Abstract 2784: Fatty acid synthase enhances stem-like properties of normal intestinal and colorectal cancer cells via an increase in notum expression and secretion
Authors: Kelson Courtney Olivia , Tessmann Josiane Weber , He Daheng , Wang Chi , Zaytseva Yekaterina 
Published: March 2024

Abstract
Introduction: Overexpression of lipogenic enzymes has been associated with a poor clinical outcome in colorectal cancer (CRC). Fatty acid synthase (FASN) synthesizes palmitate which can be utilized for post-translational modifications of various proteins. Notum, a palmitoleoyl-protein, prevents the downstream activation of Wnt signaling by de-palmitoylating Wnt ligands. Notum is also a CRC stem cell marker, and its expression correlates with poor prognosis in CRC. We found that upregulation of FASN is associated with an increase in Notum expression in mouse adenoma tissues. Therefore, the purpose of this study is to elucidate the mechanisms and contribution of FASN/Notum axis in CRC.
Methods: Adenoma and normal intestinal organoids, established from ApcMin/VillinCre-ERT2 and Apc/VillinCre-ERT2 mouse models with hetero- and homozygous deletion of FASN. 4-hydroxytamoxifen (4-OHT) and TVB-3664 (FASN inhibitor) treatments were used to assess the effect of FASN deletion/inhibition on organoid growth and viability. LIVE/DEAD™ Viability/Cytotoxicity and Cell Titer-Glo® 3D Cell Viability Assays were used for quantitative analysis of growth. Human NOTUM/Protein notum homolog ELISA Kit was used to analyze Notum secretion. CRC cells, NTC and FASN shRNA, and control and FASN overexpression, were used for Notum analysis.
Results: The TCGA data analysis shows that Notum is significantly upregulated in CRC and its expression correlates with expression of FASN in tumor tissue. Utilizing qRT-PCR and Western blot analyses, we show that downregulation of FASN leads to a decrease in expressions of active β-catenin, Notum, and other stem cell markers in transgenic mouse models. Moreover, 4-OHT-mediated inhibition of FASN results in decrease viability and size in ApcMin/FASN/VillinCre-ERT2 and Apc/FASN/VillinCre-ERT2 organoids. Consistently, shRNA-mediated deletion of FASN decreases expression of Notum in CRC cells. In contrast, overexpression of FASN increases the expression levels of active and total β-catenin, Notum, and other stem cell markers in SW480 cells. We show that normal epithelial cells exposed to CRC cell medium exhibit stem-like phenotype which is reduced when cells are exposed to medium collected from Notum shRNA knockdown cells. Moreover, the addition of recombinant Notum restores this phenotype.
Conclusion: In summary, downregulation of FASN leads to a decrease in expression of Notum and is associated with morphological changes and 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 stem-like properties via upregulation of β-catenin signaling and expression of Notum and other stem cell markers will provide the rationale for targeting the FASN/Notum axis in CRC.
Citation Format: Courtney Olivia Kelson, Josiane Weber Tessmann, Daheng He, Chi Wang, Yekaterina Zaytseva. Fatty acid synthase enhances stem-like properties of normal intestinal and colorectal cancer cells via an increase in notum expression and secretion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2784.