高 雪,葉 舟,吳克雄,范冬梅,楊 銘,張硯君,張益枝
[中國(guó)醫(yī)學(xué)科學(xué)院北京協(xié)和醫(yī)學(xué)院天津血液病醫(yī)院(血液學(xué)研究所),天津 300000]
血液病治療過程中產(chǎn)生耐藥性是治療失敗和復(fù)發(fā)的主要原因之一[1]。腫瘤細(xì)胞產(chǎn)生耐藥的原因主要有3個(gè)方面:(1)腫瘤耐藥相關(guān)基因的過表達(dá),如MDR1基因、MRP基因和LPR基因等。(2)酶系統(tǒng)的活性異常,如GSH、GST和DNA拓?fù)洚悩?gòu)酶等。(3)細(xì)胞凋亡異常:耐藥性腫瘤細(xì)胞內(nèi)抑制凋亡基因的異常表達(dá),如 Bcl-2基因[2-3]。目前針對(duì)腫瘤耐藥的治療和逆轉(zhuǎn)方法雖然取得了一定進(jìn)展,但用于臨床治療還有很多限制和不足,腫瘤耐藥產(chǎn)生及發(fā)展機(jī)制還需要不斷深入研究。
α烯醇化酶(eno1)是烯醇化酶家族成員之一,是結(jié)構(gòu)上高度保守的一種糖酵解酶,在脊椎動(dòng)物組織中廣泛存在。eno1主要與烯醇化酶家族其他成員形成同源或異源二聚體形式起作用。eno1與腫瘤發(fā)生、發(fā)展和多種疾病的發(fā)生密切相關(guān)。近年來研究發(fā)現(xiàn),在侵襲轉(zhuǎn)移性強(qiáng)和耐藥性的惡性腫瘤細(xì)胞中,eno1常處于過表達(dá)狀態(tài),如頭頸癌、乳腺癌和甲狀腺癌等[4-5]。本文主要探討eno1對(duì)人慢性粒細(xì)胞白血病耐藥細(xì)胞株K562/A02生長(zhǎng)及耐藥性的影響及機(jī)制,為耐藥性白血病治療提供一定的實(shí)驗(yàn)依據(jù)。
1.1 材料 人慢性粒細(xì)胞白血病細(xì)胞株K562和人慢性粒細(xì)胞白血病耐藥細(xì)胞株K562/A02由實(shí)驗(yàn)血液學(xué)國(guó)家重點(diǎn)實(shí)驗(yàn)室保存;pSilencerU6-sheno1質(zhì)粒和pSilencerU6-shcon質(zhì)粒有本室構(gòu)建和保存;TRIzol、Lipofectamine2000轉(zhuǎn)染試劑和MML-V逆轉(zhuǎn)錄試劑盒購(gòu)自美國(guó)Invitrogen公司;SYBR實(shí)時(shí)檢測(cè)試劑盒、G418、MTT和 DMSO購(gòu)自美國(guó) Sigma公司;RPMI 1640培養(yǎng)基粉劑購(gòu)自美國(guó)Gibco公司;eno1、MDR1和GAPDH抗體購(gòu)自CST公司;胎牛血清購(gòu)自天津?yàn)笊锛夹g(shù)有限公司。
1.2 細(xì)胞培養(yǎng)及eno1干擾細(xì)胞株的篩選 細(xì)胞培養(yǎng)于含10%胎牛血清的RPMI 1640培養(yǎng)液中,細(xì)胞為標(biāo)準(zhǔn)的懸浮生長(zhǎng)狀態(tài),常規(guī)傳代,培養(yǎng)于CO2濃度為5%的37℃恒溫細(xì)胞培養(yǎng)箱中。取對(duì)數(shù)生長(zhǎng)期細(xì)胞,接種1×105個(gè)細(xì)胞于24孔板中,培養(yǎng)24 h后將pSilencerU6-sheno1質(zhì)粒和pSilencerU6-shcon質(zhì)粒按照Lipofectamine2000轉(zhuǎn)染試劑說明進(jìn)行RNA干擾轉(zhuǎn)染實(shí)驗(yàn)。轉(zhuǎn)染48 h后加入250μg·L-1的G418進(jìn)行穩(wěn)定克隆篩選,14d后進(jìn)行細(xì)胞單克隆培養(yǎng),得到穩(wěn)定干擾的細(xì)胞株,分別取名為K562/A02-sheno1-1、K562/A02-sheno1-2、K562/A02-sheno1-3和 K562/A02-shcon。
