韓晟 陳衍
TRPM7離子通道在口腔鱗癌細(xì)胞增殖和遷移中的作用
韓晟 陳衍
目的探討TRPM7離子通道在口腔鱗癌細(xì)胞增殖和遷移中的作用。方法Western blotting,RT-PCR和間接免疫熒光法檢測(cè)口腔鱗癌細(xì)胞OC2中TRPM7的表達(dá)和細(xì)胞內(nèi)定位。MTT法和Transwell試驗(yàn)分別檢測(cè)抑制TRPM7通道(2-APB、siRNA TRPM7)對(duì)OC2細(xì)胞增殖和遷移的影響。Western blotting檢測(cè)2-APB或siRNA TRPM7阻斷PI3K/AKT通路對(duì)OC2細(xì)胞中TRPM7的表達(dá)影響。采用膜片鉗技術(shù)初步探索干預(yù)TRPM7通道對(duì)OC2細(xì)胞陽(yáng)離子通透的影響。結(jié)果OC2細(xì)胞中TRPM7過(guò)表達(dá),主要表達(dá)在細(xì)胞質(zhì)中。阻斷TRPM7通道后,OC2細(xì)胞增殖和遷移能力受抑制,且呈濃度依賴性和時(shí)間依賴性。阻斷TRPM7通道后,抑制OC2細(xì)胞TRPM7可下調(diào)磷酸化AKT以及磷酸化ERK的表達(dá),而對(duì)組成性AKT以及ERK的表達(dá)無(wú)明顯影響。膜片鉗技術(shù)顯示在TRPM7過(guò)表達(dá)的OC2細(xì)胞中TRPM7樣電流激活,2-APB 阻斷TRPM7通道后電流明顯減弱,而采用TRPM7通道活化劑Bradykinin后,電流明顯增強(qiáng)。結(jié)論TRPM7在口腔鱗癌細(xì)胞OC2中過(guò)表達(dá),可能通過(guò)影響PI3K/AKT和MAPK-ERK信號(hào)轉(zhuǎn)導(dǎo)途徑以及陽(yáng)離子內(nèi)流發(fā)揮對(duì)細(xì)胞增殖、遷移的調(diào)節(jié)作用。
口腔鱗癌; 瞬時(shí)受體電位家族成員7; 細(xì)胞增殖; 遷移
口腔鱗癌是頭頸部最常見(jiàn)的惡性腫瘤,晚期口腔鱗癌患者預(yù)后差,傳統(tǒng)治療方法有效率低,因此需要尋找新的治療靶點(diǎn)。近年來(lái)研究發(fā)現(xiàn)某些離子通道與腫瘤的發(fā)生發(fā)展密切相關(guān)。很多離子通道在非興奮性組織起源的腫瘤中高表達(dá),而在相同起源的正常組織中低表達(dá)或不表達(dá)。因此離子通道成為腫瘤研究領(lǐng)域新的熱點(diǎn)。瞬時(shí)受體電位家族成員TRPM7(transient receptor potential melastatin 7)組成性表達(dá)于興奮性和非興奮性細(xì)胞的質(zhì)膜上,參與細(xì)胞內(nèi)離子平衡的調(diào)節(jié)、神經(jīng)遞質(zhì)的釋放、細(xì)胞的黏附和遷移等重要生理過(guò)程[1]。TRPM7在多種腫瘤中過(guò)表達(dá),與腫瘤細(xì)胞的生長(zhǎng)、增殖和轉(zhuǎn)移密切相關(guān)[2-5]。目前有關(guān)口腔癌相關(guān)離子通道的研究還很缺乏,本研究初步探討TRPM7離子通道在口腔鱗癌細(xì)胞增殖和遷移中的作用,不僅有助于進(jìn)一步闡明口腔癌發(fā)生、發(fā)展及轉(zhuǎn)移的機(jī)制,并為基于該離子通道的口腔鱗癌靶向治療提供理論依據(jù)。
1.1 細(xì)胞培養(yǎng)
人類口腔鱗癌細(xì)胞株OC2由第四軍醫(yī)大學(xué)口腔醫(yī)學(xué)院實(shí)驗(yàn)中心保留。培養(yǎng)基采用以1∶1混合的Dulbecco培養(yǎng)基和Ham F12培養(yǎng)基,輔以10 胎牛血清和抗生素(50 U/L青霉素和50 U/L鏈霉素)溶液,以及2.5 mmol/L谷氨酰胺和400 g/L氫化可的松溶液。37 ℃含5% CO2的孵箱培養(yǎng)。免疫組化實(shí)驗(yàn)時(shí),將細(xì)胞接種于預(yù)先用多聚左旋鳥(niǎo)氨酸包被的蓋玻片上,生長(zhǎng)3 d后用于實(shí)驗(yàn)。
1.2 間接免疫熒光法觀察口腔鱗癌細(xì)胞OC2中TRPM7的表達(dá)和細(xì)胞內(nèi)定位
將OC2細(xì)胞按2×105/孔的密度分別接種于預(yù)先放置蓋玻片的6 孔板中,次日PBS洗滌后用4%多聚甲醛室溫固定15 min,PBS漂洗后將細(xì)胞置于乙醇和乙酸(2∶1)混合液中快速冷卻5 min(-20 ℃),室溫下加入預(yù)先用PBS稀釋的3 TritonX-100,作用20 min后加入由2%正常山羊血清和1%牛血清白蛋白組成的封閉緩沖液,孵育30 min后直接加入1∶100稀釋比例的TRPM7一抗(Abgent), 4 ℃孵育過(guò)夜。 二抗選用稀釋比例1∶750的Cy3偶聯(lián)的羊抗兔抗體(Jackson Immunoresearch,Inc,USA),室溫下孵育2 h, 避光。 DAPI封片,激光共聚焦顯微鏡下觀察。
