Pheochromocytomas and paragangliomas are neuroendocrine tumors that occur in the context of inherited cancer syndromes in ∼30% of cases and are linked to germline mutations in the VHL, RET, NF1, ...SDHA, SDHB, SDHC, SDHD, SDHAF2 and TMEM127 genes. Although genome-wide expression studies have revealed some of the mechanisms likely to be involved in pheochromocytoma/paraganglioma tumorigenesis, the complete molecular distinction of all subtypes of hereditary tumors has not been solved and the genetic events involved in the generation of sporadic tumors are unknown. With these purposes in mind, we investigated 202 pheochromocytomas/paragangliomas, including 75 hereditary tumors, using expression profiling, BAC array comparative genomic hybridization and somatic mutation screening. Gene expression signatures defined the hereditary tumors according to their genotype and notably, led to a complete subseparation between SDHx- and VHL-related tumors. In tumor tissues, the systematic characterization of somatic genetic events associated with germline mutations in tumor suppressor genes revealed loss of heterozygosity (LOH) in a majority of cases, but also detected point mutations and copy-neutral LOH. Finally, guided by transcriptome classifications and LOH profiles, somatic mutations in VHL or RET genes were identified in 14% of sporadic pheochromocytomas/paragangliomas. Overall, we found a germline or somatic genetic alteration in 45.5% (92/202) of the tumors in this large series of pheochromocytomas/paragangliomas. Regarding mutated genes, specific molecular pathways involved in tumorigenesis mechanisms are identified. Altogether, these new findings suggest that somatic mutation analysis is likely to yield important clues for personalizing molecular targeted therapies.
The commonest tumors associated with neurofibromatosis type 1 (NF1) are benign peripheral nerve sheath tumors, called neurofibromas. Malignant transformation of neurofibromas into aggressive MPNSTs ...may occur with a poor patient prognosis. A cooperative role of SUZ12 or EED inactivation, along with NF1, TP53, and CDKN2A loss‐of‐function, has been proposed to drive progression to MPNSTs. An exome sequencing analysis of eight MPNSTs, one plexiform neurofibroma, and seven cutaneous neurofibromas was undertaken. Biallelic inactivation of the NF1 gene was observed in the plexiform neurofibroma and the MPNSTs, underlining that somatic biallelic NF1 inactivation is likely to be the initiating event for plexiform neurofibroma genesis, although it is unlikely to be sufficient for the subsequent MPNST development. The majority (5/8) of MPNSTs in our analyses demonstrated homozygous or heterozygous deletions of CDKN2A, which may represent an early event following NF1 LOH in the malignant transformation of Schwann cells from plexiform neurofibroma to MPNST. Biallelic somatic alterations of SUZ12 was also found in 4/8 MPNSTs. EED biallelic alterations were detected in 2 of the other four MPNSTs, with one tumor having a homozygous EED deletion. A missense mutation in the chromatin regulator KDM2B was also identified in one MPNST. No TP53 point mutations were found in this study, confirming previous data that TP53 mutations may be relatively rare in NF1‐associated MPNSTs. Our study confirms the frequent biallelic inactivation of PRC2 subunits SUZ12 and EED in MPNSTs, and suggests the implication of KDM2B.
