A distinct and unique transcriptional programme expressed by tumor-associated macrophages : defective NF-{kappa}B and enhanced IRF-3/STAT1 activation

To identify the molecular basis underlying the functions of tumor-associated macrophages (TAMs), we characterized the gene expression profile of TAMs isolated from a murine fibrosarcoma in comparison with peritoneal macrophages (PECs) and myeloid suppressor cells (MSCs), using a cDNAmicroarray technology. Among the differentially expressed genes, 15 genes relevant to inflammation and immunity were validated by real-time polymerase chain reaction (PCR) and protein production. Resting TAMs showed a characteristic gene expression pattern with higher expression of genes coding for the immunosuppressive cytokine IL-10, phagocytosis-related receptors/molecules (Msr2 and C1q), and inflammatory chemokines (CCL2 and CCL5) as expected, as well as, unexpectedly, IFN-inducible chemokines (CXCL9, CXCL10, CXCL16). Immunohistology confirmed and extended the in vitro analysis by showing that TAMs express M2-associated molecules (eg, IL-10 and MGL1), as well as CCL2, CCL5, CXCL9, CXCL10, and CXCL16, but no appreciable NOS2. Lipopolysaccharide (LPS)-mediated activation of TAMs resulted in defective expression of several proinflammatory cytokines (eg, IL-1β, IL-6, TNF-α) and chemokines (eg, CCL3), as opposed to a strong up-regulation of immunosuppressive cytokines (IL-10, TGFβ) and IFN-inducible chemokines (CCL5, CXCL9, CXCL10, CXCL16). Thus, profiling of TAMs from a murine sarcoma revealed unexpected expression of IFN-inducible chemokines, associated with an M2 phenotype (IL-10high, IL-12low), and divergent regulation of the NF-κB versus the IRF-3/STAT1 pathway.

To identify the molecular basis underlying the functions of Tumor-Associated Macrophages (TAM), we characterized the gene expression profile of TAM isolated from a murine fibrosarcoma in comparison with peritoneal macrophages (PEC) and immature suppressor cells (MSC), using a cDNA microarray technology. Among the differentially expressed genes, 15 genes relevant to inflammation and immunity were validated by real-time PCR and protein production. Resting TAM showed a characteristic gene expression pattern, with higher expression of genes coding for the immunosuppressive cytokine IL-10, phagocytosis-related receptors/molecules (Msr2 and C1q) and inflammatory chemokines (CCL2 and CCL5) as expected, as well as, unexpectedly, IFN-inducible chemokines (CXCL9, CXCL10, CXCL16). Immunohistology confirmed and extended the in vitro analysis by showing that TAM express M2-associated molecules (e.g. IL-10 and MGL1), as well as CCL2, CCL5, CXCL9, CXCL10 and CXCL16, but no appreciable NOS2. Lipopolysaccharide (LPS)-mediated activation of TAM resulted in defective expression of several proinflammatory cytokines (e.g. IL-1beta, IL-6, TNF-alpha) and chemokines (eg. CCL3), as opposed to a strong up-regulation of immunosuppressive cytokines (IL-10, TGFbeta) and IFN-inducible chemokines (CCL5, CXCL9, CXCL10, CXCL16). The TAM functional profile was associated with defective activation of NF-kB but unexpected activation of MyD88-independent IRF-3 and STAT1.Thus, profiling of TAM from a murine sarcoma revealed unexpected expression of IFN-inducible chemokines, associated with an M2 phenotype (IL-10(high), IL-12(low)), and divergent regulation of the NF-kappaB versus the IRF-3/STAT1 pathway.