Abstract 6575: Overexpression of fatty acidy synthase increases exosomes secretion in colorectal cancer

Abstract More than 50% of colorectal cancer (CRC) patients develop metastases, with the liver being the most common site of metastasis. Fatty acid synthase (FASN), a key enzyme of de novo lipid synthesis, is overexpressed and strongly associated with metastasis and poor prognosis in CRC. FASN catalyzes the biosynthesis of palmitate, an essential component of structural lipids. Exosomes are composed of a lipid bilayer membrane and carry a wide range of bioactive molecules. Tumor-derived exosomes play a critical role in establishing a pre-metastatic niche (PMN) to support metastasis. Hepatic stellate cells (HSCs) can be activated by tumor signals and transformed to cancer-associated fibroblast, thus, contributing to PMN formation. However, the mechanisms by which exosomes promote HSCs activation and their subsequent contribution to PMN formation during CRC liver metastasis are not fully understood. Therefore, this study aims to investigate the contribution of FASN in exosomes formation, release, and HSCs activation in CRC. To delineate the role of FASN in exosomes formation, FASN-knockdown (FASN KD), FASN-overexpression (FASN OE), and pharmacological inhibition of FASN in CRC cells were utilized. Cells were cultured in media containing exosome-free FBS for 48h. Exosomes were isolated from cell culture media using ultracentrifugation. The concentration and size of exosomes were measured using nanoparticle tracking analysis. Exosomes markers were assessed using western blot. To investigate the functional impact of CRC-derived exosomes, HSCs LX-2 was used. The purity of isolated exosomes was confirmed by assessing the expression of CD9, Alix, TSG101, and syntenin. Secretion of exosomes by FASN-KD cells (ExoFASN-KD) and by cells treated with FASN inhibitors was significantly reduced as compared to control cells. Moreover, FASN expression was decreased in ExoFASN-KD. In contrast, secretion of exosomes by FASN-OE cells (ExoFASN-OE) was significantly increased as compared to control cells. Consistently, we observed an increase in expression of FASN in ExoFASN-OE. To test if FASN expression in CRC cells affects the ability of secreted exosomes to activate HSCs, LX-2 cells were incubated with exosomes from control and FASN-KD CRC cells. We found that the exposure to exosomes from control CRC cells leads to robust activation of LX-2 cells as determined by FAP and α-SMA expression; however, the level of LX-2 activation was significantly reduced when cells were exposed to ExoFASN-KD. In summary, our data suggests that FASN promotes exosomes secretion in CRC. Importantly, the association between the level of FASN expression in CRC cells and activation of LX-2 cells by secreted exosomes suggests a potential role for FASN in PMN formation. Further studies are needed to elucidate the functional importance of FASN in PMN formation via exosomes secretion in CRC. Citation Format: Josiane Weber Tessmann, Yekaterina Zaytseva. Overexpression of fatty acidy synthase increases exosomes secretion in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6575.