• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Precision medicine in gastric cancer

    2019-10-23 05:37:58PatriziaBonelliAntonellaBorrelliFrancaMariaTuccilloLucreziaSilvestroRaffaelePalaiaFrancoMariaBuonaguro

    Patrizia Bonelli,Antonella Borrelli,Franca Maria Tuccillo,Lucrezia Silvestro,Raffaele Palaia,Franco Maria Buonaguro

    Patrizia Bonelli,Antonella Borrelli,Franca Maria Tuccillo,Franco Maria Buonaguro,Molecular Biology and Viral Oncology,Istituto Nazionale Tumori - IRCCS - Fondazione G Pascale,Napoli 80131,Italy

    Lucrezia Silvestro,Abdominal Medical Oncology,Istituto Nazionale Tumori - IRCCS -Fondazione G Pascale,Napoli 80131,Italy

    Raffaele Palaia,Gastro-pancreatic Surgery Division,Istituto Nazionale Tumori - IRCCS -Fondazione G Pascale,Napoli 80131,Italy

    Abstract

    Key words: Gastric cancer; Molecular characterization; Biomarkers; Precision medicine;Targeted therapy

    INTRODUCTION

    Gastric cancer (GC) is a complex disease whose onset is linked to a series of genetic and environmental factors such as smoking and a high salt diet.Helicobacter pylori(H.pylori) is considered one of the most significant risk factors of GC.It is present in more than 70% of non-cardia GC cases and 90% of chronic gastritis cases[1],and its presence increases the risk of cancer (as compared to uninfected individuals)[2,3].Recent research has shown that there is a correlation between the risk of GC and the characteristics of specific strains ofH.pylori[4].Moreover,H.pyloriinfection has been demonstrated to be essential for promoting chronic inflammation of the gastric epithelium and histological changes that sequentially lead to GC[5].In this process,genetic and epigenetic alterations occur such as hypermethylation of DNA or mutations in genes including APC,WNT signaling pathway regulator (APC),tumor protein p53 (TP53),and KRAS proto-oncogene,GTPase (KRAS)[6].

    Regarding treatment options,surgical resection with adjuvant or neoadjuvant radiotherapy and chemotherapy with cisplatin,5-fluorouracil (5-FU),taxane,or irinotecan are the most effective treatments for GC.However,despite the increasing knowledge and progress in drug development,this disease has a very poor prognosis due to late diagnosis and extreme intra- and inter-tumor heterogeneity.The heterogeneity makes the choice of therapy difficult,emphasizing the need for both new indicators for patient classification and novel therapies capable of addressing genetic,molecular,and cellular heterogeneity within tumors.This review highlights the progress achieved in the molecular characterization of GC and how it has impacted diagnosis,prognosis,and therapy in clinical practice.

    EPIDEMIOLOGY OF GC

    GC is the fifth most malignant tumor in worldwide and the third leading cause of cancer-related deaths[7].Unfortunately,the disease becomes symptomatic in the advanced stage; thus,the 5-year survival rate is only high (90%) in Japan where diagnosis and early tumor resection are done[8].In European countries,however,the survival rate is low,varying between 10% and 30%[9].The incidence of GC has geographical variation,with more than 50% of new cases occurring in developing countries.The areas most at risk are represented by China and Japan,Eastern Europe,Central,and South America,while the areas with lowest risk are South Asia,North America,New Zealand,Australia,and North and East Africa[10].In recent decades,a decrease in the incidence rate has been observed,especially in young patients with non-cardia,sporadic,and intestinal GC[11,12].The decreased incidence of GC can be attributed to the better preservation of foods,higher hygienic standards,higher intake of fruits and vegetables,and the eradication ofH.pylori[13].Figure1 summarizes the epidemiology of GC.

    PATHOLOGICAL CLASSIFICATION OF GC

    According to World Health Organization (commonly known as WHO) guidelines,GC can be classified as adenocarcinoma,ring-cell carcinoma,and undifferentiated carcinoma[14].The Lauren's classification,which is widely used,classifies GC into intestinal,diffuse,and mixed/unclassified types based on macroscopic and microscopic differences[15].It has been hypothesized that intestinal GC is associated with chronic atrophic gastritis and intestinal metaplasia,whereas the diffuse type originates from normal gastric mucosa.In European countries,the intestinal type is currently the most common GC[16-20].It tends to occur more often in the distal part of the stomach,in high-risk areas and is often preceded by long-standing precancerous lesions[17].On the other hand,the diffuse type is predominant among young patients.However,Lauren’s classification has a couple of key flaws.First,a large group of carcinomas do not fall into the two main types of carcinomas,intestinal or diffuse.This group of “unclassified” or “undetermined” gastric carcinomas include undifferentiated carcinomas and carcinomas that have dual differentiation (mixed intestinal and diffuse carcinomas).Second,there has been confusion regarding the“intestinal” term.Therefore,a change to Lauren’s classification has been proposed in which GCs are classified into four subtypes:Glandular,solid,isolated cell type,and mixed carcinoma[21].

    MOLECULAR CHARACTERIZATION OF GC

    Advances in next-generation sequencing (NGS) and microarray technologies and a better understanding of cancer biology have provided opportunities to characterize the genome of tumors including GC.The molecular profile of the GC has enabled The Cancer Genome Atlas (TCGA) and the Asian Cancer Research Group (ACRG) to classify GC into subtypes.The new molecular classification of GC is complementary to the subtyping classification based on histopathological characteristics.It is important to note that the molecular classification of GC helps to identify the molecular alterations that may be targeted by therapy.Furthermore,the molecular profiles of GCs obtained from individual patients have offered new opportunities to identify biomarkers that can be predictive of the tumor response to treatment[22-24]and to guide the selection of cytotoxic drugs and targeted therapies.TCGA and ACRG classifications of GC should facilitate the development of personalized prognosis and treatment,as well as better patient stratification for the design of clinical trials.The molecular characterization of GC from TCGA has used different platforms,including exome sequencing,DNA copy number analysis,DNA methylation,mRNA and microRNA (miRNA) expression.It divides GC into four subtypes:Epstein-Barr virus(EBV)-positive,microsatellite instable (MSI),chromosomal instability (CIN),and genomically stable (GS) (Figure2).Each of these GC subtypes is characterized by distinct features that provide prognostic information and suggest the potential benefits of targeted therapy.

    EBV-positive tumors have mainly been found in the fundus and gastric body[25,26],and represent about 9% of GC cases.High DNA hypermethylation has been demonstrated in EBV-positive tumors,particularly of the cyclin-dependent kinase inhibitor 2A (commonly known asCDKN2A) promoter[27].An estimated 80% of EBV-positive subtype tumors contain mutations in phosphatidylinositol 3-kinase CA(PIK3CA)[28]and amplification of Janus Kinase 2 (JAK2),CD274 molecule,and programmed cell death 1 ligand 2 (PDCD1LG2),which encode for respectively tyrosine kinase receptors,PD-L1 and PD-L2[29].Based on these results,JAK2 inhibitors and PD-L1/2 antagonists should be explored as treatment options for EBV-positive tumors.Promising initial results have been reported with pembrolizumab,a humanized monoclonal antibody against programmed cell death 1 (PD-1)[30,31].In addition toPIK3CAmutations,EBV-positive tumors have more recurrent AT-rich interaction domain 1A (ARID1A) (55%) and BCL6 corepressor (commonly known asBCOR) (23%) mutations[29,32],whereas only rareTP53mutations have been observed.

    Figure1 Epidemiology of gastric cancer.Frequency of diagnosis,leading cause of cancer death,and risk areas worldwide of gastric cancer.

    Patients with MSI subtype generally have intestinal tumors,which are diagnosed in old age.MSI tumors (21.7% of GC cases) are characterized by genomic instability due to methylation of DNA mismatch repair genes including MutL homolog 1 (MHL1)and to a high incidence of mutations inPIK3CA[33],Erb-B2 receptor tyrosine kinase 3(ERBB3)[34],ring finger protein 43 (RNF43)[35],phosphatase and tensin homolog(PTEN)[36],TP53[37],KRAS[38],andARID1A[32]genes.Increased expression of components of the mitotic pathway such as the E2F transcription factor (E2F),aurora kinase A (AURKA),polo-like kinase 1 (PLK1),and forkhead box M1 (FOXM1) has been described in MSI tumors[29].

    GS tumors (19.7%) are mainly diffuse and are diagnosed in younger patients[39].GS tumors,which lack chromosomal alteration or MSI,exhibit the high expression of molecules involved in cell adhesion and pathways related to angiogenesis.They also have low mutation rates andARID1A,ras homolog family member A (RHOA),and cadherin 1 (CDH1) are the most frequently mutated genes[40].Previous studies have shown the loss ofCDH1,which encodes the E-cadherin cell adhesion molecule,in hereditary diffuse GC[41].TCGA data have also revealed the fusion of claudin 18-Rho GTPase activating protein 6 (CLDN18-ARHGAP6) or claudin 18-Rho GTPase activating protein 26 (CLDN18-ARHGAP26) and recurrent mutations inRHOA.CLDN18 and ARHGAP6 are respectively involved in the intercellular structure of the tight junction and the activation of Rho signaling (a signaling pathway in which intracellular and extracellular stimuli activate GTPase Rho),whereas RHOA modulates programmed cell death and contractility and motility of actomyosindependent cells[42-44].Therefore,alterations in RHOA or CLDN18-ARHGAP6 could contribute to the lack of cell cohesion,dispersed growth,and programmed cell death resistance.

