Intragenic allelic loss and promoter hypermethylation of the RIZ1 tumor suppressor gene in parathyroid tumors and pheochromocytomas

BACKGROUND: Loss of heterozygosity (LOH) at chromosome 1p is a common abnormality in both parathyroid tumors and pheochromocytomas. The recently characterized tumor suppressor gene RIZ1, located at 1p36, has emerged as a putative candidate to be involved in endocrine tumorigenesis. MATERIAL: Presence of allelic loss, promoter hypermethylation, and mutational aberrations of the RIZ1 gene were investigated using PCR-based techniques in 47 parathyroid tumors and 23 pheochromocytomas. Gene expression studies used the RNAse protection assay. RESULTS: RIZ1 mRNA is expressed in pathologic tissues of the parathyroid and adrenal medulla. Thirteen of 47 (28%) parathyroid tumors, and 9/23 (39%) pheochromocytomas displayed LOH within the RIZ1 gene locus. Promoter hypermethylation of RIZ1 was detected in 36% of the parathyroid tumors and was related to LOH at the RIZ1 locus (P=.01), and absence of somatic mutation of the MEN1 gene (P=.044). In the pheochromocytomas, none of the benign tumors, but 2/4 malignant specimens exhibited RIZ1 promoter hypermethylation. CONCLUSION: Alteration of the RIZ1 gene locus via intragenic allelic loss and promoter hypermethylation seem common in parathyroid tumors. Inactivation of the RIZ1 gene may cause parathyroid tumorigenesis via a mechanism in which genetic alteration of the MEN1 gene is redundant.     

Molecular and clinicopathologic comparisons of head and neck squamous carcinoma variants: common and distinctive features of biological significance

To investigate, for the first time, the events associated with the phenotypic and clinical diversities of head and neck squamous carcinomas (HNSC), we performed molecular analyses on 92 primary tumors representing the entire spectrum of the morphologic subtypes using microsatellite markers at chromosome 3p, 4p, 8p, 9p, 11q, 17p, and 18q regions and correlated the results with the clinicopathologic features and patients' survival. Loss of heterozygosity (LOH) at D9S168 and D9S171 markers on chromosome 9p regions was commonly identified in all subtypes. Distinctive alterations in certain subtypes were noted at chromosomes 3p, 4p, 8p, and 11p regions. In general, less aggressive types (verrucous, papillary, and well-differentiated conventional) had a significantly lower LOH incidence than the more aggressive (basaloid, sarcomatoid, and high-grade conventional squamous carcinoma) categories. Significant association between LOH and age, stage, nodal status, and patient outcome was found. Survival analysis revealed that pathologic categorization (less versus more aggressive) and LOH at marker D11S4167 and D3S2432 are independent predictors of patients' survival. Our analysis also defined a set of limited markers that account for most of alterations within and across these tumor subtypes. Our study indicates that 1) certain genetic markers are common to all subtypes of HNSC supporting their early involvement in tumorigenesis, 2) inter- and intratumoral genetic differences evolve subsequently and may underlie their morphologic heterogeneity, 3) high incidence of LOH in certain regions characterizes aggressive tumors, 4) categorical classification and LOH at 11p and 3p regions independently correlated with patient survival, and 5) a limited set of markers identify the majority of genetic alterations in these tumors.     

Identification of a novel microsatellite marker tightly linked to the KAI-1 gene for predicting prostate cancer progression

BACKGROUND: We have mapped the human prostate-specific membrane antigen (PSM) gene to the chromosome 11p11.2 region at 62.5 cM, a region which also contains the prostatic cancer metastasis suppressor gene KAI-1. The genetic marker D11S1344 has been utilised for loss of heterozygosity (LOH) studies on the KAI-1 gene in a large series of prostate cancer specimens. The results were negative and it was concluded that deletions of the KAI-1 gene were not involved in the development of the metastatic phenotype in these tumours. One possible explanation for this result could be that D11S1344 is not sufficiently tightly linked to the KAI-1 gene to detect small deletions. OBJECTIVE: To attempt to identify a genetic marker more tightly linked to the KAI-1 gene than D11S1344. METHODS: Yeast artificial chromosome (YAC) clones containing the KAI-1 gene and the neighbouring marker D11S1344 were analysed by the fluorescent in situ hybridisation technique. The human genomic inserts in these novel clones were sized by pulsed field gel electrophoresis. For more accurate mapping of the KAI-1 gene, YACs containing it were screened for polymorphic markers (including D11S1344) from the 11p11.2 region. RESULTS: The novel YAC clones localised exclusively to the 11p11.2 region, with single hybridisation signals compared to the dual signals consistently obtained with nearby PSM-containing YACs. All the KAI-1 clones found had small inserts (<300 kb). The only known microsatellite which gave amplification products with these YACs was D11S986 which has been mapped at 61.3 cM on human chromosome 11. CONCLUSIONS: We have precisely localised KAI-1 at 61.3 cM on human chromosome 11. This is some 1.2 cM away from the previously utilised LOH microsatellite marker, D11S1344. We suggest that the very tightly linked microsatellite D11S986 may be a more accurate marker to assess LOH of the KAI-1 gene and thus predict progression of prostate cancer. The region of genetic duplication around the PSM gene does not extend as far distally on 11p as KAI-1.     

