姜黄素通过活化PI3K/Akt信号通路逆转肝癌耐药细胞株Bel7402/ADR的耐药性

目的探讨磷脂酰肌醇3激酶/蛋白激酶B(PI3K/Akt)信号通路的活化在姜黄素逆转肝癌耐药细胞株Bel7402/ADR耐药中的作用。方法采用阿霉素药物浓度递增法诱导建立肝癌耐药细胞株Bel7402/ADR;MTT法检测Bel7402/ADR细胞对阿霉素的敏感性,姜黄素对Bel7402/ADR细胞活性的影响及姜黄素对Bel7402/ADR细胞耐药逆转的作用;流式细胞仪检测细胞凋亡率;Western印迹法检测Bel7402和Bel7402/ADR细胞株中PI3K/AKT蛋白的表达水平;构建Bel7402/ADR皮下瘤模型,考察姜黄素对肿瘤生长的影响,最后通过检测小鼠体重及观察小鼠主要脏器的病理切片分析药物的在体毒性。结果 Bel7402/ADR细胞对阿霉素的半数抑制浓度(IC50)值为(1514.6±12.6)μg/ml,耐药倍数为24.3;姜黄素对Bel7402和Bel7402/ADR细胞活性均具有一定的抑制作用,IC50值分别为:(95.8±3.9)μg/ml和(101.4±3.1)μg/ml;5、10μg/ml姜黄素为Bel7402/ADR细胞无毒剂量,对Bel7402/ADR细胞的耐药逆转倍数分别为:1.97和3.51倍,并诱导细胞凋亡。姜黄素可以诱导细胞中PI3K/Akt蛋白表达水平的降低,并随着姜黄素的浓度升高而降低;姜黄素联合阿霉素可以有效抑制肿瘤生长,并表现很低的在体毒性。结论姜黄素在体和离体上可以显著逆转Bel7402/ADR的耐药性,并表现出很好的抗肿瘤效果,姜黄素的耐药逆转机制可能是抑制PI3K/Akt信号通路活化,下调PI3K/Akt蛋白表达,降低细胞对阿霉素的耐受性。     

芹菜素通过下调MDR-1/P-gp表达逆转结肠癌耐药细胞HCT-8/5FU多药耐药性的作用及机制

目的探讨芹菜素逆转结肠癌耐药细胞HCT-8/5FU多药耐药性作用及其机制。方法运用免疫细胞化学技术和逆转录多聚酶链式反应(RT-PCR)测定耐药蛋白P-糖蛋白(P-gp)及耐药基因MDR-1mRNA的表达情况。CCK-8法测定芹菜素对耐药细胞耐药逆转作用;荧光显微镜观察芹菜素、5-FU及二者联合作用时耐药细胞凋亡情况。结果芹菜素能够降低耐药蛋白P-gp糖蛋白及耐药基因MDR-1 mRNA的表达,同时能够逆转耐药细胞的多药耐药性,诱导更多细胞凋亡。结论菜素能够通过下调MDR-1/P-gp表达逆转HCT-8/5FU多药耐药性,从而有可能成为临床多药耐药逆转剂。     

芪竹方对结肠癌耐药株HCT-8/V及肝癌耐药株Bel/Fu细胞耐药体外逆转作用的观察

[目的]研究芪竹方对结肠癌耐药株HCT-8/V、肝癌耐药株Bel/FU体外逆转作用.[方法]血清药理法制备芪竹方含药血清,MTT法检测芪竹方及其含药血清对HCT-8/V及Bel/FU细胞耐药逆转作用.[结果]芪竹方250 μg/ml、50μg/ml、芪竹方20％含药血清、10％含药血清均可逆转HCT-8/V细胞的耐药性（P＜0.05）,其逆转倍数分别为14.65、6.20、6.53、3.01;芪竹方及其含药血清对Bel/FU细胞耐药性无逆转作用.[结论]芪竹方可体外逆转结肠癌耐药细胞株HCT-8/V耐药性,而对Bel/FU细胞无体外逆转作用.     