    CIN tumors represent almost half of GC cases (49.8%),are mainly intestinal,and are most frequent in the cardia-gastro-esophageal junction.Chromosomal deletions affectingCDH1,catenin alpha 1 (CTNNA1) and RB transcriptional corepressor 1 (RB1)and mutations inTP53(71%) are frequent in these tumors.CIN tumors present with amplification of genes encoding tyrosine kinase receptors such as epidermal growth factor receptor (EGFR),ERBB2,ERBB3,fibroblast growth factor receptor 2 (FGFR2),and MET proto-oncogene,receptor tyrosine kinase (MET); some transcription factors including the MYC proto-oncogene,basic helix-loop-helix transcription factor (MYC)and GATA binding protein 4 (GATA4); cell cycle regulators such as cyclin-dependent kinase 6 (CDK6),cyclin E1 (CCNE1),and cyclin D1 (CCND1) and other genes such asPDCD1LG2andPIK3CA[29].Alterations of these genes have been observed in advanced/metastatic GC[24].By contrast,the ACRG analyzed samples from 300 Korean patients,classifying GC based on particular genetic signatures such as the activation status ofTP53and the MSI condition[45].Four molecular subtypes have been identified:MSI,microsatellite stable (MSS) with activeTP53(MSS/TP53+),MSS with inactiveTP53(MSS/TP53-),and MSS with epithelial-mesenchymal transition (EMT)signature (MSS/EMT) (Figure3).

    Figure2 The Cancer Genome Atlas gastric tumor classification.TCGA study divides GC into four molecular subtypes:CIN (chromosomal instability); EBV (Epstein-Barr virus); GS (genomically stable); and MSI (microsatellite instable).GC:Gastric cancer; TCGA:The Cancer Genome Atlas.

    These subtypes are associated with survival and recurrence.The MSI subtype has a better prognosis and a lower tendency to relapse.The MSS/TP53+ and MSS/TP53-subtypes have an intermediate prognosis,whereas the MSS/EMT subtype is associated with a high rate of recurrence and a lower survival rate.Moreover,MSI tumors are diagnosed at an early stage (I/II),and about 60% are intestinal and show a high frequency of mutations ofPIK3CA,KRAS,ARID1A,and ALK receptor tyrosine kinase (ALK) genes; they also show loss ofMLH1.Tumors of the MSS/TP53+ subtype include many EBV-positive cases compared to the other subtypes,and have a high prevalence of mutations in theAPC,KRAS,PIK3CA,ARID1A,and SMAD family member 4 (SMAD4) genes[46]compared to the MSS/TP53- subtype.They also present amplification of theCCNE1gene.The MSS/TP53- subtype is mainly Lauren intestinal and hasTP53mutations,with a low frequency of mutations affecting the other genes.This subtype also has amplification ofEGFR,MYC,ERBB2,andCCNE1genes.The MSS/EMT subtype predominantly consists of Lauren diffuse tumors,and tend to be diagnosed at a younger age.This subtype has low cell adhesion due to loss ofCDH1and has the least number of mutations.ARID1Ais among the most frequently mutated gene.The ACRG classification is also applicable to other large independent cohorts[45].The differences between the two classifications (TGCA and ACRG) reflect the different approaches and platforms used,and the ethnicity of the samples.In the ACRG cohort,GCs of the diffuse type are more represented.However,both identified the MSI subtype with hypermethylation ofMHL1,high mutation frequency and a better prognosis.The EBV and MSS/TP53 + subtypes are similar in that many cases belonging to the MSS/TP53+ subtype is EBV+ and present mutations inPIK3CAandARID1A.The GS and MSS/EMT subtypes,which include younger patients,are mostly diffuse and show low intercellular adhesion.The CIN and MSS/TP53-subtypes present with mutations inTP53and amplification of members of theEGFRfamily,and are mostly intestinal.

    APPLICATION OF THE GC MOLECULAR PROFILE IN CLINICAL PRACTICE:PRECISION MEDICINE

    Due to new technologies,such as NGS and microarray,recent discoveries have made possible to integrate diagnostic and therapeutic method,based on genotype and phenotype,and to apply them to individual patients with GC in the age of precision medicine.

    Figure3 Asian Cancer Research Group gastric tumor classification.Gastric cancer was classified into foursubtypes:MSI (microsatellite instable); MSS (stable microsatellite); MSS/TP53+ (MSS with active TP53); MSS/TP53-(MSS with inactive TP53); MSS/EMT (MSS with epithelial-mesenchymal transition).ACRG:Asian Cancer Research Group.

    Biomarkers for diagnosis and prediction

    Tumor markers are used to determine the clinical stage,assess the treatment response,and predict the risk of recurrence after treatment.Currently,markers such as αfetoprotein (AFP),carcinoembryonic antigen (CEA),carbohydrate antigen 125 (CA-125),and carbohydrate antigen 19-9 (CA19-9) are frequently used in clinical practice.CEA is a risk factor for liver metastases[47],and increased CEA levels have been observed in all advanced GCs.The sensitivity and specificity of CEA for predicting GC recurrence is < 60% and < 80%,respectively[48].CA19-9 is a marker commonly used in GC,although it is also present in other neoplastic pathologies.In combination with other tumor markers,CA19-9 can provide more information to predict GC recurrence[49].Other markers such as AFP and CA-125 are widely used in the diagnosis of GC.AFP is an indicator of a high stage and presence of hepatic metastases[50],and CA-125 is associated with peritoneal diffusion[47].

    Among the new biomarkers,human epidermal growth factor receptor 2 (encoded byERBB2commonly referred to asHER2) represents the first biomarker available in clinical practice for patients with GC.HER2 belongs to the EGFR family and has tyrosine kinase activity[51].An estimated 6%-23% of GCs have overexpression and/or amplification ofHER2[52,53],and it is mainly found in intestinal tumors[54,55].HER2 is used in clinical practice for targeted therapy.EGFR or ERBB1 is expressed in about 30% of GCs[56].The overexpression of EGFR in the pathogenesis of GC is associated with a poorly differentiated histology,vascular invasion,and shorter survival[57].Tyrosine kinase inhibitors,particularly gefitinib and erlotinib,have shown efficacy inEGFR-amplified tumors.Mutations ofEGFRconfer resistance to these drugs[58,59].In addition to anti-HER2 monoclonal antibodies,anti-EGFR therapy also includes gefitinib and erlotinib,tyrosine kinase inhibitors,as well as monoclonal antibodies such as cetuximab and panitumumab.

    Other markers have attracted substantial attention as useful therapeutic candidates for targeted anti-cancer agents.For example,a high frequency (30%) of FGFR2 overexpression has been observed in GC.The amplification ofFGFR2is related to poor overall survival (OS)[60].Furthermore,a study found that FGFR2 could be a biomarker for predicting the long-term failure of adjuvant chemotherapy for advanced GC[61].Thus,FGFR2 may be a candidate for targeted anticancer agents.E-cadherin,a molecule involved in calcium-mediated cell adhesion,is a tumor suppressor whose deactivation is correlated with invasion and metastasis[62].The deactivation ofCDH1may occur due to mutations,hypermethylation,loss of heterozygosity,andH.pyloriinfection[62].Patients withCDH1changes have generally worse survival than negative patients.It could be a useful marker for the diagnosis of preoperative biopsies[63].Genetic deregulation of the PI3K/AKT/mTOR pathway has been frequently identified in GC[64,65],and mechanistic target of rapamycin kinase(mTOR) is activated in 60% of GCs[66].

    Mutations ofPI3KCA,which encodes the p110α catalytic isoform of PI3K,have been identified in up to 25% of patients with GC[67].These mutations are involved in resistance to antitumor drugs and the acquisition of a metastatic phenotype;moreover,they are found mainly in the EBV-positive subtype of GC[68].It has been reported that the amplification and/or overexpression ofMETis involved in carcinogenesis,the efficacy of therapy,and the outcome of GC[69].MET expression is associated with invasion and overall poor survival[70].Vascular endothelial growth factor (VEGF) encodes for a growth factor that promotes the formation of new blood vessels.VEGF and vascular endothelial growth factor receptor (VEGFR) are upregulated in about 40% of GC cases[71],and their inhibition results in decreased cell proliferation and invasion.VEGF andsVEGFR2 are also used in clinical practice in targeted therapy[72,73].TP53is a tumor suppressor whose incidence of mutation in GC is about 3%-65%[74].In the EBV-positive subtype,the incidence ofTP53mutation is lower[28]; moreover,an increased incidence has been observed in the intestinal type[75].In many human tumors,TP53mutations are associated with a poor prognosis[76].For GC,there is no well-established clinical significance between theTP53status and the outcome of patients.Recent studies,however,have integrated the mutational status ofTP53and other genetic alterations to define subpopulations of GCs in order to define the clinical relevance[77].TP53mutations appear to be a cofactor that supports the expression of genes involved in various signaling pathways; and whose aberrant activation leads to high proliferation,increased metastatic potential,and resistance to treatment.AURKAand MDM2 proto-oncogene (MDM2) encode negative regulators ofTP53.AURKAis amplified and overexpressed in GC[78].By regulating the ubiquitination of TP53 through MDM2,AURKA promotes tumor growth and cell survival[79].

    DNA damage is repaired by a series of mechanisms,including basic excision repair,mismatch repair,nucleotide excision repair,single-strand annealing,homologous recombination,and non-homologous end joining.The poly (ADP-ribose)polymerases,known as PARPs,are proteins involved in the basic excision repair pathway and catalyze the transfer of ADP-ribose to target proteins[80,81].PARP1 and PARP2 are the best known of these proteins.Numerous studies have highlighted an upregulation of PARPs in different tumors,including GC[82,83].A high expression of PARP1 in GC is associated with tumor invasion and a poor prognosis[84].

