Abstract 5533: A RT-PCR study of cytokine expression with macrophages and tumors

Abstract

Abstract Macrophages (MØ) are very important in initiating and directing an immune response. However, it has been noted that when MØ are in the presence of a tumor, they often undergo a change in phenotype. In this environment, MØ will be converted from an aggressive phenotype (M1) to one that promotes tissue remodeling and repair (M2) through a process that is not fully understood. The purpose of this study was to identify which cytokines, in both MØ and cancer cells, show altered expression when the two are in close proximity. To accomplish this, MCF-7 (breast cancer), MDA-MB-231 (breast cancer), MDA-MB-435 (melanoma), and HT29 (colon cancer) cell cultures were grown in prescribed media followed by a 48-hour co-incubation with whole blood MØ. Lipopolysaccharide (LPS) was used as a positive control of an M1-type stimulation. The cytokine levels of both the cancer cells and MØ were then analyzed by quantitative PCR (qPRC) for expression of interleukin-1beta (IL-1β), macrophage migration inhibition factor (MIF), and tumor necrosis factor-alpha (TNF-α). Mathematical calculations were analyzed using a Step One® comparative quantification program and the cytokine expression equation 2⁁-(Δct1- Δct2). MØ IL-1β showed a fold change of 2.76, 1.58, 0.95, 3.09, 10.11 when exposed to MCF-7, MDA-MB-231, MDA-MB-435, and HT29 cells and LPS respectively. These expressions correlated with the aggressiveness of the cancer. Aggressive MDA-MB-435's down regulated IL-1β. Fold change in MIF expression was 3.14, 1.33, 7.56, and 1.22 in MCF-7, MDA-MB-231, MDA-MB-435, and HT29 cells respectively. HT29's had the lowest expression levels suggesting one reason why it's been reported that infiltration of MØ happens properly in colon cancers. Fold expression in MØ expression of TNF-α was 1.34, 1.65, 1.10, and 0.85 with MCF-7, MDA-MB-231, MDA-MB-435, and HT29 cells respectively. An interesting finding that warrants further investigation was in regards to the colon cancer. We observed with interest that the colon cancer line, HT29, caused a decrease in expression of MØ TNF-α. These findings show that colon cancer HT29 decreases TNF-α expression whereas other tested cancer lines did not. This suggests that colon cancers might evade the immune system by regulating MØ TNF-α, an important factor in initiating the caspase-8 regulated apoptotic pathway. These findings suggest that each cancer has an individual method in managing it's microenvironment in respect to MØ. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5533. doi:10.1158/1538-7445.AM2011-5533