Programmed cell death 4 overexpression enhances sensitivity to cisplatin via the JNK/c-Jun signaling pathway in bladder cancer

Abstract

The aim of the present study was to evaluate the effects of programmed cell death 4 (PDCD4) on cell proliferation and apoptosis, and to elucidate the potential role of the Jun N-terminal kinase (JNK)/c-Jun pathway in human bladder cancer (BCa) cells. Mixed BCa cells were transfected with plasmids containing PDCD4 (PDCD4-pcDNA3). The sensitivity to cisplatin was analyzed using cell viability, invasion/migration, apoptosis, flow cytometry, wound healing and Transwell assays at different transfection times. Furthermore, epithelial-to-mesenchymal transition (EMT) markers were detected by immunofluorescence staining, and the protein expression of c-Jun, and phosphorylated Jun N-terminal kinase (p-JNK) and c-Jun (p-c-Jun, Ser-73) were also tested using western blotting. It was observed that BCa cell proliferation and invasion and tumor growth were significantly inhibited, whereas apoptosis was enhanced in PDCD4-transfected cells treated with cisplatin compared with controls. Moreover, the western blotting and immunofluorescence results demonstrated that PDCD4 upregulated the expression of epithelial cell markers, but downregulated the expression of mesenchymal cell markers. Furthermore, overexpression of PDCD4 reduced the protein levels of p-JNK and p-c-Jun. Taken together, the findings of the present study indicate that PDCD4 enhances the sensitivity of BCa cells to cisplatin, partially via regulation of the JNK/c-Jun pathway, and reverses EMT. In conclusion, the results of the present study suggested that PDCD4, a nuclear/cytoplasmic shuttling protein with multiple functions, plays an important role in the development and progression of human BCa.