Microsatellite instability in the management of colorectal cancer

Successful conversion surgery after comprehensive therapy in a patient with MSI-H but pMMR metastatic gastric mixed adenoneuroendocrine carcinoma: a case report and literature review

Gastric mixed adenoneuroendocrine carcinoma (MANEC) is a rare and highly aggressive malignancy characterized by both exocrine and neuroendocrine components. Treatment options for metastatic cases are limited, with typical therapeutic approaches involving a combination of chemotherapy and immunotherapy. A 68-year-old male with metastatic gastric MANEC was treated with targeted therapy, immunotherapy, and chemotherapy, including S-1, apatinib, cadonilimab, and paclitaxel. After six cycles, the liver metastases resolved completely, and the primary tumor achieved partial remission, leading to conversion surgery. The patient underwent a radical D2 gastrectomy with R0 resection, including proximal gastrectomy, splenectomy, omentectomy, and esophagogastric anastomosis, along with radiofrequency ablation of liver metastases. Postoperative pathology confirmed the disappearance of liver metastases but revealed residual adenocarcinoma in the primary gastric lesion and neuroendocrine components in the perigastric lymph nodes. The patient was discharged seven days post-surgery. Five months postoperatively, new liver metastases were detected, exhibiting neuroendocrine differentiation. The patient was subsequently treated with a maintenance regimen of S-1 and pembrolizumab. This case highlights the significant heterogeneity of gastric MANEC and the challenges in managing such cases. While conversion surgery can be effective in certain contexts, the high likelihood of postoperative recurrence and metastasis, particularly in neuroendocrine components, necessitates cautious consideration. Further research is needed to evaluate the long-term benefits of conversion surgery in metastatic gastric MANEC and to develop tailored therapeutic strategies.

A new strategy for immunotherapy of microsatellite-stable (MSS)-type advanced colorectal cancer: Multi-pathway combination therapy with PD-1/PD-L1 inhibitors

Colorectal cancer (CRC) is a frequent gastrointestinal malignancy with high rates of morbidity and mortality; 85% of these tumours are proficient mismatch repair (pMMR)-microsatellite instability-low (MSI-L)/microsatellite stable (MSS) CRC known as 'cold' tumours that are resistant to immunosuppressive drugs. Monotherapy with programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) inhibitors is ineffective for treating MSS CRC, making immunotherapy for MSS CRC a bottleneck. Recent studies have found that the multi-pathway regimens combined with PD-1/PD-L1 inhibitors can enhance the efficacy of anti-PD-1/PD-L1 in MSS CRC by increasing the number of CD8+ T cells, upregulating PD-L1 expression and improving the tumour microenvironment. This paper reviews the research progress of PD-1/PD-L1 inhibitors in combination with cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) inhibitors, oncolytic virus, intestinal flora, antiangiogenic agents, chemotherapy, radiotherapy and epigenetic drugs for the treatment of pMMR-MSI-L/MSS CRC.

Correlation between mismatch repair statuses and the prognosis of stage I-IV colorectal cancer

Background

The role of microsatellite instability (MSI) and prognosis for stage II-III colorectal cancer (CRC) has been described, but the role of MSI in stage I and IV CRC is controversial.

Methods

A total of 2,540 CRC patients were collected from Huzhou Central Hospital, China, from January 2006 to 2016, and 783 cases were excluded. This retrospective study illustrates the correlation between MMR status and prognosis for 1,757 CRC patients as well as the correlation between MSI and prognosis for CRC patients. Two groups were classified as MSI-H and MSI-L&MSS. If the expression of one or more mismatch repair (MMR) proteins was negative, it was considered as microsatellite instability high expression (MSI-H), whereas positive expression was considered as microsatellite instability low expression and microsatellite stability (MSI-L&MSS), as assessed by correlation analyses. Overall and disease-free survival were analyzed using the Kaplan-Meier method. Univariable and multivariable analyses were conducted using Cox regression.

