DNA甲基转移酶基因在MDS患者中的表达及其临床意义

研究DNA甲基转移酶（DNA methyltransferase,DNMT）基因在骨髓增生异常综合征（MDS）患者中的表达及其与抑癌基因p15INK4B甲基化状态的相关性,并进一步探讨其与临床预后的关系。方法:采用SYBR Green I实时定量逆转录聚合酶链反应（Real-time RT-PCR）方法对48例初治MDS患者和20例正常人骨髓进行DNMT1、DNMT3A、DNMT3B mRNA水平检测;采用甲基化特异性PCR（MSP-PCR）方法检测48例初治MDS患者和20例正常人p15INK4B基因的甲基化状态。结果:低危组MDS患者3种DNMTs mRNA与正常对照组相比,表达水平差异均无统计学意义（P>0.05）;高危组MDS患者3种DNMTs mRNA表达显著高于低危组和正常对照组（P均<0.01）;MDS患者DNMTs mRNA表达水平与p15INK4B基因甲基化程度呈正相关。12例高危MDS患者接受了地西他滨治疗,另外15例高危MDS患者接受了IA/DA联合化疗,地西他滨组疗效与联合化疗组比较差异无统计学意义（P>0.05）。结论:DNMTs基因的异常高表达,导致细胞周期调控相关的p15INK4B等抑癌基因启动子CpG岛过甲基化失活,在MDS患者由低危向高危转变乃至进展为急性髓系白血病（AML）过程中,起着至关重要的作用,DNMTs mRNA表达水平可以作为一种判断MDS预后的指标。      

骨髓增生异常综合征患者p15INK4B基因甲基化与疾病进展的Meta分析

目的 分析骨髓增生异常综合征(MDS)患者p15INK4B基因甲基化与疾病进展的关系.方法 搜索Cochrane Library、Medline、PubMed、Embase、OVID、Springlink、CBMdisc、VIP、万方和CNKI数据库(1979 to 2012),查找报道MDS患者及sAML(MDS转化的白血病)患者p15INK4B基因甲基化发生率的文献,使用RevMan 5.0对数据进行统计分析.结果 共有20篇文献检测了MDS患者p15INK4B基因甲基化状态,并报道了患者骨髓原始细胞数;其中9篇文献包括sAML患者(共690名患者).p15INK4B基因甲基化状态在骨髓原始细胞5％～19％组中高于原始细胞＜5％组(RR=0.41,95％CI:0.33～0.50),sAML组高于MDS原始细胞5％～19％组(RR=0.51,95％CI:0.41～0.64).4篇文献报道了MDS患者疾病的进展(包括179名患者).p15INK4B基因甲基化阳性组疾病进展率高于甲基化阴性组(RR=3.09,95％CI:2.04～4.68).结论 p15INK4B基因甲基化与MDS患者疾病进展及白血病转化密切相关.     

地西他滨对套细胞淋巴瘤Mino细胞系的作用及其机制

 【摘要】 目的 探讨套细胞淋巴瘤细胞系Mino细胞中p15INK4B和p27kip1基因甲基化状态,以及地西他滨对Mino细胞p15INK4B和p27kip1基因去甲基化及诱导细胞凋亡的作用及机制。方法 用不同浓度地西他滨处理套细胞淋巴瘤细胞系Mino细胞,用锥虫蓝拒染法研究药物作用后细胞生长情况,绘制生长曲线,采用流式细胞术分析细胞凋亡和细胞周期的变化,采用RT-PCR和Western blot检测p15INK4B、p27kip1及bcl-2基因mRNA和蛋白的表达水平,用甲基化特异PCR方法检测p15INK4B及p27kip1基因的甲基化程度。结果　地西他滨对套细胞淋巴瘤细胞系Mino细胞有生长抑制作用,作用后细胞凋亡增加,细胞周期阻滞在G1期,p15INK4B和p27kip1基因mRNA表达增加,而抗凋亡基因bcl-2 mRNA的表达下降。经6.4、3.2、1.6 mmol／L地西他滨作用72 h后,Mino细胞P15INK4B基因启动子甲基化率分别下降至25.21 %、48.2 %和65 %,P27kip1基因启动子甲基化率分别下降至20.21 %、50.2 %和70 %。结论　在套细胞淋巴瘤细胞系Mino细胞中存在p15INK4B及p27kip1基因启动子高度甲基化,并且p15INK4B及p27kip1基因mRNA表达水平下降。地西他滨诱导Mino细胞凋亡,可能是通过对pP15INK4B及p27kip1基因去甲基化作用及对bcl-2基因表达的调控所致。     

