Abstract 3135: Postmenopausal obese mammary adipocytes promote breast tumorigenesis via the LCN2/IL-6/STAT3 signaling axis
Authors: Roy Roopali , Man Emily , Gonzalez Katherine , Merritt Lauren , Daisy Cassandra , Aldakhallah Rama , Sun Liang , Isaac Biju , Rockowitz Shira , Lotz-Bousvaros Margaret , Pories Susan , Moses Marsha A. 
Published: June 2022

Obesity is associated with a substantially increased risk (~50%) and a poor prognosis of breast cancer (BC) in postmenopausal (PM) women. The mechanism(s) underlying obesity-related BC are not clearly understood and, to date, most studies focus on the systemic effects of subcutaneous or visceral adipocytes on BC. We hypothesized that the increased local presence of ‘obese’ mammary adipocytes within the breast microenvironment promotes the acquisition of an invasive and vascular breast tumor cell phenotype and thereby markedly accelerates tumor proliferation and progression. We first asked whether local interactions between mammary adipocytes and BC cells might promote tumor growth and if so, what the underlying mechanism(s) might be. BC cells (ER- and ER+), when treated with the secretome of mammary adipocytes from obese women (ObAdCM), upregulated potent angiogenic/inflammatory factors, including VEGF, bFGF, lipocalin-2 (LCN2), IL-6 and significantly suppressed the angiogenesis inhibitor Tsp-1. ObAdCM stimulated endothelial cell (EC) recruitment by BC cells and increased EC proliferation, indispensable steps in tumor neovascularization. PM ObAdCM significantly stimulated BC cell proliferation, migration and invasion. Both IL-6 and LCN2-neutralization resulted in significant reduction of the ObAdCM-stimulated BC cell migration and proliferation, suggesting that these factors play a role in obesity-mediated BC progression. ObAdCM induced pSTAT3/pAkt signaling in BC cells and IL-6 and LCN2 could independently stimulate pSTAT3 in BC cells. STAT3 inhibition abrogated the ObACDM-mediated effects on BC cell proliferation and migration, suggesting that the pro-tumorigenic effects of PM obese mammary adipocytes are mediated by LCN2/IL-6/STAT3 signaling. Comparative RNAseq analyses identified &gt;30 differentially expressed genes (DEGs) in PM compared to pre-menopausal (Pre-M) obese mammary adipocytes. Furthermore, GO and KEGG enrichment analysis of DEGs suggested an upregulation of PI3K/Akt signaling, ECM-receptor interactions, focal adhesions and lipid/fatty acid metabolism in PM mammary adipocytes. Taken together, our results indicate that obese mammary adipocytes in the breast tumor microenvironment can promote migration, proliferation, invasion and the vascular phenotype of BC cells and suggest that targeting the LCN2/IL-6/STAT3 signaling axis may be a useful strategy in the treatment of obesity-driven breast tumorigenesis. [Supported by NIH RO1CA185530, the Breast Cancer Research Foundation, the Karp Family Foundation and the Nile Albright Research Foundation]

Citation Format: Roopali Roy, Emily Man, Katherine Gonzalez, Lauren Merritt, Cassandra Daisy, Rama Aldakhallah, Liang Sun, Biju Isaac, Shira Rockowitz, Margaret Lotz-Bousvaros, Susan Pories, Marsha A. Moses. Postmenopausal obese mammary adipocytes promote breast tumorigenesis via the LCN2/IL-6/STAT3 signaling axis [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 3135.