    Proteins in the matrix metalloproteinase (MMP) family are involved in breakdown of the extracellular matrix in normal physiologic processes and can promote cancer cell invasion and metastasis by degrading the extracellular matrix.Increased matrix metallopeptidase 15 (MMP15) expression is associated with poor prognosis in GC[85].In addition,overexpression of matrix metallopeptidase 9 (MMP9)is a poor prognostic factor in patients with GC[86].

    Fibrinogen C domain containing 1 (FIBCD1) is an acetyl group-binding receptor,which shows high affinity and calcium-dependent binding to acetylated structures such as chitin,some N-acetylated carbohydrates,and amino acids but not to their non-acetylated counterparts.The expression ofFIBCD1is significantly increased in GC tissues compared with normal tissues,and its overexpression is related to a poor prognosis[87].FIBCD1 may be a novel prognostic marker in gastric GC; however,the mechanisms underlying its function require further studies.

    PD-1 and PD-2 are the immune checkpoint receptors expressed on T and B lymphocytes,natural killer T cells,and monocytes[88].After binding with PD-L1 and PD-L2 on activated T cells,they downregulate the activity of cytotoxic T cells and thus induce immunotolerance to the tumor.In 15%-70% of patients with GC,PD-L1 expression has been observed and this expression correlates with poor outcome[89].Upregulation ofPD-L1/PD-L2expression in the EBV-positive subtype has been observed[29].

    Circulating tumor cells (CTCs),single or in clusters,originate from primary tumor or metastases[90].Clinically,they are related to the progression and metastatic processes,and therefore can be used as surveillance markers.CTCs can identify early stages of metastasis and thus identify patients who may benefit from treatment after primary tumor surgery[90,91].The presence of CTCs,which have the characteristics of stem cell-like or EMT cells,allows evaluation of the tumor stage and the prediction of recurrence.Circulating cell-free DNA is more sensitive than CTCs,originates from normal and cancerous cells,and is present in the blood[92].Circulating tumor DNA(ctDNA) originates from the primary tumor or metastases and can be used for the specificity of the diagnosis,even if the sensitivity is lower than the common markers used[93].The ctDNA shows the presence of EBV DNA,and is useful for identifying EBV-positive subtypes[94].The response to therapy can also be assessed with ctDNA.

    MiRNAs are small,non-coding RNAs that,by regulating gene expression,play a role in the processes of proliferation,differentiation,and cell invasion[95].They can increase the expression of oncogenes or reduce the expression of oncosuppressor genes[96].Numerous miRNAs have been identified and play a role in GC[97,98].Circulating cell-free miRNAs can be used as non-invasive biomarkers for the diagnosis and relapse of GC[99-101].Approximately 135 long non-coding RNAs(lncRNAs),non-transcribed RNA sequences longer than 200 nucleotides,are dysregulated and strongly correlated with tumorigenesis,metastasis,and prognosis of GC[102-103].Some lncRNAs are overexpressed in GC compared to healthy control tissue and may be prognostic markers[104,105].However,further studies are needed to determine their possible clinical use.

    Biomarkers for targeted therapy

    Surgery is the elective treatment for many stages of GC.In a patient with GC at stage 0,I,II,or III,surgery (often together with other treatments) is currently the only treatment.Depending on the type and stage of GC,it is possible with surgery to remove all or part of the stomach including the nearby lymph nodes (the principles).Even when the tumor is too widespread to be removed entirely,patients can be helped by surgery because it can help prevent bleeding from the tumor or remove stomach obstruction due to tumor growth.This is termed palliative surgery because it allows the reduction or prevention of symptoms,but is not indicated for the treatment of GC[106].

    Minimally invasive surgery,including laparoscopic gastrectomy and robotic gastrectomy,is receiving much attention in GC management[107,108].The laparoscopic gastrectomy has the advantage of leading to a faster recovery with shorter hospital stays compared to the traditional surgery[109].However,it has the disadvantage of limited movements.The robotic gastrectomy has overcome these limitations and its use is spreading rapidly[110-112].Some studies have been carried out in order to compare both the advantages and disadvantages of two technologies[113-115].The disadvantages of robotic gastrectomy concern its cost,duration of the procedure,and training needs[116].Unfortunately,the lack of controlled and randomized studies has precluded the ability to establish a clear indication of robotic gastrectomy in the treatment of GC[116].

    Surgical resection with pre- and post-operative chemotherapy and/or radiotherapy is the primary curative treatment of early-stage GC with a 5-year survival of about 30%[117-119].Systemic chemotherapy is used to treat patients with localized and advanced GC.Palliative systemic therapy and chemo/radiotherapy are standard treatment options for patients with unresectable or metastatic advanced GC.Neoadjuvant chemotherapy with surgery is associated with the improved survival of patients with metastatic disease[120].Perioperative chemotherapy with docetaxel,oxaliplatin,fluorouracil,and leucovorin (FLOT) significantly improves progressionfree survival (referred to herein as PFS) and OS among patients with resectable GC compared with epirubicin,cisplatin,and fluorouracil or capecitabine (ECF/ECX)[121].A Bayesian network meta-analysis obtained an estimate of the efficacy of perioperative FLOT and neoadjuvant treatments for resectable GC.Compared with surgery alone,perioperative cisplatin with fluorouracil (CF),perioperative ECF/ECX,and perioperative FLOT significantly improved survival.The most effective neoadjuvant treatment for the disease is likely to be perioperative FLOT[122].Targeted therapy,a new therapeutic strategy,may improve the survival of patients with advanced GC.Clinical trials with targeted therapies have been performed in patients with GC.Table1 shows some clinical trials,completed or ongoing,classified by specific molecular target.

    EGFR signaling pathway

    The EGFR signaling pathway is activated in the GC[56,123].Overexpression of EGFR has been associated with reduced OS[56,71].This behavior may depend on the observation that EGFR targeting molecules may be potential agents for target therapy.Trastuzumab is the first molecular targeted agent approved as standard therapy for GC.It is a monoclonal antibody against HER2,which binds to the extracellular domain of the receptor.A phase III clinical trial (ToGA) (NCT01041404) enrolled 594 patients with GC who had high HER2 expression.These patients were randomized to chemotherapy alone or combined with trastuzumab.Treatment with trastuzumab led to an increase in OS of 2.7 mo and the PFS was heightened compared to that of patients treated with chemotherapy alone[124].The benefits observed in patients treated with the combination of trastuzumab and chemotherapy were even more evident in patients who expressed high levels of HER2 compared to those with low HER2 expression.The 2015 National Comprehensive Cancer Network guidelines recommended the first-line treatment of trastuzumab combined with chemotherapy in patients overexpressing HER2.To date,trastuzumab is the only targeted therapy allowed for the treatment of advanced GC[124].A clinical trial (NCT01736410),which evaluated the efficacy of trastuzumab with tegafur,gimeracil,oteracil (TS-1) and cisplatin as first-line treatment for advanced HER2-positive GC,has been completed.The combination of trastuzumab with TS-1 and cisplatin demonstrated good activity,was well tolerated,and is a first-line treatment that can be used for advanced HER2-positive GC[125].In the GATSBY multicenter phase II/III study (NCT01641939),the efficacy of trastuzumab emtansine was evaluated in patients with advanced HER2-positive GC who had already received previous treatment.The results obtained werenot encouraging since treatment with trastuzumab emtansine did not yield increases in OS compared to standard treatment with a taxane (docetaxel,paclitaxel)[126].

    Table1 Clinical trials classified on molecular targets

    PI3KCA Alpelisib +AUY922 NCT01613950 Multicenter,open-label Second/third Ib Advanced/m etastatic gastric cancer,PIK3CA mutations and/or HER2 amplification Completed [145]AKT Ipatasertib ±5FU/oxaliplat in/leucovorin NCT01896531 Randomized,double Second II Advanced/m etastatic gastric cancer Active [146]HGF/MET HGF Rilotumumab vs rilotumumab±epirubicin/cis platin/capecit abine NCT00719550 Multicenter,randomized First Ib/II Locally advanced/me tastatic gastric cancer Completed [149]HGF Rilotumumab±epirubicin/cis platin/capecit abine RILOMET-1(NCT0169707 2)Multicenter,randomized,triple First III Locally advanced/me tastatic gastric cancer,MET-positive Terminated [150]HGF Rilotumumab±/cisplatin/ca pecitabine RILOMET-2(NCT0213734 3)Multicenter,randomized,triple First III Advanced gastric cancer Terminated [151]MET Onartuzumab± 5-FU/leucovori n/oxaliplatin NCT01662869 Multicenter,randomized,double First III Metastatic gastric cancer,HER2 negative,MET-positive Completed [152]VEGF/VEG FR VEGFR2 Ramucirumab+ BSC vs placebo +BSC REGARD(NCT0091738 4)Randomized,quadruple First III Metastatic/lo cally recurrent gastric cancer Completed [72]VEGFR2 Ramucirumab± paclitaxel RAINBOW(NCT0117066 3)Multicenter,randomized,double Second III Metastatic,refractory gastric cancer Completed [73]VEGFR2 Apatinib vs placebo NCT01512745 Randomized,quadruple Third III Advanced/m etastatic refractory gastric cancer Completed [156]TP53 TP53 Polymorphis ms of xenobiotic metabolism,DNA repair,and TP53 genes NCT01470404 Gastric cancer treated with adjuvant chemotherap y Completed [161]TP53 APR-246 + 5-FU/cisplatin NCT02999893 Open-label Second I/II Advanced/m etastatic platinum resistant gastroesopha geal cancer,TP53 mutated Recruiting [167]TP53 AZD1775(WEE inhibitor) +paclitaxel NCT02448329 Single center Second II Advanced gastric cancer,TP53 mutated Recruiting [169]TP53 HDM201(inhibitor TP53/MDM2 interaction)NCT02143635 Multicenter,nonrandomized,open-label Second I Advanced/m etastatic gastric cancer,TP53 wildtype Active [170]PARP PARP Olaparib +paclitaxel vs paclitaxel Study 39(NCT0106351 7)Multicenter,randomized,double Second II Metastatic/re current gastric cancer,low ATM expression Active [174]PARP Olaparib +paclitaxel vs placebo +paclitaxel GOLD(NCT0192453 3)Multicenter,randomized,double Second III Advanced gastric cancer Active [175]

    EGFR:Epidermal growth factor receptor; mTOR:Mechanistic target of rapamycin kinase; HGF:Hepatocyte growth factor; VEGF:Vascular endothelial growth factor; TP53:Tumor protein p53; PARP:Poly (ADP-ribose) polymerase; PD-1:Programmed cell death 1.

