In general oncology, PD-L1 is expressed on most tumor cells and binds to PD-1 on tumor-specific CTLs, resulting in the recruitment of SHP-1 and SHP-2 to the C-terminal of the PD-1 intracellular domain, leading to the inhibition of downstream PI3K/Akt signaling, which downregulates cell survival gene Bcl-xL expression and induces the apoptosis of CTLs. This evidence concerns the gene PTPN11 and neoplasm.