The clinical importance and prognostic implications of microsatellite instability in sporadic cancer

Prognostic factors and survival outcomes of immunohistochemically detection based-molecular subtypes of endometrial cancer-analysis of 576 clinical cases

OBJECTIVE

The study aimed to identify distinct molecular subtypes of endometrial cancer (EC) by immunohistochemistry and to analyze their pathological characteristics, independent prognostic factors, and patient survival outcomes for potential clinical applications.

METHOD

576 patients with preoperative EC confined to the uterus were divided into three subgroups based on the immunohistochemical detection method: MMR-deficiency (MMRd), P53 wild type (P53wt) and P53 abnormal (P53abn). These subgroups were retrospectively analyzed, and their pathological characteristics, prognostic factors and survival outcomes were compared.

RESULTS

We identified 401 (69.6%), 123 (21.4%), and 52 (9%) cases of P53wt, MMRd, and P53abn subgroups, respectively. A significant difference was observed in the median age of onset, tumor stage, high-grade tumor differentiation, non-endometrioid carcinoma, myometrial invasion, lymphovascular invasion, the incidence of lymph node metastasis postoperative, and expression of ER and PR receptors among the three groups. Pathological type, lymphovascular invasion, ER and PR expression were identified as independent prognostic factors for disease-free survival (DFS). Additionally, pathological type, lymphovascular invasion, myometrial invasion, and PR expression were recognized as independent prognostic factors for overall survival (OS) in the study cohort. However, the survival outcome for P53abn was the worst, with lymphovascular invasion identified as an independent prognostic factor for DFS. Lymph node status, FIGO stage, and ER expression were identified as independent prognostic factors for OS.

CONCLUSION

The study concludes that immunohistochemical detection-based subtyping of EC holds clinical practicality and can be employed to explore both pathological and clinical prognoses for EC patients.

Predictive Biomarkers and Resistance Mechanisms of Checkpoint Inhibitors in Malignant Solid Tumors

Predictive biomarkers for immune checkpoint inhibitors (ICIs) in solid tumors such as melanoma, hepatocellular carcinoma (HCC), colorectal cancer (CRC), non-small cell lung cancer (NSCLC), endometrial carcinoma, renal cell carcinoma (RCC), or urothelial carcinoma (UC) include programmed cell death ligand 1 (PD-L1) expression, tumor mutational burden (TMB), defective deoxyribonucleic acid (DNA) mismatch repair (dMMR), microsatellite instability (MSI), and the tumor microenvironment (TME). Over the past decade, several types of ICIs, including cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors, anti-programmed cell death 1 (PD-1) antibodies, anti-programmed cell death ligand 1 (PD-L1) antibodies, and anti-lymphocyte activation gene-3 (LAG-3) antibodies have been studied and approved by the Food and Drug Administration (FDA), with ongoing research on others. Recent studies highlight the critical role of the gut microbiome in influencing a positive therapeutic response to ICIs, emphasizing the importance of modeling factors that can maintain a healthy microbiome. However, resistance mechanisms can emerge, such as increased expression of alternative immune checkpoints, T-cell immunoglobulin (Ig), mucin domain-containing protein 3 (TIM-3), LAG-3, impaired antigen presentation, and alterations in the TME. This review aims to synthesize the data regarding the interactions between microbiota and immunotherapy (IT). Understanding these mechanisms is essential for optimizing ICI therapy and developing effective combination strategies.

Single Center Characterization of a Cohort of Salivary Gland Carcinomas

Salivary gland cancer (SGC) is a rare cancer that can present a diagnostic challenge to pathologists, with emerging, but still limited options for the treatment of recurrent/metastatic disease. We aimed to characterize the cohort of salivary gland cancers in our institute and generate a tissue microarray (TMA) with clinical data available for immunohistochemical analysis. We extracted the cases of salivary gland cancers in our institute and generated a TMA with 72 patients between 2002 and 2017 with sufficient paraffin block material. Follow-up data were present for all cases. The TMA was stained with three p53 antibodies as well as MSH2, MSH6, PMS2 and MLH1 antibodies. Additionally, we applied fragment analysis based on the Bethesda panel, and the IdyllaTM MSI test to cases with expression loss of any of the mismatch repair proteins (MMR-P) according to our immunohistochemistry (IHC). The investigated cohort shows that pT and pN stage are the only factors independently associated with survival, according to our multivariate analysis (p = 0.037 and p = 0.014). In univariate analysis, risk factors identified in our cohort were also age (p = 0.015), (lympho-) vascular invasion (p = 0.002 and p = 0.003) and risk stratification (p = 0.037). The p53 protein investigated by three antibodies showed no statistically significant association with survival or other tumor characteristics in the investigated cohort. According to MMR-P IHC, six cases of SGC showed an aberrant IHC phenotype. Additional IdyllaTM MSI test and fragment length analysis failed to confirm microsatellite instability. The pT and pN stage are the most important factors for survival in our cohort. In our cohort, antibodies directed against the protein p53 did not contribute to clinical decision-making and were not correlated with any known clinical characteristics. MSI appears to be insignificant in SGCs. Larger cohorts are needed for verification.

Performance assessment of computational tools to detect microsatellite instability

Microsatellite instability (MSI) is a phenomenon seen in several cancer types, which can be used as a biomarker to help guide immune checkpoint inhibitor treatment. To facilitate this, researchers have developed computational tools to categorize samples as having high microsatellite instability, or as being microsatellite stable using next-generation sequencing data. Most of these tools were published with unclear scope and usage, and they have yet to be independently benchmarked. To address these issues, we assessed the performance of eight leading MSI tools across several unique datasets that encompass a wide variety of sequencing methods. While we were able to replicate the original findings of each tool on whole exome sequencing data, most tools had worse receiver operating characteristic and precision-recall area under the curve values on whole genome sequencing data. We also found that they lacked agreement with one another and with commercial MSI software on gene panel data, and that optimal threshold cut-offs vary by sequencing type. Lastly, we tested tools made specifically for RNA sequencing data and found they were outperformed by tools designed for use with DNA sequencing data. Out of all, two tools (MSIsensor2, MANTIS) performed well across nearly all datasets, but when all datasets were combined, their precision decreased. Our results caution that MSI tools can have much lower performance on datasets other than those on which they were originally evaluated, and in the case of RNA sequencing tools, can even perform poorly on the type of data for which they were created.

Deep learning for automated scoring of immunohistochemically stained tumour tissue sections - Validation across tumour types based on patient outcomes

We aimed to develop deep learning (DL) models to detect protein expression in immunohistochemically (IHC) stained tissue-sections, and to compare their accuracy and performance with manually scored clinically relevant proteins in common cancer types. Five cancer patient cohorts (colon, two prostate, breast, and endometrial) were included. We developed separate DL models for scoring IHC-stained tissue-sections with nuclear, cytoplasmic, and membranous staining patterns. For training, we used images with annotations of cells with positive and negative staining from the colon cohort stained for Ki-67 and PMS2 (nuclear model), the prostate cohort 1 stained for PTEN (cytoplasmic model) and β-catenin (membranous model). The nuclear DL model was validated for MSH6 in the colon, MSH6 and PMS2 in the endometrium, Ki-67 and CyclinB1 in prostate, and oestrogen and progesterone receptors in the breast cancer cohorts. The cytoplasmic DL model was validated for PTEN and Mapre2, and the membranous DL model for CD44 and Flotillin1, all in prostate cohorts. When comparing the results of manual and DL scores in the validation sets, using manual scores as the ground truth, we observed an average correct classification rate of 91.5 % (76.9-98.5 %) for the nuclear model, 85.6 % (73.3-96.6 %) for the cytoplasmic model, and 78.4 % (75.5-84.3 %) for the membranous model. In survival analyses, manual and DL scores showed similar prognostic impact, with similar hazard ratios and p-values for all DL models. Our findings demonstrate that DL models offer a promising alternative to manual IHC scoring, providing efficiency and reproducibility across various data sources and markers.