    Other agents that target HER2,such as pertuzumab and lapatinib,have been used in clinical trials in patients with advanced GC and HER2 overexpression.One study(JACOB,NCT01774786) was performed with pertuzumab,trastuzumab,and chemotherapy in patients with untreated HER2-positive metastatic GC.This trial was the first to investigate the dual antibody blockade of HER2.Unfortunately,no significant improvement in OS was observed in the dual blockade group[127].The clinical trial (TRIO-013/LOGiC,NCT00680901) performed with lapatinib in combination with oxaliplatin and capecitabine did not produce significant results in terms of OS[128].A parallel study of biomarkers was conducted using immunohistochemistry and NGS.The most common alteration found in HER2-positive patients was amplification ofCCNE1,which correlated with a lack of response to therapy.Patients with high levels ofERBB2amplification were more responsive to therapy.The analysis of cell-free DNA showed that the amplification ofERBB2,detectable in the plasma of patients,was a predictive response.During disease progression,genetic changes were detected such as amplification ofMYC,EGFR,FGFR2,andMET[129].A phase I clinical trial (NCT02795988) evaluated the safety,tolerability,and immunogenicity of IMU-131,a peptide composed of three epitopes selected from the protein structure of HER2.In the phase II portion of the same trial,IMU-131 was used in combination with chemotherapy in patients overexpressing HER2.The study is ongoing,as only phase I has been completed,and no conclusions have been drawn[130].Pyrotinib is an irreversible inhibitor of both HER2 and EGFR.The phase I studies (NCT02500199,NCT02378389) with pyrotinib and pyrotinib plus docetaxel in patients with HER2-positive GC are recruiting[131,132].

    Studies have also been performed to identify markers to be used in monitoring the efficacy of trastuzumab alone or in combination with chemotherapy.Resistance has occurred in patients treated with trastuzumab.One of the main mechanisms that lead to this resistance are mutations inPI3KCAandPTEN[64,65,67].The combination of trastuzumab with PI3K inhibitors may bring substantial benefits to patients with HER2-positive GC.One of the markers of resistance to trastuzumab isCCNE1,whose amplification is negatively correlated with the response to therapy directed against HER2[133].Other monoclonal antibodies used to target EGFR include cetuximab and panitumumab.The results showed that anti-EGFR antibodies did not provide further benefits for patients with advanced GC receiving chemotherapy as first-line treatment(EXPAND) (NCT00678535)[134].Panitumumab was used as first-line treatment in a clinical phase I/II trial (NCT01716546) in association with 5-FU,cisplatin,and docetaxel for locally advanced or metastatic GC.However,this study did not reach its primary endpoint because in an intermediate analysis,the number of responses obtained was lower than the prefixed limit[135].Nimotuzumab is the first EGFR humanized monoclonal antibody that binds with high specificity to the extracellular region of EGFR.Two clinical trials have been concluded.The phase III study(NCT01813253) was performed to evaluate the OS in advanced GC patients with EGFR overexpression who were treated with nimotuzumab in combination with irinotecan and compared to a group of patients who received only irinotecan.This study,completed in 2018,has not yet had its results reported[136].The second study(NCT02370849) evaluated the efficacy of cisplatin and S-1 with and without nimotuzumab in patients with advanced GC who were not previously treated[137].The combination of nimotuzumab and S-1-cisplatin provided no additional benefit compared to chemotherapy alone in the first-line treatment of unresectable or metastatic GC[138]

    mTOR/PI3K/AKT signaling pathway

    Everolimus (RAD001) is an mTOR inhibitor with antitumor activity.In a phase I clinical trial,RAD001 was used in combination with capecitabine in patients with refractory GC; the clinical benefits were modest[139].In phase I clinical trials(NCT01049620) and (NCT01042782),RAD001 was used in combination with capecitabine and oxaliplatin and with mitomycin C,respectively,in patients with advanced GC; the results of these trials are unknown[140,141].In a multicenter phase II study (NCT00519324),RAD001 was used in patients with metastatic GC with previous chemotherapy failure; particularly,10.1 mo was the median OS for which the monotherapy with everolimus,in patients in which the previous chemotherapy had failed,showed a satisfying disease control rate[142].Another clinical trial(NCT00729482) evaluated the efficacy of RAD001 as a monotherapy in patients with advanced GC in whom standard first-line treatment had failed.In addition to the efficacy of RAD001,the expression of markers was evaluated in order to identify biomarkers of response to therapy.Tumors that did not have mTOR pathway activation did not benefit from treatment with RAD001[143].The median OS was lower than that reported in the study conducted by Doiet al[142].The results of this study showed that the efficacy of RAD001 was unsatisfactory compared to conventional treatment for advanced GC[143].In the phase III GRANITE-1 study (NCT00879333),the median OS in patients treated with RAD001vsplacebo was 5.4vs4.3 mo.Compared to best supportive therapy (referred to as BSC in Table1),RAD001 did not significantly improve OS in patients with advanced GC who were previously administered one or two lines of systemic chemotherapy[144].A clinical trial(NCT01613950) was performed to investigate the efficacy of the combination of alpelisib (BYL719),a potent and selective inhibitor of mutatedPI3KCAand AUY922,an inhibitor of heat shock protein 90 (HSP90),in patients with advanced GC withPIK3CAmutations and/or amplification ofHER2,respectively.The results are not yet known[145].Ipatasertib (GDC-0068),an inhibitor of serine/threonine kinase (AKT),has been used in combination with 5-FU,folinic acid,and oxaliplatin (mFOLFOX6) in advanced or metastatic GC in a multicenter placebo-controlled clinical trial(NCT01896531).The trial is ongoing[146].

    Hepatocyte growth factor/MET signaling pathway

    High MET expression has been observed in intestinal GC rather than in the diffuse type and in advanced stage disease[147].MET positivity is a prognostic factor for OS in GC[148].Patients with GC and MET expression can benefit from anti-MET drugs.Rilotumumab is a hepatocyte growth factor (HGF) monoclonal antibody that blocks binding between HGF and its receptor MET.The efficacy of first-line rilotumumab in patients with GC in combination with ECX was demonstrated in a phase Ib/II clinical study (NCT00719550).The group of patients who received ECX plus rilotumumab showed a better prognosis than placebo[149].The RILOMET-1 clinical trial(NCT01697072) evaluated the efficacy of rilotumumab in combination with epirubicin,cisplatin,and capecitabine.Regarding OS,the addition of rilotumumab to chemotherapy did not bring about benefits compared to chemotherapy alone in MET-positive patients[150],unlike the phase II study in which OS was 10.6vs5.7 mo in MET-positive patients who received rilotumumab compared to the placebo group[149].The multicenter phase III clinical trial,RILOMET-2 (NCT02137343),in which patients with advanced GC were treated first-line with rilotumumab plus cisplatin and capecitabine,was closed for a review of the safety of the study[151].The randomized,multicenter study (NCT01662869) evaluated the efficacy of onartuzumab (monoclonal anti-MET antibody) in combination with mFOLFOX6 in patients with metastatic HER2-negative and MET-positive GC.Onartuzumab did not yield satisfactory results in combination with FOLFOX[152].

    VEGF/VEGFR signaling pathway

    Antibodies against VEGF and VEGFR have shown anti-tumor effects in combination with chemotherapy as first and second-line treatments for GC.Bevacizumab,a humanized monoclonal antibody against VEGF,inhibits the VEGF/VEGFR signaling pathway[153].A phase II study (NCT00447330) was performed in patients with metastatic GC in combination with capecitabine and oxaliplatin; an OS of 7.2 and 10.8 mo was demonstrated in the two groups of patients treated with chemotherapy alone and with the combination with bevacizumab,respectively[154].Ramucirumab is a humanized monoclonal antibody specific for VEGFR2.By blocking downstream VEGFR2 signaling,ramucirumab provides antitumor effects both as a single agent(REGARD trial,NCT00917384)[72]and in combination with paclitaxel (RAINBOW trial,NCT01170663)[73]in patients with metastatic refractory GC.The median OS was significantly longer in the group of patients treated with ramucirumab plus paclitaxel(9.6 mo) compared to those treated with paclitaxel plus placebo (7.4 mo).Thus,ramucirumab may be a new second-line treatment for patients with metastatic GC.The addition of ramucirumab to FOLFOX (leucovorin,5-FU,oxaliplatin) did not improve OS in patients with advanced GC[155].In a phase III study (NCT01512745),apatinibvsplacebo was used in patients with advanced/metastatic GC who failed two lines of chemotherapy.The median OS was 6.5vs4.7 mo[156].Other studies with apatinib have been started but have not yet been completed regarding the use of apatinib alone as first-line maintenance treatment in patients with advanced GC(NCT03255811)[157]and as maintenance treatment with capecitabine (NCT03598348)after first-line chemotherapy[158].The clinical trial (NCT03104283) assessed the efficacy and safety of apatinib as monotherapy in elderly advanced GC patients,and determined the relationship between VEGFR2 expression and efficacy of apatinib treatment[159].In a retrospective study,the efficacy of the association of apatinib with docetaxelvsapatinib as monotherapy as a second- or third-line treatment in advanced GC was evaluated.The median OS was 3.3vs6.0 mo in patients with apatinib monotherapy and those with apatinib and docetaxel combination,respectively.Patients with advanced GC benefited more with the combination of apatinib and docetaxel than with apatinib monotherapy[160].

