Microsatellite alterations and target gene mutations in the early stages of multiple gastric cancer.

Multiple gastric cancers may develop through the same genetic background: the mutator pathway due to defects in DNA mismatch repair genes, or the suppressor pathway due to defects in tumour suppressor genes. To clarify the critical genetic events in the early stages of multiple gastric cancer development, 29 early and four advanced gastric cancers were examined from 12 patients. Microsatellite alterations were studied involving microsatellite instability (MSI) and loss of heterozygosity (LOH) at tumour suppressor loci, representative of the mutator pathway and the suppressor pathway, respectively, as well as mutations of target genes (TGF-beta RII, BAX, hMSH3, and E2F-4). MSI was determined in ten cancers (10/33; 30.3%) from seven patients (7/12; 58.3%). LOH was detected in six cancers (6/33; 18.2%) from five patients (5/12; 41.7%), most frequently at TP53, in four cancers (4/33; 12.1%) from four patients (4/12; 33.3%). In cases with multiple gastric cancers in the same stomach, the MSI status was generally the same, but in two patients (2/12; 16.8%) a tumour with MSI-H and another with LOH were found to co-exist in the same stomach. As for mutations of the target genes, it was found that E2F-4 was mutated in six cancers (6/33; 18.2%) from four patients (4/12; 33.3%). Furthermore, identical E2F-4 mutations were detected in four of the six intestinal metaplastic mucosae adjacent to each cancer carrying an E2F-4 mutation. No mutations were detected in the other target genes. In conclusion, the present results indicate that the majority of multiple gastric cancers develop from the same genetic background, with the mutator pathway playing a more important role than the suppressor pathway. Mutations of E2F-4 are early events in multiple gastric cancer development, occurring even in the intestinal metaplastic mucosa, with mutations of other target genes to follow during cancer progression.     

原发性胃癌中19p部分微卫星多态位点杂合性缺失分析

目的 筛选胃癌19p部分微卫星多态位点的杂合性缺失（loss of heterozygosite,LOH)频率,以初步确定19p上与胃癌相关基因连锁最密切的微卫星多态位点。方法 采用聚合酶链反应-单链长度多态（polymerase chain reaction-single strand length polymorophism,PCR-SSLP)-银染法选取19p上9对微卫星多态标记（D19S424,D19S216,D19S406,D19S413。D19S221,D19S226,D19S411,D19S883,D19S886）,对43例原发性胃癌的杂合性缺失情况进行了分析。结果 43例中22例至少在1个位点发生LOH,总缺失率为48.88%,这9个位点的LOH频率分别为29.63%,11.53%,33.33%,8.57%,13.15%,8.00%,6.45%,6.89%,10.71%,在D19S886也同时出现微卫星不稳定性（microsatellite instability,MSI)17.85%。结论 提示19p上的LOH缺失频发区域可能涉及与人类原发性胃癌发生发展相关基因的存在。     

宫颈癌基因组HLA-Ⅰ类基因微卫星不稳定和杂合性缺失的研究

目的　探讨人白细胞抗原 Ⅰ类基因在宫颈癌中微卫星不稳定和杂合性缺失的情况 ,并构建宫颈癌基因组在该区域的精细缺失图谱。方法　应用聚合酶链反应 单链长度多态性 银染技术 ,对 3 0例宫颈癌活检标本进行杂合性缺失和微卫星不稳定的检测。结果　在 3 0例宫颈癌活检组织中 ,有 2 3例( 76.7% )存在有 1个或多个位点的杂合性缺失 ,微卫星位点C3 2 11的杂合性缺失频率最高 ,可达5 0 % ( 15 /3 0 )。微卫星不稳定的发生率为 66.7% ( 2 0 /3 0 ) ,其中位点D6S2 5 8发生微卫星不稳定频率最高 ,达 40 % ( 12 /3 0 )。结论　人白细胞抗原 Ⅰ类基因的微卫星不稳定和杂合性缺失在宫颈癌的发生和发展过程中起着重要作用 ,同时发现位点C12 5～C3 2 11之间是宫颈癌患者的一个最小的共同缺失区域 ,该区域可能存在有与宫颈癌相关的抑癌基因。     

