Tumor stromal alternatively activated macrophages are important determinants of anti-tumor T lymphocyte responses, intratumoral neovascularization and metastatic dissemination. Our recent efforts to investigate the mechanism of macrophage migration inhibitory factor (MIF) in antagonizing anti-melanoma immune responses reveal that macrophage-derived MIF participates in macrophage alternative activation in melanoma-bearing mice. Both peripheral and tumor-associated macrophages (TAMs) isolated from melanoma bearing MIF-deficient mice display elevated pro-inflammatory cytokine expression and reduced anti-inflammatory, immunosuppressive and pro-angiogenic gene products compared to macrophages from tumor bearing MIF wildtype mice. Moreover, TAMs and myeloid-derived suppressor cells (MDSCs) from MIF-deficient mice exhibit reduced T lymphocyte immunosuppressive activities than do those from their wildtype littermates. Corresponding with reduced tumor immunosuppression and neoangiogenic potential by TAMs, MIF-deficiency confers protection against transplantable subcutaneous melanoma outgrowth and melanoma lung metastatic colonization. Finally, we report for the first time that our previously discovered MIF small molecule antagonist, 4-iodo-6-phenylpyrimidine (4-IPP), recapitulates MIF-deficiency in vitro and in vivo and attenuates tumor polarized macrophage alternative activation, immunosuppression, neoangiogenesis and melanoma tumor outgrowth. These studies describe an important functional contribution by MIF to tumor-associated macrophage alternative activation and provide justification for immunotherapeutic targeting of MIF in melanoma patients.

Porphyromonas gingivalis, one of the causative agents of adult periodontitis, develops biofilm microcolonies on substrata of Streptococcus gordonii but not on Streptococcus mutans. P. gingivalis genome microarrays were used to identify genes differentially regulated during accretion of P. gingivalis in heterotypic biofilms with S. gordonii. Thirty-three genes showed up-or downregulation by array analysis, and differential expression was confirmed by quantitative reverse transcription-PCR. The functions of the regulated genes were predominantly related to metabolism and energy production. In addition, many of the genes have no current known function. The roles of two upregulated genes, ftsH (PG0047) encoding an ATP-dependent zinc metallopeptidase and ptpA (PG1641) encoding a putative tyrosine phosphatase, were investigated further by mutational analysis. Strains with mutations in these genes developed more abundant biofilms with S. gordonii than the parental strain developed. ftsH and ptpA may thus participate in a regulatory network that constrains P. gingivalis accumulation in heterotypic biofilms. This study provided a global analysis of P. gingivalis transcriptional responses in an oral microbial community and also provided insight into the regulation of heterotypic biofilm development.Periodontal diseases are a group of infections characterized by destruction of the supporting structures of the teeth. Porphyromonas gingivalis is a gram-negative anaerobe that is an important pathogen in severe manifestations of these diseases (15,41). With regard to the disease process, the primary ecological niche of P. gingivalis is in the subgingival area, where toxic products, such as proteases, can readily access the periodontal tissues. However, initial colonization of the oral cavity by P. gingivalis involves attachment to sites remote from the subgingival area, including the supragingival tooth surface (28,39,43,47,57,58). Indeed, introduction of P. gingivalis into the mouths of human volunteers results in localization almost exclusively on supragingival surfaces (39). The bacterial inhabitants of the supragingival tooth surface comprise a complex multispecies biofilm (42), and numerous in vitro studies have demonstrated the ability of P. gingivalis to attach to common constituents of the supragingival biofilm, including Actinomyces species and oral streptococci (12, 35). The molecular basis of P. gingivalis adhesion to Streptococcus gordonii has been investigated in some detail and has been shown to be multivalent (3,4,23,24,45). The P. gingivalis long fimbriae (FimA) bind to glyceraldehyde-3-phosphate dehydrogenase present on the streptococcal surface (27). In addition, the P. gingivalis short fimbriae (Mfa) engage the streptococcal SspA/B (antigen I/II) adhesins (33) through an approximately 80-amino-acid binding epitope of SspA/B termed BAR (11). Coadhesion mediated through these effectors is required for P. gingivalis to accumulate in a heterotypic biofilm with S. gordonii (23).In contrast to the synergistic rela...

Highly aggressive cancers “entrain” innate and adaptive immune cells to suppress anti-tumor lymphocyte responses. Circulating myeloid-derived suppressor cells (MDSCs) constitute the bulk of monocytic immunosuppressive activity in late stage melanoma patients. Previous studies revealed that monocyte-derived macrophage migration inhibitory factor (MIF) is necessary for the immune suppressive function of tumor-associated macrophages (TAMs) and MDSCs in mouse models of melanoma. In the current study we sought to determine whether MIF contributes to human melanoma MDSC induction and T-cell immunosuppression using melanoma patient-derived MDSCs and an ex vivo co-culture model of human melanoma-induced MDSC. We now report that circulating MDSCs isolated from late stage melanoma patients are reliant upon MIF for suppression of antigen-independent T-cell activation and that MIF is necessary for maximal reactive oxygen species (ROS) generation in these cells. Moreover, inhibition of MIF results in a functional reversion from immune suppressive MDSC to an immunostimulatory dendritic cell (DC)-like phenotype that is at least partly due to reductions in MDSC prostaglandin E2 (PGE2). These findings indicate that monocyte-derived MIF is centrally involved in human monocytic MDSC induction/immune suppressive function and that therapeutic targeting of MIF may provide a novel means of inducing anti-tumor DC responses in late stage melanoma patients.