    TP53 signaling pathway

    A pharmacogenomic study (NCT01470404) was performed to evaluate the effects of germline polymorphisms in xenobiotic metabolism genes on the toxicity profile,and the role of germline polymorphisms of genes involved in DNA repair and theTP53tumor suppressor to predict disease recurrence and survival in GC patients treated with adjuvant chemotherapy[161].TP53mutations represent a very attractive target for cancer therapy.One of the objectives being pursued is to identify molecules that can restore the function of wild-type TP53.Among these,APR-246 was identified[162],and has already been tested in mouse models of cancer[163-165]and in phase I/II clinical trials on hematological and prostate malignancies[166].A phase I/II study(NCT02999893) was prepared for the treatment of gastroesophageal tumors with mutatedTP53[167].BecauseTP53mutations are still somewhat difficult to address adequately,identifying TP53-dependent targets may provide new opportunities for alternative targeted therapies.For example,targeting WEE1 G2 checkpoint kinase(WEE1),a protein kinase that plays a role in the G2-M cell cycle checkpoint,prevents cells from entering mitosis in response to DNA damage[168].AZD1775,an inhibitor of WEE1,was used in the clinical trial (NCT02448329) as second-line therapy in combination with paclitaxel in GC harboringTP53mutations[169].Overexpression of AURKA improves the stabilization of MDM2 and promotes the degradation of TP53,inhibiting its proapoptotic function in response to chemotherapy[79].This result justifies the use of AURKA inhibitors in the treatment of GC.The TP53/MDM2 interaction inhibitor (HDM201) was used in the clinical trial (NCT02143635) in patients with advanced GC characterized by wild-type TP53; this study is ongoing[170].No clinical trial has been performed on the use of MMP inhibitors in GC.

    PARP signaling pathway

    In response to DNA damage,sensors and effectors are activated that induce cell cycle arrest,damage repair,and eventually cell apoptosis.PARP inhibitors act by preventing breakage of the single DNA strand and induce tumor cell death[171].In vitro,gastric carcinoma cell lines,particularly those in which the ATM serine/threonine kinase expression levels are low,were sensitive to the action of olaparib (PARP inhibitor)[172].In a phase II study,the efficacy of olaparib (AZD-221)plus paclitaxel was evaluatedvspaclitaxel in patients with recurrent or metastatic GC whose ATM expression levels were low or undetectable (Study 39; NCT01063517)[173].The combination of olaparib plus paclitaxel significantly improved OS compared to placebo/paclitaxel,both in the general population and in the population with low ATM levels (13.1vs8.3 mo)[174].A multicenter phase III trial has evaluated the efficacy of olaparib in combination with paclitaxelvsplacebo plus paclitaxel in patients with advanced GC who are progressing after first-line treatment (GOLD,NCT01924533).The OS did not differ between treatment groups in the overall population (median OS 8.8 mo in the olaparib groupvs6.9 mo in the placebo group or the negative ATM population (12.0 movs10.0 mo)[173].

    The GOLD study did not achieve its primary objective to show a significant improvement in OS with olaparib in the overall or ATM-negative population of patients with advanced GC.However,the study provided data on efficacy and safety related to the use of olaparib in combination with a chemotherapy drug and the study itself is foundational for other studies in this type of patients[175].The GOLD trial has been negative for its endpoints of improved OS,both in overall patient population and the ATM-negative population.The differences between the GOLD trial and Study 39 are the enriched population of ATM-negative patients in Study 39 (51%vs19%)with respect to the GOLD study.PARP inhibitors are effective in tumors with a definite molecular signature,so it may not be realistic to expect efficacy from olaparib in an unselected marker population[176].

    Furthermore,the time of exposure to olaparib was shorter in the GOLD trial than in Study 39[177].A phase I/II pilot study was prepared to analyze the efficacy of olaparib in combination with ramucirumab in patients with metastatic,recurrent or unresectable GC (NCT03008278).The study is currently recruiting[178].Another phase I clinical trial (NCT01123876) studied the combination of veliparib (PARP inhibitor)with FOLFIRI in patients with advanced solid tumors,including GC[179].The antitumor activity of veliparib in combination with FOLFIRI and the acceptable safety profile lay the foundation for further studies.

    Immune checkpoint signaling pathway

    Pembrolizumab is the first immune checkpoint inhibitor approved by the United States Food and Drug Administration (FDA) for the treatment of advanced or metastatic GC[180].In a multicenter phase II trial (KEYNOTE-059,NCT02335411),the efficacy of pembrolizumab alone was demonstrated in patients with advanced GC who had previously been treated[181].Treatment with pembrolizumab showed a higher overall response rate in PD-L1-positive patients than in PD-L1-negative patients.Furthermore,in MSI-high patients,the response was higher than that in non-MSI high patients.These results suggest that PD-L1 and MSI levels may be predictive biomarkers of pembrolizumab efficacy[182].In the trial KEYNOTE-061 (NCT02370498),which was performed in patients with advanced PD-L1-positive GC,the efficacy of second-line treatment of pembrolizumabvspaclitaxel was compared.Pembrolizumab did not significantly improve OS compared to paclitaxel but had a better safety profile than paclitaxel[183].Pembrolizumab was used as first-line monotherapy or in combination with cisplatin,5-FU,or capecitabine in patients with advanced PD-L1-positive GC (KEYNOTE-062,NCT02494583); the results of this study are not yet known[184].In the clinical trial KEYNOTE-859 (NCT03675737),the efficacy of pembrolizumab in association with chemotherapy with cisplatin and 5-FU or oxaliplatin and capecitabine,in advanced/metastatic HER2-negative GC expressing PD-L1,will be evaluated[185].Another clinical trial (NCT02954536) is evaluating the first-line efficacy of the combination of pembrolizumab and trastuzumab in combination with chemotherapy in patients with HER2-positive metastatic GC.Preliminary results have been obtained on the safety and efficacy of the treatment.Resistance phenomena have occurred because mutations ofTP53(63%) andKRAS(16%) and loss ofERBB2amplification in disease progression have been observed[186].Nivolumab is a monoclonal antibody that targets PD-1 and has received FDA approval for neoplastic pathologies.In a clinical trial (NCT02267343) performed in patients with locally advanced or metastatic GC refractory to chemotherapy,nivolumab was effective with improvement of the median OS[187].In another clinical trial (NCT02746796),the efficacy of nivolumab in combination with chemotherapy as first-line treatment was tested in patients with advanced or recurrent non-resectable GC[188].In the clinical trial CheckMate-032 (NCT01928394),performed on solid tumors including GC,the efficacy of nivolumab in combination with ipilimumab,an anticytotoxic T-lymphocyte associated protein 4 antibody (CTLA4),was evaluated.Nivolumab with ipilimumab demonstrated encouraging long-term OS in patients with GC refractory to chemotherapy[189].In the clinical trial CheckMate-649(NCT02872116),the efficacy of nivolumab as first-line treatment in combination with ipilimumabvsnivolumab plus chemotherapyvschemotherapy alone,is being evaluated in patients with advanced or metastatic GC[190].The clinical trial(NCT03777657) is evaluating the efficacy of tislelizumab,a humanized anti-PD1,in combination with oxaliplatin and capecitabine or 5-FU and cisplatin[191].

    Other targets

    Clinical trials have been performed to study the significance of CTCs in advanced/metastatic GC.Some trials (NCT03156777[192],NCT01625702)[193]have been designed to evaluate CTCs as markers of prognosis and response to chemotherapy.In a clinical trial (NCT01625702) in HER2-positive patients,an increased HER2 extracellular domain was a predictor of a better prognosis.The elevated levels of HER2 after therapy were correlated with a negative therapeutic response[194].Other trials have been designed to evaluate CTCs and cell-free DNA as clinical prognosis markers (NCT01299688)[195]and response to HER2 (NCT02610218)[196]or VEGFR(NCT02048540)[197]targeting.Only one clinical trial (NCT01848015) was designed to establish the predictive value of CTCs in the recurrence of advanced GC after radical resection[198].Some of these trials have been completed,but the results are not yet known.A study conducted in patients with HER2-positive metastatic GC revealed that the ctDNA of these patients provided useful information for monitoring the response to trastuzumab,for the purpose of developing therapeutic strategies for HER2-positive but trastuzumab-resistant patients[199].A phase III clinical study(NCT01178944) was performed to determine if miR-215-5p levels could be predictive of the response to pralatrexate (a folate analog metabolic inhibitor) in association with oxaliplatin in patients with non-resectable GC[200].Another study (NCT03253107) was conducted to determine if miRNAs levels may be predictive biological markers for the response to chemotherapy[201].The results of these trials are not yet known.A study(NCT03057171) is ongoing on the control ofH.pylorion the expression of lncRNAs in gastrointestinal diseases including GC[202].