Results

Preoperative serum S-CEA, positive lymph, tumor size, pathologic tumor (Pt) status, node (N) stage, differentiation, chemotherapy, and the 8th Edition of the American Joint Committee on Cancer (AJCC-8) were significantly correlated with MSI (P=0.028, 0.037, 0.019, 0.007, 0.002, <0.001, <0.001, and <0.001, respectively), whereas tumor location was not associated with MSI. Univariable and multivariable analyses showed that MSI was an independent factor for CRC. The 5-year overall survival (OS) and 5-year disease-free survival (DFS, P<0.001) rates differed significantly between the two groups in stages II, III, and IV, whereas stage I did not show a significant difference (P>0.05).

Conclusion

MSI-H was associated with a good prognosis for stages II to IV, whereas stage I did not show any significant correlation. Moreover, MSI expression was an independent prognostic factor.

Chimeric TβRII-SE/Fc overexpression by a lentiviral vector exerts strong antitumoral activity on colorectal cancer-derived cell lines in vitro and on xenografts

The TGF signaling pathway is a key regulator of cancer progression. In this work, we report for the first time the antitumor activity of TβRII-SE/Fc, a novel peptibody whose targeting domain is comprised of the soluble endogenous isoform of the human TGF-β type II receptor (TβRII-SE). Overexpression of TβRIISE/Fc reduces in vitro cell proliferation and migration while inducing cell cycle arrest and apoptosis in human colorectal cancer-derived cell lines. Moreover, TβRII-SE/Fc overexpression reduces tumorigenicity in BALB/c nude athymic mice. Our results revealed that TRII-SE/Fc-expressing tumors were significantly reduced in size or were even incapable of developing. We also demonstrated that the novel peptibody has the ability to inhibit the canonical TGF-β and BMP signaling pathways while identifying SMAD-dependent and independent proteins involved in tumor progression that are modulated by TβRII-SE/Fc. These findings provide insights into the underlying mechanism responsible for the antitumor activity of TβRII-SE/Fc. Although more studies are required to demonstrate the effectiveness and safety of the novel peptibody as a new therapeutic for the treatment of cancer, our initial in vitro and in vivo results in human colorectal tumor-derived cell lines are highly encouraging. Our results may serve as the foundation for further research and development of a novel biopharmaceutical for oncology.

A robust microsatellite instability detection model for unpaired colorectal cancer tissue samples

BACKGROUND

Microsatellite instability (MSI) is a key biomarker for cancer immunotherapy and prognosis. Integration of MSI testing into a next-generation-sequencing (NGS) panel could save tissue sample, reduce turn-around time and cost, and provide MSI status and comprehensive genomic profiling in single test. We aimed to develop an MSI calling model to detect MSI status along with the NGS panel-based profiling test using tumor-only samples.

METHODS

From January 2019 to December 2020, a total of 174 colorectal cancer (CRC) patients were enrolled, including 31 MSI-high (MSI-H) and 143 microsatellite stability (MSS) cases. Among them, 56 paired tumor and normal samples (10 MSI-H and 46 MSS) were used for modeling, and another 118 tumor-only samples were used for validation. MSI polymerase chain reaction (MSI-PCR) was performed as the gold standard. A baseline was built for the selected microsatellite loci using the NGS data of 56 normal blood samples. An MSI detection model was constructed by analyzing the NGS data of tissue samples. The performance of the model was compared with the results of MSI-PCR.

RESULTS

We first intersected the target genomic regions of the NGS panels used in this study to select common microsatellite loci. A total of 42 loci including 23 mononucleotide repeat sites and 19 longer repeat sites were candidates for modeling. As mononucleotide repeat sites are more sensitive and specific for detecting MSI status than sites with longer length motif and the mononucleotide repeat sites performed even better than the total sites, a model containing 23 mononucleotide repeat sites was constructed and named Colorectal Cancer Microsatellite Instability test (CRC-MSI). The model achieved 100% sensitivity and 100% specificity when compared with MSI-PCR in both training and validation sets. Furthermore, the CRC-MSI model was robust with the tumor content as low as 6%. In addition, 8 out of 10 MSI-H samples showed alternations in the four mismatch repair genes ( MLH1 , MSH2 , MSH6 , and PMS2 ).

CONCLUSION

MSI status can be accurately determined along the targeted NGS panels using only tumor samples. The performance of mononucleotide repeat sites surpasses loci with longer repeat motif in MSI calling.

