Nelfinavir restricts A549 cell growth by inhibiting STAT3 signaling

OBJECTIVE: To investigate the anticancer effect of nelfinavir (NFV) on human A549 cells. METHODS: The inhibitory effects of NFV on the proliferation of human A549 cells were assessed using a MTT assay. Apoptotic cells were observed by fluorescence microscopy following Hoechst 33342 staining. Apoptosis of A549 cells was assessed using Annexin-V/propidium iodide staining and flow cytometry. Expression levels of signal transducer and activator of transcription 3 (STAT3) and p-STAT3 were measured by western blotting. STAT3 RNA silencing was used to investigate the pro-apoptotic mechanism of NFV in A549 cells. RESULTS: NFV dose-dependently suppressed proliferation of human A549 cells and induced significant apoptosis. Western blotting showed that the antitumor function of NFV might be mediated by STAT3 inhibition. A549 cell apoptosis in response to 20 µM NFV was significantly increased following STAT3 silencing. NFV significantly impeded the expression of the anti-apoptotic proteins Bcl-xL and Bcl-2, by increased the expression of the pro-apoptotic protein Cle-PARP. CONCLUSIONS: Our findings highlight STAT3 as a promising therapeutic target. NFV is a novel anti-cancer drug for the treatment of non-small-cell lung cancer.