Diet therapy abates mutant APC and KRas effects by reshaping plasma membrane cholesterol nanodomains

Abstract

Cholesterol-enriched plasma membrane domains are known to serve as signaling platforms in a diverse array of cellular processes. However, the link between cholesterol homeostasis and mutant APC-KRas-associated colorectal tumorigenesis remains to be established. Thus, we investigated the impact of Apc-Kras on 1) colonocyte plasma membrane cholesterol homeostasis, order, and receptor nanoclustering, 2) colonocyte cell proliferation, and 3) whether these effects are modulated by select membrane active dietaries (MADs). We observed that oncogenic APC-KRas increased membrane order by perturbing cholesterol homeostasis when cell proliferation is upregulated, in part by altering the expression of genes associated with cholesterol influx, export and de novo synthesis in mouse colorectal cancer (CRC) models and CRC patients. In addition, oncogene-induced loss of cholesterol homeostasis altered Fzd7, LRP6, and KRas cluster structure/organization. Notably, we show that the combination of chemoprotective MADs, i.e., n-3 PUFAs and curcumin, reduced colonic membrane free cholesterol, order, receptor cluster size, cell proliferation, and the number of dysplastic foci in mutant APC-KRas models. This work highlights the dynamic shaping of plasma membrane organization during colon tumorigenesis and the utility of membrane-targeted cancer therapy.