RESUMO
Copy number alterations are frequently found in colorectal cancer (CRC), and recurrent gains or losses are likely to correspond to regions harbouring genes that promote or impede carcinogenesis respectively. Gain of chromosome 13q is common in CRC but, because the region of gain is frequently large, identification of the driver gene(s) has hitherto proved difficult. We used array comparative genomic hybridization to analyse 124 primary CRCs, demonstrating that 13q34 is a region of gain in 35% of CRCs, with focal gains in 4% and amplification in a further 1.6% of cases. To reduce the number of potential driver genes to consider, it was necessary to refine the boundaries of the narrowest copy number changes seen in this series and hence define the minimal copy region (MCR). This was performed using molecular copy-number counting, identifying IRS2 as the only complete gene, and therefore the likely driver oncogene, within the refined MCR. Analysis of available colorectal neoplasia data sets confirmed IRS2 gene gain as a common event. Furthermore, IRS2 protein and mRNA expression in colorectal neoplasia was assessed and was positively correlated with progression from normal through adenoma to carcinoma. In functional in vitro experiments, we demonstrate that deregulated expression of IRS2 activates the oncogenic PI3 kinase pathway and increases cell adhesion, both characteristics of invasive CRC cells. Together, these data identify IRS2 as a likely driver oncogene in the prevalent 13q34 region of gain/amplification and suggest that IRS2 over-expression may provide an additional mechanism of PI3 kinase pathway activation in CRC.
Assuntos
Adenocarcinoma/genética , Cromossomos Humanos Par 13 , Neoplasias Colorretais/genética , Dosagem de Genes/genética , Proteínas Substratos do Receptor de Insulina/genética , Adenocarcinoma/metabolismo , Adenocarcinoma/secundário , Pólipos do Colo/genética , Pólipos do Colo/metabolismo , Pólipos do Colo/patologia , Neoplasias Colorretais/metabolismo , Neoplasias Colorretais/patologia , Bases de Dados Genéticas , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica/genética , Instabilidade Genômica/genética , Humanos , Proteínas Substratos do Receptor de Insulina/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , RNA Mensageiro/genética , Transdução de Sinais/genética , Células Tumorais CultivadasRESUMO
We have previously identified a region containing 16 CpGs within the MGMT CpG islands which is critical for the transcriptional control of MGMT (Malley, Acta Neuropathol 2011). To investigate the patterns and incidence of MGMT methylation in astrocytic and oligodendroglial tumors, we quantitatively assessed methylation at these 16 CpGs using bisulfite modification followed by pyrosequencing of 362 gliomas not treated with temozolomide, and correlated the findings with previously identified patterns of genetic abnormalities, patients' age and survival. The MGMT gene was considered to be methylated when the mean methylation of the 16 CpGs was 10% or higher. This cut-off value distinguished diffuse astrocytomas with high and low MGMT expression. Within each tumor type, the patterns of methylation were highly variable and also highly heterogeneous across the 16 CpGs. A high incidence of MGMT methylation was observed in all subtypes of gliomas included in this study. Among a subset of 97 tumors where conventional methylation-specific PCR (MSP) was also applied, methylation was detected by both methods in 54 tumors, while the pyrosequencing results identified a further 17 tumors. No additional cases were found using MSP alone, indicating that pyrosequencing is a robust method for methylation analysis. All tumors with IDH1/IDH2 mutations except two had MGMT methylation, while there were many tumors with MGMT methylation, particularly primary glioblastomas, which had no mutations of IDH1/2. We suggest that MGMT methylation may be one of the earliest events in the development of astrocytic and oligodendroglial tumors.
