Mutant oncopeptide immunization induces CTL specifically lysing tumor cells endogenously expressing the corresponding intact mutant p53.

The p53 nuclear oncoprotein frequently contains somatically acquired missense mutations and is often overexpressed in cancer cells. It is now known that nuclear and cytosolic proteins are processed into peptides and these can be transported into the endoplasmic reticulum and presented on the cell surface with class I MHC. We have previously shown that after treatment with interferon gamma (IFN-gamma), BALB/c 3T3 fibroblasts transfected with mutant p53 (135 C to Y) can be specifically lysed by mutant peptide-induced CTL. Here we show that P815 mastocytomas are effectively lysed by peptide stimulated CTL without treatment of IFN-gamma in vitro.