Integrative analysis of WDR12 as a potential prognostic and immunological biomarker in multiple human tumors

Background: Mammalian WD-repeat protein 12 (WDR12), a family member of proteins containing repeats of tryptophan-aspartic acid (WD), is a potential homolog of yeast Ytm1p and consists of seven repeats of WD. Aim of the study: This study aims to investigate the potential oncogenic effects of WDR12 in various human malignancies throughout a pan-cancer analysis that has been carried out to examine the various patterns in which this gene is expressed and behaves in tumor tissues. Methods: Herein, we used The Cancer Genome Atlas (TCGA) and various computational tools to explore expression profiles, prognostic relevance, genetic mutations, immune cell infiltration, as well as the functional characteristics of WDR12 in multiple human cancers. Results: We found that WDR12 was inconsistently expressed in various cancers and that variations in WDR12 expression predicted survival consequences for cancer patients. Furthermore, we observed a significant correlation between WDR12 gene mutation levels and the prognosis of some tumors. Furthermore, significant correlations were found between WDR12 expression patterns and cancer-associated fibroblast (CAF) infiltration, myeloid-derived suppressor cells (MDSCs), tumor mutation burden, microsatellite instability and immunoregulators. Ultimately, pathway enrichment analysis revealed that WDR12-related pathways are involved in carcinogenesis. Conclusions: The findings of our study are stisfactory, demonstrating that WDR12 could serve as a promising reliable prognostic biomarker, as well as a therapeutic target for novel cancer therapeutic approaches.

Comprehensive Study of Microsatellite Instability Testing and Its Comparison With Immunohistochemistry in Gastric Cancers

PURPOSE

In this study, polymerase chain reaction (PCR)-based microsatellite instability (MSI) testing was comprehensively analyzed and compared with immunohistochemistry (IHC) for mismatch repair (MMR) protein expression in patients with gastric cancer (GC).

MATERIALS AND METHODS

In 5,676 GC cases, PCR-based MSI testing using five microsatellites (BAT-26, BAT-25, D5S346, D2S123, and D17S250) and IHC for MLH1 were performed. Re-evaluation of MSI testing/MLH1 IHC and additional IHC for MSH2, MSH6, and PMS2 were performed in discordant/indeterminate cases.

RESULTS

Of the 5,676 cases, microsatellite stable (MSS)/MSI-low and intact MLH1 were observed in 5,082 cases (89.5%), whereas MSI-high (MSI-H) and loss of MLH1 expression were observed in 502 cases (8.8%). We re-evaluated the remaining 92 cases (1.6%) with a discordant/indeterminate status. Re-evaluation showed 1) 37 concordant cases (0.7%) (18 and 19 cases of MSI-H/MMR-deficient (dMMR) and MSS/MMR-proficient (pMMR), respectively), 2) 6 discordant cases (0.1%) (3 cases each of MSI-H/pMMR and MSS/dMMR), 3) 14 MSI indeterminate cases (0.2%) (1 case of dMMR and 13 cases of pMMR), and 4) 35 IHC indeterminate cases (0.6%) (22 and 13 cases of MSI-H and MSS, respectively). Finally, MSI-H or dMMR was observed in 549 cases (9.7%), of which 47 (0.8%) were additionally confirmed as MSI-H or dMMR by re-evaluation. Sensitivity was 99.3% for MSI testing and 95.4% for MMR IHC.

CONCLUSIONS

Considering the low incidence of MSI-H or dMMR, discordant/indeterminate results were occasionally identified in GCs, in which case complementary testing is required. These findings could help improve the accuracy of MSI/MMR testing in daily practice.

Potential Influence of Age and Diabetes Mellitus Type 1 on MSH2 (MutS homolog 2) Expression in a Rat Kidney Tissue

Background: Homeostasis of proliferating tissues is strongly dependent on intact DNA. Both neoplastic and non-neoplastic diseases have been associated with MSH2 (MutS homolog 2, a mismatch repair protein) deficiency. In this study, we examined how age and diabetes mellitus influence the expression of MSH2 in the kidney. Methods: To study the effect of age, three groups of healthy rats were formed: 2 months, 8 months, and 14 months old. Two groups of diabetic rats were formed: 8 months old and 14 months old. Expression of MSH2 in the kidney was studied by quantifying immunofluorescent staining. Results: Age was identified as the main factor that influences MSH2 expression in kidneys. The effect of age followed parabolic dynamics, with peak expression at 8 months of age and similar levels at 2 and 14 months. Diabetes had an age-dependent effect, which manifested as the increase of MSH2 expression in 14-month-old diabetic rats in comparison to healthy animals. Conclusions: Age influences MSH2 expression in the kidney more than diabetes mellitus. Since ageing is a risk factor for kidney neoplasia, downregulation of MSH2 in older rats might represent one of the pro-oncogenic mechanisms of ageing at a molecular level.