慢性乙型肝炎病毒感染与p16INK4A基因启动子甲基化关系的研究

目的探讨慢性乙型肝炎病毒(HBV)感染对p16INK4A基因启动子甲基化的影响及其在HBV相关肝细胞癌(HCC)形成中的作用。方法选取23例HBV相关HCC癌及癌旁组织、25例慢性乙型肝炎肝穿刺组织,采用甲基化特异性PCR(MSP)检测p16INK4A基因启动子的甲基化状态;免疫组化EnVision二步法测定肝组织内HBsAg、HBcAg、HBeAg和HBx蛋白的表达;荧光实时定量PCR检测肝组织HBV DNA含量;PCR扩增和直接测序检测HBV x基因变异。结果癌组织p16INK4A基因启动子甲基化阳性率(47.83%)明显高于癌旁组织(17.39%),慢性乙型肝炎患者p16INK4A基因启动子甲基化阳性率(36.00%)与癌组织、癌旁组织差异无统计学意义。在癌旁组织和慢性乙型肝炎, p16INK4A基因启动子甲基化者HBx蛋白表达中位数分别为3.000和0.250,明显高于非甲基化者(0.500和0.000),但在癌组织中,HBx蛋白的表达与p16INK4A基因启动子甲基化状态无关。HBsAg、HBcAg、组织HBV DNA含量和x基因突变均与p16INK4A基因启动子甲基化状态无关。结论在癌前病变中,p16INK4A基因启动子甲基化与HBx蛋白高表达有关,HBx蛋白可能通过诱导p16INK4A基因启动子甲基化而使该抑癌基因失活,在HBV相关HCC形成中起重要作用。     

丙戊酸钠诱导急性淋巴细胞白血病原代细胞凋亡机制的研究

目的 探讨丙戊酸钠（VPA）对急性淋巴细胞白血病（ALL）原代细胞凋亡现象与去甲基化机制之间的联系.方法 选取10例AIL患者原代细胞,MTT法检测VPA对ALL原代细胞增殖抑制作用,DNA ladder试验观察细胞凋亡,Annexin-V-FITC/PI检测细胞早期凋亡,半巢式甲基化特异PCR检测p15INK4B基因甲基化,反转录PCR方法检测p15基因表达水平.实验数据采用SPSS 16.0统计软件处理.结果 VPA可明显抑制细胞增殖,对原代细胞IC50为1.898 mmol/L;DNA ladder试验显示VPA对原代ALL细胞的凋亡作用明显.Annexin-V-FITC/PI检测1.0、2.0、4.0 mmol/LVPA组的凋亡率分别是（5.80±0.65）％、（48.46±2.49）％、（76.45±2.98）％,与未用药组的（0.44±0.04）％比较差异有统计学意义（P＜0.05）.原代ALL细胞经VPA作用后,p15INK4B甲基化水平明显下降,2.0、4.0 mmol/LVPA组与未用药组相比,p15 mRNA表达水平增强,差异有统计学意义（P＜0.05）.结论 VPA通过使p15INK4B基因去甲基化,促进p15基因表达上调,从而促进原代ALL细胞凋亡.     

