Is reduced expression of mismatch repair genes MLH1 and MSH2 in patients with sporadic colorectal cancer related to their prognosis?

Comparison of Microsatellite Instability With Clinicopathologic Data in Patients With Colon Adenocarcinoma

Background Microsatellite instability (MSI) is a genetic condition caused by errors in DNA repair genes that cause colorectal cancer (CRC). The literature contradicts the frequency of MSI in sporadic CRCs and its effect on prognosis. This study investigated the distribution of clinicopathologic features and the relationship between MSI and survival outcomes. Methodology This is a retrospective study of 101 consecutive cases of CRC and immunohistochemical studies. All cases were retrospectively reviewed and reevaluated by histological grade, lymphovascular invasion, perineural invasion, tumor borders, dirty necrosis, tumor-infiltrating lymphocytes (TILs), Crohn's-like lymphoid reaction, mucinous and medullary differentiation, and tumoral budding from pathological slides. An immunohistochemical study was performed in appropriate blocks for using MLH-1, MSH-2, MSH-6, and PMS-2. We collected the clinical stage, pathological tumor stage, lymph node metastasis, age, sex, tumor diameter, distant metastasis, localization, and survival information from patients' clinical data. Results There was no statistically significant difference between the two groups regarding age, gender, tumor diameter, histological grade, tumor border, dirty necrosis, TILs, N and M stage, perineural and lymphovascular invasion, mucinous differentiation, medullary differentiation, and tumor budding characteristics of the patients. The MSI-H group was more frequently located in the right colon and transverse colon (p < 0.001), and the T stage was higher among them than in the MSI-L group (p = 0.014). Upon multivariate regression analysis, MSI status had no significant effect on survival time. Age and stage N and M were independent prognostic factors for colon cancer prognosis. Conclusions Our study presented the distribution of clinicopathological features and their relationship with MSI for 101 regional CRC patients. MSI status was detected by immunohistochemistry. Identifying MSI in CRCs may help personalize therapy planning. As the distribution of the features may vary from population to population, further investigations are needed on this topic.

Butyrate Inhibits Indices of Colorectal Carcinogenesis via Enhancing α-Ketoglutarate-Dependent DNA Demethylation of Mismatch Repair Genes

SCOPE

Butyrate, the fermentation end product of gut microbiota in the colon, is known for its antitumor effects, but the mechanisms remained to be defined. α-ketoglutarate (α-KG) mediates DNA demethylation and aberrant epigenetic modifications are associated with carcinogenesis. The objectives of this study are to evaluate the effects of butyrate on α-KG mediated epigenetic modification in colorectal adenocarcinoma HT-29 and Caco-2 cells.

METHODS AND RESULTS

Butyrate suppressed proliferation, potentiated differentiation, and induced apoptosis in both HT-29 and Caco-2 cells, associated with enhanced expression of isocitrate dehydrogenase 1 (IDH1) and pyruvate dehydrogenase. Furthermore, butyrate upregulated acetyl-CoA and α-KG, concomitant with enhanced histone acetylation and DNA demethylation in the promoter of DNA mismatch repair (MMR) gene. Knocking down IDH1 abolished the positive effects of butyrate on CRC apoptosis and MMR protein expression, in conjunction with reduced α-KG content. Importantly, α-KG supplementation recovered the beneficial effects of butyrate in IDH1-deficient cells.

CONCLUSION

In summary, butyrate inhibits indices of colorectal carcinogenesis in an α-KG-dependent manner.

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.

Low expression of MSH2 DNA repair protein is associated with poor prognosis in head and neck squamous cell carcinoma

Objective

This study aimed to investigate the expression of the MSH2 DNA repair protein in head and neck squamous cell carcinoma (HNSCC) in order to analyze its association with clinicopathologic factors and overall survival of patients.

Material and Methods

Clinical data and primary lesions of HNSSC were collected from 55 patients who underwent surgical resection with postoperative radiotherapy in Montes Claros, state of Minas Gerais, Brazil, between 2000 and 2008. Immunohistochemical reactions were performed to analyze MSH2 protein expression.

Results

Bivariate analysis showed no significant correlation or association between MSH2 expression and clinicopathologic parameters by Mann-Whitney and Kruskal-Wallis tests. Patients with locoregional metastatic disease (OR=4.949, p<0.001) and lower MSH2 immunohistochemical expressions (OR=2.943, p=0.032) presented poorer survival for HNSCC by Cox regression models.

Conclusions

Our data demonstrated that lower MSH2 expression might contribute to a higher clinic aggressiveness of HNSCC by promoting an unfavorable outcome.

