儿童急性淋巴细胞白血病患者p73基因异常表达的研究

目的 探讨儿童急性淋巴细胞因病（ALL）发生及发展的机制。方法 应用RT－PCR技术检测61例ALL细胞系和53例儿童ALL患者的p73基因mRNA表达情况，并结合患者的临床资料进行分析。应用DNA甲基化酶谱测定、亚硫酸氢钠修饰的PCR和PCR产物测序等技术对61例ALL细胞系p73基因第1外显子的甲基化进行检测。结果 61个ALL细胞系中p73mRNA阴性表达率为31．1％（61个中19个）；53例原发性儿童ALL患者中，p73 mRNA阴性表达率为26．4％（53例中14例），p73 mRNA阴性表达与ALL无病生存期、总生存期的降低有明显关系。61个ALL细胞系中，39．3％存在p73基因的高甲基化。正常淋巴细胞和不存在p73基因高甲基化的细胞系表达p73 mRNA，大多数高甲基化的细胞系不表达p73 mRNA。结论 儿童ALL患者中p73 mRNA存在较高的阴性表达，其主要机制为p73基因高甲基化，p73基因失活在ALL的发生及发展中起重要作用，p73 mRNA检测对判断儿童ALL患者的预后有一定临床意义。     

p73基因异常表达与急性淋巴细胞白血病相关性的研究

目的探讨急性淋巴细胞白血病(ALL)发生发展的机制。方法应用RT-PCR技术检测42例ALL患者的p73基因mRNA表达情况,并结合患者的临床资料进行分析,同时采用限制性内切酶酶切结合多聚酶链反应方法(REP法)检测p73基因第一外显子甲基化情况。结果42例ALL患者甲基化检测结果28.6%(12/42)存在甲基化,甲基化患者p73mRNA均阴性表达,正常对照组和不存在p73基因甲基化的病人表达p73mRNA。p73mRNA阴性表达与ALL患者首次化疗既获完全缓解及平均缓解时间的降低有明显关系。结论ALL患者p73基因存在较高的阴性表达,p73基因失活在ALL的发生发展中起重要作用。p73基因失活主要原因之一是过度甲基化。p73mRNA检测对判断ALL患者预后有一定的意义。     

子宫内膜癌中p16蛋白异常表达及基因缺失和甲基化的研究

目的:研究子宫内膜癌中p16蛋白与其基因缺失及CpG岛甲基化的关系。方法:对36例子宫内膜癌标本分别用免疫组化方法和PCR技术检测MTS1/p16蛋白表达和基因纯合性缺失及第一外显子异常甲基化情况。结果:36例癌组织中14例p16蛋白表达阳性,蛋白表达缺失率为61.11%(22/36);9例发生基因缺失,12例发生甲基化,未发现基因缺失与甲基化同时存在的病例,p16基因总失活率58.33%;22例p16蛋白表达缺失标本有19例基因失活。结论:p16蛋白缺失程度与子宫内膜癌组织学分级和临床分期呈正相关;p16蛋白缺失程度与p16基因缺失和甲基化有关。     

非小细胞肺癌患者p53基因突变检测的临床意义

目的探讨非小细胞肺癌（NSCLC）患者呼出气冷凝液（EBC）中p53基因突变检测的临床意义。方法采用巢式PCR结合DNA测序法,检测53例NSCLC患者EBC中p53基因第5～8外显子的突变情况,并以32例健康体检者EBC标本作为对照。结果肺癌组53例EBC标本中扩增到1）53基因26例,其中10例检测到p53基因突变,突变率为38．5％（10／26）;正常对照组32例EBC标本中扩增到p53基因15例,但未检测到p53基因突变。结论p53基因突变可能参与NSCLC的发生发展,检测EBC中p53基因的突变对肺癌的早期诊断有一定的价值。     

淋巴细胞恶性肿瘤p16基因纯合缺失和突变的研究

为了探讨非霍奇金淋巴瘤(NHL)和急性淋巴细胞白血病(ALL)中p16基因纯合缺失和突变情况,应用聚合酶链反应(PCR)技术与DNA单链构象多态性分析(PCR-SSCP)及DNA测序技术,检测了45例NHL及20例ALL p16基因改变情况。结果发现45例NHL中有4例存在p16基因纯合缺失,占8.9％,20例ALL中有5例存在p16基因纯合缺失,占25％。1例NHL在第2外显子上游第49密码子出现错义突变,由GCC突变为GAC。1例ALL在第2外显子上游65密码子出现错义突变,由GCC改变为GCA。研究结果表明,NHL和ALL中存在一定比例的p16基因纯合缺失,而p16基因突变率较低,提示p16基因纯合缺失在NHL和ALL发生发展中起一定作用。     