高温对SGC7901/ADM细胞多药耐药蛋白表达的影响和意义

目的:研究高温43℃对多药耐药基因表达产物P-gp、MRP、LRP在蛋白水平上的影响及其生物学意义,更深入地了解热效应逆转耐药的机制.方法:采用免疫细胞化学染色法、RT-PCR以及Western blot方法,检测在不同温度和不同药物作用下,人胃癌耐药细胞株SGC7901/ADM和对照的人胃癌敏感细胞SGC7901株中,与人胃癌多药耐药相关的分子MDR1、P-gp、MRP、LRP在蛋白水平上的表达差异.结果:采用免疫细胞化学染色法检测人胃癌耐药株SGC7901/ADM细胞,发现高温43℃60 min处理可使P-gp蛋白表达下调率(down-regulated rate,DRR)31.78%(P=0.016),而MRP表达DRR为20.22%(P=0.037),差异有统计学意义,LRP未表达.采用Western blot法在SGC7901细胞中未检测出P-gp蛋白表达,而SGC7901/ADM细胞中P-gp高表达;在ADM和CDDP处理组细胞中,高温43℃时P-gp的表达量较37℃时DRR分别为45.65%(P=0.007)、17.95%(P=0.021),差异有显著学意义;TAX处理组DRR为11.90%,差异无显著学意义(P=0.065).结论:高温43℃的短期处理对人胃癌SGC7901/ADM细胞中P-gp和MRP多药耐药蛋白的表达有一定的抑制作用,可能是逆转耐药的机制之一.     

耐药相关蛋白在肺癌组织的表达与药物敏感性的关系

目的探讨耐药相关蛋白在肺癌组织中的表达与药物敏感性的关系。方法应用免疫组化法、四唑蓝快速比色法(MTT法)分别检测P-糖蛋白(P-gp)、多药耐药相关蛋白(MRP)、肺耐药蛋白(LRP)、谷胱苷肽s转移酶(GST-π)蛋白在87例肺癌组织中的表达和10种抗癌药的体外药敏试验。结果P-gp、MRP、GST-π阳性表达及高表达者中,腺癌组药物敏感数明显低于鳞癌组(P<0.05),LRP阳性表达者中NSCLC组药物敏感数明显低于LRP阴性表达者(P<0.05)。LRP与MMC、5-FU、VP-16、VCR均呈负相关(P<0.05或0.01)。P-gp与顺铂(CDDP)呈负相关(P<0.05)。GST-π与MTX、HCPT呈正相关(P<0.05行)。结论P-gp、MRP、LRP、GST-π的蛋白表达及共表达与体外药敏试验存在较好相关性,可作为监测肺癌细胞原发性耐药的指标。     

黄芪多糖抑制肝癌Bel-7402/5-FU耐药细胞株增殖及对耐药基因的影响

目的:研究黄芪多糖抑制肝癌Bel-7402/5-FU耐药细胞株增殖及对耐药基因的影响。方法:CCK-8法检测不同浓度黄芪多糖对肝癌Bel-7402/5-FU耐药细胞的增殖抑制率并计算IC_(50);根据药物处理方法将肝癌Bel-7402/5-FU耐药细胞分为CON组(不加药物)、APS组(IC_(50)浓度黄芪多糖处理)、5-FU组(10μg/ml 5-FU处理)、A+F组(黄芪多糖与5-FU联用),比较不同药物处理对细胞增殖、细胞周期及凋亡情况的影响。采用RT-PCR和Western blot分析不同药物处理对谷胱甘肽S-转移酶π(GST-π)和多药耐药基因1(MDR1)mRNA和蛋白质表达的影响。结果:药物处理2～7 d时,APS组和A+F组肝癌Bel-7402/5-FU耐药细胞增殖率均显著低于CON组和5-FU组(均P0.05),A+F组细胞增殖率显著低于APS组(P0.05),黄芪多糖与5-FU联用时细胞增殖抑制效果最佳。A+F组S期、G_2/M期细胞、增殖指数、GST-π和MDR1基因mRNA和蛋白质均显著低于APS组,G_0/G_1期和凋亡率均显著高于APS组(均P0.05)。结论:黄芪多糖可显著抑制肝癌Bel-7402/5-FU耐药细胞增殖,降低耐药基因GST-π和MDR1的表达,降低肝癌Bel-7402/5-FU耐药细胞对5-FU的耐药性。     

