Inhibitor of growth 4 induces apoptosis in human lung adenocarcinoma cell line A549 via Bcl-2 family proteins and mitochondria apoptosis pathway

Objective  Inhibitor of growth 4 (ING4) is considered to be a tumor suppressor implicated in several human malignancies by tumor growth inhibition and apoptosis enhancement. In present study, the effects of ING4 on apoptosis and its mechanisms were investigated through the transduction of ING4 cDNA into lung adenocarcinoma cell line A549. Methods  The effects of ING4 on A549 apoptosis were observed by FCM analysis, TUNEL assay, and electron microscopy. Simultaneously, the effects of ING4 on the expression of several apoptosis-related proteins in cell line A549 were evaluated by Western blot analysis. Results  Both Annexin-V FITC analysis by FCM and TUNEL assay revealed more apoptotic cells in A549 cells with exogenous ING4 gene. For electron microscopy, A549 cells with exogenous ING4 gene showed typical morphological changes of apoptosis. The deregulation of Bcl-2 family proteins (Bcl-2, Bcl-xl, Bax, Bak, Bid) and the major apoptotic executioners of mitochondria pathway (Cyt-c, caspase3, PARP) were also observed. Conclusion  Our findings suggest that exogenous ING4 can enhance A549 apoptosis via regulating the expression of Bcl-2 family proteins and the activation of mitochondrial apoptotic pathway. Xiaomei Li, Qingyuan Zhang, and Limin Cai contributed equally to this work.