There is disclosed a peptide suitable for eliciting an immune response. The peptide corresponds to a fragment of the RAS protein, and comprises a region of 8 amino acids which includes a mutated position of the RAS protein. Said region has at least 6 amino acid residues, other than the mutated position, which are identical to the corresponding region of the RAS protein. The peptide has a point mutation at the amino acid corresponding to the mutated position, and the mutated position is position 146 or 117 of the RAS protein.