中国汉族乳腺癌中BRCA1基因的杂合性丢失和微卫星不稳定性

目的探讨中国汉族妇女乳腺癌与乳腺癌基因１的关系。方法对ＢＲＣＡ１区域内的４个微卫星多态位点，应用聚合酶链式反应（ＰＣＲ）－聚丙烯酰胺尿素凝胶电泳（ＰＡＵＧＥ）－ＤＮＡ银染方法，对上海市５０例乳腺癌患者进行了ＢＲＣＡ１有关微卫星的ＬＯＨ和ＭＳＩ研究。结果患者中ＬＯＨ的发生率为５８％，ＭＳＩ的发生率为４６％；对患者进行临床分组，发现病期越晚ＬＯＨ率越高，ＭＳＩ与临床分期的关系不很确定。结论提示中国汉族人的乳腺癌的发生同与ＢＲＣＡ１基因相连锁的微卫星ＤＮＡ有关，因而也可能与ＢＲＣＡ１基因的突变有关。     

Genetic pathways in colorectal cancer: interest for the pathologist

Molecular biology studies have led to the identification of two different types of colorectal carcinomas. The first group, called LOH (for loss of heterozygosity), represents 80% of colorectal cancers and is characterised by aneuploidy, allelic losses and a location in the distal colon. The second group displays phenotypic microsatellite instability (MSI-positive tumours), has a near-diploid karyotype and a relatively low frequency of allelic losses. It accounts for 15% of all colorectal cancers and for about 30% of right-sided cancers. Four different pathways have been identified as responsible for tumour progression: the WNT/Wingless, the K-ras, the Transforming growth factor (TGF) and the P53 pathways. The involvement of these pathways depends on the tumour type. In LOH-positive tumours, the WNT/Wingless pathway is activated through an APC mutation, whereas MSI+ tumours do so through a catenin stabilising mutation. The TGFb growth inhibitory pathway is altered either by mutations in the signal transduction molecules SMAD2 and SMAD4 in LOH positive tumours or by mutations of TGFbRII in MSI+ tumours. In the p53 pathway, mutations in BAX may contribute to the adenoma-carcinoma transition just as p53 mutations may do in LOH positive tumours. Until now, cancer phenotype determination has had no clinical implications. However, the predictive value of the MSI status was recently stressed as a predictive factor for response to chemotherapy. Immunohistochemistry could represent a complementary strategy to molecular biology in assessing MSI status. This simple test would allow to screen all colorectal carcinomas for MSI status, which would provide valuable management information in addition to the histological assessment for tumour stage and grade.     

肝细胞癌8号染色体微卫星变异及其与临床病理特征的关系

目的　探讨肝细胞癌 (HCC)微卫星变异的特点及其与临床病理表现的相关性。方法采用毛细管电泳DNA分析系统 ,对 5 6例HCC中 8号染色体上 10个微卫星的杂合子丢失 (LOH)、微卫星不稳定性 (MSI)和等位基因失衡 (AI) 3种变异特征进行检测。结果　 5 6例HCC在 8号染色体上 10个基因位点发生LOH的总频率为 6 6 1% (37/ 5 6 ) ,LOH以D8S2 6 1最高为 5 3 5 % (2 3/ 4 3) ,其次为D8S172 1(5 2 5 % )和D8S1771(5 2 5 % )。D8S2 77基因位点 ,血清HBsAg阳性患者的LOH频率显著高于HBsAg阴性者 (P <0 0 1) ,D8S2 6 1、D8S2 98和D8S1733基因位点 ,血清HBsAg阴性患者的LOH频率显著高于HBsAg阳性者 (P <0 0 1) ;D8S2 98和D8S1771基因位点 ,直径 >3cm肿瘤的LOH率明显高于≤ 3cm组 (P <0 0 5和P <0 0 1) ;在D8S172 1基因位点 ,无包膜或包膜不完整的肿瘤的LOH显著高于包膜完整的肿瘤 (P <0 0 1) ;D8S2 98和D8S1771基因位点 ,肝内转移者的LOH明显高于无肝内转移者 (P <0 0 5 )。MSI的频率为 12 5 % (7/ 5 6 ) ,AI的频率为 19 6 % (11/ 5 6 )。结论HCC在 8号染色体上存在广泛的微卫星变异 ,其中LOH方式在HCC的发生和发展过程中起重要作用 ,MSI的作用次之。特定基因位点的LOH与临床和病理学参数有一定的相关性     

