Lack of susceptibility of heterozygous p53-knockout CBA and CIEA mice to phenolphthalein in a 6-month carcinogenicity study.

Abstract Phenolphthalein has carcinogenic activity, causing malignant lymphomas in B6C3F1 mice at a dietary dose of 3000 ppm in a 2-year carcinogenicity study and in female heterozygous p53-knockout TSG mice (C57BL/6 background) at the same dose in a 6-month study. To examine whether carcinogenic potential of phenolphthalein can be detected in other p53-knockout mouse [p53 (+/−)] strains such as p53 (+/−) CBA mice or p53 (+/−) CIEA mice (C57BL/6 background) and their littermates, they were given a diet containing 0, 6000 or 12 000 ppm for 6 months. Unequivocal induction of neoplastic lesions was not apparent, suggesting that p53 (+/−) CBA mice and p53 (+/−) CIEA mice are resistant to the induction of malignant lymphomas by the treatment of phenolphthalein.