Fatty acid oxidation controls CD8+ tissue-resident memory T cell survival in gastric adenocarcinoma.

The success of checkpoint inhibitors in cancer treatment is associated with the infiltration of tissue-resident memory T cells (Trm). In this study, we found that about 30% of tumor infiltrating lymphocytes (TILs) in TME of gastric adenocarcinoma (GAC) were CD69+CD103+ Trm cells. Trm cells were low in patients with metastasis and the presence of Trm cells was associated with better prognosis in GAC patients. Trm cells expressed high PD-1, TIGIT, and CD39 and represented tumor-reactive TILs. Instead of utilizing glucose, Trm cells relied on fatty acid oxidation for cell survival. Deprivation of fatty acid resulted in Trm cell death. In a tumor cell-T cell coculture system, GAC cancer cells outcompeted Trm cells for lipid uptake and induced Trm cell death. Targeting PD-L1 decreased fatty acid binding protein (Fabp) 4 and Fabp5 expression in tumor cells of GAC. In contrast, the blockade of PD-L1 increased Fabp4/5 expression in Trm cells, promoting lipid uptake by Trm cells and resulting in better survival of Trm cells in vitro and in vivo. PD-L1 blockade unleashed Trm cells specifically in the patient-derived xenograft (PDX) mice. PDX mice that did not response to PD-L1 blockade had less Trm cells than responders. Together, these data demonstrated that Trm cells represent a subset of TILs in the antitumor immune response and that metabolic reprogramming could be a promising way to prolong the longevity of Trm cells and enhance antitumor immunity in GAC.