Mogol, A. N. | bioRxiv Science

bioRxiv2025

ACSS2-Mediated Metabolic-Epigenetic Crosstalk Drives Fulvestrant Resistance and Represents a Novel Therapeutic Target

1.Endocrine therapies target hormone-dependent cancer cells, primarily through estrogen receptor alpha (ER), expressed in [~]70% of breast cancers (ER+). Despite treatment advances, 30-40% of ER+ breast cancer patients experience recurrence and metastasis, with 5-year survival rates of only 31.9%. We validated poor outcomes for liver metastasis patients treated with Fulvestrant (Fulv) using the local Carle Foundation Hospital cohort and examined metabolic pathways in liver metastatic patient-derived xenograft (PDX) models, revealing upregulated lipid and acetyl-CoA production. Our previous work demonstrated that combining Fulv with acetyl-CoA synthase inhibitor (ACSI) targeting Acyl-CoA Synthetase Short Chain Family Member 2 (ACSS2), synergistically reduced ER+ metastatic breast cancer (MBC) cell viability in vitro. Using multiple analytical approaches-isotope tracing, CUT&RUN sequencing, immunofluorescence, western blot, and RNA sequencing-we characterized the effects of acetyl-CoA synthesis inhibition on Fulv-induced alterations. Fulv treatment of MBC cells increased ACSS2 expression and acetate utilization. Isotope tracing revealed that Fulv decreased acetate flux to the TCA cycle while promoting fatty acid synthesis. Importantly, ACSS2 was predominantly nuclear and CUT&RUN sequencing showed that Fulv treatment increased ACSS2 chromatin occupancy and ER/ACSS2/H3K27ac overlapping sites near genes associated with tumor progression, which was eliminated by combination of ACSI and Fulv. RNA sequencing revealed reduction of Fulv-induced expression of genes involved in cancer cell metabolism and key signaling pathways in cancer with the Fulv+ACSI combination. In a therapy-resistant xenograft model, combining Fulv and ACSI reduced Fulv-dependent increase in metastatic burden. Our findings indicate ACSS2 contributes to endocrine therapy resistance through nuclear acetyl-CoA provision for epigenetic alterations. Targeting these cancer cell adaptations represents a novel therapeutic approach potentially reducing metastasis-related mortality and improving breast cancer treatment outcomes.

cancer biology↗

bioRxiv2021

Targeting metabolic adaptations in the breast cancer liver metastatic niche using dietary approaches to improve endocrine therapy efficacy

Estrogen receptor-positive (ER+) metastatic tumors contribute to nearly 70% of breast cancer-related deaths. Most patients with ER+ metastatic breast cancer (MBC) undergo treatment with the estrogen receptor antagonist fulvestrant (Fulv) as standard-of-care. Yet, among such patients, metastasis in liver is associated with reduced overall survival compared to other metastasis sites. The factors underlying the reduced responsiveness of liver metastases to ER-targeting agents remain unknown, impeding the development of more effective treatment approaches to improve outcomes for patients with ER+ liver metastases. We therefore evaluated site-specific changes in MBC cells and determined the mechanisms through which the liver metastatic niche specifically influences ER+ tumor metabolism and drug resistance. We characterized ER activity of MBC cells both in vitro, using a novel system of tissue-specific extracellular matrix hydrogels representing the stroma of ER+ tumor metastatic sites (liver, lung and bone), and in vivo, in liver and lung metastasis mouse models. ER+ metastatic liver tumors and MBC cells grown in liver hydrogels displayed upregulated expression of glucose metabolism enzymes in response to Fulv. Furthermore, differential ER activity, but not expression, was detected in liver hydrogels. In vivo, increased glucose metabolism led to increased glycogen deposition in liver metastatic tumors, while a fasting-mimicking diet increased efficacy of Fulv treatment to reduce the metastatic burden. ImplicationsOur findings identify a novel mechanism of endocrine resistance driven by the liver tumor microenvironment. These results may guide the development of dietary strategies to circumvent drug resistance in liver metastasis, with potential applicability in other metastatic diseases.

cancer biology↗