胃癌组织5q微卫星不稳定性与APC/MCC基因杂合性缺失的研究

目的探讨５ｑ微卫星不稳定性（ＭＳＩ）与ＡＰＣ／ＭＣＣ基因杂合缺失（ＬＯＨ）的关系。方法应用ＰＣＲ－ＳＳＬＰ及ＰＣＲ－ＲＦＬＰ技术分析５２例手术切除胃癌组织中ＭＳＩ及ＡＰＣ／ＭＭＣ基因ＬＯＨ。结果５ｑＭＳＩ检出率为３４．０％（１６／４７）,ＡＰＣ／ＭＣＣ基因ＬＯＨ率为３１．４％（１１／３５）。早期胃癌５ｑＭＳＩ阳性率为６６．７％（２／３）,ＡＰＣ／ＭＣＣＬＯＨ率为５０％（１／２）;进展期分别为３１．８（１４／４４）,３０．３％（１０／３３）。两组间无显著差别（Ｐ＞０．０５）。ＭＳＩ及杂合缺失与肿瘤大小、浸润深度、淋巴结转移及临床分期无关。粘液（印戒）细胞癌ＡＰＣ／ＭＣＣＬＯＨ率（５５．６％）显著高于高、中分化管状腺癌（Ｐ＜０．０５）。胃、肠两型胃癌５ｑＭＳＩ及ＡＰＣ／ＭＣＣＬＯＨ差异无显著性及５ｑＭＳＩ与ＡＰＣ／ＭＣＣＬＯＨ无相关性（Ｐ＞０．０５）。结论染色体５ｑＭＳＩ有ＡＰＣ／ＭＣＣ基因ＬＯＨ在两型胃癌的早期发生及发展中起一定作用。染色体５ｑ可能是胃癌的易感部位。     

大肠癌组织APC／MCC和DCC基因杂合缺失的研究

为评估ＡＰＣ／ＭＣＣ和ＤＣＣ基因在大肠癌发生和发展中的作用，采用聚合酶链反应（ＰＣＲ）技术，并配合限制性片段长度多态现象（ＲＦＬＰ）分析，对４１例大肠癌患者的组织ＡＰＣ／ＭＣＣ（位于染色体５ｑ２１）和ＤＣＣ基因（位于染色体１８ｑ２１．３）杂合缺失（ＬＯＨ）进行研究。ＡＰＣ基因ＬＯＨ率为２８．０％（７／２５），ＭＣＣ基因ＬＯＨ率为３６．４％（８／２２），两者综合分析ＬＯＨ率为３８．９％（１４／３８）。ＤＣＣ基因ＬＯＨ率为５５．３％（２１／３８）。ＤＣＣ基因在有淋巴结转移组的ＬＯＨ率（８０．０％）显著高于无淋巴结转移组（３９．１％）（Ｐ＜０．０５），在ＤｕｋｅｓＣ、Ｄ期组的ＬＯＨ率（７１．４％）显著高于Ａ、Ｂ期组（３５．３％）。以上结果提示，ＡＰＣ／ＭＣＣ和ＤＣＣ基因的ＬＯＨ是大肠癌常见的基因改变，ＤＣＣ基因ＬＯＨ的测定有可能成为大肠癌病人预后估计的指标。     

大肠癌组织APC/MCC基因杂合的缺失

目的研究大肠癌ＡＰＣ／ＭＣＣ基因杂合缺失的作用。方法采用ＰＣＲ技术，并配合限制性片段长度多态现象（ＲＦＬＰ）分析，对４１例外科手术切除大肠癌组织ＡＰＣ／ＭＣＣ基因杂合缺失（ＬＯＨ）进行检测。结果在大肠癌４１例中ＡＰＣ基因属信息个体者２５例，检出ＬＯＨ７例，占２８．０％；ＭＣＣ基因属信息个体者２２例，检出ＬＯＨ８例，占３６．４％。若将ＡＰＣ和ＭＣＣ基因进行综合分析，则信息个体者３６例，检出ＬＯＨ１４例，占３８．９％。ＡＰＣ和ＭＣＣ基因的ＬＯＨ与肿瘤大小、组织学类型、浆膜浸润、淋巴结转移及Ｄｕｋｅｓ分期无关（Ｐ＞０．０５）。结论ＡＰＣ和ＭＣＣ基因ＬＯＨ是大肠癌的常见改变     