1.3 Western blotting法
提取細(xì)胞的總蛋白,配置電泳樣品。配置分離膠(TRPM7 75 g/L,其余120 g/L)和50 g/L的濃縮膠。等量樣品經(jīng)SDS-PAGE電泳后,穩(wěn)流將蛋白電轉(zhuǎn)至甲醇預(yù)處理的PVDF膜上(TRPM7電轉(zhuǎn)5 h,其余電轉(zhuǎn)2 h)。轉(zhuǎn)膜、封閉后按流程分別加入一抗和二抗。暗室中發(fā)光、顯影和定影。抗AKT抗體、抗phospho-AKT(Ser473)、抗ERK 抗體、抗phospho-ERK(1/2)(Thr202/Tyr204)抗體購(gòu)自Cell Signaling Technology,Inc,USA。
1.4 RT-PCR法檢測(cè)OC2中TRPM7的表達(dá)
Trizol法提取OC2細(xì)胞的RNA,RT-PCR擴(kuò)增TRPM7 mRMA,引物設(shè)計(jì):正義5'-AAACATGTTGGTGATGCCCTC-3'。 反義5'-CACACACAACAACTGGAA CGG-3'(NCBI accession no. NC_005102)。 RT-PCR擴(kuò)增條件: 94 ℃ 30 s,57 ℃ 15 s,72 ℃ 30 s,共30 個(gè)循環(huán)(Clontech, CA)。
1.5 TRPM7-siRNA轉(zhuǎn)染
特異性TRPM7-siRNA合成序列設(shè)計(jì)為:5'-AAGCAGAGTGACCTGGTAGA T-3'。將細(xì)胞數(shù)預(yù)先稀釋至10 個(gè)細(xì)胞/ml;轉(zhuǎn)染試劑si PORTNeoFX(Ambion)和TRPM7 siRNA分別用Opti-MEMI低血清培養(yǎng)基(Invitrogen)按照1∶20進(jìn)行稀釋,再將稀釋后的NeoFX和TRPM7-siRNA混合,形成轉(zhuǎn)染復(fù)合物;將含有轉(zhuǎn)染復(fù)合物的培養(yǎng)基先等分至24 孔板內(nèi),再將稀釋后的細(xì)胞加入24 孔板,使每孔分別含有30 nmol/L終濃度的TRPM7-siRNA和10 個(gè)細(xì)胞。經(jīng)過(guò)TRPM7-siRNA轉(zhuǎn)染的細(xì)胞72 h后用于細(xì)胞毒評(píng)估。
1.6 MTT細(xì)胞增殖試驗(yàn)
將細(xì)胞按3×103/孔的密度分別接種于96 孔板,給予上述細(xì)胞TRPM7通道抑制劑2-APB(0、10、100 mol/L)作用48 h后終止反應(yīng),MTT法測(cè)定細(xì)胞存活率和增殖曲線。均設(shè)復(fù)孔和對(duì)照孔。
1.7 Transwell 細(xì)胞遷移實(shí)驗(yàn)
將Transwell小室(Corning)放入24 孔細(xì)胞培養(yǎng)板中,常規(guī)培養(yǎng)腫瘤細(xì)胞,胰酶消化后接種小室, 24 h后冰甲醛固定濾膜后進(jìn)行HE染色。用棉簽輕輕拭去濾膜上表面未穿透的細(xì)胞,各選擇5個(gè)高倍鏡(×200)視野,分別計(jì)數(shù)濾膜下面和24孔板中的細(xì)胞數(shù)(穿膜細(xì)胞數(shù)),以穿膜細(xì)胞數(shù)表示其運(yùn)動(dòng)能力。
1.8 膜片鉗技術(shù)記錄細(xì)胞TRPM7通道全細(xì)胞電流
采用膜片鉗技術(shù)記錄細(xì)胞TRPM7通道全細(xì)胞電流,分析濃度梯度與電流關(guān)系。在無(wú)鈣離子的細(xì)胞外液(添加細(xì)胞外鈣離子螯合劑)中,膜片鉗技術(shù)記錄細(xì)胞TRPM7通道電流在TRPM7通道抑制劑(2-APB 100 mol/L)和激活劑(Bradykinin 10 μmol/L)作用下的電流變化情況。配置細(xì)胞外溶液:K-gluconate 5 mmol/L,Na-gluconate 140 mmol/L,CaCl21 mmol/L, MgCl21 mmol/L, glucose 5 mmol/L及HEPES 10 mmol/L, pH 7.4。細(xì)胞內(nèi)溶液:Na-gluconate 140 mmol/L,NaCl 4 mmol/L,EGTA 1 mmol/L,EDTA 1 mmol/L及HEPES 10 mmol/L,pH 7.2。葡萄糖酸鹽適量減少以維持合適的滲透壓。室溫下膜片鉗記錄全細(xì)胞離子,采用Axopatch 200B放大器(Axon Instruments, Foster City)及pClamp 9.2軟件分析。
