hMLH1 Expression Research Articles

Defective mismatch repair and the development of recurrent endometrial carcinoma

Objective. To investigate whether defective DNA mismatch repair (MMR) defines a subgroup at risk for recurrence in sporadic endometrial carcinoma patients. Methods. Primary tumors from 44 patients with recurrent stage I endometrial carcinoma were compared after matching, with tumors of 44 patients being free of recurrence for minimal 3 years. Paraffin-embedded primary tumors ( n = 88) and recurrent tumors ( n = 32) were subjected to immunohistochemical analysis for hMSH2 and hMLH1 expression. Subsequently, a staining index (SI = 0–9) was calculated based on staining intensity and quantity. DNA was extracted from paraffin-embedded tissues, and promoter methylation of hMLH1 was determined by nested methylation-specific PCR (MSP). Microsatellite instability (MSI) was assessed by BAT-26 or BAT-25. Results. Low hMSH2 expression was observed in 2% of primary tumors of control patients without recurrence, 14% of primary tumors of patients with recurrence, and 0% of recurrent tumors. Low hMLH1 expression was observed in 32%, 19%, and 22%, respectively. hMLH1 gene promoter methylation was detected in 50%, 47%, and 32%, and MSI was found in 16%, 14%, and 30%, respectively. No significant differences were found between primary tumors of patients with and without recurrence with respect to hMSH2 and hMLH1 expression, hMLH1 promoter methylation, and MSI. When primary and recurrent tumors were compared, there was an increased correlation of hMLH1 methylation with low hMLH1 expression and MSI in recurrent tumors. Conclusion. MSI, hMLH1 promoter methylation, and the expression of hMLH1 and hMSH2 are not predictive for the development of recurrent stage I endometrial carcinoma. In the progression of tumor, “de novo” hMLH1 methylation rarely occurs, instead there is further derailment of the MMR pathway in affected tumors.

Microsatellite instability and alteration of the expression of hMLH1 and hMSH2 in ovarian clear cell carcinoma

Microsatellite instability (MSI) is commonly seen in tumors associated with the hereditary nonpolyposis colorectal cancer syndrome and is caused by defects in the DNA mismatch repair genes. MSI has also been observed in various sporadic cancers, including colorectal, gastric, and endometrial. The role and incidence of MSI in ovarian clear cell carcinoma remain unknown. This study was conducted to evaluate the frequency of MSI in ovarian clear cell carcinomas and to evaluate the sensitivity and specificity of immunohistochemistry in predicting mismatch-repair gene deficiency. A total of 42 ovarian clear cell carcinomas were analyzed for MSI using a panel of 5 microsatellite markers ( BAT25, BAT26, D5S346, D2S123, and D17S250). Alterations in the expression of hMLH1 and hMSH2 proteins in these tumors were examined. Of the 42 ovarian clear cell tumors analyzed, 6 demonstrated a high level of MSI (MSI-H), 3 demonstrated a low level of MSI (MSI-L), and the remaining 33 exhibited microsatellite stability (MSS). No correlation was found between MSI level and patient age or tumor stage or size ( P >0.05). Loss of expression of either hMLH1 or hMSH2 was observed in 4 of the 6 (67.7%) MSI-H tumors, whereas 34 of the 36 (94.4%) MSI-L or MSS tumors expressed both the hMLH1 and hMSH2 gene products. Our results indicate that MSI-H is involved in the development of a subset of ovarian clear cell carcinomas. A strong correlation exists between alterations in the expression of hMLH1 and hMSH2 and the presence of MSI-H in these tumors. However, immunohistochemical testing alone may miss a small fraction of cases with MSI-H.