Germline mutations in the RET, SDHA, SDHAF2, SDHB, SDHC, SDHD, MAX, TMEM127, NF1 or VHL genes are identified in about 30% of patients with pheochromocytoma or paraganglioma and somatic mutations in ...RET, VHL or MAX genes are reported in 17% of sporadic tumors. In the present study, using mutation screening of the NF1 gene, mapping of chromosome aberrations by single nucleotide polymorphism (SNP) array, microarray-based expression profiling and immunohistochemistry (IHC), we addressed the implication of NF1 somatic alterations in pheochromocytomas and paragangliomas. We studied 53 sporadic tumors, selected because of their classification with RET/NF1/TMEM127-related tumors by genome wide expression studies, as well as a second set of 11 independent tumors selected on their low individual levels of NF1 expression evaluated by microarray. Direct sequencing of the NF1 gene in tumor DNA identified the presence of an inactivating NF1 somatic mutation in 41% (25/61) of analyzed sporadic tumors, associated with loss of the wild-type allele in 84% (21/25) of cases. Gene expression signature of NF1-related tumors highlighted the downregulation of NF1 and the major overexpression of SOX9. Among the second set of 11 tumors, two sporadic tumors carried somatic mutations in NF1 as well as in another susceptibility gene. These new findings suggest that NF1 loss of function is a frequent event in the tumorigenesis of sporadic pheochromocytoma and strengthen the new concept of molecular-based targeted therapy for pheochromocytoma or paraganglioma.
Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor involved in xenobiotic metabolism. Plexiform neurofibromas (PNFs) can transform into malignant peripheral nerve sheath ...tumors (MPNSTs) that are resistant to existing therapies. These tumors are primarily composed of Schwann cells. In addition to neurofibromatosis type 1 (NF1) gene inactivation, further genetic lesions are required for malignant transformation. We have quantified the mRNA expression levels of AHR and its associated genes in 38 human samples. We report that AHR and the biosynthetic enzymes of its endogenous ligand are overexpressed in human biopsies of PNFs and MPNSTs. We also detect a strong nuclear AHR staining in MPNSTs. The inhibition of AHR by siRNA or antagonists, CH-223191 and trimethoxyflavone, induces apoptosis in human MPNST cells. Since AHR dysregulation is observed in these tumors, we investigate AHR involvement in Schwann cell physiology. Hence, we studied the role of AHR in myelin structure and myelin gene regulation in Ahr
−/− mice during myelin development. AHR ablation leads to locomotion defects and provokes thinner myelin sheaths around the axons. We observe a dysregulation of myelin gene expression and myelin developmental markers in Ahr
−/− mice. Interestingly, AHR does not directly bind to myelin gene promoters. The inhibition of AHR in vitro and in vivo increased β-catenin levels and stimulated the binding of β-catenin on myelin gene promoters. Taken together, our findings reveal an endogenous role of AHR in peripheral myelination and in peripheral nerve sheath tumors. Finally, we suggest a potential therapeutic approach by targeting AHR in nerve tumors.
Background
Neurofibromatosis type 1 (NF1) is a tumor predisposition syndrome with a worldwide birth incidence of one in 2500. Genetic factors unrelated to the NF1 locus are thought to influence the ...number of plexiform neurofibromas (PNFs) in patients with NF1, but no factors have been identified to date.
Methods
We used high-resolution array comparative genomic hybridization of tissue from 22 PNFs obtained from 18 NF1 patients to identify modifier genes involved in PNF development. We used a family-based association test for five previously identified cancer-susceptibility tag single-nucleotide polymorphisms (rs1063192, rs2151280, rs2218220, rs10757257, and rs7023329) located in chromosomal region 9p21.3 in 1105 subjects (740 NF1 patients and 365 non-affected relatives) from 306 families. To confirm the functional role of rs2151280, we used real-time quantitative reverse transcription-polymerase chain reaction to analyze the expression of cyclin-dependent kinase inhibitor 2A (CDKN2A), CDKN2B, alternate reading frame (ARF), and antisense noncoding RNA in the INK4 locus (ANRIL) in the peripheral blood of 124 NF1 patients. Relationships between CDKN2A, CDKN2B, ARF, and ANRIL expression and the rs2151280 genotype were tested by the Kruskal-Wallis test. All statistical tests were two-sided.
Results
In NF1-associated PNFs, 9p21.3 deletions (including the CDKN2A/B-ANRIL locus) were found as the only recurrent somatic alterations. Single-nucleotide polymorphism rs2151280 (located in ANRIL) was statistically significantly associated with the number of PNFs (P < .001) in NF1 patients. In addition, allele T of rs2151280 was statistically significantly associated with reduced ANRIL transcript levels (P < .001), suggesting that modulation of ANRIL expression mediates PNF susceptibility.
