胡建軍,鄭華榮,鄭耀紅(常山縣人民醫(yī)院檢驗(yàn)科,浙江衢州 324200)
miR-363下調(diào)HepG2細(xì)胞Mcl-1蛋白的表達(dá)并誘導(dǎo)其凋亡
胡建軍△,鄭華榮,鄭耀紅
(常山縣人民醫(yī)院檢驗(yàn)科,浙江衢州324200)
[摘要]目的:探討微小RNA-363( microRNA-363,miR-363)的作用靶點(diǎn)及其對(duì)HepG2細(xì)胞的抑制作用。方法:通過生物信息學(xué)分析預(yù)測(cè)Mcl-1基因是否受microRNA調(diào)控。實(shí)時(shí)熒光定量PCR檢測(cè)正常肝細(xì)胞系LO2及肝癌細(xì)胞系HepG2、Huh7、PLC的miR-363和Mcl-1的表達(dá)水平。將miR-363轉(zhuǎn)染人HepG2細(xì)胞,檢測(cè)miR-363對(duì)Mcl-1表達(dá)水平的影響。MTT法檢測(cè)HepG2細(xì)胞在轉(zhuǎn)染miR-363后的相對(duì)細(xì)胞活力,Annexin V/PI染色法檢測(cè)miR-363轉(zhuǎn)染對(duì)HepG2細(xì)胞凋亡的影響。結(jié)果: Mcl-1 mRNA 3’-非翻譯區(qū)( 3’-UTR)存在miR-363的假定結(jié)合位點(diǎn),在肝癌細(xì)胞中轉(zhuǎn)染miR-363后Mcl-1的表達(dá)下降。轉(zhuǎn)染miR-363可抑制HepG2細(xì)胞的活力并誘導(dǎo)其發(fā)生凋亡。結(jié)論: miR-363過表達(dá)可顯著抑制HepG2細(xì)胞的活力并誘導(dǎo)其發(fā)生凋亡,其機(jī)制可能與miR-363能下調(diào)HepG2細(xì)胞Mcl-1蛋白的表達(dá)有關(guān)。
[關(guān)鍵詞]微小RNA-363; Mcl-1; HepG2細(xì)胞;細(xì)胞凋亡
肝細(xì)胞癌( hepatocellular carcinoma,HCC)是危害人類健康的世界性難題,其預(yù)后差,生存時(shí)間較短,死亡率居所有惡性腫瘤的第3位[1]。然而,肝細(xì)胞肝癌的發(fā)病機(jī)制至今仍不十分清楚,一些細(xì)胞保護(hù)性蛋白的高度表達(dá)可能是HCC發(fā)病的重要原因[2]。Mcl-1是Bcl-2蛋白家族中的抗凋亡蛋白成員,包含3個(gè)BH位點(diǎn),通過與促凋亡蛋白Noxa、puma、bim、bid等的結(jié)合使之失活而發(fā)揮抗凋亡效應(yīng)[3]。有文獻(xiàn)報(bào)道腫瘤細(xì)胞利用Mcl-1的高度表達(dá)逃避細(xì)胞的程序性死亡,這也成為了腫瘤細(xì)胞對(duì)一些化療藥物耐藥的重要機(jī)制[4-5]。MicroRNA是近年來備受關(guān)注的一類細(xì)胞內(nèi)源性的、非編碼的小分子RNA,通過與其靶mRNA分子的3’端非編碼區(qū)( 3’-UTR)不完全互補(bǔ)結(jié)合,調(diào)節(jié)靶基因在轉(zhuǎn)錄后的蛋白表達(dá)水平[6-7]。近些年來的研究還表明,microRNA在腫瘤的發(fā)生發(fā)展過程中,發(fā)揮著重要的調(diào)節(jié)作用,腫瘤的發(fā)生往往伴隨著細(xì)胞內(nèi)miRNA表達(dá)的失衡。有文獻(xiàn)報(bào)道[8-9]微小RNA-363( microRNA-363,miR-363)在多種腫瘤細(xì)胞中表達(dá)失調(diào),與腫瘤的發(fā)生發(fā)展及轉(zhuǎn)移等密切相關(guān),然而miR-363對(duì)肝癌的生物效應(yīng)卻很少報(bào)道。在本研究中,我們發(fā)現(xiàn)miR-363靶向于Mcl-1 mRNA的3’-UTR區(qū),轉(zhuǎn)染miR-363模擬物能抑制肝癌細(xì)胞的生長并促進(jìn)其凋亡。
1實(shí)驗(yàn)材料
