Abstract P5-05-10: Inhibition of FASN as a potential treatment of advanced therapy-resistant breast cancer

Abstract

Abstract INTRODUCTION: The majority of breast cancers are estrogen receptor (ERα) positive making endocrine therapy a mainstay for these patients. Unfortunately, resistance to endocrine therapy is a common occurrence. Fatty acid synthase (FASN) is a key enzyme in lipid biosynthesis and is overexpressed in more aggressive and therapy-resistant tumors, including breast cancers. METHODS: The effect of the FASN inhibitor TVB-3166 on ERα expression and cell growth was characterized in tamoxifen-resistant and fulvestrant-resistant cell lines, xenografts, and patient explants. Subcellular localization of ERα was assessed using subcellular fractionations. Palmitoylation and ubiquitination of ERα were assessed by immunoprecipitation. ERα and p-eIF2α protein levels were analyzed by western blotting after treatment with TVB-3166 with or without the addition of palmitate or BAPTA. RESULTS: TVB-3166 treatment leads to a marked inhibition of proliferation in tamoxifen-resistant and fulvestrant-resistant cells compared to the parental cells. Additionally, TVB-3166 significantly inhibited tamoxifen-resistant breast tumor growth in mice and decreased proliferation of primary tumor explants compared to untreated controls. FASN inhibition significantly reduced ERα levels most prominently in endocrine resistant cells and altered its subcellular localization. Furthermore, we showed that the reduction of ERα expression upon TVB-3166 treatment is mediated through the induction of endoplasmic reticulum stress. CONCLUSION: Our preclinical data provide evidence that FASN inhibition by TVB-3166 presents a promising therapeutic strategy for treatment of endocrine-resistant breast cancer. Further clinical development of FASN inhibitors for endocrine resistant breast cancer should be considered. Citation Format: Henriette U Balinda. Inhibition of FASN as a potential treatment of advanced therapy-resistant breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-05-10.