少突胶质细胞瘤分子遗传学研究进展

胶质瘤是中枢神经系统最常见的肿瘤,国内外统计其发病率占所有原发性中枢神经系统肿瘤的43％～51％。由于其生长部位、生长方式的特点及潜在恶性倾向的生物学行为,造成目前手术切除或放化疗均难以奏效。少突胶质细胞瘤是胶质瘤中的一种独立类型,约占颅内肿瘤的4．39％。近些年来,有科学家发现少突胶质细胞瘤虽然也呈弥漫浸润     

中枢神经细胞瘤的临床病理特征和预后

目的：探讨中枢神经细胞瘤（CNC）的临床病理特征及其与预后的关系。方法：应用光镜、电镜检查观察了22例CNC的组织病理、超微结构特点,应用免疫组织化学染色观察了突触素、神经元特异性烯醇化酶（NSE）、Leu-7、胶质纤维酸性蛋白（GFAP）、髓磷脂碱性蛋白（MBP）及增殖细胞核抗原（PCNA)董关CNC的表达情况。结果：本组病例年龄4－14岁,平均27．9岁。肿瘤均发生于脑室。随访18例,14例生存8个月至14年11个月;4例死亡,平均生存时间70．7个月。CNC组织学特点,瘤细胞有明显的核周空晕,呈蜂窝状结构,特征性改变为无核纤维岛。细胞异型、核分裂象及灶性坏死罕见。免疫组织化学染色突触素、NSE、Leu-7阳性表达,GFAP7有MBP阴性反应,PCNA极少数细胞阳性。超微结构特点为圆形瘤细胞可见多量细胞突起,突起内含微管、神经分泌颗粒、透明囊泡及溶酶体样结构。结论：常规光镜检查难以鉴别CNC和少突胶质细胞瘤,免疫组织化学和电镜对确诊CNC很重要。CNC一般预后良好。间变性组织学特点与生物学行为之间的关系仍不清楚。     

少突胶质细胞肿瘤染色体1p、19q和10q杂合性缺失与临床预后的关系

目的 探讨少突胶质细胞肿瘤微卫星变异的遗传和分子特性及其与临床预后的关系。方法 26例少突胶质细胞瘤和25例伴有少突胶质细胞瘤成分的胶质母细胞瘤成对的血和肿瘤标本DNA提取后,进行微卫星不稳定性分析染色体1、19q和10q杂合性缺失。结果 54％少突胶质细胞瘤检出1pLOH,58％检出19qLOH,35％检出10q LOH,其中50％间变性少突胶质细胞瘤出现10q LOH。1p／19q LOH相伴存,二者密切相关（P〈0．0001）;40％GBMO检出1pLOH,仅4例1p LOH伴10q LOH;60％检出19q LOH,64％检出10q LOH。结论 1P和19q LOH是少突胶质细胞瘤分子和遗传特性之一,并且与化疗敏感和预后好有关,10qLOH是少突胶质细胞瘤进展标志。1PLOH与长PFS有关,10qLOH与短PFS有关。GBMO分子表型不同于GBM。     

少枝胶质细胞瘤的形态观察

目的研究少枝胶质细胞瘤（ＯＤＧ）的超微结构及组织学特性。方法用光镜，部分用电镜及免疫组化观察６５例ＯＤＧ。结果根据ＷＨＯ有关ＯＤＧ病理分级，６５例中Ⅰ级１９例，Ⅱ级３２例，Ⅲ级１４例。结论ＯＤＧ中瘤细胞出现胶质微丝是异质性分化的结果。除按瘤细胞分化程度分级外，细胞密度、核分裂数亦有重要意义。     

