Immunohistochemical detection of mismatch repair gene proteins as a useful tool for the identification of colorectal carcinoma with the mutator phenotype

Evaluation of the preventive potential of graded dietary inclusion of Hyphaene thebaica (Linn) fruit in rat model of colon carcinogenesis

The preventive effect of Hyphaene thebaica fruit in colon carcinogenesis was evaluated in Wistar rats at 0, 2.5, 5 and 10% inclusion rates for twelve weeks with concomitant 72-h intra-rectal N-methyl-N-nitrosourea (MNU) instillations. Indices of antioxidant status and carcinogenesis were analyzed using spectrophotometric, ELISA, histological and immunohistochemical techniques. The fruit protected against lipid peroxidation and level of early biomarkers of colon carcinogenesis, accompanied by decrease in some endogenous antioxidant enzymes functionality. It also prevented colon tissues against MNU-induced severe inflammations and damage to the mutL-homolog 1 (MLH1) gene. There was significant negative correlation between endogenous antioxidant enzyme activities and carcinoembryonic antigen (CEA) as well as lipid peroxidation, but relationship between total polyphenols and percentage expression of MLH1 proteins as well as endogenous antioxidant enzyme activities was positive. These results validate the folkloric use of H. thebaica fruit in the management of colorectal disorders. PRACTICAL APPLICATIONS: Hyphaene thebaica fruit which is widely consumed in northern Nigeria and other countries of sub-Saharan Africa is rich in fiber and antioxidant polyphenols. These two classes of compounds have demonstrated capacity to prevent colorectal cancer and cancer of other sites. Therefore, the validated protective Hyphaene thebaica fruit suggests that it can be processed for inclusion in beverages/diets as functional foods for prevention and management of colorectal disorders.

Low prevalence of biliary tract cancer with defective mismatch repair genes in a Japanese hospital-based population

Recent studies have reported that immune checkpoint inhibitors are effective against various defective mismatch repair (dMMR)/microsatellite instability-high (MSI-H) cancers. A limited number of reports are available on the frequency of dMMR/MSI-H carcinoma in biliary tract cancer (BTC), describing its clinicopathological characteristics and prognosis. The latter carcinoma is also associated with Lynch syndrome (LS). The present study was performed to investigate the frequency of patients with dMMR/MSI-H in BTC and the clinical characteristics of BTC with dMMR/MSI-H in a single institution in Japan. A total of 116 patients with BTC who underwent curative surgical resection at Kagawa University Hospital between January 2008 and December 2017 were included. The protein expression levels of the mismatch repair (MMR) genes [mutL homolog 1 (MLH1), mismatch repair endonuclease PMS2 (PMS2), MutS homolog (MSH)2 and MSH6] were assessed by immunohistochemistry (IHC) using formalin-fixed paraffin-embedded tissue specimens. Subsequently, MSI testing was performed on patients who exhibited loss of MMR protein expression. Loss of expression of one or more proteins was detected in five cases (4.3%). Loss of MLH1/PMS2 expression was observed in one case of intrahepatic cholangiocarcinoma, whereas loss of PMS2 expression was noted in one case of perihilar cholangiocarcinoma. Loss of MSH2/MSH6 and MSH6 expression was noted in two cases of distal cholangiocarcinoma and loss of PMS2 expression in one case of ampullary carcinoma. Out of the five patients, two demonstrated MSI-H. Microsatellite stability was observed in two cases and for one case, no data were available. Two MSI-H cases were patients with loss of expression of MLH1/PMS2 and MSH2/MSH6. None of the five patients exhibited a past medical history or family history of suspected LS. The frequency of dMMR in BTC was ~5%, which was similar to that reported by similar studies performed in other countries. In the present study, IHC appeared to be more useful than MSI testing for detecting MMR abnormalities with regards to the detection rate. Furthermore, there may only be a limited number of patients with BTCs who are likely to benefit from the therapeutic effects of treatment with immune checkpoint inhibitors.

Two updates on oesophagogastric junction adenocarcinoma from the fifth WHO classification: Alteration of definition and emphasis on HER2 test

INTRODUCTION

The incidence of oesophagogastric junction adenocarcinoma has increased rapidly but remains controversial over the last decades. There are two crucial updates of the fifth World Health Organization (WHO) classification, including the alteration of its definition and the emphasis on the human epidermal growth factor receptor 2 (HER2) test.

METHODS

A total of 566 clinicopathological samples from patients who were diagnosed with gastric adenocarcinoma were retrospectively analyzed. We comprehensively compared the clinicopathological features of oesophagogastric junction adenocarcinoma between the fourth (V4.0) and fifth (V5.0) WHO versions. The clinicalpathological features among oesophagogastric junction, proximal and distal gastric tumors with fourth and fifth edition were also compared, respectively. Also, we discuss the correlation of HER2-expression with clinicopathological features according to the V5.0.

RESULTS

The results showed that the difference was mainly between oesophagogastric junction and distal adenocarcinoma in V4.0, while some were found between proximal and distal adenocarcinoma in V5.0. Tumors invading the oesophagus more than 3cm were still mainly oesophagogastric junction tumors. The expression of HER2 in oesophagogastric junction and proximal gastric adenocarcinoma was still higher than that in gastric body and distal sites.

CONCLUSIONS

The clinicopathological parameters of the oesophagogastric junction tumors changed to some extent in the updated WHO version. The proximal gastric tumors tended to be more invasive, more than those located in oesophagogastric junction. But the latter with oesophageal invasion required additional management. The HER2-expression of oesophagogastric junction adenocarcinoma is the highest. The classification of V5.0 is reasonable and worth recommendation.

Adenocarcinoma of the esophagogastric junction and its background mucosal pathology: A comparative analysis according to Siewert classification in a Japanese cohort

Adenocarcinoma of the esophagogastric junction (AEG) has heterogeneous carcinogenic process due to its location straddling the esophagogastric junction. We assessed background mucosal pathology and its correlation with clinicopathological features of each Siewert type of AEG. Clinicopathological and immunohistochemical analyses of 103 AEGs and 58 gastric cancers (GCs) were conducted. Background mucosal features were evaluated according to the updated Sydney System. Siewert classification divided 103 AEGs into three type I, 75 type II, and 25 type III tumors, respectively. Two type I, 9 type II AEGs, and none of type III AEGs were Barrett-related and were excluded from further analysis. Background mucosa of type III AEGs more frequently showed moderate to marked degree of atrophy and intestinal metaplasia than those of type II AEGs and was very similar to those of GCs. Among type II AEGs, tumors with atrophic background were significantly associated with higher patient age and intestinal-type histology. Type II AEGs with nonatrophic background, but not those with atrophic background, showed more frequent mismatch repair deficiency, TP53 overexpression, and less frequent intestinal phenotypic markers expression than type III AEG or GC. Type II AEGs with atrophic background involved suprapancreatic nodes more frequently than those without. We demonstrated that chronic atrophic gastritis was a major precancerous condition of AEG in the Japanese population, especially Siewert type III which had background mucosal pathology similar to that of GC. Type II AEGs with and without atrophic background showed some clinicopathological differences, and these observations might represent heterogeneous carcinogenic process within type II AEGs.

Prevalence and clinicopathological characteristics of mismatch repair-deficient colorectal carcinoma in early onset cases as compared with late-onset cases: a retrospective cross-sectional study in Northeastern Iran

OBJECTIVES

Lynch syndrome (LS), a genetically inherited autosomal disorder, increases the incidence of colorectal carcinoma (CRC). We aimed to perform a universal strategy to assess the prevalence and clinicopathological characteristics of early onset CRCs at high risk of LS versus late-onset ones in the Iranian population.

SETTING

A local population-based study from Northeastern Iran.

PARTICIPANTS

321 consecutive CRCs and pathology specimen screened between 2013 and 2016.

PRIMARY AND SECONDARY OUTCOME MEASURES

Retrospectively, information regarding the clinical criteria was obtained by interviewing the patients with CRC or, their families. Pathologists tested tumours with immunohistochemistry (IHC) staining of four mismatch repair (MMR) proteins (MLH1, MSH2, MSH6 and PMS2). Tumours with absent IHC staining of MLH1 were tested for BRAF mutations to exclude sporadic CRCs. Prevalence of early onset CRCs at high risk of LS and familial CRC type X were assessed as primary and secondary outcome measures, respectively.

RESULTS

Of 321 CRCs (13/123 (10.57%), early onset vs 21/198 (10.6%) late-onset) were detected to be MMR-deficient (dMMR). Nine early onset cases and 14 late-onset ones with a loss of MLH1 underwent testing for the BRAF mutation, none of the early onset and four (2.02%) late-onset were recognised as sporadic. The difference in the outcome of IHC-analysis between early and late-onset CRCs at high risk of LS was not statistically significant (p=0.34). Majority of the suspected LS tumours from early onset patients had arisen in distal part (8/11 (72.72%) vs 8/14 (57.14%)), all of which were occurred in the rectum or sigmoid.

CONCLUSION

Clinically, these findings suggest that in case of limitation for BRAF testing, the practitioner in Iran may consider managing early onset dMMR cases like LS until access to BRAF testing becomes available to them, before germline testing to accurately diagnose LS.

