Serum ObR was also positively correlated with serum cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), tumor necrosis factor α (TNF-α), programmed death protein-1 (PD-1), and programmed death ligand-1 (PD-L1), while showing an inverse correlation with ObR expression in tumor tissues [32]. Here, TNF is linked to neoplasm.