CXCR4 and neoplasm: Consistent with the diurnal expression pattern of CXCR4 protein on tumor‐infiltrated CD8+ T cells, CXCL12‐induced migration of tumor‐infiltrated CD8+ T cells was enhanced at ZT18 (p < .01), whereas no significant time‐dependent migration activity was observed in CD8+ T cells prepared from the spleen (Figure 1C).