MLH1 as a direct target of MiR-155 and a potential predictor of favorable prognosis in pancreatic cancer

BACKGROUND

The regulation of Mut L homologue 1 (MLH1) expression by microRNA (miR)-155 and its prognostic significance in pancreatic cancer (PC) remain to be elucidated. This study aimed to address the issues.

METHODS

MiR-155 mimics and inhibitor were transfected to PC cell lines, Panc-1 and Capan-1. Expression of MLH1 was subsequently evaluated. Then, luciferase activity was detected after miR-155 mimics and pRL-TK plasmids containing wild-type and mutant 3'UTRs of MLH1 mRNA were co-transfected. Finally, immunohistochemical staining for MLH1 was performed in PC samples.

RESULTS

Transfection of miR-155 mimics and inhibitor led to reversely altered protein expressions of miR-155 and MLH1, whereas the corresponding mRNA expressions were similar. A significant decrease in luciferase activity in the cells transfected with the wild-type pRL-TK plasmid was shown in contrast to those transfected with the mutant one. In addition, MLH1 was less expressed in tumor than in para-tumor tissues of PC. Extensive MLH1 expression was significantly associated with favorable differentiation and less lymph node metastasis. MLH1 expression was found to be a prognosticator in univariate analysis, and being of marginally significant impact in multivariate test.

CONCLUSIONS

MLH1 might serve as a direct target of miR-155 and a potential prognosis predictor in PC.

Immunophenotypic evaluation of DNA mismatch repair markers in 2 cases of synchronous histomorphologically distinct gastric adenocarcinomas with gastrointestinal stromal tumors of the proximal small bowel

OBJECTIVES

To assess the prognostic value of combined mismatch DNA repair (MMR) phenotyping in 2 synchronous histomorphologically distinct gastric adenocarcinomas (GADCs), each accompanied by gastrointestinal stromal tumors (GISTs) of the proximal small bowel.

SUMMARY BACKGROUND DATA

A 72-year-old female and a 55-year-old male patient were submitted to partial and total gastrectomy, respectively, with synchronous resection of a GIST in the proximal small bowel. The 2 patients attained contrasting survival outcomes. The female survives disease-free 20 months after surgery having received no chemotherapy. The male who received adjuvant chemotherapy developed metastases in liver and lung, and died 18 months after surgery.

METHODS

We phenotype MSH2 and MLH1 protein expression in tumor relative to matched normal tissue by immunohistochemistry.

RESULTS

Immunohistochemistry analysis revealed different combined MMR phenotypes for the 2 histomorhologically distinct GADCs and similar for both GISTs studied.

CONCLUSIONS

Good and bad prognosis for disease-free survival of patients based on reduced and elevated combined MMR phenotypic expression of the 2 histomorphologically distinct GADCs, could be explained by disease-associated emergence of genomic MMR alterations in the tumor. The impact of synchronous GISTs with common intermediate MMR phenotypes on patient survival is rather incidental and secondary to predominating GADCs.

Significance of mismatch repair genes hMLH1 and hMSH2 expression in gastric cancer

AIM: To investigate the role of mismatch repair genes human mutL homolog 1 (hMLH1) and human mutL homolog 2 (hMSH2) in the carcinogenesis of gastric cancer.

METHODS: A total of 40 gastric cancer patients who underwent surgical resection at our hospital were included in the study, of which 33 were pathologically diagnosed as adenocarcinoma, and 7 as mucinous adenocarcinoma. All the patients did not underwent preoperative chemotherapy or immunotherapy. The gastric cancer specimens, matched cancer-adjacent tissue specimens, and 20 chronic gastritis mucosa specimens (10 diagnosed as chronic superficial gastritis by gastroscopic biopsy, and 10 as chronic atrophic gastritis) were collected. The expression of hMLH1 and hMSH2 proteins in these specimens was detected by Western blot.

RESULTS: The positive rate of hMSH2 expression in cancer tissue was significantly higher than those in cancer-adjacent tissue and gastritis mucosa tissue (0.28 ± 0.10 vs 0.23 ± 0.07 and 0.11 ± 0.10, respectively; both P < 0.01). The positive rate of hMLH1 expression in cancer tissue was significantly lower than those in cancer-adjacent tissue and gastritis mucosa tissue (0.22 ± 0.06 vs 0.28 ± 0.07, 0.26 ± 0.06, both P < 0.01). The positive rates of hMLH1 and hMSH2 expression were not correlated with various clinicopathological parameters in gastric cancer.

