CCL17 and breast cancer: For this reason, chemokines such as CCL1/I-309 (in breast cancer) [121,122], CCL17/TARC, CCL22/MDC (in gastric cancer and hepatocellular carcinoma) [123,124], and CCL28/MEC (in hepatocellular carcinoma) [125] cause Treg recruitment into the tumor niche.