title: Chloroquine enhances the cytotoxicity of topotecan by inhibiting autophagy in lung cancer cells.
abstract: Although the anti-malaria drug chloroquine (CQ) has been shown to enhance chemotherapy and radiation sensitivity in clinical trials, the potential mechanisms underlying this enhancement are still unclear. Here, we examined the relevant mechanisms by which the multipotent CQ enhanced the cytotoxicity of topotecan (TPT). The lung cancer cell line A549 was treated with TPT alone or TPT combined with CQ at non-cytotoxic concentrations. Cell viability was assessed using the MTT assay. The percentage of apoptotic cells and the presence of a side population of cells were both determined by flow cytometry. Autophagy and the expression of Bcl-2 family proteins were examined by Western blotting. The accumulation of YFP-LC3 dots and the formation of acidic vesicular organelles were examined by confocal microscopy. CQ sensitized A549 cells to TPT and enhanced TPT-induced apoptosis in a Bcl-2 family protein-independent fashion. CQ inhibited TPT-induced autophagy, which modified the cytotoxicity of TPT. However, CQ failed to modify the transfer of TPT across the cytoplasmic membrane and did not increase lysosomal permeability. This study showed that CQ at non-cytotoxic concentrations potentiated the cytotoxicity of TPT by interfering with autophagy, implying that CQ has significant potential as a chemotherapeutic enhancer.
authors.affiliation: State Key Laboratory of Oncology in South China, Guangdong, People's Republic of China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Wang
authors.forename: Rui-Qing
authors.initials: RQ
authors.lastname: Peng
authors.forename: Dan-Dan
authors.initials: DD
authors.lastname: Li
authors.forename: Ya
authors.initials: Y
authors.lastname: Ding
authors.forename: Xiao-Qi
authors.initials: XQ
authors.lastname: Wu
authors.forename: Yi-Xin
authors.initials: YX
authors.lastname: Zeng
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Zhu
authors.forename: Xiao-Shi
authors.initials: XS
authors.lastname: Zhang
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects*; D000072224:Bcl-2-Like Protein 11; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002738:Chloroquine / Q000494:pharmacology*; D004357:Drug Synergism; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology*; D008565:Membrane Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D059004:Topoisomerase I Inhibitors / Q000494:pharmacology; D019772:Topotecan / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C494826:BAX protein, human; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D059004:Topoisomerase I Inhibitors; D051028:bcl-2-Associated X Protein; D019772:Topotecan; D002738:Chloroquine