自噬对大肠癌LoVo/Adr细胞多药耐药性的影响

Effects of autophagy on multidrug resistance of drug resistant LoVo/Adr cells of colon carcinoma

目的探讨大肠癌耐药LoVo/Adr细胞自噬状态对多药耐药(MDR)的影响。方法体外培养LoVo/Adr细胞,应用透射电镜观察细胞自噬体形成情况,采用MDC荧光染色及流式细胞术定量分析自噬率,MTT法测定细胞对阿霉素(ADR)的半数抑制浓度(IC50),RT-PCR检测MDR1基因的mRNA水平,Western blotting检测P糖蛋白(P-gp)表达水平。结果 LoVo/Adr细胞中可见散在自噬体或点状绿色荧光分布,自噬率为3.1%±0.5%;ADR和雷帕霉素(RAPA)单独作用时,自噬体明显增多,自噬率分别为33.6%±5.1%和45.2%±6.1%(P<0.05),ADR和RAPA联合作用时可见大量自噬体形成,自噬率为76.2%±7.4%,显著高于二者单独作用时(P<0.05);LoVo/Adr细胞对ADR的IC50为3.05±0.52mg/L,RAPA作用后IC50降至1.12±0.21mg/L(P<0.01),RAPA具有逆转耐药的作用,逆转倍率为2.26倍;LoVo/Adr细胞MDR1 mRNA和P-gp蛋白呈高表达,在RAPA作用下,MDR1 mRNA表达量由1.42±0.31降至0.54±0.20(P<0.05),P-gp蛋白表达量由0.67±0.14降至0.15±0.08(P<0.01),RAPA显著下调了MDR1 mRNA及蛋白的表达。结论多药耐药的LoVo/Adr细胞呈低自噬状态,RAPA可通过提高细胞的自噬活性而逆转MDR,逆转途径可能与促进细胞自噬性死亡和下调MDR1基因的表达有关。

Objective To observe the effects of autophagy on multidrug resistance （MDR） of drug resistant LoVo/Adr cells of colon carcinoma. Methods The formation of autophagosomes was monitored with transmission electron microscopy, and autophagy rate was measured with the aid of MDC staining and flow cytometry. IC50 value of adriamycin （ADR） on colon carcinoma cells was detected by MTT assay. The mRNA level of MDR1 gene was measured by RT-PCR, and P-gp protein expression was detected by Western blotting. Results The sporadic autophagosomes or green epoptic dots were found to distribute in LoVo/ Adr cells with an autophagy rate of 3.1% ± 0.5%. A large number of autophagosomes were seen after being treated with ADR or rapamycin （PAPA） with the autophagy rates of 33.6% ± 5.1% and 45.2% ± 6.1%, respectively （P〈0.05）. After being treated with ADR combining PAPA, autophagosomes appeared abundantly with an autophagy rate of 76.2% ± 7.4%, which was significantly higher than that when treated with ADR or RAPA alone （P〈0.05）. The IC50 value of LoVo/Adr cells on ADR was 3.05 ± 0.52mg/L, which decreased to 1.12 ± 0.21mg/L after being treated with RAPA （P〈0.01）. RAPA could reverse MDR with a reversal ratio of 2.26. High expression of mRNA and protein of MDR1 gene were observed in LoVo/Adr cells. When treated with RAPA, the expression of MDR1 mRNA decreased from 1.42± 0.31 to 0.54 ± 0.20 （P〈0.05）, and the expression of P-gp protein also decreased significantly from 0.67± 0.14 to 0.15 ± 0.08 （P〈0.01）. Conclusion MDR LoVo/Adr cell shows a low autophagic activity, and RAPA can reverse MDR by increasing autophagy activity. The reversal path might be related with the increase of cell autophagic death and the decrease in MDR1 gene expression in LoVo/Adr ceils.