p53基因突变及p53、APC基因缺失与胃癌关系的研究

为明确ｐ５３基因突变、缺失，ＡＰＣ基因缺失在胃癌发病机制中的作用，应用ＰＣＲ－ＳＳＣＰ方法对抑癌基因ｐ５３第４、５、６、７、８外显子、第６内含子在８７例胃癌及癌前病变中的突变规律以及ＰＣＲ－ＲＦＬＰ方法对ｐ５３基因第４外显子、第６内含子、ＡＰＣ基因在２５对胃癌及癌旁组织中的杂合缺失规律进行了探讨。结果发现，ｐ５３突变率在肠化、不典型增生、胃癌分别为３７．５％ （３／８），４２．１％（８／１９），５３．３％（１６／３０）。正常组织、浅表胃炎未发现ｐ５３突变。肠化、不典型增生、胃癌与正常对照组、浅表胃炎组相比均存在显著差异（Ｐ＜０．０５，Ｐ＜０．０１，Ｐ＜０．０１）。在肠化、不典型增生病变中未发现Ｅｘｏｎ８的突变，而在胃癌组Ｅｘｏｎ８的突变为４例（４／３０），提示Ｅｘｏｎ８的突变主要发生在晚期。在各病变组未发现Ｅｘｏｎ４、Ｉｎｔｒｏｎ６的突变。对Ｅｘｏｎ４、Ｉｎｔｒｏｎ６、ＡＰＣ基因的杂合缺失研究表明，２５对胃癌标本中有１９对Ｅｘｏｎ４杂合子，杂合率为７６．０％，９对有杂合缺失，ＬＯＨ为４７．４％，２３对Ｉｎｔｒｏｎ６杂合子，杂合率为９２．０％，其中２对为杂合缺失，ＬＯＨ为８．７％，１８对ＡＰＣ杂合子（１８／２５     

胃癌组织DCC基因（VNTR）的杂合性丢失和Bcl—2蛋白的表达

目的：为了研究ＤＣＣ基因的杂合性丢失（ＬＯＨ）和Ｂｃｌ－２蛋白过度表达在胃癌发生中的作用，方法：采用ＰＣＲ方法及免疫组织化学技术检测了胃癌组织ＤＣＣ基因的ＬＯＨ和Ｂｃｌ－２蛋白的表达。结果：结果发现，胃癌（信息个体）ＬＯＨ发生率为５４５％（１８／３３），Ｂｃｌ－２蛋白表达阳性率为６０％（３０／５０）；ⅢⅣ期胃癌ＬＯＨ发生率（８２２％，１５／１８）显著高于ⅠⅡ期胃癌２０％，３／１５）（Ｐ＜００１）；Ｂｃｌ－２蛋白的表达与ＤＣＣ基因的ＬＯＨ及胃癌大小、分化、淋巴结转移、浆膜浸润、临床分期及Ｌａｔｌｒｅｎ’ｓ分型无显著相关。结论：以上结果提示，ＤＣＣ基因的ＬＯＨ和Ｂｃｌ－２蛋白的高表达均参与了胃癌的发生，ＤＣＣ基因的ＬＯＨ是胃癌发生的晚期事件，其致癌机制与Ｂｃｌ－２有所不同     

PCR检测胃癌MCC、DCC基因和YNZ22位点串联重复序列的杂合性丢失

为探讨抑癌基因杂合性丢失（ＬＯＨ）在胃癌发生、发展中的作用，应用聚合酶链反应技术对４５例胃癌ＭＣＣ、ＤＣＣ基因和ＹＮＺ２２位点数量可变的串联重复序列（ＶＮＴＲ）区进行了分析。结果发现，胃癌ＭＣＣ基因ＬＯＨ率为３７．５％；ＤＣＣ为３３．３％；ＹＮＺ２２位点为５１．６％。ＬＯＨ与肿瘤大小、组织学分类、浸润深度、淋巴结转移无关。ＤＣＣ基因ＬＯＨ率在胃癌Ⅲ、Ⅳ期组（５０．０％）显著高于Ⅰ、Ⅱ期组（１４．３％）（Ｐ＜０．０５）。结果提示，ＭＣＣ、ＤＣＣ基因和ＹＮＺ２２位点ＬＯＨ参与了胃癌的发生与发展，ＤＣＣ基因ＬＯＨ可能与预后相关。     