Assuntos
Astrocitoma/genética , Ilhas de CpG/genética , Metilação de DNA , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Isocitrato Desidrogenase/genética , Mutação/genética , Oligodendroglioma/genética , Proteínas Supressoras de Tumor/genética , Adolescente , Adulto , Astrocitoma/mortalidade , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/mortalidade , Criança , DNA de Neoplasias/genética , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Oligodendroglioma/mortalidade , Prognóstico , Regiões Promotoras Genéticas/genética , Reação em Cadeia da Polimerase em Tempo Real , Taxa de Sobrevida , Adulto JovemRESUMO
Diffuse astrocytomas (WHO grade II) typically present as slow-growing tumours showing significant cellular differentiation, but possessing a tendency towards malignant progression. They account for ~10% of all astrocytic tumours, with a peak incidence between 30 and 40 years of age. Median survival is reported as around 6-8 years. Mutations of TP53 and IDH1 have been described as genetic hallmarks, while copy number alterations are also relatively common. However, there is some evidence to suggest that these characteristics may vary with age. Here, we present an integrated clinicopathologic, genomic and transcriptomic analysis suggesting that paediatric and adult tumours are associated with distinct genetic signatures. For example, no childhood tumour showed mutation of IDH1/2 or TP53, virtually no copy number changes were seen, and MGMT methylation was absent. In contrast, adult tumours showed IDH1/2 mutation in 94% and TP53 mutation in 69% of cases, with multiple copy number alterations per case and hypermethylation of MGMT in the majority of tumours. These differences were associated with a worse prognosis in the adult patients. The expression array data also revealed a significant difference in the expression of a number of genes putatively involved in neural stem cell maintenance and CNS development, including DLL3, HES5, BMP2, TIMP1 and BAMBI. Genes involved in DNA replication and the cell cycle were also enriched in the adult tumours, suggesting that their more aggressive behaviour may be due to derivation from a more rapidly dividing, less differentiated cell type.
Assuntos
Astrocitoma/genética , Neoplasias Encefálicas/genética , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Regulação Neoplásica da Expressão Gênica/genética , Isocitrato Desidrogenase/genética , Proteína Supressora de Tumor p53/genética , Proteínas Supressoras de Tumor/genética , Adolescente , Adulto , Fatores Etários , Astrocitoma/patologia , Astrocitoma/fisiopatologia , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/fisiopatologia , Criança , Variações do Número de Cópias de DNA , Metilação de DNA , Análise Mutacional de DNA/métodos , Feminino , Perfilação da Expressão Gênica/métodos , Humanos , Masculino , Pessoa de Meia-Idade , Mutação/genética , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Análise de Componente Principal , Análise de Sobrevida , Adulto JovemRESUMO
There is evidence that a substantial part of genetic predisposition to prostate cancer (PCa) may be due to lower penetrance genes which are found by genome-wide association studies. We have recently conducted such a study and seven new regions of the genome linked to PCa risk have been identified. Three of these loci contain candidate susceptibility genes: MSMB, LMTK2 and KLK2/3. The MSMB and KLK2/3 genes may be useful for PCa screening, and the LMTK2 gene might provide a potential therapeutic target. Together with results from other groups, there are now 23 germline genetic variants which have been reported. These results have the potential to be developed into a genetic test. However, we consider that marketing of tests to the public is premature, as PCa risk can not be evaluated fully at this stage and the appropriate screening protocols need to be developed. Follow-up validation studies, as well as studies to explore the psychological implications of genetic profile testing, will be vital prior to roll out into healthcare.
Assuntos
Predisposição Genética para Doença/genética , Neoplasias da Próstata/diagnóstico , Neoplasias da Próstata/genética , Testes Genéticos , Humanos , Calicreínas/genética , Masculino , Proteínas de Membrana/genética , Proteínas Secretadas pela Próstata/genética , Proteínas Serina-Treonina Quinases/genética , Fatores de RiscoRESUMO
Prostate cancer is the most common cancer affecting males in developed countries. It shows consistent evidence of familial aggregation, but the causes of this aggregation are mostly unknown. To identify common alleles associated with prostate cancer risk, we conducted a genome-wide association study (GWAS) using blood DNA samples from 1,854 individuals with clinically detected prostate cancer diagnosed at