SOMATIC DEFICIENT MISMATCH REPAIR ASSESSED BY IMMUNOHISTOCHEMISTRY AND CLINICAL FEATURES IN BRAZILIAN GLIOBLASTOMA PATIENTS

BACKGROUND

Glioblastoma (GBM) is the most frequent primary malignant CNS tumor. Deficient mismatch repair (dMMR) is associated with better prognosis and is a biomarker for immunotherapy. Evaluation of MMR by immunohistochemistry (IHC) is accessible, cost effective, sensitive, and specific.

AIM

Our objective was to investigate MMR proteins in adult GBM patients.

MATERIALS AND METHODS

We retrospectively analyzed 68 GBM samples to evaluate the proficiency of MMR genes expression assessed by IHC. Clinicopathologic and molecular features were compared in proficient (pMMR) or dMMR.

RESULTS

10 (14.7%) samples showed dMMR, and the most frequent was MSH6 (100%) followed by MSH2, PMS2, and MLH1. We observed heterogeneous expression of dMMR in 5 GBMs. The median overall survival did not differ between pMMR (19.8 months; 0.2-30) and dMMR (16.9 months; 6.4-27.5) (p = 0.31). We observed a significantly higher overall survival associated with gross total resection compared to subtotal resection or biopsy (30.7 vs. 13.6 months, p = 0.02) and MGMT methylated status (29.6 vs. 19.8 months, p = 0.049). At the analysis time, 10 patients were still alive, all in the pMMR group.

CONCLUSIONS

Our data demonstrated dMMR phenotype assessed by IHC in an expressive portion of GBM patients, however without significant impact on overall survival.

An Evaluation of the Immunohistochemical Expression of Mismatch Repair Proteins (MSH2, MSH6, MLH1, and PMS2) in Prostate Adenocarcinoma

Background and objective

Mismatch repair (MMR) proteins are an integral part of the cell cycle, and they play an important role in the genomic stability of the microsatellite complex. Microsatellite instability (MSI) is associated with Lynch and multi-tumor syndromes. Identifying patients with Lynch syndrome is essential for screening, early detection, and surveillance of other Lynch syndrome-associated tumors. The role of MMR deficiency is well known in colorectal and endometrial adenocarcinoma. However, the role of MMR deficiency in prostatic adenocarcinoma is a matter of controversy. A few studies have been published to analyze the association between MMR deficiency and prostatic adenocarcinoma. In this study, we used immunohistochemistry to look into the expression of four MMR proteins in prostatic adenocarcinoma: MSH2, MSH6, MLH1, and PMS2.

Methodology

This was a cross-sectional descriptive study involving 74 cases of acinar prostatic adenocarcinoma, diagnosed with hematoxylin & eosin (H&E), over a period of six months between December 2021 and May 2022 at the Chughtai Institute of Pathology in Lahore, Pakistan. We performed the immunohistochemical (IHC) analysis and interpretation of four antibodies, i.e., MSH2, MSH6, MLH1, and PMS2.

Results

In our study, the age of the patients ranged from 50 to 98 years, with a mean age of 67.99 ± 9.59 years. The specimens were collected through transurethral resection of the prostate (TURP), transurethral vaporization of the prostate (TVP), core biopsy, and radical prostatectomy. Isolated loss of each MSH2 and PMS2 was noted in nine cases (12.20%) and MSH6 in two cases (2.70%). There was no loss noted for MLH1. Furthermore, simultaneous loss of MSH2/MSH6 was observed in one case (1.35%).

Conclusion

Our study findings revealed a low frequency of IHC expression of MMR proteins, especially the concurrent loss of paired MMR proteins. However, prostatic adenocarcinoma is associated with the isolated loss of MMR proteins. Thus, the present study does not warrant reflex testing/screening in every case of prostatic adenocarcinoma, because of its low frequency, which is probably suggestive of its sporadic pattern.

The immunohistochemical molecular risk classification in endometrial cancer: A pragmatic and high-reproducibility method

INTRODUCTION

The aim of this study is to assess the clinical reproducibility and the potential oncological validity of the molecular information provided by the immunohistochemistry (IHC) to properly stratify the endometrial cancer patients.

METHODS

Retrospective IHC analyses were conducted in a large series of 778 pre-operative uterine-confined ECs, studying the presence/absence of MLH1, MSH2, MSH6 and PMS2 to define the mismatch repair (MMR) stable or instable phenotype; the presence of p53 mutations and other molecular features. The molecular profile was correlated with histological, clinical and prognostic data.

RESULTS

Based on IHC assessment, we defined 3 EC populations: stable MMR patients (MMRs), instable patients (MMRi) and p53 mutated patients (p53+). Our result demonstrated that the IHC stratification statistically correlated with the most relevant pathologic-clinical features: FIGO stage (p < 0.001), grading (p < 0.001), histotype (p < 0.001), presence of LVSI (p < 0.001), myometrial invasion and tumor dimension (p = 0.003 for both). These 3 IHC populations statistically reflected the EC risk class ESGO-ESMO-ESP classification 2021 (p < 0.001). These results were also confirmed in the Kaplan-Meier curves in terms of overall survival (OS) and disease-free survival (DFS) (p < 0.0001). The multivariate analyses demonstrated that absence of estrogen receptor (ER) impacted the OS (p = 0.011) and, the Age > 60 years and the ER-status the DFS (p = 0.041 and p = 0.004).

CONCLUSION

In this large series, we demonstrated that the pragmatic and systematic use of IHC may have an important role to properly stratify, in terms of histological features and clinical outcomes, the EC patients.

Molecular Markers in Urinary Bladder Cancer: Applications for Diagnosis, Prognosis and Therapy

Cancer of the urinary bladder is a neoplasm with considerable importance in veterinary medicine, given its high incidence in several domestic animal species and its life-threatening character. Bladder cancer in companion animals shows a complex and still poorly understood biopathology, and this lack of knowledge has limited therapeutic progress over the years. Even so, important advances concerning the identification of tumour markers with clinical applications at the diagnosis, prognosis and therapeutic levels have recently been made, for example, the identification of pathological BRAF mutations. Those advances are now facilitating the introduction of targeted therapies. The present review will address such advances, focusing on small animal oncology and providing the reader with an update on this field. When appropriate, comparisons will be drawn with bladder cancer in human patients, as well as with experimental models of the disease.

Artificial Intelligence for Predicting Microsatellite Instability Based on Tumor Histomorphology: A Systematic Review

Microsatellite instability (MSI)/defective DNA mismatch repair (dMMR) is receiving more attention as a biomarker for eligibility for immune checkpoint inhibitors in advanced diseases. However, due to high costs and resource limitations, MSI/dMMR testing is not widely performed. Some attempts are in progress to predict MSI/dMMR status through histomorphological features on H&E slides using artificial intelligence (AI) technology. In this study, the potential predictive role of this new methodology was reviewed through a systematic review. Studies up to September 2021 were searched through PubMed and Embase database searches. The design and results of each study were summarized, and the risk of bias for each study was evaluated. For colorectal cancer, AI-based systems showed excellent performance with the highest standard of 0.972; for gastric and endometrial cancers they showed a relatively low but satisfactory performance, with the highest standard of 0.81 and 0.82, respectively. However, analyzing the risk of bias, most studies were evaluated at high-risk. AI-based systems showed a high potential in predicting the MSI/dMMR status of different cancer types, and particularly of colorectal cancers. Therefore, a confirmation test should be required only for the results that are positive in the AI test.

Microsatellite instability-high colorectal cancer patient-derived xenograft models for cancer immunity research

Context

There is an increasing demand for appropriate preclinical mice models for evaluating the efficacy of cancer immunotherapies.

Aims

Therefore, we established a humanized patient-derived xenograft (PDX) model using microsatellite instability-high (MSI-H) colorectal cancer (CRC) tissues and patient-derived peripheral blood mononuclear cells (PBMCs).

