WAF1 expression is independent of p53 gene alterations and protein expression in human lung cancer cells

Abstract

Accumulation of wild-type p53 protein arrests cells primarily at G(1)-S. This arrest is characterized by accumulation of the cyclin-dependent kinase inhibitor p21 (WAF1/CIP1) protein. Since the WAF1 gene is itself a target of p53, we investigated p53 gene expression to understand the mechanism 3 of p21 regulation in cellular transformation in human non-small cell lung cancer lines and tumor tissues. Northern and Western blot analyses in cell lines carrying wild-type or mutated p53 showed that WAFI mRNA and protein expression varied among different cell lines. WAFI expression was not directly correlated with the p53 status of the cells. WAFI was also expressed at high levels in the absence of p53 expression in a p53-deleted cell line (H358). Abrogation of p53 protein in H226b (wild-type p53) and H322 (mutated p53) cell lines by antisense RNA reduced WAFI expression in both lines, indicating that mutations in the p53 gene may not necessarily abrogate p53-mediated regulation of WAFI expression. Fourteen primary lung tumors were analyzed for p53 status by SSCP analysis and DNA sequencing. Eight of 14 lung tumor tissues examined contained p53 mutations. Six of 14 contained wildtype p53. Enhanced p21 expression was detected in two lung tumors containing p53 mutations by immunohistochemistry. Together, these data indicate that WAFI expression is independent of p53 gene alterations and protein expression in non-small cell lung tumor cells.