張笑添, 張曉延, 黃賽亞, 王 倩, 劉 威
(1山西醫(yī)科大學汾陽學院醫(yī)學檢驗系, 山西 汾陽 032200; 2山西醫(yī)科大學醫(yī)學影像學系, 山西 太原 030001)
miRNA-101-3p靶向調(diào)控EZH2蛋白抑制胃癌細胞增殖和遷移*
張笑添1△, 張曉延1, 黃賽亞1, 王 倩2, 劉 威1
(1山西醫(yī)科大學汾陽學院醫(yī)學檢驗系, 山西 汾陽 032200;2山西醫(yī)科大學醫(yī)學影像學系, 山西 太原 030001)
目的研究微小RNA-101-3p (miRNA-101-3p) 對人胃癌細胞增殖、凋亡和遷移的影響及其可能的調(diào)控機制。方法Real-time PCR檢測2種人胃癌細胞和1種胃黏膜細胞中miRNA-101-3p和zeste增強子同源物2 (EZH2) 的表達水平;采用脂質(zhì)體瞬時轉(zhuǎn)染技術過表達miRNA-101-3p;流式細胞術檢測miRNA-101-3p對胃癌細胞周期和凋亡的影響;Transwell實驗、CCK-8法和臺盼藍染色法檢測miRNA-101-3p對胃癌細胞遷移和增殖能力的影響;Western blot法檢測EZH2的表達。結果miRNA-101-3p在胃癌細胞的表達水平顯著低于胃黏膜細胞(P<0.05);過表達miRNA-101-3p后,流式細胞術結果顯示胃癌細胞的S期比例減少,G0/G1期比例增加,早期凋亡率增加(P<0.05);CCK-8法、臺盼藍染色法及Transwell實驗結果顯示胃癌細胞的增殖和遷移能力顯著降低(P<0.05);Western blot結果顯示胃癌細胞中EZH2蛋白的表達明顯下降(P<0.05)。結論miRNA-101-3p可能通過靶向負調(diào)控EZH2蛋白的表達抑制胃癌細胞的增殖和遷移,進而促進胃癌細胞凋亡。
胃癌; 微小RNA; 細胞增殖; 細胞遷移; 細胞凋亡; Zeste增強子同源物2
胃癌是最常見的惡性腫瘤之一,是腫瘤死亡的第2常見的原因,其生存期和預后較差[1-2]。微小RNA (microRNA, miRNA) 作為一種高度保守的小分子內(nèi)源性的非編碼RNA,可以靶向結合mRNA 3’-UTR進而調(diào)控靶基因的表達。已有研究發(fā)現(xiàn),miRNA-101-3p在結腸癌[3]、膀胱移行細胞癌[4]、肝癌[5]和乳腺癌[6]等發(fā)揮著抑癌的作用。近期研究發(fā)現(xiàn),miRNA-101-3p在胃癌中表達下降[7],但是其對胃癌細胞周期及凋亡的研究尚未見報道。
Zeste增強子同源物2(enhancer of zeste homolog 2,EZH2)是多梳家族(Polycomb group,PcG)的重要成員之一,在胚胎發(fā)育、細胞增殖和細胞周期調(diào)控中起著重要的作用。有研究發(fā)現(xiàn),EZH2與多種腫瘤的發(fā)生發(fā)展、轉(zhuǎn)移和侵襲都密切相關[8-9]?;诖耍狙芯繉⑻接慐ZH2在胃癌中與miRNA-101-3p的相關性,以及miRNA-101-3p對胃癌細胞增殖、遷移以及凋亡的影響。
miRNA反轉(zhuǎn)錄以及熒光定量試劑盒購于北京天根生化有限公司;miRNA-101-3p mimics以及miRNA陰性對照(negative control, NC)購于廣州銳博生物有限公司;Lipofectamine 2000購自Invitrogen;抗EZH2單克隆抗體購于Abcam;抗GAPDH多克隆抗體購于Bioworld;Transwell小室購自康寧公司;CCK-8以及細胞周期試劑盒購自碧云天生物有限公司;Annexin V-FITC/PI凋亡試劑盒購于聯(lián)科生物有限公司;RIPA裂解液以及BCA定量試劑盒購自武漢博士德生物有限公司。