人肝癌細(xì)胞株HepG2、Huh7、PLC和人正常肝細(xì)胞系LO2購于上海生科院細(xì)胞庫,細(xì)胞培養(yǎng)在RPMI-1640培養(yǎng)基中,含10%胎牛血清,培養(yǎng)條件為37℃恒溫培養(yǎng)并通入5% CO2。RPMI-1640培養(yǎng)基購于Gibco;胎牛血清( FBS)購于杭州四季青生物工程有限公司; miR-363模擬物序列為5’-AAUUGCACGGUAUCCAUCUGUA-3’、對(duì)照RNA( control RNA)序列為5’-UUCUCCGAACGUGUCACGU-3’,購自廣州銳博生物;噻唑藍(lán)( MTT)、Annexin V-FITC凋亡檢測(cè)試劑盒購于Sigma;細(xì)胞裂解液、兔抗人Mcl-1和兔抗人β-actin購于CST; Lipofectamine 2000、TRIzol購于Invitrogen;逆轉(zhuǎn)錄試劑盒、SYBR Green購于TaKaRa; ECL顯色試劑盒購自Pierce。
2主要方法
2.1Real-time PCR檢測(cè)HCC細(xì)胞及LO2細(xì)胞miR-363和Mcl-1的表達(dá)水平將5×105個(gè)HepG2細(xì)胞接種于6孔板中進(jìn)行培養(yǎng),待細(xì)胞鋪滿培養(yǎng)板80%時(shí),將miR-363(每孔100 pmol)或?qū)φ誖NA(每孔100 pmol)通過Lipofectamine 2000按試劑說明書要求轉(zhuǎn)入HepG2細(xì)胞培養(yǎng)24 h,對(duì)照組不做任何處理培養(yǎng)24 h,收集細(xì)胞,進(jìn)行real-time PCR??俁NA 用TRIzol試劑提取,miR-363采用特異性莖環(huán)引物法[10]進(jìn)行miR-363的逆轉(zhuǎn)錄,Mcl-1直接用逆轉(zhuǎn)錄試劑盒將總RNA逆轉(zhuǎn)成cDNA,操作步驟照試劑盒說明書進(jìn)行。逆轉(zhuǎn)錄產(chǎn)物用SYBR Green試劑按照說明書進(jìn)行處理并在Applied Biosystems 7500 Real Time PCR System上進(jìn)行PCR擴(kuò)增,Mcl-1基因以GAPDH的mRNA作為內(nèi)參照,miR-363以U6 small nuclear RNA( snRNA U6)作為內(nèi)參照,用2-ΔΔCt法分析Mcl-1和miR-363的相對(duì)表達(dá)[11]。PCR引物序列見表1。
2.2Western blot檢測(cè)HCC細(xì)胞或LO2細(xì)胞Mcl-1的表達(dá)水平收集細(xì)胞,將細(xì)胞裂解后將蛋白提取液行12.5%SDS-PAGE,之后將蛋白轉(zhuǎn)膜到PVDF膜( Millipore)上。將膜在兔抗人Mcl-1或兔抗人β-actin I抗稀釋液中孵育過夜,之后再在帶HRP酶活性的羊抗兔IgG II抗稀釋液中孵育2 h,ECL試劑顯色曝光。
表1 PCR引物序列Table 1.The sequence of PCR primers
2.3MTT法檢測(cè)細(xì)胞活力將HepG2細(xì)胞接種于96孔板中培養(yǎng)16 h,按操作說明書將miR-363(每孔5 pmol)或?qū)φ誖NA(每孔5 pmol)用Lipofectamine 2000轉(zhuǎn)入HepG2細(xì)胞,培養(yǎng)24 h,對(duì)照組不做任何處理培養(yǎng)24 h,之后加5 g/L MTT 20 μL,繼續(xù)培養(yǎng)4 h。棄上清,往孔中加150 μL DMSO,振蕩使紫色絮狀物完全溶解,570 nm波長下用酶標(biāo)儀檢測(cè)吸光度( A)值,細(xì)胞的活力以A570表示。
2.4細(xì)胞凋亡檢測(cè)將HepG2細(xì)胞接種于6孔板中培養(yǎng)16 h,按操作說明書將miR-363(每孔100 pmol)或control RNA (每孔100 pmol)用Lipofectamine 2000轉(zhuǎn)入HepG2細(xì)胞,培養(yǎng)24 h,對(duì)照組不做任何處理培養(yǎng)24 h,收集細(xì)胞,按照試劑說明書將PI和Annexin V加入細(xì)胞中孵育20 min,采用流式細(xì)胞術(shù)檢測(cè)腫瘤細(xì)胞的凋亡。
2.5生物信息學(xué)預(yù)測(cè)miR-363靶基因?qū)iR-363靶基因的預(yù)測(cè)采用Target Scan Human 6.2在線工具( http: / /www.targetscan.org/),若靶基因的3’UTR存在能與miR-363發(fā)生非完美互補(bǔ)配對(duì)的序列(至少有6對(duì)堿基連續(xù)互補(bǔ)配對(duì)),則該基因視為miR-363的潛在靶基因。
3統(tǒng)計(jì)學(xué)處理