槲皮素联合survivin反义核苷酸对肝癌SMMC7721/ADM细胞MDR的逆转作用

目的 探讨槲皮素与survivin反义核苷酸(ASODN)联合应用对肝癌SMMC7721/ADM细胞多药耐药(MDR)的逆转作用.方法 选择肝癌敏感细胞株SMMC7721和MDR细胞株SMMC7721/阿霉素(ADM),观察其对四种不同化疗药物的耐药性及槲皮素、survivin反义核苷酸(ASODN)对SMMC7721/ADM细胞MDR的逆转效果.结果 槲皮素和ASODN联合时较两者单独应用时能显著降低四种化疗药物对SMMC7721/ADM细胞的半数抑制浓度(IC50) (P<0.05).槲皮素单独应用及联合ASODN时均能明显降低SMMC7721/ADM细胞的多药耐药基因1(MDR1)mRNA及p170和多药耐药相关蛋白基因(MRP)mRNA及p190的表达(P均<0.05). 结论 槲皮素与ASODN联合能明显逆转SMMC7721/ADM细胞对四种化疗药物的耐药性.槲皮素可能通过抑制MDR1 mRNA和MRP mRNA的表达使p170和p190的合成减少而发挥耐药逆转作用,ASODN不能通过该途径发挥作用.     

人大肠癌HCT-8/5-FU耐药细胞株的建立及P-gp测定

目的：建立人大肠癌多药耐药细胞株HCT-8/5- FU及并对其耐药机制进行探讨．方法：先采用较大剂量间歇诱导法进行筛选,再采用浓度梯度递增法作用,历时7mo,至HCT8细胞可长期在5-FU浓度为2．0mg/L的细胞培养液中稳定生长．电镜、HE染色观察2种细胞形态结构差异．体外细胞毒性实验观察他对5-FU ADM,DDP的耐药性．绘制亲本细胞和耐药细胞的体外生长曲线．罗丹明染色法检测其两种细胞P-gp功能表达．结果：HCT-8细胞株经7mo诱导,可在5-FU 2．0 g/L的培养液中稳定增殖,具有多药耐药性,命名为HCT-8/5-FU,该细胞株对5-FU的耐药指数为16．6,并对ADM,DDP有交叉耐药性．该细胞株体外群体倍增时间与亲本细胞差别不显著．HE染色观察耐药细胞胞体较亲本细胞大,细胞核不规则,可见双核、多形核,细胞形态不规则,呈多角形、细长形改变,可见巨核细胞．透射电镜下耐药细胞胞质内线粒体、内质网、溶酶体增多．流式细胞仪罗丹明染色法观察荧光强度曲线左移,提示耐药细胞有过度P-gp表达．结论：成功建立HCT-8/5-FU多药耐药细胞株．先采用较大剂量间歇诱导进行筛选,再采用浓度梯度递增法作用是诱导大肠癌耐药细胞株的较好方式．HCT-8/5-FU细胞株的耐药机制与P-糖蛋白表达有关．     

奥曲肽逆转肝细胞肝癌多药耐药的机制

目的 探讨生长抑素（SST）类似物奥曲肽逆转肝癌细胞多药耐药可能的机制。方法 应用MTT法分析肝癌细胞对化疗药物的敏感性；RT—PCR、流式细胞术检测肝癌细胞多药耐药基因多药耐药糖蛋白1（MDR1）、多药耐药相关蛋白2（MRP2）mRNA及其蛋白质的表达。结果 奥曲肽联合化疗药物可以显著降低化疗药物的IC50肝癌细胞有生长抑索受体2（SSTR2）、生长抑素受体3（SSTR3）、MDR1、MRP2的表达，奥曲肽可显著降低肝癌细胞表面MDR1、MRP2的表达。结论 SST可与肝癌细胞表面的SSTR结合，降低其表面MDR2、MRP2的表达，使细胞内细胞毒药物浓度增加，从而逆转肝癌细胞多药耐药。     

