PDCD1 and cancer: Similarly, treatment with monoclonal antibodies for inhibiting PD-1/PD-L1 mediated activation of phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways by adding a phosphoryl group to AKT and ERK1/2, respectively, promoting cancer cell proliferation in vivo (Zheng and Zhou, 2015).