Tumour tissue is infiltrated by myeloid cells that are reprogrammed into alternatively activated/regenerative (M2) macrophages. The contribution of major signalling pathways and their ...modulators/targets involved in the macrophage reprogramming is poorly known. Glioblastoma (malignant brain tumour) attracts and reprograms brain-resident microglia and peripheral macrophages into cells that increase invasion, angiogenesis and suppress antitumour immunity. Using a 'function-first' approach and glioma secretome proteomics we identified osteopontin and lactadherin as proteins that cooperatively activate amoeboid transformation, phagocytosis and motility of primary microglia cultures via integrins and FAK-Akt (focal adhesion kinase-Akt) signalling. A synthetic peptide interfering with integrin ligands blocks glioma-microglia communication, functional activation and M2 gene expression. We found that osteopontin/secreted phosphoprotein 1 (Spp1) produced by non-transformed cells acts as a proinflammatory factor inducing inflammatory signalling and M1 genes, and counteracts the action of lactadherin. Using constructs encoding functional mutants of osteopontin, we demonstrated sequential processing of Spp1 by thrombin and matrix metalloproteinase-3 and/or -7 (MMP-3 and/or -7) in glioma cells, which generates a microglia-activating form devoid of the inflammatory activity, while retaining the M2 reprogramming potential. A similar form of osteopontin is secreted by human glioma cells but not normal human astrocytes. Knockdown of osteopontin or lactadherin in glioma cells reduces intracranial glioma growth, blocks amoeboid transformation of myeloid cells and affects M2 reprogramming of microglia/macrophages. Our findings demonstrate how glioma cells misuse macrophage-activating signals and redesign primarily proinflammatory signals towards their advantage to induce M2 reprogramming of tumour-infiltrating brain macrophages.
P142 Pszczółkowska, D; Ellert-Miklaszewska, A; Gieryng, A ...
European journal of cancer supplements,
11/2015, Letnik:
13, Številka:
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Malignant gliomas are fast-growing, heterogeneous and invasive brain tumors strongly infiltrated by non-tumor cells. Glioma attracts variety of immune cells, in particular microglia/macrophages and ...re-program these cells into immunosuppressive, tumor-supporting cells. Factors responsible for pro-invasive macrophage polarization and shaping tumor microenvironment in tumor-supporting manner are poorly known. We analyzed glioma secretome using proteomical approach and identified lactadherin (Mfge8) and osteopontin (Spp1) in microglia-activating fractions. Both osteopontin and lactadherin are αvβ 3/ αvβ 5 integrin ligands able to interact with receptors present on microglia and macrophages and thus could be involved in pro-invasive polarization of microglia/macrophages. Moreover, both Spp1 and Mfge8 are overexpressed in glioma cells, but not in non-transformed astrocytes. C6 glioma cells stably expressing shRNA specific to lactadherin (shMfge8), osteopontin (shSpp1) and negative shRNA (shNeg) were implanted into striatum of Wistar rats. There was no difference in proliferation and viability of C6 glioma cells, cells stably expressing shRNA specific to lactadherin, ostopontin and negative shRNA in vitro, that demonstrates the negligible effect of autocrine production of both protein on tumor cell growth. Knockdown of Spp1 and Mfge8 resulted in significant reduction of tumor volume in rat model of glioma. Immunochemical analysis of brain sections revealed similar numbers of infiltrating microglia/macrophages (Iba1 staining), but the reduced number of ameboid, arginase 1 expressing cells in Mfge8 – depleted tumor. Treatment of endothelial cells with rhMFGE8 revealed significant effect of that protein on angiogenesis in vitro, however lactadherin-depleted tumors do not exhibit reduced blood vessel density in rat glioma model. FACS analysis showed that silencing of Spp1 does not affect total number of CD11b-positive cells, but strongly modulates microenvironment by leading to significant changes in percentage of Tc and Treg cells infiltrating tumor-bearing hemisphere. Our results suggest that glioma-derived integrin ligands are important factor in polarization of glioma infiltrating microglia/macrophages into the pro-invasive phenotype and its targeting could be a new therapeutic strategy.
Cannabinoids were shown to induce apoptosis of glioma cells in vitro and tumor regression in vivo, but mechanisms of their antiproliferative action remain elusive. In the present studies, C6 cells ...were exposed to a synthetic cannabinoid, WIN 55,212-2, which produced down-regulation of the Akt and Erk signalling pathways prior to appearance of any sign of apoptosis. We hypothesized that cannabinoid-induced cell death may be mediated by a Bcl-2 family member—Bad, whose function is hampered by these kinases due to control of its phosphorylation state. Using Western blot analysis, we found that levels of phosphorylated Bad, but not total Bad protein, decreased under exposure to WIN 55,212-2. WIN 55,212-2 treatment further resulted in mitochondrial depolarization and activation of caspase cascade. Thus, we suggest that the increase of proapoptotic Bad activity is an important link between the inhibition of survival pathways and an onset of execution phase of cannabinoid-induced glioma cell death.