全反式维甲酸联合维生素D3对肺癌原代细胞化疗敏感性的影响

目的探讨全反式维甲酸(ATRA)联用维生素D3(VD3)逆转肺癌细胞多药耐药、提高肺癌细胞化疗敏感性的机制。方法将ATRA、VD3联合作用于培养后的人肺癌原代细胞,观察肺癌原代细胞对顺铂化疗的敏感性及多药耐药相关蛋白(MRP)、肺耐药蛋白(LRP)的表达水平。结果人肺癌原代细胞MRP、LRP呈高表达;ATRA及VD3作用后肺腺癌原代细胞MRP、LRP表达量明显降低,肺鳞癌MRP、LRP的表达量无明显变化;顺铂化疗的敏感性提高。结论MRP、LRP在肺癌尤其非小细胞肺癌中高表达,可反映肿瘤细胞多药耐药性;ATRA或VD3可下调肺腺癌MRP、LRP基因的表达水平,提高肺腺癌的化疗敏感性;但对肺鳞癌MRP、LRP基因表达水平无明显影响;ATRA和VD3联用有协同作用。     

Mechanaism of 5—fluorouracil required resistance in human hepatocellular carcinoma cell line Bel7402

AIM: To investigate the resistance mechanism of 5-fluorouracil (5-FU) in Bel(7402)/5-FU cells which was established in our lab by in vitro continuous stepwise exposure of human hepatocellular carcinoma (HCC) cell line Bel(7402) to 5-FU. METHODS: The expression of multidrug resistance-associated protein (MRP) and thymidylate synthase (TS) in Bel(7402) cells was detected by immonocytochemistry. The fluorescein (FLU) accumulation, an index of MRP functional activity, was determined by flow cytometry. The distribution of FLU was observed by confocal laser scanning microscope. The spectrofluorometry was used to show the intracelluar content of glutathione (GSH). Cell growth inhibition was determined by MTT assay. The activity of glutathione S-transferases (GSTs) was determined by spectrophotometry. RESULTS: A higher expression of MRP in the Bel(7402)/5-FU cells was observed by using monoclonal mouse anti-MRP antibody, MRPr-1, in comparison with Bel(7402) cells. Bel(7402)/5-FU cells also showed a significant decrease of FLU accumulation. FLU mainly accumulated in the nucleus with a high nuclear/cytoplasmic ratio in Bel(7402) cells, whereas there was no difference of FLU accumulation between the nucleus and cytoplasm in Bel(7402)/5-FU cells. The intracellular GSH content in Bel(7402)/5-FU cells was almost 3 folds higher than that in Bel(7402) cells. Addition of D, L-buthione-S, R-sulfoximine (BSO) dose-dependently reduced the GSH content in Bel(7402)/5-FU cells, however, only a weak enhancement on the cytotoxicity of 5-FU and doxorubicin (Dox) to Bel(7402)/5-FU cells was observed. Bel(7402)/5-FU cells also exhibited 29.1 % higher total GSTs activity than Bel(7402) cells. Immunocytochemical staining by using anti-TS monoclonal antibody TS 106 showed that the level of TS in Bel(7402)/5-FU cells elevated markedly as compared with Bel(7402) cells. CONCLUSION: The continuous exposure of Bel(7402) cells to 5-FU led to overexpression of TS and MRP, as well as increased intracellular GSH content and total GST activity.     

Taxotere resistance in SUIT Taxotere resistance in pancreatic carcinoma cell line SUIT 2 and its sublines

