CD274 and neoplasm: Moreover, the S283 residue of PD-L1 was found to have a clear-cut role in mediating PD-L1 cell-autonomous pro-tumorigenic roles, as indicated by the fact that until day 77, none of the nine S283A-PD-L1-MDA-injected mice developed a palpable tumor (Group 3; Figure 8B and Figure 9).