Abstract The efficacy of cannabinoids against high-grade glioma in animal models, mediated by two specific receptors, CB1 and CB2, raised promises for targeted treatment of the most frequent and ...malignant primary brain tumors. Unlike the abundantly expressed CB1, the CB2 receptor shows a restricted distribution in normal brain. Although brain tumors constitute the second most common malignancy in children and the prevalence of histological types of brain tumors vary significantly between the adult and pediatric populations, cannabinoid receptor expression in pediatric tumors remains unknown. In the present study, we compared the expression of the CB2 receptor in paraffin-embedded sections from primary brain tumors of adult and pediatric patients. Most glioblastomas expressed very high levels of CB2 receptors and the expression correlated with tumor grade. Interestingly, some benign pediatric astrocytic tumors, such as subependymal giant cell astrocytoma (SEGA), which may occasionally cause mortality owing to progressive growth, also displayed high CB2 immunoreactivity. The high levels of CB2 expression would predestine those tumors to be vulnerable to cannabinoid treatment. In contrast, all examined cases of embryonal tumors (medulloblastoma and S-PNET), the most frequently diagnosed malignant brain tumors in childhood, showed no or trace CB2 immunoreactivity. Our results suggest that the CB2 receptor expression depends primarily on the histopathological origin of the brain tumor cells and differentiation state, reflecting the tumor grade.
Tumour tissue is infiltrated by myeloid cells that are reprogrammed into alternatively activated/regenerative (M2) macrophages. The contribution of major signalling pathways and their ...modulators/targets involved in the macrophage reprogramming is poorly known. Glioblastoma (malignant brain tumour) attracts and reprograms brain-resident microglia and peripheral macrophages into cells that increase invasion, angiogenesis and suppress antitumour immunity. Using a 'function-first' approach and glioma secretome proteomics we identified osteopontin and lactadherin as proteins that cooperatively activate amoeboid transformation, phagocytosis and motility of primary microglia cultures via integrins and FAK-Akt (focal adhesion kinase-Akt) signalling. A synthetic peptide interfering with integrin ligands blocks glioma-microglia communication, functional activation and M2 gene expression. We found that osteopontin/secreted phosphoprotein 1 (Spp1) produced by non-transformed cells acts as a proinflammatory factor inducing inflammatory signalling and M1 genes, and counteracts the action of lactadherin. Using constructs encoding functional mutants of osteopontin, we demonstrated sequential processing of Spp1 by thrombin and matrix metalloproteinase-3 and/or -7 (MMP-3 and/or -7) in glioma cells, which generates a microglia-activating form devoid of the inflammatory activity, while retaining the M2 reprogramming potential. A similar form of osteopontin is secreted by human glioma cells but not normal human astrocytes. Knockdown of osteopontin or lactadherin in glioma cells reduces intracranial glioma growth, blocks amoeboid transformation of myeloid cells and affects M2 reprogramming of microglia/macrophages. Our findings demonstrate how glioma cells misuse macrophage-activating signals and redesign primarily proinflammatory signals towards their advantage to induce M2 reprogramming of tumour-infiltrating brain macrophages. Oncogene (2016) 35, 6366-6377; doi: 10.1038/onc.2016.55; published online 4 April 2016
Malignant gliomas are highly resistant to current therapeutic approaches due to genetic alterations rendering them resistant to cell death. CK2, a ubiquitous and constitutively active ...serine/threonine kinase, frequently elevated in tumors, contributes to enhanced cell proliferation and resistance to apoptosis. Inhibition of CK2 expression or treatment with inhibitors of CK2 affected survival or induced apoptosis in various cancer cells. Here we compared cytotoxic effects of well-known and new CK2 inhibitors: 4,5,6,7-tetrabromo-1H-benzotriazole (TBB), 4,5,6,7-tetrabromo-1H-benzimidazole (TBI), 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT), the related 3-(4,5,6,7-tetrabromo-1H-benzimidazol-1-yl)propan-1-ol (MB001), 3-(4,5,6,7-tetrabromo-1H-1,2,3-benzotriazol-1-yl) propan-1-ol (MB002), 3-(4,5,6,7-tetrabromo-2H-1,2,3-benzotriazol-2-yl)propan-1-ol (MB003) and also structurally similar to above compounds pentabromobenzylisothiourea (ZKK1) and its derivatives (ZKK2-8) on cultured malignant glioma cells. TBI, ZKK1 and MB001-3 were more effective than TBB in inducing growth arrest and cell death in glioma cells. TBI and ZKK1 strongly induced apoptotic death involving caspase 3 and 7 activation followed by PARP cleavage. DMAT strongly upregulated the expression of cytotoxic ligand and its receptor Fas. Structural modifications of ZKK1 largely affected its efficacy: exchange of Br- to Cl- or F-substituents on the pentabromophenyl ring and inclusion of the bulky N-phenyl substituent in thiourea fragment of ZKK1 diminished cytotoxic activity, while N-substitution with short alkyl groups or an allyl group had opposite effects. Interestingly, TBI at moderate dose did not affect viability of non-transformed astrocytes, suggesting some specificity toward tumor cells in cytotoxic action. TBI, DMAT and ZKK1-induced apoptosis associated with caspase cascade activation in human malignant glioblastoma cells with mutated PT53 and PTEN genes. The reported data demonstrate that suitably modified polybromobenzene molecules exhibit a significant cytotoxic potential towards malignant glioblastoma cells.
