Abstract P1-03-02: Estrogens contribute to cytokine upregulation and cancer stem cell recruitment upon breast cancer contact with mature human mammary adipocytes: Effects of estrogen type and adipocyte donor weight

Abstract

Abstract Consequences of the obesity epidemic on cancer morbidity and mortality are not fully appreciated. While obesity confers increased cancer risk and worse outcome, mechanisms thereof are not fully known. We show prolonged co-culture of fat cells (human adipocyte stem cells, differentiated adipocytes or mature adipocytes) from breast tissue together with breast cancer lines or cultured primary dissociated human breast tumor cells increases secretion of six different pro-inflammatory cytokines, each of which contributes to tumor progression through cancer stem cell recruitment. Prolonged exposure to fat cells or to each cytokine increases the proportion of cells that form mammosphere and express ALDH1 activity in vitro and that can initiate primary orthotopic tumors and metastasis in vivo. Adipocyte and cytokine exposures activate Src, and Src family kinase activity leads to induction of embryonic transcription factors that upregulate miR302b. miR302b induction is Sox2-dependent, promotes cytokine-driven sphere formation, and in turn, stimulates cMYC and SOX2 expression. Src is not only activated by adipocyte or cytokine exposures, it is also required to sustain cytokine induction, since Src inhibitors decrease cytokine production after co-culture. Cytokine upregulation was much greater after co-culture of ER+ breast cancer cells with mature, aromatase positive, adipocytes than with adipocyte stem cells. Cytokine induction was estrogen regulated. The mechanisms of cytokine induction, ER-coactivation and effects of different estrogenic ligands will be presented. Present data illuminate the increased risk of breast cancer after menopause, particularly in obese women and the increased breast cancer mortality with obesity: cancer cell invasion into local fat, in the presence of high local aromatase and intracellular estrogen would establish feed-forward loops to activate Src, maintain pro-inflammatory cytokine production and increase tumor initiating cell abundance, tumor growth and metastasis. These data link obesity related pro-inflammatory cytokines to Src activation and cancer initiating cell abundance, and provide a novel rationale for Src inhibitors together with endocrine therapy for breast cancer. Citation Format: Slingerland J, Picon-Ruiz M, Jang K, Morata-Tarifa C, Pan C, Besser A, Kim M, Ince TA, Howard GA, El-Ashry D. Estrogens contribute to cytokine upregulation and cancer stem cell recruitment upon breast cancer contact with mature human mammary adipocytes: Effects of estrogen type and adipocyte donor weight. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-03-02.