G-显带技术、荧光原位杂交和比较基因组杂交技术在产前诊断中的应用

目的 探讨G显带、荧光原位杂交(fluorescencein situ hybridization,FISH)和比较基因组杂交(comparative genomic hybridization,CGH)技术在产前诊断中应用的程序及意义.方法 采集102例妊娠16周～24周胎儿的羊水,采用G显带、G显带/FISH和G显带/FISH/CGH三阶梯的核型诊断程序,并分析其在产前诊断中的意义.结果 102例胎儿中,经第1阶梯诊断核型98例,诊断困难2例,失败2例;第2阶梯诊断核型2例,诊断困难1例,失败1例;第3阶梯诊断核型2例.经3阶梯诊断程序核型的诊断率达100%(102/102例),异常核型7例(7/102例,6.68 0A),其中第1、第2和第3阶梯分别诊断异常核型4例(4/7例,57.1 oA)、1例(1/7例,14.3%)和2例(2/7例,28.5%).结论 在产前诊断中实施3阶梯诊断程序有助于提高核型的确诊率,规范染色体诊断流程.     

A de novo supernumerary genomic discontinuous ring chromosome 21 in a child with mild intellectual disability

Small supernumerary marker chromosomes (sSMCs) are structurally abnormal extra chromosomes that cannot be unambiguously identified or characterized by conventional banding techniques alone, and they are generally equal in size or smaller than chromosome 20 of the same metaphase spread. Small supernumerary ring chromosomes (sSRCs), a smaller class of marker chromosomes, comprise about 10% of the cases. For various reasons these marker chromosomes have been the most difficult to characterize; although specific syndromes have not yet been defined, 60% of cases are associated with an abnormal phenotype. The chromosomal material involved, the degree and tissutal distribution of mosaicism, and the possible presence of uniparental disomy, are the important factors determining whether or not the ring chromosome will give rise to symptoms. Using conventional and molecular cytogenetics approaches we identified a de novo chromosome 21 sSRC in a child with speech delay and mild intellectual disability. By using aCGH analysis and SNP arrays, we report the presence of two discontinuous regions of chromosome 21 and the paternal origin of the sSRC. A thorough neuropsychiatric evaluation is also provided. Only few other cases of complex discontinuous ring chromosomes have been described in detail.     

髓母细胞瘤比较基因组杂交分析及ERBB-2异常表达的意义

目的研究髓母细胞瘤全基因组的遗传学异常,探讨癌基因的异常表达在髓母细胞瘤发病机制中的作用以及与预后的关系。方法应用比较基因组杂交（comparative genomic hybridization,CGH）技术检测14例髓母细胞瘤全基因组的遗传学改变;同时,在扩大系列的29例髓母细胞瘤中,应用荧光原位杂交（fluorescence in situ hybridization,FISH）和免疫组化染色分别检测ERBB-2在基因水平和蛋白水平的表达。结果（1）CGH结果显示,在所有14例髓母细胞瘤标本中,每一条染色体臂上都检测到了染色体的失衡（获得或丢失）,最常见的染色体异常为17q（85．7％）和7q（35．7％）的获得,以及8p（50％）、16q（28．6％）和17p（35．7％）的丢失;（2）FISH检测中,44．5％（13／29例）的肿瘤细胞有ERBB-2基因的异常表达;（3）免疫组化结果显示,37．9％（11／29例）的病例有抗体c-erbB-2的阳性表达;（4）在预后较差的16例患者中,56％（9／16例）的病例有ERBB-2的过度表达。结论CGH研究发现了髓母细胞瘤全基因组的染色体失衡。在染色体17q特异性位点上ERBB-2基因的异常改变很可能在髓母细胞瘤的发病机制中起着重要的作用,其过度表达与患者的预后密切相关。     

Comparative genomic hybridization in a case of melanoma that loses expression of S100, HMB45, Melan A and tyrosinase in metastasis

