Usefulness of Immunohistochemistry for Microsatellite Instability Screening in Gastric Cancer

BACKGROUND/AIMS: The usefulness of immunohistochemistry to screen for the microsatellite instability (MSI) phenotype in gastric cancer remains unclear. Moreover, the prognostic value of MSI phenotypes in gastric cancer has been debated. METHODS: The clinicopathologic parameters and survival outcomes of 203 MSI-high (MSI-H) and 261 microsatellite-stable (MSS) advanced gastric cancers (AGCs) were compared. Next, we compared the immunohistochemistry results for hMLH1 and hMSH2 with those of a polymerase chain reaction (PCR)-based method. Kaplan-Meier curves and a Cox proportional hazard regression model were used to conduct survival analyses. RESULTS: The MSI-H AGCs were correlated with older age (p<0.001), female gender (p=0.018), distal location (p<0.001), larger size (p=0.016), and intestinal type (p<0.001). Multivariate analysis revealed that the MSI-H phenotype was an independent favorable factor that was related to overall survival in patients with AGC (p<0.001). Compared with the PCR-based analysis, immunohistochemistry exhibited high sensitivity (91.1%) and specificity (98.5%) in the detection of MSI phenotypes. CONCLUSIONS: MSI-H gastric cancers have distinct clinicopathologic features and better prognoses, which suggests the necessity of MSI analysis in gastric cancer. Immunohistochemistry can be a useful and reliable screening method in the assessment of MSI status in gastric cancer.

Expression and clinical significance of hMLH-1 and hMSH-2 in Han and Uygur in Xinjiang area of sporadic colorectal carcinoma / 临床与实验病理学杂志

Purpose To detect the incidence rate, average age and the expression of hMLH-1 and hMSH-2 of sporadic colorectal carci-noma ( SCC) with Han and Uygur patients. Methods The expression of hMLH-1 and hMSH-2 was detected in SCC for 60 cases of Uygur and 196 cases of Han by immunohistochemical method, including 60 Uygur and Han cases normal colorectal mucosa ( NCM) . Results The positive rate of hMLH-1 and hMSH-2 proteins expression in the NCM was 100%. There was a marked difference in the positive rate of hMLH-1 in SCC between Han (93. 4%, 183/196)and Uygur (75%, 45/60) (P0. 05). The average age of Han and Uygur SCC patients were 65. 64 years, 57. 63 years, respectively, and Uygur SCC cases were more likely to be diagnosed at less 40 years old (P<0. 05). The positive rate of hMLH-1 and hMSH-2 expression in the tubular adenoma was 100%. The positive rate of hMLH-1 and hMSH-2 expression in the tubulovillous adenoma in Uygur and Han were 66. 7%( 2/3 ) and 66. 7%( 2/3 ) , and 74. 2%(23/31) and 90. 3%(28/31), respectively, significantly lower than those of tubular adenoma (P<0. 05). The expression of hMLH-1 was positively correlated with that of hMSH-2 in SCC in Han(rs =0. 737, P<0. 05). The expression of hMLH-1 was positive-ly correlated with that of hMSH-2 in SCC in Uygur(rs =0. 383, P<0. 05). There exists marked difference in the positive rate of hM-LH-1 and hMSH-2 among difference age groups (P<0. 05). Conclusion There is a certain loss of hMLH-1 and hMSH-2 expression in SCC in Han and Uygur Chinese, which is related to adenoma and age. The expression of hMLH-1 in SCC tissue among Uygur pa-tients is not resemble to those of Han patients. The average age of Uygur SCC patients is younger than Han, and the positive rate of hMLH-1 is higher. Combined detection of hMLH-1 and hMSH-2 proteins may be used for judging the severity and prognosis of SCC in Xinjiang, which helps improve patients’ treatment program and rationalize their choices.

