Targeting DGAT1 reprograms lipid landscape and restores CD8⁺ T cell immunity in pancreatic cancer.

Lipid accumulation is a hallmark of the pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment, yet effective strategies to reprogram this lipid-rich niche and restore anti-tumor immunity remain limited. Here, we show that diacylglycerol O-acyltransferase 1 (DGAT1) as a tumor-intrinsic metabolic checkpoint that promotes immune evasion. DGAT1 inhibition rewires tumor lipid metabolism by promoting increased fatty acid uptake and redistribution, thereby depleting extracellular free fatty acids that impair CD8⁺ T cell function. Mechanistically, decreased palmitate availability alleviates endoplasmic reticulum stress, preserves FOXO1 activity, and supports stem-like CD8⁺ T cell differentiation. This competitive lipid remodeling enhances memory potential, restrains terminal exhaustion, and sensitizes PDAC tumors to PD-1 checkpoint blockade in vivo. Together, our findings identify tumor-immune lipid crosstalk as a key barrier to effective immunity in PDAC and establish DGAT1 as a promising therapeutic target to restore T cell function and improve immunotherapy response.