We recently reported three cases of metastatic melanoma that does not express S100, HMB45, Melan A and Tyrosinase. A concurrent cutaneous scalp primary melanoma was identified later in one of the cases, which showed strong expression of these markers. The difference in immunophenotype between the primary melanoma and its metastasis in the parotid gland in this case raised the question of the biological significance of the expression of these markers and metastatic potential. To address this question, we utilized microarray comparative genomic hybridization (aCGH) to compare the cytogenetic features between the primary and metastatic melanoma. We observed chromosomal gains including 6p, entire chromosome 7, and 8q11.1-q24.3 in both primary and metastatic tumors. However, the metastatic lesion showed unique additional copy of chromosomal 7q, and loss of chromosome 9p24.3-q13 and chromosome 4, which included Melan A encoding gene region in 9p24.1. The above findings suggest the unique cytogenetic changes in the parotid lesion are most likely related to the metastatic behavior, as well as responsible for loss of multiple melanocytic marker expression in the metastatic melanoma for this case.     

鼻咽癌的比较基因组杂交研究

目的：研究鼻咽癌的遗传变异特性。方法：采用激光微切割技术分离鼻咽癌细胞DNA，用比较基因组杂交检测6例鼻咽癌组织。结果：6q12-22、8q染色体区域的扩增，染色体11q23-24、13q基因缺失。结论：鼻咽癌具有染色体变异，其中6q12-22、8q、11q23-24和13q区域可能存在一些与鼻咽癌相关的未知基因。     

Fluorescence in situ hybridization, comparative genomic hybridization, and other molecular biology techniques in the analysis of effusions

Over the last 20 yr, the introduction of immunocytochemistry as a diagnostic tool has dramatically revolutionized diagnostic pathology. With the introduction of molecular methods as part of the diagnostic armamentarium, the practicing pathologist is facing the new challenge of grasping novel concepts of the molecular cytogenetics era. Herein, we review the diagnostic contribution of ancillary molecular techniques, including fluorescent and chromogenic in situ hybridization, telomerase assays, loss of heterozygosity, comparative genomic hybridization (CGH), and microarray-based CGH, for the practicing cytopathologists and discuss how these techniques will help pathologists in decision-making.     

Molecular cytogenetics: recent developments and applications in cancer

Aneuploidy or alteration in chromosome numbers is a characteristic feature in cancer that is generally a consequence of defective chromosome segregation during cell division. Molecular cytogenetic analyses have conferred substantial evidence with regards to the chromosomal architectures in cancer. Most importantly, the fluorescence in situ hybridization (FISH) technique that plays a leading role in diagnostic pathology for its single‐cell analysis has provided crucial information regarding genomic variations in malignant cells. Further development of molecular cytogenetic methodologies such as chromosome specific FISH karyotyping and comparative genomic hybridization have also helped in the detection of cryptic genetic changes in cancer. But, the recent advancement of high throughput sequencing technologies have provided a more comprehensive genomic analyses resulting in novel chromosome rearrangements, somatic mutations as well as identification of fusion genes leading to new therapeutic targets. This review highlights the application of early molecular cytogenetics and the recent high throughput genomic approaches in characterizing various cancers and their invaluable support in cancer therapeutics.     

Optimization of the fluorescence in situ hybridization (FISH) technique for high detection efficiency of very small proportions of target interphase nuclei

Using commercially available fluorochrome-labeled probes specific for chromosomes X, Y, 13, 18, and 21, we optimized the technical protocols for fluorescence in situ hybridization (FISH) so that the highest sensitivity and specificity were achieved. Also, we compared the optical properties of different types of fluorescent labels in an effort to develop the most efficient FISH protocol, including the determination of which types of labels are the easiest to count accurately. The lymphocytes were purified from blood of normal male and female newborns, normal male and female adults, and a trisomy 21 male adult. Male and female lymphocytes were mixed in five different combinations. For each combination, the male lymphocytes either from newborns or from adults were diluted with female lymphocytes in seven different proportions. For each of these 35 different cell mixtures, 100,000 nuclei were analyzed and scored in a blind fashion. Among the different fluorochrome-labeled probes, the highest sensitivity and specificity were achieved when SpectrumAqua CEP-Y/SpectrumOrange CEP X probe mixture, SpectrumAqua CEP-18, SpectrumOrange LSI-13, and SpectrumOrange LSI-21 were hybridized. The hybridization sensitivity and specificity were higher than 99% for the identification of chromosomes X, Y, 13, and 18, and higher than 98% for the detection of trisomy 21. The proportion of false-positive signals was under 0.005% for XY detection and lower than 0.14% for autosome detection. With these high hybridization sensitivities and specificities, the optimized FISH protocol developed in our laboratory has the potential to detect very rare events, e.g., when the proportion of cells being sought is lower than 0.01%. In other words, our protocol allows the specific detection of one male cell sunken among 10,000 female cells.     