所有實(shí)驗(yàn)重復(fù)3次,實(shí)驗(yàn)數(shù)據(jù)用均數(shù)±標(biāo)準(zhǔn)差( mean±SD)表示。數(shù)據(jù)統(tǒng)計(jì)用SPSS 13.0進(jìn)行分析,2組間數(shù)據(jù)差異用雙側(cè)t檢驗(yàn)分析,以P<0.05為差異有統(tǒng)計(jì)學(xué)意義。
1 肝癌細(xì)胞高表達(dá)Mcl-1
為了明確Mcl-1是否在肝癌細(xì)胞中高表達(dá),我們用real-time PCR和Western blot方法檢測(cè)人正常肝細(xì)胞系LO2及人肝癌細(xì)胞系HepG2、Huh7和PLC的Mcl-1表達(dá)水平,結(jié)果表明3種肝癌細(xì)胞系相比于LO2細(xì)胞Mcl-1的表達(dá),不論mRNA水平還是蛋白水平均顯著上升,見圖1。
Figure 1.The expression of Mcl-1 at mRNA and protein levels in HCC cells and LO2 cells.Mean±SD.n = 3.*P<0. 05 vs LO2 cells.圖1 HCC細(xì)胞Mcl-1的mRNA及蛋白表達(dá)水平相比于正常肝細(xì)胞顯著升高
2 HCC細(xì)胞Mcl-1受miR-363調(diào)控
為了研究HCC細(xì)胞中Mcl-1是否受microRNA調(diào)控,我們嘗試通過TargetScan工具預(yù)測(cè)Mcl-1的調(diào)控microRNA,結(jié)果發(fā)現(xiàn)Mcl-1 mRNA 3’-UTR確實(shí)存在miR-363的作用靶點(diǎn)( GUGCAAU,3’-UTR的第12 ~18個(gè)堿基),見圖2。因此我們用熒光定量PCR法檢測(cè)HCC細(xì)胞和LO2細(xì)胞miR-363的表達(dá)水平,發(fā)現(xiàn)HCC細(xì)胞相比于LO2細(xì)胞miR-363表達(dá)水平減少,這些結(jié)果提示Mcl-1表達(dá)可能和miR-363存在反比關(guān)系,見圖3。為了進(jìn)一步明確miR-363調(diào)控Mcl-1的表達(dá)水平,我們將miR-363相對(duì)表達(dá)水平最低的HepG2細(xì)胞作為研究對(duì)象,用real-time PCR方法檢測(cè)miR-363的轉(zhuǎn)染效率和Mcl-1的表達(dá),結(jié)果發(fā)現(xiàn)miR-363轉(zhuǎn)染后,HepG2細(xì)胞的miR-363表達(dá)水平相比于轉(zhuǎn)染對(duì)照RNA提高了10.245倍,而轉(zhuǎn)染miR-363模擬物相比于轉(zhuǎn)染對(duì)照RNA可顯著降低Mcl-1 mRNA及蛋白表達(dá)水平,表明miR-363確實(shí)能下調(diào)Mcl-1的水平,見圖4。
Figure 2.The putative miR-363 binding site in 3’-UTR of Mcl-1 gene.圖2 Mcl-1 3’-UTR存在miR-363的結(jié)合位點(diǎn)
Figure 3.The expression of miR-363 in HCC cells and LO2 cells.Mean±SD.n =3.*P<0. 05 vs LO2 cells.圖3 HCC細(xì)胞miR-363的表達(dá)水平相比于正常肝LO2細(xì)胞顯著降低
Figure 4.The exogenous miR-363 significantly increased the expression of miR-363 and decreased the levels of Mcl-1 in HepG2 cells.Mean±SD.n =3.*P<0. 05 vs control RNA group.圖4 miR-363轉(zhuǎn)染顯著提高HepG2細(xì)胞miR-363表達(dá)水平并降低細(xì)胞內(nèi)Mcl-1的表達(dá)水平
3 miR-363抑制HepG2細(xì)胞的細(xì)胞活力并誘導(dǎo)細(xì)胞凋亡
