Metabolic reprogramming through SREBP2-driven cholesterol synthesis in CAFs of CMS4 colorectal cancer

Colorectal cancer has been stratified based on gene expression profiles into consensus molecular subtypes (CMS). Among these, the mesenchymal subtype (CMS4), which accounts for approximately 23% of cases, is associated with a particularly poor prognosis compared with the other subtypes. It has been increasingly recognized that the high malignancy of CMS4 colorectal cancer is driven by activation of the tumor stroma, predominantly composed of CAFs, and by its interactions with cancer cells within the tumor microenvironment (TME). However, the mechanisms remain to be unclear. Cholesterol is essential for cancer, particularly through its roles in membrane integrity and intracellular signaling. Dysregulation of cholesterol homeostasis has been implicated in cancer progression. Recent studies have shown that activation of SREBP2, a key transcription factor for cholesterol biosynthesis, contributes to the development of aggressive serrated colorectal tumors characterized by desmoplasia. However, the metabolic state of cancer-associated fibroblasts (CAFs), particularly regarding cholesterol metabolism, remains unclear. We analyzed bulk RNA sequencing data from 10 colorectal cancer samples. Gene set enrichment analysis (GSEA) was performed to compare CAFs from CMS4 tumors with those from other CMS subtypes. Subsequently, we established CAF lines derived from CMS4 and the other subtype tumors and examined the impact of CAF cholesterol metabolism on tumor progression. We revealed that CMS4-CAFs exhibited significant enrichment of gene sets related to cholesterol homeostasis. In particular expression levels of SREBP2 and its downstream genes were markedly upregulated in CMS4-CAFs. Furthermore our in vitro results showed that inhibition of cholesterol biosynthesis or SREBF2 knocking down reduced the proliferative capacity of CMS4-CAFs and suppressed tumor migration. These findings highlight a potential metabolic feature of CAFs in CMS4 colorectal cancer that may contribute to tumor aggressiveness.