Abstract PO5-25-05: Crosstalk between adipocyte and tumor cells with ESR1 mutations via adipsin enhances tumor growth

Abstract

Abstract While endocrine therapies have shown clinical benefits for breast cancer with ESR1 mutations, resistance development is a significant challenge. Evidence suggests that the complement system is critical to tumor development, and recent studies highlight the role of adipsin in breast cancer growth. In a previous study, we characterized the role of complement pathway-mediated adipsin in ESR1 mutant cell lines (Y537S and D538G), identifying the upregulation of adipsin, C3, and C3aR in ESR1 mutant cells. The interaction between C3a and C3aR enhanced ESR1 mutant cell growth, and inhibiting C3aR abolished cell growth and increased apoptosis. Combining C3aR inhibitors with fulvestrant or CDK4/6 inhibitors had a synergistic inhibitory effect on ESR1 mutant cells. Our findings suggest that the complement pathway plays a role in ESR1 mutant cell proliferation and that C3aR is a potential target to mitigate ESR1 mutant breast cancer growth and metastasis. Additionally, we demonstrated the critical role of the feedback loop of adipsin in ESR1 mutant cell growth in adipocyte crosstalk. Using differentiated mouse 3T3-L1 adipocytes induced with tumor-conditioned media from ESR1 mutant cells, we observed the upregulation of adipsin, C3, and C3a in the adipocyte secretome, which enhanced C3a levels. Blocking the interaction between C3a and C3aR in ESR1 mutant cells using a C3aR inhibitor significantly inhibited ESR1 mutant cell growth compared to wild-type cells and enhanced apoptosis. Our findings suggest that upregulation of adipsin from ESR1 mutant cells and adipocytes in crosstalk increases tumor cell growth. Future studies will investigate the critical role of adipsin's auto- and paracrine effects in breast cancer with ESR1 mutations. Citation Format: Artem Belyakov, Kideok Jin. Crosstalk between adipocyte and tumor cells with ESR1 mutations via adipsin enhances tumor growth [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-25-05.