Loss of heterozygosity analysis identifies genetic abnormalities in mycosis fungoides and specific loci associated with disease progression

Mycosis fungoides (MF) exhibits a variety of underlying molecular defects. Loss of heterozygosity (LOH) is a technique used to detect chromosomal imbalances in neoplastic disorders using archival tissue. We analyzed skin biopsies of MF in different stages for the presence of LOH at specific loci to evaluate underlying genetic aberrations involved in MF and its progression. Twenty-five skin biopsies (15 plaque stage and 10 tumor stage) from 19 patients were evaluated. LOH was examined at 1p22 (D1S2766), 9p21 [IFNA, p15 (D9S1748), p16 (D9S171)], 10q23 [PTEN (D10S185, D10S541, D10S2491)], and 17p13 [p53 (TP53)]. Abnormal lymphocytes were microdissected from formalin-fixed, paraffin-embedded tissue sections. Sixteen of the 25 (64%) specimens evaluated had at least one abnormal LOH locus and LOH was identified in 7 of 15 (47%) plaque and in 9 of 10 (90%) tumor stage lesions, respectively. All 3 patients with sequential biopsies (plaque followed by tumor lesions) had additional LOH abnormalities in tumor specimens compared with plaque stage lesions. LOH most frequently involved chromosome 10, including 7 of 10 (70%) tumor stage lesions. Loss of multiple alleles was only identified in tumor stage cases, with 3 tumors undergoing allelic losses at 3 separate loci. Our results suggest that LOH studies are a robust method for evaluating genetic abnormalities in MF. Tumor stage lesions manifest increasing allelic losses compared with plaque stage. Further, in this series, several loci associated with the tumor suppressor gene PTEN on chromosome 10 appear to be associated with progression from plaque to tumor stage.     

Comprehensive loss of heterozygosity analysis and identification of a novel hotspot at 3p21 in salivary gland neoplasms.

OBJECTIVES: We sought to assess loss of heterozygosity (LOH) profiles of 3p, 6q, 8q, 10q, 12q, 13q, and 17p and to identify the tumor suppressor genes involved in salivary gland neoplasms. STUDY DESIGN: LOH analysis was performed using 26 microsatellite markers by polymerase chain reaction-polyacrylamide gel electrophoresis method in 20 benign and 6 malignant salivary gland tumors. RESULTS: Overall, LOH was detected in at least one informative locus in 18 of 20 (90%) of benign tumors and in all of 6 cases of malignant tumors. High LOH frequencies were revealed at the loci D3S1307 (22%, 3p26), D3S966 (41%, 3p21), D6S255 (27%, 6q25), D8S166 (25%, 8q12), D8S199 (21%, 8q24), and D10S1765 (28%, 10q23) in benign tumors, defining the hotspot regions for putative tumor suppressor genes. CONCLUSIONS AND SIGNIFICANCE: The hotspot regions defined by the present study suggest that new tumor suppressor genes related to the development of salivary gland tumors may reside at several chromosomal loci, including loci at 3p, 6q, 8q and 10q.     

