Combination treatment of FTY720 and cisplatin exhibits enhanced antitumour effects on cisplatin-resistant non-small lung cancer cells

A major common medical treatment for lung carcinoma is cisplatin (DDP)-based therapy. However, the development or existence of chemoresistance frequently blocks its effectiveness. Currently, autophagy is recognised as a potential anticancer strategy, although there is controversy over its role in the development of cancer. In lung carcinoma, no studies of autophagy induced by FTY720, a sphingosine 1-phosphate analog and a novel immunosuppressant drug, have been published, while apoptosis has been shown to be induced by FTY720 in several cancer cell lines. We evaluated the effects of FTY720 on autophagy in A549 cells and studied the related mechanisms of cell autophagy and apoptosis in non-small cell lung carcinoma, including both DDP-resistant and -sensitive cells. The results revealed that FTY720 inhibited the growth and induced apoptosis in the A549/DDP cells in a time- and dose-dependent manner and the combination of FTY720 and DDP further enhanced apoptosis in these cells as determined by CCK-8 assay, western blotting and flow cytometry. Compared with the sensitive cell line A549, DDP-resistant A549/DDP cells showed a substantial increase in baseline autophagy as determined by increased LC puncta, and expression of LC3-I, LC3-II and Atg7 expression. DDP-induced apoptotic cell death was enhanced by the blockade of either siRNA-mediated knockdown of Atg7 genetic expression or a pharmacological inhibitor (3-MA). Moreover, the combination of FTY720 and DDP showed enhanced antitumour activity in vivo in lung cancer-bearing mice. Immunohistochemistry showed that the mice with lung carcinoma treated with FTY720 and DDP showed decreased expression of Atg7 and Ki67. Compared with monotherapy in vivo and in vitro, FTY720 in combination with DDP inhibited A549 cell growth more effectively. and these findings also show the influence of FTY720 in the induction of autophagy. Overall, the results indicated that FTY720 in combination with a DDP-based regime could enhance the effectiveness of lung carcinoma treatment.