Subjects and Methods

The CRC tissues of patients scheduled for surgery were tested for MSI status, and CRC tumors were transplanted into NOD/LtSz-scid/IL-2Rg-/-(NSG) mice to establish MSI-H PDX models. PDX tumors were compared to the original patient tumors in terms of histological and genetic characteristics. To humanize the immune system of MSI-H PDX models, patient PBMCs were injected through the tail vein.

Results

PDX models were established from two patients with MSI-H CRC; one patient had a germline mutation in MLH1 (c.1990-2A > G), and the other patient had MLH1 promoter hypermethylation. PDX with the germline mutation was histologically similar to the patient tumor, and retained the genetic characteristics, including MSI-H, deficient mismatch repair (dMMR), and MLH1 mutation. In contrast, the histological features of the other PDX from a tumor with MLH1 promoter hypermethylation were clearly different from those of the original tumor, and MLH1 promoter hypermethylation and MSI-H/dMMR were lost in the PDX. When T cells from the same patient with MLH1 mutation were injected into the PDX through the tail vein, they were detected in the PDX tumor.

Conclusions

The MSI-H tumor with an MMR mutation is suitable for MSI-H PDX model generation. The PBMC humanized MSI-H PDX has the potential to be used as an efficient model for cancer immunotherapy research.

Current Landscape of Non-Small Cell Lung Cancer: Epidemiology, Histological Classification, Targeted Therapies, and Immunotherapy

Non-small cell lung cancer (NSCLC) is a subtype of the most frequently diagnosed cancer in the world. Its epidemiology depends not only on tobacco exposition but also air quality. While the global trends in NSCLC incidence have started to decline, we can observe region-dependent differences related to the education and the economic level of the patients. Due to an increasing understanding of NSCLC biology, new diagnostic and therapeutic strategies have been developed, such as the reorganization of histopathological classification or tumor genotyping. Precision medicine is focused on the recognition of a genetic mutation in lung cancer cells called "driver mutation" to provide a variety of specific inhibitors of improperly functioning proteins. A rapidly growing group of approved drugs for targeted therapy in NSCLC currently allows the following mutated proteins to be treated: EGFR family (ERBB-1, ERBB-2), ALK, ROS1, MET, RET, NTRK, and RAF. Nevertheless, one of the most frequent NSCLC molecular sub-types remains without successful treatment: the K-Ras protein. In this review, we discuss the current NSCLC landscape treatment focusing on targeted therapy and immunotherapy, including first- and second-line monotherapies, immune checkpoint inhibitors with chemotherapy treatment, and approved predictive biomarkers.

Analysis of Molecular Pretreated Tumor Profiles as Predictive Biomarkers of Therapeutic Response and Survival Outcomes after Neoadjuvant Therapy for Rectal Cancer in Moroccan Population

Pathologic features depending on tumor response to preoperative chemoradiotherapy are important to determine the outcomes in patients with rectal cancer. Evaluating the potential predictive roles of biomarker expression and their prognostic impact is a promising challenge. We reported here the immunohistochemical staining of a panel marker of mismatch repair protein (MMR), Ki67, HER-2, and p53. Additionally, identification of somatic mutations of KRAS, NRAS, and BRAF genes were performed by direct sequencing and pyrosequencing in pretreated biopsy tissues from 57 patients diagnosed for rectal cancer. Clinical features and pathological criteria for postneoadjuvant treatment surgical resection specimen's data were collected. Immunohistochemical expression and mutational status were correlated with therapeutic response, overall survival, and disease progression. The mean age of patients was 56 years. Seven (12.3%) out of 57 patients had a complete therapeutic response. Our analysis showed that when using complete therapeutic response (Dworak 4) and incomplete therapeutic response (Dworak 3, 2, and 1) as grouping factor, high p53 expression at the pretreatment biopsy was significantly associated to an incomplete response (p = 0.002). For 20 and 2 out of 57, KRAS and NRAS mutations were detected, respectively. The majority of these mutations affected codon 12. KRAS mutations detected at codon 146 (A146T, A146V) was associated with the appearance of recurrence and distant metastasis (p = 0.019). A high expression of HER-2 corresponding to score 3+ was observed in 3 pretreatment biopsy specimens. This class was significantly associated with a short relapse-free survival (p = 0.002). Furthermore, the high expression of Ki67 was moderately correlated with an older age (p = 0.016, r = 0.319). In addition, this shows that high p53 expression in the pretreatment biopsy was associated with an incomplete response in surgical resection specimens after neoadjuvant treatment, and a HER-2 score 3+ can be a predictive factor of distant metastasis and local recurrence. Larger, prospective, and more studies are needed.

ESMO recommendations on microsatellite instability testing for immunotherapy in cancer, and its relationship with PD-1/PD-L1 expression and tumour mutational burden: a systematic review-based approach

BACKGROUND

Cancers with a defective DNA mismatch repair (dMMR) system contain thousands of mutations most frequently located in monomorphic microsatellites and are thereby defined as having microsatellite instability (MSI). Therefore, MSI is a marker of dMMR. MSI/dMMR can be identified using immunohistochemistry to detect loss of MMR proteins and/or molecular tests to show microsatellite alterations. Together with tumour mutational burden (TMB) and PD-1/PD-L1 expression, it plays a role as a predictive biomarker for immunotherapy.

METHODS

To define best practices to implement the detection of dMMR tumours in clinical practice, the ESMO Translational Research and Precision Medicine Working Group launched a collaborative project, based on a systematic review-approach, to generate consensus recommendations on the: (i) definitions related to the concept of MSI/dMMR; (ii) methods of MSI/dMMR testing and (iii) relationships between MSI, TMB and PD-1/PD-L1 expression.

RESULTS

The MSI-related definitions, for which a consensus frame-work was used to establish definitions, included: 'microsatellites', 'MSI', 'DNA mismatch repair' and 'features of MSI tumour'. This consensus also provides recommendations on MSI testing; immunohistochemistry for the mismatch repair proteins MLH1, MSH2, MSH6 and PMS2 represents the first action to assess MSI/dMMR (consensus with strong agreement); the second method of MSI/dMMR testing is represented by polymerase chain reaction (PCR)-based assessment of microsatellite alterations using five microsatellite markers including at least BAT-25 and BAT-26 (strong agreement). Next-generation sequencing, coupling MSI and TMB analysis, may represent a decisive tool for selecting patients for immunotherapy, for common or rare cancers not belonging to the spectrum of Lynch syndrome (very strong agreement). The relationships between MSI, TMB and PD-1/PD-L1 expression are complex, and differ according to tumour types.

CONCLUSIONS

This ESMO initiative is a response to the urgent questions raised by the growing success of immunotherapy and provides also important insights on the relationships between MSI, TMB and PD-1/PD-L1.

Clinical implications of mismatch repair deficiency in prostate cancer

Immune checkpoint blockade holds great promise in the treatment of solid tumors but has not yet been approved for use in advanced prostate cancer. This is largely due to the relatively modest response in clinical trials in unselected patients and the lack of available biomarkers to predict clinical benefit. Germline and somatic mismatch repair (MMR) gene deficiencies are more prevalent than previously thought, especially in the metastatic setting, in patients with high-grade Gleason scores and in patients with variant histologies. An early signal suggests that patients with deficiency in MMR may respond well to immunotherapy. Both germline and somatic genetic testing are recommended, yet questions remain on the best modality for testing given lack of standardization and false-negative results in patients with complex genomic structural rearrangements. Expanded panels, such as next generation sequencing may increase the sensitivity without compromising specificity. Future studies are still needed to explore the relationships of hypermutation, tumor mutational burden, tumor-infiltrating lymphocytes and microsatellite instability-H status as predictors of response to immunotherapy. The drivers of variable response is largely unknown, and a more mature understanding of the mechanisms of resistance in deficiencies in MMR tumors may help to more precisely inform use of immunotherapy in prostate cancer.

