HNPCC大肠腺瘤及癌组织微卫星不稳定与TGFβRII表达的关系

目的观察遗传性非息肉病性大肠癌（HNPCC）和大肠腺瘤癌组织中TGFβRRII、错配修复基因（hMLH1、hMSH2、hMSH6）蛋白表达和微卫星不稳定（MSI）的关系。方法以来源于33个HNPCC家系的大肠腺瘤28例和大肠腺癌14例为观察对象，以32例散发性大肠腺瘤和24例散发性大肠癌作为对照。采用免疫组织化学技术，检测大肠腺瘤及大肠腺癌组织中TGFβRRII、hMLH1、hMSH2、hMSH6蛋白表达。从活检组织中提取DNA，选择BAT-25、BAT-26、D2S123、D5S346、D17S250五个微卫星位点行荧光标记聚合酶链反应（PCR），以GeneMapper软件分析PCR产物。通过与正常黏膜微卫星序列PCR片断长度进行比较，判定腺瘤和癌组织的MSI情况。结果64．29％的HNPCC大肠腺瘤和71．43％的HNPCC大肠癌表现为MSI—H，明显高于散发性大肠腺瘤9．38％和散发性大肠癌12，5％。分别有67．86％的HNPCC大肠腺瘤和71.43％的HNPCC大肠癌表现为MMR蛋白表达缺失。明最高于散发性大肠腺瘤3．13％和散发性大肠癌12．5％。分别有57．14％的HNPCC大肠腺瘤和78.57％的HNPCC大肠癌表现为TGFβRRII低表达，明显高于散发性大肠腺瘤9．38％和散发性大肠癌41．67％。在MSI．H的HNPCC大肠腺瘤中，TGFl3RII低表达者占77．78％，MSI—H的HNPCC大肠癌中90％出现TGFβRRII的低表达。MSI—H的散发性大肠腺瘤中TGFβRRII的低表达率为66．67％，MSI—H的散发性大肠癌TGFβRRII的低表达率为100％。结论大部分HNPCC大肠腺瘤和大肠癌出现MSI—H，大部分MSI-H大肠腺瘤和大肠癌表现为TGFβRRII低表达。MSI、MMR、TGFβRRII的检测对腺瘤癌变风险的估计具有重要意义。     

HNPCC大肠腺瘤及癌组织微卫星不稳定与TGFβRRII表达的关系

目的观察遗传性非息肉病性大肠癌（HNPCC）和大肠腺瘤癌组织中TGFβRRII、错配修复基因（hMLH1、hMSH2、hMSH6）蛋白表达和微卫星不稳定（MSI）的关系。方法以来源于33个HNPCC家系的大肠腺瘤28例和大肠腺癌14例为观察对象，以32例散发性大肠腺瘤和24例散发性大肠癌作为对照。采用免疫组织化学技术，检测大肠腺瘤及大肠腺癌组织中TGFβRRII、hMLH1、hMSH2、hMSH6蛋白表达。从活检组织中提取DNA，选择BAT-25、BAT-26、D2S123、D5S346、D17S250五个微卫星位点行荧光标记聚合酶链反应（PCR），以GeneMapper软件分析PCR产物。通过与正常黏膜微卫星序列PCR片断长度进行比较，判定腺瘤和癌组织的MSI情况。结果64．29％的HNPCC大肠腺瘤和71．43％的HNPCC大肠癌表现为MSI—H，明显高于散发性大肠腺瘤9．38％和散发性大肠癌12，5％。分别有67．86％的HNPCC大肠腺瘤和71.43％的HNPCC大肠癌表现为MMR蛋白表达缺失。明最高于散发性大肠腺瘤3．13％和散发性大肠癌12．5％。分别有57．14％的HNPCC大肠腺瘤和78.57％的HNPCC大肠癌表现为TGFβRRII低表达，明显高于散发性大肠腺瘤9．38％和散发性大肠癌41．67％。在MSI．H的HNPCC大肠腺瘤中，TGFl3RII低表达者占77．78％，MSI—H的HNPCC大肠癌中90％出现TGFβRRII的低表达。MSI—H的散发性大肠腺瘤中TGFβRRII的低表达率为66．67％，MSI—H的散发性大肠癌TGFβRRII的低表达率为100％。结论大部分HNPCC大肠腺瘤和大肠癌出现MSI—H，大部分MSI-H大肠腺瘤和大肠癌表现为TGFβRRII低表达。MSI、MMR、TGFβRRII的检测对腺瘤癌变风险的估计具有重要意义。     