INK4系列抑癌基因纯合子缺失、甲基化与白血病预后的实验研究

 目的　研究INK4系列抑癌基因纯合子缺失、甲基化与白血病预后的关系。方法　采用聚合酶链反应（PCR）研究p16基因家族在白血病中纯合子缺失,应用甲基化敏感限制内切酶HpaⅡ结合PCR技术研究白血病患者p16、p15、p18、p19 基因甲基化状况,用单因素、多因素Logistic回归分析其基因失活与急性白血病（AL）预后的关系。结果　基因表达组治疗有效27例（84.38 %）,基因失活组治疗有效11例（28.95 %）,基因表达组治疗有效率明显高于基因失活组（P＜0.001）。单因素、多因素Logistic回归分析结果显示p16、p15 基因失活化疗有效率明显低于基因表达组。结论　p16、p15基因失活可作为AL病程进展、复发、预后的指标之一。     

非小细胞肺癌INK4a和ARF基因甲基化与其蛋白共表达关系的探讨

目的:分析INK4a和ARF基因启动子甲基化与其蛋白共表达之间的关系.方法:选择前期实验中p14ARF和p16INK4a蛋白共表达阴性的非小细胞肺癌(NSCLC)患者35例,共表达阳性的NSCLC患者20例作为研究对象,分别称为(p14 p16)阴性组和(p14 p16)阳性组.运用甲基化特异性PCR(MSP)方法对两组患者癌组织INK4a和ARF基因启动子的甲基化状态进行检测.结果:(p14 p16)阴性组有18例发生INK4a基因甲基化,(p14 p16)阳性组有2例发生INK4a基因甲基化,两组差异有显著意义(P＜0.01).(p14 p16)阴性组有8例发生ARF基因启动子甲基化,(p14 p16)阳性组有2例发生ARF基因启动子甲基化,两组差异无显著意义(P＞0.05).INK4a和ARF基因异常申基化相互之间无显著相关性(P＞0.05).结论:NSCLC患者肺癌组织INK4a基因甲基化是导致p16INK4a蛋白表达阴性的重要机制;INK4a和ARF基因甲基化可能是相对独立的事件.     

食管鳞癌中hMLH1、E-cadherin、p16^INK4a基因启动子甲基化及其意义

背景与目的:目前认为抑癌基因启动子甲基化导致转录抑制是恶性肿瘤发生的重要机制之一,hgLH1、E-cadherin及p16INK4a基因在多种恶性肿瘤中都已被证实存在较高频率的甲基化.本研究通过检测食管鳞癌组织及癌旁组织中hMLH1、E-cadherin,p16INK4a基因启动子甲基化的发生情况,探讨hMLH1、E-cadherin、p16INK4a基因启动子甲基化在食管鳞癌发生发展中的作用.方法:采用酚-氯仿法提取105例食管鳞癌组织及癌旁组织的基因组DNA,应用甲基化特异性PCR对所提DNA进行hMLH1、E-cadherin、p16INK4a基因甲基化检测.采用EnVison免疫组织化学二步法对癌组织中上述3种基因蛋白表达进行检测.结果:癌组织中E-cadherin、hMLH1、p16INK4a基因启动子甲基化的阳性率分别为57.1%(60/105)、20.9%(22/105)和50.5%(53/105),而癌旁食管组织中相应的3个基因的甲基化率分别为10.5%(11/105)、1.9%(2/105)和7.6%(8/105),均显著低于癌组织.E-cadherin(P=0.021)及p16INK4a(P=0.026)基因甲基化与蛋白表达缺失密切相关,而hMLH1基因甲基化与蛋白表达无显著相关性.E-cadherin基因启动子甲基化与淋巴结转移有关(P=0.016),p16INK4a基因启动子甲基化与低分化癌有关性(P=0.024).hMLH1基因甲基化与各项临床病理特征均无关.结论:食管鳞癌中p16INK4a基因启动子甲基化与相应蛋白表达缺失密切相关,且在低分化癌中更多见;E-cadherin基因启动子甲基化与相应蛋白质表达缺失有相关性,并且有淋巴结转移多见的显著特征,这2个基因的甲基化位点与食管鳞癌密切相关.hMLH1基因甲基化可能并不直接参与食管鳞癌的发生、发展.     

