YKL-40 is also suggested to contribute to an immunosuppressive tumor microenvironment by inhibiting the function of cytotoxic T and natural killer (NK) lymphocytes (6–8), stimulating programmed death-ligand 1 (PD-L1) expression (9), and regulating macrophage polarization toward an anti-inflammatory phenotype (10). The gene discussed is CD274; the disease is neoplasm.