CIC蛋白失表达在少突胶质细胞肿瘤诊断及预后判断中的意义北大核心CSCD

目的探讨CIC蛋白失表达在少突胶质细胞肿瘤中作为预测染色体lp／19q共缺失初筛检测方法的可行性及其对预后的影响。方法回顾性分析首都医科大学宣武医院病理科113例形态学具有少突胶质细胞瘤特征的胶质瘤,分别进行染色体lp／19q共缺失荧光原位杂交（FISH）检测及CIC蛋白免疫组织化学标记。分析CIC蛋白失表达与染色体1p／19q共缺失的相关性,并探讨其与预后的关系。结果在113例组织学诊断为少突胶质细胞肿瘤中,CIC蛋白失表达率为59．3％（67／113）,不同的组织学类型中失表达率不同,在只含有少突胶质细胞成分的肿瘤中失表达率（85．7％．42／49）比混合性的胶质瘤中（39．1％,25／64）高（P〈0．01）。CIC蛋白失表达预测1p／19q共缺失的敏感性和特异性分别为76．1％（54／71）和71．1％（27／38）,假阳性率和假阴性率分别为16．9％（11／65）和38．6％（17／44）。按照2016版（（WHO中枢神经系统肿瘤分类第4版修订版》,本组病例中63例整合诊断符合少突胶质细胞瘤／间变型少突胶质细胞瘤,IDH突变及1p／19q共缺失;CIC蛋白失表达率为81．0％（51／63）,其预测1p／19q共缺失的敏感性和特异性分别提高至81．0％（51／63）和76．9％（20／26）,假阳性率和假阴性率分别降至10．5％（6／57）和37．5％（12／32）。此时,应用Kaplan—Meier法分析CIC蛋白失表达对预后的影响,发现CIC蛋白失表达组比阳性表达组预后稍好,但二者差异无统计学意义（总生存期：P=0．218;无进展生存期：P=0．249）。结论利用免疫组织化学检测CIC蛋白失表达情况,可以作为染色体1p／19q共缺失的一种初筛检测方法。CIC蛋白失表达与预后无关。     

即时荧光定量PCR微卫星分析技术检测少突胶质细胞肿瘤染色体1p/19q杂合性缺失

目的研究少突胶质细胞肿瘤染色体1p／19q杂合性缺失（LOH）情况。方法采用即时荧光定量PCR微卫星分析技术对28例少突胶质细胞肿瘤进行染色体1p／19qLOH检测。结果28例少突胶质细胞肿瘤染色体中有24例（85．7％）发生1pLOH;有18例（64．3％）发生19qLOH;有17例（60．7％）发生1p／19q联合性LOH;25例有1P或19qLOH。结论即时荧光定量PCR微卫星分析技术特异性高、方便快捷,可以用于石蜡包埋组织标本染色体杂合性缺失的检测。大多数少突胶质细胞肿瘤发生了1p／19qLOH。     

少突胶质细胞瘤染色体1p/19 q杂合性缺失与p53蛋白表达的相关性研究

目的 探讨少突胶质细胞瘤染色体1p/19q杂合性缺失及p53蛋白的表达情况,与星形细胞起源的肿瘤进行比较研究并探讨其意义.方法 选择2004-2005年间,经病理组织学诊断为不同类型和级别的胶质瘤合计191例,包括:WHOⅡ级少突胶质细胞瘤116例,其中30例为新鲜组织;间变性少突胶质细胞瘤45例和不同级别星形细胞起源的肿瘤石蜡组织30例;采用PCR-微卫星技术检测染色体1p/19q杂合性缺失情况;采用免疫组织化学方法 对184例胶质瘤石蜡切片p53蛋白表达情况进行半定量分析.结果 86例WHO Ⅱ级少突胶质细胞瘤石蜡标本染色体1p缺失率为69.8%(60/86)、19q缺失率为64.0%(55/86)、1p/19q联合缺失率为57.0%(49/86);45例间变性少突胶质细胞瘤中,1p缺失率为71.1%(32/45)、19q缺失率为60.0%(27/45)、1p/19q联合缺失率为55.6%(25/45);两种级别间差异无统计学意义(P>0.05).30例WHO Ⅱ级少突胶质细胞瘤新鲜标本染色体1p缺失率为70.0%(21/30)、19q缺失率为63.3%(19/30)、1p/19q联合缺失率为60.0%(18/30),与石蜡标本的缺失率比较差异无统计学意义(P>0.05).30例星形细胞起源的肿瘤染色体对应三种缺失率分别为23.3%(7/30)、33.3%(10/30)及20.0%(6/30),与少突胶质细胞瘤差异有统计学意义(P<0.05).86例WHO Ⅱ级少突胶质细胞瘤中,仅7例有p53蛋白阳性表达(占8.1%);45例间变性少突胶质细胞瘤中,有14例呈阳性表达(31.1%),两者差异有统计学意义(P=0.007).少突胶质细胞瘤p53蛋白阳性表达明显低于星形细胞起源的肿瘤(P=0.001).在间变性少突胶质细胞瘤中,染色体1p/19q杂合性缺失与p53蛋白阳性表达呈负相关(P<0.05).结论 石蜡和新鲜组织均可用于染色体1p/19q杂合性缺失的检测.在间变性少突胶质细胞瘤中,染色体1p/19q杂合性缺失与p53蛋白阳性表达呈负相关.检测少突胶质细胞瘤染色体1p/19q杂合性缺失和p53蛋白表达,对提高病理诊断的精确性、指导治疗及预后判断具有重要意义.     

