Expression of p21 in non small cell lung cancer relationship with PCNA

The first cyclin dependent kinase inhibitor to be discovered was the p21 cd k interacting protein (a.k.a., WAF1, Cip1, CAP20, Sdi1, mda6). p21 expressi on may or. may not be dependent on p53. This pathway also inhibits DNA repl ication by merit of p21's interaction with PCNA, but it has also been shown that this same inhibitory interaction with p21 does nor affect PCNA DNA re pair abilities. We assessed the immunohistochemical expression of p21 protein in 60 curativ e surgical resected non small cell lung cancers I elating it to the express ion of PCNA to clarify the contribution of the p21/PCNA pathway to the deve lopment of NSCLC. We did not find any relationship between PCNA and p21 expression. This last result may indicate that the mechanism by which PCNA controls the DNA repa ir is the most important activity of this protein during lung cancer progre ssion and development, compared to its contribution to cell proliferation. In fact, this last event is strongly counteracted by p21 expression, which in this last case works as an inhibitor of PCNA expression. In conclusion this study highlighted the important role of the p21/PCNA pat hway in lung carcinogenesis, pointing out the contribution of PCNA to the r esponse to lung aggression and nor only it's role as a proliferation index. Therefore, these results offer a background to further study to evaluate p otential novel therapeutic approaches to lung cancel treatment.