Progress in the Application of Immune Checkpoint Inhibitor-Based Immunotherapy for Targeting Different Types of Colorectal Cancer

Colorectal cancer (CRC), a common malignant disease, has the second highest mortality rate among all cancer types. Due to the diversity and heterogeneity of CRC, few effective treatment strategies have been developed in recent years, except for surgical resection. As immunotherapy has become a revolutionary treatment after surgery, along with chemoradiotherapy and targeted therapy, numerous basic research studies and clinical trials have been conducted on CRC. Therefore, immune checkpoint inhibitor (ICI) therapy has become the main anti-CRC immunotherapy method used at present. With the rapid development of biotechnology and cell research, an increasing number of monotherapy or combination therapy strategies using ICIs for CRC have been designed in recent years. Methods to classify and review ICI strategies for different types of CRC to better guide treatment are continuously investigated. However, the identification of why the ICIs would be more effective in targeting particular subtypes of CRC such as high microsatellite instability (MSI-H) is more important because of the different immune backgrounds in patients. This review intends to classify different subtypes of CRC and summarizes the basic and clinical studies on ICIs for each subtype of CRC currently available. In addition, we also attempt to briefly discuss the progress in immunotherapy methods other than ICI therapy, such as chemoimmunotherapy strategy, chimeric antigen receptor-modified T (CAR-T) cells, or immunotherapy based on oncolytic viruses. Finally, we provide a perspective on the development of immunotherapy in the treatment of CRC and attempt to propose a new systematic classification of CRC based on immunological strategies, which may improve guidance for the selection of immunotherapy strategies for different subtypes of CRC in the future.

MSIsensor-ct: microsatellite instability detection using cfDNA sequencing data

MOTIVATION

Microsatellite instability (MSI) is a promising biomarker for cancer prognosis and chemosensitivity. Techniques are rapidly evolving for the detection of MSI from tumor-normal paired or tumor-only sequencing data. However, tumor tissues are often insufficient, unavailable, or otherwise difficult to procure. Increasing clinical evidence indicates the enormous potential of plasma circulating cell-free DNA (cfNDA) technology as a noninvasive MSI detection approach.

RESULTS

We developed MSIsensor-ct, a bioinformatics tool based on a machine learning protocol, dedicated to detecting MSI status using cfDNA sequencing data with a potential stable MSIscore threshold of 20%. Evaluation of MSIsensor-ct on independent testing datasets with various levels of circulating tumor DNA (ctDNA) and sequencing depth showed 100% accuracy within the limit of detection (LOD) of 0.05% ctDNA content. MSIsensor-ct requires only BAM files as input, rendering it user-friendly and readily integrated into next generation sequencing (NGS) analysis pipelines.

AVAILABILITY

MSIsensor-ct is freely available at https://github.com/niu-lab/MSIsensor-ct.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Briefings in Bioinformatics online.

ATMIN Suppresses Metastasis by Altering the WNT-Signaling Pathway via PARP1 in MSI-High Colorectal Cancer

BACKGROUND

Constant DNA damage occurs in cells, and the cells are programmed to respond constitutively. This study explored the roles of ataxia-telangiectasia mutated interactor (ATMIN), one of the impaired pathways involving the DNA damage response (DDR) in mismatch repair-deficient [microsatellite instability (MSI)-high] colorectal carcinoma (CRC).

METHODS

Expression of ATMIN messenger RNA (mRNA) was detected in CRC specimens with microsatellite instability (MSI) characteristics. The effects of ectopic ATMIN expression and ATMIN knockdown on invasion abilities were evaluated in MSI-high cell lines, and liver metastasis ability was investigated in vivo. Protein-protein interactions were assessed by coimmunoprecipitation analyses in vitro.