Microsatellite instability in esophageal adenocarcinoma

The frequency of microsatellite instability (MSI), a result of defective mismatch repair during DNA replication, has been reported inconsistently in primary esophageal adenocarcinoma (EADC). Using a panel of 15 markers, the primary aim of this study was to analyze the frequency of MSI in a well-characterized series of 27 primary EADCs, defined according to strict clinicopathologic criteria. Polymerase chain reaction was used to amplify the following microsatellite repeat loci: D2S123, D10S197, D2S119, D11S904, D2S147, D3S1764, D7S1830, D7S1805, D2S434, D9S299, BAT25, BAT26, D5S346, D17S250, and TGF-β-RII. Tumors were classified as microsatellite-stable (MSS) when no alterations were seen in tumor DNA compared to matched normal tissues, low-level MSI (MSI-L) when 1–5 of 15 markers were altered, and high-level MSI (MSI-H) when more than five markers were altered. Using these stringent criteria, 9/27 (33%) tumors were MSS, 18/27 (67%) tumors were MSI-L, and no tumor was MSI-H. Immunohistochemistry demonstrated cell nuclear expression of DNA mismatch repair proteins (both hMLH1 and hMSH2) in 78% (21/27) of tumors. No associations were seen between MSI and immunohistochemical expression of hMLH1, hMSH2, alterations in p53 or MBD4, tumor grade, pathologic stage, or patient survival. In conclusion, the finding of low levels of MSI in most tumors suggests an inherent baseline genomic instability, and potentially increased susceptibility to mutations during the progression of esophageal adenocarcinoma.

Geno- and pheno-typic characterization in ten patients with double-primary gastric and colorectal adenocarcinomas.

Although a number of double-primary gastric and colorectal cancers have been known to correlate with the mutator pathway, a possible association with known hereditary cancers regarding geno-pathogenesis has rarely been investigated. This study was intended to identify a possible association of hereditary cancers and the implications of the mutator or tumor-suppressor pathway in double-primary gastric and colorectal cancers. Fresh colorectal tissues and lymphocytes from ten patients with double-primary gastric and colorectal cancers were obtained consecutively. The mutator pathway was evaluated by detecting hMSH2 and hMLH1 mutations, microsatellite instability (MSI) using 12 microsatellite markers, and hMLH1 promoter region methylation. Protein expressions of hMSH2, hMLH1, APC, E-cadherin, and beta-catenin were identified by immune staining. There was no pathogenic mutation in any introns or exons of hMSH2, hMLH1 or CDH1, and in exons 3, 5, 6, and 15 of CTNNB1. Either MSI or methylator phenotype was found in five gastric cancers and in four colorectal cancers. No patients met the Amsterdam criteria of hereditary nonpolyposis colorectal cancer (HNPCC) or its equivalent of hereditary gastric cancer. Two patients with gastric cancers among their first-degree relatives showed no E-cadherin expression. The two of the three patients with rectal cancers among their first-degree relatives showed mutator phenotype either in the gastric or in the colorectal cancer. A subset of double-primary gastric and colorectal cancers may thereby be categorized as variant forms of hereditary gastric or colorectal cancer. Both cytoplasmic and nuclear beta-catenins were expressed in all gastric and colorectal cancers. Among the gastric and colorectal cancers with either MSI or methylator phenotype, four of five gastric cancers showed both APC and E-cadherin expression, whereas one of four colorectal cancers showed them. This may suggest that the mutator pathway and the aberrant tumor suppressor pathway of the APC-E-cadherin may be cooperative or separately activated in the geno-pathogenesis of double-primary gastric and colorectal cancers.

In this issue

In this issue

Defective mismatch-repair colorectal cancer: clinicopathologic characteristics and usefulness of immunohistochemical analysis for diagnosis.

The purpose of our study was to determine the usefulness of immunohistochemical analysis for the diagnosis of mismatch-repair (MMR) gene defective colorectal tumors and to describe their prevalence and clinicopathologic characteristics. We studied 172 cases. DNA was extracted from formalin-fixed, paraffin-embedded surgical samples, and microsatellite analysis was performed by polymerase chain reaction with BAT-26. The results were correlated with immunohistochemical analysis for hMLH1 and hMSH2. Microsatellite instability (MSI) was detected in 13 (7.6%) tumors, and all showed loss of protein expression of hMLH1 (11/13) or hMSH2 (2/13) (P < .000). Patients with MMR-defective tumors more frequently had poorly differentiated tumors (5/13 [38%] vs 18/159 [11.3%]; P = .02) located in the ascending colon (8/13 [62%] vs 30/159 [18.9%]; P < .0001) and a personal history of other neoplasms (4/13 [31%] vs 18/159 [11.3%]; P = .05). There were no differences in age, family history of cancer, or TNM stage. Immunohistochemical analysis seems to be a reliable method to detect most colorectal cancers with defective MMR genes.