1.3 細(xì)胞生長(zhǎng)速率和細(xì)胞增殖檢測(cè) 使用細(xì)胞計(jì)數(shù)法檢測(cè)細(xì)胞生長(zhǎng)速率:取對(duì)數(shù)生長(zhǎng)的細(xì)胞,接種于24孔板內(nèi),每孔5 000個(gè)細(xì)胞,每組設(shè)3個(gè)復(fù)孔。使用MTT法檢測(cè)細(xì)胞增殖:取對(duì)數(shù)生長(zhǎng)期細(xì)胞,調(diào)整細(xì)胞濃度為5×107·L-1,接種于96孔培養(yǎng)板中,每孔180μl細(xì)胞液。培養(yǎng)24 h后,將抗腫瘤藥物紫杉醇和阿霉素按照一定濃度加入培養(yǎng)板中,每個(gè)濃度設(shè)3個(gè)復(fù)孔,藥物體積為每孔20μl,繼續(xù)培養(yǎng)48 h。每孔加入20μl MTT溶液,恒溫培養(yǎng)箱中繼續(xù)培養(yǎng)4 h,每孔加入100μl DMSO溶解結(jié)晶,酶標(biāo)儀檢測(cè)各孔波長(zhǎng)570 nm處的吸光度值,計(jì)算IC50值。
1.4 羅丹明123蓄積實(shí)驗(yàn) 收集1×105個(gè)細(xì)胞,冷的PBS緩沖液沖洗3次。細(xì)胞重懸于300μl羅丹明123染液中,37℃恒溫振蕩水浴中避光孵育1h。收集細(xì)胞,冷的PBS緩沖液沖洗3次,用300μl PBS緩沖液重懸細(xì)胞,流式細(xì)胞儀檢測(cè)細(xì)胞熒光強(qiáng)度。
1.5 real-time PCR檢測(cè)基因 mRNA水平 按TRIzol試劑盒說明書提取細(xì)胞總RNA,瓊脂糖凝膠電泳鑒定其完整性,測(cè)定其260 nm和280 nm光密度值并計(jì)算RNA的純度與濃度。按照MML-V逆轉(zhuǎn)錄試劑盒說明進(jìn)行逆轉(zhuǎn)錄,獲得相應(yīng)cDNA。realtime PCR引物由上海生工生物工程股份有限公司合成。GAPDH:上游引物:5′-GAA GGT GAA GGT CGG AGT C-3′,下游引物:5′-GAA GAT GGT GAT GGG ATT TC-3′;eno1:上游引物:5′-AGC UGG UGC CGU UGA GAA GTT-3′,下游引物:5′-CUU CUC AAC GGCACC AGC UTT-3′。real-time PCR反應(yīng)按SYBR實(shí)時(shí)檢測(cè)試劑盒說明進(jìn)行。
1.6 Western blot檢測(cè)蛋白水平 收集1×106個(gè)細(xì)胞,冷的PBS緩沖液沖洗3次,將細(xì)胞轉(zhuǎn)移至EP管中,加入一定量RIPA裂解液,冰上裂解30 min,4℃12 000×g離心20 min收集上清液。BCA法測(cè)定各組蛋白濃度,取50μg蛋白經(jīng)SDS-PAGE電泳后,電轉(zhuǎn)印至NC膜上。5%脫脂奶粉室溫封閉1 h后,加入相應(yīng)一抗,4℃孵育過夜。PBST緩沖液洗膜3次后,加入辣根過氧化物酶標(biāo)記的二抗(1∶3 000稀釋),室溫孵育1 h。PBST緩沖液洗膜3次后進(jìn)行ECL化學(xué)發(fā)光試劑顯色,膠片曝光。
1.7 統(tǒng)計(jì)學(xué)方法 實(shí)驗(yàn)結(jié)果為3次重復(fù)實(shí)驗(yàn)結(jié)果。采用Quantity One軟件進(jìn)行Western blot條帶灰度分析;采用GraphPad Prism 5.0軟件分析和處理獲得的數(shù)據(jù);采用SPSS 13.0軟件進(jìn)行多組間單因素方差分析,兩組間采用獨(dú)立樣本t檢驗(yàn),計(jì)量資料以xˉ±s表示。
2.1 eno1在K562/A02細(xì)胞中過表達(dá) 細(xì)胞計(jì)數(shù)法檢測(cè)12、24、36、48和 60 h細(xì)胞數(shù)量發(fā)現(xiàn),K562/A02細(xì)胞生長(zhǎng)速率與敏感性K562細(xì)胞相比差異無顯著性。real-time PCR實(shí)驗(yàn)和Western blot實(shí)驗(yàn)結(jié)果顯示,K562/A02細(xì)胞中eno1基因在mRNA水平和蛋白水平均處于過表達(dá)狀態(tài)。與K562細(xì)胞相比,K562/A02細(xì)胞中eno1基因在mRNA水平表達(dá)增強(qiáng)(2.85±0.56)倍,在蛋白水平表達(dá)增強(qiáng)(1.43±0.05)倍 (Fig 1,2)。
Fig 1 Cell growth rate(performed by cell counting assay)There was no difference in cell growth between K562 cells and K562/A02 cells and numerical analysis data representˉx±s based on three independent experiments.