Expression of hMLH1 and hMSH2 in suspected hereditary non-polyposis colorectal cancer / 实用医学杂志

Objective To analyse the suspected hereditary non-polyposis colorectal cancer (HNPCC) in mismatch repair protein (MMR) expression of hMLH1 and hMSH2. Methods Immunohistochemical staining method was used for the detection of hMLH1 and hMSH2 protein expression in 193 cases suspected HNPCC patients, the deletion of MMR proteins was identified as highly suspected HNPCC cases. Results Of the 193 patients with suspected HNPCC hMLH1/hMSH2 abnormal expression rate was 29.02%; ≤30 years old was 40%, 31 ~ 40 years old was 28.05%, 41 ~ 50 years old was 28.71%,3 suspected HNPCC showed the deletion of hMLH1/hMSH2 protein expression at the same time ,; In the right colon , the left half colon and rectal anomaly detection rates were 40.74%, 32.65%and 18.89%; hMLH1/hMSH2 deletion was 46.15%with family history. Conclusions The deletion of MMR protein is closely related to age,site and family history in suspected HNPCC, and the deletion of hMLH1 is an important factor to induce early-set colorectal cancer. The deletion of hMLH1/hMSH2 at the same time indicates that hMLH1/hMSH2 genes may play important role in the incidence of HNPCC.

The study on the relationship between methylation of MGMT, hMSH2 gene promoters and protein ex-pression in glioma patients / 实用肿瘤学杂志

Objective To investigate the relevance between protein expression and methylation of MG-MT and hMSH2 in glioma patimts.Methods Immunohistochemical and methylation specific PCR were adopted respectively to test on 275 cases of glioma patients for the protein expression and methylation situation of MGMT and hMSH2.Results The negative protein expression rate of MGMT and hMSH 2 in the tissue of brain golima were 47.2% and 62.5% respectively;the occurrence of methylation in gene promoter region were accordingly 41.8% and 22.4%.Statistical analysis revealed that MGMT promoter methylation in peripheral blood gene groups was related with the protein negative expression of tumor tissue (P0.05).Conclusion The meth-ylation of MGMT is a common molecular situation in the generation of brain glioma ,which may be connected with that of tumor.However,hMSH2 promoter methylation might not the main reason for inactivation of hMSH 2 pro-tein,there may be other important factors affecting its expression .

Expression of mismatch repair genes hMLH1 and hMSH2 and their significance in patients with colorectal carcinoma / 中国肿瘤临床

10.3969/j.issn.1000-8179.2013.12.007

Implication of DNA repair genes in prostate tumourigenesis in Indian males.

Background & objectives: Prostate cancer (CaP) is the fifth most common cancer among Indian men. Tumour protein p53 (TP53) gene increases the fidelity of DNA replication and homologous recombination by transcriptional transactivation of mismatch repair (MMR) genes. DNA repair thus has a potential role in molecular carcinogenesis of CaP. The aim of the present study was to identify mutations, and polymorphisms in TP53 gene and MMR protein expression in CaP in Indian male population. Methods: TP53 codon 72 polymorphism was analysed in 105 CaP, 120 benign prostatic hyperplasia (BPH) cases and 106 normal controls. Mutational analysis of TP53 was done in DNA extracted from formalin fixed paraffin embedded tissue of 80 CaP and 24 BPH cases. Expression of MMR proteins viz. hMLH1, hMSH2, hPMS1 and hPMS2 was studied in 80 CaP, 15 prostatic intraepithelial neoplasia (PIN) and 15 BPH cases. Results: A somatic C/A variation at the intronic boundary of exon 7 in TP53 gene was observed in one each biopsy samples from CaP and BPH. A significant association of codon 72 TP53 Pro/Pro genotype was observed with the risk of CaP (OR, 2.59, P=0.02) and BPH (OR, 6.27, P<0.001). Immunohistochemical analysis of MMR proteins showed maximum loss of hPMS1 expression in cases of CaP and PIN while no loss in expression of MMR proteins was observed in BPH cases. The study also identified a significant loss of hPMS2 protein in poorly differentiated tumours (Gleason score >7) than in well differentiated tumours (Gleason score 3-6) (P<0.05). Interpretation & conclusions: The results of the present study demonstrate that TP53 codon 72 polymorphism plays significant role in the pathogenesis and susceptibility to CaP and BPH. Also, an aberrant MMR protein expression could be involved in progression of prostate cancer through PIN, early CaP to aggressive CaP. The loss of hPMS2 protein expression may serve as a marker for progression of CaP.

