The concept that the colon tumor-promoting effect of CCL5 crucially depends on the involvement of the adaptive immune system was further supported by the observation that the inoculation of CCL5-deficient colon tumor cells into immunocompetent recipient mice, but not into B and T cell-lacking Rag1-deficient animals, resulted in impaired tumor growth [51]. This evidence concerns the gene CCL5 and colonic neoplasm.