PDCD1 and digestive system neoplasm: In addition, the PD-1/PD-L1 function blockage may attenuate apoptosis of CD8-positive T-cells by regulating the PI3K/AKT/mTOR pathway in gastrointestinal tumors [28]. A negative feedback system by inducing active T-cell apoptosis and interleukin-10 (IL-10) was detected in colorectal cancer [29].