RESUMO
Mutations of the tumor suppressor p53 lead to chemotherapy resistance and a dismal prognosis in chronic lymphocytic leukemia (CLL). Whereas p53 targets are used to identify patient subgroups with impaired p53 function, a comprehensive assessment of non-coding RNA targets of p53 in CLL is missing. We exploited the impaired transcriptional activity of mutant p53 to map out p53 targets in CLL by small RNA sequencing. We describe the landscape of p53-dependent microRNA/non-coding RNA induced in response to DNA damage in CLL. Besides the key p53 target miR-34a, we identify a set of p53-dependent microRNAs (miRNAs; miR-182-5p, miR-7-5p and miR-320c/d). In addition to miRNAs, the long non-coding RNAs (lncRNAs) nuclear enriched abundant transcript 1 (NEAT1) and long intergenic non-coding RNA p21 (lincRNA-p21) are induced in response to DNA damage in the presence of functional p53 but not in CLL with p53 mutation. Induction of NEAT1 and lincRNA-p21 are closely correlated to the induction of cell death after DNA damage. We used isogenic lymphoma cell line models to prove p53 dependence of NEAT1 and lincRNA-p21. The current work describes the p53-dependent miRNome and identifies lncRNAs NEAT1 and lincRNA-p21 as novel elements of the p53-dependent DNA damage response machinery in CLL and lymphoma.
Assuntos
Apoptose , Leucemia Linfocítica Crônica de Células B/genética , MicroRNAs/genética , RNA Longo não Codificante/genética , Proteína Supressora de Tumor p53/genética , Idoso , Idoso de 80 Anos ou mais , Western Blotting , Proliferação de Células , Imunoprecipitação da Cromatina , Dano ao DNA , Feminino , Citometria de Fluxo , Humanos , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Prognóstico , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Células Tumorais Cultivadas , Proteína Supressora de Tumor p53/metabolismoRESUMO
Mutations or deletions in TP53 or ATM are well-known determinants of poor prognosis in chronic lymphocytic leukemia (CLL), but only account for approximately 40% of chemo-resistant patients. Genome-wide sequencing has uncovered novel mutations in the splicing factor sf3b1, that were in part associated with ATM aberrations, suggesting functional synergy. We first performed detailed genetic analyses in a CLL cohort (n=110) containing ATM, SF3B1 and TP53 gene defects. Next, we applied a newly developed multiplex assay for p53/ATM target gene induction and measured apoptotic responses to DNA damage. Interestingly, SF3B1 mutated samples without concurrent ATM and TP53 aberrations (sole SF3B1) displayed partially defective ATM/p53 transcriptional and apoptotic responses to various DNA-damaging regimens. In contrast, NOTCH1 or K/N-RAS mutated CLL displayed normal responses in p53/ATM target gene induction and apoptosis. In sole SF3B1 mutated cases, ATM kinase function remained intact, and γH2AX formation, a marker for DNA damage, was increased at baseline and upon irradiation. Our data demonstrate that single mutations in sf3b1 are associated with increased DNA damage and/or an aberrant response to DNA damage. Together, our observations may offer an explanation for the poor prognosis associated with SF3B1 mutations.
Assuntos
Regulação Leucêmica da Expressão Gênica , Leucemia Linfocítica Crônica de Células B/genética , Mutação , Fosfoproteínas/genética , Ribonucleoproteína Nuclear Pequena U2/genética , Apoptose , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Estudos de Coortes , Dano ao DNA , Análise Mutacional de DNA , Doxorrubicina/farmacologia , Citometria de Fluxo , Deleção de Genes , Genoma Humano , Histonas/metabolismo , Humanos , Imidazóis/farmacologia , Piperazinas/farmacologia , Prognóstico , Fatores de Processamento de RNA , Receptor Notch1/genética , Proteína Supressora de Tumor p53/genética , Vidarabina/análogos & derivados , Vidarabina/farmacologiaRESUMO
The use of hormone replacement therapy (HRT) for cardiovascular risk reduction remains uncertain. Although previous epidemiological surveys have suggested a clear benefit and nearly 50% mortality risk reduction with HRT in postmenopausal women, recent randomised trials have largely failed to support this. The epidemiological surveys may have been biased in a number of ways including the possibility that HRT users in these studies may have been healthier and taken a greater interest in modifying cardiovascular risks. The aim of the present study was to determine to what extent the revelations from all these trials have influenced HRT prescribing in general practice, in relation to cardiovascular disease. We reviewed 140 women on HRT and 140 age-matched controls from one city centre general practice in the west of Birmingham who were randomly selected by computer. The main indication for HRT use was presence of symptoms associated with oestrogen deficiency. The prevention of osteoporosis accounted for 7.1% of HRT indications, while the primary prevention of CHD was not an issue discussed by either the patient or the GP. Among non-users, 86.4% did not have a known contraindication and many did not have serum lipid measurements or estimations of cardiovascular risk. There was no difference between HRT users and non-users for smoking habits and presence of cardiovascular risk factors including diabetes, hypertension and coronary heart disease. HRT users were also less likely to undergo investigations, such as cervical smear tests and mammograms. In conclusion, this survey reflects the current uncertainty surrounding the use of HRT for cardiovascular risk prevention. Importantly, women on HRT may not be any healthier than non-users, nor do they seek more preventive care than non-users. This is contrary to previous presumptions that selection and prevention bias were the explanation for the apparent cardioprotective effects of HRT.