2.1細胞培養(yǎng)和轉(zhuǎn)染 胃癌細胞MGC-803和HGC-27的培養(yǎng)條件分別是RPMI-1640加10%胎牛血清(fetal bovine serum,F(xiàn)BS)和DMEM加10% FBS,胃黏膜細胞GES-1的培養(yǎng)條件是DMEM加10% FBS,于37 ℃、5% CO2條件下培養(yǎng),0.25%胰蛋白酶消化傳代。轉(zhuǎn)染前1 d取生長狀態(tài)良好的細胞接種于6孔板中,每孔細胞數(shù)大約為3×105,次日細胞密度達到60%時進行轉(zhuǎn)染實驗,使用Lipofectamine 2000將miRNA-101-3p mimics或miRNA mimics NC轉(zhuǎn)入胃癌細胞MGC-803中,相應分為miRNA-101-3p mimics組、miRNA NC組及空白(blank)組,轉(zhuǎn)染8 h后,將無血清培養(yǎng)基更換為含10% FBS培養(yǎng)基繼續(xù)培養(yǎng),24 h后用流式細胞術觀察轉(zhuǎn)染效率,48 h后用熒光定量PCR檢測各組胃癌細胞中miRNA-101-3p和EZH2的表達水平。
2.2Real-time PCR 胰酶消化各組細胞后使用TRIzol試劑提取細胞中的RNA。應用miRNA熒光定量PCR試劑盒檢測miRNA-101-3p的表達,以U6為內(nèi)參照。擴增條件是: 94 ℃ 2 min; 94 ℃ 20 s, 60 ℃ 34 s, 40個循環(huán)。使用SYBR Premix Ex Taq試劑盒檢測EZH2的表達,以GAPDH為內(nèi)參照。EZH2上游引物序列為5’-AAAGAAAGCCGCCCACCT-3’,下游引物序列為5’-GGTCCATCTATGTTGGGGGTA-3’; GAPDH的上游引物序列為5’-GGATTTGGTGTCGTATTGGGC-3’,下游引物序列為5’-CGCTCCTGGAAGATGGTGAT-3’。擴增條件是: 95 ℃ 3 min; 95 ℃ 30 s, 56 ℃ 30 s, 72 ℃ 30 s, 40個循環(huán)。擴增結束后均進行熔解曲線分析,miRNA-101-3p和EZH2的相對表達水平采用2-ΔΔCt法計算。
2.3CCK-8比色法和臺盼藍染色法檢測細胞增殖 將轉(zhuǎn)染了miRNA-101-3p mimics或miRNA NC的胃癌細胞經(jīng)胰酶消化后重新接種于96孔板中,每孔中的細胞約為3×105個,于37 ℃、5% CO2培養(yǎng)箱中繼續(xù)培養(yǎng)24、48和72 h后,加入CCK-8試劑10 μL,混勻后繼續(xù)置于培養(yǎng)箱中1 h,使用酶聯(lián)免疫檢測儀測定450 nm處的吸光度(A)值,繪制生長曲線,每組設定3個復孔。采用臺盼藍染色進行活細胞計數(shù)時,轉(zhuǎn)染前一天將細胞按3×108/L接種于6孔板中,轉(zhuǎn)染48 h后收集細胞,使用臺盼藍染色后直接計數(shù)活細胞。
2.4流式細胞術檢測細胞周期和凋亡 轉(zhuǎn)染48 h后,收集miRNA-101-3p mimics、miRNA NC及空白對照組的細胞,細胞數(shù)大約為1×106個,使用預冷的PBS清洗2次,用70%的乙醇固定后置于4 ℃冰箱中過夜,再用預冷的PBS洗滌細胞2次,每管分別加入PI染色液(20×)和RNase A(50×),于37 ℃避光溫浴0.5 h后,使用流式細胞術檢測細胞周期。