Clinical analysis and molecular genetic study of hereditary nonpolyposis colorectal cancer kindreds

To study the clinicopathological and molecular genetic characteristics of hereditary nonpolyposis colorectal cancer (HNPCC), to enable the early diagnosis and to evaluate the treatment. We analyzed 12 families of HNPCC from Wenzhou, Zhejiang province, China. Mismatch repair genes hMSH2 and hMLH1 expression and microsatellite instability of tumor tissue were studied using microdissection, microsatellite analysis, immunohistochemical staining and Gene Scan analysis. Direct DNA sequencing of hMSH2 and hMLH1 were performed subsequently. Altogether 32 patients with colorectal cancer were recognized in 12 HNPCC families, with the median age of 45.2 years (75.0% before the age of 50 years). The proximal tumors accounted for 51.1%, while multiple colorectal cancers accounted for 34.4%. Poor differentiation cancers occupied half of the patients (53.1%). And 68.8% of the patients had the tumor of Dukes A and B. Among 12 HNPCC families, 7 cases in 6 HNPCC families developed extracolonic cancer. 13 cases died during follow up of 1 - 23 years. The median survival time was 6.4 years. 19 alive cases followed up from 1 to 28 years. All tumors (9/9) displayed microsatellite instability, with the half losing hMSH2 or hMLH1 expression. In the 5 genetic analyzed kindreds 3 possessed germline mutation. Two of three mutations have not been reported in the worldwide database previously. HNPCC showed distinct clinicopathological characteristics. Microsatellite instability analysis and immunohistochemical staining might be the effective screening methods before direct DNA sequencing for the detection of mutation in mismatch repair genes. It is important to analyze the members of affected families.

Correlation between patterns of DNA mismatch repair hmlh1 and hmsh2 protein expression and progression of dysplasia in intraductal papillary mucinous neoplasms of the pancreas.

Defective DNA mismatch repair results from genetic or epigenetic alterations that most frequently inactivate the genes hMLH1 and hMSH2. This is thought to promote tumourigenesis by accumulation of mutations in oncogenes and tumour suppressor genes. This pathway, first reported in colon cancer, has been recently demonstrated in a subgroup of sporadic pancreatic adenocarcinomas. Intraductal papillary-mucinous neoplasms of the pancreas are a special type of pancreatic tumours, characterised by a spectrum of morphological changes from mild to moderate and to non-invasive, and they may associate with adenocarcinoma. An immunohistochemical study of hmlh1 and hmsh2 protein expression was performed on 26 intraductal papillary-mucinous neoplasms. All tumours showed nuclear expression of hmlh1 and hmsh2 proteins. There were two distinctive patterns of protein expression on the basis of the location of cells expressing these markers: the "normal" pattern, observed mainly in adenoma and rarely in intraductal papillary-mucinous neoplasms with moderate dysplasia and the "dysplastic" pattern, frequently encountered in moderate dysplasia neoplasms, non-invasive and invasive carcinomas. These findings suggest that defective DNA mismatch repair, due to inactivation of hMLH1 and hMSH2, does not play a significant role in the pathogenesis of intraductal papillary-mucinous neoplasms of the pancreas. Two patterns of protein expression were observed and were correlated with the progression of dysplasia in intraductal papillary mucinous neoplasms.

Hypermethylation of the hMLH1 promoter with absent hMLH1 expression in medullary-type poorly differentiated colorectal adenocarcinoma in the elderly

To clarify the significance of hMLH1 promoter hypermethylation in the development of medullary-type poorly differentiated colorectal adenocarcinoma, we studied the status of promoter methylation and hMLH1 expression in 23 medullary-type and 12 pleomorphic-type carcinomas, as well as the pathology and microsatellite status. In medullary-type carcinomas, the percentages of cases with promoter methylation (83%) and an absence of hMLH1 expression (91%) were significantly higher than in pleomorphic-type carcinomas (14 and 17%), respectively. The rate of microsatellite instability in the medullary type was significantly higher than that of the pleomorphic type (87 vs 40%, P<0.01). Compared with pleomorphic-type carcinomas, medullary-type carcinomas were significantly associated with hMLH1 promoter methylation, absent expression of hMLH1 protein, microsatellite instability, as well as a proximal location, a Crohn's-like lymphoid reaction, a low incidence of lymph node metastasis, and a favorable outcome. Medullary-type carcinomas accumulated with advancing age, especially in the female. These results indicated that hMLH1 hypermethylation, concurrent with a lack of its protein expression, may play an important role in the development of medullary-type poorly differentiated colorectal adenocarcinomas in the elderly.