喉鳞状细胞癌中p16INK4a基因甲基化状况及表达

目的研究喉鳞状细胞癌p16^（INK4a）基因启动子区域5′CpG岛的甲基化状况,探讨基因异常甲基化与蛋白表达及其临床病理指标的关系。方法采用甲基化特异性PCR检测30例喉鳞状细胞癌及15例远离肿瘤的正常喉黏膜中p16^（INK4a）基因启动子区域5′CpG岛的甲基化状况,并应用免疫组化EnVision法检测p16^（INK4a）蛋白的表达情况。结果30例喉鳞状细胞癌中p16^（INK4a）基因启动子区5′CpG岛甲基化率76.7%（23/30）;p16^（INK4a）蛋白缺失率为93.3%（28/30）。15例正常喉黏膜中未检测到p16^（INK4a）基因异常甲基化,而且其相应蛋白表达均为阳性。p16^（INK4a）基因甲基化状况与其蛋白表达和临床分期密切相关。结论p16^（INK4a）基因5′CpG岛异常甲基化在喉鳞状细胞癌中频率很高,可能在喉癌发生、发展中扮演重要角色;而且这可能是一个早期事件,其临床早期诊断和基因治疗意义均值得进一步深入探讨。     

结肠直肠癌KRAS、NRAS、BRAF基因突变及其与临床病理特征、p53蛋白表达间相关性研究

目的：筛查肠直肠癌患者的KRAS、NRAS和BRAF基因亚型突变状态, 并分析其与患者临床病理特征及p53蛋白表达情况间的相关性。方法：收集110例手术切除的结肠直肠癌病理资料及组织学样本, 总结临床病理特征;采用突变阻滞扩增系统法检测KRAS、NRAS基因2、3、4号外显子第12、13、61、117、146密码子及BRAF基因15号外显子第600密码子的突变情况;采用免疫组织化学（免疫组化）法检测p53蛋白的表达情况。结果：KRAS基因突变率为45.4%（50/110）, 其中49例患者检测到2号外显子第12和13密码子突变, 1例检测到4号外显子第117和146密码子突变;NRAS基因突变率为6.3%（7/110）, 其中3例检测到2号外显子第12和13密码子突变, 3例检测到3号外显子第61密码子突变, 1例检测到4号外显子第146密码子突变, 且与KRAS基因存在共突变;BRAF基因15号外显子第600密码子突变率为2.7%（3/110）;p53蛋白阳性表达率为57.3%（63/110）, 其中27例患者存在KRAS基因突变, 7例存在NRAS基因突变, 2例存在BRAF基因突变。KRAS基因突变率与患者的淋巴结转移显著相关（P<0.05）;而NRAS基因突变与其组织分型及p53蛋白表达显著相关（P<0.05）;BRAF基因突变率与右半结肠癌显著相关（P<0.05）。结论：KRAS与结肠直肠癌发生、发展的分子机制关系密切;BRAF基因突变仅见于右半结肠, 提示右半结肠癌发生机制可能有其特殊性;p53蛋白表达与NRAS基因突变之间是否存在相互作用关系值得进一步研究。     

儿童急性淋巴细胞白血病AKAP12启动子区域异常甲基化

目的探讨儿童急性淋巴细胞白血病（ALL）中A激酶锚定蛋白12（AKAP12）基因启动子区域CpG岛异常甲基化情况及其与临床病理参数之间的关系。方法用甲基化特异性聚合酶链反应（MSP）检测儿童ALL患者骨髓和对照骨髓以及淋巴细胞白血病细胞株6T—CEM中AKAP12基因启动子区域CpG岛甲基化状态,并采用亚硫酸盐测序法检测启动子区域发生甲基化的频率。采用荧光定量逆转录PCR（FQ—RT—PCR）检测6T—CEM中,经过甲基化酶抑制剂（5-Aza—CdR）处理后,AKAP12恢复表达的情况。结果32例ALL患者MSP结果显示AKAP12基因甲基化比率为62．5％（20／32）,但与患者的临床病理学参数均无显著相关。经过5-Aza-CdR处理后,可使6T-CEM中AKAP12恢复表达,且表达强度与剂量成正比。结论AKAP12基因启动子的异常甲基化与ALL的发生有密切的联系,AKAP12基因启动子甲基化有望成为一个诊断ALL的分子标志物。     

p73基因及其在急性淋巴细胞白血病中的研究进展

p73基因是p53基因家族中发现的一个新成员，是一个新的抑癌基因。由于其特殊的定位及其与p53结构和功能的相似性，人们对其进行了较深入的研究，发现其在急性淋巴细胞白血病（ALL）的发生、发展及预后等方面具有一定意义。本文拟对p73基因的研究进展及在ALL中的表达和意义作一综述。     