2.1 口腔鱗癌細(xì)胞OC2中TRPM7的表達(dá)
采用間接免疫熒光法檢測(cè)OC2細(xì)胞中TRPM7的細(xì)胞內(nèi)定位,結(jié)果示TRPM7主要定位于胞質(zhì)中(圖 1)。采用Western blotting 和RT-PCR法檢測(cè)OC2中TRPM7的表達(dá)情況,結(jié)果顯示在OC2細(xì)胞中TRPM7過(guò)表達(dá),siRNA TRPM7后TRPM7 的蛋白(圖 2A)和mRNA(圖 2B)表達(dá)水平均下調(diào)。
A: 熒光染色; B: DAPI染色
圖 1 OC2細(xì)胞中TRPM7蛋白的表達(dá)
(× 40)
A: Indirect immunofluorescence assay; B: DAPI staining
Fig 1 TRPM expression in OC2 cells
(× 40)
A: TRPM7蛋白表達(dá); B: TRPM7 mRNA表達(dá)
2.2 抑制TRPM7對(duì)口腔鱗癌細(xì)胞系OC2生物學(xué)性狀的影響
為探討阻斷TRPM7通道對(duì)OC2細(xì)胞增殖的影響,給予TRPM7抑制劑2-APB(0、 10、 100 μmol/L)、siRNA TRPM7后,觀察對(duì)細(xì)胞生物學(xué)性狀的影響。MTT結(jié)果顯示,2-APB 阻斷TRPM7通道后OC2細(xì)胞生長(zhǎng)和增殖受抑,且呈濃度依賴性和時(shí)間依賴性(圖 3),100 μmol/L作用48 h時(shí)其抑制能力達(dá)到78.56%。同樣,給予siRNA TRPM7后,OC2細(xì)胞生長(zhǎng)和增殖受抑,且呈時(shí)間依賴性,在作用48 h后,其細(xì)胞增殖能力下降約84.27%(圖 4)。此外,siRNA TRPM7后, OC2細(xì)胞的遷移能力受到明顯抑制,與對(duì)照組相比作用24 h其遷移能力下降71.09%(圖 5)。
圖 3 2-APB對(duì)OC2細(xì)胞增殖的影響
圖 4 siRNA TRPM7對(duì)OC2細(xì)胞增殖的影響
Fig 4 The effects of siRNA TRPM7 on the proliferation of OC2 cells
2.3 TRPM7通道可通過(guò)PI3K/AKT途徑對(duì)口腔鱗癌細(xì)胞系OC2的生長(zhǎng)進(jìn)行調(diào)控
為探討TRPM7通道對(duì)OC2細(xì)胞系PI3K/AKT和MAPK-ERK信號(hào)轉(zhuǎn)導(dǎo)通路的影響,對(duì)OC2細(xì)胞siRNA TRPM7后,采用Western blotting檢測(cè)AKT、磷酸化AKT、ERK以及磷酸化ERK的表達(dá)情況。結(jié)果顯示,抑制OC2細(xì)胞TRPM7可下調(diào)磷酸化AKT以及磷酸化ERK的表達(dá),而對(duì)組成性AKT以及ERK的表達(dá)無(wú)明顯影響(圖 6)。
2.4 TRPM7通道對(duì)口腔鱗癌細(xì)胞系OC2陽(yáng)離子通透的影響
采用膜片鉗技術(shù)探索TRPM7通道對(duì)OC2陽(yáng)離子通透的影響。給予OC2細(xì)胞TRPM7通道抑制劑2-APB(100 μmol/L)或活化劑Bradykinin(10 μmol/L),膜片鉗實(shí)驗(yàn)檢測(cè)了OC2全細(xì)胞電流,結(jié)果顯示,在TRPM7過(guò)表達(dá)的OC2細(xì)胞中TRPM7樣電流激活,采用TRPM7通道抑制劑2-APB 阻斷TRPM7通道后電流明顯減弱,而采用TRPM7通道活化劑Bradykinin后,電流明顯增強(qiáng)(圖 7)。
圖 5 siRNA TRPM7對(duì)OC2細(xì)胞遷移能力的影響
圖 6 TRPM7對(duì)OC2細(xì)胞磷酸化AKT以及磷酸化ERK表達(dá)的影響
Fig 6 The effects of TRPM7 on the expression of phosphorylated AKT and phosphorylated ERK
圖 7 TRPM7對(duì)OC2細(xì)胞陽(yáng)離子通透的影響
