RESUMO
PURPOSE: Conjunctival melanoma is a rare but potentially deadly tumor of the eye. Despite effective local therapies, recurrence and metastasis remain frequent. Once the tumor has metastasized, treatment options are limited and the prognosis is poor. To date, little is known of the genetic alterations in conjunctival melanomas. EXPERIMENTAL DESIGN: We conducted genetic analysis of 78 conjunctival melanomas, to our knowledge the largest cohort reported to date. An oncogene hotspot array was run on 38 samples, screening for a panel of known cancer-relevant mutations. Thirty tumors were analyzed for genome-wide copy number alterations (CNA) using array-based comparative genomic hybridization. Sanger sequencing of selected target mutations was conducted in all samples. RESULTS: BRAF mutations were identified in 23 of 78 (29%) tumors. NRAS mutations, previously not recognized as relevant in conjunctival melanoma, were detected in 14 of 78 (18%) tumors. We found CNAs affecting various chromosomes distributed across the genome in a pattern reminiscent of cutaneous and mucosal melanoma but differing markedly from uveal melanoma. CONCLUSIONS: The presence of NRAS or BRAF mutations in a mutually exclusive pattern in roughly half (47%) of conjunctival melanomas and the pattern of CNAs argue for conjunctival melanoma being closely related to cutaneous and mucosal melanoma but entirely distinct from uveal melanoma. Patients with metastatic conjunctival melanoma should be considered for therapeutic modalities available for metastatic cutaneous and mucosal melanoma including clinical trials of novel agents.
Assuntos
Neoplasias da Túnica Conjuntiva/genética , Variações do Número de Cópias de DNA/genética , GTP Fosfo-Hidrolases/genética , Melanoma/genética , Proteínas de Membrana/genética , Proteínas Proto-Oncogênicas B-raf/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Hibridização Genômica Comparativa , Neoplasias da Túnica Conjuntiva/patologia , Feminino , Humanos , Masculino , Melanoma/patologia , Pessoa de Meia-Idade , Mucosa/patologia , Mutação , Análise de Sequência de DNA , Pele/patologiaRESUMO
The tumour suppressor p53 activates Puma-dependent apoptosis and p21-dependent cell-cycle arrest in response to DNA damage. Deletion of p21 improved stem-cell function and organ maintenance in progeroid mice with dysfunctional telomeres, but the function of Puma has not been investigated in this context. Here we show that deletion of Puma improves stem- and progenitor-cell function, organ maintenance and lifespan of telomere-dysfunctional mice. Puma deletion impairs the clearance of stem and progenitor cells that have accumulated DNA damage as a consequence of critically short telomeres. However, further accumulation of DNA damage in these rescued progenitor cells leads to increasing activation of p21. RNA interference experiments show that upregulation of p21 limits proliferation and evolution of chromosomal imbalances of Puma-deficient stem and progenitor cells with dysfunctional telomeres. These results provide experimental evidence that p53-dependent apoptosis and cell-cycle arrest act in cooperating checkpoints limiting tissue maintenance and evolution of chromosomal instability at stem- and progenitor-cell levels in response to telomere dysfunction. Selective inhibition of Puma-dependent apoptosis can result in temporary improvements in maintenance of telomere-dysfunctional organs.
Assuntos
Proteínas Reguladoras de Apoptose/genética , Pontos de Checagem do Ciclo Celular/genética , Instabilidade Cromossômica , Inibidor de Quinase Dependente de Ciclina p21/genética , Células-Tronco/fisiologia , Telômero/genética , Proteínas Supressoras de Tumor/genética , Animais , Apoptose/genética , Proteínas Reguladoras de Apoptose/metabolismo , Processos de Crescimento Celular/genética , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Dano ao DNA , Camundongos , Camundongos Endogâmicos C57BL , Células NIH 3T3 , Células-Tronco/metabolismo , Telômero/metabolismo , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Regulação para CimaRESUMO
The DFNA25 locus for autosomal dominant nonsyndromic hereditary hearing loss has been mapped to 12q21-q24 by linkage analysis. A de novo deletion in a six-year-old boy with congenital hearing loss as well as mental and motor retardation now provides independent confirmation of this genetic localization and narrows the critical interval to 13 cM in the 12q22-q24.1 region. Mapping of the deletion was performed using fluorescence in situ hybridization (FISH) analysis with region-specific yeast artificial chromosome (YAC) clones. Ten YACs 929_e_4, 959_c_3, 746_h_7, 817_h_10, 886_a_6, 916_h_9, 969_c_12, 747_e_2, 812_h_12, and 959_f_8 were absent from one chromosome 12 from the patient. Molecular analyses of eight polymorphic markers helped to narrow down the breakpoints and demonstrated that the derivative chromosome 12 is of paternal origin. Several known genes including ATP2A2, UBE3B, and VR-OAC that map in the 12q22-q24.1 region are included in the deletion. These results provide evidence that haploinsufficiency for a gene or genes in 12q22-q24.1 is associated with autosomal dominant deafness.