散发性结直肠癌微卫星不稳定性及其与临床病理生物学的关系

目的:探讨分析中国人散发性结直肠癌微卫星不稳定的变异及其与临床病理生物学特征的关系.方法:应用荧光多重PCR方法检测105例散发性结直肠癌初诊患者微卫星状态,分析MSI结直肠癌潜在的相关临床病理生物学特征.结果:105结直肠癌中,MSI检出率24.7%,其中MSI-H 14例(13.3%),MSI-L 12例(11.4%);队列中各位点突变率分别是D5S346(5.7%),BAT26(8.6%),BAT25(10.5%),D17S250(8.6%),D2S123(10.5%);MSI结直肠癌的组织分化程度与淋巴结转移情况与MSS结直肠癌有显著的统计学差异(P=0.047,P=0.029),但在患者年龄、肿瘤位置、病理性质无显著临床意义(P＞0.05).结论:MSI结直肠癌具有低分化癌多见,淋巴结转移少等特点,淋巴结转移少可能是MSI结直肠癌具有生存优势的原因之一.     

老年人食管鳞状上皮化生和不典型增生及腺癌序列微卫星改变

目的评估老年人食管鳞状上皮和化生-不典型增生-腺癌的微卫星变化。方法应用稀释性聚合酶链反应（PCR）方法检测存档手术切除的食管癌标本中的D2S123、D3S1616、D3S1300、BATRII、D5S346、D17S787和D18S61位点微卫星的变化。结果在非稀释DNA中，17例食管鳞状细胞癌和12例腺癌微卫星不稳定性（MSI）的频率分别是52．9％（9例）和41．7％（5例），杂合性丢失（LOH）的频率分别是23．5％（4例）和16．7％（2例），两者差异均无统计学意义（P〉0．05）。在8例食管鳞状上皮和化生-不典型增生-腺癌组织稀释DNA中，MSI和LOH频繁出现，与其非稀释DNA的结果比较，差异均有统计学意义（P〈0．05）。结论MSI和LOH在上述组织中普遍存在，它们可能是食管腺癌发生、发展的早期事件。     

遗传性非息肉病性结直肠癌的临床特征与诊断原则

目的：探讨遗传性非息肉病性结直肠癌（HNPCC）的临床特点和诊断。方法：收集22个符合Amsterdam标准的HNPCC家族，分析其临床特点。结果：本组符合Amsterdam标准的HNPCC发病率为2．6％＜22个家族有恶性肿瘤患者101例，结直肠癌患者84例，发生第一个结直肠癌的平均年龄为45．7岁，位于脾曲近侧结肠和直肠的分别占58．3％和23．8％。23．8％患者发生同时或异时多原发结直肠癌。20例患者发生肠外肿瘤，以胃癌居多。结论：HNPCC具有发病年龄早，近侧结肠多见，同时和异时多原发结直肠癌发生率高的特点，诊断治疗及随访应有别于散发性结直肠癌。本组肠外肿瘤以胃癌发生率高，与国外报道不同。建立中国人的HNPCC诊断标准是必要的。     

急性白血病p16基因微卫星不稳定性及杂和性缺失的研究

目的分析急性白血病（AL）患者p16基因连锁的微卫星不稳定性（MSI）和杂和性缺失（LOH）,了解p16基因改变与AL发生的关系。方法采用多重PCR方法检测53例AL患者骨髓及口腔黏膜细胞标本的p16基因连锁的3个微卫星位点（D9S162、D9S1748、D9S171）,观察其MSI及LOH情况。结果53例AL患者中,MSI检出率为43．4％（23／53）;位于9p21的p16基因连锁的微卫星D9S162、D9S1748、D9S171的LOH发生率分别为0（0／53）、5．7％（3／53）和9．4％（5／53）,MSI发生率分别为13．2％（7／53）、7．6％（4／53）和7．6％（4／53）。结论AL患者p16基因连锁微卫星均可检测到高频率的MSI和LOH,说明p16基因突变与AL发生、发展有关。     

遗传性非息肉结直肠癌中微卫星不稳定性的研究进展

遗传性非息肉性结直肠癌（HNPCC）是一种常染色体显性遗传病，肿瘤多发于近段结肠，并常发生肠外肿瘤。HNPCC的发生缘于错修复缺陷所致的微卫星不稳定性（MSI），MSI的状态与HNPCC的临床特征密切相关。MSI在HNPCC的基因诊断、筛查及治疗等方面具有重要的运用价值。     

