A Possible Correlation between the Status of Functional p53 and p21^(CIP1) Gene Expression in Human Hepatoma Cell Lines

Abstract

Expression of p21CIP1 gene has been known to be regulated by p53. We have examined whether basal expression of p21CIPI is directly correlated to the status of p53 gene expression in seven human hepatoma cell lines. Six hepatoma cell lines except Hep3B expressed significant amount of p53 and Rb transcripts. However, only three of the six cell lines(HepG2, SK-HEP-1, HT-17) showed detectable basal expression of p21CIP1transcripts, whereas three other Huh cell lines(Huhl, 4 and 7) originated from Japan did not. Neither p2lcIP´ nor p53 transcripts were observed in the Hep3B cell line. There was a considerable correlation between the status of functional p53 and p21cm gene expression in these hepatoma cells, since loss of p21CIP1gene expression was observed in the Huh7 cells which have mutated p53 and in the Huhl and Huh4 cells which have HBV containing HBX gene. Treatment of HepG2 hepatoma cells with 25 nM testosterone resulted in higher mitogenic activities by the 3H-thymidine incorporation assay. However, expression of p21"" gene did not seem to be involved in mitogenic enhancement by testosterone in these cells.