Induction of apoptosis in p16(INK4A) mutant cell lines by adenovirus-mediated overexpression of p16(INK4A) protein

The tumor suppressor gene p16(INK4A) is a cyclin-dependent kinase inhibitor (CDK1) and an important cell cycle regulator. We have previously construct ed a recombinant adenovirus which expresses p16 (Adp16) and shown that infe ction in a variety of human tumor cell lines with this recombinant virus re sults in high levels of p16(INK4A) protein expression resulting in cell cyc le arrest and loss of cyclin-cdk activity. Furthermore, adenoviral-mediated overexpression of wild-type p16(INK4A) is more toxic in cancer cells which express mutant forms of p16(INK4A) compared to cancer cell lines containin g endogenous wild-type p16. TUNEL assay and DAPI staining following infecti on of MDA-MB 231 breast cancer cells with Adp16 indicate that p16(INK4A)-me diated cytotoxicity was associated with apoptosis. This is supported by stu dies demonstrating a decrease in cpp32 and cyclinB1 protein levels and indu ction of poly (ADP-ribose) polymerase (PARP) cleavage following infection o f MDA-MB-231 cells with Adp16. These results suggest that gene therapy usin g Adp16 may be a promising treatment option for human cancers containing al terations in p16 expression.