轉(zhuǎn)染48 h后使用不含EDTA的胰酶消化各組細胞,用上清培養(yǎng)液終止消化,1 000 r/min離心5 min收集細胞,PBS清洗細胞2次,收集大約(1~5)×105個細胞,使用500 μL 1×Binding Buffer重懸細胞,相繼加入5 μL Annexin V-FITC和10 μL PI,室溫避光5 min后使用流式細胞術檢測各組的凋亡率。
2.5Transwell細胞遷移實驗 轉(zhuǎn)染24 h后,胰酶消化各組細胞并使用無血清培養(yǎng)基重懸細胞,調(diào)整細胞密度為2×108/L,取細胞懸液100 μL加在Transwell小室的上層,Transwell小室下層加入500 μL含10%血清培養(yǎng)基,置于37 ℃、5% CO2孵箱中繼續(xù)培養(yǎng)24 h后取出小室,PBS清洗后使用濕棉簽輕輕拭去上室中未遷移的細胞, 4%多聚甲醛固定20 min,PBS清洗3次后使用0.1%結晶紫染色10 min,PBS清洗后隨機選取5個視野,計數(shù)下室染色細胞。
2.6Western blot實驗 收集細胞后,使用RIPA裂解液(含1% PMSF)提取細胞中的蛋白質(zhì),使用BCA法測定蛋白濃度。取大約30 μg蛋白行10% SDS-PAGE分離蛋白,使用濕轉(zhuǎn)法電轉(zhuǎn)至NC膜上,5%脫脂奶粉室溫封閉2 h,抗EZH2(1∶2 000)和GAPDH(1∶5 000)抗體4 ℃孵育過夜,TBST洗3次后,加入HRP標記 II 抗(1∶8 000)室溫孵育1 h,TBST清洗3次后,ECL發(fā)光法顯影曝光,灰度值采用ImageJ軟件掃描并記錄,并分析目的蛋白與內(nèi)參照蛋白灰度的比值作為目的蛋白的相對表達量。
用SPSS 18.0統(tǒng)計軟件進行分析。數(shù)據(jù)均采用均數(shù)±標準差(mean±SD)表示,多組間比較采用單因素方差分析(one-way ANOVA),組間兩兩比較采用Bonferroni校正的t檢驗。以P<0.05為差異有統(tǒng)計學意義。
PCR結果顯示,miRNA-101-3p在胃癌細胞MGC-803和HGC-27中的表達量顯著低于胃黏膜細胞GES-1(P<0.05),其中胃癌細胞MGC-803中miRNA-101-3p的表達水平最低,故以胃癌細胞MGC-803作為后續(xù)的研究對象,見圖1。轉(zhuǎn)染48 h后,與miRNA NC組相比,miRNA-101-3p mimics組的miRNA-101-3p表達水平顯著上調(diào)(P<0.05),而miRNA NC組與空白組之間的差異沒有統(tǒng)計學顯著性,說明轉(zhuǎn)染成功; EZH2在miRNA-101-3p mimics組的水平顯著低于miRNA NC組和空白組(P<0.05),見圖2。
Figure 1. The expression of miRNA-101-3p in gastric mucosal cells and gastric cancer cells detected by real-time PCR. Mean±SD.n=3.*P<0.05vsGES-1.
圖1Real-timePCR檢測胃黏膜細胞和胃癌細胞中mi-RNA-101-3p的表達水平
Figure 2. The expression levels of miRNA-101-3p and EZH2 mRNA in MGC-803 cells after transfected with miRNA-101-3p mimics for 48 h were detected by real-time PCR. Mean±SD.n=3.*P<0.05vsmiRNA-101-3p mimics group.