P16INK4a和RASSF1a启动子甲基化在非小细胞肺癌中的研究

目的探讨抑癌基因p16INK4a和RASSF1a启动子甲基化在非小细胞肺癌中的作用。方法应用甲基化特异的PCR（methyl-specific PCR,MSP）和RT-PCR法测定基因的甲基化率与mRNA的转录水平,回收PCR产物测序。结果在NSCLC癌/癌旁组织中的甲基化率分别是RASSF1a为55%和10%,p16INK4a为43%和12%,p16INK4a和RASSF1a的甲基化率在〉65岁组高于≤65岁组,两基因甲基化率均随吸烟指数的增加而增高,并且随TNM临床进展而逐渐增加;p16INK4a甲基化率鳞癌组高于腺癌组。甲基化的NSCLC标本mRNA转录失活或下降,在细胞株水平5-aza-deoxycytidine（5-Aza-CdR）处理后,甲基化而转录沉默的细胞株恢复转录活性。结论启动子甲基化是调节p16^INK4a和RASSF1a转录的重要机制,5-Aza-CdR具有逆转甲基化而恢复转录的作用。     

肝癌患者p16基因甲基化与DNMTs表达相关性分析

目的:研究p16基因启动子区域异常甲基化所导致的基因表达异常在肝癌形成过程中的作用,探讨p16基因甲基化与DNMTs(DNMT1、DNMT2、DNMT3A和DNMT3B)表达之间的相关性。方法:检测肝癌患者癌组织、癌旁组织和肝硬化组织中p16基因的异常甲基化状态及p16、DNMTs基因mRNA的表达水平;采用甲基化特异性PCR技术检测甲基化状态,荧光定量技术检测mRNA的表达。结果:p16基因在肝癌组织、肝硬化组织和癌旁组织中的甲基化率分别为70.5%(31/44)、37.1%(13/35)和9.1%(4/44),肝癌组织和肝硬化组织中的甲基化改变与癌旁组织比较差异有统计学意义,P<0.01。31例甲基化阳性组织中17例p16基因表达降低或缺失,13例甲基化阴性组织中2例基因表达降低或缺失,甲基化阳性与阴性的p16基因表达水平存在明显差异。癌组织和肝硬化组织中4种DNMT mRNA水平均高于相应癌旁组织。其中DNMT1、DNMT3A和DNMT3BmRNA的表达水平差异有统计学意义,DNMT1:P值分别为0.009和0.020;DNMT3A:P值分别为0.005和0.010;DNMT3B:P值分别为0.039和0.036。DNMT2mRNA的表达水平虽然高于相应癌旁组织,但差异无统计学意义,P值分别为0.120和0.350。DNMT1、DNMT 3A和DNMT3B的表达与p16甲基化有相关性,P值分别为0.013、0.025和0.041。结论:p16基因甲基化是肝癌的早期、频发事件,其改变是其基因表达下降甚至失活的重要原因。DNMTs活性的改变可能促进p16基因的异常甲基化。     

Expression and methylation status of the FHIT gene in acute myeloid leukemia and myelodysplastic syndrome.

To clarify the role of fragile histidine triad (FHIT) in hematological malignancies, we examined the methylation status and the expression level of the FHIT gene in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) cells in comparison with the methylation of the p15(INK4B) gene. The FHIT methylation was found in 13 of 94 (13.8%) AML and 22 of 40 (55.0%) MDS cases, but not in normal mononuclear cells (MNCs). Both the frequency and density of methylation increased in the advanced-stages MDS and the relapsed AML cases. Although FHIT and p15(INK4B) methylations were not correlated in MDS and AML, increased FHIT methylation at the relapse in AML was associated with p15(INK4B) methylation. The median expression level in AML was significantly higher than in normal MNCs, although the median expression level in those with methylation was significantly lower than in those without methylation. Furthermore, the methylation level at relapse was significantly higher than at diagnosis in AML. These results suggested that FHIT methylation was accumulated through the disease progression of MDS and AML, and the role of the FHIT gene as a tumor suppressor seemed different in AML and MDS.     