Allelic alterations in nontumorous liver tissues and corresponding hepatocellular carcinomas from chinese patients

Allelic imbalance may play an important in tumor progression in hepatocarcinogenesis, but the genetic background of the corresponding nontumorous liver in hepatocellular carcinoma (HCC) is not well defined. We studied the incidence of loss of heterozygosity (LOH) and microsatellite instability (MSI) by microsatellite analysis in both nontumorous livers and the corresponding tumors, by comparing them with the normal DNA from Chinese patients with resected primary HCCs. We also evaluated the pathologic significance of the alterations. We used 18 highly polymorphic microsatellite markers on chromosomes 1, 3, 4, 7, 8, 9, 13, 16, 17, and 18. Our results showed that 70.6% (24 of 34) of the HCCs exhibited LOH at 1 or more loci, and that the overall fractional allelic loss (FAL) was 0.169. MSI was observed in only 1 tumor. In contrast, the nontumorous livers of the HCCs showed a very low incidence of LOH, with only a single LOH detected in 1 of 34 (2.9%) of the nontumorous livers, with an overall FAL index of 0.005. Tumors with LOH at 1 or more loci had significantly more frequent venous invasion (P = 0.019). Allelic loss at locus D9S199 (9p23) was seen more frequently in larger tumors (P = 0.031), and, less significantly, allelic loss at locus D16S516 (16q24.1) was seen more frequently in larger tumors (P = 0.059). LOH was common in predominantly hepatitis B virus-associated HCCs from Chinese patients. However, LOH or MSI in the corresponding cirrhotic or noncirrhotic livers was uncommon.     

头颈部鳞癌的微卫星不稳定性和杂合性丢失的初步研究

目的:探讨头颈部鳞癌的微卫星不稳定性(MSI)及杂合性丢失(LOH)。方法:选择来自3、5、6、8、9、13、17和18号染色体的15个微卫星标志对36例头颈部鳞癌标本和相应的外周血进行微卫星分析。结果:36例头颈部鳞癌中,27.8%(10/36)分别有1-8个位点存在MSI,MSI发生率较高的位点为:D17S520(22.9%)、D6S105(16.7%)和D8S264(13.9%)。在9p21-p22和3p14等处存在一定的LOH。微卫星异常的检出率与肿瘤分期、分级无相关性。结论:提示MSI是头颈部鳞癌中较为常见的遗传学变化,染色体9p21-p22和3p14区域可能存在与头颈部鳞癌有关的抑癌基因。     

Microsatellite instability is uncommon in lymphoepithelioma-like carcinoma of the lung

Primary lymphoepithelioma-like carcinoma of the lung (LELC) shares some morphologic and clinical characteristics with malignancies associated with microsatellite instability (MSI). The aims of our study were to determine the MSI status in LELC and compare these findings with stage I non-small cell lung carcinoma (NSCLC) with marked lymphocytic host response (MLHR). We assessed MSI by a DNA-based polymerase chain reaction assay using mononucleotide (BAT25 and BAT26) and dinucleotide (D2S123, D5S346, and D17S250) repeats. MSI was detected in 2 (29%) of 7 LELC cases with only 1 marker (D17S250), and in 3 (19%) of 16 NSCLC cases with MLHR with only 2 markers (1D2S123 and 2 D17S250). Loss of heterozygosity (LOH) was detected at 1 or 2 of 3 dinucleotide repeats in 11 NSCLC cases (69%) with MLHR and 3 LELC cases (43%) (P = .36). The overall frequencies of LOH in NSCLC with MLHR were 29% and 19% in LELC (P = .55). MSI is very uncommon in LELC, indicating that MSI is not an important event in carcinogenesis for this tumor subtype. The presence of LOH suggests a probable role of tumor suppressor genes in LELC carcinogenesis.     

Allelic imbalance and microsatellite instability in chromosomes 2p, 3p, 5q, and 18q in esophageal squamous carcinoma in patients from South Africa.