圖2Real-timePCR檢測轉(zhuǎn)染48h后miRNA-101-3p和EZH2mRNA的表達水平
轉(zhuǎn)染24 h后,使用熒光顯微鏡觀察,結果顯示大約90%以上的細胞均呈紅色熒光蛋白Cy3陽性,并進一步使用流式細胞儀進行分選,結果說明轉(zhuǎn)染成功,見圖3。
轉(zhuǎn)染后使用CCK-8法測定各組細胞的吸光度(A)值,結果顯示,miRNA-101-3p mimics組在48和72 h時其吸光度值明顯低于miRNA NC組和空白對照組(P<0.05),而miRNA NC組和空白對照組之間的差異無統(tǒng)計學顯著性,見圖4A;同時采用臺盼藍染色法計數(shù)轉(zhuǎn)染后活細胞數(shù)量,結果顯示,miRNA-101-3p mimics組的活細胞數(shù)量顯著低于miRNA NC組和空白對照組(P<0.05),而miRNA NC組和空白對照組之間的活細胞數(shù)量沒有統(tǒng)計學顯著性,見圖4B。此結果說明過表達miRNA-101-3p后胃癌細胞MGC-803的生長受到抑制,細胞活力明顯降低。
Figure 3. The transfection efficiency after transfected with miRNA-101-3p mimics for 24 h (×200). A: the MGC-803 cells under phase-contrast microscope; B: the image of Cy3 positive staining of MGC-803 cells under fluorescence microscope; C: the intensity of red fluorescence in MGC-803 cells analyzed by flow cytometry.
圖3脂質(zhì)體轉(zhuǎn)染24h細胞轉(zhuǎn)染效率
Figure 4. The effect of miRNA-101-3p overexpression on the proliferation of gastric cancer cells. A: the viability of gastric cancer MGC-803 cells was dectected by CCK-8 assay; B: the number of gastric cancer cells was counted by trypan blue staining. Mean±SD.n=3.*P<0.05vsmiRNA-101-3p mimics.
圖4過表達miRNA-101-3p對胃癌細胞MGC-803增殖的影響
過表達miRNA-101-3p 48 h后,胃癌細胞的S期比例為(27.39±0.66)%,顯著低于NC組和空白對照組,而細胞分裂處于G0/G1期的胃癌細胞明顯增多(P<0.05),說明過表達miRNA-101-3p可以導致胃癌細胞出現(xiàn)G1期阻滯,進而抑制細胞的增殖,見圖5。
流式細胞儀檢測結果顯示,過表達miRNA-101-3p 48 h后,胃癌細胞早期凋亡率為(15.62±1.26)%,明顯高于NC組(6.20±1.07)%和空白對照組(4.54±1.32)%(P<0.05),說明miRNA-101-3p過表達可以促進胃癌細胞出現(xiàn)凋亡,見圖6。
Transwell細胞遷移實驗的結果顯示,過表達miRNA-101-3p后,胃癌細胞的遷移能力顯著降低,遷移的細胞數(shù)明顯低于miRNA NC組和空白對照組(P<0.05),說明過表達miRNA-101-3p可以抑制胃癌細胞遷移,見圖7。
利用在線軟件TargetScan進行生物信息學分析,預測結果顯示,EZH2是miRNA-101-3p的潛在靶基因。為了進一步確認miRNA-101-3p對EZH2基因的調(diào)控,Western blot實驗結果顯示,過表達miRNA-101-3p后,EZH2的表達明顯低于NC組和空白對照組(P<0.05),而NC組和空白對照組之間EZH2的表達沒有顯著變化,說明miRNA-101-3p可以抑制胃癌細胞MGC803中EZH2蛋白的表達;而胃癌細胞MGC-803和HGC-27中EZH2的水平顯著高于胃黏膜細胞GES-1(P<0.05),見圖8。
Figure 5. The effect of miRNA-101-3p overexpression on the cell cycle distribution of gastric cancer cells. Mean±SD.n=3.*P<0.05vsmiRNA-101-3p mimics.
圖5過表達miRNA-101-3p對胃癌細胞周期的影響
Figure 6. The effect of miRNA-101-3p overexpression on the apoptosis of gastric cancer cells. Mean±SD.n=3.*P<0.05vsmiRNA-101-3p mimics.