The relationship between human muth homolog 1 gene mutation at site 415 and sporadic colon cancers in Chinese Han population

Background: The genetic factors of colon cancer play an important role in the tumor development and growth. The incidence of colon cancers has greatly increased in China. However, few data is available for the relationship between human muth homolog 1 (hMLH1) gene mutation at site 415 and sporadic colon cancers in Chinese population. Objective: Investigate the relationship between G→C mutation in hMLH1 gene at site 415 and sporadic colon cancers in Chinese Han population. Methods: Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing techniques, the genotype of the hMLH1 gene was analyzed at site 415 in 97 cases of sporadic colon cancer patients and 138 controls. Reverse-transcription (RT)-PCR was used to determine the level of hMLH1 mRNA expression in normal colonic mucosa of patients with different genotype. Results: The frequency of genotype C/C at the 415 site of the hMLH1 gene was significantly higher in colon cancer patients than in controls. The expression levels of hMLH1 mRNA in normal colonic mucosa were similar in colon cancer patients with different genotypes. Conclusion: G’!C mutation in hMLH1 gene at site 415 may represent a genetic factor that is associated with sporadic colon cancer in a small group of Chinese Han population.

Receptor tyrosine kinase amplified gastric cancer: Clinicopathologic characteristics and proposed screening algorithm

Although targeted therapy for receptor tyrosine kinases (RTKs) of advanced gastric cancers (AGCs) has been in the spotlight, guidelines for the identification of RTK-amplified gastric cancers (RA-GCs) have not been established. In this study, we investigate clinicopathologic characteristics of RA-GCs and propose a screening algorithm for their identification. We performed immunohistochemistry (IHC) for MLH1, MSH2, PMS2, MSH6, key RTKs (EGFR, HER2, MET), and p53, in situ hybridization for Epstein-Barr virus encoding RNA, and silver in situ hybridization (SISH) for EGFR, HER2, and MET using tissue microarrays of 993 AGCs. On IHC, 157 (15.8%) 61, (6.15%), and 85 (8.56%) out of 993 cases scored 2+ or 3+ for EGFR, HER2, and MET, respectively. On SISH, 31.2% (49/157), 80.3% (49/61), and 30.6% (26/85) of 2+ or 3+ cases on IHC showed amplification of the corresponding genes. Of the 993 cases, 104 were classified as RA-GCs. RA-GC status correlated with older age (P < 0.001), differentiated histology (P = 0.001), intestinal or mixed type by Lauren classification (P < 0.001), lymphovascular invasion (P = 0.026), and mutant-pattern of p53 (P < 0.001). The cases were divided into four subgroups using two classification systems, putative molecular classification and histologic-molecular classification, based on Lauren classification, IHC, and SISH results. The histologic-molecular classification showed higher sensitivity for identification of RA-GCs and predicted patient prognosis better than the putative molecular classification. In conclusion, RA-GCs show unique clinicopathologic features. The proposed algorithm based on histologic-molecular classification can be applied to select candidates for genetic examination and targeted therapy.

Altered Expression of the Dna Mismatch Repair Proteins Hmlh1 and Hmsh2 in Cutaneous Dysplastic Nevi and Malignant Melanoma

Molecular alterations in the mismatch repair system suggest that this mechanism may be important in the evolution of cutaneous melanoma. Our current study evaluated the expression of two mismatch repair proteins, hMLH1 and hMSH2, in dysplastic nevi (DN) and cutaneous melanoma (CM). Immunohistochemical staining of these proteins was performed on 55 CM and 30 DN specimens. The staining results were divided into three groups: negative, partially positive and strongly positive. Normal adjacent skin cells served as an internal control for positive immunostaining. Altered immunoreactivity of one of the proteins was found in four (13.4%) DN and seven (12.7%) CM. Lack of staining for hMLH1 was observed in two (6.7%) cases of DN and five (9.1%) cases of CM; staining for hMSH2 was absent in two (6.7%) of the DN and two (3.6%) of the CM specimens. Partially positive staining was found in 33.3% and 53.3% for hMLH1 and hMSH2, respectively, in DN, and in 54.5% and 69.1%, respectively, in CMM. Our study shows that complete or partial loss of MMR protein expression occurs in a subset of both DN and CM and may represent a distinct pathway in the development of some DN and CM.

Mismatch Repair Protein MSH2 Expression and Prognosis of Colorectal Cancer Patients

Introduction and aims

The role of genetic factors in the etiology and prognosis of patients with sporadic colorectal cancer is controversial. We have therefore investigated the biological and clinicopathological influence of immunohistochemical MSH2 expression in colorectal cancer.

Patients and methods

A total of 49 consecutive patients with unselected colorectal cancer operated on in our unit were included in the study. All tumors were resected and tumor specimens were evaluated for MSH2 expression. Clinicopathological data and patient survival were correlated with MSH2 staining. Uni- and multivariate analyses were performed. The minimum follow-up period was five years.

Results

Curative resection was performed in 34 patients (64.9%), 14 of whom subsequently relapsed. At the end of the overall follow-up 25 (51%) patients had died, 21 of cancer-related causes. Twenty-eight patients (57.1%) were negative for MSH2 staining. Only vascular invasion was significantly correlated with MSH2 expression (lower median values; p=0.04). The overall median survival was 47.9 months (95% CI=27–86.6%). Multivariate analysis of variables in relation to survival showed that T stage (p=0.001), N stage (p<0.001) and MSH2 expression (p=0.01) were independent factors for survival.

Conclusions

Reduced MSH2 expression is frequent in unselected colorectal cancer patients. Only vascular invasion was correlated with MSH2 expression in this study. Survival was related to TN stage and MSH2 staining.

Prevalence and clinicopathologic/molecular characteristics of mismatch repair-deficient colorectal cancer in the under-50-year-old Japanese population

PURPOSE

To clarify the prevalence and clinicopathologic/molecular characteristics of mismatch repair (MMR)-deficient colorectal cancer in the young Japanese population.

METHODS

Immunohistochemical analyses for MMR proteins (MLH1, MSH2, MSH6, and PMS2) were performed in formalin-fixed paraffin-embedded sections prepared from the resected CRC specimens of 119 consecutive patients aged <50 years old, who underwent resection of the primary tumor at our institution between 1996 and 2015. Analyses for somatic BRAF V600E mutation, somatic hypermethylation of the MLH1 promoter, and germline MMR gene mutations were undertaken where indicated.

RESULTS

MMR protein loss was found in 10 patients (8.4%), 7 (5.9%) of whom were subsequently identified to have Lynch syndrome (LS). The remaining 3 patients were categorized as having sporadic MMR-deficient CRC (n = 2) or "possible LS (n = 1)". In multivariate logistic regression analysis, the presence of tumor-infiltrating lymphocytes (P < 0.01), right-sided location of the tumor (P = 0.01), and a history of LS-associated tumors in the first-degree relatives (P < 0.01) were identified as independent factors predictive of MMR-deficient CRC.

CONCLUSION

These results are of value in the clinical management of patients with the early onset CRC under circumstances where universal tumor screening approaches for LS are still not available, like in Japan.

Genetic instability and increased mutational load: which diagnostic tool best direct patients with cancer to immunotherapy?

The occurrence of high rates of somatic mutations in cancer is believed to correspond to increased frequency of neo-epitope formation and tumor immunogenicity. Thus, classification of patients with cancer according to degree a somatic hyper-mutational status could be proposed as a predictive biomarker of responsiveness to immunotherapy with immune checkpoint inhibitors. Here, we discuss the suitable and reliable tests easily adoptable in clinical practice to assess somatic mutational status in patients with advanced cancer.

Epstein-Barr virus positivity, not mismatch repair-deficiency, is a favorable risk factor for lymph node metastasis in submucosa-invasive early gastric cancer

BACKGROUND

Epstein-Barr virus (EBV)-associated gastric cancer (GC) and microsatellite-instability-high GC are associated with a low prevalence of regional lymph node metastasis (LNM). To evaluate the feasibility of endoscopic treatment of EBV-associated and/or microsatellite-instability-high early GC (EGC), we analyzed the risk factors for LNM using a large series (n = 756) of submucosa-invasive (SM) EGC.

METHODS

EBV-encoded RNA in situ hybridization (EBER ISH) and immunohistochemistry for four mismatch repair (MMR) proteins (MLH1, PMS2, MSH2, and MSH6) were performed. The clinicopathologic features and results of EBER ISH and immunohistochemistry were compared according to the LNM status.

RESULTS

Among the cases, 146 EGCs (19.3 %) showed LNM. EBV negativity, larger tumor size (greater than 2 cm), deeper level of submucosal invasion, submucosal invasion depth greater than 500 µm, presence of ulceration, and presence of lymphovascular invasion (LVI) were associated with LNM. However, the MMR deficiency was not correlated with LNM. On multivariate regression analysis, larger tumor size (greater than 2 cm; odds ratio 1.6, p = 0.030), deeper level of submucosal invasion (odds ratio 2.9, p = 0.001), LVI (odds ratio 7.4, p < 0.001), and EBV negativity (p = 0.020) were independent risk factors for LNM in SM EGCs.

CONCLUSIONS

EBV positivity was a favorable risk factor for LNM in SM EGC. However, MMR deficiency was not associated with the status of LNM. Thus, we suggest that examination with EBER ISH could be considered for endoscopic resected specimens, especially in cases of SM EGC showing no LVI and clear resection margins.

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.

Mismatch repair deficiency screening via immunohistochemical staining in young Asians with colorectal cancers

BACKGROUND

The incidence of mismatch repair deficiency in colorectal cancer (CRC) in young people remains unknown in Asians. The present study assessed the clinicopathological features and efficacy of immunohistochemistry screening for Lynch syndrome in young Asian CRC patients.