17号染色体微卫星不稳定性和杂合性丢失与非小细胞肺癌的关系

目的　明确１７ 号染色体微卫星不稳定性（ＭＩ） 和杂合性丢失（ＬＯＨ） 与非小细胞肺癌（ＮＳＣＬＣ） 的关系。方法　对３５ 例ＮＳＣＬＣ肿瘤切除组织和肿瘤旁正常组织,采用聚合酶链反应微卫星长度多态性分析方法检测了１７ 号染色体上４ 个微卫星位点ＴＰ５３（１７ｐ１３－１）、ＴＨＲＡ１（１７ｑ１１－２１２）、Ｄ１７Ｓ５７９（１７ｑ１２２１）、Ｄ１７Ｓ８５５（１７ｑ２１） 的ＭＩ和ＬＯＨ。结果　３５ 例ＮＳＣＬＣ中,１７ 号染色体ＭＩ和（或）ＬＯＨ的发生率为６３％ （２４／３５）,其中ＭＩ为４０％ （１４／３５） ,ＬＯＨ 为３１％ （１１／３５）。同时表现有ＭＩ和ＬＯＨ 为９％ （３／３５） 。早期ＮＳＣＬＣ（ Ⅰ期和Ⅱ期） １７ 号染色体ＭＩ和（ 或）ＬＯＨ 发生率为７９％ （１５／１９）,明显大于晚期（ Ⅲ期）ＮＳＣＬＣ（４４％ ,７／１６,Ｐ＜０－０５） 。无纵隔淋巴结转移的ＮＳＣＬＣ的ＭＩ和（ 或）ＬＯＨ 发生率（８７％ ） 亦明显大于已有纵隔淋巴结转移者（４８％ ）,Ｐ＜ ０－０５。ＭＩ和（ 或）ＬＯＨ 在不同肿瘤组织类型以及不同组织细胞分化程度之间差异无显著性,Ｐ＞０．０５。结论　１７ 号染色体ＭＩ和ＬＯＨ 在ＮＳＣＬＣ的发生中可     

胃癌及癌前期病变粘膜芳香基酰胺酶同工酶的表达意义

目的探讨胃癌及癌前期病变粘膜芳香基酰胺酶（ＡＡＤ）同工酶的表达规律，寻找癌前期病变及早期癌的标志物．方法采用本室建立的圆盘等电聚焦电泳（ＣＩＥＦ）分离１２２例各种胃病粘膜（胃癌４１例，浅表性胃炎４８例，萎缩性胃炎３０例，胃溃疡８例，其中伴肠化１９例，异型增生８例）中ＡＡＤ同工酶．以６０ｇ／Ｌ丙烯酰胺作支持递质，ｐＨ３５～５０和ｐＨ３５～１００两种载体两性电解质建立ｐＨ梯度，加匀浆液５０μｌ，阴极及阳极电极液分别用０２ｍｏｌ／ＬＮａＯＨ和０５ｍｏｌ／ＬＨ３ＰＯ４，恒压电泳（１０℃）１８ｈ后以亮氨酰β萘胺作为基质呈色．结果ＡＡＤ分为８条区带，从阳极到阴极依次命名为ＡＡＤⅠ～ＡＡＤⅧ，其中ＡＡＤⅣ主要见于胃癌（９０２％），不完全大肠型肠化（８６７％）和异型增生（７５０％）；而不伴有肠化或异型增生的良性胃病和正常胃中则未发现．ＡＡＤⅣ的阳性率与胃癌病理类型、细胞分化程度及临床分期无相关，且ＡＡＤⅣ等电点和胎盘型ＡＡＤ等电点相当．结论ＡＡＤⅣ是一种癌胚蛋白，即胃癌组织特异性同工酶，是癌前期病变及早期癌的标志物．     