圖6過表達miRNA-101-3p對胃癌細胞凋亡的影響
Figure 7. The effect of miRNA-101-3p on the migration ability of gastric cancer cells detected by Transwell assay (×200). Mean±SD.n=3.*P<0.05vsmiRNA-101-3p mimics.
圖7Transwell遷移實驗檢測miRNA-101-3p對胃癌細胞遷移能力的影響
Figure 8. The protein expression of EZH2 in gastric cancer cells and gastric mucosal cells was detected by Western blot. Mean±SD.n=3.*P<0.05vsmiRNA-101-3p mimics;#P<0.05vsGES-1.
圖8Westernblot實驗檢測胃癌細胞和胃黏膜細胞中EZH2的蛋白表達
miRNA做為一種非編碼RNA,可以調(diào)控機體許多生理和病理過程,大約30%的編碼蛋白基因被miRNA所調(diào)控[10]。miRNA-101-3p在多種腫瘤中表達下調(diào),研究發(fā)現(xiàn),在肝癌中下調(diào)的miRNA-101-3p可以靶向調(diào)控髓細胞白血病基因1 (myeloid cell leukemia-1,Mcl-1)促進肝癌細胞凋亡,抑制肝癌細胞增殖[5];在乳腺癌中,miRNA-101-3p與生存期及淋巴轉(zhuǎn)移密切相關,并且可能通過調(diào)控CXC趨化因子受體7(CXC chemokine receptor, CXCR7)影響體內(nèi)細胞周期蛋白D1(cyclin D1)、B細胞白血病/淋巴瘤2(B-cell leukemia/lymphoma-2,Bcl-2)、基質(zhì)金屬蛋白酶2(matrixmetalloprotein 2,MMP2)、MMP-9和上皮鈣黏蛋白(E-cadherin)等蛋白的表達,進而抑制乳腺癌細胞的增殖[6]。在本研究中,miRNA-101-3p在胃癌細胞中的表達下調(diào),為了進一步研究miRNA-101-3p對胃癌細胞增殖、凋亡以及遷移的影響,采用脂質(zhì)體轉(zhuǎn)染技術過表達胃癌細胞中miRNA-101-3p的水平,結果顯示上調(diào)miRNA-101-3p的水平后,胃癌細胞的生長和遷移能力明顯受到抑制,細胞S期明顯減少,G0/G1期延長,細胞阻滯于G0/G1期,而細胞的早期凋亡率明顯增加;以上結果說明,miRNA-101-3p在胃癌的發(fā)生和發(fā)展中可能起到了抑癌基因的作用。
EZH2是表觀遺傳調(diào)控因子PcG蛋白的核心組件,在多種腫瘤[11-12]中表達增高,是腫瘤治療的潛在靶點。已有研究發(fā)現(xiàn)[13-14],胃癌組織中EZH2的表達明顯增高,而且與生存期密切相關。在本研究中我們也發(fā)現(xiàn)了胃癌細胞中EZH2的表達高于胃黏膜細胞;有學者發(fā)現(xiàn)[15],沉默胃癌細胞中EZH2的表達后可以誘導P53和組蛋白脫乙酰酶1(histone deacetylase 1, HDAC1)的表達,同時抑制cyclin D1和cyclin E的表達進而調(diào)控細胞的增殖; Bai等[16]也發(fā)現(xiàn),抑制EZH2的表達后可以抑制胃癌細胞SGC-7901的生長,激活p21和p16的表達,進而調(diào)控細胞周期;吳雪雷等[17]發(fā)現(xiàn) EZH2可以通過核因子κB(nuclear factor kappa B, NF-κB) 而抑制胃癌細胞的生長;還有的學者發(fā)現(xiàn),長鏈非編碼RNA 00152可通過結合EZH2而抑制p15和p21的表達,進而促進胃癌的進展[18],可見EZH2基因可能成為治療胃癌的重要靶點。在本研究中,通過生物學信息預測EZH2基因可能是miRNA-101-3p的潛在靶基因,也有學者[19]研究發(fā)現(xiàn)在前列腺癌和乳腺癌中EZH2基因受到miRNA-101-3p的靶向調(diào)控;而在其它腫瘤如膀胱癌[20]和肝癌[21]中通過雙熒光素報告基因也驗證了miRNA-101-3p對EZH2基因的靶向調(diào)控;本研究中,Western blot實驗顯示胃癌細胞中EZH2的表達顯著高于胃黏膜細胞,同時miRNA-101-3p的表達則低于胃黏膜細胞,而在上調(diào)胃癌細胞中的miRNA-101-3p后,EZH2的表達則明顯下調(diào)。因此我們推斷,在胃癌中EZH2與miRNA-101-3p的水平有可能呈負相關,并由于miRNA-101-3p下調(diào),使得其對EZH2基因的負調(diào)控作用減弱, EZH2的表達增加,而增高的EZH2蛋白又會影響E-cadherin[22]、整合素2[23]和印跡基因CDKN1C(p57KP12)[24]等的表達,從而最終促進了腫瘤的演進。
綜上所述,miRNA-101-3p可能通過靶向負調(diào)控EZH2基因的表達,進而抑制胃癌細胞的生長和遷移,促進胃癌細胞的凋亡。miRNA-101-3p有望成為治療胃癌的重要靶點。