散发性结直肠癌患者18号染色体高频杂合缺失的研究

目的：探讨散发性结直肠癌患者18号染色体上抑癌基因相关的杂合缺失（LOH）情况，并探索新的抑癌基因位点。方法：对83例散发性结直肠癌患者基因组DNA用14个不同荧光标记的高度多态性微卫生引物，扩增相应的微卫星位点，平均距离为10厘摩（centi-morgan,cM）。用ABI PRISM377测序仪进行基因扫描，统计各位点杂合缺失率。结果：在12个获得有效数据的微卫星位点中，平均杂合缺失率为36．78％,18p中最高为D18S53（38．09％），18q中最高为D18S474（55．74％）。4位患者的18号染色体所有杂合位点都存在缺失，30位患者的杂合缺失位点不少于50％（平均6个／人）；缺失位点少于50％的有53人（平均1个／人）。结论：结直肠癌患者18号染色体存在高频的LOH，并以整体缺失为特点。存在高频LOH的区域定位有转化生长因子（TGF）信号传导相关基因、结直肠癌缺失基因（DCC）、Rb结合蛋白8(RbBP8），特别是TGF信号传导相关基因MADH2、4、转化生长因子－β1反应元件（TGF－β1）等的缺失可能对结直肠癌的发生有重要影响。18p也有存在未知抑癌基因的可能。     

散发性胆管癌患者染色体3p21.3区段微卫星位点不稳定性分析

目的研究散发性胆管癌患者染色体3p21．3区段的微卫星不稳定性（MSI）及杂合性缺失（LOH），探讨染色体3p21．3区段遗传不稳定性与散发性胆管癌发生发展的关系，定位该区段上散发性胆管癌相关肿瘤基因。方法用聚合酶链反应一单链构象多态性分析（PCR—SSCP）方法检测24例散发性胆管癌患者染色体3p21．3区段上D3S1568、D3S1621、D3S1578和D3S1289四个微卫星位点的MSI和LOH发生率，分析其与临床病理因素之间的关系。结果24例散发性胆管癌组织中，4个微卫星位点的MSI和LOH平均发生率分别为7．23％和15．63％。其中D3S1621位点的LOH最高（45．83％，11／24），并与TNM分期、是否伴有局部／淋巴结转移相关（P〈0．05）。结论染色体3p21．3区段133S1621位点高频率杂合性缺失，提示3p21．3区段定位有散发性胆管癌的候选抑癌基因，并在散发性胆管癌的发生发展过程中发挥重要作用。     

Chromosome 22q a frequent site of allele loss in head and neck carcinoma

BACKGROUND: Loss of heterozygosity (LOH) correlates with inactivated tumor suppressor genes. LOH at chromosome arm 22q has been found in a variety of human neoplasms, suggesting that this region contains a tumor suppressor gene(s) other than NF2 important to tumorigenesis. The aim of this study was to evaluate the presence of LOH on chromosome 22q11.2-13 and determine whether there was a relationship between loss in this genomic region and tumor histologic parameters, anatomic site, and survival in patients with squamous cell carcinoma of the head and neck (HNSCC). METHODS: Fifty matched blood and HNSCC tumor samples taken at the time of surgical treatment were evaluated for LOH by use of four microsatellite markers mapping to 22q11.2-q13. Clinical information was available for all patients. The frequency and distribution of LOH was correlated with clinical (age, sex, use of tobacco and alcohol, site of primary tumor, clinical stage, adjuvant therapy and overall survival) and histologic parameters (histopathologic stage, tumor differentiation). RESULTS: LOH at 22q was found in 19 of 50 (38%) informative tumors. The respective incidence of allelic loss for the patients was as follows: 28% at D22S421, 10% at D22S277, 8% at D22S446, and 4% at D22S280. No statistical differences were apparent with a mean follow-up of 30 months. Laryngeal tumors showed a higher incidence of LOH compared with oral tumors. CONCLUSIONS: These results suggest that the D22S277 locus may be closely linked to a tumor suppressor gene (TSG) and involved in upper aerodigestive tract carcinogenesis. In particular, laryngeal tumors may harbor another putative TSG on 22q11.2-q12.3 that may play a role in aggressive stage III/IV disease.     

