RESUMO
Helicase-like transcription factor is a SWI/SNF chromatin remodeling factor involved in various biological processes. However, little is known about its role in hematopoiesis. In this study, we measured helicase-like transcription factor mRNA expression in the bone marrow of 204 adult patients with de novo acute myeloid leukemia. Patients were dichotomized into low and high expression groups at the median level for clinicopathological correlations. Helicase-like transcription factor levels were dramatically reduced in the low expression patient group compared to those in the normal controls (n=40) (P<0.0001). Low helicase-like transcription factor expression correlated positively with French-American-British M4/M5 subtypes (P<0.0001) and complex cytogenetic abnormalities (P=0.02 for ≥3 abnormalities;P=0.004 for ≥5 abnormalities) but negatively with CEBPA double mutations (P=0.012). Also, low expression correlated with poorer overall (P=0.005) and event-free (P=0.006) survival in the intermediate-risk cytogenetic subgroup. Consistent with the more aggressive disease associated with low expression, helicase-like transcription factor knockdown in leukemic cells promoted proliferation and chromosomal instability that was accompanied by downregulation of mitotic regulators and impaired DNA damage response. The significance of helicase-like transcription factor in genome maintenance was further indicated by its markedly elevated expression in normal human CD34(+)hematopoietic stem cells. We further demonstrated that helicase-like transcription factor was a RUNX1 target and transcriptionally repressed by RUNX1-ETO and site-specific DNA methylation through a duplicated RUNX1 binding site in its promoter. Taken together, our findings provide new mechanistic insights on genomic instability linked to helicase-like transcription factor deregulation, and strongly suggest a tumor suppressor function of the SWI/SNF protein in acute myeloid leukemia.
Assuntos
Células da Medula Óssea/metabolismo , Subunidade alfa 2 de Fator de Ligação ao Core/genética , Proteínas de Ligação a DNA/genética , Regulação Leucêmica da Expressão Gênica , Leucemia Mieloide Aguda/genética , RNA Mensageiro/genética , Fatores de Transcrição/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Antígenos CD34/genética , Antígenos CD34/metabolismo , Sítios de Ligação , Células da Medula Óssea/patologia , Proteínas Estimuladoras de Ligação a CCAAT/genética , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Proliferação de Células , Aberrações Cromossômicas , Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Metilação de DNA , Proteínas de Ligação a DNA/antagonistas & inibidores , Proteínas de Ligação a DNA/metabolismo , Feminino , Instabilidade Genômica , Hematopoese/genética , Humanos , Cariótipo , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/mortalidade , Leucemia Mieloide Aguda/patologia , Masculino , Pessoa de Meia-Idade , Mutação , Regiões Promotoras Genéticas , Ligação Proteica , RNA Mensageiro/antagonistas & inibidores , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Transdução de Sinais , Análise de Sobrevida , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/metabolismoRESUMO
BACKGROUND: Previous studies in Western countries demonstrated BRAF V600E mutation only in a small subset of multiple myeloma (MM) patients. However, the prevalence and clinicopathologic significances of this mutation remain unclear in Chinese MM patients. PATIENTS AND METHODS: We studied diagnostic bone marrow samples from 205 Chinese MM patients by allele-specific PCR to detect BRAF V600E mutation and by high-resolution melting assay to detect KRAS and NRAS mutations. The mutations were confirmed by independent assays. RESULTS: BRAF V600E mutation was found in 9.3% of the cases, the highest prevalence hitherto reported. In addition, the mutation was significantly associated with hypercalcemia and a male predominance but not with aggressive extramedullary diseases or a high serum creatinine level as reported in Western studies. Importantly, BRAF V600E mutation was an adverse prognostic factor for overall survival in younger MM patients by subgroup analysis. Concurrent analysis of RAS mutations highlighted differential alteration spectrum of RAS signaling between Chinese and Western MM, which may suggest a unique myeloma-related genetic profile in Chinese patients. CONCLUSION: Our study revealed a higher prevalence of BRAF V600E mutation in Chinese MM patients. The associated prognostic impacts on younger patients could be beneficial to risk stratification and potential application of BRAF-targeted therapies in Chinese MM management. This is the first large-scale study revealing the prevalence and clinicopathologic significances of BRAF V600E mutation in Chinese myeloma.