Koper et al. [55], Ding et al. [53], and Tonouchi et al. [59] report that serum CCL2 levels were decreased in patients with astrocytic brain tumors, oral squamous cell carcinoma, and gastric cancer, and Tonouchi et al. report CCL2 levels tended to decrease in accordance with disease progression and that decreased serum CCL2 levels were associated with poor survival. The gene discussed is CCL2; the disease is oral cavity squamous cell carcinoma.