PDCD1 and neoplasm: However, some important functional issues remained poorly characterized including upregulated signaling pathways in Treg from injured tissues and regenerated tissues, tumor splenic Treg specific pathways, tumor tissue Treg’s specific pathways, Treg canonical secretome, Treg non-canonical secretomes, Foxp3 collaboration/non-collaboration transcriptomes, immune checkpoint receptors PD-1 and CTLA-4 collaboration/non-collaboration transcriptomes, and ROS regulated Treg transcriptomes.