This interaction was eliminated in cells with Chk or cyclooxygenase (COX-2) silenced, suggesting that choline metabolism and inflammation played a role in this inverse relationship.57 Downregulation of PD-L1 resulted in significant changes in several metabolites detected by 1H MRS, identifying for the first time previously unknown roles of PD-L1 in cancer cell metabolic reprogramming (Figure 2).57 Here, CHKA is linked to cancer.