Immune response to p53 and HPV-16 E6 proteins in patients with cervical cancer

To investigate whether p53 autoantibodies could be found in the sera of patients with cervical cancers, we have therefore studied by radioimmunoprecipitation assay, using in vitro translated p53 protein, sera from such patients. The sere-positive patients for p53 were also evaluated in relation to immunoreactivity to p53 antigens by immunohistochemistry, for genomic alterations of p53 by PCR-SSCP, and for the presence of HPV-16/18 DNAs in the cervical cancer cells. In immunohistochemistry, expression of p53 protein was seen in 47% (14/30) of HPV-16 or -18 positive cervical cancers and 13% (2/15) of HPV-16/18 negative cervical cancers (P < 0.01). Eight out of 12 control ovarian cancers (67%) showed positive p53 staining in most tumor cells. Cases of cervical cancer and ovarian cancer, which were positively expressed p53 protein in the tissue or the sera, were studied for genomic alterations in exons 5-8 of the p53 by PCR-SSCP. Serum antibodies to in vitro translated p53 protein were found in two cases from 63 cervical cancers; one patient was stage IIA, having HPV-16 DNA in a tumor of squamous cell type, and another patient was stage IIIB, having HPV-16 and -18 DNAs in an adenocarcinoma. The cervical cancer tissues from the two sere-positive patients were also positive for p53 immunostaining. None of the cervical cancer samples showed aberrant bands, but three of eight cases of ovarian cancer which were positive for p53 protein by immunostaining were shown to have aberrant bands by PCR-SSCP. In contrast to ovarian cancers, alteration of p53 tumor suppressor gene and positive antibody response to p53 protein seem to be rare events in patients with cervical cancer.