p53-dependent induction of WAF1 by a low-pH culture condition in human glioblastoma cells.

The effects of an acidic condition (pH 6.5) on WAF1 gene expression and p53 accumulation was investigated in human glioblastoma cells with different p53 statuses. WAF1 and p53 accumulation after treatment in acidic conditions was observed in A-172 cells carrying the wild-type p53 gene but not in T98G cells carrying the mutant p53 gene. Northern blot analysis showed that WAF1 gene activation by acidic conditions only occurred in A-172 cells. Consistent with this, activation of the binding of p53 to its specific DNA sequence by acidic stress was detected by gel mobility shift assay using p53 consensus sequence as a probe. Moreover, the increased WAF1 protein and mRNA levels that were due to acidic treatment returned to normal levels upon the return of the cells to neutral conditions, 6 h after the cells had been cultured in acidic conditions for 6 or 12 h. These findings suggest that WAF1 gene activation is inducible by acidic conditions in human glioblastoma cells, which is probably due to activation of the p53-dependent signal transduction pathway.