中文摘要：

目的：探讨靶向溶酶体药物氯喹（chloroquine,CQ）联合拓扑替康（topotecan,TPT）对结肠癌细胞的增殖抑制作用及其可能的机制。方法：应用MTT法检测TPT对结肠癌SW480、SW620、Colo205和LoVo细胞的抑制率,以及CQ和TPT联合应用对LoVo细胞的增殖抑制作用。CQ或TPT作用于LoVo细胞后,免疫印迹法检测自噬标志蛋白LC3、P62及自噬相关蛋白Beclin1的表达;共聚焦显微镜下观察细胞质内YFP-LC3的点状聚集;采用小干扰RNA（small interfering RNA,siRNA）沉默Beclin1基因表达后,应用TPT作用LoVo细胞,锥虫蓝染色法计数细胞死亡率。结果：低浓度的CQ能够增强TPT对LoVo细胞的增殖抑制作用;CQ通过干扰自噬溶酶体功能阻断TPT诱导的自噬;通过siRNA沉默自噬相关基因Beclin1,也可增强TPT对LoVo细胞的杀伤作用。结论：CQ能够增强TPT对结肠癌细胞的增殖抑制作用,其机制可能与其阻断自噬有关。预测CQ在结肠癌治疗方面有望成为一种新型的化疗药物增敏剂。

英文摘要：

Objective：The lysosomotropic drug chloroquine（CQ） has been shown in clinical trials to enhance chemotherapy and radiation sensitivity.This study is designed to examine the inhibitory effects of CQ combined with topotecan（TPT）on the proliferation of colon cancer cells and elucidate the potential mechanisms.Methods：Colon cancer SW480,SW620,and LoVo cells were treated with TPT alone or TPT combined with CQ at non cytotoxic concentrations.Cell viability was examined using MTT assay.Expressions of autophagy-related proteins LC3,P62,and Beclin1 in LoVo cells were examined by Western blotting after CQ or TPT treatment,and the intracellular accumulation of YFP-LC3 dots was examined by confocal microscopy.After Beclin1 gene was silenced by small interfering RNA（siRNA） in LoVo cells,the death rate was evaluated by Trypan blue staining after TPT treatment.Results：CQ at low concentrations enhanced the inhibitory effects of TPT on the proliferation of LoVo cells.CQ blocked TPT-induced autophagy by interffering the function of autophagic lysosome.Silencing autophagy-related gene Beclin1 by siRNA also enhanced the cytotoxicity of TPT.Conclusion：CQ potentiated the cytotoxicity of TPT on colon cancer cells.The mechanism may be related with blockade of autophagy induced by TPT at non cytotoxic concentration.This implies that CQ has significant potential to be a novel chemotherapeutic enhancer for colon cancer therapy.