• Microbiology and Biotechnology Letters
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• v.32 no.1
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• pp.72-77
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• 2004

Previously, we synthesized a novel Cyclin-dependent kinase inhibitor, MCS-5A. Also, we investigated the involvement of cell cycle regulatory events during MCS-5A-mediated apoptosis in HL-60(+p16/-p53) cells with up-regulation of p16 protein expression. In contrast, apoptosis was not observed in A549(-p16/+p53) cells. Therefore we propose that $p16^{INK4A}$ is a key enzyme for inducing apoptosis. In the present studies, we have explored the mechanism of $p16^{INK4A}$ -mediated cytotoxicity and the role of p16.sup INK4A/ overexpression in the induction of apoptosis in human tumor cells. The tumor suppressor gene $p16^{INK4A}$ is known as a cyclin-dependent kinase inhibitor (CKI) and cell cycle regulator. We expressed wild type $p16^{INK4A}$ in pcDNA3.1 vector and then transfected into non-small cell lung cancer (NSCLC) cell expressing different statue of p16$^{INK4A}$, p53 gene〔A549(-p16/+p53), H1299(-p16/-p53) and HeLa(+pl6/+p53) cell line〕. TUNEL assay (including propidium iodide staining following transfection of these cell line with pcDNA3.1-pl6) indicate that p16$^{INK4A}$-mediated cytotoxicity was associated with apoptosis. This is supported by studies demonstrating an induction of caspase 3 cleavage due to the transfection of A549, H1299 and HeLa cells with pcDNA3.1-pl6. These results suggest that p16$^{INK4A}$ has a new function of inducing apoptosis which is not related with the function of tumor suppressor gene p53.