A natural or synthetic peptide derived from the Ras protein with potential use in cancer immunotherapy. Ras protein regulates a number of signalling molecules by translocating them to the plasma membrane for activation and may serve as a branchpoint in signal transduction because it orchestrates the activity of multiple signalling pathways to regulate diverse cellular functions. Ras-12 Ala is a mutated form of the wild-type Ras protein in which the amino acid glycine at codon 12 is replaced with alanine. Vaccination with mutated Ras proteins or peptides may stimulate cytotoxic host immune responses to tumor cells that express similarly mutated Ras proteins. (NCI04) [ ]