少突胶质细胞瘤染色体1p/19 q杂合性缺失与p53蛋白表达的相关性研究

目的 探讨少突胶质细胞瘤染色体1p/19q杂合性缺失及p53蛋白的表达情况,与星形细胞起源的肿瘤进行比较研究并探讨其意义.方法 选择2004-2005年间,经病理组织学诊断为不同类型和级别的胶质瘤合计191例,包括:WHOⅡ级少突胶质细胞瘤116例,其中30例为新鲜组织;间变性少突胶质细胞瘤45例和不同级别星形细胞起源的肿瘤石蜡组织30例;采用PCR-微卫星技术检测染色体1p/19q杂合性缺失情况;采用免疫组织化学方法 对184例胶质瘤石蜡切片p53蛋白表达情况进行半定量分析.结果 86例WHO Ⅱ级少突胶质细胞瘤石蜡标本染色体1p缺失率为69.8%(60/86)、19q缺失率为64.0%(55/86)、1p/19q联合缺失率为57.0%(49/86);45例间变性少突胶质细胞瘤中,1p缺失率为71.1%(32/45)、19q缺失率为60.0%(27/45)、1p/19q联合缺失率为55.6%(25/45);两种级别间差异无统计学意义(P>0.05).30例WHO Ⅱ级少突胶质细胞瘤新鲜标本染色体1p缺失率为70.0%(21/30)、19q缺失率为63.3%(19/30)、1p/19q联合缺失率为60.0%(18/30),与石蜡标本的缺失率比较差异无统计学意义(P>0.05).30例星形细胞起源的肿瘤染色体对应三种缺失率分别为23.3%(7/30)、33.3%(10/30)及20.0%(6/30),与少突胶质细胞瘤差异有统计学意义(P<0.05).86例WHO Ⅱ级少突胶质细胞瘤中,仅7例有p53蛋白阳性表达(占8.1%);45例间变性少突胶质细胞瘤中,有14例呈阳性表达(31.1%),两者差异有统计学意义(P=0.007).少突胶质细胞瘤p53蛋白阳性表达明显低于星形细胞起源的肿瘤(P=0.001).在间变性少突胶质细胞瘤中,染色体1p/19q杂合性缺失与p53蛋白阳性表达呈负相关(P<0.05).结论 石蜡和新鲜组织均可用于染色体1p/19q杂合性缺失的检测.在间变性少突胶质细胞瘤中,染色体1p/19q杂合性缺失与p53蛋白阳性表达呈负相关.检测少突胶质细胞瘤染色体1p/19q杂合性缺失和p53蛋白表达,对提高病理诊断的精确性、指导治疗及预后判断具有重要意义.     

