Abstract 4494: Structure, dynamics and therapeutic potential of fatty acid synthase

Abstract De novo lipid synthesis is facilitated by the multifunctional enzyme fatty acid synthase (FASN), a hallmark of cancer associated with chemotherapeutic resistance and poor prognosis. Human FASN (hFASN) is a dynamic protein that undergoes significant conformational changes during catalysis, posing challenges for structural characterization. To date, no structural information is available for full-length hFASN, hindering our understanding of its catalytic mechanism and complicating rational drug design.Here, we report the structure of hFASN resolved using electron cryo-microscopy (cryoEM). The modifying region of hFASN was determined at near-atomic resolution using a recombinant expression system bound to the first-in-class inhibitor Denifanstat, enabling structure-based small molecule discovery. Additionally, we solved the full-length structure of endogenous hFASN from MCF7 cells, revealing an interaction with the small heat shock protein HSP27. In some 2D classes of hFASN from cryoEM data, we found partial unfolding of the modifying region, evidence of potential protein degradation. However, HSP27 knockdown in breast cancer cell lines did not alter overall hFASN levels, indicating that this interaction may be transient or involve additional partners.Mass spectrometry-based post-translational modification analysis further identified dihydroxylation of proline, arginine, and tyrosine residues in hFASN from MCF7 cells, likely reflecting oxidative stress. These modifications may play a role in protein stabilization or regulation under stress conditions, highlighting a potential mechanism for hFASN activity modulation. Together, these findings provide critical structural and regulatory insights, paving the way for targeted therapeutic development. Citation Format: Naimul Hasan, Alexander Keszei, Matthew Waas, Thomas Kislinger, Razq Hakem, Mohammad Mazhab-Jafari. Structure, dynamics and therapeutic potential of fatty acid synthase [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 4494.