A cytogeneticist's perspective on genomic microarrays

The identification of cytogenetic imbalance is an important component of clinical genetics. About 1 in 154 newborns has a chromosome abnormality. Conventional cytogenetic analysis has enabled the identification of microscopic alterations of the chromosomes. The development of fluorescence in situ hybridization (FISH) and other molecular methodologies has made possible the identification of submicroscopic aberrations. An additional development was comparative genomic hybridization (CGH), a method that directly compares two genomes for DNA copy differences. As first developed, the substrate for CGH analysis is normal metaphase chromosomes. Recently, CGH has been applied to microarrays (array CGH) constructed from large insert clones to identify chromosome imbalance. Array CGH has many advantages over conventional cytogenetic and molecular cytogenetic techniques. Array CGH can be comprehensive (genome-wide), high resolution, amenable to automation, rapid, and sensitive. We anticipate that array CGH will be employed in the clinical cytogenetics laboratory in the near future and will lead to the identification of the chromosomal basis of new syndromes and existing genetic conditions.     

Array-based comparative genomic hybridization of ductal carcinoma in situ and synchronous invasive lobular cancer

It has been increasingly recognized that ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS) and invasive cancer of the breast are often closely associated with one another. However, the genomic relationship between these histologically distinct entities has not been well characterized. Refinements in high-resolution comparative genomic hybridization (CGH) techniques allow for a detailed comparison of genomic alterations in synchronously occurring tumors. The following case illustrates how array CGH may be used to better understand whether synchronous neoplasms share a common origin.     

荧光原位杂交联合微阵列比较基因组杂交分析一例原发性闭经患者的染色体畸变

目的分析1例原发性闭经患者的染色体畸变,探讨该患者原发性闭经的可能原因。方法采集临床已确诊的原发性闭经患者外周血,并抽提基因组DNA,进行荧光原位杂交和微阵列比较基因组杂交,分析染色体异常。结果微阵列比较基因组杂交显示患者染色体Xp22.31区域存在长1.637Mb片段的三倍体,Xp21.2-q21.1区域存在长52.156 Mb片段的重复片段。结论微阵列比较基因组杂交技术可以检测染色体微小畸变,值得临床推广应用。     

Interphase cytogenetics of gastric carcinoma: Fluorescence in situ hybridization (FISH) applied to cells obtained from formalin-fixed paraffin-embedded tissues

The interphase cytogenetics in formalin-fixed and paraffin-embedded gastric cancer tissues were examined by fluorescence in sku hybridization (FISH) with α-satellite DNA probes. Two gastric carcinoma cell lines, TMK-1 and MKN-28, were first analyzed cytogenetically. Of 25 TMK-1 cell karyotypes, chromosome 7 showed trisomy and chromosome 17 showed disomy in 18 cells. Most MKN-28 cells showed disomy of both chromosomes 7 and 17. Suspensions of singly isolated TMK-1 and MKN-7 cells were obtained from the cultured cells, and from paraffinembedded tissue specimens fixed with formalin for 0, 1, 3 and 5 days obtained from xenotrans-planted tumors in nude mice. The numbers of chromosomes 7 and 17 analyzed with the karyotypic preparations coincided well with those determined by FISH, even in the paraffin-embedded specimens. The number of tumor cells showing no signals, however, increased in the specimens after 5 days formalin fixation. In 10 surgically removed gastric carcinomas, the predominant signal number for chromosomes 7 and 17 in the cells of paraffinembedded tissues was two (disomy), except in one papillary carcinoma, which was trisomic for chromosome 7. Large subpopulations (more than 20%) showing trisomy were found in four cases for chromosome 7 and in five cases for chromosome 17. A higher frequency of trisomy was found in well differentiated than in poorly differentiated carcinomas. These findings suggest that the FISH technique is a useful tool for detecting chromosomal aberrations in gastric adenocarcinoma cells, even in paraffinembedded specimens, as long as the tissues are fixed with formalin for an appropriate time.     