少突胶质细胞瘤染色体1p/19 q杂合性缺失与p53蛋白表达的相关性研究

目的 探讨少突胶质细胞瘤染色体1p/19q杂合性缺失及p53蛋白的表达情况,与星形细胞起源的肿瘤进行比较研究并探讨其意义.方法 选择2004-2005年间,经病理组织学诊断为不同类型和级别的胶质瘤合计191例,包括:WHOⅡ级少突胶质细胞瘤116例,其中30例为新鲜组织;间变性少突胶质细胞瘤45例和不同级别星形细胞起源的肿瘤石蜡组织30例;采用PCR-微卫星技术检测染色体1p/19q杂合性缺失情况;采用免疫组织化学方法 对184例胶质瘤石蜡切片p53蛋白表达情况进行半定量分析.结果 86例WHO Ⅱ级少突胶质细胞瘤石蜡标本染色体1p缺失率为69.8%(60/86)、19q缺失率为64.0%(55/86)、1p/19q联合缺失率为57.0%(49/86);45例间变性少突胶质细胞瘤中,1p缺失率为71.1%(32/45)、19q缺失率为60.0%(27/45)、1p/19q联合缺失率为55.6%(25/45);两种级别间差异无统计学意义(P>0.05).30例WHO Ⅱ级少突胶质细胞瘤新鲜标本染色体1p缺失率为70.0%(21/30)、19q缺失率为63.3%(19/30)、1p/19q联合缺失率为60.0%(18/30),与石蜡标本的缺失率比较差异无统计学意义(P>0.05).30例星形细胞起源的肿瘤染色体对应三种缺失率分别为23.3%(7/30)、33.3%(10/30)及20.0%(6/30),与少突胶质细胞瘤差异有统计学意义(P<0.05).86例WHO Ⅱ级少突胶质细胞瘤中,仅7例有p53蛋白阳性表达(占8.1%);45例间变性少突胶质细胞瘤中,有14例呈阳性表达(31.1%),两者差异有统计学意义(P=0.007).少突胶质细胞瘤p53蛋白阳性表达明显低于星形细胞起源的肿瘤(P=0.001).在间变性少突胶质细胞瘤中,染色体1p/19q杂合性缺失与p53蛋白阳性表达呈负相关(P<0.05).结论 石蜡和新鲜组织均可用于染色体1p/19q杂合性缺失的检测.在间变性少突胶质细胞瘤中,染色体1p/19q杂合性缺失与p53蛋白阳性表达呈负相关.检测少突胶质细胞瘤染色体1p/19q杂合性缺失和p53蛋白表达,对提高病理诊断的精确性、指导治疗及预后判断具有重要意义.     

少突胶质细胞瘤染色体1p/19 q杂合性缺失与p53蛋白表达的相关性研究

目的 探讨少突胶质细胞瘤染色体1p/19q杂合性缺失及p53蛋白的表达情况,与星形细胞起源的肿瘤进行比较研究并探讨其意义.方法 选择2004-2005年间,经病理组织学诊断为不同类型和级别的胶质瘤合计191例,包括:WHOⅡ级少突胶质细胞瘤116例,其中30例为新鲜组织;间变性少突胶质细胞瘤45例和不同级别星形细胞起源的肿瘤石蜡组织30例;采用PCR-微卫星技术检测染色体1p/19q杂合性缺失情况;采用免疫组织化学方法 对184例胶质瘤石蜡切片p53蛋白表达情况进行半定量分析.结果 86例WHO Ⅱ级少突胶质细胞瘤石蜡标本染色体1p缺失率为69.8%(60/86)、19q缺失率为64.0%(55/86)、1p/19q联合缺失率为57.0%(49/86);45例间变性少突胶质细胞瘤中,1p缺失率为71.1%(32/45)、19q缺失率为60.0%(27/45)、1p/19q联合缺失率为55.6%(25/45);两种级别间差异无统计学意义(P>0.05).30例WHO Ⅱ级少突胶质细胞瘤新鲜标本染色体1p缺失率为70.0%(21/30)、19q缺失率为63.3%(19/30)、1p/19q联合缺失率为60.0%(18/30),与石蜡标本的缺失率比较差异无统计学意义(P>0.05).30例星形细胞起源的肿瘤染色体对应三种缺失率分别为23.3%(7/30)、33.3%(10/30)及20.0%(6/30),与少突胶质细胞瘤差异有统计学意义(P<0.05).86例WHO Ⅱ级少突胶质细胞瘤中,仅7例有p53蛋白阳性表达(占8.1%);45例间变性少突胶质细胞瘤中,有14例呈阳性表达(31.1%),两者差异有统计学意义(P=0.007).少突胶质细胞瘤p53蛋白阳性表达明显低于星形细胞起源的肿瘤(P=0.001).在间变性少突胶质细胞瘤中,染色体1p/19q杂合性缺失与p53蛋白阳性表达呈负相关(P<0.05).结论 石蜡和新鲜组织均可用于染色体1p/19q杂合性缺失的检测.在间变性少突胶质细胞瘤中,染色体1p/19q杂合性缺失与p53蛋白阳性表达呈负相关.检测少突胶质细胞瘤染色体1p/19q杂合性缺失和p53蛋白表达,对提高病理诊断的精确性、指导治疗及预后判断具有重要意义.     

