CCL17 and neoplasm: Since chemokines and chemokine receptors are necessary for the recruitment of CD8+ T cells into tumors, the mRNA expression levels of various chemokines secreted by H22 tumor cells were assessed, including CCL5, CCL9, CCL17, CXCL9, CXCL10 and CXCL12, which were identified to regulate the migration of CD8+ T cells in previous studies (Berghuis et al., 2011; Zhang et al., 2020).