Clinicopathological significance of microsatellite instability and mutated RIZ in colorectal cancer

Several studies have shown that microsatellite instability (MSI) is related to favourable survival in colorectal cancer patients but there are controversial results. Tumour suppressor gene RIZ is a susceptible mutational target of MSI. However, its clinicopathological significance has not been investigated. We investigated the prognostic significance of MSI in Swedish colorectal cancer patients and the clinicopathological significance of RIZ mutations. We analysed 438 colorectal adenocarcinomas for MSI by microsatellite analysis. Among them, 29 MSI and 28 microsatellite stable (MSS) tumours were examined for RIZ mutations by DNA sequencing. MSI (13% of 438 cases) was not associated with survival (rate ratio = 0.97, 95% confidence interval = 0.57-1.64, P = 0.90), although it was related to proximal tumour (P <0.001), poor differentiation and mucinous carcinomas (P <0.001), multiple tumours (P = 0.01) and negative/weak expression of hMLH1 (P = 0.03). RIZ mutations were detected in 31% of 29 MSI tumours but in none of the 28 MSS tumours. The mutations were related to female (P = 0.01), proximal tumour (P = 0.01), stage B (P = 0.01) and poor differentiation (P = 0.047). MSI was not a prognostic factor in the Swedish patients included in this study. Clinicopathological variables associated with RIZ mutations might be a consequence of the MSI characteristics.

Microsatellite instability predicts poor short-term survival in patients with advanced breast cancer after high-dose chemotherapy and autologous stem-cell transplantation.

The purpose is to define molecular prognostic factors in patients with advanced breast cancer treated with high-dose chemotherapy (HDCT) and autologous stem cell transplantation (ASCT). Thirty-nine patients with breast cancer and extensive lymph node (level III) and/or systemic metastases from a prospective single-center study of sequential HDCT/ASCT were studied. Microsatellite analysis was performed after laser microdissection using 15 markers selected for sensitive detection of microsatellite instability (MSI) in breast cancer. Exons 5-9 of the P53 gene were directly sequenced. Expression of P53, HER-2/neu, and the mismatch repair proteins hMSH2 and hMLH1 was evaluated by immunohistochemistry. MSI of at least three markers was detected in 13 of 39 patients (33%) and was predominantly found at tetranucleotide markers. All MSI-positive tumors showed normal expression of hMSH2 and hMLH1. Complete sequence analysis of exons 5-9 of the P53 gene was successful in 34 cases; 18% (n = 6) revealed a mutation. Overexpression of HER-2/neu and P53 was observed in 7 (22%) and 12 (46%) of 26 evaluated cases, respectively. The presence of MSI strongly correlated with shorter overall survival (OS; P = 0.0004) and progression-free survival (PFS; P = 0.02). None of the other investigated clinical or molecular factors correlated with OS in univariate analyses, with the exception of menopausal status and previous adjuvant chemotherapy. Testing various multivariate Cox regression models, MSI remained a highly significant, independent, and adverse risk factor for OS. MSI is frequent in advanced breast cancer and could be an indicator of chemotherapy resistance and poor prognosis in breast cancer patients treated with HDCT/ASCT.