為了研究miR-363對(duì)HepG2細(xì)胞活力的抑制作用,我們用MTT法檢測(cè)HepG2細(xì)胞在miR-363治療下的增殖情況,結(jié)果發(fā)現(xiàn)miR-363組相比于對(duì)照RNA組,細(xì)胞活力顯著降低,見圖5。Mcl-1為抗凋亡蛋白,因此我們用流式細(xì)胞術(shù)檢測(cè)miR-363是否通過誘導(dǎo)HepG2的凋亡來抑制HepG2細(xì)胞的活力,結(jié)果發(fā)現(xiàn)miR-363組相比于control RNA組,細(xì)胞凋亡水平提高,見圖6。這些結(jié)果提示了miR-363通過下調(diào)Mcl-1的表達(dá)抑制肝癌細(xì)胞生長并誘導(dǎo)其發(fā)生凋亡。
Figure 5.miR-363 decreased the cell activity of HepG2 cells.Mean±SD.n =3.*P<0. 05 vs control RNA group.圖5 miR-363顯著抑制HepG2的細(xì)胞活力
Figure 6.miR-363 induced apoptosis of HepG2.圖6 miR-363誘導(dǎo)HepG2細(xì)胞凋亡
Mcl-1是Bcl-2蛋白家族中關(guān)鍵的抗凋亡蛋白,Mcl-1在人類各種腫瘤細(xì)胞系中均高度表達(dá)。Sieghart等[12]發(fā)現(xiàn)149個(gè)肝細(xì)胞肝癌患者中有51%的患者的肝腫瘤組織中高度表達(dá)Mcl-1,而腫瘤組織附近的正常肝組織Mcl-1的表達(dá)量卻很低,表明Mcl-1的過表達(dá)是腫瘤特異性改變之一。將腫瘤細(xì)胞的Mcl-1基因沉默后會(huì)引起腫瘤細(xì)胞凋亡,但不影響正常肝細(xì)胞的生物學(xué)性狀[13-14]。Mcl-1對(duì)其它類型的腫瘤也起著十分重要的作用,Thallinger等[15]發(fā)現(xiàn)在患有黑色素瘤的重癥聯(lián)合免疫缺陷小鼠的皮下腫瘤組織中注射Mcl-1的反義寡核苷酸可以增加腫瘤細(xì)胞對(duì)化療藥物達(dá)卡巴嗪的敏感性,并且使腫瘤細(xì)胞的凋亡程度增加。這些研究都提示了Mcl-1可以作為腫瘤治療的一個(gè)重要靶點(diǎn)。
MicroRNAs是一種生物效應(yīng)很強(qiáng)的小分子核酸,在細(xì)胞中通過調(diào)節(jié)對(duì)應(yīng)基因的表達(dá)參與細(xì)胞各項(xiàng)生理活動(dòng)。研究表明microRNAs表達(dá)的改變往往會(huì)導(dǎo)致腫瘤的發(fā)生[16],一些特定的microRNAs還被用作腫瘤診斷及預(yù)后的評(píng)價(jià)指標(biāo)[17]。miR-363是一個(gè)細(xì)胞中有廣泛生物學(xué)效應(yīng)的microRNA,近期的研究還發(fā)現(xiàn)miR-363在多種腫瘤組織表達(dá)失調(diào)。Ng等[18]的研究表明miR-363在NK/T細(xì)胞淋巴瘤中起腫瘤抑制作用。此外,miR-363在高轉(zhuǎn)移性頭頸部鱗狀細(xì)胞癌中同樣表達(dá)下調(diào)[19]。
我們?cè)诒狙芯恐凶C實(shí)了miR-363的表達(dá)在3種肝腫瘤細(xì)胞系中相比于正常肝細(xì)胞系均顯著下降,而Mcl-1基因在肝癌細(xì)胞中相比于正常肝細(xì)胞系表達(dá)顯著升高,兩者存在反比關(guān)系,提示miR-363在肝癌細(xì)胞中起腫瘤抑制作用,而Mcl-1則可能對(duì)腫瘤發(fā)展有促進(jìn)作用。我們?cè)谶M(jìn)一步的實(shí)驗(yàn)中發(fā)現(xiàn)在HepG2細(xì)胞中轉(zhuǎn)染miR-363相比于轉(zhuǎn)染對(duì)照RNA可顯著抑制其細(xì)胞活力。為了研究其機(jī)制,我們通過生物信息學(xué)方法尋找miR-363的潛在靶基因,結(jié)果發(fā)現(xiàn)Mcl-1可能受miR-363的調(diào)控。為了驗(yàn)證這一假設(shè),我們將miR-363轉(zhuǎn)染HepG2細(xì)胞后,檢測(cè)細(xì)胞內(nèi)Mcl-1的表達(dá)水平,結(jié)果發(fā)現(xiàn)miR-363的轉(zhuǎn)染確實(shí)能引起Mcl-1的下調(diào),表明Mcl-1為miR-363的靶基因。Mcl-1已經(jīng)被證實(shí)屬于Bcl-2家族中的抗凋亡蛋白,因此我們推測(cè)miR-363抑制HepG2細(xì)胞活力的機(jī)制可能和細(xì)胞凋亡有關(guān)。