应用激光捕获显微切割技术对肝细胞癌8号染色体短臂杂合性缺失的研究

目的探讨8p杂合性缺失（LOH）的特点及其与肝细胞癌（HCC）临床病理特征的相关性。方法选择8p上5个具有高度多态性的微卫星标记，对62例HCC组织利用激光捕获显微切割（LCM）技术进行LOH分析。结果有56．5％（35／62）的HCC患者在1个或多个基因位点发生LOH。LOH频率最高的3个位点依次为D8S298（51．1％，24／47）、D8S1771（48．8％，21／43）和D8S264（43．5％，20／46）。D8S298位点肝内转移者的LOH频率明显高于无转移者（P〈0．05）；在D8S1771位点，肿瘤直径〉3cm的LOH频率明显高于≤3cm组（P〈0．05）。结论HCC在染色体8p特定位点上LOH明显，在这些区域可能存在一个或多个与HCC发生发展相关的肿瘤抑制基因。8p上部分位点的LOH与临床病理特征有一定的相关性。     

Analysis of loss of heterozygosity on chromosome 10 in patients with malignant astrocytic tumors: correlation with patient age and survival

OBJECT: The most frequent genetic abnormality in human malignant gliomas is loss of heterozygosity (LOH) on chromosome 10. Candidate genes on chromosome 10 that are associated with the prognosis of patients with anaplastic astrocytoma (AA) and glioblastoma (GBM) were evaluated. METHODS: The authors used 12 fluorescent microsatellite markers on both arms of chromosome 10 to study LOH in 108 primary astrocytic tumors. The LOH on chromosome 10 was observed in 11 (32%) of 34 AAs and 34 (56%) of 61 GBMs. No LOH was detected in 13 low-grade gliomas. Loss of heterozygosity was not detected in any AA in the seven patients younger than 35 years, but it was discovered in 41% of the patients older than 35 years. The prognostic significance of LOH at each locus was evaluated in 89 patients older than 15 years; 33 (37%) had supratentorial AAs and 56 (63%) had supratentorial GBMs. The Cox proportional hazards model, adjusted for patient age at surgery, the preoperative Karnofsky Performance Scale score, and the extent of surgical resection revealed that LOH on marker D10S209 near the FGFR2 and DMBT1 genes was significantly associated with shorter survival in patients with AA. The LOH on markers D10S215 and D10S541, which contain the PTEN/MMAC1 gene between them, was significantly associated with shorter survival in patients with GBM. CONCLUSIONS: In the present study it is found that LOH on chromosome 10 is an age-dependent event for patients with AAs and that LOH on marker D10S209 near the FGFR2 and DMBT1 loci is a significantly unfavorable prognostic factor. It is also reported that LOH on the PTEN/MMAC1 gene is a significantly unfavorable prognostic factor in patients with GBM.     

乳腺癌及癌前病变3号染色体短臂杂合性缺失的研究

目的研究乳腺癌及癌前病变中3号染色体短臂（3p）杂合性缺失（loss of heterozygosity,LOH）的发生情况。方法采用聚合酶链式反应及硝酸银染色等方法检测41例原发性乳腺癌及12例癌前病变中3p的11个微卫星位点LOH发生情况;用免疫组化方法检测40例乳腺癌中雌激素受体（ER）、孕激素受体（PR）、脆性组氨酸三联体（fragile histidine triad,FHIT）及人类MutL基因的同源基因（human MutL homologue,hMLH1）的表达情况。结果97％乳腺癌患者发生3p的LOH,检出率较高的位点是D3S1295（53．1％）、D3S1029（43．6％）和D3S1038（52．5％）,分别位于3p14、3021-p22和3p25。D3S1038位点LOH及hMLH1蛋白表达与部分临床病理学参数相关（P〈0．05）。D3S1295的LOH与FHIT蛋白表达负相关（P〈0．05）。癌前病变患者3pLOH发生率为41．7％,检出率较高的位点是D3S1295（27．3％）和D3S1029（16．7％）。最小共同丢失区位于3p14-p25。结论3p14-p25区段可能有与乳腺癌发生发展相关并影响乳腺癌生物学行为的候选抑癌基因,基因的部分缺失可影响其蛋白的表达。     

Malignant transformation-related genes in meningiomas: allelic loss on 1p36 and methylation status of p73 and RASSF1A