Evaluation of Microsatellite Instability, hMLH1 Expression and hMLH1 Promoter Hypermethylation in Defining the MSI Phenotype of Colorectal Cancer

About 10-15% of all colorectal cancers (CRCs) demonstrate high levels of microsatellite instability (MSI-H) and are currently best identified by molecular analysis of microsatellite markers. Most sporadic CRCs with MSI-H are known to be associated with the methylation of the hMLH1 promoter. Promoter methylation coincides with lack of the hMLH1 expression. We aimed to investigate the association between MSI status, hMLH1 protein expression and methylation status of the hMLH1 promoter, and to determine the usefulness of each method in defining the MSI phenotype in sporadic CRCs. Methods: CRCs from 173 patients from the Cancer and Leukemia Group B (CALGB) were assessed for their MSI status. An additional cohort of 18 MSI-H tumors from the University of California San Diego (UCSD) was included in the analysis of the MSI-H subgroup. MSI testing was performed by PCR using five standard MSI markers. hMLH1 promoter analysis was investigated by methylation specific PCR (MSP), and expression of the MMR genes hMLH1 and hMSH2 was examined by immunohistochemistry (IHC). Results: Of the 173 CALGB tumors, 111 (64%) were MSS, 35 (20%) were MSI-L and 27 (16%) MSI-H, respectively. Data on hMLH1 protein expression, MSH2 protein expression and hMLH1 methylation are available on 128, 173 and 81 of these tumors, respectively. Presence of hMLH1 and hMSH2 protein expression was significantly associated with MSI status. Four of 45 (8.9%) MSI-H tumors and 0 of 146 (0%) MSS/MSI-L tumors did not express hMSH2 (p=0.0028). hMLH1 protein expression was present in 107 of 108 (99%) MSS and MSI-L tumors versus 11 of 20 (55%) MSI-H tumors (p

Responsiveness of CPT-11 in Respect to hMLH1 and hMSH2 Protein Expression in the Primary Colorectal Cancer

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

Microsatellite instability and expression of hMLH1 and hMSH2 proteins in ovarian endometrioid cancer

Microsatellite instability and loss of heterozygosity has been implicated in ovarian carcinogenesis. The reported frequency of microsatellite instability in human ovarian cancer varies significantly owing to the use of heterogeneous tumor histotypes and various microsatellite markers in different laboratories. In this study, we determined the frequency of microsatellite instability in 74 ovarian endometrioid carcinomas using four microsatellite markers (BAT25, BAT26, D5S346, D17S250), and examined hMLH1 and hMSH2 protein expression. In all, 20% of the tumors were microsatellite instability high (two or more markers showing instability) and 12% were microsatellite instability low (one marker showed instability). Loss of hMLH1 and/or hMSH2 expression was found in nine of 15 microsatellite instability-high tumors. The microsatellite instability-high phenotype tended to occur more frequently in low-grade tumors (P=0.053), but did not correlate with clinical stage. Totally, 38% of cases also displayed loss of heterozygosity at D17S250; this loss of heterozygosity was associated with high clinical stage (P=0.097). Our results indicate that both microsatellite and loss of heterozygosity at D17S250 are involved in the development of ovarian endometrioid carcinoma.

Analysis of Microsatellite Instability and hMLH1, hMSH2 and Bax Expression in Sporadic Endometrioid Endometrial Adenocarcinoma

Objective : We aimed to assess the incidence and clinicopathologic significance of microsatellite instability (MSI) and to analyze the loss of protein expression of hMLH1, hMSH2 and Bax gene in endometrioid endometrial adenocarcinoma. Methods : A total of 30 patients with pure endometrioid type of endometrial adenocarcinoma were examined. MSI analysis was done using five polymorphic markers (BAT26, D5S346, BAT25, D17S250, D2S123) and the protein expression of hMLH1, hMSH2 and Bax gene was determined using immunohistochemical staining. Results : MSI was detected in 30% (9/30) of endometrioid endometrial adenocarcinoma. There was a significant correlation between MSI status and loss of hMLH1, hMSH2 and Bax expression (p0.05). But there were significant correlations between loss of hMLH1 and histological grade and lymph-vascular space invasion of endometrial adenocarcinoma (p0.05). Conclusions : According to the results, MSI and loss of protein expression of hMLH1, hMSH2 and Bax could be associated with the pathogenesis of sporadic endometrioid endometrial adenocarcinoma. In addition, hMLH1 might have a role as a prognostic parameter. Further prospective study with a large number of cases is needed in future.