肺癌癌组织标本中微卫星DNA检测及临床意义

为研究肺癌癌组织标本中微卫星DNA改变及其对肺癌的诊断价值，采用聚合酶链反应（PCR）－银染法，对43例原发性肺癌（观察组）及10例良性肺疾病患者（对照组）纤支镜活检标本的3个微卫星位点进行了检测。结果观察组微卫星不稳定（MSI）发生率47％，杂合性丢失阳性率（LOH）30％，MSI加LOH阳性率为63％；对照组未发现微卫星DNA改变。提示肺癌组织微卫星DNA检测诊断肺癌有一定价值。     

COX-1和COX-2在结直肠腺瘤中的表达

目的观察COX-1和COX-2在结直肠腺瘤中的表达情况。方法16例经病理证实的散发性结直肠腺瘤活组织检查标本，15例肠镜检查无明显病变的IBS患者肠黏膜活组织检查标本。免疫组化染色观察COX-1和COX-2表达水平的变化。结果COX-2在结直肠腺瘤组织中的表达异常增高（P〈0．05），而COX-1在正常组织和腺瘤中的表达水平没有明显的变化。结论在结直肠腺瘤组织中，COX-2表达明显升高，提示COX-2参与结直肠腺瘤的发生和发展。     

食管癌组织微卫星DNA序列不稳定性和杂合性缺失及预后的研究

目的探讨微卫星DNA序列不稳定性（MSI）和杂合性缺失（LOH）与人食管癌发生、临床病理特征及预后的关系。方法应用聚合酶链反应（PCR）和变性聚丙烯酰胺凝胶电泳技术,对30例人食管癌中MSI及LOH阳性情况进行研究,术后随访5年,了解预后。结果D3S1067位点MSI发生检出频率较高,为26.7%;D18S58位点MSI阳性率为20%。MSI的发生在食管小细胞癌中较食管鳞癌为高（P〉0.05）;MSI、LOH与肿瘤的病理分级、PTNM分期、有无区域淋巴结转移和浸润深度无关（P〉0.05）。结论食管癌在3p和18q染色体位点均存在微卫星不稳定现象;D3S1067和D18S58二个位点上MSI与食管癌的临床病理类型均相关;研究未发现这两个位点MSI、LOH与食管癌的临床分期、细胞分化程度、癌组织浸润深度和有无区域淋巴结转移等参数相关;3p位点基因的改变在食管鳞癌发生过程中具有较重要意义。     

Role of detection of microsatellite instability in Chinese with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer

AIM: To detect microsatellite instability (MSI) in patients with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer and to provide criteria for screening the kindreds with hereditary nonpolyposis colorectal cancer at molecular level. METHODS: MSI was detected in the specimens from 20 cases with HNPCC, 20 cases with ordinary hereditary colorectal cancer and 20 cases with sporadic colorectal cancer by means of polymerase chain reaction-single strand conformation polymorphism. RESULTS: The positive rate of MSI was 85% (17/20) in HNPCC group, 40% (8/20) in ordinary hereditary colorectal cancer group and 10% (2/20) in the sporadic colorectal cancer group respectively. The differences were significant. The mean ages of the three groups were 43.6, 52.2, and 61.8 years respectively, which increased gradually. The incidence of right hemicolon cancer was 64.7%, 37.5%, and 0% respectively, which decreased gradually and had significant difference. The expression ratio of BAT26 and BAT25 was 94.1% respectively, which was highest in the 5 gene sites studied. The incidence of poorly differentiated adenocarcinoma was 70.6% in HNPCC group among high frequency microsatellite instability (MSI-H), which was higher than the other two groups, which had 50% and 50% respectively. CONCLUSION: The incidence of MSI-H is higher in HNPCC group. The detection of MSI is simple and economical and has high correlation with the clinicopathologic feature of HNPCC and can be used as a screening method to detect the germ line mutation of the mismatch repair gene.     