為了驗(yàn)證這一假設(shè),我們通過流式細(xì)胞術(shù)檢測(cè)HepG2細(xì)胞在轉(zhuǎn)染miR-363后細(xì)胞的凋亡程度,結(jié)果證實(shí)了miR-363確實(shí)能誘導(dǎo)HepG2的凋亡。結(jié)合這些實(shí)驗(yàn)結(jié)果,我們的研究表明miR-363為一腫瘤抑制性miRNA,其過表達(dá)能顯著抑制肝腫瘤細(xì)胞的細(xì)胞活力,其機(jī)制為miR-363下調(diào)腫瘤細(xì)胞內(nèi)抗凋亡蛋白Mcl-1的表達(dá)水平,進(jìn)而誘導(dǎo)細(xì)胞發(fā)生凋亡。本研究的意義在于提示了miR-363-Mcl-1途徑可能成為一個(gè)新的治療肝細(xì)胞肝癌的重要靶點(diǎn)。
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·綜述·
miR-363 downregulates Mcl-1 expression and induces apoptosis in HepG2 cells
HU Jian-jun,ZHENG Hua-rong,ZHENG Yao-hong
( Changshan People’s Hospital,Quzhou 324200,China.E-mail: changshanhujianjun@163.com)
[ABSTRACT]AIM: To determine the effect of microRNA-363( miR-363) on HepG2 cells.METHODS: Bioinformatic analysis was conducted to identify if the Mcl-1 was regulated by miR-363.The expression of Mcl-1 and miR-363 was detected by real-time PCR in normal liver cell line LO2 and hepatocellular carcinoma cell line HepG2,Huh7 and PLC.miR-363 was transfected into the HepG2 cells,and then the level of Mcl-1 was measured.The relative viability was evaluated by MTT assay after the HepG2 cells were transfected with miR-363,and the apoptosis was analyzed by flow cytometry with Annexin V/PI staining.RESULTS: Bioinformatic analysis identified that there was a putative target site in the Mcl-1 mRNA for miR-363.Transfection of miR-363 mimics suppressed Mcl-1 expression in the HepG2 cells.Transfection of miR-363 mimics inhibited the cell viability as well as inducing cell apoptosis in HepG2 cells.CONCLUSION: Over-expression of miR-363 significantly inhibits the cell viability and induces apoptosis in HepG2 cells,and the mechanism may be related to the downregulation of Mcl-1 caused by miR-363 transfection.
[KEY WORDS]MicroRNA-363; Mcl-1; HepG2 cells; Apoptosis
通訊作者△Tel: 0570-5039003; E-mail: changshanhujianjun@163.com
[收稿日期]2014-12-10[修回日期]2015-01-31
[文章編號(hào)]1000-4718( 2015)07-1329-05
[中圖分類號(hào)]R735. 7; R730. 23
[文獻(xiàn)標(biāo)志碼]A
doi:10.3969/j.issn.1000-4718.2015.07.032