Microsatellite polymerase chain reaction (PCR) and fluorescent DNA technology was used to assess allelic imbalance (AI) or loss of heterozygosity (LOH) and microsatellite instability (MSI) in chromosomes 2p, 3p, 5q, and 18q in esophagectomy specimens from 39 patients who had squamous carcinoma and who lived in a high-incidence geographic location in South Africa. The squamous carcinomas were graded by conventional light microscopy and staged using the tumor-node-metastasis (TNM)-Union Internationale Contre Le Cancer (UICC) criteria. The DNA was isolated using proteinase K digestion and standard phenol-chloroform extraction procedure. Microsatellite PCR was performed using fluorescent, CY5-labeled primers for the following markers: D2S123 (2p), D3S659 (3p), D3S1255 (3p), D5S346 (5q), DCC (18q), D18S34 (18q), and D18S58 (18q). These markers were chosen because they are the most frequently used and most informative markers for these particular gene loci. Results were analyzed using software attached to an automated DNA sequencer. Molecular changes obtained were correlated with clinicopathologic parameters. Molecular analysis did not correlate with clinicopathologic features, such as tumor grade, stage, or lymph node status. No correlation with patient outcome was seen, though only limited follow-ups were obtained. Rates of MSI and LOH on 3p and 18q in these specimens are similar to the range seen in studies from other geographic areas. However, a striking point of departure is the high LOH (30% of informative cases) seen on 2p.     

Microsatellite analysis of breast carcinoma and corresponding local recurrences

Local recurrence is a serious complication of breast carcinoma that reduces quality of life and influences prognosis. The aim of this study was to determine whether local recurrences of breast carcinoma are genetically related to the primary tumours. Forty cases of locally recurrent breast carcinomas (median onset: 3.6 years after primary surgery) were analysed: 22 patients had undergone breast-conserving therapy and 18 mastectomy. Eighteen microsatellites on chromosomes 2p, 3p, 5q, 10q, 11p, 11q, 13q, 17q, 17p, 18p were amplified by PCR using fluorescent-labelled primers, automatically detected after polyacrylamide gel electrophoresis and analysed for loss of heterozygosity (LOH) or microsatellite instability (MSI). Follow-up data were available for 39 cases with a median value of 89 months. All LOH and MSI found in the primary tumours were also present in the corresponding recurrences, indicating that they are genetically related to the primary tumours and not secondary malignancies in the same breast. MSI was found in three cases, of which one harboured MSI at more than two loci. The median value of LOH per case was significantly higher in the recurrent (four per case) compared to the primary tumours (two per case; p < 0.001, Mann-Whitney test), reflecting the genotype of tumour progression. Early local recurrence was associated with specific LOH for TP53.15 (p = 0.018, log-rank test) in the primary tumours. LOH on D13S1699 or D17S855 was associated with lymph node metastases (p = 0.024 and p = 0.019, respectively; chi-square test). In addition, tumour grade, lack of oestrogen or progesterone receptor expression, young patient age and early appearance of local recurrence significantly correlated with poor survival. The development of local recurrence despite clear resection margins may result from residual DCIS distant from the invasive carcinoma, homing of circulating tumour cells, or genetically altered, histologically normal breast tissue not immediately adjacent to the invasive carcinoma.     

Chromosome 11q in sporadic colorectal carcinoma: patterns of allele loss and their significance for tumorigenesis.

AIMS: To analyse the frequency of loss of heterozygosity (allele loss, LOH) in a large sample of colorectal carcinomas using highly informative markers along chromosome 11q. METHODS: One hundred paired samples of colorectal cancer and normal tissue were genotyped at six microsatellite markers on chromosome 11q (cen-D11S1313-D11S901-DRD2/NCAM-D11S29- D11S968-tel). The high levels of heterozygosity at these markers allow allele loss to be determined in about 80% of cases at any one locus. The frequency of replication errors (RERs, microsatellite instability) has also been determined. RESULTS: LOH was found at frequencies of 25% and 29% at the distal D11S968 (11qter) and D11S29 (11q23.3) loci, slightly above the accepted baseline of 0-20%. Allele loss at NCAM, DRD2, D11S901, and D11S1313 was not raised above baseline levels. The probable genetic mechanism of allele loss--chromosomal non-disjunction, mitotic recombination, deletion, or gene conversion--seemed to vary between tumours and no consistent mechanism of mutation was found. Microsatellite instability was found in 23 (23%) tumours. No associations were found between LOH and clinical data (patient sex, age at presentation, tumour site, and Duke's stage). CONCLUSIONS: Although gene(s) on 11q may have a role in the development of a minority of colorectal carcinomas, this study provides evidence against the general importance of allele loss on chromosome 11q in the pathogenesis of colorectal cancer. The results also have implications for the importance of 11q in other cancers: it seems less likely that a single tumour supressor gene at this location promotes the growth of all types of tumour when lost. Rather, one or more genes with tissue specific effects may be involved.     