OBJECT: Analysis of meningiomas supports the suggestion that loss of heterozygosity (LOH) of chromosome arm 1p plays an important role in malignancy. The aim of this study was to identify genes related to meningioma progression from the benign state to the atypical and anaplastic states by examining 1p LOH and the promoter methylation of RASSF1A and p73. METHODS: The authors studied 40 surgical specimens (22 WHO Grade I, 11 Grade II, and seven Grade III) obtained in 37 patients with meningioma. The LOH at 1p36 was analyzed using microsatellite markers, and promoter methylation of p73 and RASSFIA was analyzed using methylation-specific polymerase chain reaction. RESULTS: No 1p LOH was detected in the Grade I tumors, whereas it was detected in more than 80% of the Grade II and III tumors. Methylation of the p73 promoter was observed in 81.8 and 71.4% of the Grade II and III tumors, respectively, but it was not observed in any of the Grade I tumors; methylation of the RASSF1A promoter was observed in 18.2, 63.6, and 42.9% of the Grade I, II, and III tumors, respectively. Interestingly, 1p LOH and p73 promoter hypermethylation were detected in the malignantly transformed tumors but not in the lower-grade primary ones. CONCLUSIONS: Based on the hypothesis that meningiomas cumulatively acquire genetic alterations and thus progress from the benign to the atypical and anaplastic states, genetic alterations in the methylation status of p73 or RASSF1A along with 1p LOH may result in the malignant transformation of a meningioma. This type of genetic fingerprint may play both diagnostic and therapeutic roles.     

Increased expression of tenascin in pheochromocytomas correlates with malignancy.

Tenascin is a significant extracellular matrix glycoprotein, which is upregulated in various neoplasias and pathologic processes. Pheochromocytomas are rare tumors of the sympathoadrenal system, whose malignancy is almost impossible to predict. There are no histologic or chemical markers available that would define the malignant behavior of these tumors, except the discovery of metastases. In our search for new markers, we investigated the immunohistochemical expression of tenascin in a large number of pheochromocytomas and paragangliomas. Seven tumors were metastasized and were thus considered malignant. Normal adrenal medulla was tenascin negative. A striking difference was seen between malignant and benign pheochromocytomas. All malignant pheochromocytomas expressed stromal tenascin strongly or moderately, whereas most benign pheochromocytomas (28 of 37, 70%) showed no or only weak immunopositivity. The staining was strong or moderate also in 13 of 28 (46%) of the tumors that showed histologically suspicious features, here called borderline tumors. Paragangliomas showed a more heterogeneous staining pattern, and no significant difference was found between benign and malignant paragangliomas. To our knowledge, this is the first study to demonstrate the expression of tenascin in pheochromocytomas and particularly the enhanced expression in malignant pheochromocytomas. We therefore suggest that tenascin may be associated with the malignant transformation and metastasis of pheochromocytomas. It is also a potential marker predicting more aggressive behavior in pheochromocytomas.     

Potential location of a bladder tumor suppressor gene on chromosome 9q at 9q13 to 9q22.1

Allelic losses involving chromosome 9q occur in a significant percentage of bladder tumors. Experimental evidence suggests that a putative tumor suppressor gene located on this chromosome may play a role in the development of bladder cancer. The precise location of this potential tumor suppressor gene is not clear. Previous studies have targeted a large region between 9p12-13 and 9q22 or 9p12 and 9q34.1 as the likely site. To further delineate the location of this gene, we examined 49 tumors by loss of heterozygosity (LOH) analysis, using seven microsatellite polymorhpic loci spanning from 9p21 to 9q34 of the chromosome. LOH was found in at least one of the loci in 20 (41%) of the tumors examined, and the majority (12 of 17; 71%) of the losses on 9q involved large segments or the entire chromosome arm. Although many of the tumors with large losses on 9q also involved 9p21, several tumors with small losses did not involve the 9p marker. Conversely, there were tumors with 9p21 losses that did not involve the q-arm. These data agree with recent findings that distinct tumor suppressor genes associated with bladder cancer are located on separate arms of chromosome 9. Among tumors with single locus LOHs, the most common deletion was located in 9q 13-21.2, which was detected by probe D9S15. This also is the smallest area of critical loss when LOH patterns of tumors with partial or interstitial losses were examined. Results of the study therefore suggest that a potential tumor suppressor gene may reside within or near the region of 9q13-22.1.     