    CONCLUSION

    GC is the fifth most malignant tumor worldwide and the third leading cause of cancer-related deaths[7].Unfortunately,the disease becomes symptomatic in the advanced stage.GC is a complex disease whose onset is linked to a series of environmental and genetic factors[1-6].Despite the increasing knowledge and progress in drug development,due to late diagnosis and extreme intra- and inter-tumor heterogeneity,the prognosis of GC patients is poor.The heterogeneity of GC is mainly linked to genetic and epigenetic alterations,but also interactions with the microenvironment and the presence of intratumoral cellular clones.Hence,there are variations between patients and within the same tumor.The new classifications,TCGA and ACRG,based on molecular profiles and complementary to those based on pathological characteristics[15],have highlighted four GC subtypes,each characterized by specific genetic alterations[29].The molecular classification of GC has helped to identify molecular alterations that may be targeted by the therapy.Furthermore,the molecular profiles of GCs obtained from individual patients has provided new opportunities to identify biomarkers that may predict the tumor response to treatment[22-24].Unfortunately,even today,the molecular characteristics of tumors are not taken into significant consideration in the management of patients.

    H.pyloriis responsible for the onset of peptic ulcers and 80% of GC cases.Eradication of theH.pyloriinfection treats gastritis and peptic ulcers and is a mean to prevent GC.Obviously,for the treatment of the eradication of theH.pylori,guidelines have been issued by three separate authoritative groups[203-205]but none overcome the problem of resistance.Falloneet al[206]recently revised the guidelines to arrive at the best treatment options; however,GC still develops after the eradication.Many Japanese investigators have reported that the presence of severe atrophy after eradication represents a risk factor for the development of GC[207].Hence,there is a need for specific endoscopic surveillance programs for this type of patients.

    Endoscopy plays an important role in the diagnosis of GC[208].More than 90% of GC cases are reportedly revealed by biopsy-associated endoscopy.The increased use of endoscopy,thanks also to the revolutionary developments that have occurred recently and that have produced new,more sophisticated systems,has allowed highlighting of the “early” GC[209,210].Ultrasonographic endoscopy is useful for TNM staging of GC patients,having a high diagnostic value.This technique allows the patient to be managed for the most appropriate treatment,limiting the occurrence of unnecessary exploratory surgical procedures[211].Endoscopy can also be curative for early GC or used as palliative care for more advanced cases.In early GC,the endoscopic mucosal resection provides similar effects as traditional surgical resection[212,213].

    Surgical resection with adjuvant or neoadjuvant radiotherapy and chemotherapy with cisplatin,5-FU,taxane,or irinotecan,remains the most effective treatment for advanced GC.The recent MRC MAGIC/UK study (ISRCTN93793971) showed that perioperative ECF/ECX chemotherapy led to an improvement in OS and PFS in patients with resectable GC[214].Perioperative chemotherapy is the standard of care in most of Europe for localized GC with accepted ECF or ECX regimens[215].However,objective response rates to chemotherapy range from 20% to 40%,indicating variable clinical responses that are mostly likely caused by the biologic heterogeneity of the tumor.As with chemotherapy,therapeutic regimens based on targeted therapy have recently been introduced,which makes use of small molecules or monoclonal antibodies that can act on specific molecules capable of modifying molecular pathways involved in proliferation,differentiation,and cell invasion.

    Based on phase III clinical trials in patients with advanced/metastatic GC,trastuzumab (anti-HER2) and ramucirumab (anti-VEGFR2) have been approved as first- and second-line therapies in these patients[72-74,124].However,the survival of patients receiving these therapies is not very high,and with the exception of HER2,there are no markers that can be used to evaluate the response to therapy.Data from preclinical studies have shown a relationship between HER2 overexpression and activation of angiogenesis in breast cancer cells[216].A retrospective study showed significant efficacy of the combination of a biological therapy with ramucirumab with a chemotherapeutic (paclitaxel) in patients in whom trastuzumab therapy had failed[217].This study has demonstrated the crosstalk between HER2 signaling and angiogenesis in GC,which can explain tumor survival.Therefore,trastuzumab resistance could be overcome by inhibiting the angiogenic pathway.An analysis of subgroups extrapolated from the RAINBOW study showed that patients who had already been treated with trastuzumab benefited from treatment with ramucirumab in combination with paclitaxel[218].New studies will be needed to evaluate the efficacy of sequential blockades of both pathways to improve the survival of patients with GC.

    Other monoclonal antibodies,such as cetuximab and panitumumab (anti-EGFR),have also been tested in advanced/metastatic GC but the results on survival rates have not been encouraging[134-135].Unacceptable results were obtained with RAD001,an mTOR inhibitor.The efficacy of RAD001 is unsatisfactory compared to conventional treatment for advanced GCs[139,143].Anti-MET monoclonal antibodies,such as rilotumumab and onartuzumab,in combination with chemotherapy,did not bring benefits compared to chemotherapy alone[149-152].A study was prepared to more effectively target MET with a mixture of two humanized monoclonal antibodies that target two non-overlapping MET epitopes.The results represent efficacy data demonstrated on preclinical models and are part of a clinical trial (NCT02648724)[219]carried out on patients with NSLC and MET amplification[220].The advantage of antibody mixtures is their ability to orchestrate the internalization of the receptor and its degradation more effectively than a single monoclonal antibody,as previously shown for the EGFR family[221].

    PARP inhibitors are very effective in the treatment of ovarian and breast tumors in which DNA repair systems are altered and BRCA1/2 mutations are present,which makes them more sensitive to these inhibitors[222].New biomarkers are being explored,which go beyond BRCA1/2 mutations and DNA repair mechanism deficits to stratify sensitive patients,new combinations of PARP inhibitors,and/or combinations with checkpoint inhibitors to determine who will be eligible for this treatment for other solid tumors,including GC[223].It has been hypothesized that the inhibition of PARP may trigger mechanisms based on the recognition of new tumor cell antigens by the immune system,making the PARP inhibitors potential partners for combination with immune checkpoint inhibitors.

    Recently,patients with GC have also been studied from an immunotherapy viewpoint.Pembrolizumab and nivolumab received FDA approval for GC[180].Anti-PD1 antibodies have been used in phase II and phase III clinical trials and appear to be promising,especially in patients overexpressing PD-L1.Further clinical trials are underway to evaluate the efficacy of these antibodies in association with chemotherapy.At the same time,other pathways such as the TP53 signaling pathway,are being studied to identify inhibitory molecules[162-166].Strategic opportunities can also be provided by studying the potential of biomarkers such as CTCs,ctDNA,miRNAs,and lncRNAs to predict response to therapy and resistance phenomena.

    There is no doubt that targeted therapies allow patients to live longer,whether they are administered alone or in combination with chemotherapy.Today the probability of observing patients who survive several years after the diagnosis of cancer is much higher,thanks to the targeted therapies.The targeted therapies must be provided to groups of patients who can benefit from them,screened on the molecular profiles to which the therapy is effective.Molecular profiling regarding the overexpression and/or mutation of the targets must be carried out on tissue biopsies,both in resectable and unresectable patients,to establish the correct targeted therapy to be used alone or associated with chemotherapy.It is necessary to continue to study the heterogeneity of GC.The fact that GC has genetic variations between different patients and/or in the same patient during its progression and/or during or after therapy (conventional or targeted) should drive investigations into the molecular characteristics present in tumor tissue,and the use of circulating biomarkers to predict and monitor disease progression and response to therapy.Furthermore,the association of several markers should be considered in order to appropriately classify the tumor and to establish therapeutic strategies that increase survival rates.

