Abstract PS16-24: Mechanisms underlying obesity-induced enrichment of stem-like breast cancer cells

Abstract

Abstract Background: Breast cancer represents the most common nonskin malignancy in women worldwide, and most deaths result from metastatic dissemination of the disease. At the same time, studies indicate that obesity induces a stem cell-like phenotype, required for tumor metastases and associated with cancer progression and mortality. Although the precise mechanism behind this reprogramming event remains to be elucidated, preliminary data from our lab demonstrate that the epithelial-mesenchymal transition (EMT) associated with obese conditions is linked to IL-6 mechanistically. Because IL-6 cannot be targeted clinically, it will be of the utmost importance to identify downstream effectors of this IL-6-mediated response. This said, we hypothesize that increased levels of IL-6 in obese conditions are at least partially responsible for inducing a stem cell-like phenotype in breast cancer cells through activation of the Akt-mTOR pathway.Methods: MCF-7 and T47D breast cancer cells will be exposed to sera pooled from normoweight (BMI<25 kg/m2) or obese (BMI≥30 kg/m2) women as an in vitro model of the systemic inflammation present in obesity. The cells will then be assessed for changes in expression of genes and proteins involved in induction of EMT using qPCR and western immunoblotting, respectively. Finally, flow cytometry will be used to confirm establishment of an EMT phenotype with measurement of the stem cell markers CD24 and CD44.Results: Our gene expression analyses confirm that obese conditions increase expression of EMT-related genes, including those encoding the transcription factors Snail and Twist. Our flow cytometric analyses also indicate an increase in the stem cell population following a 10-day IL-6 exposure. Additionally, supplementation of IL-6 to non-obese sera increased expression of Twist and Snail in breast cancer cells, while inhibition of IL-6 in obese sera reduced expression of these transcription factors. Finally, western blot analyses demonstrate mechanistic involvement of the Akt-mTOR pathway.Conclusions: These data contribute to our understanding of the means by which obesity induces a stem-like phenotype in breast cancer cells and will ultimately bring light to a therapeutic target that can be used to modulate IL-6-induced activation of the Akt-mTOR signaling pathway leading to an EMT phenotype in obese conditions. Citation Format: Shannon Mayberry, Brittany Harlow, Elizabeth Eichman, Christopher Hsu, Linda deGraffenried. Mechanisms underlying obesity-induced enrichment of stem-like breast cancer cells [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-24.