CCL17 and esophageal squamous cell carcinoma: Moreover, for rescue experiments, Eca109 cells were treated with CCL17 (50 ng/ml) and/or CCR4 antagonist AZD2098 (20 μM) to probe whether CCL17 could influence the malignant behaviors including migration, invasion and stemness of ESCC cells via activating CCR4/ERK/PD-L1 pathway.