Expression and clinical implications of hMSH2 gene in sporadic insnlinomns / 中华胰腺病杂志

Objective To investigate the role of hMSH2 in the pathogenesis of sporadic insulinomas and to determine whether the expression of hMSH2 could be used to differentiate benign sporadic insulinomas from malignant ones. Methods Fifty-five sporadic insulinomas (40 benign and 15 malignant tumors) resected from 50 patients were obtained. Expression of hMSH2 was detected by immunohistochemistry staining. DNA was obtained from micradissected tissue. Loss of heterozygnsity (LOH) of hMSH2 gene was detected by PCR-LOH. 6 microsatellite markers were selected on 3 chromosomes, and microsatellite instability (MSI) status of tumor tissue were detected by PCR. The findings were analyzed in relation to the clinicopathological characteristics. Results Down-regulation of hMSH2 expression was found in 13% of 55 sporadic insulinomas. LOH of the hMSH2 gene was not present in 55 insulinomas. High frequency MSI (MSI-H, MSI occurred in at least 2 out of 6 sites) was present in 36% (20/55) of all the insulinomas. Down-regulation of hMSH2 expression was found in 33% of the 15 malignant tumors, while it was 5% in benign tumors (P < 0. 05). Conclusions Down-regulation of mismatch repair gene hMSH2 may be correlated with the degree of tumor malignancy. The expression of hMSH2 could be used as a potential marker for distinguishing benign insulinoma from malignant ones.

Expression of hMLH1 and hMSH2 in hilar cholangiocarcinoma and its significance / 中华肝胆外科杂志

Objective To investigate the expression of hMLH1 and hMSH2 in hilar cholangiocarcinoma and its relation to clinical features and prognosis of the tumor.Methods The expression of hMLH1 and hMSH2 was determined with immunohistochemistry in 54 specimens of hilar cholangiocarcinoma and 25 of normal bile duct tissue.Lahoratory data were then analyzed statistically together with the related clinicopathological data.Results 1)hMLH1 and hMSH2 were expressed in 24 and 21 out of the 54 cases of hilar cholangiocarcinoma(44.4%,38.9%)and 23 and 21 of the 25 normal cases(92%,84%),respectively(P＜0.05).2)The expression of hMLH1 and hMSH2 in hilar cholangiocarcinoma had no association with the age,gender,tumor size and Bismuth type(P＞0.05)but close relation to lymph node metastasis and pathological changes(P＜0.05).3)The 2-year survival rate was markedly lower in hMLH1-negative patients than in hMLH1-and hMSH2-positive ones (15%vs.45.4%,23.5%vs.44%,P＜0.05).Conclusions Joint action of hMLH1 and hMSH2plays an important role in the oncogenesis and metastasis of hilar cholangiocarcinoma.These two may be valuble factors to indicate prognosis of the tumor.

Analysis of Microsatellite Instability in Ovarian Epithelial Cancer

BACKGROUND: The aim of this study was to clarify the incidence and role of microsatellite instability (MSI) in sporadic ovarian epithelial cancers (OEC). We investigated the MSI status and mismatch repair (MMR) protein expression in OEC. METHODS: MSI was examined by fluorescence- based polymerase chain reaction using five NCI panel markers (BAT25, BAT26, D2S123, D5S346 and D17S250) in 46 cases of OEC. Immunohistochemistry (IHC) for hMLH1 and hMSH2 was performed. RESULTS: Seven cases (15.2%) exhibited high-frequency MSI (MSIH), one exhibited low-frequency MSI (MSI-L), and the remaining 38 demonstrated microsatellite stability (MSS). MSI-H in OEC was not associated with histologic grade, FIGO stage, tumor size, mitoses or histologic type. Loss of expression of either hMLH1 or hMSH2 was observed in 4 of the 7 (59.3%) MSI-H cases, whereas 4 of the 39 (10.3%) MSI-L or MSS tumors revealed loss of expression of MMR proteins. The sensitivity and specificity of immunohistochemistry for hMLH1 and hMSH2 were 57.1% and 89.7%. CONCLUSIONS: Our data suggest that a genetic defect in the MMR system might play a role in the carcinogenesis of a minor subset of sporadic OEC however, immunohistochemical testing for hMLH1 and hMSH2 cannot accurately determine microsatellite instability status in OEC.