MATERIAL AND METHODS

This was a retrospective review conducted in Singapore General Hospital between January 2006 and December 2010 of 240 unrelated patients under the age of 50. All patients had immunohistochemical (IHC) staining for mismatch repair proteins in resected CRC specimen data retrieved from a prospective computerized database.

RESULTS

A total of 21 % (n = 51) of the patients had abnormal IHC staining. Loss of staining for MLH1, MSH2, MSH6, and PMS2 proteins was observed in 10, 4, 6, and 13 % of tumors, respectively. Of the 22 patients who had abnormal staining of MLH1, 13 had concomitant abnormal staining for PMS2. One tumor specimen had abnormal staining in all four proteins. If the Amsterdam criteria alone were to be used, 86 % (n = 44) of the cohort would have not been detected for mismatch repair gene defects.

CONCLUSIONS

The overall burden of germline mismatch repair deficiency in the Singapore population may be as high as 21 %. The Amsterdam criteria alone are inadequate to detect Lynch syndrome patients. The use of IHC staining of at least four mismatch repair proteins is a useful screening strategy for Lynch syndrome diagnosis. Routine screening of mismatch repair deficiency may be recommended for all young Asian CRC patients.

Mismatch repair protein expression in colorectal cancer

INTRODUCTION

Alterations in at least six of the genes that encode proteins involved in the mismatch repair (MMR) system have been identified in either HNPCC or sporadic colon cancer. We aimed to analyse the proportion of patients with colorectal cancer with loss of immunostaining for MMR proteins in order to determine the feasibility of molecular screening for the loss of MMR proteins through the study of unselected patients with colorectal cancer.

METHODS

A group of 33 patients with colorectal cancer was randomly selected from the department of surgery bio-bank to determine the expression of MMR proteins in their FFPE tumour tissues using immunohistochemistry techniques. Changes in protein expression following transfection of colorectal tissues were observed in stained cells using Olympus BX60 microscope and image analySIS software.

RESULTS

Of the tissue specimens in which acceptable immunostaining was achieved, three samples showed loss of one or more of the MMR proteins. Both hMLH1 and hPMS2 proteins were not expressed in a 36 years old woman with cancer of the caecum. The expression of hMSH6 protein was undetermined in tumour tissues retrieved from a 61 years old man with cancer of the proximal colon. The third case was a 77 years old man with no documented family history of cancer, who had carcinoma of the rectum. He showed loss of hMLH1 expression in the tumour tissues.

CONCLUSIONS

Our findings and the previous reports pointed out the importance of molecular screening of patients with colorectal cancer for MSI using immunohistochemistry. This strategy managed to identify mutations in patients otherwise would not have been detected.

Loss of expression of the tumor suppressor CEACAM1 links different hereditary colorectal carcinoma subtypes to the genesis of sporadic colorectal carcinoma

According to their carcinogenesis, colorectal cancer (CRC) subtypes show distinct molecular parameters. Hereditary non-polypous colorectal cancer (HNPCC) is the most common inherited CRC characterized by clinical criteria and confirmed microsatellite instability (MSI). Interestingly, a recently identified subtype, familial colorectal cancer type X (FCC-X), shows the same clinical criteria but microsatellite stability (MSS). CEACAM1 is a known tumor suppressor that regulates apoptosis in colon cells, and its loss is one of the most frequent events in early tumorigenesis of CRC. Therefore its loss may characterize precursor colon cells prior to neoplastic transformation. We analyzed tumor specimens of HNPCC and FCC-X patients in order to investigate whether there is a loss of CEACAM1 expression analogous to sporadic CRC and whether the expression of CEACAM1 would distinguish between these tumor entities. No differences in CEACAM1 expression were noted between HNPPC (n = 38) and FCC-X (n = 30) tumors. CEACAM1 was reduced in near-identical frequencies in 36/38 (95%) HNPCC and 29/30 (97%) FCC-X. This is the first report to demonstrate the loss of CEACAM1 expression in hereditary CRC. There was no difference between HNPCC and FCC-X. The frequency of expression loss was comparable to sporadic CRC, indicating that loss of CEACAM1 is an early event in colorectal tumorigenesis linking the genesis of sporadic and hereditary CRC.

Unique ectopic lymph node-like structures present in human primary colorectal carcinoma are identified by immune gene array profiling

We hypothesized that immune gene-related signatures would predict the presence of unique histological features of lymphoid cell infiltrates in colorectal carcinoma (CRC) that correlate with clinical parameters. Metagene analysis with gene chip technology was performed on 326 CRCs, which were then sorted by low versus high gene scores. Microscopically, CRCs with a high gene score revealed a marked host immune response organized, remarkably, as lymphoid follicles. Proliferation involved both B and T cells. In every case, the presence of CD79a(+) B-cell precursors was identified, suggesting that the lymphoid follicles represent newly formed, ectopic lymph node-like structures. CD21(+) dendritic cells were present within the follicular germinal centers, and CD3(+) T cells were localized mainly in the parafollicular cortex zone surrounding the B-cell area of the follicles. A strong correlation between a 12-chemokine gene subset of the molecular profile and the presence of ectopic lymph node-like structures was associated with better patient survival independent of tumor staging, site location, microsatellite instability or stability, and patient treatment. These findings suggest beneficial, intratumoral immune cell priming and raise the possibility of immunotherapy intervention decisions based on molecular signatures that can identify the presence of tumor-localized, ectopic lymph node-like structures.

Three novel germline mutations in MLH1 and MSH2 in families with Lynch syndrome living on Jeju island, Korea

Hereditary non-polyposis colorectal cancer (HNPCC) is an autosomal dominant syndrome characterized by predisposition to early-onset cancers. HNPCC is caused by heterozygous loss-of-function mutations within the mismatch repair genes MLH1, MSH2, MSH6, PMS1, and PMS2. We genotyped the MLH1 and MSH2 genes in patients suffering from Lynch syndrome and in 11 unrelated patients who were diagnosed with colorectal cancer and had subsequently undergone surgery. Five Lynch syndrome patients carried germline mutations in MLH1 or MSH2. Two of these were identified as known mutations in MLH1: deletion of exon 10 and a point mutation (V384D). The remaining three patients exhibited novel mutations: a duplication (937_942dupGAAGTT) in MLH1; deletion of exons 8, 9, and 10; and a point mutation in MLH1 (F396I) combined with multiple missense mutations in MSH2 (D295G, K808E, Q855P, and I884T). The findings underline the importance of efficient pre-screening of conspicuous cases.

Clinicopathological and patient characteristics of early gastric neoplasia endoscopically resected with loss of Mlh1 expression

Hypermethylation of the promoter region of the MLH1 gene leads to loss of Mlh1 protein expression and plays a key role in the development of gastric cancer. Little is known about the association between Mlh1 expression and the clinicopathological and patient characteristics in early gastric neoplasia, particularly in endoscopically resected tumors. Immunohistochemistry was used to examine Mlh1 expression in 140 early gastric neoplasias obtained by endoscopic resection and comprising 31 gastric adenomas (GAs) and 109 early gastric cancers (EGCs), and compared them to corresponding clinicopathological and patient data. P53 expression and phenotypic profiles were also analyzed. The rate of reduced Mlh1 expression and P53 overexpression was 9.6 and 6.5% in GAs, and 27.5 and 27.5% in EGCs, respectively. In elderly patients (≥65 years of age), the aberrant expression of Mlh1 in EGCs was more significant in female than in male patients (59.9 vs. 29.8%; P=0.016). In addition, the frequency of aberrant Mlh1 expression in EGCs increased significantly in patients with oncological family histories and elevated gross type (P=0.033 and P=0.04, respectively). Moreover, a significant correlation was observed among aberrant Mlh1, P53-negative and HGM expression. The present findings suggest that loss of Mlh1 expression is associated with age, gender, oncological family history and tumor growth pattern in EGC. Patient and tumor characteristics are key factors in the screening, surveillance and diagnosis of early gastric neoplasia, particularly in elderly individuals.

DNA mismatch repair enzyme immunohistochemistry in colorectal cancer: a comparison of biopsy and resection material

BACKGROUND

Microsatellite instability (MSI) in colorectal cancer (CRC) may be predicted using mismatch repair protein (MMRP) immunohistochemistry (immunostaining), allowing focused genetic investigations and potentially influencing therapeutic interventions. Most laboratories perform immunostaining on surgical resection specimens. Endoscopic biopsy specimens are an alternative tissue source for immunostaining. Given the sensitivity of immunostaining to the degree of tissue fixation, endoscopic biopsy material may produce superior staining, based on faster and more thorough fixation. Moreover, in patients receiving neoadjuvant chemotherapy and/or radiotherapy, endoscopic biopsies may be more useful than surgical resection specimens by allowing assessment of MMR status prior to chemotherapy and/or radiotherapy induced changes in tumours. This study examines whether immunostaining for MMRP expression in CRC is as reliable on endoscopic biopsy material as on surgical resection specimens.

METHODS

Immunostaining for MLH1, PMS2, MSH2 and MHS6 was performed on 112 unselected CRC cases with both endoscopic biopsy and surgical resection material available. A single observer blindly examined intensity and distribution of staining and assessed MMRP expression. Two consultant histopathologists reviewed challenging cases. Endoscopic biopsies and surgical resections were compared using non-parametric statistical analysis.

