Expression of programmed death-ligand 1 (PD-L1) plays a significant role in creating an immune suppressive tumor microenvironment. We investigated the relationship between the aberrant choline metabolism observed in most cancers and PD-L1 expression in triple negative human MDA-MB-231 breast cancer cells. Using siRNA to downregulate Chk-a or PD-L1 or both, we identified a close inverse interdependence between Chk-α and PD-L1. We identified, for the first time, the role of PD-L1 in cancer cell metabolism. These results have significant implications for therapy and provide new insights into the relationship between metabolism and immune resistance in these breast cancer cells.