Restoration by glycerol of p53-dependent apoptosis in cells bearing the mutant p53 gene.

PURPOSE: Effective heat-induced cell death in cultured cells bearing a mutant p53 (mp53) gene was sought by glycerol treatment which led to conformational change from mp53 to wild-type p53 (wtp53) in p53-null murine fibroblasts transfected with mp53. MATERIALS AND METHODS: Heat sensitivity was measured using a colony-forming assay. For heat-induced apoptosis, gel electrophoresis was applied to detect DNA fragmentation and Hoechst33342 staining for apoptotic bodies. Glycerol (0.6 M) was applied to the cultured cells 48 h before heating at 44 degrees C in a water bath. RESULTS: Wtp53 transfectants (MT158/wtp53-1) were sensitive to heat stress compared with mp53 transfectants (MT158/mp53-2 cells), and the combined treatment with glycerol enhanced cell killing only in the MT158/mp53-2 cells. After glycerol pretreatment for 48 h, the subsequent heat treatment enhanced DNA fragmentation and apoptosis in MT158/mp53-2 cells, while DNA fragmentation and apoptotic bodies were not enhanced with heat treatment alone in these cells. In contrast, DNA fragmentation or apoptotic bodies were clearly observed in MT158/wtp53-1 cells 3-24h after heat treatment. Treatment with glycerol alone did not induce apoptosis in the transfectants. CONCLUSIONS: Glycerol appears to function as a chemical chaperone that restores mp53 to wtp53 function.