Approaches to identification of HNPCC suspected patients in Slovak population

Patients with hereditary non-polyposis colorectal cancer (HNPCC) have a DNA mismatch repair defect (MMR) in their tumor tissue that results in instability of microsatellite DNA sequences (MSI). Thus, MSI analysis may effectively indicate this form of cancer that should be then proved by analysis of germline mutations in MMR genes. The aim of this study was to identify HNPCC suspected patients in the Slovak population by investigating microsatellite instability in colorectal tumor tissues. MSI was studied at 5-11 loci in matched tumor and normal DNA using radioactively labeled PCR products separated on sequencing gels. High microsatellite instability (MSI-H) was present only in patients younger than 50 years, in 100% of patients having two affected relatives by colorectal cancer and in 67% of patients with only one affected relative. In both groups of patients colorectal cancer was present in two successive generations. No MSI-H was found in the group of patients older than 50 years, even if they had positive family history for colorectal cancer. Among all markers used, the BAT26 mononucleotide repeat (100%), DI0S197 and D13S175 (62.5%) dinucleotide repeats were the most frequently altered in the tumor tissues. Retrospective analysis revealed that some of the patients having MSI-H tumors have had clinicopathological characteristics frequently reported to HNPCC. The family members of those patients with MSI-H are enrolled in preventive health care program until mutational analyses will enable to select carriers from non-carriers of mutated MMR genes.     

DNA microsatellite instability and mismatch repair protein loss in adenomas presenting in hereditary non-polyposis colorectal cancer

BACKGROUND AND AIM: Hereditary non-polyposis colorectal cancer (HNPCC), as its name implies, is associated with few adenomas, and the early evolution of colorectal neoplasia is poorly understood. In this study our aim was to clarify the genetic profiles of benign polyps in subjects with HNPCC using a combined molecular and immunohistochemical approach. METHODS: Thirty adenomas and 17 hyperplastic polyps were obtained from 24 affected HNPCC subjects. DNA was extracted from paraffin embedded tissue by microdissection and analysed for the presence of microsatellite instability (MSI) and mutations in five genes known to be targets in mismatch repair deficiency (TGFbetaRII, IGF2R, BAX, hMSH3, and hMSH6). Serial sections were stained by immunohistochemistry for hMLH1 and hMSH2. RESULTS: Twenty four (80%) of 30 adenomas showed MSI. Of MSI positive adenomas, 66.7% showed MSI at more than 40% of markers (high level of MSI (MSI-H)). Two of 17 hyperplastic polyps revealed MSI at one marker (low level of MSI (MSI-L)). A significant association was found between MSI-H and high grade dysplasia in adenomas (p=0.004). Eight of nine adenomas with mutations of coding sequences revealed high grade dysplasia and all nine were MSI-H. Four of the nine ranged in size from 2 to 5 mm. The presence of the hMSH6 mutation was significantly correlated with high levels of MSI (80% of markers) (p<0.02). Twenty four adenomas gave evaluable results with immunohistochemistry. One of six (17%) microsatellite stable, six of seven (86%) MSI-L, and 11 of 11 (100%) MSI-H adenomas showed loss of either hMLH1 or hMSH2. CONCLUSIONS: Most adenomas in subjects with a definite diagnosis of HNPCC show MSI (80%). The finding of MSI-L is usually associated with loss of expression of hMLH1 or hMSH2, unlike the situation in MSI-L sporadic colorectal cancer. The transition from MSI-L to MSI-H correlated with the finding of high grade dysplasia and mutation of coding sequences and may be driven by mutation of secondary mutators such as hMSH3 and hMSH6. Advanced genetic changes may be present in adenomas of minute size.     

Exon 3 beta-catenin mutations are specifically associated with colorectal carcinomas in hereditary non-polyposis colorectal cancer syndrome

BACKGROUND AND AIMS: Activating beta-catenin mutations in exon 3 have been implicated in colorectal tumorigenesis. Although reports to the contrary exist, it has been suggested that beta-catenin mutations occur more often in microsatellite unstable (MSI+) colorectal carcinomas, including hereditary non-polyposis colorectal cancer (HNPCC), as a consequence of defective DNA mismatch repair. We have analysed 337 colorectal carcinomas and adenomas, from both sporadic cases and HNPCC families, to provide an accurate assessment of beta-catenin mutation frequency in each tumour type. METHODS: Direct sequencing of exon 3 of beta-catenin. RESULTS: Mutations were rare in sporadic (1/83, 1.2%) and HNPCC adenomas (1/37, 2.7%). Most of the sporadic adenomas analysed (80%) were small (<1 cm), and our data therefore differ from a previous report of a much higher mutation frequency in small adenomas. No oncogenic beta-catenin mutations were identified in 34 MSI+ and 78 microsatellite stable (MSI-) sporadic colorectal cancers but a raised mutation frequency (8/44, 18.2%) was found in HNPCC cancers; this frequency was significantly higher than that in HNPCC adenomas (p=0.035) and in both MSI- (p<0.0001) and MSI+ (p=0.008) sporadic cancers. Mutations were more common in higher stage (Dukes' stages C and D) cancers (p=0.001). CONCLUSION: Exon 3 beta-catenin mutations are associated specifically with malignant colorectal tumours in HNPCC; mutations appear not to result directly from deficient mismatch repair. Our data provide evidence that the genetic pathways of sporadic MSI+ and HNPCC cancers may be divergent, and indicate that mutations in the HNPCC pathway of colorectal tumorigenesis may be determined by selection, not simply by hypermutation.     