CD133 expression and cancer stem cells predict prognosis in high-grade oligodendroglial tumors

High-grade oligodendroglial tumors, that is, anaplastic oligodendroglial tumors and glioblastomas with oligodendroglial component, differ significantly in terms of prognosis and response to chemotherapy. Differentiation might be difficult because the histological differences are vague and reliable markers are not established. We correlated the presence of putative cancer stem cells (CSC) in high-grade oligodendroglial tumors (WHO grades III and IV) with clinical outcome. Tumors with favorable prognosis neither contained CSC nor did they show CD133 expression. Tumor cells resembled lineage-restricted progenitor cells with limited proliferative capacity and differentiation profile. In contrast, CD133 expression and stem cell-like tumor cells characterized tumors with poor prognosis. They showed neurosphere-like growth, differentiated into cells of all neural lineages, and were tumorigenic in nude mice. In our series, CSC and expression of CD133 predicted the clinical course of disease better than the histological grading. To confirm these results, we retrospectively analyzed 36 high-grade oligodendroglial tumors. Again, CD133 expression indicated shorter survival and predicted clinical outcome more reliable than the histological assessment. Our data show that detection of CSC and expression of CD133 is predictive of prognosis in high-grade oligodendroglial tumors. The presence or absence of CD133(+) CSC might explain the crucial biological difference between WHO grade III and IV oligodendroglial tumors.     

Prognostic impact of genetic alterations and methylation classes in meningioma

Meningiomas are classified based on histological features, but genetic and epigenetic features are emerging as relevant biomarkers for outcome prediction and may supplement histomorphological evaluation. We investigated meningioma‐relevant mutations and their correlation with DNA methylation clusters and patient survival times. Formalin‐fixed and paraffin‐embedded samples of 126 meningioma patients (WHO grade I 52/126; 41.3%; WHO grade II: 48/126; 38.1%; WHO grade III: 26/126; 20.6%) were investigated. We analyzed NF2, TRAF7, KLF4, ARID, SMO, AKT, TERT promotor, PIK3CA, and SUFU mutations using panel sequencing and correlated them to DNA methylation classes (MC) determined using 850k EPIC arrays. The TRAKL mutation genotype was characterized by the presence of any of the following mutations: TRAF7, AKT1, and KLF4. Survival data including progression‐free survival (PFS) and overall survival (OS) was retrieved from chart review. Mutations were evident in 90/126 (71.4%) specimens with mutations in NF2 (39/126; 31.0%), TRAF7 (39/126; 31.0%) and KLF4 (25/126; 19.8%) being the most frequent ones. Two or more mutations were observed in 35/126 (27.8%) specimens. While TRAKL was predominantly found in benign MC, NF2 was associated with malign MC (p < 0.05). TRAF7, KLF4, and TRAKL mutation genotype were associated with improved PFS and OS (p < 0.05). TERT promotor methylation, intermediate, and malign MC were associated with impaired PFS and OS (p < 0.05). Methylation cluster showed better prognostic discrimination for PFS and OS (c‐index 0.77/0.75) than each of the individual mutations (c‐index 0.63/0.68). In multivariate analysis correcting for age, gender, MC, and WHO grade, none of the individual mutations except TERT remained an independent significant prognostic factor for PFS. Molecular profiling including mutational analysis and DNA methylation classification may facilitate more precise prognostic assessment and identification of potential targets for personalized therapy in meningioma patients.     

Molecular pathology of ovarian carcinomas

 There is evidence that ovarian cancer may be derived from the progressive transformation of benign and/or borderline tumours. Mutations involving different oncogenes and tumour suppressor genes accumulate during the process of malignant transformation, and the alterations of genes involved in the pathogenesis of familial ovarian cancer are probably early events in ovarian tumorigenesis. BRCA-1 and BRCA-2 act as classical tumour suppressor genes in hereditary tumours, but their role in sporadic tumours remains controversial; however, a high frequency of allele losses in BRCA-1 (17q) and BRCA-2 (13q) loci has been observed in both familial and sporadic tumours. The possible role of mismatch repair genes and microsatellite instability is also controversial, but a role for them has been proposed in borderline tumours. Mutations in K-ras are specific for mucinous tumours and may be related to mucinous differentiation. Finally, a role in tumour progression has been proposed for both c-erb B-2 and p53, but their practical value in prognosis remains questionable. Received: 29 May 1997 / Accepted: 2 April 1998     