    国产男人的电影天堂91| 亚洲一区二区三区欧美精品| 街头女战士在线观看网站| 亚洲精品乱码久久久久久按摩| 18+在线观看网站| 国产欧美日韩精品一区二区| 色5月婷婷丁香| 国产成人精品福利久久| 中文欧美无线码| 日韩精品有码人妻一区| 一级毛片 在线播放| 2018国产大陆天天弄谢| 免费观看的影片在线观看| 久久精品国产亚洲网站| 新久久久久国产一级毛片| 男人狂女人下面高潮的视频| 日日啪夜夜爽| 亚洲人成网站高清观看| 亚洲电影在线观看av| 国产亚洲5aaaaa淫片| 99久久中文字幕三级久久日本| 久久综合国产亚洲精品| 久久精品国产亚洲网站| 欧美变态另类bdsm刘玥| 免费观看av网站的网址| 国产精品秋霞免费鲁丝片| 精品久久国产蜜桃| 成年人午夜在线观看视频| 亚洲av不卡在线观看| 国产淫语在线视频| 日本黄大片高清| 日韩不卡一区二区三区视频在线| 久久97久久精品| 建设人人有责人人尽责人人享有的 | 18禁在线播放成人免费| 日韩一区二区三区影片| 中国美白少妇内射xxxbb| 国产成人精品久久久久久| 国内揄拍国产精品人妻在线| av卡一久久| 一级av片app| 国产免费一区二区三区四区乱码| 久热久热在线精品观看| 国产淫语在线视频| 亚州av有码| 欧美三级亚洲精品| 内地一区二区视频在线| 美女内射精品一级片tv| 2018国产大陆天天弄谢| 人妻夜夜爽99麻豆av| 久久av网站| 日本黄色片子视频| 欧美成人一区二区免费高清观看| av国产免费在线观看| 亚洲精品一二三| 精品人妻一区二区三区麻豆| 亚洲第一区二区三区不卡| 国产一区二区三区av在线| 精品一区二区三卡| 久久国产精品大桥未久av | 人妻 亚洲 视频| 国产精品精品国产色婷婷| 国产黄片美女视频| 日本黄色片子视频| 国产综合精华液| 亚洲美女视频黄频| 夫妻性生交免费视频一级片| 久久久久久久久久久丰满| 91精品伊人久久大香线蕉| 国产一区二区在线观看日韩| 精品人妻偷拍中文字幕| 国产亚洲最大av| 水蜜桃什么品种好| 欧美日本视频| 国产精品无大码| 18禁在线播放成人免费| 亚洲精品国产av蜜桃| h视频一区二区三区| 国产亚洲一区二区精品| 高清av免费在线| 欧美日韩在线观看h| 美女视频免费永久观看网站| 嫩草影院新地址| 日韩人妻高清精品专区| 亚洲av中文字字幕乱码综合| 狠狠精品人妻久久久久久综合| av不卡在线播放| 美女国产视频在线观看| 欧美xxⅹ黑人| 国产精品不卡视频一区二区| 久热久热在线精品观看| 青春草国产在线视频| 午夜福利影视在线免费观看| 91久久精品国产一区二区三区| 亚洲aⅴ乱码一区二区在线播放| 欧美成人精品欧美一级黄| 久久精品国产亚洲av涩爱| 国产亚洲5aaaaa淫片| 丰满迷人的少妇在线观看| 国产精品久久久久久精品电影小说 | 国产成人freesex在线| 深夜a级毛片| 精品少妇久久久久久888优播| 久久久久性生活片| 国产成人精品福利久久| 久久久久视频综合| 秋霞在线观看毛片| 大香蕉久久网| 国产精品人妻久久久影院| 99久国产av精品国产电影| 亚洲av成人精品一区久久| 永久网站在线| 91久久精品国产一区二区三区| 亚洲欧美日韩另类电影网站 | av免费在线看不卡| 日韩 亚洲 欧美在线| 亚洲av中文字字幕乱码综合| 久久精品国产自在天天线| 毛片一级片免费看久久久久| 欧美一级a爱片免费观看看| 国产永久视频网站| 国产免费视频播放在线视频| 亚洲第一av免费看| 只有这里有精品99| 午夜老司机福利剧场| 丝袜喷水一区| 久久99蜜桃精品久久| 一区二区三区四区激情视频| 精品一区二区三卡| 婷婷色综合大香蕉| 热99国产精品久久久久久7| a级一级毛片免费在线观看| 久久久午夜欧美精品| 天堂8中文在线网| 亚洲国产成人一精品久久久| 肉色欧美久久久久久久蜜桃| 一级二级三级毛片免费看| 特大巨黑吊av在线直播| 高清午夜精品一区二区三区| 深爱激情五月婷婷| 欧美xxxx性猛交bbbb| 乱系列少妇在线播放| 国产精品成人在线| 国产成人91sexporn| 中国国产av一级| 观看美女的网站| 亚洲婷婷狠狠爱综合网| 亚洲国产色片| 欧美成人午夜免费资源| 成年女人在线观看亚洲视频| 欧美人与善性xxx| 我的老师免费观看完整版| 亚洲精品日韩在线中文字幕| 色吧在线观看| 一级毛片久久久久久久久女| 日韩免费高清中文字幕av| 亚洲成人一二三区av| 亚洲国产毛片av蜜桃av| 国产在线视频一区二区| 亚洲av欧美aⅴ国产| 欧美另类一区| 久久精品国产亚洲av天美| 欧美三级亚洲精品| 日韩成人av中文字幕在线观看| 晚上一个人看的免费电影| 欧美日韩综合久久久久久| 亚洲国产欧美在线一区| 18禁动态无遮挡网站| 亚洲成人av在线免费| 中文精品一卡2卡3卡4更新| 99热全是精品| 欧美人与善性xxx| 一级毛片黄色毛片免费观看视频| 国产69精品久久久久777片| 久久久久精品性色| 嘟嘟电影网在线观看| 赤兔流量卡办理| 一区二区三区精品91| 男女边摸边吃奶| 九色成人免费人妻av| 午夜激情福利司机影院| 少妇精品久久久久久久| 伦精品一区二区三区| 国产精品一区二区性色av| 日产精品乱码卡一卡2卡三| 菩萨蛮人人尽说江南好唐韦庄| 多毛熟女@视频| 成人无遮挡网站| 麻豆乱淫一区二区| 精品亚洲成国产av| 成人综合一区亚洲| 国产精品一区二区在线观看99| 亚洲av日韩在线播放| 亚洲国产av新网站| 欧美少妇被猛烈插入视频| 大片免费播放器 马上看| 国产亚洲一区二区精品| 熟女人妻精品中文字幕| 色视频www国产| 亚洲av中文字字幕乱码综合| 91久久精品电影网| 国精品久久久久久国模美| 黄色欧美视频在线观看| 欧美bdsm另类| 亚洲欧美日韩另类电影网站 | 成人国产麻豆网| a 毛片基地| 亚洲国产日韩一区二区| 日韩av免费高清视频| 极品教师在线视频| 亚洲精品乱码久久久久久按摩| 国产免费视频播放在线视频| 亚洲无线观看免费| 精品午夜福利在线看| 成人二区视频| 日韩av在线免费看完整版不卡| 国产成人a∨麻豆精品| 国产伦精品一区二区三区四那| 又大又黄又爽视频免费| 99热这里只有是精品在线观看| 大陆偷拍与自拍| 亚洲精品国产成人久久av| 伊人久久国产一区二区| 免费观看a级毛片全部| 色婷婷久久久亚洲欧美| 波野结衣二区三区在线| 国产亚洲最大av| 伊人久久国产一区二区| 国产一区二区在线观看日韩| 久久99热6这里只有精品| 精品国产露脸久久av麻豆| 偷拍熟女少妇极品色| 丝袜喷水一区| 久久99热这里只有精品18| 一级黄片播放器| 熟女电影av网| 亚洲aⅴ乱码一区二区在线播放| 午夜免费观看性视频| 少妇人妻 视频| 狂野欧美白嫩少妇大欣赏| 久久女婷五月综合色啪小说| 久久99热这里只频精品6学生| 国产免费又黄又爽又色| 菩萨蛮人人尽说江南好唐韦庄| 韩国av在线不卡| 国产精品久久久久久久电影| 卡戴珊不雅视频在线播放| av专区在线播放| 亚洲成人中文字幕在线播放| 99久国产av精品国产电影| 欧美变态另类bdsm刘玥| 亚洲美女黄色视频免费看| 午夜福利高清视频| 乱码一卡2卡4卡精品| 国产有黄有色有爽视频| 国产有黄有色有爽视频| 黄片wwwwww| 久久人人爽av亚洲精品天堂 | 欧美三级亚洲精品| 日韩三级伦理在线观看| 国产精品国产三级国产专区5o| 97在线人人人人妻| 亚洲av国产av综合av卡| 亚洲欧美日韩卡通动漫| 日本欧美视频一区| 国产一区二区三区综合在线观看 | 亚洲国产最新在线播放| 久久国产精品男人的天堂亚洲 | 久久久久久伊人网av| 亚洲欧美日韩卡通动漫| 如何舔出高潮| 色网站视频免费| 高清日韩中文字幕在线| 精品久久久久久久末码| 国产伦精品一区二区三区四那| 国产午夜精品久久久久久一区二区三区| 亚洲av电影在线观看一区二区三区| 18禁动态无遮挡网站| 伦精品一区二区三区| 国产伦精品一区二区三区视频9| 国产精品女同一区二区软件| 国产精品嫩草影院av在线观看| 精品人妻一区二区三区麻豆| 午夜福利高清视频| 偷拍熟女少妇极品色| 又爽又黄a免费视频| av在线观看视频网站免费| 王馨瑶露胸无遮挡在线观看| 久热这里只有精品99| 亚洲伊人久久精品综合| 少妇 在线观看| 欧美激情极品国产一区二区三区 | 99热6这里只有精品| 国产白丝娇喘喷水9色精品| 七月丁香在线播放| 韩国高清视频一区二区三区| 国产av精品麻豆| 成人影院久久| 新久久久久国产一级毛片| 精品人妻偷拍中文字幕| 卡戴珊不雅视频在线播放| 久久精品熟女亚洲av麻豆精品| 高清午夜精品一区二区三区| 亚洲国产精品一区三区| 纯流量卡能插随身wifi吗| 亚洲国产日韩一区二区| www.