Sarcomatoid carcinoma of the head and neck: molecular evidence for evolution and progression from conventional squamous cell carcinomas

The underlying events associated with the development of sarcomatoid head and neck squamous carcinoma and the biologic significance remain unknown. To investigate the genetic events involved in the evolution of this entity, comparative analysis of matched microdissected epithelial and sarcoma-like components from 11 primary sarcomatoid carcinomas was performed using microsatellite markers. Nine markers on chromosomes 4p, 9p, and 17p regions (3 per each chromosomal region) were selected based on their informativeness, small product size, and the high alterations in head and neck squamous carcinomas. In this study, loss of heterozygosity (LOH) in at least one marker in either component was noted in all 11 tumors, and instability was found in 10 instances (six in 3 paired specimens and four in the sarcomatoid area only). Concordant results in both components were found in 58 (79.5%) reactions (37 LOH and 21 retention of heterozygosity), and paradoxical findings were noted in 15 instances (20.5%). The latter included LOHs in only two conventional epithelial components and 13 sarcomatoid components. Both keratin-positive and -negative sarcomatoid tumors had a comparable frequency of LOH. The most frequently altered markers in both components were D9S168 and D9S171 (75% each) and D4S1587 (66%). The sarcomatoid components manifested distinctly high alterations at marker D17S520 on chromosome 17p. Our study supports: 1) an evolution of sarcomatoid carcinoma from the conventional epithelial-type, 2) a malignant nature of the sarcomatoid component, and 3) that molecular progression is associated with the sarcomatoid transformation.     

染色体1pter-p36.21杂合性缺失与瘢痕疙瘩的关系

目的寻找瘢痕疙瘩1pter-36.21中可能存在的肿瘤抑制基因的杂合性丢失(LOH)区域,为发现和定位瘢痕抑制基因提供线索和依据。方法采用聚合酶链反应(PCR)-变性聚丙烯酰胺凝胶电泳技术,对25例瘢痕疙瘩组织和外周静脉血标本进行微卫星分析。结果瘢痕疙瘩组织在所选的位点上的LOH发生率为60%(15/25),明显高于正常对照组织的4%(1/25,P<0.05),在所选的位点上均未发现微卫星不稳定性(MSI)。D1S243位点、D1S468位点、D1S507位点、D1S199位点的LOH发生率分别为28%(7/25)、40%(10/25)、52%(13/25)、12%(3/25),其中D1S243、D1S468、D1S507的LOH发生率比较具有统计学意义(P<0.05)。结论发生在D1S243-D1S468-D1S507位点的LOH存在与瘢痕疙瘩有关的潜在瘢痕抑制基因(SSG),而1pter-36.21上LOH微卫星不稳定性与瘢痕疙瘩发生的关系不大。     

Investigation of tumor suppressor genes apart from VHL on 3p by deletion mapping in sporadic clear cell renal cell carcinoma (cRCC)

ObjectivesTo investigate the most recurrent deletion loci on 3p12-p26 by deletion mapping studies by PCR-LOH and BAC array-FISH in sporadic conventional renal cell carcinoma (cRCC) and further, to evaluate the their clinicopathologic significance in cRCC. Comparative allelotyping studies in cRCC and major epithelial carcinomas (MEC) such as lung, breast, and bladder tumors were also carried out to investigate the specificity of the targeted loci in cRCC.Subjects and methodsA total of 40 c-RCC patients were enrolled in this study, categorized in to 2 groups: group I comprises of patients of stages I and II and group II includes patients at stages III and IV. Loss of heterozygosity (LOH) studies were performed by PCR using 15 microsatellite markers of region 3p12-p26 on paired normal-tumor tissues. The recurrent LOH loci found in 27 cRCC tumors were further validated by BAC array-FISH using 23 serially mapped BAC clones. Simultaneously, the allelic deletion status of fragile histidine triad (FHIT) gene was studied by FISH in cRCC and major epithelial carcinoma (MEC) tumors. The numerical aberrations of chromosome 3 were also studied using the centromere enumeration probe (CEP) probe for chromosome 3 to validate the observed allelic losses by BAC array-FISH in cRCC as well as MECs.ResultsOur study revealed 3 affected regions of LOH on 3p in cRCC: 3p12.2-p14.1, 3p14.2-p21.1, and 3p24.2-p26.1 in both group I (stages I and II) and group II (stage III and IV). Comparative allelotyping studies revealed that except for LOH loci D3S2406 (20%), D3S1766 (14%), and D3S1560 (20%), remaining affected loci revealed retention of heterozygosity (ROH) in breast carcinomas. Lung and bladder tumors revealed ROH at all affected LOH loci. FISH with FHIT gene probe revealed deletions in cRCC (88%), breast (30%), and lung tumors (10%). FHIT gene deletions frequency was almost equal in both groups I and II (>70%), whereas a locus 3p13 (D3S2454) revealed the highest LOH in group II (83%) patients in comparison to group I (16%). BAC array-FISH studies in cRCC identified 15 recurrent deletion loci at crucial regions, 3p12.2, 3p14.2, 3p21.3, and 3p24.2-p26 with long continuous deletion of 3p14.1-p26.1 exclusively in patients of stages III and IV. Validation of LOH loci in breast carcinomas by BAC array-FISH with BAC clones mapped at these loci revealed comparatively lower deletion frequency for RP11-59E22 (3p12.2) (30%), RP11-759B7(3p21.1) (12%), and RP11-57D6 (3p25.2, proximal to VHL) (15%) than cRCC.ConclusionMolecular cytogenetic studies by BAC array-FISH was found to be more sensitive over LOH. Deletion patterns on 3p explored that deletion of FHIT and flanking loci may occur as an initiating event followed by deletions at 3p12.2, 3p21.31–3p21.32, and 3p24.2–3p26.1 in the initial stage of development of disease, while continuous large deletions of 3p21.3–3p26.1 and 3p14.1–3p26.1 occur as progressive deletion due to genetic instability. Lack of VHL along with flanking loci in 50% cRCC patients that included both groups I and II supported the hypothesis of both VHL dependent and VHL independent pathways in cRCC tumorigenesis. Comparative allelotyping studies in cRCC and MECs indicated association of specific targeted loci including VHL in cRCC. Further expansion of these studies with characterization of the genes at targeted loci and correlation with clinical outcome will explore the prognostic significance and also provide an insight into the mechanisms of tumor suppressive pathways in genitourinary cancers such as CRCC.     