CONCLUSION: High hMSH2 expression and low hMLH1 expression may be potential markers for prediction of the development of gastric cancer.

Importance of MutL homologue MLH1 and MutS homologue MSH2 expression in Turkish patients with sporadic colorectal cancer

AIM: To assess the incidence of MLH1 (the human MutL homologue) and MSH2 (the human MutS homologue) protein expression in Turkish patients with sporadic colorectal cancers and to compare their survival and clinicopathological features.

METHODS: We validated the tissue microarray technology in 77 colorectal carcinomas by analyzing the immunohistochemical expression of proteins involved in two main pathways of colorectal carcinogenesis: p53 protein for loss of heterozygosity tumors; MLH1 and MSH2 proteins for microsatellite instability (MSI).

RESULTS: Our analysis showed that 29 (39.2%) had loss of MLH1 expression, 5 (6.8%) had loss of MSH2 expression and 2 cases had loss of expression of both proteins. We found that 60% of MSH2-negative tumors were located in the right side of the colon; all MSH2-negative cases were women. In addition, the loss of MSH2 expression was correlated with low p53 expression. Neither MLH1 nor MSH2 expressions were associated with prognosis, although there seemed a tendency of longer survival (71.7 ± 8.65 mo vs 47.08 ± 5.26 mo) for the patients with MLH1-negative versus MLH1-positive carcinomas. There were not significant differences in overall and recurrence-free survival among MLH1/MSH2-positive and -negative cases.

CONCLUSION: Our data supports that Turkish patients with MLH1- and MSH2-defective tumors have some distinct features from each other. Although prognostic importance remains controversial, immunohistochemical analysis of mismatch repair genes may be used as a routine histopathological examination of sporadic colorectal carcinomas.

ASCO 2006 Update of Recommendations for the Use of Tumor Markers in Gastrointestinal Cancer

Purpose

To update the recommendations for the use of tumor marker tests in the prevention, screening, treatment, and surveillance of gastrointestinal cancers.

Methods

For the 2006 update, an update committee composed of members from the full Panel was formed to complete the review and analysis of data published since 1999. Computerized literature searches of Medline and the Cochrane Collaboration Library were performed. The Update Committee's literature review focused attention on available systematic reviews and meta-analyses of published tumor marker studies.

Recommendations and Conclusion

For colorectal cancer, it is recommended that carcinoembryonic antigen (CEA) be ordered preoperatively, if it would assist in staging and surgical planning. Postoperative CEA levels should be performed every 3 months for stage II and III disease for at least 3 years if the patient is a potential candidate for surgery or chemotherapy of metastatic disease. CEA is the marker of choice for monitoring the response of metastatic disease to systemic therapy. Data are insufficient to recommend the routine use of p53, ras, thymidine synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, microsatellite instability, 18q loss of heterozygosity, or deleted in colon cancer (DCC) protein in the management of patients with colorectal cancer. For pancreatic cancer, CA 19-9 can be measured every 1 to 3 months for patients with locally advanced or metastatic disease receiving active therapy. Elevations in serial CA 19-9 determinations suggest progressive disease but confirmation with other studies should be sought. New markers and new evidence to support the use of the currently reviewed markers will be evaluated in future updates of these guidelines.

Immunohistochemical test for MLH1 and MSH2 expression predicts clinical outcome in stage II and III colorectal cancer patients

PURPOSE

To evaluate the prognostic significance of DNA mismatch repair (MMR) status in a large series of stage II and III colorectal cancer patients. The relationship among MMR status, adjuvant chemotherapy, and clinical outcome was also investigated.

PATIENTS AND METHODS

The study included 718 patients with colorectal adenocarcinoma (393 stage II and 325 stage III) who underwent curative surgical resection. MMR status was determined by immunohistochemical analysis of MLH1 and MSH2 expression. Microsatellite instability (MSI) was assessed in 363 patients using mononucleotide and dinucleotide markers.

RESULTS

One hundred fourteen (15.9%) carcinomas showed abnormal MMR protein (MMRP) expression (96 MLH1 negative and 18 MSH2 negative) and were classified as MMRP negative, whereas 604 tumors demonstrated normal MLH1/MSH2 immunoreactivity (MMRP positive). MLH1/MSH2 expression was closely related to MSI status (P < .001) and several clinicopathologic features. Patients with MMRP-negative carcinomas demonstrated a marked reduction in the risk of cancer-related death with respect to patients with MMRP-positive tumors (hazard ratio, 0.2579; 95% CI, 0.1289 to 0.5159). A better clinical outcome for patients with MMRP-negative tumors was observed in both stage II (P = .0006) and stage III (P = .0052) disease. In stage III disease, the survival advantage conferred by MMRP-negative tumors was more evident among patients treated with surgery alone than among patients who received adjuvant chemotherapy. A nonsignificant trend for survival benefit from adjuvant chemotherapy was observed among patients with MMRP-positive carcinomas but not among those with MMRP-negative carcinomas.

