PDCD1 and neoplasm: Our analysis suggests that cell-surface receptors including those targeted by checkpoint inhibitors in tumor immunotherapy (e.g. PD-1) or T-cell co-stimulatory molecules (e.g. ICOS (inducible T-cell COStimulator (59)) can couple with common and context-dependent downstream TFs within a given cell type but in different tissue contexts (Figure 4C,F,I).