Malignant gliomas attract resident microglia and macrophages and re-program these cells into pro-invasive, immunosuppressive cells. It results in formation of tumor supportive microenvironment and ...evasion of antitumor responses. The analysis of marker genes in microglia and macrophages infiltrating experimental gliomas indicates different kinetics and functions of various myeloid subpopulations during glioma progression. Signals responsible for recruitment and polarization of tumor infiltrating myeloid cells are poorly known. Proteomic analysis of glioma secretome revealed a presence of osteopontin (SPP1) and lactadherin (MGF-E8) in microglia-activating fractions. Both proteins stimulated microglia via alpha v beta 3 integrin signaling that results in activation of PI-3K/Akt and FAK, enhancement of microglial migration, phagocytosis and transcriptional responses. Inhibition of ligand-integrin interactions with short interfering peptides abolished pro-invasive polarization in glioma-microglia co-cultures. We found that SPP1, highly overexpressed in glioma cells, was specifically processed by sequential thrombin and metalloproteinase-dependent cleavage. This type of processing results in losing SPP1 pro-inflammatory activity leaving intact its pro-tumorigenic activity and does not occur in non-transformed cells. Knockdown of SPP1 in glioma cells strongly reduced growth of intracranial gliomas. The number of infiltrating microglia/macrophages (Iba1+) was not affected, but amoeboid transformation, expression of the alternative phenotype markers and angiogenesis were reduced in SPP1-depleted gliomas. Interestingly, infiltrating Iba1+ cells did not undergo pro-invasive polarization. Moreover, SPP1-depleted tumors were infiltrated with T cytotoxic lymphocytes, while accumulation of T regulatory cells was significantly reduced. The expression of SPP1 is up-regulated in human glioblastoma and inversely correlated with patient's survival. Our findings demonstrate that glioma-derived and specifically processed osteopontin/SPP1 polarizes glioma-infiltrating microglia and contributes to transformation of tumor microenvironment. This defines osteopontin/SPP1 a new biomarker and target for glioma therapy, and shows that targeting glioma-microglia interactions within tumor microenvironment is a promising strategy to fight these tumors. Studies were supported by a grant 2012/04/A/NZ3/00630 from the National Science Center.
Malignant gliomas are fast-growing, heterogeneous and invasive brain tumors strongly infiltrated by non-tumor cells. Glioma attracts variety of immune cells, in particular microglia/macrophages and ...re-program these cells into immunosuppressive, tumor-supporting cells. Factors responsible for pro-invasive macrophage polarization and shaping tumor microenvironment in tumor-supporting manner are poorly known. We analyzed glioma secretome using proteomical approach and identified lactadherin (Mfge8) and osteopontin (Spp1) in microglia-activating fractions. Both osteopontin and lactadherin are αvβ3/αvβ5 integrin ligands able to interact with receptors present on microglia and macrophages and thus could be involved in pro-invasive polarization of microglia/macrophages. Moreover, both Spp1 and Mfge8 are overexpressed in glioma cells, but not in non-transformed astrocytes. C6 glioma cells stably expressing shRNA specific to lactadherin (shMfge8), osteopontin (shSpp1) and negative shRNA (shNeg) were implanted into striatum of Wistar rats. There was no difference in proliferation and viability of C6 glioma cells, cells stably expressing shRNA specific to lactadherin, ostopontin and negative shRNA in vitro, that demonstrates the negligible effect of autocrine production of both protein on tumor cell growth. Knockdown of Spp1 and Mfge8 resulted in significant reduction of tumor volume in rat model of glioma. Immunochemical analysis of brain sections revealed similar numbers of infiltrating microglia/macrophages (Iba1 staining), but the reduced number of ameboid, arginase 1 expressing cells in Mfge8 – depleted tumor. Treatment of endothelial cells with rhMFGE8 revealed significant effect of that protein on angiogenesis in vitro, however lactadherin-depleted tumors do not exhibit reduced blood vessel density in rat glioma model. FACS analysis showed that silencing of Spp1 does not affect total number of CD11b-positive cells, but strongly modulates microenvironment by leading to significant changes in percentage of Tc and Treg cells infiltrating tumor-bearing hemisphere. Our results suggest that glioma-derived integrin ligands are important factor in polarization of glioma infiltrating microglia/macrophages into the pro-invasive phenotype and its targeting could be a new therapeutic strategy.
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