Fig 7 The effects of TRPM7 on the positive ion permeability of OC2 cells
TRPM7為TRPM亞家族成員,是第一個(gè)被發(fā)現(xiàn)的具有離子通道和蛋白激酶雙重結(jié)構(gòu)的“雙功能蛋白”,其對(duì)陽(yáng)離子具有通透性,調(diào)控細(xì)胞內(nèi)Mg2+和Ca2+內(nèi)穩(wěn)定[1,6]。此外,TRPM7還作為一種絲/蘇胺酸蛋白激酶可使自身或底物磷酸化,是細(xì)胞生長(zhǎng)和增殖的關(guān)鍵調(diào)控者,不僅是早期胚胎發(fā)育所必須的,還在多種腫瘤細(xì)胞中過(guò)表達(dá),參與調(diào)控腫瘤細(xì)胞的生長(zhǎng)和遷移[2-5]。TRPM7 在頭頸部腫瘤中的研究較少。TRPM7在鼻咽鱗癌中過(guò)表達(dá),是鼻咽鱗癌細(xì)胞增殖、抗凋亡所必需,并與較差的臨床預(yù)后密切相關(guān),是獨(dú)立的臨床預(yù)后因素,敲除TRPM7可以增強(qiáng)鼻咽鱗癌細(xì)胞對(duì)放療的敏感性[3,8]。我們的研究發(fā)現(xiàn),口腔鱗癌OC2細(xì)胞中TRPM7過(guò)表達(dá),特異性抑制TRPM7后OC2細(xì)胞生長(zhǎng)、增殖和遷移能力明顯受抑。因此說(shuō)明TRPM7離子通道在口腔鱗癌的發(fā)生、發(fā)展和轉(zhuǎn)移中起到重要作用,而抑制該通道可能成為口腔鱗癌新的治療途徑。
那么TRPM7到底通過(guò)什么途徑調(diào)控口腔鱗癌細(xì)胞的生長(zhǎng)、增殖和遷移能力?研究表明TRPM7可通過(guò)STAT3、AKT、JAK2/STAT3及Notch等多種信號(hào)通路調(diào)控不同腫瘤細(xì)胞的增殖和遷移[3,9-10]。本研究顯示,抑制TRPM7可下調(diào)磷酸化AKT以及磷酸化ERK的表達(dá)水平,因此推測(cè)TRPM7通道可能通過(guò)PI3K/AKT和MAPK-ERK途徑對(duì)口腔鱗癌細(xì)胞系OC2的生長(zhǎng)進(jìn)行調(diào)控,但是還需要進(jìn)一步驗(yàn)證。此外,我們還推測(cè)TRPM7通道至少通過(guò)影響陽(yáng)離子參與口腔癌的發(fā)生發(fā)展。TRPM7是調(diào)控非興奮性細(xì)胞(腫瘤細(xì)胞屬非興奮細(xì)胞)Ca2+內(nèi)流的關(guān)鍵通道[11]。TRPM7和m-鈣激活蛋白酶共存于細(xì)胞黏附復(fù)合體中,Ca2+可通過(guò)TRPM7通道激活m-鈣激活蛋白酶,使細(xì)胞黏附復(fù)合物解離從而抑制細(xì)胞黏附[12]。TRPM7 Ca2+通道參與人鼻咽癌細(xì)胞的侵襲轉(zhuǎn)移。細(xì)胞外Ca2+螯合劑、TRPM7抑制劑均可抑制鼻咽癌細(xì)胞的遷移,而運(yùn)用TRPM7 活化劑則促進(jìn)細(xì)胞增殖[13]。在頭頸部腫瘤細(xì)胞FaDu和FCC25內(nèi)檢測(cè)到Ca2+傳感電流和TRPM7 通道,這種電流至少部分通過(guò) TRPM7通道[14]。我們的膜片鉗技術(shù)檢測(cè)結(jié)果顯示在TRPM7過(guò)表達(dá)的OC2細(xì)胞中TRPM7樣電流激活,采用TRPM7通道抑制劑2-APB 阻斷TRPM7通道后電流明顯減弱,而采用TRPM7通道活化劑Bradykinin后,電流明顯增強(qiáng)。
綜上所述,TRPM7在口腔鱗癌細(xì)胞OC2中過(guò)表達(dá),抑制TRPM7離子通道可抑制腫瘤細(xì)胞增殖和遷移,可能通過(guò)影響PI3K/AKT和MAPK/ERK信號(hào)轉(zhuǎn)導(dǎo)途徑以及陽(yáng)離子內(nèi)流發(fā)揮作用,靶向TRPM7離子通道可能為口腔鱗癌新的治療途徑。
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TheroleofTRPM7ionchannelintheproliferationandmigrationoforalsquamouscancercells
HANSheng1,CHENYan2.
1. 710032Xi'an,StateKeyLaboratoryofMilitaryStomatology&NationalClinicalResearchCenterforOralDiseases,DepartmentofInformationCenter,SchoolofStomatology,TheFourthMilitaryMedicalUniversity,China; 2.DepartmentofOncology,Xi'jingHospital,TheFourthMilitaryMedicalUniversity,Xi'an