AIM: To investigate the specific mechanisms of intrinsic and acquired resistance to taxotere (TXT) in pancreatic adenocarcinoma (PAC). METHODS: MTT assay was used to detect the sensitivity of PAC cell line SUIT-2 and its sublines (S-007, S-013, S-020, S-028 and TXT selected SUIT-2 cell line, S2/TXT) to TXT. Mdr1 (P-gp), multidrug resistance associated protein (MRP), lung resistance protein (LRP) and beta-tubulin isotype gene expressions were detected by RT-PCR. The functionality of P-gp and MRP was tested using their specific blocker verapamil (Ver) and indomethacin (IMC), respectively. The transporter activity of P-gp was also confirmed by Rhodamine 123 accumulation assay. RESULTS: S-020 and S2/TXT were found to be significantly resistant to TXT(19 and 9.5-fold to their parental cell line SUIT-2, respectively). RT-PCR demonstrated strong expression of Mdr1 in these two cell lines, but weaker expression or no expression in other cells lines. MRP and LRP expressions were found in most of these cell lines. The TXT-resistance in S2-020 and S2/TXT could be reversed almost completely by Ver, but not by IMC. Flow cytometry showed that Ver increased the accumulation of Rhodamine-123 in these two cell lines. Compared with S-020 and SUIT-2, the levels of beta-tubulin isotype II, III expressions in S-2/TXT were increased remarkably. CONCLUSION: The both intrinsic and acquired TXT-related drug resistance in these PAC cell lines is mainly mediated by P-gp, but had no relationship to MRP and LRP expressions. The increases of beta-tubulin isotype II, III might be collateral changes that occur when the SUIT-2 cells are treated with TXT.     

Synergistic anticancer effect of exogenous wild-type p53 gene combined with 5-FU in human colon cancer resistant to 5-FU in vivo

AIM To investigate the anticancer effect of a recombinant adenovirus-mediated p53(r Ad-p53) combined with 5-fluorouracil(5-FU) in human colon cancer resistant to 5-FU in vivo and the mechanism of r Ad-p53 in reversal of 5-FU resistance.METHODS nude mice bearing human colon cancer SW480/5-FU(5-FU resistant) were randomly assigned to four groups(n = 25 each): control group, 5-FU group, r Ad-p53 group, and r Ad-p53 + 5-FU group. At 24 h, 48 h, 72 h, 120 h and 168 h after treatment, 5 mice were randomly selected from each group and sacrificed using an overdose of anesthetics. The tumors were removed and the protein expressions of p53, protein kinase C(PKC), permeability-glycoprotein(P-gp) and multidrug resistance-associated protein 1(MRP1)(Western blot) and apoptosis(TUNEL) were determined.RESULTS The area ratios of tumor cell apoptosis were larger in the r Ad/p53 + 5-FU group than that in the control, 5-FU and r Ad/p53 groups(P 0.05), and were larger in the r Ad/p53 group than that of the control group(P 0.05) and the 5-FU group at more than 48 h(P 0.05). The p53 expression was higher in the r Ad/p53 and the r Ad/p53 + 5-FU groups than that of the control and 5-FU groups(P 0.05), and were higher in the r Ad/p53 + 5-FU group than that of the r Ad/p53 group(P 0.05). Overexpression of PKC, P-gp and MRP1 was observed in the 5-FU and control groups. In the r Ad/p53 + 5-FU group, the expression of P-gp and MRP1 was lower that of the control and 5-FU groups(P 0.05), and the expression of PKC was lower than that of the control, 5-FU and r Ad/p53 groups at more than 48 h(P 0.05). In the r Ad/p53 group, the expression of P-gp and MRP1 was lower that of the control and 5-FU groups at more than 48 h(P 0.05), and the expression of PKC was lower than that of the control and 5-FU groups at more than 120 h(P 0.05).CONCLUSION5-FU combined with r Ad-p53 has a synergistic anticancer effect in SW480/5-FU(5-FU resistance), which contributes to reversal of 5-FU resistance.     

