Regulation of tumor associated macrophages by cooperative inflammatory signaling

Tumor associated macrophages show signs of both, classical pro-inflammatory as well as alternative macrophage activation. The aim of this study was to compare TAMs across tumor types, to characterize their phenotype in detail and to identify the signaling nodules involved regulating classical and alternative activation traits. To identify gene expression profiles and pathways differentially activated in tumor-associated macrophages (TAMs) we isolated TAMs from in vivo animal models of EG7 thymoma (n=3), glioma (n=3) and neuroblastoma (n=3) by tumor digestion and subsequent enrichment of CD11b+ cells using Miltenyi magnetic beads. Thymomas grown in WT or Myd88-/- mice (n=5 per group) were used to identify TLR/IL1R dependent signaling in TAMs. RNA extracted from CD11b+ TAMs was analyzed using the Affymetrx HT_MG-430_PM arrays. For in-depth analysis of the role of inflammatory signaling by TNFR1 (Tnfrsf1a) and/or Myd88, EG7 TAM populations A (CD11b+, Ly6G-, Ly6C+, MHCII-) and C (CD11b+, Ly6C-, MHCII+) were isolated by flow cytometric sorting from WT, TNFR1-/-, Myd88flox/flox; Tie2-Cre and TNFR-/-; Myd88flox/flox; Tie2-cre mice and extracted RNA was analyzed by microarray using the Mouse Gene 2.0 GeneChip arrays (n=2 per genotype and population).