CCL17 and urinary bladder cancer: Moreover, the blockade of CCR4 results in the reduction of regulatory T cells, while increasing the survival of canine models of bladder cancer (Maeda et al., 2019), and CCR4-CCL17/22 could serve as a chemokine gradient to chemoattract regulatory T cells to the tumor microenvironment (Ohue and Nishikawa, 2019).