Glioblastoma multiforme (GBM) comprises several molecular subtypes including proneural GBM. Most therapeutic approaches targeting glioma cells have failed. An alternative strategy is to target cells in the glioma microenvironment, such as tumor-associated macrophages and microglia (TAMs). Macrophages depend upon colony stimulating factor (CSF)-1 for differentiation and survival. A CSF-1R inhibitor was used to target TAMs in a mouse proneural GBM model, which dramatically increased survival, and regressed established tumors. CSF-1R blockade additionally slowed intracranial growth of patient-derived glioma xenografts. Surprisingly, TAMs were not depleted in treated mice. Instead, glioma-secreted factors including GM-CSF and IFN-γ facilitated TAM survival in the context of CSF-1R inhibition. Alternatively activated/ M2 macrophage markers decreased in surviving TAMs, consistent with impaired tumor-promoting functions. These gene signatures were associated with enhanced survival in proneural GBM patients. Our results identify TAMs as a promising therapeutic target for proneural gliomas, and establish the translational potential of CSF-1R inhibition for GBM.

Macrophages accumulate with glioblastoma multiforme (GBM) progression, and can be targeted via inhibition of colony stimulating factor-1 receptor (CSF-1R) to regress high-grade tumors in animal models of this cancer. However, whether and how resistance emerges in response to sustained CSF-1R blockade is unknown. We show that while overall survival is significantly prolonged, tumors recur in >50% of mice. Gliomas re-establish sensitivity to CSF-1R inhibition upon transplantation, indicating that resistance is tumor microenvironment-driven. Phosphatidylinositol 3-kinase (PI3K) pathway activity was elevated in recurrent GBM, driven by macrophage-derived insulin-like growth factor (IGF-1) and tumor cell IGF-1 receptor (IGF-1R). Combining IGF-1R or PI3K blockade with CSF-1R inhibition in recurrent tumors significantly prolonged overall survival. Our findings thus reveal a potential therapeutic approach for treating resistance to CSF-1R inhibitors.

Obesity is associated with chronic, low-grade inflammation, which can disrupt homeostasis within tissue microenvironments. Given the correlation between obesity and relative risk of death from cancer, we investigated whether obesity-associated inflammation promotes metastatic progression. We demonstrate that obesity causes lung neutrophilia in otherwise normal mice, which is further exacerbated by the presence of a primary tumour. The increase in lung neutrophils translates to increased breast cancer metastasis to this site, in a GM-CSF- and IL5-dependent manner. Importantly, weight loss is sufficient to reverse this effect, and reduce serum levels of GM-CSF and IL5 in both mouse models and humans. Our data indicate that special consideration of the obese patient population is critical for effective management of cancer progression.

Purpose Chronic pelvic pain syndrome (CPPS) accounts for 90% of all chronic prostatitis but has an unknown pathogenesis. In this study, we sought to understand the role of mast cells and nerve growth factor (NGF) in chronic pelvic pain. Materials and Methods Expressed prostatic secretions in men with CPPS and controls were tested for the presence of mast cell tryptase and NGF. Mast cell numbers, activation status and NGF expression were examined in the NOD/ShiLtJ experimental autoimmune prostatitis model (EAP) as well as in mast cell deficient KitW-sh/KitW-sh mice. Tactile allodynia was quantified using Von Frey filaments as a measure of pelvic pain behavior. Inhibitors of mast cell degranulation, histamine receptor antagonists and anti-NGF neutralizing antibodies were tested for reducing pelvic pain behavior. Results Men with CPPS demonstrated increased mast cell tryptase and NGF in expressed prostatic secretions. In the EAP model, increased total and activated mast cells were observed in the prostate. Mast cell deficient KitW-sh/KitW-sh mice showed attenuated pelvic pain behavior but no difference in inflammatory infiltrates in the prostate from controls. EAP mice also demonstrated increased intraprostatic NGF expression compared to KitW-sh/KitW-sh mice. Treatment of EAP with a mast cell stabilizer in combination with a histamine 1 receptor antagonist resulted in a synergistic reduction in chronic pelvic pain. In contrast, neutralization of NGF in vivo did not result in pain relief. Conclusions These results suggest that mast cells are important mediators of chronic pelvic pain in EAP and may be potential targets for therapeutic intervention in CP/CPPS.

During the process of tumor progression, cancer cells can produce the requisite growth-and invasion-promoting factors and can also rely on noncancerous cells in the tumor microenvironment as an alternative, cell-extrinsic source. However, whether the cellular source influences the function of such tumor-promoting factors remains an open question. Here, we examined the roles of the cathepsin Z (CtsZ) protease, which is provided by both cancer cells and macrophages in pancreatic neuroendocrine tumors in humans and mice. We found that tumor proliferation was exclusively regulated by cancer cell-intrinsic functions of CtsZ, whereas tumor invasion required contributions from both macrophages and cancer cells. Interestingly, several of the tumor-promoting functions of CtsZ were not dependent on its described catalytic activity but instead were mediated via the Arg-Gly-Asp (RGD) motif in the enzyme prodomain, which regulated interactions with integrins and the extracellular matrix. Together, these results underscore the complexity of interactions within the tumor microenvironment and indicate that cellular source can indeed impact molecular function.[Keywords: cell invasion; cell migration; tumor microenvironment; protease] Supplemental material is available for this article. Received July 26, 2014; revised version accepted August 29, 2014. Tumors arise in complex tissue microenvironments in which a multitude of different noncancerous cell types can potently regulate disease initiation and progression (Hanahan and Coussens 2012;Quail and Joyce 2013). In addition, interactions with the extracellular matrix (ECM) are critical for modulating cell behavior, including enhancing cell survival and promoting invasion via ECM turnover and proteolysis (Lu et al. 2012;Sevenich and Joyce 2014). The ECM is a heterogeneous mix of proteins and polysaccharides, including different collagens, laminins, fibronectin, and heparan sulfate proteoglycans, which form an intricate network that confers tissue structure and regulates growth factor availability (Hynes and Naba 2012;Lu et al. 2012). Integrins are central in mediating interactions between cells and the surrounding ECM, and integrin engagement at the cell surface results in activation of downstream signaling nodes, including focal adhesion kinase (FAK) and Src kinase, to promote cancer cell proliferation, survival, migration, and invasion (Desgrosellier and Cheresh 2010;Huttenlocher and Horwitz 2011;Moreno-Layseca and Streuli 2014).Among the noncancerous cell types that modulate tumorigenesis, tumor-associated macrophages (TAMs) have emerged as critical regulators of tumor progression (Biswas et al. 2013;Noy and Pollard 2014). This is particularly evident in tumor invasion, as TAMs provide a major source of proteases that modulate the ECM (Joyce and Pollard 2009). In determining the mechanisms by which TAMs promote different tumorigenic processes, the focus to date has been predominantly centered on identifying factors that are TAM-specific or TAM-enriched, which are not necessa...