PCR检测胃癌MCC,DCC基因和YNZ22位点串联重复序列的杂全…

为探讨抑基因杂合性丢失（ＬＯＨ）在胃癌发生、发展中作用，应用聚合酶链反应技术对４５例胃癌ＭＣＣ、ＤＣＣ基因和ＹＮＺ２２位点数量可变的串联重复序列（ＶＮＴＲ）区进行了分析。结果发现，胃癌ＭＣＣ基因ＬＨＯ率为３７．５％；ＤＣＣ为３３．３％；ＹＮＺ２２位点为５１．６％。ＬＯＨ与肿瘤大小、组织学分类、浸润深度、淋巴结转移无关。ＤＣＣ基因ＬＯＨ率在胃癌Ⅲ、Ⅳ期组显著高于Ⅰ、Ⅱ期组（１４．３％）。结果提示，Ｍ     

53基因密码子249突变致肝细胞癌的机理研究

目的为了进一步探讨ＨＣＣ中ｐ５３基因密码子２４９突变的作用机理。方法收集密码子２４９突变率为３２９％的７０例南方地区手术切除ＨＣＣ标本，采用ＳＳＣＰ、ＩＨＣ和ＲＮＡ斑点杂交分析方法，深入研究了密码子２４９突变伴ＬＯＨ情况及其对ｐ５３基因转录和翻译的影响。结果９０％的密码子２４９突变伴ＬＯＨ。突变组中，ｐ５３蛋白和ｐ５３ｍＲＮＡ检出率分别为９１３％和９５７％，两者均显著高于无突变组（Ｐ＜０００１）。相关分析显示，ｐ５３基因的转录与翻译之间高度相关（ｒ＝０．８２０８）。结论ＬＯＨ是使ｐ５３基因密码子２４９突变发挥致癌作用的主要因素。ｐ５３基因密码子２４９的突变导致了ｐ５３基因在转录和翻译两水平上的增加，其中转录增加是ｐ５３蛋白表达增加的重要原因之一     

Telomere erosion is independent of microsatellite instability but related to loss of heterozygosity in gastric cancer

AIM: To correlate the length of the telomere to microsatellite instability (MSI) and loss of heterozygosity (LOH) of APC, MCC and DCC genes in gastric carcinomas. METHODS: Telomeric restriction fragment (TRF) length of gastric cancer was measured with Southern blot. LOH of APC, MCC and DCC genes, microsatellite instability (MSI) and frameshift mutation of hMSH6, TGF-betaRII and BAX genes were analyzed by PCR-based methods. RESULTS: Sixty-eight cases of sporadic gastric carcinoma were studied for MSI using five microsatellite markers. MSI in at least one locus was detected in 17 (25%) of 68 tumors analyzed. Frameshift mutations of hMSH6, TGF-betaRII and BAX were detected in 2,6 and 3 of gastric carcinomas respectively showing high MSI (> or = 2 loci, n = 8), but none was found in those showing low MSI (only one locus, n = 9) or MSS (tumor lacking MSI or stable, n = 51). Thirty-five cases, including all high MSI and low MSI, were studied for TRF. The mean TRF length was not correlated with clinicopathological parameters. No association was observed between TRF length and MSI or frameshift mutation. On the contrary, LOH at the DCC locus was related to telomere shortening (P<0.01). This tendency was also observed in APC and MCC genes, although there was no statistical significance. CONCLUSION: The development of gastric cancer can arise through two different genetic pathways. In high MSI gastric cancers, defective mismatch repair allows mutations to accumulate and generate the high MSI phenotype. In gastric cancers showing either low MSI or MSS, multiple deletions may represent the LOH pathway. Telomere erosion is independent of high MSI phenotype but related to the LOH pathway in gastric cancer.     

Mutation analysis of APC gene in gastric cancer with microsatellite instability

AIM：To evaluate the role of APCmutation in gastric carcinogenesis and to correlate APC mutation with microsatellite instability(MSI)in gastiric carcinomas.METHODS:APC mutation was measured with multiplexPCR,denaturing gradient gel electrophoresis and DNAsequencing;and MSIwas analyzed by PCR-based methods.RESULTS:Sixty-eight cases of sporadis gastric carcinoma were studied for APCmutation at exon15and MSI,APC mutaions were detected in15(22.1%)gastric cancers,Frequence of APCmutation(33.3%)in in testinal type of gastric ancer was significantly higher than that in diffuse type(13.1%,P&lt;0.05).On the contrary.on association was observed dbtween APC mutation and tumor size,differentiation,depth of invasion,metastasis or clinical stages.Using five microsatellite markers.MSIin at least one locus was detected in 17of68(25%)of the tumors analyzed,APC mutations were all detected in MSI-L(only one locus,n=9)orMSS(tumor lacking MSI or stable,n=51),but no mutation was found in MSI-H(≥2loci,n=8).CONCLUSION:APC mutation is involved in carcinogenesis of intestial type of gastric cancer and is independent of MSI phenotype but related to the LOH pathway in gastri cancer.     