中国人胃癌骨形态发生蛋白3基因遗传的不稳定和甲基化

目的 探讨骨形态发生蛋白3(BMP3)基因遗传不稳定性及异常甲基化与胃癌进展的关系,为揭示BMP3基因作用机制和胃癌发生发展机制提供实验依据. 方法 采用聚合酶链反应-单链构象多态(PCR-SSCP)技术分析中国人胃癌BMP3基因D4S2922、 D4S2964位点微卫星不稳定性(MSI)和杂合性缺失(LOH);使用甲基化特异PCR法检测BMP3基因启动子的甲基化状况. 结果 在本实验中,50例胃癌标本BMP3基因微卫星位点MSI、 LOH的阳性率分别为16.00%和20.00%,并且LOH检出率在胃癌的TNM Ⅲ+Ⅳ期高于Ⅰ+Ⅱ期(P<0.01),并随淋巴转移的发生而增高(P<0.01).45例胃癌标本中BMP3基因启动子区域甲基化阳性率为64.44%,其检出率与胃癌分化程度、浆膜浸润、淋巴转移及TNM分期均无关.此外,MSI阴性组的甲基化阳性率为71.05%, 显著高于MSI阴性组的28.58%(P<0.05). 结论 BMP3基因遗传不稳定和启动子甲基化存在于胃癌的发生发展中.LOH多发生于胃癌的晚期阶段并赋予胃癌高侵袭、预后差的表型.BMP3基因启动子高甲基化可能是胃癌发生因素之一.     

Microsatellite instability in ovarian and other pelvic carcinomas

Twenty-six cases of ovarian carcinoma and six cases of other pelvic neoplasms were analyzed for microsatellite instability (MSI) using frozen specimens, fluorescence technology, and four selected markers (D2S123 on chromosome 2, D18S58 on chromosome 18, BAT26 on chromosome 2, and BAT40 on chromosome 1). This procedure also allowed the detection of loss of heterogeneity (LOH) at the four selected loci. One of the cases of ovarian carcinoma exhibited MSI and this was evident at three loci. Of 44 informative loci, 7 exhibited LOH representing 3 cases of ovarian carcinoma, 3 of 4 cases of primary peritoneal carcinoma, and one case of unknown primary. These data support other findings that MSI is not a frequent occurrence in ovarian cancer; however, LOH is a more frequent event and may be a target for the development of diagnostic/prognostic procedures for ovarian and primary peritoneal carcinoma.     

鼻咽癌染色体1pter-p36.11杂合性缺失

目的构建鼻咽癌染色体1pter-p36.11(63.4cM)区域内的杂合性缺失精细图谱,为进一步寻找鼻咽癌相关基因提供依据。方法在比较基因组杂交和间期荧光原位杂交研究基础上,应用淋巴分离液将肿瘤组织的肿瘤细胞与淋巴细胞分离并以淋巴细胞DNA作相应正常对照,利用1pter-p36.11区域内的20个微卫星多态位点(平均间距3cM)对47例鼻咽癌活检组织用杂合性缺失(LOH)分析法进行LOH分析并绘制其精细缺失图谱。结果在47例鼻咽癌患者中,至少有一个位点存在LOH的有37例(82.2%),其中LOH频率最高的为D1S234(50.0%),位于1p36.13,其次为D1S2644(37.5%),位于1p36.22;微卫星不稳定频率最高的为D1S243(37.5%),位于1p36.33,其次为D1S199(30.2%),位于1p36.21;D1S234的LOH及D1S199的MI与临床分期相关无显著性意义（P>0.05）。结论鼻咽癌染色体1pter-p36.11之间63.4cM区域内有两个共同的缺失区,分别位于1p36.13(D1S234,2.0cM)与1p36.22(D1S436-D1S2644,6.3cM),其间有一个微卫星不稳定位点D1S199,D1S436-D1S199-D1S234区域内可能有一个或几个在早期与鼻咽癌形成相关的肿瘤抑制基因。     