RESULTS

Immunostaining for all four MMRPs on all 112 cases produced conclusive (i.e., fully interpretable) results in endoscopic biopsies. In surgical resection specimens, 10 stains from nine cases were inconclusive (stains for two MMRPs were inconclusive in one case). In cases where conclusive immunostaining was achieved, there was complete agreement in MMRP status between the endoscopic biopsy and corresponding surgical resection specimens. Overall, MMRP loss was identified in 13% of cases; 11% MLH1, 12% PMS2, 1% MSH2, and 1% MSH6. Immunostaining intensity was significantly higher (p < 0.0005) and the distribution of staining was significantly more uniform (p < 0.0005) on endoscopic biopsy than on surgical resection.

CONCLUSION

Endoscopic biopsy provides equal accuracy and easier interpretation of MMRP expression immunostaining compared to surgical resection specimens.

Absence of hMLH1 or hMSH2 expression as a stage-dependent prognostic factor in sporadic colorectal cancers

BACKGROUND

The predictive role of mismatch repair (MMR) status for survival after sporadic colorectal cancer remains a point of controversy. This study was designed to test the prognostic value of MMR status in sporadic colorectal cancers.

METHODS

The study included 318 patients with sporadic colorectal cancer who underwent primary tumor resection. MMR status was determined by the immunohistochemical analysis of hMLH1 and hMSH2 expression.

RESULTS

Thirty-six carcinomas (11.3%) showed abnormal MMR protein expression (22 hMLH1 negative and 14 hMSH2 negative) and were classified as MMR-defective tumors. An MMR defect was strongly associated with a reduced likelihood of lymph node (odds ratio, 0.32; 95% confidence interval [95% CI], 0.13-0.75) or distant organ metastases at diagnosis (odds ratio, 0.07; 95% CI, 0.01-0.62), independent of the clinicopathological features. Overall survival was significantly better in patients with MMR-defective tumors than in those with MMR-intact tumors (P = 0.013). In the subgroup analysis by stage, adjusted for other potential confounding variables, MMR status was not a statistically significant prognostic factor in stage I and II patients, while the MMR defect predicted a significantly better overall survival in stage III and IV patients (adjusted hazard ratio, 0.23; 95% CI, 0.06-0.97; P = 0.045).

CONCLUSIONS

At initial diagnosis, metastases were found at lower rates in MMR-defective tumors. MMR status may be a stage-dependent prognostic factor in patients with sporadic colorectal cancer.

Preliminary Results of Mismatch Repair Deficiency Screening via Immunohistochemical Staining in Young Asian Colorectal Cancers

Background:

The incidence of mismatch repair (MMR) deficiency in young colorectal cancers (CRC) remains unknown in Asians. This preliminary study assessed the clinicopathological features and efficacy of screening for MMR protein deficiency in young Asian CRC patients.

Methods:

From January 2006 to October 2009, patients under the age of 50 with immunohistochemical (IHC) staining for MMR proteins in resected CRC specimens were retrieved from a prospective computerised database.

Results:

Eighty unrelated patients comprising predominantly 80% Chinese (n = 64), with median age of diagnosis at 41 years (range 22–50 years) had IHC performed. Twenty-three per cent (n=18) of the patients had abnormal IHC staining. Loss of staining for MLH1, MSH2 and MSH6 proteins were observed in 18%, 2% and 6% of tumours respectively. Of the 15 patients who had abnormal staining of MLH1, three had concomitant equivocal staining for MSH6. One tumour specimen had abnormal staining in all 3 proteins. Multivariate analysis revealed that family history was the only significant predictive factor for defective MMR detection (OR 8.06, 95% CI 1.69–38.35, p=0.002). However if Amsterdam criteria alone were to be used, 72% (n=12) of the cohort would have not been detected for MMR gene defects.

Conclusion:

The overall burden of germline MMR deficiency in the Singapore population may be as high as 23%. Amsterdam criteria alone are insufficient to detect hereditary non-polyposis colorectal cancer (HNPCC) related patients. The use of IHC staining of at least 3 MMR proteins is a useful screening strategy for HNPCC diagnosis and routine screening of mismatch repair deficiency may be recommended for all young Asian CRC patients.

Genetic testing for hereditary nonpolyposis colorectal cancer (HNPCC)

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant cancer syndrome that confers an elevated risk of early-onset colorectal cancer (CRC) and increased lifetime risk for other cancers of the endometrium, stomach, small intestine, hepatobiliary system, kidney, ureter, and ovary. HNPCC accounts for up to 5% of all CRC, making it the most common hereditary colorectal cancer syndrome. Germline mutations in methyl-directed mismatch repair (MMR) genes give rise to microsatellite instability (MSI) in tumor DNA. HNPCC is most often associated with mutations in the MLH1 gene on 3p21, the MSH2 gene on 2p21, and to a lesser extent MSH6 on 2p16. This unit presents a comprehensive molecular and genetic screening strategy for HNPCC mutations in the MLH1, MSH2, and MSH6 genes, including analysis of MSI, mutation scanning by denaturing high-pressure liquid chromatography (DHPLC), and DNA sequencing analysis.

Clinicopathologic characteristics and outcomes of gastric cancers with the MSI-H phenotype

OBJECTIVES

We examined the correlation between microsatellite instability (MSI) status and the clinicopathological features and prognostic value in gastric cancer and compared the efficacy of immunohistochemical staining for hMLH1 and hMSH2 with a polymerase chain reaction (PCR)-based test.

METHODS

MSI status was examined in 328 consecutive gastric adenocarcinomas using tissue preserved in paraffin blocks. DNA extracted from tumor sections and the corresponding normal tissue was analyzed using PCR at the five microsatellite loci recommended by the National Cancer Institute (NCI). Immunohistochemical staining for hMLH1 and hMSH2 was performed and the results were compared with the MSI status measured using PCR. The relationship of the clinicopathologic variables to MSI status was analyzed.

RESULTS

Of the gastric cancers, 8.2% (n = 27) contained MSI-H and this was associated with older age (>70 years), distal tumor location, tumor size, and intestinal subtype. Lymphatic and vascular invasion were associated with the disease-free survival. On immunohistochemical staining, the loss of expression of hMLH1 or hMSH2 was observed in 11% (n = 36). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of immunohistochemical staining were 63.0%, 93.7%, 47.2%, 96.6%, and 91.2%, respectively.

CONCLUSIONS

Gastric cancers with MSI-H have specific clinicopathologic characteristics, such as older age at diagnosis, distal tumor location, increased tumor size, and intestinal histologic type. However, immunohistochemical staining for hMLH1 and hMSH2 is not as accurate as the PCR-based MSI test.

Prognostic significance of DNA repair proteins MLH1, MSH2 and MGMT expression in non-small-cell lung cancer and precursor lesions

Aims

To investigate the role of DNA repair proteins and their prognostic significance in non-small-cell lung cancer (NSCLC).

Methods and results

A retrospective analysis of 108 cases of stage I–II NSCLC was undertaken. Immunohistochemical expression of DNA repair proteins MLH1, MSH2 and MGMT was assessed using tissue microarrays of paraffin-embedded samples of invasive carcinoma and precursor lesions. Results were analysed in relation to clinicopathological parameters and patient survival. Reduced expression of MLH1 was found in 58.5% of tumours and occurred less frequently in poorly differentiated tumours (P = 0.044) and large cell carcinomas (P = 0.004). MSH2 and MGMT expression was reduced in 18.1% and 77.8% of cases, respectively. There was an inverse relationship between MLH1 and MSH2 expression (P = 0.012). Normal expression of MLH1, MSH2 and MGMT was found in all cases of squamous metaplasia and squamous dysplasia. Only a single case of carcinoma in situ (12.5%) showed reduced MLH1, none showed reduced MSH2 and 25% showed reduced MGMT. Survival analyses showed no prognostic significance based on expression of MLH1 (P = 0.92), MSH2 (P = 0.78) or MGMT (P = 0.57).

Conclusions

Reduction in expression of DNA repair proteins MLH1, MSH2 and MGMT is relatively common in NSCLC, appears to be a late event in the development of invasive malignancy and does not influence survival in this patient cohort.

Cooper W A, Kohonen-Corish M R J, Chan C, Kwun S Y, McCaughan B, Kennedy C, Sutherland R L & Lee C-S (2008) Histopathology52, 613–622

Prognostic significance of DNA repair proteins MLH1, MSH2 and MGMT expression in non-small-cell lung cancer and precursor lesions

DNA repair dysfunction in gastrointestinal tract cancers

The DNA repair system surveys the genome, which is always suffering from exposure to both exogenous as well as endogenous mutagens, to maintain the genetic information. The fact that the basis of this DNA repair system is highly conserved, from prokaryote to mammalian cells, suggests the importance of precise genome maintenance mechanisms for organisms. In the past 15 years, considerable progress has been made in understanding how repair processes interact and how disruptions of these mechanisms lead to the accumulation of mutations and carcinogenesis. In 1993, two groups reported that DNA mismatch repair could be associated with hereditary non-polyposis colorectal cancer, indicating a connection between faulty DNA repair function and cancer. More recently, an inherited disorder of DNA glycosylase, which removes mutagenic oxidized base from DNA, has been reported in individuals with a predisposition to multiple colorectal adenomas and carcinomas. This is the first report that directly indicates the role of the repair of oxidative DNA in human inherited cancer. Studies from gene knockout mice have elucidated the principal role of these repair systems in the process of carcinogenesis. Moreover, clinical samples derived from cancer patients have shown the direct involvement. This review focuses on the function of DNA mismatch repair and oxidative DNA/nucleotide repair among various DNA repair systems in cells, both of which are essentially involved in the carcinogenesis of gastrointestinal tract cancer.