Conclusion
Identification of ANRIL as a modifier gene in NF1 may offer clues to the molecular pathogenesis of PNFs, particularly neurofibroma formation, and emphasizes the unanticipated role of large noncoding RNA in activation of critical regulators of tumor development.
Churg-Strauss syndrome (CSS) is characterized by systemic vasculitis and blood and tissue eosinophilia. Blood eosinophilia correlates with disease activity, and activated T cells from CSS patients ...are predominantly T helper 2 (Th2). Interleukin (IL)-25 has been shown to link innate and adaptive immunity by enhancing Th2 cytokine production. We sought to determine the involvement of IL-25 and its receptor IL-17RB in the pathogenesis of CSS. We found increased levels of IL-25 in the serum of active CSS patients (952 ± 697 vs 75 ± 49 pg/mL in inactive patients and 47 ± 6 pg/mL in healthy donors). IL-25 was correlated with disease activity and eosinophil level. Eosinophils were the main source of IL-25, whereas activated CD4+ memory T cells were the IL-17RB–expressing cells in CSS. IL-25 enhanced the production of IL-4, IL-5, and IL-13 by activated peripheral blood mononuclear cells. IL-25 and IL-17RB were observed within the vasculitic lesions of patients with CSS, and IL-17RB colocalized with T cells. Increased expression of IL-17RB, tumor necrosis factor receptor–associated factor 6, and JunB in vasculitic lesions of CSS underscored the IL-25–mediated activation, whereas up-regulation of GATA3 and IL-10 supported Th2 differentiation. Our findings suggest that eosinophils, through the production of IL-25, exert a critical role in promoting Th2 responses in target tissues of CSS.
The hallmark of neurofibromatosis type 1 (NF1) is the onset of dermal or plexiform neurofibromas, mainly composed of Schwann cells. Plexiform neurofibromas can transform into malignant peripheral ...nerve sheath tumors (MPNST) that are resistant to therapies.
The aim of this study was to identify an additional pathway in the NF1 tumorigenesis. We focused our work on Wnt signaling that is highly implicated in cancer, mainly in regulating the proliferation of cancer stem cells. We quantified mRNAs of 89 Wnt pathway genes in 57 NF1-associated tumors including dermal and plexiform neurofibromas and MPNSTs. Expression of two major stem cell marker genes and five major epithelial-mesenchymal transition marker genes was also assessed. The expression of significantly deregulated Wnt genes was then studied in normal human Schwann cells, fibroblasts, endothelial cells, and mast cells and in seven MPNST cell lines.
The expression of nine Wnt genes was significantly deregulated in plexiform neurofibromas in comparison with dermal neurofibromas. Twenty Wnt genes showed altered expression in MPNST biopsies and cell lines. Immunohistochemical studies confirmed the Wnt pathway activation in NF1-associated MPNSTs. We then confirmed that the knockdown of NF1 in Schwann cells but not in epithelial cells provoked the activation of Wnt pathway by functional transfection assays. Furthermore, we showed that the protein expression of active β-catenin was increased in NF1-silenced cell lines. Wnt pathway activation was strongly associated to both cancer stem cell reservoir and Schwann-mesenchymal transition.
We highlighted the implication of Wnt pathway in NF1-associated tumorigenesis.
Neurofibromatosis type 1 (NF1) is a common dominant tumor predisposition syndrome affecting 1 in 3,500 individuals. The hallmarks of NF1 are the development of peripheral nerve sheath tumors either ...benign (dermal and plexiform neurofibromas) or malignant (MPNSTs).