P-glycoprotein, lung resistance-related protein and multidrug resistance-associated protein in de novo adult acute lymphoblastic leukaemia

P-glycoprotein (P-gp), lung resistance-related protein (LRP) and multidrug resistance-associated protein (MRP) expression, and blast cell intracellular daunorubicin accumulation (IDA) were evaluated in 95 previously untreated cases of adult acute lymphoblastic leukaemia (ALL) using flow cytometry. Forty-five out of 95 (47%) patients were P-gp positive (+), 12/66 (18%) were LRP+ and 11/66 (17%) were MRP+. Eighteen out of 66 (28%) patients showed a simultaneous multidrug resistance (MDR)-related protein expression higher than controls for more than one protein, while 24/66 (36%) cases did not overexpress any protein. Twenty-one out of 24 (87%) cases overexpressing at least one MDR-related protein had a defect in accumulating daunorubicin into their blast cells, while only 4/24 (16%) cases who did not overexpress any protein had similar features. The complete remission rates were similar in MDR-positive and -negative (-) patients but relapses within 6 months were more frequent in P-gp+ cases, and therefore the disease-free survival duration was shorter in P-gp+ than in P-gp- patients (P = 0.01). The number of MRP+ and/or LRP+ cases was too small to be able to draw any conclusion on their role in affecting or predicting therapy outcome. In conclusion, P-gp overexpression associated with a defect in daunorubicin accumulation is a frequent feature in adult ALL at onset and seems to be related to poorer therapy outcome and, consequently, a shorter disease-free survival. LRP and MRP overexpression seems to be a rare event and no conclusion can be drawn on its prognostic role.     

Multidrug resistance mechanisms in chronic lymphocytic leukaemia

We evaluated the presence of P-glycoprotein (P-gp)-170, multidrug resistance protein (MRP), lung resistance protein (LRP)-56 and Bcl-2 in CD19-positive cells from 100 cases of chronic lymphocytic leukaemia (CLL). P-gp-170 was found in 73% of the CLL cases with no significant difference regarding stage or previous treatment. LRP-56 protein was homogeneously distributed with no differences for stage or treatment. MRP protein was detected at a low level of expression in 49.4% of CLL patients with no differences for stage or treatment. Bcl-2 protein was expressed at a high level in all CLL patients and higher levels were found in the advanced stage. This leads us to conclude that P-gp, MRP, LRP-56 and Bcl-2 are frequently expressed in CLL. P-gp, MRP and LRP are not correlated to stage or previous treatment. Bcl-2 is higher in advanced-stage patients. The clinical and biological significance of these zMDR mechanisms in CLL remains to be fully explained.     

Multidrug resistance reversal in human gastric carcinoma cells by neferine

AIIVI: To investigate the reversal effect of neferine on multidrug resistance in human gastric carcinoma cell line. METHODS: Cells of a human gastric cancer cells line, SGC7901, and its vincristine (VCR) -resistant variant, SGC7901/VCR, were cultivated with or without neferine and/or VCR. The cytotoxic effect of VCR was evaluated by the MTT assay. Cell apoptosis induced by VCR was determined by flow cytometry(FCM). The expression of P-glycoprotein (P-gp) and a multidrug-resistance-associated protein (MRP) in cells was examined by immunofluorescence and FCM. RESULTS: Neferine at the concentration from 2.5 μmol/L to 10 μmol/L had no cytotoxicity to SGC7901 cells, and its variant SGC7901/VCR cells. The ICso of VCR against SGC7901 and SGC7901/VCR cells was 0.059 μg/mL and 2.32 μg/mL, respectively, indicating that SGC7901/VCR cells were 39 times more resistant to VCR than its parent SGC7 901 cells. After treatment with neferine at concentrations of 2.5, 5 and 10 μmol/L, the IC50 of VCR to SGC7901/VCR cell line decreased to 0.340, 0.128 and 0.053 μg/mL, respectively,thus, increased the chemosensitivity by 6.8-, 18.1- and 43.8-fold, respectively. SGC7901/VCR cells were apoptosis resistant to VCR. Neferine (2.5, 5 and 10 μmol/L) promoted the VCR-induced apoptosis of SGC7901/VCR cells in a dosedependent manner. The expressions of P-gp and MRP were strongly positive in SGC7901/VCR cells, which were significantly down-regulated after treatment with neferine (10 μmol/L)for 24 h. CONCLUSION: Neferine reverses multidrug resistance of human gastric carcinoma SGC7901/VCR cells, which may be associated with the down-regulations of P-gp and MRP expression in SGC701/VCR cells.     

