Abstract 3820: Inhibition of M1 macrophages may aid the conversion process to M2, which may aid tumor survival and growth

Abstract

Abstract Macrophages perform a variety of functions, from phagocytosis to the repair and remodeling of damaged tissues. Two phenotypes have been proposed: M1 and M2. The M1 macrophage performs phagocytosis of tumor cells and releases pro-inflammatory cytokines. The M2 macrophage acts as a support cell by promoting the healing of damaged cells by angiogenesis and tissue remodeling. The transition from M1 to M2 may be facilitated by tumor environments. To further study the relationship between cancer and macrophages we developed a live-cell migration assay, which measures cancer's ability to recruit macrophages. We hypothesize that cancer cell lines have varied abilities to recruit macrophages and convert them into M2, and that this ability corresponds to the aggressiveness of the cell line. Macrophages were derived from the human mononuclear phagocyte cell line U937, after addition of phorbol 12-myristate 13-acetate (PMA). These U937 cells were incubated with three adenocarcinomas of varying aggressivity. The adenocarcinomas were MDA-MB-435, MDA-MB-231, and MCF7. The U937 cells were separated from the three cell lines by 3.0 µm trans-permeable polycarbonate membranes (Corning Inc.) which allowed the U937 cells to migrate to the cell lines. After 1 hour non-migratory U937 cells were isolated and counted by means of a hemocytometer. The control without cancer caused 73.86% of U937 cells to remain, MDA-MB-435 69.28% (N=24, P=0.29), MCF7 61.09% (N=24, P<0.01), and MDA-MB-231 55.83% (N=24, P<0.01). This data was then compared with expression levels of macrophage Migration Inhibition Factor (MIF) analyzed from Real Time PCR data. These samples consisted of monocytes, from human blood, which were co-incubated with the cell lines for 48 hours. The cells were separated by 0.4 µm trans-permeable polycarbonate membranes (Corning Inc.) to prevent cells from coming into contact and allowing signal exchange. The RT-PCR data correlated with the migration data. The amount of MIF increased 7.56 fold, (N=9) in MDA-MB-435 when compared to controls, 3.13 fold for MCF7 (N=9), and 1.33 fold for MDA- MB-231 (N=9). This data suggests that the more aggressive the cancer the more MIF emitted and the greater the potential to inhibit macrophages. Previous studies have shown Interleukin-10, (IL-10), IL-6, IL-4, and prostaglandin F2 (PGF2) to be released from tumors and inhibit the cytotoxic activity of macrophages. This exposure to IL-10 has been suggested to convert M1 macrophages to a M2 phenotype. The migration inhibition observed from this study might be the initial step in the conversion process from M1 to M2. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3820.