PDCD1 and neoplasm: Indeed, scientists found that mutated BRAF, a gene responsible for the regulation of IL-a and -b transcription in tumor cells, induced the activation of CAFs in melanoma, which resulted in the enhanced expression of CAF-derived programmed death 1 (PD-1) ligands such as programmed death-ligand 1 (PD-L1), PD-L2 and cyclooxygenase 2 (COX-2).