Indoleamine 2,3-dioxygenase 1 (IDO1) inhibition is another metabolic approach promoting Vγ9Vδ2 T-cell cytotoxicity against human breast cancer cells and pancreatic ductal adenocarcinoma (PDAC) cells by enhancing perforin production (150), degranulation, and cytokine production (151). This evidence concerns the gene IDO1 and pancreatic ductal adenocarcinoma.