RESUMO
BACKGROUND: Paragangliomas are benign, slow-growing tumours of the head and neck region. The candidate gene for familial and some sporadic paragangliomas, SDHD (succinate dehydrogenase, subunit D), has been mapped to the PGL1 locus in 11q23.3. MATERIALS AND METHODS: Normal and tumour DNA of 17 patients with sporadic paragangliomas were analysed by sequencing (SDHD, SDHB and SDHC genes), fluorescence in situ hybridisation (FISH). In addition, loss of heterozygosity (LOH) and succinate dehydrogenase (SDH) enzyme activity assays were performed. RESULTS AND CONCLUSION: Only two patients from our collective showed SDH gene mutations, one in SDHD and one in SDHB, respectively. Moreover, SDH activity detected in 5/8 patients confirmed the fact that SDH inactivation is not a major event in sporadic paragangliomas. LOH and FISH analysis demonstrated a frequent loss of regions within chromosome 11, indicating that additional genes in 11q may play a role in tumour genesis of sporadic paragangliomas.
Assuntos
Proteínas de Membrana/genética , Paraganglioma Extrassuprarrenal/enzimologia , Paraganglioma Extrassuprarrenal/genética , Succinato Desidrogenase/genética , Tumor do Corpo Carotídeo/enzimologia , Tumor do Corpo Carotídeo/genética , Cromossomos Humanos Par 11/genética , Tumor do Glomo Jugular/enzimologia , Tumor do Glomo Jugular/genética , Tumor de Glomo Timpânico/enzimologia , Tumor de Glomo Timpânico/genética , Humanos , Hibridização in Situ Fluorescente , Perda de Heterozigosidade , Proteínas de Membrana/metabolismo , Mutação , Inclusão em Parafina , Succinato Desidrogenase/metabolismoRESUMO
Lack of regular cell-cell interaction is one major cause for neoplastic growth and metastasis. In head and neck squamous cell carcinomas a 10-fold down-regulation of connexin31.1 (GJB5) as well as mutations in the TGF-beta-receptor-II were reported. We performed mutation screenings in GJB5 and the TGF-beta-receptor-II poly(10)adenine hot spot employing larynx cancer samples of 10 patients. Variable length of the TGF-beta-receptor-II adenine homopolymer in controls and tumours indicate a high slippage error rate of the DNA polymerases rendering mutational analyses inconsistent. Lack of GJB5 mutations in the entire tumour collection suggests that this gene is not primarily involved in laryngeal tumorigenesis.
Assuntos
Carcinoma de Células Escamosas/genética , Conexinas/biossíntese , Neoplasias Laríngeas/genética , Receptores de Fatores de Crescimento Transformadores beta/genética , Adulto , Idoso , Carcinoma de Células Escamosas/patologia , Estudos de Casos e Controles , Comunicação Celular , Análise Mutacional de DNA , DNA Polimerase Dirigida por DNA/farmacologia , Regulação para Baixo , Feminino , Humanos , Neoplasias Laríngeas/patologia , Perda de Heterozigosidade , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase , Proteínas Serina-Treonina Quinases , Receptor do Fator de Crescimento Transformador beta Tipo IIRESUMO
BACKGROUND: Alpha-tectorin is a noncollagenous component of the tectorial membrane which plays an essential role in auditory transduction. In several DFNA12 families mutations in TECTA, the gene encoding alpha-tectorin, were shown to cause hearing impairment (HI) with different phenotypes depending on the location of the mutation. METHODS/RESULTS: Here we report a Turkish family displaying autosomal dominant inherited HI. Linkage analysis revealed significant cosegregation (LOD score: 4.6) of the disease to markers on chromosome 11q23.3- q24. This region contains the TECTA gene which was subsequently sequenced. A nucleotide change in exon 13, 4526T>G, was detected leading to a substitution from cysteine to glycine at codon 1509 of the TECTA protein. This cysteine is located in vWFD4 domain, a protein domain which is supposed to be involved in disulfide bonds and protein-protein interactions. CONCLUSIONS: It is conspicuous that the phenotype in this family correlates with other families, also displaying mutations involving conserved cysteines. In all three families these mutations result in progressive HI involving high frequencies. In contrast, mutations which are not affecting the vWFD domains seem to provoke mid-frequency sensorineural HI. Furthermore, evaluation of clinical data in our family revealed a gender effect for the severity of hearing impairment. Males were significantly more affected than females. The identification of the third family displaying a missense mutation in the vWFD domain of alpha-tectorin underlines the phenotype-genotype correlation based on different mutations in TECTA.
Assuntos
Proteínas da Matriz Extracelular/genética , Perda Auditiva Neurossensorial/genética , Glicoproteínas de Membrana/genética , Mutação de Sentido Incorreto/genética , Fatores Sexuais , Fatores Etários , Sequência de Aminoácidos , Substituição de Aminoácidos/genética , Animais , Cromossomos Humanos Par 11/genética , Cisteína/genética , Éxons/genética , Feminino , Proteínas Ligadas por GPI , Genótipo , Perda Auditiva Neurossensorial/diagnóstico , Perda Auditiva Neurossensorial/etiologia , Humanos , Masculino , Repetições de Microssatélites/genética , Dados de Sequência Molecular , Fenótipo , Estrutura Terciária de Proteína/genéticaRESUMO
It has been advanced that the trefoil factor (TFF) 1 gene is a candidate tumor-suppressor gene and may be involved in the development and/or progression of human gastric cancer. We aimed to clarify the putative role of TFF1 in gastric carcinogenesis. Ninety gastric carcinomas and eight gastric carcinoma-derived cell lines were screened for TFF1 mutations; subsets of the primary tumors and of the cell lines were subjected to loss of heterozygosity (LOH), immunohistochemistry, and promoter methylation analyses. TFF1 mutations were not detected in any of 90 gastric carcinomas. Eight (28%) of 28 informative cases displayed LOH at the TFF1 locus and absence of TFF1 staining by immunohistochemistry. These results indicate a frequent loss of TFF1 expression in gastric carcinomas through a mutation-independent mechanism. Extensive TFF1 promoter methylation was observed in nonexpressing gastric carcinoma-derived cell lines and tissues. Expressing cell lines, as well as normal gastric mucosa, presented little or no methylation of the promoter. Gastric carcinoma DNA presented de novo methylation of the promoter. These results point to the involvement of promoter methylation in the shutting down of TFF1. We conclude that TFF1 point mutations seem to be a rare event in gastric carcinogenesis. The loss of expression of TFF1 in a proportion of gastric carcinomas may be explained by LOH and methylation of the TFF1 promoter region. Our results further support the role of TFF1 inactivation in gastric carcinogenesis, in agreement with the results obtained in the Tff1-knockout mice model.