Development of an MSI-positive colon tumor with aberrant DNA methylation in a PPAP patient

Polymerase proofreading-associated polyposis (PPAP) is a disease caused by germline variations in the POLE and POLD1 genes that encode catalytic subunits of DNA polymerases. Studies of cancer genomes have identified somatic mutations in these genes, suggesting the importance of polymerase proofreading of DNA replication in suppressing tumorigenesis. Here, we identified a germline frameshift variation in the POLE gene (c.4191_4192delCT, p.Tyr1398*) in a case with multiple adenomatous polyps and three synchronous colon cancers. Interestingly, one of the colon cancers showed microsatellite instability-high (MSI-H) and another microsatellite stable. Immunohistochemical staining revealed that the MSI-H tumor cells lost the expression of MLH1 protein. Whole genome sequencing of the MSI-H tumor did not find pathogenic somatic mutations in mismatch repair genes but found frameshift mutations in the TET genes that catalyze 5-methylcytosine hydroxylation. Bisulfite sequencing of the tumor corroborated an increase in the number of hypermethylated regions including the MLH1 promoter. These data indicate that PPAP patients might develop MSI-positive tumors through epigenetic silencing of MLH1. These findings will contribute to comprehensive understanding of the molecular basis of tumors that involve deficiency of proofreading activity of DNA polymerases.

Small molecule inhibitors uncover synthetic genetic interactions of human flap endonuclease 1 (FEN1) with DNA damage response genes

Flap endonuclease 1 (FEN1) is a structure selective endonuclease required for proficient DNA replication and the repair of DNA damage. Cellularly active inhibitors of this enzyme have previously been shown to induce a DNA damage response and, ultimately, cell death. High-throughput screens of human cancer cell-lines identify colorectal and gastric cell-lines with microsatellite instability (MSI) as enriched for cellular sensitivity to N-hydroxyurea series inhibitors of FEN1, but not the PARP inhibitor olaparib or other inhibitors of the DNA damage response. This sensitivity is due to a synthetic lethal interaction between FEN1 and MRE11A, which is often mutated in MSI cancers through instabilities at a poly(T) microsatellite repeat. Disruption of ATM is similarly synthetic lethal with FEN1 inhibition, suggesting that disruption of FEN1 function leads to the accumulation of DNA double-strand breaks. These are likely a result of the accumulation of aberrant replication forks, that accumulate as a consequence of a failure in Okazaki fragment maturation, as inhibition of FEN1 is toxic in cells disrupted for the Fanconi anemia pathway and post-replication repair. Furthermore, RAD51 foci accumulate as a consequence of FEN1 inhibition and the toxicity of FEN1 inhibitors increases in cells disrupted for the homologous recombination pathway, suggesting a role for homologous recombination in the resolution of damage induced by FEN1 inhibition. Finally, FEN1 appears to be required for the repair of damage induced by olaparib and cisplatin within the Fanconi anemia pathway, and may play a role in the repair of damage associated with its own disruption.

Low Level of Microsatellite Instability Correlates with Poor Clinical Prognosis in Stage II Colorectal Cancer Patients

The influence of microsatellite instability (MSI) on the prognosis of colorectal cancer (CRC) requires more investigation. We assessed the role of MSI status in survival of individuals diagnosed with primary colorectal cancer. In this retrospective cross-sectional study the MSI status was determined in 158 formalin-fixed paraffin-embedded tumors and their matched normal tissues from patients who underwent curative surgery. Cox proportional hazard modeling was performed to assess the clinical prognostic significance. In this study we found that MSI-H tumors were predominantly located in the colon versus rectum (p = 0.03), associated with poorer differentiation (p = 0.003) and TNM stage II/III of tumors (p = 0.02). In CRC patients with stage II, MSI-L cases showed significantly poorer survival compared with patients who had MSI-H or MSS tumors (p = 0.04). This study indicates that MSI-L tumors correlate with poorer clinical outcome in patients with stage II tumors (p = 0.04) or in tumors located in the colon (p = 0.02). MSI-L characterizes a distinct subgroup of CRC patients who have a poorer outcome. This study suggests that MSI status in CRC, as a clinical prognostic marker, is dependent on other factors, such as tumor stage and location.

Microsatellite instability in gallbladder carcinoma

The genetic abnormalities involved in the pathogenesis of gallbladder carcinoma (GBC) remain unclear. Microsatellite instability (MSI) has been described in many carcinomas, but little is known about the significance of mismatch repair in gallbladder carcinogenesis. Additionally, methylation status of long interspersed element-1 (LINE-1), a surrogate marker of global DNA methylation, has defined distinct subsets of other cancer types but has not been explored in GBC. Immunohistochemical expression of MSH2, MSH6, MLH1, and PMS2 and LINE-1 mRNA in situ hybridization was evaluated in 67 primary and 15 metastatic GBCs from 77 patients. Amplification of human epidermal growth factor receptor 2 (HER2) was evaluated by fluorescence in situ hybridization. Genotyping for 24 genes involved in carcinogenesis was performed using a multiplex PCR-based platform. MSI was present in 6 of 77 GBCs (7.8 %). Loss of MSH2/MSH6 was detected in five cases and loss of MLH1/PMS2 in one case. MSI status was not associated with Lynch syndrome, tumor grade, extracellular mucin, or tumor-infiltrating lymphocytes. There was no significant difference in mean overall survival of patients with and without MSI. Strong LINE-1 staining was identified in none of the GBC with MSI and in 36 of 69 (52 %) of those without MSI (p = 0.005), suggesting that LINE-1 in the former cohort was hypermethylated. All MSI tumors were negative for HER2 amplification, and TP53 and NRAS mutations were only found in GBC without MSI. MSI was identified in a minority of GBC cases. The strong correlation between global DNA methylation as measured by LINE-1 and loss of mismatch repair proteins suggests that methylation may account for the loss of these proteins. These hypermethylated tumors appear to represent a genetically unique cohort of gallbladder neoplasms, and the data suggests that demethylating agents may have a therapeutic value in this class of tumors.

Microsatellite alteration in multiple primary lung cancer

Patients with pulmonary neoplasms have an increased risk for developing a second tumor of the lung, either at the same time or different times. It is important to determine if the second tumor represents an independent primary tumor or recurrence/metastasis, because it will significantly change the management and prognosis. Microsatellite instability (MSI) and loss of heterozygosity (LOH) represents molecular disorders acquired by the cell during neoplastic transformation. Both are associated with genetic instability. Functional silencing of tumour suppressor genes may be the consequence of genomic instability, particularly of the globally occurring LOH phenomenon. Numerous studies have confirmed the role of MSI/LOH at both the early and the late stages of multiple primary lung cancer. This paper reviews the published literatures focused on the role of MSI/LOH significance in multiple primary lung cancer. Additionally, a new method based on the allelic variations at polymorphic microsatellite markers was offered that it does not rely on collection of normal tissue, performed with minimal tumor sample, and will complement clinical criteria for diagnostic discrimination between multiple primary cancers versus solitary metastatic diseases.

De Novo proteome analysis of genetically modified tumor cells by a metabolic labeling/azide-alkyne cycloaddition approach

Activin receptor type II (ACVR2) is a member of the transforming growth factor type II receptor family and controls cell growth and differentiation, thereby acting as a tumor suppressor. ACVR2 inactivation is known to drive colorectal tumorigenesis. We used an ACVR2-deficient microsatellite unstable colon cancer cell line (HCT116) to set up a novel experimental design for comprehensive analysis of proteomic changes associated with such functional loss of a tumor suppressor. To this end we combined two existing technologies. First, the ACVR2 gene was reconstituted in an ACVR2-deficient colorectal cancer (CRC) cell line by means of recombinase-mediated cassette exchange, resulting in the generation of an inducible expression system that allowed the regulation of ACVR2 gene expression in a doxycycline-dependent manner. Functional expression in the induced cells was explicitly proven. Second, we used the methionine analog azidohomoalanine for metabolic labeling of newly synthesized proteins in our cell line model. Labeled proteins were tagged with biotin via a Click-iT chemistry approach enabling specific extraction of labeled proteins by streptavidin-coated beads. Tryptic on-bead digestion of captured proteins and subsequent ultra-high-performance LC coupled to LTQ Orbitrap XL mass spectrometry identified 513 proteins, with 25 of them differentially expressed between ACVR2-deficient and -proficient cells. Among these, several candidates that had already been linked to colorectal cancer or were known to play a key role in cell growth or apoptosis control were identified, proving the utility of the presented experimental approach. In principle, this strategy can be adapted to analyze any gene of interest and its effect on the cellular de novo proteome.