Fig 2 Expression of eno1 increases in K562/A02 cellsA:The mRNA expression level of eno1 was tested by real-time PCR assay.B:The protein expression level of eno1 was tested by western blot assay.Numerical analysis data representˉx±s based on three independent experiments,*P<0.05 vs K562.
2.2 穩(wěn)定干擾eno1細(xì)胞系的鑒定 使用本室構(gòu)建的RNA干擾質(zhì)粒pSilencerU6-sheno1和pSilencerU6-shcon轉(zhuǎn)染并干擾K562/A02細(xì)胞,經(jīng)G418篩選2周,單克隆細(xì)胞培養(yǎng)后得到穩(wěn)定干擾細(xì)胞系。real-time PCR檢測(cè)結(jié)果顯示,eno1穩(wěn)定干擾的3株細(xì)胞系在mRNA水平干擾效率分別為(43.15±0.03)%,(77.59±0.05)%和(57.04±0.06)%(Fig 3A)。Western blot檢測(cè)結(jié)果顯示,穩(wěn)定干擾eno1組中eno1蛋白無明顯表達(dá)(Fig 3B)。實(shí)驗(yàn)結(jié)果證明3株eno1穩(wěn)定干擾細(xì)胞系及對(duì)照細(xì)胞系成功建立。
Fig 3 eno1 stable silencing cell lines are identified in mRNA level and protein levelThree eno1 stable silencing cell lines were tested and results showed that eno1 stable silencing cell line was successfully established.Numerical analysis data representˉx±s based on three independent experiments,**P<0.01 vs K562/A02-shcon.
2.3 穩(wěn)定干擾eno1增強(qiáng)K562/A02細(xì)胞對(duì)抗腫瘤藥物紫杉醇和阿霉素的敏感 細(xì)胞計(jì)數(shù)法檢測(cè)結(jié)果顯示,K562/A02細(xì)胞穩(wěn)定干擾eno1后,其生長(zhǎng)速率明顯降低,其中K562/A02-sheno1-2生長(zhǎng)速率最低(Fig 4)。MTT法檢測(cè)結(jié)果顯示,K562/A02-sheno1組中紫杉醇和阿霉素對(duì)細(xì)胞增殖抑制明顯增強(qiáng),呈現(xiàn)劑量依賴性。對(duì)紫杉醇敏感性檢測(cè)結(jié)果顯示,紫杉醇對(duì) K562/A02-shcon、K562/A02-sheno1-1、K562/A02-sheno1-2和K562/A02-sheno1-3細(xì)胞系48 h的IC50值分別為(7.40±0.03)、(2.08±0.49)、(1.66±0.05)和(2.03±0.37)μmol·L-1;對(duì)阿霉素敏感性檢測(cè)結(jié)果顯示,阿霉素對(duì) K562/A02-shcon、K562/A02-sheno1-1、K562/A02-sheno1-2和 K562/A02-sheno1-3細(xì)胞系48 h的IC50值分別是(112.17±16.25)、(43.29±6.36)、(44.98±5.29)和(62.26±4.53)μmol·L-1。
Fig 4 Cell growth rate(performed by cell counting assay)Cell growth rate in K562/A02 cells was associated with eno1 and three eno1 stable silencing cell lines were tested.Numerical analysis data representˉx±s based on three independent experiments.