Genetic changes in Slovenian patients with gastric adenocarcinoma evaluated in terms of microsatellite DNA

OBJECTIVES: Adenocarcinoma of the stomach is a relatively frequent malignant disease in Slovenia. We investigated the frequency of microsatellite instability (MSI) and loss of heterozygosity (LOH) in gastric carcinomas from the Slovenian population to determine their prognostic significance. METHODS: We evaluated MSI of mismatch repair associated loci and LOH on loci associated with following tumour suppressors: APC, nm23, Rb and p53. Results of the multiplex-PCR amplifications were correlated with clinicopathological factors for 73 patients. RESULTS: LOH was found in 52% of informative samples (20.5% LOH-H; 31.5% LOH-L). We found correlation of MSI with low-frequency LOH (LOH-L) in 11% of cases and with high-frequency LOH (LOH-H) tumours in 4% of cases. LOH-H and high-frequency MSI (MSI-H) were not associated. LOH was found in APC 36%, p53 33%, Rb 24% and nm23 33% of informative samples, whereas MSI was found in 30% of samples (12% MSI-H; 18% MSI-L). LOH-H status was associated with ulceration (P=0.029). LOH-N status was associated with diagnosis at higher TNM status (0.074) and infiltrative growth (P=0.006). Interestingly, in 6% of samples we found MSI on LOH loci as well. MSI-H was associated with higher age at diagnosis (r=0.24; P=0.04), antral location (r=0.252; P=0.04), intestinal type (P=0.044), expansive growth (P=0.001), tubular type (0.014), better differentiation (P=0.01), less nodal involvement (0.006) and better survival (P=0.022). The poorest prognosis was found in patients with both low-frequency MSI (MSI-L) and low-frequency LOH (LOH-L) tumours. CONCLUSION: The experimental design presented in the study may be of potential value for clinicians: at least five relevant markers for both MSI and LOH analysis may be needed to evaluate a gastric cancer (GC) patient's clinical status.     

Loss of heterozygosity at adenomatous polyposis coli,mutation in colorectal cancer and deleted in colorectal cancer genetic loci in colorectal cancers

AIM: To evaluate the role and analyze the loss of heterozygosity (LOH) of adenomatous polyposis coli (APC), mutation in colorectal cancer (MCC) and deleted in colorectal cancer (DCC) genes in the development and progression of colorectal cancers. METHODS: LOH at APC, MCC and DCC genes was examined in 41 surgically resected specimens of colorectal carcinomas by polymerase chain reaction and restriction fragment length polymorphism analysis technique. RESULTS: LOH of APC and MCC were observed in 7 of 25 (28.0%) and 8 of 22 (36.4%) of informative cases, respectively. When considered as one locus, the LOH frequency for APC/MCC was 14 of 36 (38.9%). LOH at DCC gene locus was detected in 21 of 38 (55.3%) of informative cases. No correlation was found between the LOH at APC or MCC gene and tumor histological types, size, invasion, lymph node metastasis and Dukes’ stages (P > 0.05). However, LOH rates at DCC locus in the group with lymph-node metastasis (80.0%) and in Dukes’ stages III and IV (71.4%) were significantly higher than those without lymph node metastasis (39.1%) and in Dukes’ stages I and II (35.3%) (P < 0.05). CONCLUSION: LOH at APC and/or MCC may occur more frequently in the early stages and plays a role in the initiation of colorectal cancer while LOH at DCC is frequent at late event and associated with the progression and metastasis of colorectal cancer.     