Microsatellite Instability of Gastric and Colorectal Cancers as a Predictor of Synchronous Gastric or Colorectal Neoplasms

Background/Aims

Microsatellite instability (MSI) plays a crucial role in gastrointestinal carcinogenesis. The aim of this study was to clarify whether MSI is a useful marker for predicting synchronous gastric and colorectal neoplasms.

Methods

Consecutive patients who underwent both esophagogastroduodenoscopy and colonoscopy before the resection of gastric or colorectal cancers were included. MSI was analyzed using two mononucleotide and three dinucleotide markers.

Results

In total, 434 gastric cancers (372 microsatellite stability [MSS], 21 low incidence of MSI [MSI-L], and 41 high incidence of MSI [MSI-H]) and 162 colorectal cancers (138 MSS, 9 MSI-L, and 15 MSI-H) were included. Patients with MSI gastric cancer had a higher prevalence of synchronous colorectal cancer, colorectal adenoma, and gastric adenoma than those with MSS gastric cancers (4.8% vs 0.5%, p=0.023; 11.3% vs 3.2%, p=0.011; 3.2% vs 1.2%, p=0.00, respectively). The prevalence of synchronous colorectal adenomas was highest in MSI-L gastric cancers (19.0%), compared with MSI-H (7.3%) or MSS (3.2%) gastric cancers (p=0.002). In addition, there were no significant differences in the prevalence rates of synchronous colorectal adenoma among the MSI-H (13.3%), MSI-L (11.1%), and MSS (12.3%) colorectal cancers (p=0.987).

Conclusions

The presence of MSI in gastric cancer may be a predictor of synchronous gastric and colorectal neoplasms, whereas MSI in colorectal cancer is not a predictor of synchronous colorectal adenoma.     

Microsatellite instability in sporadic and inherited colon adenocarcinomas from Greek patients: correlation with several clinicopathological characteristics

BACKGROUND AND AIMS: Microsatellite instability seems to play a significant role in colorectal carcinogenesis, as it is reported to occur in HNPCC patients as well as in a proportion of sporadic cases. The aim of this study was to examine the presence of microsatellite instability in relation to other commonly observed genetic abnormalities and clinicopathological characteristics of sporadic and inherited colorectal cancers. METHODOLOGY: One hundred and three sporadic colorectal adenocarcinomas and 9 adenocarcinomas from HNPCC patients were histologically evaluated. The presence of microsatellite instability was investigated at six loci. K-ras and p53 mutations, p53 LOH, hMLH1 expression and methylation status were examined as well. Statistical analysis was performed to define possible correlations of the observed genetic alterations with the clinicopathological characteristics of the analysed tumors. RESULTS: High-grade microsatellite instability was found in 14% of sporadic adenocarcinomas and in 78% of adenocarcinomas from HNPCC patients. K-ras and p53 mutations were found in 29% and 28% of sporadic adenocarcinomas respectively and in 0% and 22% of the 9 HNPCC cases. A statistically significant correlation was noticed in sporadic tumors between the presence of MSI-H and tumor location at the proximal colon, as well as with the female gender. CONCLUSIONS: Sporadic MSI+ colon adenocarcinomas seem to represent a distinct entity with a unique profile of genetic changes, different from those observed in HNPCC or MSI negative sporadic tumors.     