Construction and application of a Rh-Pt DNA metalloinsertor conjugate

We report the synthesis and characterization of a bimetallic conjugate (RhPt) in which an oxaliplatin derivative is tethered to a rhodium metalloinsertor through an aminomalonate leaving group ligand. The complex interacts with DNA through metalloinsertion at a base pair mismatch followed by formation of a covalent Pt-DNA adduct. Characterization of RhPt in mismatch repair-deficient HCT116O cells reveals increased cytotoxicity compared to cisplatin and oxaliplatin as well as relative to the unconjugated rhodium and platinum counterparts. Caspase and poly-ADP ribose polymerase inhibition assays indicate that RhPt induces apoptotic cell death. Inductively coupled plasma mass spectrometry (ICP-MS) experiments reveal that RhPt exhibits enhanced cellular uptake properties that contribute to its increased efficacy.

The analysis of microsatellite instability in extracolonic gastrointestinal malignancy

Microsatellite instability (MSI) is a genetic feature of sporadic and familial cancers of multiple sites and is related to defective mismatch repair (MMR) protein function. Lynch syndrome (LS) is a familial form of MMR deficiency that may present with a spectrum of MSI positive cancers including gastrointestinal (GI) malignancies. The incidence of high level MSI (MSI-H) in colorectal carcinoma is well defined in both familial and sporadic cases and these tumours portend a better overall prognosis in colorectal carcinoma (CRC). There are certain morphological features that suggest MSI-H CRC and international guidelines have been established for the evaluation of MSI in CRC. The prevalence and morphological features of extracolonic GI MSI-H tumours are less well documented. Furthermore, it is unclear whether the guidelines for the assessment of MSI in CRC are appropriate for application to extracolonic GI malignancies. This review aims to summarise the recent literature on MSI in extracolonic LS-related GI tract malignancies with special attention to the assessment of the MMR system by evaluation of specific microsatellite markers and/or immunohistochemical evaluation of MMR protein expression. The reported prevalence of sporadic and LS-related MSI-H tumours along with their associated unique morphological patterns and related prognostic or therapeutic implications will be discussed.

Genomic Instability and Cancer

Genomic instability is a characteristic of most cancer cells. It is an increased tendency of genome alteration during cell division. Cancer frequently results from damage to multiple genes controlling cell division and tumor suppressors. It is known that genomic integrity is closely monitored by several surveillance mechanisms, DNA damage checkpoint, DNA repair machinery and mitotic checkpoint. A defect in the regulation of any of these mechanisms often results in genomic instability, which predisposes the cell to malignant transformation. Posttranslational modifications of the histone tails are closely associated with regulation of the cell cycle as well as chromatin structure. Nevertheless, DNA methylation status is also related to genomic integrity. We attempt to summarize recent developments in this field and discuss the debate of driving force of tumor initiation and progression.

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.

Mismatch repair proteins in recurrent prostate cancer

Normal cell function requires strict control over the repair of DNA damage, which prevents excessive mutagenesis. An enhanced accumulation of mutations results in the multistep process generally known as carcinogenesis. Defects in repair pathways fuel such mutagenesis by allowing reiterative cycles of mutation, selection, and clonal expansion that drive cancer progression. The repair of mismatches is an important mechanism in the prevention of such genetic instability. In addition, proteins of this pathway have the unique ability to function in DNA damage response by inducing apoptosis when irreparable damage is encountered. Though originally identified primarily in association with a predisposition to hereditary colon cancer, mismatch repair defects have been identified in many other cancer types, including prostate cancer. From the first discovery of microsatellite instability in prostate cancer cell lines and tumor samples, variations in protein levels and a possible association with recurrence and aggression of disease have been described. Current results suggest that the involvement of mismatch repair proteins in prostate cancer may differ from that found in colorectal cancer, in the type of proteins and protein defects involved and the type of causative mutations. Additional work is clearly needed to investigate this involvement and the possibility that such defects may affect treatment response and androgen independence.

Transforming growth factor beta receptor 2 (TGFBR2) changes sialylation in the microsatellite unstable (MSI) Colorectal cancer cell line HCT116

Aberrant glycosylation is a common feature of many malignancies including colorectal cancers (CRCs). About 15% of CRC show the microsatellite instability (MSI) phenotype that is associated with a high frequency of biallelic frameshift mutations in the A10 coding mononucleotide microsatellite of the transforming growth factor beta receptor 2 (TGFBR2) gene. If and how impaired TGFBR2 signaling in MSI CRC cells affects cell surface glycan pattern is largely unexplored. Here, we used the TGFBR2-deficient MSI colon carcinoma cell line HCT116 as a model system. Stable clones conferring doxycycline (dox)-inducible expression of a single copy wildtype TGFBR2 transgene were generated by recombinase-mediated cassette exchange (RMCE). In two independent clones, dox-inducible expression of wildtype TGFBR2 protein and reconstitution of its signaling function was shown. Metabolic labeling experiments using the tritiated sialic acid precursor N-acetyl-D-mannosamine (ManNAc) revealed a significant decline (∼30%) of its incorporation into newly synthesized sialoglycoproteins in a TGFBR2-dependent manner. In particular, we detected a significant decrease of sialylated ß1-integrin upon reconstituted TGFBR2 signaling which did not influence ß1-integrin protein turnover. Notably, TGFBR2 reconstitution did not affect the transcript levels of any of the known human sialyltransferases when examined by real-time RT- PCR analysis. These results suggest that reconstituted TGFBR2 signaling in an isogenic MSI cell line model system can modulate sialylation of cell surface proteins like ß1-integrin. Moreover, our model system will be suitable to uncover the underlying molecular mechanisms of altered MSI tumor glycobiology.

Prognostic value of microsatellite instability in sporadic locally advanced rectal cancer following neoadjuvant radiotherapy

AIMS

This study was conducted to investigate the clinicopathological significance and prognostic value of microsatellite instability (MSI) in locally advanced rectal cancer (LARC) following neoadjuvant radiotherapy.

METHODS AND RESULTS

A total of 316 consecutive patients with LARC who underwent neoadjuvant radiotherapy and curative surgery were included retrospectively. Microsatellite instability in pretreatment biopsy tissue was assessed using the pentaplex panel of mononucleotides. Twenty-five tumours (7.9%) were assessed as high-frequency MSI (MSI-H) and 291 were low-frequency MSI (MSI-L; n = 42) or microsatellite stable (MSS; n = 249). There were no significant differences in terms of gender, age, tumour location or pretreatment serum carcinoembryonic antigen between the MSI-H and MSI-L + MSS groups. Microsatellite instability was not associated statistically with pathological stage, radiation-induced tumour regression or downstaging. No significant difference was found in disease-free survival (DFS) between the two groups but, within the subgroup of ypN0 stage, patients with MSI-H tumours presented a significantly improved DFS compared with those with MSI-L or MSS tumours (100% versus 79.8%, P < 0.05), whereas no DFS improvement was observed for patients with MSI-H tumours in the ypN + subgroup.

CONCLUSIONS

Microsatellite instability could not predict a histopathological response to neoadjuvant radiotherapy, but was a good prognostic marker for patients without lymph node metastasis after neoadjuvant radiotherapy.

