Abstract 3355: Are cancer cells redefining macrophages’ aggressiveness
Authors: Elias Inga Jaco, Evita G. Weagel, Nicholas B. Anderson, Wei Meng, Joshua J. Davis, Richard A. Robinson, Kim L. O'Neill
Journal: Cancer Research (2015)

Abstract Breast cancer is one of the deadliest diseases in the United States. One in 5 women will be diagnosed with breast cancer during their lifetime and about 1 in 8 will develop invasive breast cancer. It has been shown that breast tumor's microenvironment contains large amounts of immune cells. In some cases macrophages account for up to 50% of the tumor mass. Macrophages belong to the innate immune response, and are mainly responsible for initiating the inflammatory response and engulfing foreign particles and cellular debris. They respond to multiple signals, which means they can perform a variety of functions ranging from phagocytosis to tissue repair. Classically-activated macrophages, referred as M1, are responsible for a pro-inflammatory response. Alternatively activated macrophages or M2 macrophages secrete anti-inflammatory cytokines, help in tissue repair, and are often involved in angiogenesis. In this project, we studied the effects of MCF-7 and MDA-MB-231 breast cancer cell lines on macrophages. We stimulated U937 cells with phorbol 12-myristate 13-acetate (PMA) for 24 hours. We checked for differentiation, morphology changes, and adhesion at 24 hours. We incubated 500,000 differentiated U937 cells with 500,000 cells (either MCF-7 or MDA-MB-231) or 500uL spent media from either MCF-7 or MDA-MB-231 cells for 48 hours. After the 48 hour incubation period, fluorescent microspheres were added to the macrophages and incubated for 1 hour to allow for phagocytosis. Macrophages were ran in a flow cytometer to quantify microsphere engulfment. We found about 50% decrease in engulfment activity in macrophages exposed to MCF-7 or MDA-MB-231 cells or media. When we analyzed the population of macrophages that engulfed 3+ beads, for MDA-MB-231 treatment, we found a 57% and 79% engulfment reduction in macrophages for media and cells respectively. For the MCF-7 treatment, the population of macrophages that engulfed 3+ beads was reduced 54% and 65.4% for media and cells respectively. We also studied gene expression of these macrophages to account for macrophage phenotype (M1 or M2). We found up-regulation on IL-10, down-regulation on TNF-α, and down-regulation on IL-12 suggesting that macrophages show a M2-like phenotype. This proposes that the tumor microenvironment (including cells, cytokines, cell vesicles, etc.) may be influencing the decrease in macrophage aggressiveness. Further studies will allows us to learn more in depth all of the interaction of cancer cells, their microenvironment, and macrophages. Citation Format: Elias Inga Jaco, Evita G. Weagel, Nicholas B. Anderson, Wei Meng, Joshua J. Davis, Richard A. Robinson, Kim L. O'Neill. Are cancer cells redefining macrophages’ aggressiveness. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3355. doi:10.1158/1538-7445.AM2015-3355