瘢痕疙瘩形成与发展中p53基因突变的意义

目的:通过检测瘢痕疙瘩p53基因第4～8外显子的突变,探讨p53基因突变在瘢痕疙瘩形成与发展中的意义。方法:取手术切除的瘢痕疙瘩和正常瘢痕各12例,并分别取正常皮肤对照,采用聚合酶链反应-单链构象多态性分析方法(PCR-SSCP),检测p53基因的突变情况。结果:12例瘢痕疙瘩标本中有9例p53基因外显子4,5,6,7出现点突变和移码突变,正常瘢痕标本、正常皮肤标本均未检出突变。结论:p53基因突变是瘢痕疙瘩形成和发展的重要因素之一。     

Absence of hereditary p53 mutations in 10 familial leukemia pedigrees.

Germline p53 mutations have been identified in the Li-Fraumeni syndrome but the role of such mutations in familial leukemia is not established. The p53 gene was examined by single-strand conformation polymorphism analysis of exons 4-8 in 10 families with multiple members affected with leukemia. The diagnoses included acute and chronic leukemias and Hodgkin's disease. Identified in two families were p53 mutations that were nonhereditary. These included a 2-bp deletion in exon 6 found in the lymphoblast DNA of one child whose sibling, cousin, and several adult relatives had acute leukemia. The other nonhereditary p53 mutation was a transition at codon 248 (CGG to CAG, arginine to glutamine) found in the lymphoblasts of a patient with a preleukemic syndrome and acute lymphoblastic leukemia (ALL) whose brother is a long-term survivor of ALL. Thus, p53 mutations were found to occur in two families but both were nonhereditary. Moreover, in the remaining eight families no p53 mutation was identified in the regions of p53 where most mutations have been found in other cancers. Although p53 mutations sometimes may be present, they do not appear to be a primary event responsible for hereditary susceptibility to familial leukemia. This study suggests involvement of other genes or mechanisms.     

Loss of p73 promotes dissemination of Myc-induced B cell lymphomas in mice

Mice engineered to express c-Myc in B cells (Eμ-myc mice) develop lethal lymphomas in which the gene encoding the p53 tumor suppressor is frequently mutated. Whether the p53 homolog p73 also functions as a tumor suppressor in vivo remains controversial. Here we have shown that p73 loss does not substantially affect disease onset and mortality in Eμ-myc mice. However, it does alter the phenotype of the disease. Specifically, p73 loss decreased nodal disease and increased widespread extranodal dissemination. We further found that p53 acted as the dominant tumor suppressor during the onset of Eμ-myc–driven B cell lymphomagenesis, while p73 modulated tumor dissemination and extranodal growth. Immunophenotyping and expression profiling suggested that p73 loss allowed increased maturation of malignant B cells and deregulated genes involved in lymphocyte homing and dissemination of human lymphomas. Consistent with this, p73 expression was frequently downregulated in a large cohort of human mature aggressive B cell lymphomas, and both the incidence and degree of p73 downregulation in these tumors correlated with their extranodal dissemination status. These data indicate that p73 is a modifier of Myc-driven lymphomas in mice, favoring tumor dissemination, and suggest that p73 could be a biomarker for human B cell lymphoma dissemination, a notion that can now be tested in clinicopathologic correlation studies.     

RITA inhibits multiple myeloma cell growth through induction of p53-mediated caspase-dependent apoptosis and synergistically enhances nutlin-induced cytotoxic responses

Mutations or deletions of p53 are relatively rare in multiple myeloma (MM), at least in newly diagnosed patients. Thus, restoration of p53 tumor suppressor function in MM by blocking the inhibitory role of murine double minute 2 (MDM2) is a promising and applicable therapeutic strategy. RITA and nutlin are two new classes of small molecule MDM2 inhibitors that prevent the p53-MDM2 interaction. Earlier reports showed p53-dependent activity of RITA in solid tumors as well as in leukemias. We and others recently described nutlin-induced apoptosis in MM cells, but it remains unclear whether RITA exerts antimyeloma activity. Here, we found that RITA activates the p53 pathway and induces apoptosis in MM cell lines and primary MM samples, preferentially killing myeloma cells. The activation of p53 induced by RITA was mediated through modulation of multiple apoptotic regulatory proteins, including upregulation of a proapoptotic protein (NOXA), downregulation of an antiapoptotic protein, Mcl-1, and activation of caspases through extrinsic pathways. Moreover, a number of key p53-mediated apoptotic target genes were identified by gene expression profiling and further validated by quantitative real-time PCR. Importantly, the combination of RITA with nutlin displayed a strong synergism on growth inhibition with the combination index ranging from 0.56 to 0.82 in MM cells. Our data support further clinical evaluation of RITA as a potential novel therapeutic intervention in MM.     