Efficacy of hMLH1/hMSH2 Immunohistochemical Staining as Representative Index for Microsatellite Instability Status in Sporadic Colorectal Cancer

PURPOSE: Sporadic colorectal cancer with micosatellite instability (MSI) is supposed to have a distinct molecular profile, distinct clinocopathologic feature, and a distinct prognosis. However, the test for MSI is still expensive, and a big machine is needed for routine screening. This study was performed to examine the clinicopathologic of characteristics of MSI sporadic colorectal cancer and the efficacy of immunohistochemical staining for hMLH1 and hMSH2. METHODS: Five hundred sixty nine colorectal adenocarinomas resected from September 2003 to August 2004 at Asan Medical Center were prospectively collected. FAP (familial adenomatous polyposis), HNPCC (hereditary non-polyposis colo-rectal cancer), and incomplete tests of immunohistochemical staining or MSI were excluded. The MSI status was determined by using PCR (polymerase chain reaction). A first round of immunohistochemical staining for hMLH1/hMSH2 was performed, and a second round was performed for cases showing a disparity between the two exams. The clinicopathologic variables regarding the MSI status were analyzed, and the sensitivity and the specificity of immunohistochemical staining were evaluated. RESULTS: Sporadic colorectal cancers with MSI-H were 8.4% (n=48) and were associated with age (< or = 60 years), colorectal cancer familial history, synchronous colorectal cancer, right side tumor location, and poorly differentiated or mucinous cell type. However, age, synchronous colorectal cancer, and right side tumor location were associated an the multivariate analysis. In the first round of immunohistochemical staining, no expression of hMLH1 and/or hMSH2 was obserred in 71 cases (12.5%), and the sensitivity and the specificity were 50.0% and 91.9%, respectively. After repetitive immunohistochemical staining for the 71 cases showing disagreement with the to MSI status, the sensitivity and the specificity of the second round of immunohistochemical staining were 53.3% and 97.6%, respectively. CONCLUSIONS: Sporadic colorectal cancer with MSI appears to have distinct characteristics. However, immunohistochemical staining for hMLH1 and hMSH2 is not accurate enough to be used instead of MSI.

Microsatellite Instability and Mismatch Repair Protein (hMLH1, hMSH2) Expression in Intrahepatic Cholangiocarcinoma

BACKGROUND: To clarify the role of the mismatch repair (MMR) system in the carcinogenesis of intrahepatic cholangiocarcinoma (ICC), we investigated the microsatellite instability (MSI) status and MMR protein expression in ICC. METHODS: Thirty-six cases of ICCs were examined by microsatellite analysis for 55 markers that encompassed all of the chromosomal arms and BAT26. An immunohistochemical study for hMLH1 and hMSH2 was also performed. RESULTS: Widespread MSI (MSI-H) accompanied with a loss of hMLH1 expression was found in one case (2.8%). This MSI-H case was an adenosquamous carcinoma showing intraductal tubulopapillary adenocarcinoma and invasive adenosquamous carcinoma component. Loss of hMLH1 was noted in both components while the frequency and shifted band patterns of MSI were not identical between the components. Another 10 ICCs (27.8%) revealed low level MSI with preserved MMR gene expression. CONCLUSIONS: Our data suggested that a genetic defect in the MMR system and MSI is not a major pathway in the carcinogenesis of ICC.

