Abstract 4623: Transcriptional analysis of the functional differences between M1 and M2 macrophages to identify new targets for myeloid cell modulation in pancreatic tumors

Abstract

Abstract Macrophages exhibit dynamic plasticity in their function in response to the accumulating genetic alterations that occur during tumorigenesis, resulting in the establishment of an immune tolerized tumor microenvironment. However, depending on their environmental cues, they can switch between two functional phenotypes: pro-inflammatory/anti-tumorigenic (M1) or anti-inflammatory/pro-tumorigenic (M2). The importance of these two macrophage subsets is well-recognized; however, identifying and distinguishing M1 from M2 macrophages in patient tumors still remains a challenge. Prior studies have utilized transcriptome profiling of artificially skewed M1 and M2 macrophages from healthy donors to identify individual genes or gene clusters unique to each macrophage subset. However, these studies are limited to surface marker expression and gene expression profiles alone to distinguish subsets and lack functional validation of M1 and M2 macrophages. Surface marker and gene expression profiling of human M1 and M2 macrophages provide an incomplete characterization, as functionality is an important feature distinguishing these macrophage subsets. To improve the characterization of M1 and M2 macrophages, we performed a thorough three-step validation of artificially skewed M1 and M2 macrophages from healthy donor monocytes using surface marker expression, gene expression profiling, and multi-analyte ELISA analyses. Using our validation assays, we tested previously published protocols for their efficacy in generating M1 and M2 macrophages. While M1 macrophages using these protocols generated as expected M1 characteristics, M2 macrophages lacked hallmark functional features, particularly IL-10 secretion. This necessitated the generation of an optimized protocol to skew M1 and M2 macrophages that exhibited distinctive surface marker expression, gene expression profiles, and cytokine and chemokine production for their respective subset. We then performed RNA-sequencing to interrogate the transcriptional landscape of functional M1 and M2 macrophages and have found 1,472 transcripts that have at least a two-fold change in differential expression between M1 and M2 macrophages across 4 different donors. These results represent the most in-depth characterization of human M1 and M2 macrophages and provide insights into better biomarkers and targets for novel immunotherapy approaches. Citation Format: Kimberline R. Yang, Todd D. Armstrong, Elizabeth M. Jaffee. Transcriptional analysis of the functional differences between M1 and M2 macrophages to identify new targets for myeloid cell modulation in pancreatic tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4623. doi:10.1158/1538-7445.AM2017-4623