Cell-selective biological activity of rhodium metalloinsertors correlates with subcellular localization

Deficiencies in the mismatch repair (MMR) pathway are associated with several types of cancers, as well as resistance to commonly used chemotherapeutics. Rhodium metalloinsertors have been found to bind DNA mismatches with high affinity and specificity in vitro, and also exhibit cell-selective cytotoxicity, targeting MMR-deficient cells over MMR-proficient cells. Ten distinct metalloinsertors with varying lipophilicities have been synthesized and their mismatch binding affinities and biological activities determined. Although DNA photocleavage experiments demonstrate that their binding affinities are quite similar, their cell-selective antiproliferative and cytotoxic activities vary significantly. Inductively coupled plasma mass spectrometry (ICP-MS) experiments have uncovered a relationship between the subcellular distribution of these metalloinsertors and their biological activities. Specifically, we find that all of our metalloinsertors localize in the nucleus at sufficient concentrations for binding to DNA mismatches. However, the metalloinsertors with high rhodium localization in the mitochondria show toxicity that is not selective for MMR-deficient cells, whereas metalloinsertors with less mitochondrial rhodium show activity that is highly selective for MMR-deficient versus proficient cells. This work supports the notion that specific targeting of the metalloinsertors to nuclear DNA gives rise to their cell-selective cytotoxic and antiproliferative activities. The selectivity in cellular targeting depends upon binding to mismatches in genomic DNA.

ARID1A expression loss in gastric cancer: pathway-dependent roles with and without Epstein-Barr virus infection and microsatellite instability

The AT-rich interactive domain 1A gene (ARID1A), which encodes one of the subunits in the Switch/Sucrose Nonfermentable chromatin remodeling complex, carries mutations and is responsible for loss of protein expression in gastric carcinoma, particularly with Epstein-Barr virus (EBV) infection and a microsatellite instability-high phenotype. We used immunohistochemistry to investigate the significance of ARID1A loss in 857 gastric carcinoma cases, including 67 EBV(+) and 136 MLH1-lost gastric carcinomas (corresponding to a microsatellite instability-high phenotype). Loss of ARID1A expression was significantly more frequent in EBV(+) (23/67; 34 %) and MLH1-lost (40/136; 29 %) gastric carcinomas than in EBV(-)MLH1-preserved (32/657; 5 %) gastric carcinomas (P < 0.01). Loss of ARID1A correlated with larger tumor size, advanced invasion depth, lymph node metastasis, and poor prognosis in EBV(-)MLH1-preserved gastric carcinoma. A correlation was found only with tumor size and diffuse-type histology in MLH1-lost gastric carcinoma, but no correlation was observed in EBV(+) gastric carcinoma. Loss of ARID1A expression in EBV(+) gastric carcinoma was highly frequent in the early stage of gastric carcinoma, although EBV infection did not cause downregulation of ARID1A: EBV-positive nasopharyngeal carcinomas (n = 8) and lymphomas (n = 15) failed to show loss of ARID1A, and EBV infection did not cause loss of ARID1A in gastric carcinoma cell lines. Taken together, loss of ARID1A may be an early change in carcinogenesis and may precede EBV infection in gastric epithelial cells, while loss of ARID1A promotes cancer progression in gastric cancer cells without EBV infection or loss of MLH1 expression. Loss of ARID1A has different and pathway-dependent roles in gastric carcinoma.

Evaluation of microsatellite instability in women with epithelial ovarian cancer

The function of microsatellite instability (MSI) and the optimal panel of markers for epithelial ovarian cancer (EOC) are not well established. This study aimed to use the National Cancer Institute (NCI) markers BAT25, BAT26, D2S123, D5S346 and D17S250 to evaluate MSI in patients with ovarian serous cystadenocarcinoma, compared with ovarian serous cystadenoma and normal ovaries. A total of 37 patients were divided into three groups, as follows: cystadenocarcinoma (n=13), cystadenoma (n=10) and normal ovaries (n=14). DNA was extracted with TRIzol and quantified by spectrophotometry. MSI was evaluated by polymerase chain reaction (PCR), and classified as high (MSI-H), low (MSI-L) or stable (MSS). FIGO staging was I/II in 23.1% and III/IV in 76.9% of the cystadenocarcinoma group. Polymorphisms were found using at least one marker in 32 women, and were observed with D2S123 (83.7%), D17S250 (81.1%), D5S346 (72.9%), BAT25 (21.6%) and BAT26 (16.2%) markers. In the cystadenocarcinoma group, BAT25, BAT26, D2S123, D5S346 and D17S250 markers were positive in 30.8, 76.9, 53.8, 69.2 and 69.2% of patients, respectively. The same markers were positive in 30, 50, 40, 60 and 30% of the cystadenoma group, and 50, 71.4, 71.4, 64.3 and 63.3% in the normal ovary group, respectively. MSI-H was present in 84.6, 60 and 78.6% of the cystadenocarcinoma, cystadenoma and normal patients, respectively. MSI-L was detected in 0, 30 and 7.1%, and MSS was identified in 15.4, 10 and 14.3% of the cystadenocarcinoma, cystadenoma and normal patients, respectively. The frequency of MSI in both benign epithelial ovarian neoplasms and in normal ovaries was high, as well as in EOC, with no statistically significant difference between the groups. This suggests that MSI may arise as a consequence of the ovulatory process, and not solely as a feature of malignant ovarian tumors.

Crystal structure of Δ-[Ru(bpy)₂dppz]²⁺ bound to mismatched DNA reveals side-by-side metalloinsertion and intercalation

DNA mismatches represent a novel target in the development of diagnostics and therapeutics for cancer, because deficiencies in DNA mismatch repair are implicated in cancers, and cells that are repair-deficient show a high frequency of mismatches. Metal complexes with bulky intercalating ligands serve as probes for DNA mismatches. Here, we report the high-resolution (0.92 Å) crystal structure of the ruthenium 'light switch' complex Δ-[Ru(bpy)(2)dppz](2+) (bpy = 2,2'-bipyridine and dppz = dipyridophenazine), which is known to show luminescence on binding to duplex DNA, bound to both mismatched and well-matched sites in the oligonucleotide 5'-(dCGGAAATTACCG)(2)-3' (underline denotes AA mismatches). Two crystallographically independent views reveal that the complex binds mismatches through metalloinsertion, ejecting both mispaired adenosines. Additional ruthenium complexes are intercalated at well-matched sites, creating an array of complexes in the minor groove stabilized by stacking interactions between bpy ligands and extruded adenosines. This structure attests to the generality of metalloinsertion and metallointercalation as DNA binding modes.

Colonic carcinogenesis along different genetic routes: glycophenotyping of tumor cases separated by microsatellite instability/stability

Different genetic routes account for colonic carcinogenesis. However, when analyzing colon cancer specimens, separation into different groups based on genetic alterations is commonly not performed. Thus, we here initiate the comparative phenotyping considering microsatellite instability/stability for clinical specimens. The focus is given to glycan epitopes, expression of which is known to be modulated by signal-transducing proteins that act as key regulators of normal colon epithelial growth and differentiation. In addition to six plant lectins used as sensors, the presence of two adhesion/growth-regulatory galectins is studied. Overall, a considerable level of intra- and interindividual heterogeneity is revealed. Alterations in the proportion of stained cells between tumor-adjacent and malignant epithelia concerned plant lectins, which bind substituted N-glycan cores, α2,6-sialylated branch ends, core 1 O-glycans and N-acetylgalactosamine. A tendency for changes was noted between microsatellite-unstable and microsatellite-stable cases for core substitution (bisected N-glycan, presence of β1,6-branching) and status of α2,6-sialylation. Statistical significance was reached for presence of galectin-3, found to be elevated in microsatellite-stable compared to microsatellite-unstable tumors. These results emphasize the potential of distinct signaling pathways to regulate certain aspects of the glycophenotype in vivo and thus delineate a perspective to discern functionally relevant deviations in expression of endogenous lectins and their counter-receptors.

Selective cytotoxicity of rhodium metalloinsertors in mismatch repair-deficient cells

Mismatches in DNA occur naturally during replication and as a result of endogenous DNA damaging agents, but the mismatch repair (MMR) pathway acts to correct mismatches before subsequent rounds of replication. Rhodium metalloinsertors bind to DNA mismatches with high affinity and specificity and represent a promising strategy to target mismatches in cells. Here we examine the biological fate of rhodium metalloinsertors bearing dipyridylamine ancillary ligands in cells deficient in MMR versus those that are MMR-proficient. These complexes are shown to exhibit accelerated cellular uptake which permits the observation of various cellular responses, including disruption of the cell cycle, monitored by flow cytometry assays, and induction of necrosis, monitored by dye exclusion and caspase inhibition assays, that occur preferentially in the MMR-deficient cell line. These cellular responses provide insight into the mechanisms underlying the selective activity of this novel class of targeted anticancer agents.