High-risk myelodysplastic syndromes and hypermethylation of the p15Ink4B gene

Recent studies have elucidated that not only genetic alterations but also epigenetic changes may play an important role in carcinogenesis. In particular, de novo methylation of CpG islands within the promoter region associated with the inactivation of tumor suppressor genes (TSGs) has been demonstrated in various malignancies. Since de novo acute myelogenous leukemia shows frequent inactivation of the p15INK4B gene through the promoter methylation only, we investigated the methylation status of the p15INK4B gene in myelodysplastic syndrome (MDS). In MDS, the p15INK4B gene is also frequently hypermethylated at the promoter region located at the 5'-CpG island of exon 1. Association of frequent and strong methylation with high-risk MDS suggested that promoter methylation of the p15INK4B gene plays an important role as a late event during MDS progression. Since several TSGs and growth regulatory genes, including the p15INK4B gene, may be inactivated through promoter hypermethylation in hematological malignancies, modulation of the methylation status may be considered as a novel treatment modality in MDS.     

Methylation status of the p15INK4B gene in hematopoietic progenitors and peripheral blood cells in myelodysplastic syndromes.

We previously reported that the hypermethylation of the p15INK4B gene promoter was frequently observed in myelodysplastic syndromes (MDS), and that it may be associated with disease progression. An unanswered question is whether p15INK4B gene methylation is restricted to undifferentiated blastic cells, or whether differentiated cells such as granulocytes or erythrocytes of MDS origin also harbor this epigenetic alteration. In this study, we analyzed the methylation status of the p15INK4B gene in MDS by the methylation-specific PCR (MSP) method, which is more sensitive than Southern blotting. The bone marrow mononuclear cells (BM-MNCs) of 23 MDS patients were analyzed, and six of them showed p15INK4B methylation. Progenitor assay with methylcellulose medium was also performed in all patients. In two of the six patients with p15INK4B-methylated BM-MNCs, erythroid and/or non-erythroid colonies formed were subjected to molecular analysis. Colonies with and without p15INK4B methylation were detected in both patients. Furthermore, X-chromosome inactivation (XCI) pattern of each colony was simultaneously determined by MSP-based human androgen receptor gene analysis (HUMARA-MSP), and all p15INK4B-methylated colonies showed the same XCI pattern, which was dominant among the colonies, while p15INK4B-unmethylated colonies showed both patterns of XCI, in each of the two patients. We then examined the methylation status of the p15INK4B gene of granulocyte (PB-PMN) fractions from 10 patients with available peripheral blood cells. In all four patients with p15INK4B-methylated BM-MNCs, their PB-PMNs showed p15INK4B methylation. These results suggest that p15INK4B methylation in hematopoietic cells in MDS patients is restricted to the MDS clone but not necessarily to blast cells.     

P15INK4b gene methylation and myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are clonal disorders, which frequently undergo leukemic transformation. It was recently shown that the promoter of the p15INK4b but not the p16INK4a gene is frequently and selectively hypermethylated in MDS. The p15INK4b gene is a cyclin dependent kinase inhibitor gene, which is actively transcribed after TGFbeta exposure. Methylation of the p15INK4b gene is significantly correlated with blastic bone marrow involvement, and sequential analyses have shown that methylation increases with disease evolution toward AML. These data strongly suggest that p15INK4b gene methylation is a mechanism allowing leukemic cells to escape to inhibitory signals from the bone marrow environment, however the exact role of p15INK4b gene methylation in disruption of the signal mediated by TGFbeta remains to be investigated.     