胃癌多药耐药蛋白的相互作用蛋白鉴定及分子机制

目的:研究多药耐药蛋白(multidrug resistance protein,MRP)的相互作用蛋白及其对肿瘤耐药性的影响.方法:采用免疫沉淀结合质谱方法分离鉴定MRP的相互作用蛋白,并对其中的耐药相关蛋白之一Annexin A5进行功能研究,Western blot及siRNA干扰技术分析MRP、Annexin A5蛋白表达的变化、相关性及胃癌SGC-7901细胞的耐药性变化.结果:经免疫沉淀结合质谱方法分离鉴定发现了14个MRP的相互作用蛋白,其中AnnexinA5为其中得分最高的蛋白;Westernblot检测显示耐药细胞株SGC-7901/DDP中MRP、AnnexinA5蛋白表达均高于SGC-7901和siRNA-SGC-7901/DDP,siRNA干扰AnnexinA5表达后,siRNA-SGC-7901/DDP中MRP蛋白表达下调,MRP、AnnexinA5蛋白在SGC-7901和siRNA-SGC-7901/DDP之间表达无明显差异;MTT法结果显示经siRNA干扰SGC-7901/DDP后,顺铂、5-Fu和紫杉醇作用后的IC50值明显减少,对其的敏感性分别增加了36倍、17倍和4倍.结论...     

Involvement of extracellular signal-regulated kinase／mitogenactivated protein kinase pathway in multidrug resistance induced by HBx in hepatoma cell line

AIM: To investigate the molecular mechanism of the influence of HBx protein on multidrug resistance associated genes: multidrug resistance 1 (MDR-1), multidrug related protein (MRP-1), lung resistance related protein (LRP) in hepatoma cells and the potential role of extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) pathway in this process. METHODS: A cell model stably expressing the HBx protein was established by liposome-mediated transfection of HBx gene into HepG2 cell line. The expression of multidrug resistance associated genes and proteins was detected by RT-PCR and Western blot. AnnexinV-FITC/PI assay was used to confirm the multidrug resistance (MDR) phenotype of transfected cells by fluorescence cytometry (FACS). The ERK/MAPK pathway activation was measured by Western blot through comparing the ratio of phosphorylation of ERK/MAPK to total ERK/MAPK protein. After treated with the ERK/MAPK pathway inhibitor U0126, the HBx-expressing cells were harvested. Then RT-PCR, Western blot and FACS were used to analyze the alterations in the expression of multidrug resistance associated genes and the MDR phenotype after exposure. RESULTS: Compared with the control group, the transfected cells showed a higher expression of MDR associated genes and proteins. Marked elevations in MDR-1 (64.3%), MRP-1 (87.5%) and LRP (90.8%) were observed in the transfected cells (P<0.05). RT-PCR revealed that the over-expression of MDR associated proteins was due to amplification of such genes (MDR1 2.9 fold, MRP1 1.67 fold, LRP1.95 fold). Furthermore, we found that the ERK/MAPK activity was remarkably high in the HBx-expressing cells. The activation of ERK/MAPK, as measured by the ratio of phosphorylated ERK bands normalized to the total ERK bands, was increased by 2.3-fold in HBx-transfected cells compared with cells transfected with the empty vector. After treated with the ERK/MAPK pathway inhibitor, the level of MDR associated genes and proteins in the transfected cells decreased to some extent. Compared with controls, a significant decrease in MDR-1 mRNA (53.3%), MRP-1 mRNA (59.7%) as well as LRP mRNA (56.4%) was observed in the U0126 treated transfected cells after 12 h. Western blot also demonstrated that the protein expression of these MDR associated genes slightly reduced after treated with U0126 for 12 h (MDR-1 40.1%, MRP-1 29.4%, LRP35.7%). This change was accompanied with the rise of cell apoptosis ratio confirmed by Annexin V-PI detection. The apoptosis index of U0126-treated cells increased by 1.28 fold, compared with that of transfected cells. Obviously, the MDR phenotype of these cells was obviously related with increased activities of the ERK/MAPK pathway. CONCLUSION: HBx protein might be one of the causes for the occurrence of MDR in HCC, and ERK/MAPK pathway might be involved in this change.