High microsatellite instability predicts good prognosis in intestinal-type gastric cancers

Background and Aim: A subset of gastric cancers showed high microsatellite instability (MSI‐H). The reported clinicopathological features of MSI‐H gastric cancers are heterogeneous, and specific factors associated with prognosis have not been identified. Methods: We analyzed the clinicopathological characteristics and prognostic factors in a large series (161 cases) of MSI‐H gastric cancers, and compared the results to 315 cases of microsatellite‐stable or low microsatellite‐instable gastric cancers. Results: The frequency of MSI‐H gastric cancers was 9% (161/1786). MSI‐H gastric cancers have distinct clinicopathological features, including female sex, older age, antral location, well‐to‐moderate differentiation, intestinal‐type Lauren classification, expanding‐type Ming classification, a non‐signet‐ring cell component, the presence of a mucinous component, a moderate‐to‐severe lymphoid stromal reaction, and a lower tumor stage. The MSI‐H phenotype was associated with better prognosis (P = 0.044), and male sex (P = 0.035, hazard ratios [HR]: 0.23), intestinal‐/mixed‐type Lauren classification (P < 0.001, HR: 0.09) and lower tumor stages (1 and 2, P = 0.001, HR: 0.08) were independently‐favorable prognostic factors. Conclusions: With unique clinicopathological features, intestinal‐type MSI‐H gastric cancers are associated with good prognosis and can be classified as a different subset of gastric cancers.     

Microsatellite instability in gallbladder carcinoma: two independent genetic pathways of gallbladder carcinogenesis

Although the genetic basis for gallbladder carcinogenesis has not been clarified, considerable evidence has shown that genetic alterations play an important role in the development and progression of human cancers. In this study, we analyzed 30 gallbladder carcinomas to investigate the role of genetic alterations in their tumorigenesis, and to study correlations with their clinicopathological features. Tissue samples were obtained from 30 patients with gallbladder carcinoma (11 men and 19 women; mean age, 62 years; age range, 38–80 years). Genomic DNAs were extracted from fresh tumor tissue. We examined loss of heterozygosity (LOH) in the p53, APC, DCC, RB, and NM23-H1 gene regions by polymerase chain reaction (PCR)-LOH assay using an automated fluorescent DNA sequencer employing four microsatellite markers (p53, APC, DCC, NM23-H1). Five additional microsatellite markers were used for the determination of microsatellite instability (MSI). LOH was found at p53 in 9 of 15 informative cases (60%), at DCC in 10 of 22 (45%), at APC in 5 of 15 (33%), at RB in 1 of 8 (13%), and at NM23-H1 in 1 of 15 (7%). MSI was observed in 5 of 30 cases (17%) in at least one chromosomal loci of these nine microsatellite markers. None of the patients with MSI-positive tumors showed lymph node metastasis, and there was an inverse correlation between MSI and the presence of LOH in gallbladder carcinoma. These results suggest that there are two independent genetic pathways in gallbladder carcinogenesis; that is, an MSI pathway and an LOH pathway. Received: December 24, 1999 / Accepted: May 26, 2000     

Loss of heterozygosity： An independent prognostic factor of colorectal cancer

AIM: Colorectal cancers result from the accumulation of several distinct genetic alterations. This study was to investigate the frequency and prognostic value of loss of heterozygosity (LOH) and microsatellite instability (MSI) at 14 genetic loci located near or within regions containing important genes implicated in colorectal tumorigenesis. METHODS: We studied colorectal cancers with corresponding normal mucosae in 207 patients (139 males and 68 females, mean age at the time of tumor resection 66.2±12.4 years, range 22-88 years). There were 37 right-sided colonic tumors, 85 left-sided colonic tumors and 85 rectal tumors. The distribution of tumor staging was stage Ⅰ in 25, stage Ⅱ in 73, stage Ⅲ in 68, and stage Ⅳ in 41. We analyzed the LOH and MSI of HPC1, hMSH2, hMLH1, APC, MET, P53, NH23-H1, DCC, BAT25, BAT26, D17S250, MYCL1 and D8S254 with fluorescent polymerase chain reaction and denatured gel electrophoresis. High-frequency LOH was determined to be greater than three, or more than 50% of the informative marker with LOH. High-frequency MSI (MSI-H) was determined as more than four markers with instability (>30%). Correlations of LOH and MSI with clinical outcomes and pathological features were analyzed and compared. RESULTS: The occurrence of MSI-H was 7.25%, located predominantly in the right colons (7/15) and had a higher frequency of poor differentiation (6/15) and mucin production (7/15). LOH in at least one genetic locus occurred in 78.7% of the tumors and was significantly associated with disease progression. Of the 166 potentially cured patients, 45 developed tumor recurrence within 36 mo of follow-up. Clinicopathological factors affecting 3-year disease-free survival (DFS) were TNM staging, grade of differentiation, preoperative CEA level, and high LOH status. Patients with high LOH tumors had a significantly lower DFS (50%) compared with patients with low LOH tumors (84%). Of the patients developing subsequent tumor recurrence, the number and percentage of LOH were 2.97 and 46.8% respectively, similar to the stage IV disease patients. TNM staging had the most significant impact on DFS, followed by high LOH status. CONCLUSION: Clinical manifestations of LOH and MSI are different in colorectal cancer patients. High-frequency LOH is associated with high metastatic potential of colorectal cancers.     