色视频.com| 亚洲欧美清纯卡通| 国产一区有黄有色的免费视频| 亚洲av欧美aⅴ国产| 欧美性感艳星| 美女视频免费永久观看网站| 国产欧美亚洲国产| 久久精品国产自在天天线| 日日摸夜夜添夜夜爱| 熟妇人妻不卡中文字幕| 国产熟女欧美一区二区| 欧美少妇被猛烈插入视频| 99热这里只有是精品在线观看| 人人妻人人澡人人爽人人夜夜| 大码成人一级视频| 人妻系列 视频| 尾随美女入室| 99久久中文字幕三级久久日本| 黄色视频在线播放观看不卡| 国产成人午夜福利电影在线观看| 观看av在线不卡| 天天躁夜夜躁狠狠久久av| 中文字幕亚洲精品专区| 国产精品麻豆人妻色哟哟久久| 亚洲中文av在线| 26uuu在线亚洲综合色| 亚洲成人手机| 成人一区二区视频在线观看| 男人舔奶头视频| 一区二区三区四区激情视频| 新久久久久国产一级毛片| av网站免费在线观看视频| 日本av手机在线免费观看| 亚洲精品一区蜜桃| 我的老师免费观看完整版| 久久综合国产亚洲精品| 国产91av在线免费观看| 天堂中文最新版在线下载| 91在线精品国自产拍蜜月| av视频免费观看在线观看| 国产精品人妻久久久影院| 纯流量卡能插随身wifi吗| 91久久精品电影网| 91精品伊人久久大香线蕉| 91精品一卡2卡3卡4卡| 91久久精品国产一区二区三区| 99久久精品一区二区三区| 亚洲内射少妇av| 精品视频人人做人人爽| 夫妻午夜视频| 国产午夜精品一二区理论片| 在线观看国产h片| 成人午夜精彩视频在线观看| 久久久久人妻精品一区果冻| 国产精品99久久久久久久久| 亚洲欧美日韩卡通动漫| 波野结衣二区三区在线| 最近手机中文字幕大全| 国产精品一区二区性色av| 日韩亚洲欧美综合| 国内少妇人妻偷人精品xxx网站| 国产人妻一区二区三区在| 高清黄色对白视频在线免费看 | 久久久久国产精品人妻一区二区| 亚洲av中文av极速乱| 久久精品夜色国产| 只有这里有精品99| 极品教师在线视频| 亚洲欧洲国产日韩| 九九爱精品视频在线观看| 国产一区二区在线观看日韩| 直男gayav资源| 男人舔奶头视频| 精品久久久久久久末码| 国产熟女欧美一区二区| 午夜老司机福利剧场| 人妻一区二区av| 有码 亚洲区| 精品一品国产午夜福利视频| 成人影院久久| 不卡视频在线观看欧美| 六月丁香七月| 夜夜看夜夜爽夜夜摸| 亚洲精品国产av成人精品| 天堂中文最新版在线下载| 老司机影院成人| 我的老师免费观看完整版| 在线免费十八禁| 亚洲欧美一区二区三区黑人 | 成人漫画全彩无遮挡| 欧美极品一区二区三区四区| 国产av码专区亚洲av| 亚洲精品国产色婷婷电影| 国产欧美日韩一区二区三区在线 | 丝瓜视频免费看黄片| 国产亚洲5aaaaa淫片| 久久久久网色| 在线播放无遮挡| 99re6热这里在线精品视频| 免费大片黄手机在线观看| 久久久久久久久大av| 日本一二三区视频观看| 男人添女人高潮全过程视频| 亚洲成人中文字幕在线播放| 国产淫片久久久久久久久| 国产在线免费精品| av又黄又爽大尺度在线免费看| 欧美成人精品欧美一级黄| 边亲边吃奶的免费视频| 王馨瑶露胸无遮挡在线观看| 日日摸夜夜添夜夜添av毛片| 久久久成人免费电影| 久久久久性生活片| 国产免费福利视频在线观看| 卡戴珊不雅视频在线播放| 国产精品不卡视频一区二区| 各种免费的搞黄视频| 中文字幕免费在线视频6| 婷婷色麻豆天堂久久| 亚洲国产最新在线播放| 99国产精品免费福利视频| 欧美另类一区| tube8黄色片| 国内揄拍国产精品人妻在线| 国产乱来视频区| 久久热精品热| 国产精品伦人一区二区| 精品一区二区免费观看| 中文字幕久久专区| 搡老乐熟女国产| 内射极品少妇av片p| 久久国产亚洲av麻豆专区| 精品国产一区二区三区久久久樱花 | 最近中文字幕高清免费大全6| 看十八女毛片水多多多| 一本一本综合久久| 午夜日本视频在线| 久热久热在线精品观看| 成人国产av品久久久| 久久精品久久久久久久性| 国产一区二区在线观看日韩| 亚洲国产毛片av蜜桃av| 噜噜噜噜噜久久久久久91| 日本黄色日本黄色录像| 插阴视频在线观看视频| 国产乱人视频| 亚洲av不卡在线观看| 国产精品一及| 国产精品麻豆人妻色哟哟久久| 免费av中文字幕在线| 人妻一区二区av| 91精品伊人久久大香线蕉| 精品熟女少妇av免费看| 丝袜喷水一区| 爱豆传媒免费全集在线观看| 中文字幕久久专区| 欧美日韩视频高清一区二区三区二| 看十八女毛片水多多多| 色婷婷久久久亚洲欧美| 久久99蜜桃精品久久| 亚洲美女搞黄在线观看| 九色成人免费人妻av| 色5月婷婷丁香| 毛片一级片免费看久久久久| 永久免费av网站大全| 欧美丝袜亚洲另类| 亚洲伊人久久精品综合| 久久久精品免费免费高清| 18禁在线播放成人免费| 成人亚洲欧美一区二区av| 国产人妻一区二区三区在| 欧美日韩在线观看h| 97在线人人人人妻| 欧美另类一区| 伦理电影大哥的女人| 日本一二三区视频观看| 国产精品国产三级专区第一集| 26uuu在线亚洲综合色| 乱码一卡2卡4卡精品| 丰满乱子伦码专区| 国产欧美亚洲国产| 色婷婷久久久亚洲欧美| 亚洲欧美日韩无卡精品| 又黄又爽又刺激的免费视频.| 国产精品爽爽va在线观看网站| 少妇高潮的动态图| 热99国产精品久久久久久7| 国产亚洲5aaaaa淫片| 老熟女久久久| a级毛片免费高清观看在线播放| 一个人看视频在线观看www免费| 91精品国产国语对白视频| 国产免费一级a男人的天堂| 超碰97精品在线观看| 日日撸夜夜添| 国产精品国产av在线观看| 在线观看免费高清a一片| 国产精品一区二区性色av| 亚洲成人一二三区av| 最近最新中文字幕免费大全7| 欧美变态另类bdsm刘玥| 国产精品久久久久久av不卡| 午夜福利高清视频| 蜜桃久久精品国产亚洲av| 美女国产视频在线观看| 国产精品国产av在线观看| 卡戴珊不雅视频在线播放| 永久免费av网站大全| 国产精品久久久久久久久免| 国产一区亚洲一区在线观看| 亚洲在久久综合| 久久国内精品自在自线图片| 国产亚洲5aaaaa淫片| 又爽又黄a免费视频| 午夜激情久久久久久久| 亚洲国产日韩一区二区| 国产片特级美女逼逼视频| 精华霜和精华液先用哪个| 久久国产精品男人的天堂亚洲 | 夜夜看夜夜爽夜夜摸| 99热这里只有是精品在线观看| 国产成人91sexporn| 蜜桃在线观看..| 亚洲,一卡二卡三卡| 国产女主播在线喷水免费视频网站| 国产精品久久久久久久久免| 一级片'在线观看视频| 国产在线视频一区二区| 麻豆成人午夜福利视频| 男女下面进入的视频免费午夜| av专区在线播放| 午夜福利视频精品| 亚洲精品亚洲一区二区| 又爽又黄a免费视频| 舔av片在线| 欧美区成人在线视频| 久久精品国产亚洲网站| av免费在线看不卡| 欧美人与善性xxx| 国产精品熟女久久久久浪| 日本午夜av视频| 国产免费又黄又爽又色| 女人十人毛片免费观看3o分钟| 纵有疾风起免费观看全集完整版| 99热这里只有精品一区| 久久久精品94久久精品| 国产精品一区二区在线观看99| 久久人人爽人人片av| 我的女老师完整版在线观看| 欧美人与善性xxx| 五月天丁香电影| 26uuu在线亚洲综合色| 80岁老熟妇乱子伦牲交| 成人无遮挡网站| 街头女战士在线观看网站| 免费少妇av软件| 啦啦啦视频在线资源免费观看| 日韩一本色道免费dvd| 亚洲人成网站在线播| 国产视频首页在线观看| 精品国产露脸久久av麻豆| 亚洲成人一二三区av| 国产亚洲欧美精品永久| 看十八女毛片水多多多| 免费在线观看成人毛片| 亚洲自偷自拍三级| 色综合色国产| 麻豆乱淫一区二区| 精品午夜福利在线看| 国产毛片在线视频| 91精品国产国语对白视频| 美女脱内裤让男人舔精品视频| 亚洲色图综合在线观看| 五月天丁香电影| 日韩欧美 国产精品| 久久精品夜色国产| 黄片无遮挡物在线观看| 久热久热在线精品观看| 搡女人真爽免费视频火全软件| 国产亚洲av片在线观看秒播厂| 2018国产大陆天天弄谢| 日日摸夜夜添夜夜添av毛片| 啦啦啦视频在线资源免费观看| 高清午夜精品一区二区三区| 水蜜桃什么品种好| 亚洲欧美精品专区久久| 老熟女久久久| 大片电影免费在线观看免费| 日韩成人伦理影院| 啦啦啦视频在线资源免费观看| 一级毛片黄色毛片免费观看视频| 水蜜桃什么品种好| av免费观看日本| videos熟女内射| 亚洲国产欧美人成| 国产一区二区三区综合在线观看 | 在线免费十八禁| 中文欧美无线码| 久久久久久人妻| 亚洲国产欧美在线一区| 亚洲欧美成人精品一区二区| 女人十人毛片免费观看3o分钟| 免费观看在线日韩| 亚洲欧美日韩另类电影网站 | 亚洲精品国产av蜜桃| 国产精品一区二区在线不卡| av在线蜜桃| 亚洲国产精品国产精品| 天堂8中文在线网|