CCR4 and colorectal cancer: CCR4 is expressed in T-cell leukemia [51], non-lymphoid solid tumors, such as breast cancer, lung cancer, colorectal cancer, gastric and hepatocellular carcinoma [42, 43, 52-56], where it may contribute to the proliferation of tumor cells and chemotaxis of regulatory T cells [43, 46, 53, 57].