Mast Cell Accumulation in Glioblastoma with a Potential Role for Stem Cell Factor and Chemokine CXCL12

Glioblastoma multiforme (GBM) is the most common and malignant form of glioma with high mortality and no cure. Many human cancers maintain a complex inflammatory program triggering rapid recruitment of inflammatory cells, including mast cells (MCs), to the tumor site. However, the potential contribution of MCs in glioma has not been addressed previously. Here we report for the first time that MCs infiltrate KRas+Akt-induced gliomas, using the RCAS/TV-a system, where KRas and Akt are transduced by RCAS into the brains of neonatal Gtv-a- or Ntv-a transgenic mice lacking Ink4a or Arf. The most abundant MC infiltration was observed in high-grade gliomas of Arf−/− mice. MC accumulation could be localized to the vicinity of glioma-associated vessels but also within the tumor mass. Importantly, proliferating MCs were detected, suggesting that the MC accumulation was caused by local expansion of the MC population. In line with these findings, strong expression of stem cell factor (SCF), i.e. the main MC growth factor, was detected, in particular around tumor blood vessels. Further, glioma cells expressed the MC chemotaxin CXCL12 and MCs expressed the corresponding receptor, i.e. CXCR4, suggesting that MCs could be attracted to the tumor through the CXCL12/CXCR4 axis. Supporting a role for MCs in glioma, strong MC infiltration was detected in human glioma, where GBMs contained significantly higher MC numbers than grade II tumors did. Moreover, human GBMs were positive for CXCL12 and the infiltrating MCs were positive for CXCR4. In conclusion, we provide the first evidence for a role for MCs in glioma

Dissecting cell-type-specific metabolism in pancreatic ductal adenocarcinoma.

Tumors are composed of many different cell types including cancer cells, fibroblasts, and immune cells. Dissecting functional metabolic differences between cell types within a mixed population can be challenging due to the rapid turnover of metabolites relative to the time needed to isolate cells. To overcome this challenge, we traced isotope-labeled nutrients into macromolecules that turn over more slowly than metabolites. This approach was used to assess differences between cancer cell and fibroblast metabolism in murine pancreatic cancer organoid-fibroblast co-cultures and tumors. Pancreatic cancer cells exhibited increased pyruvate carboxylation relative to fibroblasts, and this flux depended on both pyruvate carboxylase and malic enzyme 1 activity. Consequently, expression of both enzymes in cancer cells was necessary for organoid and tumor growth, demonstrating that dissecting the metabolism of specific cell populations within heterogeneous systems can identify dependencies that may not be evident from studying isolated cells in culture or bulk tissue

PDGF and PDGF receptors in glioma

The family of platelet-derived growth factors (PDGFs) plays a number of critical roles in normal embryonic development, cellular differentiation, and response to tissue damage. Not surprisingly, as it is a multi-faceted regulatory system, numerous pathological conditions are associated with aberrant activity of the PDGFs and their receptors. As we and others have shown, human gliomas, especially glioblastoma, express all PDGF ligands and both the two cell surface receptors, PDGFR-α and -β. The cellular distribution of these proteins in tumors indicates that glial tumor cells are stimulated via PDGF/PDGFR-α autocrine and paracrine loops, while tumor vessels are stimulated via the PDGFR-β. Here we summarize the initial discoveries on the role of PDGF and PDGF receptors in gliomas and provide a brief overview of what is known in this field

The human serum protein C4b-binding protein inhibits pancreatic IAPP-induced inflammasome activation

Aims/hypothesis: Inflammasome activation and subsequent IL-1 beta production is a driver of islet pathology in type 2 diabetes. Oligomers, but not mature amyloid fibrils, of human islet amyloid polypeptide (IAPP), which is co-secreted with insulin, trigger NOD-like receptor pyrin domain containing-3 (NLRP3) inflammasome activation. C4b-binding protein (C4BP), present in serum, binds to IAPP and affects transition of IAPP monomers and oligomers to amyloid fibrils. We therefore hypothesised that C4BP inhibits IAPP-mediated inflammasome activation and IL-1 beta production. Methods: Macrophages were exposed to IAPP in the presence or absence of plasma-purified human C4BP, and inflammasome activation was assessed by IL-1 beta secretion as detected by ELISA and reporter cell lines. IAPP fibrillation was assessed by thioflavin T assay. Uptake of IAPP-C4BP complexes and their effects on phagolysosomal stability were assessed by flow cytometry and confocal microscopy. The effect of C4BP regulation of IAPP-mediated inflammasome activation on beta cell function was assessed using a clonal rat beta cell line. Immunohistochemistry was used to examine the association of IAPP amyloid deposits and macrophage infiltration in isolated human and mouse pancreatic islets, and expression of C4BP from isolated human pancreatic islets was assessed by quantitative PCR, immunohistochemistry and western blot. Results: C4BP significantly inhibited IAPP-mediated IL-1 beta secretion from primed macrophages at physiological concentrations in a dose-dependent manner. C4BP bound to and was internalised together with IAPP. C4BP did not affect IAPP uptake into phagolysosomal compartments, although it did inhibit its formation into amyloid fibrils. The loss of macrophage phagolysosomal integrity induced by IAPP incubation was inhibited by co-incubation with C4BP. Supernatant fractions from macrophages activated with IAPP inhibited both insulin secretion and viability of clonal beta cells in an IL-1 beta-dependent manner but the presence of C4BP during macrophage IAPP incubation rescued beta cell function and viability. In human and mouse islets, the presence of amyloid deposits correlated with higher numbers of infiltrating macrophages. Isolated human islets expressed and secreted C4BP, which increased with addition of IL-1 beta. Conclusions/interpretation: IAPP deposition is associated with inflammatory cell infiltrates in pancreatic islets. C4BP blocks IAPP-induced inflammasome activation by preventing the loss of macrophage phagolysosomal integrity required for NLRP3 activation. The consequence of this is the preservation of beta cell function and viability. C4BP is secreted directly from human pancreatic islets and this increases in response to inflammatory cytokines. We therefore propose that C4BP acts as an extracellular chaperone protein that limits the proinflammatory effects of IAPP