散发性结直肠癌染色体20q11-13区杂合性缺失精细定位

目的 研究散发性结直肠癌20号染色体杂合性缺失情况,并对20q11-13区进行精细定位.方法 收集1998年至1999年上海市第一人民医院83例结直肠癌患者的肿瘤组织和对应的正常黏膜组织,采用10个微卫星标记的引物对20号染色体进行杂合性缺失分析,在20q11-13区域另取10个微卫星标记的引物并对标本进行PCR分析.以Genescan 3.1和Genotyper 2.1软件进行基因分型和精确定位.结果 在20号染色体上发现一个高频杂合性缺失区即20q11-13区.进一步的精细定位,界定了两个高频杂合性缺失区:20q11.2、20q12,并在该杂合性缺失区发现了抑癌基因E2F1、PMP24和MAFB.结论 20号染色体有两个高频精细杂合性缺失区,该区很可能存在一个或多个与结直肠癌相关的新的抑癌基因.     

Loss of heterozygosity and lack of mutations of the XPG/ERCC5 DNA repair gene at 13q33 in prostate cancer.

BACKGROUND: Three regions of chromosome 13 were previously identified for having loss of heterozygosity (LOH) in human prostate cancer. One of them, at 13q33, was defined by LOH at markers D13S158 and D13S280. The XPG/ERCC5 gene, a DNA repair gene that when mutated in the germline leads to xeroderma pigmentosum, has been mapped to 13q33, within one megabase of D13S158 and D13S280. This paper describes LOH and mutational analysis of the XPG gene in human prostate cancers, in order to determine whether the XPG gene is involved in the development of prostate cancer. METHODS: LOH of the XPG gene was analyzed in 40 primary prostate cancers and 14 metastases by using the microsatellite assay, and its mutations were examined in 5 cell lines, 14 metastases, and 8 tumors with LOH at 13q33 by using the single-strand conformation polymorphism (SSCP)-direct DNA sequencing analysis. RESULTS: Four of the 29 (14%) informative primary tumors and 4 of 8 (50%) metastases showed LOH for the XPG gene. Analysis of the 8 tumors with LOH at the 13q33 region, 14 metastases, and 5 cell lines of prostate cancer revealed two polymorphisms but no mutation of the gene. The polymorphism in exon 2 did not change the amino-acid sequence of the XPG protein, but the exon 15 polymorphism altered codon 1104 from histidine to aspartic acid. The two polymorphisms also occurred in individuals without prostate cancer. CONCLUSIONS: LOH at XPG in prostate cancer supports the conclusion that the 13q33 region contains a gene important in the development of prostate cancer, while lack of mutations of the gene suggests that XPG is not the target gene involved.