Responsiveness of CPT-11 in Respect to hMLH1 and hMSH2 Protein Expression in the Primary Colorectal Cancer / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The aim of this study was to evaluate the responsiveness to CPT-11 with respect to hMLH1 and hMSH2 protein expressions in primary colorectal tumors. MATERIAL AND METHODS: 91 patients with colorectal cancer treated having undergone surgery and postoperative CPT-11-based adjuvant chemotherapy, between 1997 and 2002, were prospectively recruited. Tumor samples were immunohistochemically analyzed for the expressions of hMLH1, hMSH2, p53 and CEA proteins. RESULTS: Of the 91 tumors, 6 (6.6%) and 4 (4.4%) showed loss of hMLH1 and hMSH2 protein expressions, respectively. The response rate of patients with tumors not expressing either hMLH1 or hMSH2 was higher than that of those expressing either of these proteins (p=0.026). Patients with tumors not expressing hMLH1 showed a significantly better response to CPT-11 (p=0.04). The responsiveness was not associated with the expressions of hMSH2, p53 or CEA. There were no correlations between drug toxicity and the expressions of hMLH1, hMSH2 or p53. The overall survival was better in patients responsive to CPT-11-based chemotherapy compared to non-responders. CONCLUSION: The immunohistochemical determination of loss of hMLH1 and hMSH2 expressions may be used in determining the responsiveness to CPT-11-based chemotherapy. Our results suggest that hMLH1 protein expression may be a predictor for CPT-11 responsiveness in patients with colorectal cancer.

Etiological role of polymorphism IVS+9C→G in hMSH2 gene in gastric cancers / 医学研究生学报

Objective: To investigate the etiological role of polymorphism IVS1+9C→G in hMSH2 gene in gastric cancers. Methods: A case-control study has been taken on subjects included 72 sporadic gastric, 71 familial gastric cancers and 126 healthy individual controls. Genomic DNA was extracted from peripheral white cell of all subjects. The polymorphism was detected by a PCR-based DHPLC analysis and verified by DNA sequencing. Results: The polymorphism IVS1+9C→G in hMSH2 gene was detected in 33.3%(42/126) Healthy individuals, 40.3%((29/72 ))sporadic gastric and 43.7%(31/71 )familial gastric cancers. Significant difference existed between cancers at young age (

Detection of hMSH2 gene mutations in gynecologic tumor population by multiple PCR-SSCP / 中国癌症杂志

Purpose:To set up a new method to screen hMSH2 gene mutations, to detect hMSH2 gene mutations in gynecologic tumor population and to find molecular biomarkers of tumor. Methods:The basic data and blood samples from 42 gynecologic tumor patients werre collected. The genetic mutations of the sixth exon and seventh exon of hMSH2 gene were investigated by multiple polymerase chain reaction single strand conformation polymorphism (PCR SSCP),followed by DNA sequencing. Results:The successes in setting up the multiple PCR SSCP method made it possible to detect hMSH2 gene mutations more quickly and more economically. Two samples of the seventh exon mutation was detected in the tumor population. The mutation is Leu→Phe missense mutation. No mutation of the sixth exon was detected by SSCP.Conclusions:The multiple PCR SSCP method is effective in detecting genetic mutations. There is a mutation site in the seventh exon of hMSH2 gene. It is probably a biomarker of gynecologic tumor. This discovery might offer the basis for further investigation of mutations in large amount population and studies of the function of the mutation.

The expression of P53,K-ras and hMSH2 in ulcerative colitis-associated colorectal cancer / 中华消化杂志

0.05). The positive rate of MSI in UC with dysplasia was significantly higher than that in UC (P0.05). The loss of hMSH2 protein expression was not found in UC with dysplasia and UCACRC. Conclusions Both the mutations of P53, K-ras genes and MSI are early events in UCACRC. There is no relationship between MSI and loss of hMSH2 protein expression in (UCACRC).

