PDCD1 and neoplasm: The PD-L1 expression levels on tumor cells tend to be associated with tumor progression and are predictive of unfavorable prognosis and better response to PD-1 blockade treatment, to a certain extent, in ovarian, kidney, pancreatic, and gastric cancers (Thompson et al., 2005; Wu et al., 2006; Hamanishi et al., 2007; Nomi et al., 2007; Garon et al., 2015; Gandini et al., 2016).