Microsatellite instability in poorly differentiated adenocarcinomas of the colon and rectum: relationship to clinicopathological features

BACKGROUND: Poorly differentiated adenocarcinomas of the colon and rectum (Por) feature the worst prognosis among the various types of colorectal carcinomas. Por is highly associated with microsatellite instability (MSI), although MSI is associated with an improved prognosis in colorectal cancers. AIM: To investigate the influence of MSI on clinicopathological features and survival of patients affected by Por. METHODS: 53 patients affected by Por were investigated. DNA extracted from tumour sections and the corresponding normal tissue was analysed by PCR at five microsatellite loci: BAT25, BAT26, D2S123, D5S346 and D17S250. Tumours with alterations at two or more loci were classified as MSI-Por. The others were classified as microsatellite stability (MSS)-Por. The clinicopathological features and survival of patients with MSI-Por and MSS-Por were investigated. RESULTS: Of the 53 patients who were examined, 12 (22.6%) were MSI-Por, whereas 41 (77.4%) were MSS-Por. Significant differences were found between MSI-Por and MSS-Por regarding the following clinicopathological features: age, gender, lymph-node metastasis (MSI-Por: 4/12; MSS-Por: 33/41), TNM stage (MSI-Por: T1/T2/T3/T4 = 2/6/2/2; MSS-Por: 3/3/19/16) and lymphatic invasion (MSI-Por: 4/10; MSS-Por: 27/35). Kaplan-Meier survival curves and log-rank analysis showed that MSI-Por was associated with better prognosis than MSS-Por, although no significant difference was found. CONCLUSIONS: Compared with MSS-Por, MSI-Por is significantly associated with a low incidence of lymph-node metastases and a low stage. This indicates that MSI-Por is a less aggressive subtype.     

Alterations in p53 predict response to preoperative high dose chemotherapy in patients with gastric cancer.

AIMS: To evaluate the usefulness of molecular markers in predicting histopathological and clinical response to preoperative high dose chemotherapy (HDCT) and survival of patients with advanced gastric cancer. METHODS: In a phase II trial, 25 patients with metastatic gastric cancer received preoperative tandem HDCT consisting of etoposide, cisplatin, and mitomycin, followed by autologous bone marrow transplantation to achieve surgical resectability. Samples before and after treatment, from normal and tumour tissue, were characterised histopathologically, and both p53 and BAX expression was analysed by immunohistochemistry. Pretreatment formalin fixed, paraffin wax embedded samples from normal and tumour tissue were microdissected, and the extracted DNA was preamplified using improved primer extension preamplification polymerase chain reaction. Detection of microsatellite instability (MSI) or loss of heterozygosity (LOH) was performed using markers for p53, BAX, BAT25, BAT26, D2S123, D17S250, and APC. Exons 5-9 of the p53 gene were sequenced directly on ABI 373. RESULTS: Four parameters were significantly associated with response to chemotherapy and prolonged overall survival: positive p53 immunostaining, positive p53 mutation status before chemotherapy, strong histological regression induced by preoperative HDCT, and surgical treatment. Patients's sex or age, tumour location or stage, lymph node status, Lauren classification, MSI, or LOH did not influence duration of survival significantly in this high risk population. CONCLUSION: Positive p53 immunostaining and p53 mutation status in pretreatment tumour biopsies might be useful molecular predictors of response and prognosis in patients with advanced gastric cancer treated by preoperative HDCT.     