遗传性非息肉病性结直肠癌的微卫星不稳定研究

目的　探讨国人北方人群HNPCC的微卫星不稳定 (microsatelliteinstability ,MSI)发生情况及其意义。方法　 44例患者来源于 3 0个HNPCC (hereditarynonpolyposiscolorectalcancer)家系 ,这些家系主要分布于北方 5省市。所有患者均符合BGl 3 (Bethes dal 3 )HNPCC诊断标准。以荧光标记法检测 44例患者的石蜡包埋组织微卫星稳定性。结果　 44例患者中高度微卫星不稳定 (highfrequencymicrosatelliteinstability ,MSI H)为 81.81( 3 6/ 44 ) ,低度微卫星不稳定 (lowfrequencymicrosatelliteinstability ,MSI L)为 6.82 ( 3 / 44 ) ,微卫星稳定 (microsatellitestable ,MSS)为 11.3 ( 5 / 44 ) ;所选择的 5个微卫星位点中Bat2 5和Bat2 62个位点MSI H的表达率较高 ,分别为 10 0 %和 97.2 2 %。符合AmsterdamⅡ和符合BGl 3标准的HNPCC患者的MSI H表达率分别为 85 .2 9%和 81,81% ,仅符合BGl 3标准 ,而不符合AmsterdamII的 10个患者中 ,7个发现MSI H。结论　HNPCC肿瘤的MSI H发生率高 ,MSI检测方法简便、易行 ,可作为错配修复基因种系突变初筛方法 ,Bethesdal 3标准可更多地收集到可疑的HNPCC患者     

Low rate of microsatellite instability in young patients with adenomas: reassessing the Bethesda guidelines

BACKGROUND AND AIM: Screening adenomas for microsatellite instability (MSI) in patients younger than 40 yr of age has been recommended by the Bethesda Guidelines as a means of identifying patients at risk for hereditary nonpolyposis colorectal cancer (HNPCC). We sought to determine the rate of MSI in adenomas removed from individuals under 40 yr of age over a 5-yr period in a university general gastroenterology practice. METHODS: We identified patients between 18 and 39 yr of age with endoscopically removed adenomatous colorectal polyps. Patients with polyposis syndromes, inflammatory bowel disease, or colorectal carcinoma were excluded. A three-generation family history was obtained via telephone interview. Endoscopic and histology reports were reviewed. Adenomas were tested for MSI using the BAT26 and BAT40 microsatellite markers, and expression of the MSH2 and MLH1 proteins was assessed by immunostaining. RESULTS: A total of 34 patients had 46 adenomas removed endoscopically. Out of 34 patients, 14 (41%) had a family history of colorectal cancer and 3 were from Amsterdam criteria positive families. A total of 28 of 46 adenomas (61%) were distal to the splenic flexure. Polyps ranged in size from 2 to 20 mm and averaged 6.6 mm. Five polyps (11%) were tubulovillous adenomas, and the remainder were tubular adenomas. None of the polyps were serrated adenomas and none demonstrated high-grade dysplasia. Among the 40 adenomas available for testing, none demonstrated MSI using either BAT26 (0/40) or BAT40 (0/21), nor did any of the polyps tested demonstrate loss of either MSH2 or MLH1 expression (0/16). CONCLUSION: Screening adenomas from patients younger than 40 yr of age for MSI was ineffective in identifying potentially new cases of HNPCC. New strategies that improve on the current clinical and molecular screening methods should be developed so that at-risk individuals can be identified and referred for germline testing before developing their first cancer.     

MSI is frequently recognized among gastric cancer patients with a family history of cancer

BACKGROUND/AIMS: A family history of cancer raises the risk of gastric cancer. Microsatellite instability (MSI) is frequently observed in hereditary non-polyposis colorectal cancer (HNPCC), and gastric cancer is the most frequent extra-colonic cancer among HNPCC patients. The relationship between gastric cancer and MSI is controversial. The purpose of this study was to identify the relationship between MSI incidence and gastric cancer in patients with a family history of cancer. METHODOLOGY: MSI incidence was examined at 5 microsatellite loci and hMLH1 and hMSH2 protein expression was examined by immunohistochemical analysis in 30 gastric cancer patients with family histories of cancer (familial group) and 37 gastric cancer patients without any family history of cancer (sporadic group). RESULTS: The incidence of high-frequency MSI (MSI-H) in the familial group was 33.3% (10/30) and in the sporadic group it was 5.4% (2/37) (p < 0.05). The incidence of lack of at least one mismatch repair (MMR) protein was 66.7% (8/12) in MSI-H cases, which was significantly higher than in low-frequency MSI (MSI-L) cases and microsatellite stable (MSS) cases. CONCLUSIONS: MSI may play an important role in the development of gastric cancer in individuals with a family history of cancer and it is induced by a deficiency in MMR protein expression.