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miRNA-101-3p inhibits proliferation and migration of gastric cancer cells by targeting EZH2
ZHANG Xiao-tian1, ZHANG Xiao-yan1, HUANG Sai-ya1, WANG Qian2, LIU Wei1
(1DepartmentofMedicalLaboratoryScience,FenyangCollegeofShanxiMedicalUniversity,Fenyang032200,China;2DepartmentofMedicalImaging,ShanxiMedicalUniversity,Taiyuan030001,China.E-mail: 116048164@qq.com)
AIM: To investigate the role of microRNA-101-3p (miRNA-101-3p) on the proliferation, apoptosis and invasion of gastric cancer cells and the possible regulatory mechanisms.METHODSThe expression of miRNA-101-3p in two kinds of gastric cancer cells and a gastric mucosal cell line was detected by real-time PCR. The miRNA-101-3p was overexpressed by Lipofectamine 2000 transfection with miRNA-101-3p mimics. The effects of miRNA-101-3p on cell cycle distribution and apoptosis were analyzed by flow cytometry. The effects of miRNA-101-3p on cell proliferation and migration abilities were detected by CCK-8 assay, trypan blue exclusion test and Transwell assay. The protein expression of enhancer of zeste homolog 2 (EZH2) was determined by Western blot.RESULTSThe expression of miRNA-101-3p in gastric cancer cells was lower than that in gastric mucosal cells (P<0.05). The gastric cancer cell MGC-803 had the lowest expression level of miRNA-101-3p. The result of flow cytometry showed that the population of S phase was reduced, and the population of G0/G1phase and the early stage apoptotic rate were increased after the expression of miRNA-101-3p was overexpressed (P<0.05). The results of CCK-8 assay, trypan blue exclusion test and Transwell assay showed that overexpression of miRNA-101-3p significantly reduced the proliferation and migration abilities of gastric cancer cells (P<0.05). Overexpression of miRNA-101-3p decreased the protein level of EZH2 (P<0.05).CONCLUSIONmiRNA-101-3p may suppresses the gastric cancer cell proliferation and migration, and promotes the gastric cancer cell apotosis by down-regulation of EZH2.
Gastric cancer; MicroRNA; Cell proliferation; Cell migration; Apotosis; Enhancer of zeste homolog 2
1000- 4718(2017)12- 2143- 08
2017- 07- 17
2017- 11- 07
國家自然科學基金資助項目(No. 81301426);山西醫(yī)科大學汾陽學院科研項目(No. 2017B05)
△通訊作者 Tel: 0358-2100372; E-mail: 116048164@qq.com
R735.2; R363.2
A
10.3969/j.issn.1000- 4718.2017.12.006
(責任編輯: 林白霜, 羅 森)