Downregulation of CPA4 to suppress NSCLC proliferation by inducing apoptosis and G1 arrest.

e20074 Background: Carboxypepidase A4 (CPA4) is a member of the metallocarboxypeptidase family. Previous study discovered that CPA4 may participate in cell growth and differentiation of prostate epithelial cells. Meanwhile, CPA4 is a printed gene and thought to be involved in prostate cancer aggressiveness. As is reported, CPA4 was increased in NSCLC tissues compared to normal lung tissues and high expression of CPA4 was correlated with poor prognosis of NSCLC patients. However, the role of CPA4 play in lung tumorigenesis is still unclear. Methods: We examined the mRNA and protein expression level of CPA4 via real-time PCR and immunohistochemistry in NSCLC tissues and adjacent tissues. Growth assays both in vitro and in vivo were performed to elucidate the role of CPA4 may play in lung cancer and Fluorescence Activated Cell Sorter was conducted to uncover the putative mechanism. Results: CPA4 expression was increased both in mRNA and protein levels in NSCLC tissues compared to adjacent tissues. MTT and colony formation assays showed that downregulation of CPA4 in H1299 and A549 cells inhibited lung cancer cells proliferation. We further confirmed this result by using cellomics and celligo. Depleting CPA4 also suppressed tumor growth in mice. Mechanically, we found that suppressing CPA4 expression in lung cancer cells could induce apoptosis and G1 arrest. We supposed that CPA4 expression may be associated with caspase family and it needs further studies. Conclusions: Collectively, we demonstrate that decreased CPA4 inhibits NSCLC proliferation via inducing apoptosis and G1 arrest.