Significant difference in p53 and p21 protein immunoreactivity in HPV 16 positive and HPV negative breast carcinomas

Human papillomavirus (HPV) 16 has previously been found in 19/41 breast car cinomas (46%) in women with a history of HPV 16 positive CIN III lesions. T here was no significant difference in distribution of histological subtypes , mean or median tumour diameter or number of regional lymph node metastase s in the HPV positive and HPV negative breast carcinoma groups. P53, p21 an d c-erbB-2 proteins were analysed by immunohistochemistry in the HPV 16 pos itive and HPV negative breast carcinomas. There was a significant differenc e in p53 and p21 protein immunoreactivity between HPV 16 positive and HPV n egative breast carcinomas (p = 0.0091 and p = 0.0040). with a significant l ess detectable p53 and p21 protein immunoreactivity in the HPV 16 positive cases. There was also a significant difference in the coexpression of p53/p 21 between the HPV 16 positive and HPV 16 negative breast carcinomas (p = 0 .002). No significant difference in immunostaining for c-erbB-2 protein in the two groups was found (p = 0.15), or for the coexpression of p53/c-erbB- 2 (p = 0.19). The significantly lower expression of p53 and p21 proteins in HPV 16 positive than in HPV 16 negative breast carcinomas supports the hyp othesis of inactivation and degradation of wild-type p53 proteins by HPV 16 E6 and that p53 mutation is not necessary for transformation in the HPV 16 positive cases.