Comparative analysis of hypermethylation of cell cycle control and DNA-mismatch repair genes in low-density and CD34+ bone marrow cells from patients with myelodysplastic syndrome

Hypermethylation of CpG islands within the promoter region is one of the mechanisms by which genes are inactivated and may be one of the reason for silencing of cell cycle control or DNA-mismatch repair genes in myelodysplastic syndrome (MDS). Since the function of cell cycle control genes including the cyclin-dependent kinase inhibitors known as p15(INK4b) and p16(INK4a), as well as p14(ARF) which blocks MDM-2 (an inhibitor of p53), the retinoblastoma (RB1) protein and the mismatch repair gene MGMT is critical for hematopoietic proliferation and differentiation, we performed methylation specific polymerase chain reaction (MSP) in low-density, non-adherent bone marrow cells from 49 patients with MDS. In addition, expression of p15(INK4b) and RB1 was analysed by quantitative real-time PCR. From selected patients, we analyzed the methylation pattern of cell cycle control genes in CD34+ bone marrow cells. Thirty-nine of 49 cases (80%) had at least one of five genes methylated in our MDS samples by analysing low-density non-adherent bone marrow cells. The frequency of p15(INK4b) methylation was 34 of 49 samples (69%). The incidence of methylation of both p14(ARF) and p16(INK4a) was four of 49 (8%). RB1 gene was methylated in seven samples (14%) and each patient had RA. Interestingly, none of these genes were methylated in the purified CD34+ hematopoietic stem cells from the MDS patients. Furthermore, all our RARS patients had a methylated p15(INK4b) promoter correlating with non-detectable expression of this gene in bone marrow cells from those patients. These results indicate that hypermethylation of cell cycle control genes in MDS may occur late during the differentiation of myelodysplastic stem cells.     

Role of p15(INK4B) Methylation in Patients With Myelodysplastic Syndromes: A Systematic Meta-Analysis

BackgroundTumor suppressor gene cyclin-dependent kinase inhibitor 2B (p15(INK4B)) methylation has been frequently reported in myelodysplastic syndromes (MDS). However, the association between p15(INK4B) methylation and MDS remains elusive. Thus, this meta-analysis was first conducted to evaluate the clinical significance of p15(INK4B) methylation in MDS.Materials and MethodsEligible studies were identified via an online electronic databases search. The overall odds ratios (ORs) or hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated.ResultsTwenty-eight studies published between 1997 and 2017 were identified, including 1205 MDS patients and 243 nontumor controls. No evidence of heterogeneity was found in our study. p15(INK4B) methylation was significantly elevated in MDS compared with nontumor controls (OR, 10.37; P < .001). In addition, p15(INK4B) methylation was significantly higher in advanced MDS than in early MDS (OR, 4.70; P < .001) and was linked to an unfavorable overall survival (multivariate analysis: HR, 1.78; 95% CI, 1.23-2.71). Subgroup analyses on the basis of ethnicity and detection method showed that the results remained significant in different subgroups (all Ps < .05).ConclusionOur findings suggest that p15(INK4B) methylation might play an important role in the development, progression, and poor prognosis of MDS. More prospective studies with larger study populations are needed.     

Aberrant methylation and impaired expression of the p15(INK4b) cell cycle regulatory gene in chronic myelomonocytic leukemia (CMML).

The important cell cycle regulatory gene p15(INK4b) has been shown to be inactivated in acute myeloid leukemia and myelodysplastic syndrome. Little is known about the expression and epigenetic modification of this gene in chronic myelomonocytic leukemia (CMML) that belongs to the myelodysplastic/myeloproliferative disorders (MDS/MPD) with a high proportion of blastic transformation. Analysis of bone marrow trephines in a series of 33 CMML cases showed an aberrant p15(INK4b) gene methylation in up to 58% of cases. Methylation was analyzed employing different methylation-specific PCR and genomic sequencing protocols. It turned out to be spread over a broad area of the 5' region and exhibited substantial heterogeneity between cases and even in individual patients. The degree of aberrant methylation was correlated with a reduced mRNA as well as reduced protein expression, and was associated with a higher expression of DNA methyltransferase DNMT 3A. We conclude that aberrant gene methylation is a frequent event in CMML that might contribute to the pathogenesis of this MDS/MPD.