Inhibition of autophagy-potentiated chemosensitivity to cisplatin in laryngeal cancer Hep-2 cells.

The purposes of this study were to determine whether autophagy was involved in cisplatin (CDDP) resistance and to investigate the role of the autophagy in the regulation of chemosensitivity to CDDP in laryngeal cancer Hep-2 cells. A WST-1 assay was performed to determine cell viability and cell proliferation. Autophagy activation and proapoptotic effects were characterized using monodansylcadaverine labeling and Hoechest staining, respectively. Western blot analysis was used to detect the expression of apoptotic and autophagy-related genes. Flow cytometry was used to assess cell apoptosis ratio. Exposure to CDDP induced the aggregation of autophagosomes in the cytoplasms of Hep-2 cells and up-regulated the expression of Beclin 1 and LC3II. However, CDDP treatment could not lead to obvious inhibition of cell proliferation, which implies that the autophagy may protect CDDP-treated cells from undergoing cell death. Meanwhile, the WST-1 assay indicated that knockdown of the autophagic gene Beclin 1 sensitized Hep-2 cells to CDDP. Furthermore, CDDP-mediated apoptotic cell death was further potentiated by pretreatment with autophagy inhibitor 3-methyladenine or small interfering RNA against Beclin 1. For the definite mechanism of Beclin 1-enhancing chemosensitivity to CDDP, we found that Beclin1 augmented CDDP-induced apoptotic signaling via enhancing caspase-9 and caspase-3 activity but not caspase-8. Our results suggest that functional autophagy in response to CDDP may lead to cell survival in Hep-2 cells, whereas defective autophagy may contribute to CDDP-induced apoptosis in Hep-2 cells. Thus, modulators of autophagy may be used beneficially as adjunctive therapeutic agents during the treatment of laryngeal cancer with CDDP therapy.