CCL2 and esophageal squamous cell carcinoma: Several studies have reported that increased expression of CCL2 in tumor tissue is associated with advanced tumor stage and worse prognosis: These studies include patients with breast cancer [65–68], prostate cancer [69, 70], gastric cancer [71], colorectal cancer [72, 73], esophageal squamous cell carcinoma [74], head and neck squamous cell carcinoma [75], and glial tumors [47].