Disclosed is an immune response inducer comprising a specific polypeptide asan active ingredient. The polypeptide is isolated as a polypeptide capable ofbinding to an antibody that occurs specifically in a serum collected from a cancer-carryingliving body, by the SEREX method using a cDNA library derived from a canine testisand a serum collected from a cancer-carrying dog. The polypeptide can inducean immune response in a living body, and can also regress a tumor in a cancer-carryingliving body. Therefore, the polypeptide is particularly useful as a therapeuticand/or prophylactic agent for cancer.