2.4 穩(wěn)定干擾 eno1增強(qiáng) K562/A02細(xì)胞羅丹明123蓄積能力 羅丹明123蓄積實(shí)驗(yàn)結(jié)果顯示,eno1穩(wěn)定干擾的細(xì)胞系K562/A02-sheno1-1、K562/A02-sheno1-2和 K562/A02-sheno1-3與對(duì)照組K562/A02-shcon相比,其羅丹明123含量分別提高了(59.05±0.15)%、(60.81±0.03)%和(50.82±1.02)%(Fig 5)。由此可知,eno1干擾增強(qiáng) K562/A02細(xì)胞藥物敏感性與其細(xì)胞膜上糖蛋白泵出藥物的能力有關(guān)。
2.5 穩(wěn)定干擾eno1對(duì)K562/A02細(xì)胞內(nèi)耐藥相關(guān)基因MDR1表達(dá)的影響 以GAPDH為內(nèi)參,在Fig 6 real-time PCR實(shí)驗(yàn)結(jié)果顯示,穩(wěn)定干擾eno1的細(xì)胞 系 K562/A02-sheno1-1、K562/A02-sheno1-2和K562/A02-sheno1-3實(shí)驗(yàn)組與對(duì)照組相比,MDR1基因mRNA表達(dá)分別降低(45.02±0.08)%、(73.21±0.05)%和(41.67±0.91)%。而且 Western blot檢測(cè)結(jié)果顯示,eno1穩(wěn)定干擾的細(xì)胞系K562/A02-sheno1-1、K562/A02-sheno1-2和 K562/A02-sheno1-3,與對(duì)照組相比,MDR1基因蛋白表達(dá)也明顯降低,其中K562/A02-sheno1-2細(xì)胞系中MDR1蛋白水平表達(dá)最低。
人慢性粒細(xì)胞白血病是一種抑制骨髓正常造血功能的惡性腫瘤,一般采用藥物治療和干細(xì)胞移植等治療方法,其治療效果取決于白血病的分期和病人身體狀況等因素[6]。藥物治療過程中腫瘤細(xì)胞會(huì)產(chǎn)生一定的耐藥性,導(dǎo)致治療失敗或復(fù)發(fā)。腫瘤耐藥的產(chǎn)生是一個(gè)復(fù)雜的、多因素參與的過程,目前研究主要集中于對(duì)耐藥相關(guān)基因MDR1的研究及逆轉(zhuǎn)耐藥的方法研究[7-8]。MDR1基因不僅與藥物轉(zhuǎn)運(yùn)功能相關(guān),有效降低腫瘤細(xì)胞內(nèi)藥物的濃度,并能有效抑制細(xì)胞凋亡[9]。
eno1是烯醇化酶家族成員之一,幾乎在人類所有組織中表達(dá),其通常作為金屬酶起作用。研究表明,eno1的表達(dá)水平與多種生物學(xué)功能和疾病相關(guān),如腫瘤,阿爾采末癥和肌細(xì)胞生成等[10-12]。近年來,eno1成為腫瘤研究領(lǐng)域的熱點(diǎn),eno1作為一種腫瘤標(biāo)志物,不僅與腫瘤的發(fā)生發(fā)展相關(guān),也與腫瘤耐藥性和侵襲轉(zhuǎn)移等相關(guān),且在多種耐藥性腫瘤中,eno1處于過表達(dá)狀態(tài)。Georges等[13]研究發(fā)現(xiàn),在肺癌細(xì)胞A549和H460,乳腺癌細(xì)胞株MCF-7和卵巢癌CaOV3中干擾eno1能增強(qiáng)細(xì)胞對(duì)抗腫瘤藥物的敏感性。在ER+的乳腺癌細(xì)胞中,eno1過表達(dá)不僅能促進(jìn)腫瘤的形成,還能增強(qiáng)乳腺癌耐他莫昔芬細(xì)胞對(duì)他莫昔芬的敏感性[14]。
Fig 5 Intra-cellular Rho123 content(detected by flow cytometry)Results showed that Rho123 content decreased in K562/A02-sheno1 cells compared to K562/A02-shcon cells.
Fig 6 Expression of MDR1 decreases in K562/A02-sheno1 cellsA:The mRNA expression level of eno1 was tested by real-time PCR assay.B:The protein expression level of eno1 was tested by western blot assay.Numerical analysis data representˉx±s based on three independent experiments,**P<0.01 vs K562/A02-shcon.