To comprehensively characterize the role of microRNAs in NF1 tumorigenesis, we analyzed 377 miRNAs expression in a large panel of dermal and plexiform neurofibromas, and MPNSTs. The most significantly upregulated miRNA in plexiform neurofibromas was miR-486-3p that targets the major tumor suppressor gene, PTEN. We confirmed PTEN downregulation at mRNA level. In plexiform neurofibromas, we also report aberrant expression of four miRNAs involved in the RAS-MAPK pathway (miR-370, miR-143, miR-181a, and miR-145). In MPNSTs, significant deregulated miRNAs were involved in PTEN repression (miR-301a, miR-19a, and miR-106b), RAS-MAPK pathway regulation (Let-7b, miR-195, and miR-10b), mesenchymal transition (miR-200c, let-7b, miR-135a, miR-135b, and miR-9), HOX genes expression (miR-210, miR-196b, miR-10a, miR-10b, and miR-9), and cell cycle progression (miR-195, let-7b, miR-20a, miR-210, miR-129-3p, miR-449a, and miR-106b).
We confirmed the implication of PTEN in genesis of plexiform neurofibromas and MPNSTs in NF1. Markedly deregulated miRNAs might have potential diagnostic or prognostic value and could represent novel strategies for effective pharmacological therapies of NF1 tumors.
The Hedgehog (Hh) signaling pathway has an important role during embryogenesis and in adult life, regulating proliferation, angiogenesis, matrix remodeling and stem-cell renewal. Deregulation of the ...Hh pathway is involved in tumor development, since mutations in several components of this pathway were found in patients with basal cell carcinoma, medulloblastoma and other tumors; however, the role of Hh in meningiomas has not been studied yet. Meningiomas represent 30% of primary cranial tumors, are mostly benign and prevail in the second half of life. Novel therapies for meningiomas such as targeted molecular agents could use Hh pathway components. To provide information concerning molecular alterations, by use of real-time RT-PCR, we studied expression at the mRNA level of 32 Hh pathway and target genes in 36 meningioma specimens of different grades. mRNA levels of 16 genes, involved mainly in Hh pathway activation and cell proliferation, increased in meningiomas in comparison with normal tissue, whereas those of 7 genes, mainly related to Hh pathway repression, decreased. The most significant changes occurred in signal transduction (SMO) and GLI-transcription factor genes, and the target FOXM1 mRNA attained the highest values; their over-expression was found in aggressive and in benign tumors. Some proliferation-related genes (SPP1, IGF2) were overexpressed in higher meningioma grades. A correlation in expression between genes with a similar function was also found. Our results show a marked activation of the Hh pathway in meningiomas, which may be important for their biological and clinical characterization and would be useful for gene therapy.
To determine the role of Wnt antagonist Dickkopf (DKK) 1 in human endothelial colony-forming cells (ECFCs) in view of the emerging importance of Wnt pathways in vascular biology.
Endothelial ...progenitor cells have been proposed to be crucial in tumor neovascularization. Recombinant DKK1 has been tested in ECFC angiogenic properties in vitro. DKK1 enhanced ECFC proliferation and the capacity of ECFCs to form pseudotubes in Matrigel. These effects have been attributed to enhancement of vascular endothelial growth factor receptor 2, SDF-1, and CXCR4. DKK1 gene silencing has been realized on ECFCs and mesenchymal stem cells, and we found that DKK1 silencing in the 2 cell types decreased their angiogenic potential. We then examined the possible role of DKK1 in tumor neovasculogenesis and found that blood vessels of breast cancer tissues expressed DKK1 far more strongly in human breast tumors than in normal breast tissues. By studying 62 human breast tumors, we found a significant positive correlation between DKK1 expression and von Willebrand factor. In vivo, DKK1 strongly enhanced the vascularization of Matrigel plugs and increased tumor size in a xenograft model of human breast carcinoma in nude mice.
DKK1 enhances angiogenic properties of ECFCs in vitro and is required for ECFC and mesenchymal stem cell angiogenic phenotypes in vivo. DKK1 also increases tumoral angiogenesis. Thus, we demonstrated a major role of DKK1 in angiogenic processes.
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