Pathology and molecular genetics of oligodendroglial tumors

Oligodendroglial gliomas are second only to astrocytic gliomas in frequency. The lack of stringent diagnostic criteria cause high interobserver variation in regard to classification and grading of these tumors. Previous studies have described oligodendrogliomas with features that overlap with those of neurocytic tumors, thus further complicating diagnostic decisions. The increasing need for standardized diagnostic criteria in this subset of gliomas is emphasized by the benefit of adjuvant therapies in patients with anaplastic oligodendrogliomas. Characteristic chromosomal aberrations have been successfully determined for oligodendroglial tumors in recent years. In contrast to astrocytomas, however, no genes in the affected regions have been clearly linked to their pathogenesis. However, the molecular findings promise to be helpful for diagnostic and therapeutic decisions. This review compiles clinical, pathological, and molecular genetic findings on WHO grades II and III oligodendrogliomas and oligoastrocytomas.     

Anaplastic oligodendroglial tumors: refining the correlation among histopathology, 1p 19q deletion and clinical outcome in Intergroup Radiation Therapy Oncology Group Trial 9402

Intergroup Radiation Therapy Oncology Group Trial 9402 study, a phase III trial of chemotherapy plus radiotherapy (PCV-plus-RT) vs. radiotherapy alone for pure and mixed anaplastic oligodendroglioma confirmed the prognostic significance of 1p 19q deletion and showed that only progression-free survival (PFS) was prolonged in PCV-plus-RT-treated patients and only in association with 1p 19q deletion. We reviewed tumor histopathology, separating 115 tumors deemed to be classic for oligodendroglioma (CFO) from 132 lacking classic features of oligodendroglioma (NCFO) and evaluated the relationship of histopathology and 1p 19q status to treatment and outcome. The study disclosed: (i) overall survival (OS) of patients with CFO was significantly longer than for patients with NCFO (P < 0.0001) and was not affected by necrosis. Median OS for CFO patients with and without necrosis was 6.6 and 6.3 years (OS log-rank P = not significant), respectively, in contrast to NCFO showing 1.9 and 3.3 years respectively (OS log-rank P = 0.014). (ii) Classic oligodendroglial morphology was highly associated with 1p 19q deletion, present in 80% of CFO and only in 13% of NCFO. (iii) On multivariate analysis, both classic oligodendroglial morphology and 1p 19q deletion remained significantly associated with PFS and OS. (iv) Patients with CFO treated with PCV-plus-RT showed a trend toward increased survival compared with CFO treated with RT (P = 0.08). Median OS was not reached in the PCV-plus-RT group and was 6.3 years in RT group. These findings suggest that classic oligodendroglial morphology combined with 1p 19q deletion may in the future be predictive of chemotherapeutic response and survival.     

Pathological assessment of pancreatic endocrine tumors for metastatic potential and clinical prognosis

The prognostic significance of several pathological factors (tumor size, mitotic index, Ki-67 labeling index, and vascular invasion) and expression of exocrine markers (CA19-9, CEA, AFP, and trypsin) in pancreatic endocrine tumors was studied. A total of 20 specimens of metastasizing (n=10) and non-metastasizing (n=10) tumors were subjected to histological and immunohistochemical examination. The metastasizing tumors showed significantly larger size, higher Ki-67 labeling index, increased number of mitotic cells, and more frequent vascular invasion in comparison with the non-metastasizing tumors. It was difficult to determine the effect of individual factors on clinical outcome because of slow disease progression in almost all cases. Numerous mitotic cells and widespread necrosis, however, were thought to indicate a poor prognosis, and tumors with these characteristics were regarded as high-grade malignant endocrine carcinomas. In one case, one-third of the tumor tissue comprised trypsin-positive cells, the outcome was comparatively poor, and the behavior of the tumor resembled that of mixed acinar-endocrine carcinoma. A simple multifactorial approach may be effective for the identification of tumors at increased risk of metastasis, but it remains difficult to determine clinical prognosis. It is essential to at least distinguish high-grade endocrine carcinomas from the more common endocrine tumors.     