Causal link between microsatellite instability and hMRE11 dysfunction in human cancers

Maintenance of genomic integrity is essential for cell survival, and genomic instability is a commonly recognized intrinsic property of all cancers. Microsatellite instability (MSI) represents a frequently occurring and easily traceable simple form of sequence variation, signified by the contraction or expansion of specific DNA sequences containing short tandem repeats. MSI is frequently detected in tumor cells with DNA mismatch repair (MMR) deficiency. It is commonly conceived that instability at individual microsatellite loci can arise spontaneously in cells independent of MMR status, and different microsatellite loci are generally not affected uniformly by MMR deficiency. It is well recognized that MMR deficiency per se is not sufficient to initiate tumorigenesis; rather, the biological effects have to be exerted by mutations in genes controlling cell survival, DNA damage response, and apoptosis. Recently, shortening of an intronic hMRE11 poly(T)11 tract has been associated with MMR deficiency, raising the possibility that hMRE11 may be inactivated by defective MMR. However, the molecular nature underlying this association is presently unknown, and review of the current literature suggests that hMRE11 is most likely involved with the MMR pathway in a more complex fashion than simply being a MMR target gene. An alternative scenario is proposed to better reconcile the differences among various studies. The potential role of hMRE11 in telomere repeats stability is also discussed.

Association between the hMSH2 IVS12-6 T>C polymorphism and cancer risk: A meta-analysis

The hMSH2 gene, a member of the mismatch repair (MMR) pathway, plays a key role in the maintenance of genomic integrity. The common sequence variation in hMSH2, IVS12-6 T>C, has been implicated in cancer risk. However, the results of published studies on this polymorphism remain conflicting. Hence, we conducted a meta-analysis to clarify the role of the hMSH2 IVS12-6 T>C polymorphism in cancer. We performed a comprehensive literature search updated to March 2011 of studies on the associations between the hMSH2 IVS12-6 T>C polymorphism and cancer risk. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the associations. Thirteen studies involving 7,527 patients and 8,762 control subjects were included in this meta-analysis. The overall results indicated no major influence of the polymorphism on cancer risk. However, stratified analysis by cancer types showed that the hMSH2 IVS12-6 polymorphism increased the risk for non-Hodgkin's lymphomas (heterozygote comparison: OR=1.62; 95% CI 1.06-2.47). When stratified by the source of controls, significant associations were observed in hospital-based populations (heterozygote comparison: OR=1.28; 95% CI 1.02-1.61). These results indicate that the polymorphism of hMSH2, IVS12-6, may cause a different effect in different types of cancers. To draw more comprehensive conclusions, further prospective studies with larger numbers of participants worldwide are required to examine the associations between this polymorphism and cancer risk.

Review of histopathological and molecular prognostic features in colorectal cancer

Prediction of prognosis in colorectal cancer is vital for the choice of therapeutic options. Histopathological factors remain paramount in this respect. Factors such as tumor size, histological type and subtype, presence of signet ring morphology and the degree of differentiation as well as the presence of lymphovascular invasion and lymph node involvement are well known factors that influence outcome. Our understanding of these factors has improved in the past few years with factors such as tumor budding, lymphocytic infiltration being recognized as important. Likewise the prognostic significance of resection margins, particularly circumferential margins has been appreciated in the last two decades. A number of molecular and genetic markers such as KRAS, BRAF and microsatellite instability are also important and correlate with histological features in some patients. This review summarizes our current understanding of the main histopathological factors that affect prognosis of colorectal cancer.

Microsatellite instability in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer in the world. In 75% CRC develops sporadically, in 25% hereditary or as a consequence of inflammatory bowel disease. CRC carcinogenesis develops over many years. The cause of CRC in 85% is chromosomal instability (CIN) and in 15% microsatellite instability (MSI-H), where hereditary nonpolyposis colorectal cancer (HNPCC) represents 10-20%. Microsatellite sequences (MS) are repeated sequences of short stretches of DNA all over the genome. Microsatellite stability (MSS) means MS are the same in each cell of an individual, whereas microsatellite instability (MSI-H) means MS differ in normal and cancer cells of an individual. The cause of MSI-H is a damaged mismatch repair mechanism (MMR), with the most important MMR proteins being MSH2, MLH1 and MSH6.

CONCLUSIONS

MSI-H seems to be an important prognostic factor in CRC and an important predictive factor of CRC chemotherapeutic treatment efficacy. Clinical trials conducted until now have shown contradictory findings in different chemotherapeutic settings, adjuvant and palliative; therefore MSI-H is going to be the object of the future research. The future of cancer treatment is in the individualized therapy based on molecular characteristics of the tumour, such as MSI-H in CRC.

Evaluation of microsatellite instability in urine for the diagnosis of transitional cell carcinoma of the lower urinary tract in dogs

BACKGROUND

The accumulation of frame-shift mutations in microsatellites (MS), termed microsatellite instability (MSI), is associated with certain tumors. MSI and its detection in urine samples has been used to aid in the detection of human bladder cancer.

HYPOTHESIS

Evaluation of MSI in urine is a useful assay test for diagnosis of transitional cell carcinoma (TCC) in dogs and is more specific than the commercially available, veterinary bladder tumor analyte (V-BTA) test.

ANIMALS

Seventy-three dogs: healthy controls (n=21), proteinuric (n=12), lower urinary tract disease excluding TCC (n=17), and TCC (n=23).

METHODS

Prospective observational study. Urine samples collected from each animal were evaluated for MSI and using the V-BTA. For MSI detection, 22 MS sequences were polymerase chain reaction amplified from urine and blood, subjected to capillary electrophoresis, and the MS genotypes were compared. Aberration in ≥15% of MS was considered indicative of MSI.

RESULTS

MSI was detected in 11 of 23 (48%) urine samples from dogs with TCC. MSI was also detected in 12 of 50 (24%) of the control animals, including 29, 16, and 24% of healthy, proteinuric, and lower urinary disease dogs, respectively. In this population, sensitivity and specificity of MSI analysis was 48 and 76%, respectively, compared with 83 and 64%, respectively, for the V-BTA test.

CONCLUSIONS

MS analysis as performed in this study is not useful in the diagnosis of TCC.

Prognostic value of microsatellite instability (MSI) and PTEN expression in women with endometrial cancer: results from studies of the NCIC Clinical Trials Group (NCIC CTG)

AIM

The impact of PTEN status and microsatellite instability (MSI) on the prognosis of women with endometrial cancer is controversial. The aim of this study was to investigate MSI and PTEN expression in two patient populations using data from NCIC CTG studies.

METHODS

Archival paraffin embedded tumour from women with endometrial cancer enrolled in NCIC CTG studies: EN5 (stage I/II) and IND 126, 148 and 160 (advanced/recurrent disease) were examined for MSI using BAT25/26 and for PTEN expression using immunohistochemistry. PTEN and MSI status were correlated with clinicopathologic variables and survival using data from NCIC CTG trial databases.

RESULTS

PTEN and MSI results were available from 128 and 163 patients, respectively. MSI+ tumours were more common in women enrolled in EN5 compared to the IND studies (p=0.01). PTEN negative tumours were associated with improved survival in both univariate (hazard ratio (HR) 0.55, 95% confidence interval (CI) 0.32-0.94; p=0.03) and multivariate (adjusted HR 0.54, 95% CI 0.30-0.96; p=0.03) analyses in women enrolled in IND studies. Microsatellite stable tumours were associated with an improved prognosis in univariate (HR 0.18, 95% CI 0.06-0.51; p<0.0001) and multivariate (adjusted HR 0.16, 95% CI 0.05-0.5; p<0.0001) analyses in women enrolled in EN5. There was no significant correlation between MSI and PTEN status.