Objective: To investigate the role of the transient receptor potential melastatin subfamily member 7(TRPM7) ion channel in the proliferation and migration of oral squamous cancer cells OC2.MethodsThe expression of TRPM7 in OC2 cells was examined by western blotting, RT-PCR and indirect immunofluorescence assay. The influence of TRPM7 on cell proliferation and migration under the inhibition of TRPM7 ion channel with 2-APB or siRNA TRPM7 in OC2 cells was examined by MTT and Transwell respectively. The influence of PI3K/AKT signal pathway on the expression of TRPM7 in OC2 cells was tested by Western blotting. The change of positive ion current when the OC2 cells were treated with TRPM7 inhibitor and activator was explored with patch clamp technique.ResultsTRPM7 overexpression in OC2 cells mainly in the cytoplasm was observed, siRNA TRPM7 downregulated the expression of TRPM7. Inhibition of TRPM7(2-APB or siRNA TRPM7) inhibited the growth and proliferation of OC2 cells in a time- and dose-dependent manner. Blockage of TRPM7 ion channel inhibited the migration capacity of OC2 cells. Inhibition of TRPM7 downregulated the expression of phosphorylated AKT and phosphorylated ERK. Patch clamp assay showed the activation of TRPM7-like current in OC2 cells. 2-APB could weaken this current while Bradykinin could enhance the current.ConclusionTRPM7 may regulate the proliferation and migration of oral cancer cells by the regulation of PI3K/AKT and MAPK/ERK signal pathways and cell positive current.
Oralsquamouscellcarcinoma;TRPM7;Cellproliferation;Migration
陜西省攻關(guān)項(xiàng)目資助(編號(hào): 2013K12-03-01); 中華醫(yī)學(xué)會(huì)吳階平醫(yī)學(xué)基金(編號(hào): 320.6750.12235)
710032 西安, 軍事口腔醫(yī)學(xué)國(guó)家重點(diǎn)實(shí)驗(yàn)室, 口腔疾病國(guó)家臨床醫(yī)學(xué)研究中心, 第四軍醫(yī)大學(xué)口腔醫(yī)院信息科(韓晟); 第四軍醫(yī)大學(xué)西京醫(yī)院腫瘤科(陳衍)
陳衍 E-mail: chenyan@fmmu.edu.cn
R739.8
A
10.3969/j.issn.1001-3733.2017.04.022
(收稿: 2016-12-07 修回: 2017-01-04)