Common genetic changes in leiomyosarcoma and gastrointestinal stromal tumour: implication for ataxia telangiectasia mutated involvement

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the gastrointestinal tract. Formerly GISTs were commonly classified histologically as leiomyosarcomas; however, they are now known to arise from the interstitial cells of Cajal. Majority of GISTs overexpress KIT and have characteristic mutations within the gene, which are the targets of drug treatment with tyrosine kinase inhibitors. Leiomyosarcoma is a malignant tumour of smooth muscle differentiation and falls into a group of sarcomas that show complex karyotypic changes with no consistent recurrent genetic abnormality. We have used comparative genomic hybridization in combination with fluorescence in situ hybridization to determine genetic differences between the tumour types. We found leiomyosarcomas and GISTs share common regions of chromosomal 13q and 11q imbalance, in addition to more specific 1p and 8p losses in leiomyosarcoma and 15q and 22q losses in GISTs. More importantly, we have shown for the first time a deletion in the ataxia telangiectasia mutated (ATM) gene locus with decreased/absent expression of ATM protein, and amplification in the region 13q21–q32 in both tumour types, suggesting both regions may play a role in leiomyosarcoma and GIST biology.     

Chromogenic in situ hybridization (CISH) to detect HER2 gene amplification in breast and gastric cancer: Comparison with immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH)

The chromogenic in situ hybridization (CISH) assay, designed to detect the amplification of the HER2 gene in formalin‐fixed, paraffin‐embedded (FFPE) breast cancer (BC) and gastric cancer (GC) tissue specimens, was evaluated in 125 FFPE BC cases and 198 FFPE GC cases for which the HER2 status had been predetermined using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). In the 125 BC cases and the 198 gastric cases, we found a very good concordance (98.4% and 99.0%, respectively) between CISH and FISH. In particular, we evaluated the polysomy cases, as these cases often have ambiguous treatment options in clinical practice. The polysomy of chromosome 17 was defined as the presence of three or more CEP17 signals in at least 10% of the tumor cells. In the 50 BC cases and 54 GC cases displaying chromosome 17 polysomy, the concordance between FISH and CISH was 98.0% and 98.1%, respectively. These results indicate that CISH could provide an accurate and practical alternative to FISH for the clinical diagnosis of HER2 gene amplification in FFPE BC and FFPE GC samples.     

用比较基因组杂交技术(CGH)检测肾癌染色体畸变

目的应用比较基因组杂交技术(CGH)分析原发性肾癌肿瘤组织中染色体异常变化,探讨肾癌细胞遗传物质的改变,揭示肾癌发生发展的内在本质及其与临床特征之间的关系。方法采用CGH技术对12例肾癌组织提取的全基因组DNA进行检测,以了解肾癌全基因组的变化。结果CGH技术检测的12例肾癌标本中均有染色体的畸变(扩增和/或缺失),常见的扩增区是1p、4p、5q、7p、9p、16p,常见的缺失区是3q、4q、6q、9q、14q、18q。结论原发性肾癌存在广泛的遗传物质不平衡现象,肾癌细胞染色体扩增和/或缺失可能是肾癌发生发展的基础。     

荧光原位杂交技术在泌尿系统非尿路上皮肿瘤的研究进展

作为一种新技术,荧光原位杂交技术在泌尿系统非尿路上皮肿瘤中得到广泛应用并取得了一些成果:肾上腺肿瘤的良恶性鉴别;肾肿瘤的病理分型,转移预后;肾母细胞瘤的发病机理;VHL综合症的基因诊断;前列腺癌的发病机理和治疗预后;睾丸癌等其他肿瘤的基因诊断等。     

Detection of a human chromosomal translocation t(8;9) in a baby with multiple malformations using two-color fluorescence in situ hybridization

A human chromosomal translocation t(8;9) was detected using two-color fluorescence in situ hybridization with probes capable of staining the entire lengths of each of these chromosomes. The chromosome 8 probe was labeled with biotin and detected with Texas red, while the chromosome 9 probe was labeled with AAF and detected with FITC . In normal metaphase spreads, two metaphases from the proband, two red, one green and one part red and part green derivative chromosome were seen. The bicolor chromosome corresponded to translocation of a chromosome 8 segment to the distal part of the q region of one chromosome 9, as originally indicated by banding analysis. In interphase nuclei of the proband, four domains with bright fluorescence were recognized in many nuclei. Two were red, one was green, and the fourth had portions of both colors, indicating the presence of the translocation.     