CONCLUSION

Immunohistochemical testing for MLH1/MSH2 expression provides useful prognostic information for the management of stage II and III colorectal cancer patients.

Systematic review of genetic influences on the prognosis of colorectal cancer

Background

In terms of genetics, colorectal cancer is one of the best understood of all malignant diseases. Genetic influences on prognosis may have far-reaching implications, especially for the design of surgical and chemoradiotherapeutic regimens. However, their significance in determining prognosis remains unclear. This study aimed to review the literature on the specific role of key genes in determining the survival of patients with colorectal cancer.

Methods

A Medline search was carried out to identify all original scientific papers relating colorectal cancer genetics to patient survival, up to December 2002. Cochrane and Embase databases were also searched. Identified articles were retrieved and searched carefully for additional information. This review includes K-ras, p53, DCC, NM23 and DNA mismatch repair genes.

Results and conclusion

Conflicting evidence exists as to the prognostic significance of genes commonly implicated in the pathogenesis of colorectal carcinoma. Possible causes for such discrepancy include differences in study methods and laboratory techniques, variable duration of follow-up, statistical differences in study power, and heterogeneity in study populations. Future studies should adopt standardized protocols to define clinically relevant genetic observations.

Deleted in oral cancer-1 expression upregulates proapoptosis elements in microsatellite-unstable human colorectal cancer

BACKGROUND

We previously reported differential expression of the growth suppressor, deleted in oral cancer-1 (DOC-1), in microsatellite-unstable (MSI+) versus microsatellite-stable colorectal cancer (CRC) cell lines. MSI+ CRC cell lines demonstrated decreased DOC-1 expression and decreased apoptosis. Transfection of wild-type DOC-1 into an MSI+ cell line (SW48) resulted in increased apoptosis. We undertook our current experiment to identify specific elements modulated by DOC-1 expression that result in increased apoptosis.

METHODS

SW48 is an MSI+ CRC cell line that does not constitutively express DOC-1. SW48 was suspended in culture medium and incubated to 60% confluence. Half the plates were transfected with cytomegalovirus (CMV)-DOC-1. At 30 hours, RNA and protein were isolated with Trizol. Complementary DNA microarray was performed to compare SW48(CMV-DOC-1) with SW48, which lacks DOC-1. Signal intensity was analyzed by GenePix Pro 3.0 software. Expression ratios </=.67 and >/ 1.5 were considered significant. Poor-quality spots were flagged and excluded from analysis. Real-time polymerase chain reaction was performed to determine DOC-1 levels in both cell lines.

RESULTS

Successful transfection of DOC-1 was confirmed by real-time polymerase chain reaction and by Western blot. Microarray revealed significant differential expression of DOC-1, as expected. Increased DOC-1 expression in SW48(CMV-DOC-1) was associated with significantly increased expression of proapoptosis components of the caspase cascade (CASP7, CASP9) and bcl2/bax pathway (BNIP3, BNIP3L, BID).

CONCLUSIONS

DOC-1 expression promotes apoptosis by upregulation of specific elements of the caspase cascade and bcl2/bax pathways. DOC-1 therefore deserves further study as a candidate for the therapeutic modulation of apoptosis in MSI+ CRC.

Histopathology and mismatch repair status of 458 consecutive colorectal carcinomas

