On the other hand, in case of APN KO mice, EL-4 tumor growth in old APN KO mice was more retarded than in young APN KO mice (Fig. 8E) and CD8+ T cells per tumor weight dramatically increased in old-aged APN KO mice compared with young-aged APN KO mice (Fig. 8G). The gene discussed is ANPEP; the disease is neoplasm.