Dissecting cell-type-specific metabolism in pancreatic ductal adenocarcinoma

Funder: Jane Coffin Childs Memorial Fund for Medical Research; FundRef: http://dx.doi.org/10.13039/100001033Funder: Swedish Foundation for Strategic Research; FundRef: http://dx.doi.org/10.13039/501100001729Funder: Knut and Alice Wallenberg Foundation; FundRef: http://dx.doi.org/10.13039/501100004063Funder: Barbro Osher Pro Suecia Foundation; FundRef: http://dx.doi.org/10.13039/100008483Funder: Howard Hughes Medical Institute; FundRef: http://dx.doi.org/10.13039/100000011Funder: NIHR Cambridge BRCFunder: Lustgarten Foundation; FundRef: http://dx.doi.org/10.13039/100005979Funder: Stand Up To Cancer; FundRef: http://dx.doi.org/10.13039/100009730Funder: MIT Center for Precision Cancer MedicineFunder: Ludwig Center at MITFunder: Emerald FoundationTumors are composed of many different cell types including cancer cells, fibroblasts, and immune cells. Dissecting functional metabolic differences between cell types within a mixed population can be challenging due to the rapid turnover of metabolites relative to the time needed to isolate cells. To overcome this challenge, we traced isotope-labeled nutrients into macromolecules that turn over more slowly than metabolites. This approach was used to assess differences between cancer cell and fibroblast metabolism in murine pancreatic cancer organoid-fibroblast co-cultures and tumors. Pancreatic cancer cells exhibited increased pyruvate carboxylation relative to fibroblasts, and this flux depended on both pyruvate carboxylase and malic enzyme 1 activity. Consequently, expression of both enzymes in cancer cells was necessary for organoid and tumor growth, demonstrating that dissecting the metabolism of specific cell populations within heterogeneous systems can identify dependencies that may not be evident from studying isolated cells in culture or bulk tissue

MC distribution in the mouse RCAS-<i>KRas</i>+RCAS-<i>Akt</i> induced brain tumors.

<p>(<b>A</b>) Immunofluorescence staining for endothelial cell marker CD31 and MC tryptase mMCP-6 in <i>Ntv-a Arf−/−</i> and <i>Gtv-a Arf−/−</i> mouse brain tumors revealed perivascular localization of MCs. Lower panel: quantification of perivascular MCs in mouse brain tumors revealed about 50% in the corresponding objective fields with no difference between <i>Ntv-a Arf−/−</i> (n = 5) and <i>Gtv-a Arf−/−</i> (n = 5). Error bars show SD. Scale bar = 50 µM. (<b>B</b>) Immunohistochemical analysis for SCF expression revealing marked expression of SCF in the glioma vascular structures in both <i>Ntv-a Arf−/−</i> and <i>Gtv-a Arf−/−</i> mice (indicated by blue arrows). Expression of SCF was also observed in MC granules (indicated by red arrows). Lower panel: quantification of total absolute intensity signal for SCF revealed statistically significant difference between tumor and nontumor areas of the objective fields in both <i>Ntv-a Arf−/−</i> and <i>Gtv-a Arf−/−</i> mouse brain tumors (* p<0.05). Error bars show SD. Scale bar = 50 µM.</p

CXCL12 and CXCR4 expression in mouse RCAS-<i>KRas</i>+RCAS-<i>Akt</i> induced gliomas.

<p>Immunofluorescence staining for CXCL12 and CXCR4 was performed in both <i>Ntv-a Arf−/−</i> and <i>Gtv-a Arf−/−</i> mouse gliomas. The quantification of intensity signal for CXCL12 (lower left panel) and CXCR4 (lower right panel) revealed statistically significant difference between tumor and nontumor areas of the objective fields in both <i>Ntv-a Arf−/−</i> and <i>Gtv-a Arf−/−</i> mouse brain tumors (* p<0.05). Error bars show SD. Scale bar = 50 µM.</p