PDCD1 and neoplasm: Regarding PD-1/L-1-based immunotherapy, work from Arlene Sharpe, Weiping Zou, Yang-Xin Fu, and others showed that PD-L1 expression on tumor-associated professional antigen-presenting cells, as opposed tumor cells, could be the major target for anti-PD-1/L1 responsiveness for some cancers [95–97].