CONCLUSIONS

PTEN negative tumours in women with advanced disease are associated with improved survival. MSI+ tumours are more common in early stage disease and in this group of women are associated with a worse prognosis.

Sebaceous lesions and their associated syndromes: part II

Sebaceous lesions are associated with two syndromes with widespread multisystem disorders and tumors. Linear sebaceous nevus syndrome has been traditionally known as the triad of sebaceous nevus of Jadassohn, seizures, and mental retardation. This syndrome encompasses a much broader spectrum of multisystem disorders, which is explored below. Muir-Torre syndrome is described as the presence of sebaceous tumors or keratoacanthomas with an underlying visceral malignancy. It is caused by mutations in DNA mismatch repair genes. We discuss its relationship with Lynch syndrome and suggest a comprehensive algorithm on how to screen patients with sebaceous neoplasms for Muire-Torre syndrome. We also provide suggested intensive cancer screening guidelines based on recommendations for patients with Lynch syndrome that may also be of value for patients with Muir-Torre syndrome.

Detection of microsatellite instability in gastric cancer and dysplasia tissue in Lanzhou province of China

AIM: To investigate the relationship between microsatellite instability (MSI) and the gastric cancer and its effect on carcinogenesis in Lanzhou province of China.

METHODS: Silver staining single strand conformation polymorphis-polymerease chain reaction (PCR-SSCP) was used to screen MSI markers at 5 loci (Bat25, Bat26, D2S123, D5S346 and D17S250) in the DNA which were all extracted from gastric cancer (n = 43) and dysplasia (n = 21) tissues with Phenol-Chloroform method, in the same way as corresponding normal gastric tissues. MSI was analyzed in the gastric cancer and dysplasia.

RESULTS: MSI was detected in 28/43 cases of gastric cancer (65.1%) including 8 MSI-H (28.6%), and 20 MSI-L (71.4%). Six out of 21 cases were detected in dysplasia (28.6%), including 2 MSI-H (33.3%) and 4 MSI-L (66.7%).

CONCLUSION: The incidence of MSI in HEXI gastric cancer is very higher, probably contributive to the multistep gastric carcinogenesis. MSI may be a relatively better marker of gastric cancer.

DNA mismatch binding and antiproliferative activity of rhodium metalloinsertors

Deficiencies in mismatch repair (MMR) are associated with carcinogenesis. Rhodium metalloinsertors bind to DNA base mismatches with high specificity and inhibit cellular proliferation preferentially in MMR-deficient cells versus MMR-proficient cells. A family of chrysenequinone diimine complexes of rhodium with varying ancillary ligands that serve as DNA metalloinsertors has been synthesized, and both DNA mismatch binding affinities and antiproliferative activities against the human colorectal carcinoma cell lines HCT116N and HCT116O, an isogenic model system for MMR deficiency, have been determined. DNA photocleavage experiments reveal that all complexes bind to the mismatch sites with high specificities; DNA binding affinities to oligonucleotides containing single base CA and CC mismatches, obtained through photocleavage titration or competition, vary from 10(4) to 10(8) M(-1) for the series of complexes. Significantly, binding affinities are found to be inversely related to ancillary ligand size and directly related to differential inhibition of the HCT116 cell lines. The observed trend in binding affinity is consistent with the metalloinsertion mode where the complex binds from the minor groove with ejection of mismatched base pairs. The correlation between binding affinity and targeting of the MMR-deficient cell line suggests that rhodium metalloinsertors exert their selective biological effects on MMR-deficient cells through mismatch binding in vivo.

Compensation of loss of protein function in microsatellite-unstable colon cancer cells (HCT116): a gene-dependent effect on the cell surface glycan profile

Tumors that display a high level of microsatellite instability (MSI-H) accumulate somatic frameshift mutations in several genes. The compensation of this loss of function by transfection represents a suitable approach to tie respective gene deficiency to alterations in cellular characteristics. In view of the emerging significance of cell surface glycans as biochemical signals for presentation/activity of various receptors/integrins and for susceptibility to adhesion/growth-regulatory tissue lectins, we examined the glycophenotype in the MSI-H colon cancer cell line HCT116 for activin type 2 receptor (ACVR2), absent in melanoma 2 (AIM2), and transforming growth factor beta-type 2 receptor (TGFBR2) known to be associated with MSI colorectal carcinogenesis. A panel of probes specific for functional carbohydrate epitopes including human lectins was used to trace changes in cell surface levels, thereby initiating glycan analysis related to MSI. In particular, the presence of core substitutions and branching in N-glycans, the sialylation status of N- and O-glycans, and the presence of Le(a/x)-epitopes were profiled. Transient transfection affected the glycophenotype, depending on the nature of the gene and the probe. The TGFBR2 presence reduced binding of probes specific for a core substitution and increased branch length in N-glycosylation, even reaching a P-value of 0.0016. ACVR2/AIM2 influenced core 1 mucin-type O-glycosylation differentially, upregulation by ACVR2, and downregulation by AIM2. These alterations of cell surface glycosylation by gene products that are not directly associated with the machinery for glycan generation direct attention to pursue analysis of glycosylation in MSI tumor cells on the level of target glycoproteins and open the way for functional studies.

Expression of mismatch repair proteins, hMLH1/hMSH2, in non-small cell lung cancer tissues and its clinical significance

BACKGROUND

hMLH1 and hMSH2 have been implicated to be involved in the DNA mismatch repair (MMR) system. The purpose of this study is to investigate the expression of hMLH1 and hMSH2 DNA MMR proteins in non-small cell lung cancer (NSCLC) tissue and to elucidate their clinical significance.

METHODS

The hMLH1 and hMSH2 protein expression was evaluated by immunohistochemistry for a consecutive series of 113 NSCLC patients. The expressions of each protein were examined for an association with the clinicopathological variables, including genetic alterations analyzed by high resolution fluorescent microsatellite analysis.

RESULTS

Regarding the hMLH1 expression, the MSI-positive patients showed significantly lower scores than the MSI-negative patients. For hMSH2 expression, the patients with a 20 or higher pack-year index (PYI) showed significantly higher scores than the patients with a PYI less than 20. The expression status of proteins did not affect both the disease free and overall survival of the patients. No significant correlation was observed among the scores for the proteins.

CONCLUSIONS

The expressions of hMLH1 and hMSH2 are independently regulated and play different roles in NSCLC. The genetic instability is possibly due to the reduced expression of hMLH1 protein, and hMSH2 expression is associated with smoking status.

[Lynch syndrome I: a case report]

INTRODUCTION

Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndromes I and II, accounts for about 5-8% of colorectal cancers. Lynch syndrome I is an autosomal dominant inherited disorder characterized by early onset of colorectal cancer, predominance of proximal and multiple tumors, and microsatellite instability. In order to identify HNPCC, the international "Amsterdam criteria" have been used.

CASE REPORT

The proband was a 40-year-old male who was admitted to hospital with a diagnosis of advanced rectal cancer. Left colectomy was carried out. A histopathologic diagnosis of poorly differentiated adenocarcinoma of clinical stage Dukes C was made. The family talking was done and it was revealed that the proband had five family members (one of first degree relative) with colorectal cancer, and two successive generations affected. All malignancy were diagnosed before 45 years of age. In one family member, metachronous transverse cancer was revealed 12 years after surgery for cecal adenocarcinoma.

DISCUSSION AND CONCLUSION

The main molecular cause for HNPCC is constitutional mutation in one of the mismatch repair (MMR) genes that regulate the excision of errors occurring during DNA replication. The most often are mutations of MLH1 and MSH2 genes, and microsatellite instability is present in about 90-95% HNPCC. In this report, we present a case of an HNPCC patient who met the Amsterdam criteria for Lynch syndrome I. Family members that fulfil the Amsterdam criteria should be investigated for mutation in MMR genes. The genetic tests are not routinely available, so colonoscopic screening of all asymptomatic family members older than 25 has been recommended.