TP53 mutations are associated with a particular pattern of genomic imbalances in breast carcinomas

TP53 mutations play an important role in the development of several cancers and are present in 20-40% of all breast carcinomas, contributing to increased genomic instability. In order to address the relationship of mutated TP53 to genomic complexity, the present study analysed 61 breast carcinomas for TP53 mutations and compared mutation status with the pattern of genomic imbalances as assessed by comparative genomic hybridization (CGH). Twenty per cent of the present series of breast carcinomas harboured TP53 mutations. An increasing number of abnormalities, as identified by CGH (higher genomic complexity), correlated significantly with mutant TP53. Among the chromosome arms most commonly altered (in more than 20% of the tumours), loss of 8p and gain of 8q were associated with TP53 mutations, whereas loss of 16q was associated with wild-type TP53. By performing supervised hierarchical clustering analysis of the CGH data, a cluster of chromosome imbalances was observed that showed differences between wild-type and mutant TP53 cases. Among these, loss of chromosome arm 5q revealed the strongest correlation with altered TP53. To investigate further the most commonly deleted region of 5q, gene expression patterns from two publicly available microarray data sets of breast carcinomas were evaluated statistically. The expression data sets identified potential target genes, including genes involved in ubiquitination and the known TP53 target CSPG2. The genomic complexity of breast carcinomas as assessed by CGH is associated with TP53 mutation status; breast cancers with TP53 mutations display more complex genomes than do those with wild-type TP53. The pattern of genomic imbalances associated with mutant TP53 is non-random, with loss of chromosome arm 5q being particularly closely associated with TP53 mutations.     

Evaluation of HER2 gene amplification in invasive breast cancer using a dual‐color chromogenic in situ hybridization (dual CISH)

Fluorescence in situ hybridization (FISH) assay is considered the ‘gold standard’ for evaluation of HER2/neu (HER2) gene status, however, it is difficult to recognize morphologic features of tumors using fluorescence microscopy. Thus, chromogenic in situ hybridization (CISH) has been proposed as an alternative method to evaluate HER2 gene amplification. Here, we examined the dual color CISH (dual CISH) method which provides information regarding the copy number of the HER2 gene and chromosome 17 centromere from a single slide. We examined 40 cases of invasive ductal carcinomas of the breast that were resected surgically. HER2 gene status was assessed with FISH (Abbott) and dual CISH (Dako). HER2 gene amplification status was classified according to the guidelines of the American Society of Clinical Oncology and College of American Pathologists (ASCO/CAP). Comparison of the cut‐off values for HER2/chromosome 17 centromere copy number ratio obtained by dual CISH and FISH showed that there was almost perfect agreement between two methods (Kappa coefficient 0.96). The results of the two commercial products were almost consistent for evaluation of HER2 gene counts on the sections. The current study proved that dual CISH is comparable with FISH for evaluating HER2 gene status.     

Chromosomal integrity maintained in five human embryonic stem cell lines after prolonged in vitro culture

There have been recent reports of human embryonic stem cell (hESC) lines developing chromosomal aberrations after long-term culture, indicating an unstable genomic status due to the in vitro milieu. This raises concern, since it would limit their use in therapeutics. In this study the chromosomal status of five well-characterized hESC lines, SA002, SA002.5, AS034.1.1, SA121 and SA461, was monitored during long-term in vitro culture. The criteria of defined hESCs were met by all of the five hESC lines (four diploid and one trisomic for chromosome 13). The genomes were screened for chromosomal aberrations and rearrangements using comparative genomic hybridization (CGH), interphase fluorescence in situ hybridization (FISH) and traditional karyotyping on several occasions while in culture. The genomic integrity was shown to be maintained after repeated freeze-thaw procedures and continuous culture in vitro for up to 22 months (148 passages). We discuss the most common de novo chromosomal aberrations reported in hESCs, as well as their possible origin.