Suppression of membranous LRP5 recycling, WNT/β-catenin signaling, and colorectal tumorigenesis by 15-LOX-1 peroxidation of PI3P_linoleic acid

Abstract

SUMMARYAberrant Wnt/β-catenin activation is a major driver of colorectal cancer (CRC), which is typically initiated byAPCmutations. Additional modifiable factors beyondAPCmutations have been recognized to be important for further potentiation of aberrant β-catenin activation to promote colorectal tumorigenesis. These factors have yet to be clearly identified. Western-type diets are increasingly enriched in linoleic acid (LA). LA-enriched diet however promotes chemically-induced colorectal tumorigenesis in rodent models. Furthermore, the main metabolizing enzyme of LA, 15-lipoxygenase-1 (15-LOX-1), is transcriptionally silenced in CRC. Whether LA and 15-LOX-1 affect Wnt/β-catenin signaling to modulate colorectal tumorigenesis is poorly understood. Herein, we report that high dietary LA promoted colorectal tumorigenesis in mice with intestinally targetedAPCmutation (ApcΔ580) by upregulating a Wnt receptor, LRP5 expression, and β-catenin activation. 15-LOX-1 transgenic expression in intestinal epithelial cells suppressed LRP5 expression, β-catenin activation and subsequently CRC in these mice. In particular, 15-LOX-1 peroxidation of LA in phosphatidylinositol-3-phosphates (PI3P_LA) into PI3P_13-HODE decreased PI3P binding to SNX17and LRP5, which inhibited LRP5 recycling from endosomes to the plasma membrane, thereby leading to an increase of LRP5 lysosomal degradation. Our findings demonstrate for the first time that 15-LOX-1 metabolism of LA in PI3P to regulate LRP5 membrane abundance is a modifiable factor of Wnt/β-catenin aberrant signaling that could be potentially therapeutically targeted to suppress colorectal tumorigenesis and progression.