Detection of hMLH1/hMSH2 expression for identifying patients with hereditary nonpolyposis colorectal carcinoma / 中华消化杂志

Objective To evaluate the significance of expression of hMLH1 and hMSH2 in detecting hereditary nonpolyposis colorectal carcinoma (HNPCC). Methods Colorectal carcinomas from 66 patients were examined by immunohistochemistry for the expressions of hMLH1 and hMSH2 using commercially available monoclonal antibodies. Immunohistochemical patterns of tumors from 19 HNPCC patients (Group A), 20 suspected HNPCC patients (Group B), 14 patients whose clinical features conformed to the Bethesda guideline (Group C), and 13 sporadic colorectal cancer patients (Group D) were compared. Results The absence or low expression of hMLH1 and hMSH2 was revealed in 72.8% patients of group A, 60.0% in group B, 28.4% in group C and 7.7% in group D. The absence or low protein expression of hMLH1 and hMSH2 was significantly correlated with HNPCC (P=0.0008). The absence or low expression of hMLH1 was higher detection rate than that hMSH2 (P=0.01). Conclusions HNPCC patients can be identified by immunohistochemical methods according to the expression of hMLH1 and hMSH2, which may be used in clinical practice and research. Immunohistochemical analysis of hMLH1 and hMSH2 may predict the presence of corresponding gene mutations. Gene mutation in hMLH1 might be higher than that in hMSH2 in Chinese HNPCC.

hMLH1/hMSH2 Protein Expression in Sporadic Colorectal Carcinoma and Its Clinicopathological Significance

PURPOSE: DNA replication errors (RERs) in repeated nucleotide sequences (microsatellite instability) is caused by defective mismatch repair (MMR) genes. Ninety percent of colorectal carcinomas in hereditary nonpolyposis colorectal cancer (HNPCC) patients and 10-15% of sporadic colorectal cancers show microsatellite instability. In the majority of colorectal cancers with microsatellite instability, the defective MMR gene is hMLH1 or hMSH2. The author examined immunohistochemical expression of hMLH1 and hMSH2 in 75 cases of colorectal carcinomas excluding HNPCC, based on Amsterdam criteria for investigating clinicopathological characteristics and prognosis in hMLH1/hMSH2 negative cases. METHODS: Formalin fixed, paraffin blocks obtained from tumors of 75 cases of colorectal cancers were stained with two monoclonal antibodies (hMLH1 and hMSH2). The correlation between hMLH1/hMSH2 negativity, and clinicopathological feature and prognosis were statistically analysed. RESULTS: Twelve cases (16.0%) showed hMLH1/hMSH2 negativity. Negative expression of hMLH1/hMSH2 was associated with early onset (under age 50), proximal location, multiplicity, mucinous histologic type and poor differentiation. There was a significant survival advantage in patients with hMLH1/hMSH2 negative colorectal carcinoma. CONCLUSIONS: This study shows that hMLH1/hMSH2 negative colorectal carcinomas have the same clinicopathological characteristics of colorectal carcinomas with microsatellite instability. The immunohistochemical test for hMLH1/hMSH2 protein can be a simple screening method routinely applicable. The result of this test is available for establishing guidelines for management, and an independent prognostic factor for sporadic colorectal cancers.

Study on genetic instability of nm23-H1 gene and expression of hMLH1, hMSH2 in sporadic gallbladder carcinoma / 中国病理生理杂志

AIM: To examine the MSI and LOH of locus D17S396 and their influence on the expression of nm23-H1 in gallbladder tumors, and to examine the protein expression of hMLH1/hMSH2, which may provide experimental evidence for the tumor occurrence and metastasis. METHODS: Techniques such as DNA extraction, CR-SSCP, ordinary silver stain were used to study MSI and LOH of locus D17S396. Envision IHC was used to assess the expression of nm23-H1 and hMLH1/hMSH2.RESULTS: ① The frequency of heredity instability of gallbladder carcinoma was 42.55%. The frequency of LOH in liver and lymph node metastasis cases and in stage Nevin IV and V was significantly higher than that without metastasis and stage I, II and III. However, the frequency of MSI showed contrary correlation with some clinicopathologic characteristics. ② The expression of nm23-H1 was 46.81%. The case with lymph node metastasis and Nevin stage IV and V showed significantly lower expression than that without lymph node metastasis and stage I, II and III. ③ The expressions of hMLH1 and hMSH2 were 51.06% and 42.55% respectively. hMLH1 in lymph node and liver metastasis cases and in stage Nevin IV and V were significantly lower than that without metastasis and in stage I, II and III. ④ Positive frequency of hMLH1 in MSI positive group was higher than that in MSI negative group. The positive frequency of nm23-H1 and hMSH2 protein in LOH positive group was lower than that in negative group.CONCLUSION: The heredity instability of nm23-H1 gene may be implicated pathogenesis and progression of gallbladder carcinoma. Both MSI and LOH of nm23-H1 control the development of gallbladder carcinoma independently in different paths. Abnormal expression of hMLH1/hMSH2 may be a molecule marker in early stage of gallbladder carcinoma.

