Overexpression of the wild-type p53 gene inhibits NF-kappa B activity and synergizes with aspirin to induce apoptosis in human colon cancer cells

The tumor suppressor gene p53 is a potent transcriptional regulator of gene s which are involved in many cellular activities including cell cycle arres t, apoptosis, and angiogenesis, Recent studies have demonstrated that the a ctivation of the transcriptional factor nuclear factor kappa B (NF-kappa B) plays an essential role in preventing apoptotic cell death. In this study, to better understand the mechanism reponsible for the p53-mediated apoptos is, the effect of wild-type p53 (wt-p53) gene transfer on nuclear expressio n of NF-kappa B was determined in human colon cancer cell lines, A Western blot analysis of nuclear extracts demonstrated that NF-kappa B protein leve ls in the nuclei were suppressed by the transient expression of the wt-p53 in a dose-dependent manner. Transduced wt-p53 expression increased the cyto plasmic expression of I kappa B alpha as well as its binding ability to NF- kappa B, thus markedly reducing the amount of NF-kappa B that translocated to the nucleus, The decrease in nuclear NF-kappa B protein correlated with the decreased NF-kappa B constitutive activity measured by electrophoretic mobility shift assay. Furthermore, parental cells transfected with NF-kappa B were better protected from cell death induced by the wt-p53 gene transfe r. We also found that the wt-p53 gene transfer was synergistic with aspirin (acetylsalicylic acid) in inhibiting NF-kappa B constitutive activity, res ulting in enhanced apoptotic cell death. These results suggest that the inh ibition of NF-kappa B activity is a plausible mechanism for apoptosis induc ed by the wt-p53 gene transfer in human colon cancer cells and that anti-NF -kappa B reagent aspirin could make these cells more susceptible to apoptos is.