Transfection of p53-knockout mouse fibroblasts with wild-type p53 increases the thermosensitivity and stimulates apoptosis induced by heat stress

Purpose: The relationship between p53 functions and cellular thermosensitivity was evaluated using murine fibroblasts transfected with either wild-type p53 or mutated p53, or those with a null p53 genotype. Methods and Materials: Cellular thermosensitivity was determined using the clonogenic assay. Cell cycle distribution was assayed by determining DNA content using flow cytometry, Apoptosis was analyzed by detection of both apoptotic bodies and DNA fragmentation, Results: Stable transfectant with either wild-type p53 or mutated p53 was established, The transfectants with wild-type p53 were more thermosensitive than either those with a null p53 or with mutated p53, Although heat-induced G(1) cell cycle arrest was substantially observed in all transfectants, wild-type p53 enhanced and prolonged the G(1) arrest; furthermore, wild-type p53 stimulated the induction of apoptosis by heat stress, whereas mutated p53 delayed it extremely. Conclusion: The p53 gene is a factor for determining cellular thermosensitivity and wild-type p53 contributes to thermosensitization resulting in enhancement of heat-induced apoptosis. (C) 1997 Elsevier Science Inc.