Defects in the mismatch repair (MMR) genes hMLH1 and hMSH2 have been found in 10% to 20% of sporadic colorectal carcinomas and also many cases of hereditary nonpolyposis colorectal cancer syndrome. Patients with these tumors have an improved prognosis and may show greater sensitivity to chemotherapy. We examined 458 resected colorectal carcinomas from 430 consecutive patients and used immunohistochemistry to determine which tumors lacked expression of these genes (MMR-d). We correlated the status of MMR-d or "intact" expression with stage, site, and histology. Eighty-nine of 458 tumors (19.4%) were MMR-d, including 80 hMLH1 and 9 hMSH2 tumors. A total of 6% of patients had synchronous tumors, and 37.7% of these were MMR-d (P=0.0008). A high proportion of patients with previous breast cancer (4 of 6 patients) had hMLH1-defective colorectal carcinomas. MMR-d tumors presented at an earlier stage than intact tumors, and the node-positive MMR-d tumors were less likely than intact tumors to have pericolonic extranodal tumor deposits (18.2% vs. 44%). The proportion of tumors at each site that were MMR-d increased progressively from cecum (32%) to ascending (35%) to transverse colon, where 41% of all tumors were defective. The proportions then rapidly decreased, reaching the lowest rate (4.7%) in the rectum. Both types of MMR-d tumors more often had expansive borders, intraepithelial lymphocytosis, peritumoral lymphoid, and Crohn's-like lymphoid responses than the intact tumors; the frequencies of these features diminished with advancing stage. Tumor budding was less common in stage II and III MMR-d tumors than in intact tumors. Keloid and myxoid type stromas correlated with stage and vascular invasion and were not related to mismatch repair status. Significant differences existed between the hMLH1 and hMSH2 tumors. The reported right-sided preponderance of MMR-d tumors is due to most hMLH1, but not hMSH2, tumors being found there (87.5% vs. 44.4%). hMSH2 tumors were most common in the rectum (55.6%). Mucinous tumors were common in hMLH1 tumors (36.3%) but not in hMSH2 tumors (11.1%). hMLH1 tumors were most likely to be poorly differentiated (70%), which was uncommon with hMSH2 tumors (22.2%). hMSH2 tumors were more likely to be confined to the wall (66.7%) than hMLH1 (20%) or intact tumors (23%). We conclude that hMLH1 and hMSH2-defective tumors have distinctly differing histologic features from each other.

Differential expression of DOC-1 in microsatellite-unstable human colorectal cancer

The precise genetic mechanism of malignant transformation in DNA mismatch repair deficient, microsatellite-unstable colorectal cancer (CRC) has yet to be elucidated. We employed cDNA microarray to identify patterns of gene expression among CRC cell lines and to compare directly lines with and without microsatellite instability. This study was undertaken to test the hypothesis that microsatellite-unstable CRC cell lines demonstrate specific patterns of gene expression that differ significantly from those observed among microsatellite-stable CRC. Multiple differential expression patterns were identified. Genes demonstrating differential expression included deleted-in-oral-cancer-1 (DOC-1), a highly conserved growth suppressor. DOC-1 expression correlated with microsatellite status, with significantly decreased expression in microsatellite-unstable cell lines and constitutive expression in microsatellite-stable cell lines. We also observed alterations in the biologic behavior of p12(DOC-1)-deficient cell lines, with increased S phase and decreased apoptosis compared to microsatellite-stable (DOC-1+) cell lines. Transfection of p12(DOC-1) into SW48, which lacks p12(DOC-1) expression, resulted in cell cycle and apoptosis profiles similar to other p12(DOC-1)+ cell lines. These results support the hypothesis that microsatellite-unstable CRC is characterized by novel patterns of gene expression different from those associated with microsatellite-stable CRC, and demonstrate that p12(DOC-1) has tumor suppressor potential in colon epithelial cells.

Prognostic molecular markers for planning adjuvant chemotherapy trials in Dukes' B colorectal cancer patients: how much evidence is enough?

The benefit of postoperative adjuvant chemotherapy in patients with Dukes' B colorectal cancer is still uncertain and its routine use is not recommended. Prognostic biomarkers may be useful for identifying high-risk patients with resected, node-negative disease, and this stratification may represent an innovative strategy for designing adjuvant chemotherapy trials. Featured prognostic molecular markers can be divided into the following categories: cell proliferation indices (Ki-67, Mib-1, proliferating cell nuclear antigen); oncogenes/tumor suppressor genes [p53, K-ras, Deleted in Colorectal Cancer (DCC), Bcl-2, c-erbB2]; DNA repair (microsatellite instability); markers of angiogenesis (vascular count, vascular endothelial growth factor); markers of invasion/metastasis (plasminogen-related molecules, matrix metalloproteinases); and biochemical markers (thymidylate synthase). Studies that have investigated their prognostic role in Dukes' B colorectal cancer patients are reviewed here. Current data do not provide sufficient evidence for the incorporation of available prognostic biomarkers into clinical practice. However, a biomarker-based approach could be an effective strategy for improving results of postoperative adjuvant treatments in high-risk Dukes' B colorectal cancer patients. Markers of altered DCC function have shown promising prognostic role and sufficient prevalence in retrospective investigations and they deserve further assessment in prospective studies.