Analysis of genetic alterations in renal cell carcinoma using the polymerase chain reaction

Very frequent loss of heterozygosity (LOH) on chromosome 3p has been found in human renal cell carcinoma (RCC). In the present study, we examined LOH at the retinoblastoma (RB), mutated in colorectal cancer (MCC) and adenomatous polyposis coli (APC) tumour suppressor genes loci, and mutations of the H-, K-, and N-ras oncogenes. We performed these studies using the polymerase chain reaction (PCR) method followed by restriction fragment length polymorphism (RFLP) and single-strand conformation polymorphism (SSCP) analyses. LOH was detected in 2 of 11 (18.2%), and 2 of 14 (14.3%) informative cases at the MCC and APC loci, respectively, and in none of 15 informative cases at the RB locus in 25 RCCs. LOH at the MCC was accompanied by LOH at the APC locus in two RCCs. No mutation was detected in H-, K-, and N-ras genes in 39 RCCs. Thus, alterations of the known tumour suppressor genes and the ras oncogenes were infrequent events in RCC. The results suggest that the genetic pathway in the genesis of RCC differs considerably from that of other common human carcinomas.     

Detection of genetic alterations in bladder tumors by comparative genomic hybridization and cytogenetic analysis

Comparative genomic hybridization (CGH) and conventional cytogenetic karyotyping were used to screen for losses and gains of DNA sequences along all chromosome arms in 16 bladder tumors. Cytogenetic results were highly complex. The most frequently affected chromosomes were 5, 8, 9, 21, and Y as determined by karyotyping. There was close correlation between the CGH data and cytogenetic results in near-diploid tumors with simple karyotypes. However, some unexpected results were observed by CGH in tumors with several composite clones. Common amplification of copy numbers of DNA sequences by CGH were seen at 1q, 3q, 4q, 5p, 6p/q, 7p, 8q, 11q, 12q, 13q, 17q, 18q, and 20p/q (more than 20% of cases). High level amplification was noted at 1p32, 3p21, 3q24, 4q26, 8q21-qter, 11q1422, 12q1521, 12q2124, 13q2131, 17q22, and 18q22. Deletions were noted at 2q21qter, 4q1323, 5q, 8p1222, 9p/q, and 11p1315 (more than 20% of cases). Although most amplifications and deletions have been previously described in the literature, our study showed some intriguing and uncommon regions, different from those found in past studies. These were the amplification of 7p, 8q, 11q14qter 12q2424, 13q2131, and 18q22, and deletion on 4q1323, even though loss of heterozygosity was not detected at this locus. In spite of the very complex pattern of genetic changes in bladder tumors, most of these uncommon aberrations have to be implicated in bladder tumors, and further molecular genetic methods are necessary to establish whether the chromosomal regions contain candidate genes which contributed to the initiation and progression of bladder tumors.     

A meta-analysis of nonsense mutations causing human genetic disease

Nonsense mutations account for approximately 11% of all described gene lesions causing human inherited disease and approximately 20% of disease-associated single-basepair substitutions affecting gene coding regions. Pathological nonsense mutations resulting in TGA (38.5%), TAG (40.4%), and TAA (21.1%) occur in different proportions to naturally occurring stop codons. Of the 23 different nucleotide substitutions giving rise to nonsense mutations, the most frequent are CGA --> TGA (21%; resulting from methylation-mediated deamination) and CAG --> TAG (19%). The differing nonsense mutation frequencies are largely explicable in terms of variable nucleotide substitution rates such that it is unnecessary to invoke differential translational termination efficiency or differential codon usage. Some genes are characterized by numerous nonsense mutations but relatively few if any missense mutations (e.g., CHM) whereas other genes exhibit many missense mutations but few if any nonsense mutations (e.g., PSEN1). Genes in the latter category have a tendency to encode proteins characterized by multimer formation. Consistent with the operation of a clinical selection bias, genes exhibiting an excess of nonsense mutations are also likely to display an excess of frameshift mutations. Tumor suppressor (TS) genes exhibit a disproportionate number of nonsense mutations while most mutations in oncogenes are missense. A total of 12% of somatic nonsense mutations in TS genes were found to occur recurrently in the hypermutable CpG dinucleotide. In a comparison of somatic and germline mutational spectra for 17 TS genes, approximately 43% of somatic nonsense mutations had counterparts in the germline (rising to 98% for CpG mutations). Finally, the proportion of disease-causing nonsense mutations predicted to elicit nonsense-mediated mRNA decay (NMD) is significantly higher (P=1.56 x 10(-9)) than among nonobserved (potential) nonsense mutations, implying that nonsense mutations that elicit NMD are more likely to come to clinical attention.