A compound of formula (1): wherein X is a tyrosine residue or a methionine residue; Y and Z each are a single bond; R1 is a hydrogen atom; R2 is a hydroxy group; R3 is a hydrogen atom, alkyl group, amino group substituted alkylcarbonylamino; R4 is a hydrogen atom, alkyl group, carboxy group a group of formula (2): wherein W is an amino acid residue; m is 1 or 2; and n is an integer of 0 to 2, with the proviso that when n is 0, R3 is a hydrogen atom or an alkyl group, or a pharmaceutically acceptable salt thereof, and its use in cancer immunotherapy.