Microsatellite Instability and hMSH2 Gene Mutations in Sporadic Colorectal Cancers

Microsatellites are short nucleotide repeat sequences present throughout the human genome. Alterations of microsatellites, comprising extra or missing copies of these se quences, have been termed microsatellite instability(MSI, genetic instability, replication errors, RER(+) phenotype). To date, at least four genes involved in DNA mismatch repair, hMSH2, hMLH1, hPMS1 and hPMS2, are thought to account for the observation of microsatellite instability in tumor from Hereditary nonpolyposis colorectal cancer (HNPCC) patients. The genetic defect responsible for the MIN+ phenotype in sporadic colorectal cancer, however, has yet to be clearly delineated. The purpose of this study was to determine the presence of MSI in sporadic cancer and to correlate its occurrence with clinicopathological parameters, we have studied six microsatellite loci by use of polymerase chain reaction amplification and denaturing polyacrylamide gel electrophoresis. We found that 20%(9 of 46 cases) sporadic colorectal cancers showed RER at two or several loci(RER+). Microsatellite instability was associated with location of the tumor in the proximal colon 66%(6 of 9 cases) and with poorly differentiated tumor phenotype 56%(5 of 9 cases). In order to better understand the role of somatic alterations within hMSH2 in the process of colorectal tumorigenesis, we examined the most conserved regions(codon 598~789) of this gene in nine patients with MIN spotadic colorectal cancer. 6 patient of RER(+) colorectal ca. patients had a polymorphism which was a T to C base change in the intron sequence at -6 position of the splice acceptor site at the 5'end of exon 13. This particular sequence variation is a polymorphism rather than a mutation which increase cancer susceptability. These data suggest that the genetic instability is detect ed in some colorectal cancers and play an important role in the pathogenesis of sporadic colorectal cancer.

Expression of hMSH2, hMLH1 Protein in Sporadic Colorectal Cancer and Corresponding Normal Tissue

PURPOSE: DNA mismatch repair gene is responsible for hereditary nonpolyposis colorectal cancer. But it is not well known its role in sporadic colorectal cancer patients. We analysed normal hMSH2, hMLH1 protein expression in colorectal adenocarcinoma tissues and corresponding normal tissues to find out the role of mismatch repair gene in sporadic colorectal cancer by Western blotting. METHODS: Normal hMSH2 and hMLH1 protein expression was studied on 25 colorectal cancer and corresponding normal tissue by Western blot with hMSH2 and hMLH1 monoclonal antibody. Normal protein band was expressed on 100 kD in hMSH2 and 87 kD in hMLH1. SW480 and LoVo cell line was used as positive and negative control for hMSH2 and LoVo and SW480 as positive and negative for hMLH1. And we analysed the relation between the hMSH2, hMLH1 protein expression and clinicopathological parameters. RESULTS: It was 2 cases (8%) that both hMSH2 and hMLH1 protein expression was not observed. Three cases (12%) were negative for hMSH2 and 2 cases (8%) for hMLH1. One or both hMSH2, hMLH1 protein expression was not observed in 7 cases (28%) in total. There was no correlation for proximal occurrence (25% vs 35%), young age (37.5% vs 23.5%) and lymph node metastasis (50% vs 47%). But poorly and mucinous differentiation was regarded as having relation with negative expression of hMSH2 and hMLH1 (50% vs 17.6%) but not significant statistically. CONCLUSION: Sporadic colorectal cancer with negative expression of normal hMSH2 and hMLH1 protein showed no relation to younger age, proximal site preference and lymph node metastasis. But it was suggested that mismatch repair gene protein was involved in cancer cell differentiation in sporadic colorectal cancer.