Mismatch repair protein expression in Amsterdam II criteria-positive patients in Taiwan

BACKGROUND

Hereditary non-polyposis colorectal cancer (HNPCC) is characterized genetically by germline mutations in DNA mismatch repair (MMR) genes. Immunohistochemistry (IHC) has high sensitivity and specificity for identifying MMR-deficient tumours. This study investigated the clinical presentations and frequency of HNPCC in Taiwan by combined Amsterdam II criteria (AC-II) and IHC.

METHODS

In 1995-2003, 7108 patients with primary colorectal cancer registered in Chang Gung Memorial Hospital's Colorectal Cancer Registry were screened using AC-II. Tumour specimens were analysed for MMR protein expression by IHC, and relevant clinicopathological details were documented.

RESULTS

Some 83 patients fulfilled the AC-II. Clinicopathologically, 43 patients (52 per cent) had proximal tumours, ten (12 per cent) had poorly differentiated cancers, 17 (20 per cent) had mucinous adenocarcinoma and 51 (61 per cent) had stage I-II tumours. Seventeen patients developed second primary colonic and extracolonic cancers over a mean 7.2-year follow-up. Immunohistochemically, 58 patients were MMR protein deficient. They had a significantly earlier age of onset (P < 0.001), more proximal tumour location (P = 0.002), less advanced tumour stage (P = 0.008) and more second primary cancers (P = 0.017) compared with MMR-competent patients.

CONCLUSION

These data show significant differences in clinical features between MMR protein-deficient and MMR competent subgroups.

Mismatch repair genes hMLH1 and hMSH2 may not play an essential role in breast carcinogenesis

Breast carcinoma is one of the most common malignancies in women, and its carcinogenesis is still unknown. The role of microsatellite instability (MSI) in breast carcinogenesis has been inconsistent in the literature. Here we studied the expression of 2 mismatch repair genes, hMLH1 and hMSH2, in 211 cases of intraductal (DCIS; 90 cases) and invasive ductal carcinoma (121 cases) of the breast by immunohistochemical analysis; and evaluated its relationship with cytokeratin (CK) subtypes, along with expression of ER-alpha (138 cases positive, 73 cases negative); PR (118 cases positive, 93 cases negative), and HER-2/neu (47 cases positive, 164 cases negative); and clinical features such as patient age (157 cases>50 years, 54 cases<50 years), tumor size (31 cases of IDC>2 cm, 90 cases of IDC<2 cm), tumor grade (87 cases high nuclear grade, 124 case non-high grade), and lymph node metastasis (38 cases of IDC positive, 74 cases of IDC negative, 9 cases of IDC with no available data on lymph node status). For CK subtypes, 167 cases were classified as luminal subtype (expressing CK8 and/or CK18, negative for CK5/6, CK14, and CK17) and 44 cases were classified as nonluminal (most of them belonged to basal/stem subtype, expressing CK5/6, and/or CK14, and/or CK17). No typical or atypical medullary carcinoma was included in this study. Our results showed that no loss of nuclear expression of either hMLH1 or hMSH2 was identified in any of the 211 cases of DCIS or IDC regardless of the various pathological and clinical factors, suggesting that hMLH1 or hMSH2 may not play an essential role in the majority of cases of the breast carcinoma.

Immunohistochemical staining of hMLH1 and hMSH2 reflects microsatellite instability status in ovarian carcinoma

Microsatellite instability is due to defects in the family of DNA repair genes, primarily hMLH1 and hMSH2, which can be detected by immunohistochemical staining. However, it is unclear whether immunohistochemical staining can accurately predict microsatellite instability status. We sought here to evaluate the sensitivity, specificity, and predictive values of immunostaining for the expression of the DNA mismatch-repair genes hMLH1 or hMSH2 in predicting microsatellite instability in ovarian carcinoma. Tissue microarrays with specimens from 322 women with primary ovarian carcinoma were stained with antibodies to hMLH1 and hMSH2; cases in which either hMLH1 or hMSH2 were negative were analyzed for microsatellite instability with the five-marker panel recommended by the National Cancer Institute (BAT26, BAT25, D5S346, D2S123, and D17S250). Microsatellite instability was also analyzed in another 19 cases selected at random in which both hMLH1 and hMSH2 were positive. Tumors with instability at two or more of the five NCI markers were considered to have a high level of microsatellite instability; tumors showing instability at only one marker were considered microsatellite instability-low; and tumors in which no markers exhibited microsatellite instability were considered microsatellite stable. We found that negative staining for hMLH1 protein (five cases) or hMSH2 protein (two cases) was associated with high level of microsatellite instability. The sensitivity and specificity of immunohistochemical staining for hMLH1 were 62 and 100% and those of hMSH2 alone were 25 and 100%. Combining loss of expression of both hMLH1 and hMSH2 led to sensitivity, specificity, and positive and negative predictive values of 87, 100, 100, and 95%. These results suggest that use of a two-molecule panel (hMLH1 and hMSH2) can accurately determine the microsatellite instability status of patients with ovarian cancer.

Immunohistochemistry detects mismatch repair gene defects in colorectal cancer

OBJECTIVE

The clinical management of colorectal malignancies that arise via the mismatch repair gene pathway may differ from those that arise from the more common loss of heterozygosity pathway. They respond differently to chemotherapy, have a different prognosis and are associated with a raised incidence of metachronous lesions if a germline mutation is present. Established methods of detecting mismatch repair gene defects require the testing for microsatellite instability. This is expensive and requires specialized molecular biological resources and staff. An immunohistochemical method is attractive because it is far cheaper, and can be performed by most anatomical pathology laboratories. The aim of this study was to determine the incidence of mismatch repair gene defects using immunohistochemistry in a group of patients who were aged < or = 45 years at the time of diagnosis of colorectal cancer and to compare the patient survival and pathological features of tumours with and without mismatch repair gene defects.

METHODS

One hundred and four patients with colorectal cancer, diagnosed at 45 years or younger between January 1983 and December 2001, who had been managed at Groote Schuur Hospital, were identified from clinical records. Demographic and clinical data was collected from the clinical notes. The pathological reports were reviewed and the original histopathological slides retrieved. New tissue sections were cut from the original paraffin embedded tissue blocks to obtain both normal colonic mucosa and tumour on the same slide. There was insufficient tissue available or poor staining in 11 patients so 93 were available for the study.

RESULTS

The mismatch repair status was detected by antibodies to hMLH1 and hMSH2 gene product using a standard immunohistochemical technique. Fifty-six (60%) of 93 tumours demonstrated normal expression of both hMLH1 and hMSH2 protein. Twenty-five (27%) tumours did not express hMLH1 and 12 (13%) hMSH2 proteins. Comparison of the histopathological features revealed that a greater proportion of tumours with absence of either the hMLH1 or hMSH2 product were right sided, mucinous and poorly differentiated when compared to those that expressed the gene product. There was no detectable difference in overall survival or in survival of patients with Duke's C carcinoma when the groups were separated by the presence or absence of gene product.

CONCLUSIONS

This study found that 40% of patients who were < or = 45 years of age at the time of diagnosis of colorectal cancer seen at Groote Schuur Hospital have tumours which are related to the absence of expression of either hMLH1 or hMSH2 genes.

Does Biomolecular Characterization of Stage II/III Colorectal Cancer Have Any Prognostic Value?

As new improvements in the treatment of colorectal cancer have become available, it has become important to understand the benefits of new therapies or the deleterious effects stemming from the increased risk of toxicity. In particular, a more rational approach to adjuvant chemotherapy for patients with stage II/III disease should be defined by understanding which patients have a higher recurrence risk. Many studies have investigated several molecular markers, but none has been definitively associated with patient outcome. We present a review of studies that have evaluated the immunohistochemical correlation between expression of some biomarkers, such as thymidylate synthase, p53, Ki-67, Bcl-2, and microsatellite instability status expressed by Mut-L homologue 1 and Mut-S homologue 2 proteins, and the prognosis of patients with stage II/III colorectal cancer. We have evaluated studies in which > or = 100 patients were involved in an effort to ensure a representative study group. The only biomarker likely to have a prognostic value is microsatellite instability status, which correlated with a better prognosis.

Microsatellite instability in colorectal cancer

BACKGROUND

Microsatellite instability (MSI) causes hereditary non-polyposis colorectal cancer (HNPCC), and occurs in about 15 per cent of sporadic colorectal cancers. Although the basic mechanisms are not clear, there is increased understanding of the clinicopathological consequences of MSI.

METHODS

Medline was searched for articles with a combination of keywords relating to MSI in colorectal cancer, focusing on molecular mechanisms, clinicopathological implications, and prognostic and predictive value. Emphasis was placed on articles from the past 5 years.

RESULTS

The genetic mechanisms differ in hereditary (germline mutation) and sporadic (epigenetic silencing) colorectal cancer. The MSI pathway frequently has altered transforming growth factor beta receptor II and BAX genes, often beta-catenin, and occasionally p16INK4A and PTEN. Changes in K-ras, adenomatous polyposis coli and p53 are rare. Polymerase chain reaction testing for MSI is superior to immunohistochemistry, but complicated by the number and types of nucleotide markers. The Bethesda panel guides HNPCC testing, but guidelines are lacking for general screening. The presence and role of low-frequency MSI remains controversial. Tumours with MSI tend to occur in the proximal colon and be large, but they have a good prognosis. Their reduced response to adjuvant chemotherapy requires confirmation.