Evaluation of oligonucleotide arrays for sequencing of the p53 gene in DNA from formalin-fixed, paraffin-embedded breast cancer specimens

BACKGROUND: Routine tissue processing has generated banks of paraffin-embedded tissue that could be used in retrospective cohort studies to study the molecular changes that occur during cancer development. The purpose of this study was to determine whether a p53 microarray could be used to sequence the p53 gene in DNA extracted from formalin-fixed, paraffin-embedded (FFPE) tissues. METHODS: DNA was extracted from 70 FFPE breast cancer tissue specimens. p53 was sequenced with an oligonucleotide microarray (p53 GeneChip; Affymetrix), and the results were compared with the results obtained from direct sequencing. RESULTS: DNA was extracted from 62 of 70 cases. We identified 26 mutations in 24 of the 62 cases by the p53 GeneChip. No polymorphisms were detected, and exon 4 could not be evaluated in 20 cases. There were 43 genetic alterations detected by direct sequencing in 35 of the 62 cases. These consisted of 26 polymorphisms and 17 mutations in exons or splice sites. Fifteen mutations were identified by both methods. Direct sequencing detected significantly more gene alterations (43 of 54) in DNA extracted from FFPE tissue than the p53 GeneChip (26 of 54; P = 0.018). However, if the changes in exon 4 were eliminated from this comparison, the p53 GeneChip detected 26 of 27 mutations compared with direct sequencing, which identified 16 of 27 mutations. (P = 0.016). CONCLUSIONS: A combination of oligonucleotide microarray and direct sequencing may be necessary to accurately identify p53 gene alterations in FFPE breast cancer. The p53 GeneChip cannot be used to detect exon 4 polymorphisms (codon 72) in FFPE breast cancer tissue.     

多发性骨髓瘤中p16、p15基因甲基化及其mRNA表达的研究

目的 探讨p16、p15基因的高甲基化及其mRNA转录阻抑与多发性骨髓瘸的发病和进展之间的关系。方法 采用甲基化敏感的限制性内切酶联合聚合酶链反应方法（REP法）,检测了28例多发性骨髓瘸患者骨髓细胞p16、p15基因5端启动子区的甲基化状态,采用逆转录聚合酶链反应（RT-PCR）方法检测多发性骨髓瘸患者p16、p15基因mRNA表达情况。结果 p16、p15基因启动子区过度甲基化率分别为57．14％（16／28）、64．28％（18／28）,53．57％（15／28）患者同时存在p16、p15基因启动子区过度甲基化。大多数存在甲基化的患者不表达p16、p15基因mRNA。结论 p16、p15基因的高甲基化与多发性骨髓瘸的发病有关,p16、p15基因甲基化与其转录阻抑高度相关。     

NPM基因在人淋巴母细胞中的差异表达与染色体不稳定性

目的：研究NPM基因与染色体不稳定性（CIN）、细胞增殖及p53的关系，为阐明恶性血液病发生的分子机制提供参考。方法：采用软琼脂克隆形成法、常规染色体分析和G显带法检测人淋巴母细胞TK6（wtp53）、WTK1（mtp53）和正常人淋巴细胞永生化细胞（HNILL）的细胞增殖、染色体数量变化和5号染色体质量排，并观察Olomoucine对其的影响；用Sanger测序法和Western Blot方法分别测定NPM第12外显子的DNA序列、NPM蛋白和磷酸化蛋白的表达。结果：WTK1细胞的克隆形成能力和多倍体率均显著高于TK6细胞，同时WTKI细胞的NPM蛋白和磷酸化蛋白表达亦明显高于TK6细胞，且它们均又显著高于HNILL细胞；3株细胞均未发现5号染色体的重排和NPM第12外显子编码区的突变。用Olomoucine抑制NPM蛋白磷酸化后WTK1细胞的多倍体率明显降低。结论：WTK1、TK6和HNILL细胞的增殖能力、CIN与NPM蛋白和磷酸化蛋白表达呈正相关，而且与p53状态密切相关。