Ubiquitin-specific protease 39 is overexpressed in human lung cancer and promotes tumor cell proliferation in vitro.

Lung cancer is the most frequent cancer in the world. Previous studies have shown that ubiquitin-specific protease 39 (USP39) is upregulated in several cancers and associated with tumor malignant characters. However, the effects of USP39 in lung cancer have not been well understood. In the present study, we found USP39 was generally expressed higher in human lung cancer tissues than in normal tissues by Oncomine database mining, qRT-PCR, and western blot assay. Knockdown of USP39 expression markedly reduced the proliferative and colony-forming ability of lung cancer cell lines 95D and A549. Flow cytometric analysis showed that USP39 knockdown induced cell cycle arrest at G2/M phase and enhanced cell apoptosis in 95D cells. Moreover, depletion of USP39 blocked activation of Akt, mTOR, p53, and PARP signaling pathways. Taken together, our study indicates that USP39 may be functionally involved in lung cancer growth and act as a potential molecular target for human lung cancer diagnosis and treatment.