CONCLUSION

Research on colorectal cancer needs to be stratified according to microsatellite status in order further to explore the molecular mechanisms and clinicopathological consequences of MSI.

ΔTAp73 Upregulation Correlates With Poor Prognosis in Human Tumors: Putative In Vivo Network Involving p73 Isoforms, p53, and E2F-1

Purpose

Although full-length TAp73 variants largely mimic p53 suppressor activities, the transactivation-deficient transcripts ΔTAp73 exert an oncogenic effect by inactivating p53 and TAp73 suppressor properties. Additionally, ΔTAp73 may cooperate with oncogenic RAS to induce cell transformation, confer drug resistance, and induce the phosphorylation of phosphorylated Rb. Here, we study the expression of TAp73 and ΔTAp73 variants and assess possible associations with E2F-1, p53 and K-ras status. We address the possible clinical relevance of alterations in these genes.

Patients and Methods

We determine in 113 colon and 60 breast cancer patients (a) the expression levels of TAp73, ΔTAp73 (ΔEx2p73, ΔEx2/3p73, and ΔNp73), and E2F-1 transcripts by quantitative real-time reverse transcriptase polymerase chain reaction (PCR); (b) mutations in the first exon of K-ras by PCR–single-stranded confirmational polymorphism; and (c) p53 status by immunohistochemistry. Tumor characteristics were examined in each patient.

Results

Both suppressor and oncogenic isoforms of TP73 were significantly coupregulated in tumor tissues. Associations were observed between (a) p53 wild type status and upregulation of some TP73 variants; (b) overexpression of E2F-1 and some TP73 forms; and (c) upregulation of ΔTAp73 variants and advanced pathologic stage, lymph node metastasis, vascular invasion, presence of polyps, and tumor localization.

Conclusion

Overexpression of TP73 variants in tumor tissues indicates that they may be involved in colon and breast carcinogenesis. The association between upregulation of ΔTAp73 isoforms and poor prognosis features, specifically advanced tumor stage, suggests that they may be of practical clinical prognostic value. Interestingly, the in vivo associations identified here may indicate a functional network involving p73 variants, p53, and E2F-1.

Tumours from MSH2 mutation carriers show loss of MSH2 expression but many tumours from MLH1 mutation carriers exhibit weak positive MLH1 staining

Microsatellite analysis (MSA) in tumour tissue is useful for pre-selection of hereditary non-polyposis colorectal cancer (HNPCC) patients for mutation screening, but is time-consuming and cost-intensive. Immunohistochemistry (IHC) for expression of MLH1 and MSH2 proteins is simple, fast, and indicates the affected gene. IHC has therefore been proposed as an alternative pre-screening method. However, some authors report a lower sensitivity of IHC compared with MSA. The present study reports IHC results for MSH2 and MLH1 performed in 82 tumours with high microsatellite instability (MSI-H) from 81 carriers of pathogenic mutations in MSH2 or MLH1. One hundred per cent (38/38) of the tumours from MSH2 mutation carriers showed loss of MSH2 staining; in all cases, the affected MSH2 gene was predicted correctly by IHC. Complete loss of MLH1 expression was observed in 66% (29/44) of MLH1 mutation carriers. Weak positive MLH1 staining was observed in 14 (32%) cases and, in one case, normal MLH1 staining was seen. The pathologist was aware of the weak staining pattern as an indicator of an MLH1 mutation; 98% of the MLH1 mutations were predicted correctly. To evaluate whether weak positive MLH1 staining is observed more often with in-frame or missense mutations, IHC data from 23 MSI-H tumours from carriers of unspecified variants were added and mutations were grouped into truncating mutations, large non-truncating deletions, and small non-truncating mutations. Weak MLH1 staining was observed in all three categories and it is postulated that other factors, such as mutation of the second allele, also influence protein expression. In conclusion, IHC can be regarded as a very useful method for selecting HNPCC patients for mutation analysis, as long as it is interpreted by an experienced pathologist. The high specificity of IHC in terms of indicating the affected gene is useful for evaluating unspecified variants. However, the staining pattern does not predict whether the underlying germ-line mutation is truncating or not.

Routine testing for mismatch repair deficiency in sporadic colorectal cancer is justified

This study prospectively examines the accuracy of immunohistochemical staining in the identification of mismatch repair defective (MMRD) colorectal cancer in routine clinical practice. The potential impact of this information on decisions regarding adjuvant treatment and germline testing were quantified. A consecutive series of fresh tissue (836 cancers) was obtained from 786 individuals undergoing curative surgery for colorectal cancer at one institution. As part of normal practice, each tumour was screened for the expression of MLH1 and MSH2 by immunohistochemical staining (IHC) and relevant clinicopathological details were documented. Microsatellite instability (MSI) was assessed using standard markers. Overall, 108 (13%) tumours showed loss of staining for either MLH1 (92 tumours) or MSH2 (16 tumours). The positive predictive value of mismatch repair IHC when used alone in the detection of MSI tumours was 88%, and the negative predictive value was 97%. Specificity and positive predictive value were improved by correlation with microsatellite status. Tumour stage (HR 3.5, 95% CI 2.0-6.0), vascular space invasion (HR 1.9, 95% CI 1.2-3.0) and mismatch repair deficiency (HR 0.2, 95% CI 0.05-0.87) were independent prognostic factors in stages II and III disease. Screening by mismatch repair IHC could reasonably have been expected to prevent ineffective treatment in 3.6% of stage II and 7.6% of stage III patients. The frequency of germline mismatch repair mutations was 0.8%, representing six unsuspected hereditary non-polyposis colorectal cancer (HNPCC) cases. Routine screening of colorectal cancers by mismatch repair IHC identifies individuals at low risk of relapse, and can prevent unnecessary adjuvant treatments in a significant number of individuals. Abnormal immunohistochemistry should be confirmed by microsatellite testing to ensure that false-positive results do not adversely impact on treatment decisions.

Tissue microarray analysis of hMSH2 expression predicts outcome in men with prostate cancer

PURPOSE

Mismatch repair genes are responsible for the coordinated correction of misincorporated nucleotides formed during DNA replication. Mismatch repair expression is altered in a subset of prostate cancers (PCs) and a recent study suggested that time to biochemical recurrence following prostatectomy correlated with the degree of hMSH2 immunohistochemical staining. We compared hMSH2 expression and survival in clinically organ confined PC.

MATERIALS AND METHODS

A prostate tissue microarray was constructed using 243 specimens from patients who underwent radical prostatectomy with extended lymph node dissection for clinically organ confined PC with up to 12 years of followup. Immunohistochemistry was performed with anti-human MSH2 monoclonal antibody. Three independent observers evaluated hMSH2 expression on a scale of 0 to 4. Low expression was defined as a score of less than 2 and high expression was defined as a score of 2 or higher. Statistical analysis used the Fisher exact test, and Goodman and Kruskal gamma coefficient.

RESULTS

Higher Gleason score significantly correlated with higher hMSH2 expression (p < 0.0002). Low hMSH2 expression correlated with increased overall, disease-free and biochemical disease-free survival (all p < 0.01). Analysis comparing low vs high hMSH2 expression was significant with respect to overall (p = 0.0004), disease-free (p = 0.005) and biochemical disease-free (p = 0.0177) survival.

CONCLUSIONS

hMSH2 is differentially expressed in malignant prostate tissue and hMSH2 immunohistochemical staining intensity correlates with Gleason score, overall and disease-free survival. Taken together our results suggest that hMSH2 expression may be a useful prognostic biomarker for outcome in men with clinically organ confined PC.

Microsatellite instability testing in colorectal carcinoma: choice of markers affects sensitivity of detection of mismatch repair-deficient tumors

PURPOSE

Microsatellite instability (MSI) is found in 10% to 15% of sporadic colorectal tumors and is usually caused by defects in DNA mismatch repair (MMR). In 1997, a panel of microsatellite markers including mononucleotide and dinucleotide repeats was recommended by a National Cancer Institute workshop on MSI. We investigated the relationship between instability of these markers and MMR protein expression in a cohort of sporadic colorectal cancer patients.

EXPERIMENTAL DESIGN

Paraffin sections of normal and tumor tissue from 262 colorectal cancer patients were examined for MSI status by PCR amplification and for MMR protein expression using antibodies against hMLH1, hPMS2, hMSH2, and hMSH6.

RESULTS

Twenty-six (10%) of the patients studied had tumors with a high level of MSI (MSI-H). The frequencies of MSI were the same in African-American and Caucasian patients. Each of the MSI-H tumors had mutations in both mononucleotide and dinucleotide repeats and had loss of MMR protein expression, as did two tumors that had low levels of MSI (MSI-L). These two MSI-L tumors exhibited mutations in mononucleotide repeats only, whereas eight of the other nine MSI-L tumors had mutations in just a single dinucleotide repeat. There was not a statistically significant difference in outcomes between patients whose tumors were MMR-positive or MMR-negative, although there was a slight trend toward improved survival among those with MMR-deficient tumors.

CONCLUSIONS

The choice of microsatellite markers is important for MSI testing. Examination of mononucleotide repeats is sufficient for detection of tumors with MMR defects, whereas instability only in dinucleotides is characteristic of MSI-L/MMR-positive tumors.