Adenocarcinoid of the appendix vermiformis — A case report

We tested three mononucleotide, 45 dinucleotide, and five tetranucleotide repeats in 30 gastric adenomas and 30 gastric carcinomas for microsatellite instability (MSI) in order to evaluate which microsatellites might indicate the MSI status in gastric neoplasms. Along with the increase in tested markers, the proportion of low-frequency MSI (MSI-L) tumors increased. On immunohistochemistry, MSI-L gastric neoplasms did not show any alteration in hMLH1 or hMSH2 protein expression, while most of the high-frequency MSI (MSI-H) tumors did show alterations in the above mismatch repair proteins. The above findings suggested that MSI-L tumors cannot be distinguished from microsatellite stable tumors. Two mononucleotides, BAT25 and BAT26, were sufficient for the screening of MSI. An additional three dinucleotides, D17S786, D6S105 and D19S188, were also highly sensitive and specific in identifying MSI phenotype tumors.

Colorectal cancer without high microsatellite instability and chromosomal instability--an alternative genetic pathway to human colorectal cancer.

At least two forms of genomic instability have been described in colorectal cancers (CRCs): microsatellite instability (MIN), which is characterized by a high frequency of microsatellite instability (MSI-H) and chromosomal instability (CIN), which is characterized by losses and gains of chromosomes (aneuploidy), as well as chromosome rearrangements. Morphological and molecular heterogeneity within MIN(-) CRCs have been described, but the distinctions between MIN(-) tumors with CIN and those without CIN remain largely unknown. We studied 179 colorectal cancers to elucidate the clinicopathological characteristics and molecular events in CRCs arising along these pathways. Loss of heterozygosity, MIN, DNA content, mutation of p53 and K-ras, and expression of p53, hMLH1 and hMSH2 were examined. We found that a subtype of tumors (17%) with MIN(-) and CIN(-), differed from MIN(-)CIN(+) tumors with respect to clinicopathological and genetic characteristics. This subtype was associated with a greater frequency of poorly differentiated and/or mucinous tumors (26%). This subtype of tumors had an extremely low p53 gene mutation rate (11%) and a relatively high p53 protein accumulation rate (55%). The dissociation between the p53 gene mutation and protein accumulation suggests that stabilization of p53 protein in the absence of p53 gene mutation may be an important event on a distinct pathway.

Hypermethylation of the hMLH1 promoter with absent hMLH1 expression in medullary-type poorly differentiated colorectal adenocarcinoma in the elderly

Hypermethylation of the hMLH1 promoter with absent hMLH1 expression in medullary-type poorly differentiated colorectal adenocarcinoma in the elderly

Mismatch repair-dependent transcriptome changes in human cells treated with the methylating agent N-methyl-n'-nitro-N-nitrosoguanidine.

DNA mismatch repair (MMR) plays a key role in the cytotoxic response of human cells to methylating agents, however, the cascade of events leading to cell cycle arrest and cell death has yet to be characterized. We studied the role of MMR in the transcriptional response to DNA methylation damage in two human cellular models: (a). the lymphoblastoid cell line TK6 and its derivative MT1, which is mutated in the MMR gene hMSH6; and (b). the epithelial cell line 293T Lalpha in which the expression of the MMR gene hMLH1 can be tightly regulated and p53 is inactivated. Upon N-methyl-N'-nitro-N-nitrosoguanidine treatment, only cells with functional MMR were killed, but the type of cytotoxic response differed. In TK6 cells, S-phase arrest and apoptosis were accompanied by a dramatic change in gene expression, notably, an up-regulation of several genes encoding growth inhibitors and proapoptotic factors both p53 dependent and independent. In contrast, the MMR-dependent transcriptional response in 293T Lalpha cells was substantially less pronounced than in TK6 cells, despite an efficient induction of a G(2)-M checkpoint and nonapoptotic cell death. Thus, we demonstrate that in human cells of different origin, MMR-mediated killing by methylating agents occurs through different pathways and regardless of the p53 status. Moreover, once DNA methylation damage has been processed by the MMR system, tumor cells might be committed to die, although one or more of their signaling pathways are impaired.

Immunohistochemical analysis of adenocarcinoma of the small intestine: a tissue microarray study

Background: Primary adenocarcinomas of the small intestine are rare, and the genetic mechanisms involved in their carcinogenesis remain unclear. Aim: To examine the expression of candidate proteins in small intestinal...