Altered fatty acid metabolism continues to be an attractive target for therapeutic intervention in cancer. We previously found that colorectal cancer (CRC) cells with a higher metastatic potential express a higher level of fatty acid translocase (CD36). However, the role of CD36 in CRC metastasis has not been studied. Here, we demonstrate that high expression of CD36 promotes invasion of CRC cells. Consistently, CD36 promoted lung metastasis in the tail vein model and GI metastasis in the cecum injection model. RNA-Seq analysis of CRC cells with altered expression of CD36 revealed an association between high expression of CD36 and upregulation of MMP28, a novel member of the metallopeptidase family of proteins. Using shRNA-mediated knockdown and overexpression of CD36, we confirmed that CD36 regulates MMP28 expression in CRC cells. siRNA-mediated knockdown of MMP28 decreases invasion of CRC cells, suggesting that MMP28 regulates the metastatic properties of cells downstream of CD36. Importantly, high expression of MMP28 leads to a significant decrease in active E-cadherin and an increase in the products of E-cadherin cleavage, CTF1 and CTF2. In summary, upregulation of CD36 expression promotes the metastatic properties of CRC via upregulation of MMP28 and an increase in E-cadherin cleavage, suggesting that targeting the CD36–MMP28 axis may be an effective therapeutic strategy for CRC metastasis.

Altered lipid metabolism is a potential target for therapeutic intervention in cancer. Overexpression of Fatty Acid Synthase (FASN) correlates with poor prognosis in colorectal cancer (CRC). While multiple studies show that upregulation of lipogenesis is critically important for CRC progression, the contribution of FASN to CRC initiation is poorly understood. We utilize a C57BL/6-Apc/Villin-Cre mouse model with knockout of FASN in intestinal epithelial cells to show that the heterozygous deletion of FASN increases mouse survival and decreases the number of intestinal adenomas. Using RNA-Seq and gene set enrichment analysis, we demonstrate that a decrease in FASN expression is associated with inhibition of pathways involved in cellular proliferation, energy production, and CRC progression. Metabolic and reverse phase protein array analyses demonstrate consistent changes in alteration of metabolic pathways involved in both anabolism and energy production. Downregulation of FASN expression reduces the levels of metabolites within glycolysis and tricarboxylic acid cycle with the most significant reduction in the level of citrate, a master metabolite, which enhances ATP production and fuels anabolic pathways. In summary, we demonstrate the critical importance of FASN during CRC initiation. These findings suggest that targeting FASN is a potential therapeutic approach for early stages of CRC or as a preventive strategy for this disease.

Background: Upregulation of lipid synthesis has been associated with poor clinical outcomes in colorectal cancer (CRC). Fatty acid synthase (FASN) synthesizes 16-carbon fatty acid palmitate which can be utilized for post-translational modifications of various proteins. Notum, a palmitoleoyl-protein carboxylesterase, is involved in the negative regulation of the Wnt signaling via its role in de-palmitoylation of Wnt ligands and has been identified as a marker for poor prognosis in CRC. However, the crosstalk between FASN and Notum has not been reported. Our preliminary data suggest that FASN regulates β-catenin signaling and Notum expression. Therefore, the purpose of this study is to elucidate (I) the mechanisms of how FASN regulates expression of Notum and (II) the contribution of the FASN/Notum axis to CRC. Methods: Tumor and normal intestinal organoids were established from transgenic mice models, ApcMin and Apc/VillinCre-ERT2, with inducible hetero- and homozygous deletion of FASN. The effect of genetic deletion and pharmacological inhibition of FASN on organoid growth and viability was assessed by 4-hydroxytamoxifen (4-OHT) and TVB-3664 (a FASN inhibitor) treatments, respectively. LIVE/DEAD™ Viability/Cytotoxicity Cell Viability Kit and Cell Titer-Glo® 3D Cell Viability Assays were used for quantitative analysis of growth and viability. HCT116, NTC and FASN shRNA, and SW480, control and FASN overexpression, cells were used for analysis. Results: ERT2-mediated deletion of Apc leads to upregulation of FASN and Notum expression in mouse intestinal tissues and organoids. RNA-seq analysis of adenomas from Apc/VillinCre mice showed that hetero- and homozygous germline deletion of FASN is associated with a significant decrease in the number of adenomas, expression of Notum and CRC stem cell markers. Using qRT-PCR and Western blot, we confirmed that FASN downregulation is associated with a decrease in active β-catenin, Notum, and stem cell markers. Consistently with Apc/VillinCre model, downregulation of FASN results in a decrease in bud formation in Apc/VillinCre-ERT2 organoids, and viability and size in ApcMin organoids. Furthermore, overexpression of FASN increases the levels of active and total β-catenin, Notum, and stem cell markers expression in SW480 cells. In contrast, shRNA-mediated deletion of FASN decreases expression of Notum in HCT116 cells. Conclusion: Downregulation of FASN leads to a decrease in expression of Notum and is associated with morphological changes and a significant decrease in viability in organoid models. Conversely, FASN overexpression upregulates Notum expression suggesting a potential cross-talk between de novo lipid synthesis and Notum. Delineating the role of FASN regulation of stemness via altered β-catenin signaling and expression of Notum and other stem cell markers will provide the rationale for targeting the FASN/Notum axis as a preventative or early-stage therapeutic approach in CRC. Citation Format: Courtney Olivia Kelson, James Drury, Daheng He, Chi Wang, Yekaterina Zaytseva. Fatty acid synthase regulates expression of Notum in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2581.

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