Value of microsatellite instability typing in detecting hereditary non-polyposis colorectal cancer

AIM OF THE STUDY

To detect hereditary non-polyposis colorectal cancer (HNPCC) patients with a strategy combining clinical selection (patient age at onset of cancer less than 50 years or family history of HNPCC tumors) and microsatellite instability typing plus immunohistochemistry, leading to mismatch repair (MMR) germline mutation analysis.

METHODS

Tumors were screened for microsatellite instability (MSI) and for hmlh1 and hmsh2 immunohistochemical expression. Germline mutation analysis was performed to search for MLH1 and MSH2 mutations in patients with MSI-High and MSI-Low tumors.

RESULTS

197 adenocarcinomas were studied: 164 patients were< or =50 years old, 33 were older than 50 years but had a family history of HNPCC tumors. Fifty tumors (25.4%) were MSI-High, 10 were MSI-Low (5.1%), and 130 were MS-Stable (66%). MSI typing was inconclusive in 7 (3.5%). Immunohistochemistry screening was performed on 165 tumors: sensitivity was 63.6%, specificity was 99%. Germline mutation analysis was performed in 33/60 MSI-High or Low tumors: 23 mutations were noted (70% of the tested patients).

CONCLUSION

This proposed strategy of determining microsatellite instability in young colorectal cancer patients or in patients with a family history of HNPCC tumors led to an increased frequency in the detection of MMR germline mutations.

Defective DNA mismatch repair in long-term (> or =3 years) survivors with pancreatic cancer

BACKGROUND/AIMS

Defective DNA mismatch repair (MMR) in pancreatic cancer, reported in up to 13% of sporadic pancreatic cancers, may predict a good prognosis. To determine if long-term survival in pancreatic cancer could be attributed to defective DNA MMR, we ascertained its prevalence in 35 pancreatic cancer patients who survived > or =3 years after surgery.

METHODS

We performed immunohistochemistry (IHC) for MMR proteins hMLH1, hMSH2, and hMSH6 in all 35 tumors and microsatellite instability (MSI) studies in 34/35 tumors using 10 microsatellite markers in paired normal and tumor DNA. Defective DNA MMR was defined as absence of protein expression on IHC and/or MSI in > or =30% of markers studied.

RESULTS

On IHC, 3/35 (8.6%) tumors had defective DNA MMR. All 3 had absent expression of a DNA MMR protein (hMLH1 in 2 and hMSH2) and 2/3 also had MSI; the third could not be tested. Definitely 2, and probably all 3 patients had hereditary nonpolyposis colon cancer as determined by clinical and genetic profiles.

CONCLUSION

Defective DNA MMR is uncommon in long-term survivors of pancreatic cancer and does not account for the survival benefit in those with sporadic pancreatic cancer.

Asociación entre la inestabilidad de microsatélites y las características clínicas y anatomopatológicas en pacientes con cáncer de colon esporádico

BACKGROUND AND OBJECTIVE

Currently, colon cancer is a leading cause of cancer death world-wide. It progresses according to three molecular pathways, named suppressor, mutador and methylator. Microsatellite instability is a hallmark of the lack of reparation, of DNA mismatches and it characterizes a subset of colon tumors (unstable tumors, MSI). MSI-H patients (high degree of microsatellite instability) seem to share clinico-pathological differences with MSS (microsatellite stable) and MSI-L (low degree of microsatellite instability) patients. In this study, associations between high degree of microsatellite instability and pathological (location, mucinous content, differentiation grade, stages T3N0, stages II and III) and clinical features (response to chemotherapy, disease-free survival and overall survival) were evaluated.

PATIENTS AND METHOD

117 patients with sporadic colon cancer were classified into two populations (MSS/MSI-L and MSI-H) by using PCR and electrophoresis of seven microsatellites, according to the National Cancer Institute recommendations.

RESULTS

MSI-H tumors tended to be located in the right colon (p = 0.022) and were of mucinous histologic type (p = 0.04). No differences in disease-free survival and overall survival between group of stage II and III patients with MSS/ MSI-L and corresponding ones with MSI-H colon cancer were found (p = 0.54, p = 0.37, respectively). Conversely, MSI-H patients with stage II colon cancer had a favourable prognosis (p = 0.027). Nevertheless, response to 5-fluorouracil (5-FU) and leucovorin was similar in MSS/ MSI-L and MSI-H groups (p = 0.38).

CONCLUSIONS

MSI-H patients are characterized by certain pathological features; those MSI-H patients with a stage II seem to have a better prognosis than MSS/ MSI-L patients.

Clinicopathological and molecular genetic analysis of HNPCC in China

AIM: To explore the clinicopathological and molecular genetic features of hereditary nonpolyposis colorectal cancer (HNPCC) in Chinese population.

METHODS: We collected 16 Chinese HNPCC families from Wenzhou, Zhejiang Province, China. Tumor tissues and peripheral white blood cells were studied using microdissection, microsatellite analysis, immunostaining of hMSH2 and hMLH1 proteins and direct DNA sequencing of hMSH2 and hMLH1 genes.

RESULTS: (1) A total of 50 patients had CRC. Average age at diagnosis of the first CRC was 45.7 years; 40.9% and 28.7% of the CRCs were located proximal to the splenic flexure and in the rectum, respectively. Thirty-eight percent of the colorectal cancer patients had synchronous and metachronous CRC. 34.4% and 25% of the CRCs were poor differentiation cancer and mucinous adenocarcinoma, respectively. Fourteen extracoloni tumors were found, and the hepatic cancer was the most common tumor type. Twenty-one patients whose median survival time was 5.7 years died during 1-23 years. Twenty-nine patients have survived for 1-28 years, 58.6%, 41.4% and 24.1% patients have survived for more than 5, 10 and 15 years, respectively; (2) All nine tumor-tissues showed microsatellite instability (MSI) at more than two loci. Four tumor-tissues lost hMSH2 protein expression and one lost hMLH1 protein expression. Three pathological germline mutations were identified from five genetically analyzed families; two of three mutations had not been reported previously as they were a transition from C to A in exon 14 (codon 743) of hMSH2 and a TTC deletion in exon 14 (codon 530) of hMLH1.

CONCLUSION: Chinese HNPCC have specific clinicopathological features, such as early onset, propensity to involve the proximal colon, and high frequency of multiple CRCs, liver cancer more frequent than endometrial cancer. Chinese HNPCC showed relatively frequent germline mutation of mismatch repair (MMR) genes that correlated closely with high-level MSI and loss of expression of MMR genes protein.

Value of immunohistochemical detection of DNA mismatch repair proteins in predicting germline mutation in hereditary colorectal neoplasms

The utility of immunohistochemistry (IHC) as a screening method for the identification of persons with mutations in the DNA mismatch repair (MMR) genes in hereditary nonpolyposis colorectal cancer (HNPCC) remains to be defined. In this study, we analyzed the value of IHC versus that of microsatellite instability (MSI) testing in predicting mutation status of the MLH1, MSH2, and MSH6 genes in colorectal carcinomas and adenomas, and explored the frequency and significance of immunohistochemical staining variability. The study samples included 83 carcinomas and 29 adenomas derived from 110 patients who had strong family histories of colorectal cancer. Our results showed that IHC correctly predicted MSI status in 76% of the cases with a specificity of 100%. The overall sensitivity of IHC in predicting a germline mutation was 79% (30 of 38) with a specificity of 89% (48 of 54), whereas that of MSI testing was 97% (30 of 31) with a specificity of 83% (35 of 42). Six of 31 analyzable cases that had a disease-causing mutation and exhibited MSI showed normal IHC. The lower sensitivity of IHC was caused mainly by its low sensitivity in detecting MLH1 gene mutation (4 of 9). Coexisting adenomas and carcinomas observed in the same slide (n=12) showed a similar or identical staining pattern for all three proteins. No significant difference was detected in the sensitivity of IHC or MSI in detecting a germline mutation between isolated adenomas and carcinomas. In IHC-positive cases, heterogeneous staining was noted in 30% to 40% of the cases with the three different antibodies, and cytoplasmic staining in 5% to 13%. Weak IHC (defined as positive staining in <10% of the tumor with weak intensity) was noted in 14 tumors: 5 for the MLH1 antibody, 1 for MSH2, and 8 for MSH6. One of the 5 MLH1 cases exhibited MSI and had an MLH1 germline mutation. Five of the 8 MSH6 cases exhibited MSI and had MSH2 germline mutations. In conclusion, our study shows that 1) IHC identifies a significant portion of colorectal tumors derived from MMR gene germline mutation carriers and can be used as an adjunct measure in the identification of HNPCC families, but IHC cannot replace MSI testing; 2) adenomas have similar MMR protein expression patterns as carcinomas and may serve as an adequate sample for screening purposes in the identification of patients with MMR mutations; 3) not all IHC-positive cases show uniform positivity throughout the tumor; and 4) weak and focal staining of an MMR protein may be associated with MSI or gene mutation or both, suggesting the need to incorporate staining intensity in further IHC studies.

