Abstract 2308: Inhibition of fatty acid synthesis and concurrent lipid deprivation decreases neuroendocrine cancer cell proliferation and colony formation
Authors: Johnson Jeremy , Zaytseva Yekaterina Y. , Castle Jennifer , Evers B. Mark , Rychahou Piotr 
Published: June 2022

Abstract
Introduction. Gastroenteropancreatic neuroendocrine tumors (GEP-NETs), the second most common digestive cancer in terms of prevalence, can be particularly challenging to treat due to resistance to current clinical regimens. Lipid metabolism provides an important energy source for cancer cells; cells increase lipid supply by endogenous synthesis or exogenous uptake. Both processes can become dysregulated in cancer, but little is known about the role of either pathway in neuroendocrine tumors (NETs). The goal of this project was to determine whether inhibition of lipid synthesis with concurrent lipid deprivation affects NET cell proliferation and survival.
Methods. (i) Expression and localization of fatty acid synthase (FASN) in NET patient samples (n=39) and human cell lines (BON, QGP-1, and NT-3) were examined with immunohistochemistry and immunoblotting, respectively. (ii) NET neutral lipid stores were determined with immunofluorescent analysis of Bodipy 493/503 staining. (iii) To study the role of lipid synthesis and lipid uptake on colony formation, NET cells were treated with TVB-3664 with or without FA depletion for 10d. Colonies were visualized with sulforhodamine B (SRB) dye staining and quantified with photospectrometry. (iv) To study the effect of lipid synthesis and uptake on proliferation, NET cells were treated with TVB-3664 with or without FA depletion for 72h, 96h, and 120h. Cellular growth was determined with SRB assays. (v) The effect of TVB-3664 on cyclin D1 and β-catenin expression in NET cells was determined with immunoblotting.
Results. (i) FASN was detected in the cytoplasm of all 39 NET primary and metastatic tissue samples; scores of 5 or 6 indicated robust expression in 38/39 samples. Among cell lines, FASN expression was highest in BON cells followed by similar levels in QGP-1 and NT-3 cells. (ii) TVB-3664 treatment or lipid deprivation for 5d reduced neutral lipid storage in BON cells; combined TVB-3664 treatment with FA depletion for 5d fully depleted BON lipid stores. (iii) TVB-3664 treatment, but not FA deprivation, reduced NET colony formation by ~25% in BON cells and ~50% in QGP-1 cells. TVB-3664 treatment with FA deprivation reduced colony formation by ~65% in BON cells and ~75% in QGP-1 cells. (iv) TVB-3664 treatment or FA deprivation reduced NET cell proliferation at 72h, 96h, and 120h. (v) TVB-3664 treatment reduced cyclin D1 expression in BON and QGP-1 cells and β-catenin levels in BON cells.
Conclusions. Our findings indicate that FASN is robustly expressed in NET patient samples and cell lines. Inhibition of endogenous lipid synthesis with concurrent lipid deprivation reduces colony formation and proliferation of NET cells. Importantly, our findings show that lipid metabolism promotes NET cell growth and that targeting de novo lipogenesis may be a potential treatment strategy for advanced GEP-NETs.
Citation Format: Jeremy Johnson, Yekaterina Y. Zaytseva, Jennifer Castle, B. Mark Evers, Piotr Rychahou. Inhibition of fatty acid synthesis and concurrent lipid deprivation decreases neuroendocrine cancer cell proliferation and colony formation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2308.