Abnormalities of chromosome 17 in oesophageal cancer

BACKGROUND: Oesophageal cancer is the most common malignancy encountered in South African males, especially in the Eastern Cape and surrounding region of South Africa. There are a number of risk factors and predisposing conditions that have been implicated in the aetiology of the disease. The tylosis oesophageal cancer (TOC) gene, localised to a small region on chromosome 17q25, has been shown to be associated with oesophageal squamous cell carcinoma. AIM: To investigate loss of heterozygosity (LOH) and microsatellite instability (MSI) in the region of the TOC locus. METHODS: In 74 oesophagectomy specimens for squamous cell carcinoma, microsatellite PCR was performed using five fluorescently labelled TOC markers. The PCR products were analysed and the data correlated with clinicopathological findings. RESULTS: LOH ranged from 25% to 60%. LOH for the individual markers was as follows: D17S1839, 25%; D17S1864, 36%; D17S1817, 38%; D17S785, 47.8%; and D17S579, 60%. MSI ranged from 4.1% to 6.8% for the five loci in the 17q region. MSI was 4.1% for the markers D17S579, D17S785 and D17S1817. Marker D17S1864 showed MSI to occur in 4 cases (5.4%) and marker D17S1839 in 5 cases (6.8%). CONCLUSION: No significant relationship between genetic and clinical parameters was observed; however, aberrations in poorly differentiated tumours were high for markers D17S579 and D17S1864 (25% and 37%, respectively), indicating that these markers may have an underlying role in the molecular pathogenesis of oesophageal squamous cell carcinoma. In addition, 63% of patients who died showed LOH for the markers D17S579, D17S1864 and D17S1817.     

THE FREQUENCY AND MECHANISM OF LOSS OF HETEROZYGOSITY ON CHROMOSOME 11q IN BREAST CANCER

Loss of heterozygosity (LOH, allele loss) occurs frequently on the long arm of chromosome 11 in breast cancer. Seventy-one paired tumour/normal DNA samples from breast cancer patients under 50 years old were studied for allele loss at four microsatellite loci on 11q: D11S29 (11q23.3), NCAM (11q22–q23), D11S968 (11qtel), and D11S1313 (11qcen). The maximum frequency of LOH (≈35 per cent) was found at the D11S29 and NCAM loci. This result is consistent with previous studies and the frequency of allele loss is moderate to high compared with the usual baseline of 0–20 per cent. In most of the cases studied, LOH on chromosome 11q could be accounted for by one of two mechanisms. Either chromosomal non-disjunction had occurred, or sequences stretching from the telomere at least as far as NCAM had undergone deletion or mitotic recombination. These results suggest that a putative tumour suppressor gene is most likely to exist near 11q22–q23. There was a very low frequency of microsatellite instability in the tumours. An association was found between lack of progesterone receptor (PgR) expression and LOH at NCAM , suggesting that deletion of sequences on 11q may prevent high levels of PgR expression in some cases.     

Role of E-cadherin gene in gall bladder cancer and its precursor lesions

The aim was to investigate the genomic instability in the E-cadherin (CDH1) gene and to correlate it with its protein expression in gall bladder cancer (GBC) and in other gall bladder (GB) diseases viz. chronic cholecystitis (CC), xantho-granulomatous cholecystitis (XGC), and normal GB to explicate its role in GBC tumorigenesis. Microsatellite instability (MSI) and loss of heterozygosity (LOH) in CDH1 were studied using D16S421, D16S496, D16S503, D16S512, D16S2624, and D16S3021 microsatellite markers and D2S123 (2p16), D2S382 (2q24), D6S292 (6q21–23), D7S480 (7q31), and D17S796 (17p13.1–3) were used to investigate genomic instability at 2p, 2q, 6q, 7q, and 17p loci in 40 GBC, 50 CC, 34 XGC, and 15 normal GB cases. Immunohistochemistry was carried out to analyze the E-cadherin and p53 protein expression. Overall LOH in CDH1 and other markers was high in GBC and XGC as compared to CC; however, it did not correlate with its protein expression in GBC cases. Loss of E-cadherin expression was high in GBC (67%), while majority of the CC (94%) and XGC (91%) cases retained positive E-cadherin expression. Overexpression of p53 was high in GBC (43%) whereas CC, XGC, normal GB cases were negative for p53 overexpression. None of the normal GB cases showed genomic instability at any of the markers. High LOH in CDH1 and other chromosomal loci in GBC indicated that the genomic instability followed a GBC>XGC>CC trend during the process of neoplastic transformation in GB, highlighting the fact that CC might act as a precursor lesion of GBC.