人慢性粒細(xì)胞白血病耐藥細(xì)胞株K562/A02由本室篩選并保存,前期研究發(fā)現(xiàn),K562/A02細(xì)胞不僅對(duì)誘導(dǎo)藥物阿霉素表現(xiàn)耐藥性,對(duì)其他部分抗腫瘤藥物也表現(xiàn)一定的耐藥性,為多藥耐藥細(xì)胞株,且K562/A02細(xì)胞耐藥機(jī)制為 MDR1基因過表達(dá)[15]。本研究發(fā)現(xiàn),與敏感性人慢性粒細(xì)胞白血病細(xì)胞株K562相比,耐藥細(xì)胞株 K562/A02中 eno1處于過表達(dá)狀態(tài),但是K562/A02細(xì)胞生長(zhǎng)速率與K562細(xì)胞無明顯差異,表明正常生長(zhǎng)狀態(tài)下,K562/A02細(xì)胞內(nèi)eno1需要處于過表達(dá)狀態(tài)。
本文成功構(gòu)建3株eno1穩(wěn)定干擾的細(xì)胞系K562/A02-sheno1-1、K562/A02-sheno1-2和 K562/A02-sheno1-3,細(xì)胞形態(tài)觀察發(fā)現(xiàn)eno1穩(wěn)定干擾細(xì)胞系 K562/A02-sheno1,與對(duì)照組 K562/A02-shcon相比,細(xì)胞形態(tài)無明顯改變,表明eno1在K562/A02細(xì)胞中對(duì)細(xì)胞形態(tài)維持無明顯影響。
細(xì)胞計(jì)數(shù)法檢測(cè)發(fā)現(xiàn),eno1穩(wěn)定干擾后細(xì)胞生長(zhǎng)速率明顯減慢,表明eno1可能與K562/A02細(xì)胞生長(zhǎng)密切相關(guān)。細(xì)胞對(duì)抗腫瘤藥物敏感性實(shí)驗(yàn)結(jié)果表明,eno1穩(wěn)定干擾能有效逆轉(zhuǎn)細(xì)胞耐藥,使抗腫瘤藥物紫杉醇和阿霉素對(duì)腫瘤細(xì)胞的IC50明顯降低。進(jìn)一步檢測(cè)細(xì)胞藥物蓄積能力發(fā)現(xiàn),與對(duì)照組細(xì)胞K562/A02-shcon相比,eno1穩(wěn)定干擾細(xì)胞系K562/A02-sheno1對(duì)羅丹明123的外排能力明顯增強(qiáng),細(xì)胞內(nèi)藥物蓄積減少。因K562/A02細(xì)胞耐藥主要由MDR1基因過表達(dá)影響,而eno1穩(wěn)定干擾細(xì)胞系其藥物外排能力明顯增強(qiáng),表明eno1對(duì)K562/A02細(xì)胞耐藥性影響可能通過調(diào)控MDR1基因表達(dá)實(shí)現(xiàn)。real-time PCR實(shí)驗(yàn)和Western blot實(shí)驗(yàn)結(jié)果表明,eno1穩(wěn)定干擾細(xì)胞系K562/A02-sheno1細(xì)胞內(nèi)MDR1基因在mRNA水平和蛋白水平表達(dá)均顯著性降低,證明干擾eno1通過有效降低K562/A02細(xì)胞中耐藥相關(guān)基因MDR1表達(dá)來增強(qiáng)細(xì)胞對(duì)抗腫瘤藥物的敏感性,減弱細(xì)胞對(duì)抗腫瘤藥物的外排能力。
綜上所述,本研究發(fā)現(xiàn),eno1過表達(dá)狀態(tài)是人慢性粒細(xì)胞白血病耐藥細(xì)胞株K562/A02正常生長(zhǎng)所必需的條件,干擾eno1后明顯抑制K562/A02細(xì)胞生長(zhǎng)。eno1還可作為逆轉(zhuǎn)人慢性粒細(xì)胞白血病耐藥細(xì)胞株 K562/A02中 MDR1的靶位點(diǎn),干擾eno1表達(dá),有效降低細(xì)胞內(nèi)耐藥相關(guān)基因MDR1在mRNA水平和蛋白水平的表達(dá),從而增強(qiáng)耐藥細(xì)胞對(duì)抗腫瘤藥物的敏感性。本研究將進(jìn)一步研究eno1對(duì)耐藥細(xì)胞增強(qiáng)藥物敏感性的機(jī)制,為人慢性粒細(xì)胞白血病耐藥治療提供新線索。
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