Cytotoxic susceptibility and defective MHC class I expression do not correlate with mutation of p53 in human carcinomas.

Twenty-nine samples of ex vivo ovarian and lung carcinomas were investigated for the relationship between the presence of mutated protein 53 (mp53) and cytotoxic susceptibility. Unaltered expression of MHC class I alleles was required for the cytotoxic susceptibility of tumour cells to the autologous ex vivo blood lymphocytes, i.e. all 4 sensitive tumours belonged to the group of 11 tumours without defect in MHC class I expression. In contrast, the susceptibility did not correlate with the presence of mp53, i.e. cases with mp53 were randomly distributed between the sensitive and resistant tumours (2/4 and 10/17 respectively). There was no correlation either between the p53 mutation and down-regulation of MHC class I alleles. The results suggest that in these tumours the mutated p53 is not the source of immunogenic peptides and that the lack of recognition of the tumours with mp53 is not caused by a defect in the expression of MHC class I molecules.