Identificação de genes de fusão no cisto ósseo aneurismático

• Ano de defesa: 2010
• Autor(a) principal: Oliveira, Andre Machado Mascarenhas de [UNIFESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo (UNIFESP)
• Palavras-chave em Português: Citogenética; Genes de fusão; Oncogene; USP6; Cistos ósseo aneurismático; Cistos ósseos
• Link de acesso: http://repositorio.unifesp.br/handle/11600/9698

Aneurysmal bone cyst is a bone lesion of unknown pathogenesis. However, recent cytogenetic findings suggest a possible clonal neoplastic nature for this lesion with a few examples showing the chromosomal translocation t(16;17)(q22;p13). Objectives: (1) map at the genomic level this translocation and characterize the genes involved, (2) verify the sensitivity and specificity of this genetic anomaly, (3) identify the aneurysmal bone cyst neoplastic cell, (4) correlate the molecular findings with clinico-pathologic features, and (5) characterize alternative oncogenic mechanisms. Methods: Fresh, frozen and paraffin-embedded tissues were used in these studies. Initially eight cases of aneurysmal bone cyst were investigated at the cytogenetics and molecular genetic levels using fluorescence in situ hybridization (FISH) and reverse transcriptase polymerase chain reaction (RT-PCR). The findings were confirmed in 52 primary and 17 secondary aneurysmal bone cysts. Clinico-pathologic data were also obtained. Results: The chromosomal translocation t(16;17)(q22;p13) leads to the creation of a fusion gene in which the promoter region of the osteoblastic cadherin CDH11 is fused to the entire coding sequence of the ubiquitin specific protease USP6. CDH11-USP6 mRNA was demonstrated only in aneurysmal bone cysts with the translocation t(16;17). Thirty-six (of 52; 69%) primary aneurysmal bone cysts demonstrated rearrangements of CDH11, USP6 or both: 10 (28%) contained the fusion gene CDH11-USP6, 23 (64%) demonstrated rearrangements of the USP6 locus without CDH11 involvement, and three (8%) demonstrated CDH11 rearrangement without USP6 involvement. The molecular alterations were observed only in the spindle cell component of the tumor and not in other cell types. No correlation between the molecular findings and clinico-pathologic features of the lesion was observed. None of the 17 secondary aneurysmal bone cysts demonstrated alterations of the CDH11 and USP6 loci. The alternate chromosomal translocations led to the formation of the ffusion genes TRAP150-USP6, ZNF9-USP6, OMD(osteomodulin)-USP6 e COL1A1-USP6. The oncogenic mechanism of these novel fusion genes is akin to that of CDH11-USP6. High levels of USP6 mRNA were observed in the aneurysmal bone cyst, and in a few examples of Ewing sarcoma and osteoblastoma, but not in the other tumors evaluated. Conclusions: Aneurysmal bone cyst is a clonal neoplastic disorder whose pathogenesis is related to an increased USP6 mRNA transcription through its fusion with highly active ectopic promoters.