Induction of expression of MHC-class-II antigen on human thyroid carcinoma by wild-type p53

Mutation of the tumor-suppressor gene p53 is involved in carcinogenetics. We investigated the role of p53 in the induction of anti-tumor immune responses by establishing a thyroid carcinoma cell line (1F3) prepared by transfection of wild-type human p53 gene into a p53-deficient cell line (FRO). Our results showed for the first time the involvement of p53 in the induction of anti-tumor immune responses, as demonstrated by: (i) expression of the major-histocompatibility-complex(MHC)-class-II antigen on 1F3, but not FRO; (ii) mRNA of class-II gene was expressed both in 1F3 and in FRO, but was stable at post-transcriptional level in FRO, which restrained protein synthesis; (iii) 1F3 induced MHC-class-II-specific CD4+ cytotoxic-T-cell activity through allo-antigen presentation and co-stimulation. Although our novel results are limited to the wild-type-p53-expressing clone from a p53-deficient cell line, we suggest that the absence of p53 in carcinoma cells may reduce the induction of CD4+ cytotoxic-T-cell activity against carcinoma cells by diminishing the expression of class-II antigen.