Truncation of inhibitor of growth family protein 5 effectively induces senescence, but not apoptosis in human tongue squamous cell carcinoma cell line.

In these studies, inhibitor of growth protein 5 (ING5) and various fragments of it were overexpressed in the human tongue squamous cell carcinoma cell line, HSC-3. The roles of ING5 in HSC-3 cells were then identified in vitro. Our results indicate that intact ING5 can inhibit proliferation and induce apoptosis in HSC-3 cells. Moreover, two truncated fragments of ING5 (aa 1-184 and aa 107-226) can induce cellular senescence. To analyze the signaling pathway involved, western blotting was performed. In these assays, two truncated fragments of ING5 were found to inhibit the cyclin E and CDK2 expression. These results are consistent with the S phase arrest observed with the overexpression of truncated ING5. However, the mechanisms of ING5-induced cellular senescence remain unclear, and extensive investigations are required in future studies.