Is gastric cancer part of the tumour spectrum of hereditary non-polyposis colorectal cancer? A molecular genetic study

BACKGROUND: Gastric cancer is the second most common extracolonic malignancy in individuals with hereditary non-polyposis colorectal cancer (HNPCC)/Lynch syndrome. As gastric cancer is relatively common in the general population as well, it is not clear whether or not gastric cancer is a true HNPCC spectrum malignancy. AIM: To determine whether or not gastric cancer is a true HNPCC spectrum malignancy. Subjects and METHODS: The molecular and clinicopathological profiles of gastric cancers (n = 13) from HNPCC mutation carriers were evaluated and compared with the profiles of sporadic gastric cancers (n = 46) stratified by histology and microsatellite instability (MSI) status. RESULTS: This study on sporadic and HNPCC gastric cancers revealed several important universal associations. Loss of heterozygosity in the adenomatous polyposis coli (APC) region was associated with intestinal histology regardless of the MSI (p = 0.007). KRAS-mutations (p = 0.019) and frameshift mutations in repeat tracts of growth-regulatory genes (p<0.001) were associated with MSI tumours being absent in microsatellite stable (MSS) tumours. The average number of methylated tumour suppressor gene loci among the 24 genes studied (methylation index) was higher in MSI than in MSS tumours regardless of histology (p<0.001). Gastric cancers from HNPCC mutation carriers resembled sporadic intestinal MSI gastric cancers, except that MLH1 promoter methylation was absent (p<0.001) and the general methylation index was lower (p = 0.038), suggesting similar, but not identical, developmental pathways. All these lacked the mismatch repair protein corresponding to the germline mutation and displayed high MSI. CONCLUSION: The present molecular evidence, combined with the previous demonstration of an increased incidence relative to the general population, justify considering gastric cancers as true HNPCC spectrum malignancies.     

Alterations of tumor suppressor and tumor-related genes in the development and progression of gastric cancer

The development and progression of gastric cancer involves a number of genetic and epigenetic alterations of tumor suppressor and tumor-related genes. The majority of differentiated carcinomas arise from intestinal metaplastic mucosa and exhibit structurally altered tumor suppressor genes, typified by p53, which is inactivated via the classic two-hit mechanism, i.e. loss of heterozygosity (LOH) and mutation of the remaining allele. LOH at certain chromosomal loci accumulates during tumor progression. Approximately 20% of differentiated carcinomas show evidence of mutator pathway tumorigenesis due to hMLH1 inactivation via hypermethylation of promoter CpG islands, and exhibit high-frequency microsatellite instability. In contrast, undifferentiated carcinomas rarely exhibit structurally altered tumor suppressor genes. For instance, while methylation of E-cadherin is often observed in undifferentiated carcinomas, mutation of this gene is generally associated with the progression from differentiated to undifferentiated carcinomas. Hypermethylation of tumor suppressor and tumor-related genes, including APC, CHFR, DAP-kinase, DCC, E-cadherin, GSTP1, hMLH1, p16, PTEN, RASSF1A, RUNX3, and TSLC1, can be detected in both differentiated and undifferentiated carcinomas at varying frequencies. However, the significance of the hypermethylation varies according to the analyzed genomic region, and hypermethylation of these genes can also be present in non-neoplastic gastric epithelia. Promoter demethylation of specific genes, such as MAGE and synuclein y, can occur during the progressive stages of both histological types, and is associated with patient prognosis. Thus, while the molecular pathways of gastric carcinogenesis are dependent on histological background, specific genetic alterations can still be used for risk assessment, diagnosis, and prognosis.