PDCD1 and neoplasm: IPA identified significant changes in the antigen presentation pathway, which we explored previously [34], and in several others including the Th1, Th1 and Th2, PD-1/PD-L1 cancer immunotherapy, and tumor microenvironment pathways, all of which included genes relating to the PD-1/PD-L1 signaling axis (Fig. 1A).