What is the best way to assess microsatellite instability status in colorectal cancer? Study on a population base of 462 colorectal cancers

The assessment of the microsatellite instability (MSI) status in colorectal cancers is presently warranted for three reasons: 1) as a screening tool for hereditary nonpolyposis colorectal cancer, 2) as a prognostic marker, and 3) as a potential predictive factor of chemotherapy response. The aim of this study was to evaluate, on a large scale with tissue samples coming from a number of different sources, the difficulties met with routine use of immunohistochemistry (IHC) and to determine if it really does offer an accurate alternative to PCR genotyping. Colorectal carcinomas from 462 consecutive patients resected in public or private hospitals were assessed for MSI status by two methods: MSI testing (with BAT-26 microsatellite) and IHC detection of hMLH1, hMSH2, and hMSH6 proteins. Of the 398 cancers tested, immunohistochemistry was noncontributory in 42 (10.5%), focal in 9 (2.3%), and discordant with the PCR results in 36 (9%). For these 87 cases, complementary analyses were performed to explain discrepancy. After additional IHC assay with modified processing protocols, 8 cases remained noncontributory, 2 focal, and 28 discordant: 18 microsatellite stability IHC/MSI PCR and 10 MSI IHC/microsatellite stability PCR. For these discordant cases, we performed a multiplex PCR assay on DNA extracted from the frozen sample and BAT-26 was amplified from DNA extracted from the paraffin blocks used for IHC. Four discordant cases were reclassified after PCR multiplex assay (3 as MSI and 1 as microsatellite stability). Five other cases displayed intratumoral heterogeneity and 19 remained discordant. The discrepancy could be partly explained by variable technical protocols of fixation in the different laboratories, leading to variations in staining quality and difficulties in IHC interpretation. This population-based study is the first one to show that IHC is not sensitive and specific enough to be used routinely. Immunohistochemistry analysis of MMR proteins must be performed in standardized conditions and interpreted by confirmed pathologists. It cannot replace PCR as long as protocols are not optimized and harmonized.

Relationship between MUC5AC and altered expression of MLH1 protein in mucinous and non-mucinous colorectal carcinomas

The main purpose of this study was to examine the expression of mucins and mismatch repair proteins in colorectal carcinomas. The immunohistochemical distribution of apomucins MUC2, MUC5AC, and the expression of MLH1 and MSH2 proteins were examined in 76 mucinous and 60 non-mucinous colorectal carcinomas. MUC2 was noted in all mucinous carcinomas, whereas MUC5AC was present in 41 cases only (54%). In non-mucinous carcinomas, MUC2 was expressed in 61.7% of the tumors; by contrast, MUC5AC was present in 20% of the cases. The expression level of apomucins was significantly different in mucinous and non-mucinous lesions (p<0.001). Twenty-seven (35.5%) of the mucinous carcinomas showed no MLH1 expression, whereas 11 (18.3%) of the non-mucinous tumors did. This difference was statistically significant (p<0.005). Altered expression of MSH2 protein was never observed. The lack of MLH1 expression was considerably more frequent in carcinomas with secretion of MUC5AC (p<0.005). Our study has demonstrated this close relationship by immunohistochemical methods. In summary, our data show: (1) differences in the expression of mucins between mucinous and non-mucinous tumors; (2) a high frequency of altered MLH1 protein expression (35.5%) in mucinous carcinomas; (3) a significant relationship between the presence of MUC5AC and the altered expression of MLH1 protein in colorectal carcinomas.

Defective mismatch repair in the pathogenesis of low-grade appendiceal mucinous neoplasms and adenocarcinomas

Defective DNA mismatch repair has been proposed as a second pathway for colonic carcinogenesis, particularly in tumors arising in the right colon. We investigated whether tumors arising in the appendix are associated with defective DNA mismatch repair using immunohistochemistry for mismatch repair enzymes hMLH-1, hMSH-2, hMSH-6, and hPMS-2. These immunoassays have been shown to be highly sensitive and specific for defective DNA mismatch repair in sporadic and familial adenocarcinomas. Sporadic adenocarcinomas with defective DNA mismatch repair essentially always show loss of hMLH-1, while loss of hMSH-2, hMSH-6, or hPMS-2 is almost always due to germline mutation. In all, 35 cases of appendiceal epithelial neoplasms were evaluated, comprising 18 low-grade appendiceal mucinous neoplasms confined to the appendix; eight low-grade appendiceal mucinous neoplasms with extra-appendiceal spread (five peritoneum and ovaries, two peritoneum, one ovaries only); and nine invasive adenocarcinomas (three with metastatic disease). All immunohistochemical slides were reviewed by two pathologists. One (11%) invasive adenocarcinoma showed absent expression of hMSH-2 and hMSH-6, but preserved hMLH-1 and hPMS-2 expression. This case was a 26-year-old female with a history of synovial sarcoma who presented with acute appendicitis and appendiceal perforation (median age for other invasive carcinomas, 62 years; range 38-76 years). The appendiceal tumor was a moderately differentiated, colonic-type adenocarcinoma without significant extracellular mucin or tumor-infiltrating lymphocytes. The remaining invasive carcinomas and low-grade appendiceal mucinous neoplasms demonstrated preserved expression of all mismatch repair enzymes, including the seven cases in which extra-appendiceal tumor was also evaluated. We conclude that defective DNA mismatch repair does not play a role in the pathogenesis of low-grade appendiceal mucinous neoplasms. Defective DNA mismatch was found in 11% of invasive carcinomas, likely due to a germline mutation. These findings suggest that sporadic appendiceal neoplasia rarely arises through the defective DNA mismatch repair (mutator) pathway.

The utility of immunohistochemical detection of DNA mismatch repair gene proteins

Since the development of monoclonal antibodies against the MSH2 protein by Leach et al. in 1996, a series of investigations has been undertaken to determine the utility of immunohistochemical detection of DNA mismatch repair (MMR) gene proteins in the identification of hereditary or sporadic colorectal tumors with microsatellite instability. These studies, however, have been performed with different aims and on different patient populations. Interpretation of these immunohistochemical data relies on a thorough understanding of the biological and technical factors that affect the detection of MMR proteins. In this review, we analyze the data from the published research studies, pointing out the various factors affecting immunohistochemical detection of MMR proteins and projecting the utility of immunohistochemistry in different clinical settings.

Microsatellite instability and mutation analysis among southern Italian patients with colorectal carcinoma: detection of different alterations accounting for MLH1 and MSH2 inactivation in familial cases

BACKGROUND

Microsatellite instability (MSI) is due to defective DNA mismatch repair (MMR) and has been detected at various rates in colorectal carcinoma (CRC). The role of MSI in colorectal tumorigenesis was assessed further in this study by both microsatellite analysis of two CRC subsets [unselected patients (n = 215) and patients <50 years of age (n = 95)], and mutation screening of the two major MMR genes MLH1 and MSH2 among familial CRC cases.

PATIENTS AND METHODS

PCR-based microsatellite analysis was performed on paraffin-embedded tissues. In CRC families, MLH1/MSH2 mutation analysis and MLH1/MSH2 immunostaining were performed on germline DNA and MSI+ tumour tissues, respectively.

RESULTS

The MSI+ phenotype was detected in 75 (24%) patients, with higher incidence in early-onset or proximally located tumours. Among 220 patients investigated for family cancer history, MSI frequency was markedly higher in familial [18/27 (67%)] than in sporadic [32/193 (17%)] cases. Three MLH1 and six MSH2 germline mutations were identified in 14 out of 36 (39%) CRC families. Prevalence of MLH1/MSH2 mutations in CRC families was significantly increased by the presence of: (i) fulfilled Amsterdam criteria; (ii) four or more CRCs; or (iii) one or more endometrial cancer. While MSH2 was found mostly mutated, almost all [8/9 (89%)] familial MSI+ cases with loss of the MLH1 protein were negative for MLH1 germline mutations.

CONCLUSIONS

Both genetic (for MSH2) and gene-silencing (for MLH1) alterations seem to be involved in CRC pathogenesis.

Significance of Mismatch Repair Protein Expression in the Chemotherapeutic Response of Sporadic Invasive Ductal Carcinoma of the Breast

The mismatch repair (MMR) gene plays a key role in the correction of DNA damage, and the loss of MMR has been implicated in resistance to a variety of chemotherapeutic drugs. The purpose of this study was to assess whether the reduced expression of hMLH1 and/or hMSH2 affects the chemotherapeutic responsiveness of sporadic invasive ductal carcinoma of the breast. Immunohistochemical studies were performed on 71 histologic specimens of breast cancer taken from the patients treated with surgery and subsequent cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) or cyclophosphamide, Adriamycin, and 5-fluorouracil (CAF) chemotherapy for stage II or III primary breast cancer. Single-strand conformational polymorphism polymerase chain reaction (PCR-SSCP) and sequencing were carried out in 16 patients. A combined immunoreactivity score (hMLH1-IS and hMSH2-IS) was calculated by multiplying the staining grade by the intensity score. Positive expression (>4) of hMLH1-IS and hMSH2-IS were 57.7% and 60.6%, respectively, and complete losses of hMLH1 and hMSH2 were observed in 4.2% of patients. Of the patients with advanced cancer with lymph node metastasis, those having a low hMLH1-IS had a significantly higher failure rate with the CMF regimen than those having a high hMLH1-IS (p = 0.03). No significant difference was noted in chemotherapeutic response according to hMLH1 and hMSH2 expression in the CAF group. Both hMLH1-IS (p = 0.03) and progesterone receptor (PR) status (p = 0.03) were well correlated with CMF chemotherapy response in breast cancers with lymph node metastasis. Our study shows that a lack of hMLH1 expression may play a role in drug resistance, especially in the CMF group, and immunohistochemical assay for MMR protein can be used as a convenient tool for evaluating chemotherapeutic response in patients with breast cancer.