RESULTS

Decreased ATMIN expression was positively correlated with advanced stage of disease (P < 0.05), lymph node metastases (P < 0.05), and deeper invasion (P < 0.05) in MSI-high tumors. Transient or stable ATMIN knockdown significantly increased cell motility. Moreover, in the high-throughput microarray and gene set enrichment analysis, ATMIN was shown to act on the Wnt-signaling pathway via PARP1. This cascade influences β-catenin/transcription factor 4 (TCF4) binding affinity in MSI-high tumors, and PARP1 inhibition significantly decreased the number of metastases from ATMIN knockdown cancer cells.

CONCLUSIONS

The results not only indicated the critical role of ATMIN, but also shed new light on PARP1 inhibitors, providing a basis for further clinical trials of MSI-high CRC.

Tumor microenvironment-associated gene C3 can predict the prognosis of colorectal adenocarcinoma: a study based on TCGA

BACKGROUND

Colorectal cancer is one of the most common malignancies. With continuous exploration of the interaction between tumor cells and the immune system, tumor immunotherapy has become a revolution. However, CRC remains one of the less effective tumors for immunotherapy. The tumor microenvironment plays an important role in tumorigenesis and progression. The aim of this study is to explore tumor microenvironment-related genes that can predict the prognosis of colorectal adenocarcinoma, and also to provide new ideas for the mechanism of tumor development as well as immunotherapy.

METHODS

After estimating Stromalscore and Immunescore of colorectal adenocarcinoma tumor samples according to RNA-Seq expression data downloaded from TCGA, we screened for TME-related differential genes. We filtered prognosis-related core genes by constructing protein-protein interaction networks and making one-factor cox analysis for prognosis. Finally, the relative content of 22 immune cells in tumor tissues was evaluated, and then immune cells associated with core genes were identified.

RESULTS

We screened 773 differential genes related to the TME. Then we identified C3 as a core gene associated with prognosis. Single gene analysis showed that C3 expression was significantly higher in tumor tissues than in normal tissues (p < 0.001). High C3 expression was associated with lower overall survival (p = 0.046). Tumor immune cell analysis showed that mast cells resting, mast cells activated, T cells CD4 memory activated, eosinophils, and macrophages M0 were C3-associated immune cells.

CONCLUSIONS

C3 has potential as a biomarker for colorectal adenocarcinoma and could provide new research ideas for the diagnosis and treatment of colorectal adenocarcinoma, especially for immunotherapy.

A next-generation sequencing-based strategy combining microsatellite instability and tumor mutation burden for comprehensive molecular diagnosis of advanced colorectal cancer

Background

Mismatch repair (MMR)/microsatellite instability (MSI) and tumor mutational burden (TMB) are independent biomarkers that complement each other for predicting immune checkpoint inhibitors (ICIs) efficacy. Here we aim to establish a strategy that integrates MSI and TMB determination for colorectal cancer (CRC) in one single assay.

Methods

Surgical or biopsy specimens retrospectively collected from CRC patients were subjected to NGS analysis. Immunohistochemistry (IHC) and polymerase chain reaction (PCR) were also used to determine MMR/MSI for those having enough tissues. The NGS-MSI method was validated against IHC and PCR. The MSI-high (MSI-H) or microsatellite stable (MSS) groups were further stratified based on tumor mutational burden, followed by validation using the The Cancer Genome Atlas (TCGA) CRC dataset. Immune microenvironment was evaluated for each subgroup be profiling the expression of immune signatures.

Results

Tissues from 430 CRC patients were analyzed using a 381-gene NGS panel. Alterations in KRAS, NRAS, BRAF, and HER2 occurred at a significantly higher incidence among MSI-H tumors than in MSS patients (83.6% vs. 58.4%, p = 0.0003). A subset comprising 98 tumors were tested for MSI/MMR using all three techniques, where NGS proved to be 99.0 and 93.9% concordant with PCR and IHC, respectively. Four of the 7 IHC-PCR discordant cases had low TMB (1.1–8.1 muts/Mb) and were confirmed to have been misdiagnosed by IHC. Intriguingly, 4 of the 66 MSS tumors (as determined by NGS) were defined as TMB-high (TMB-H) using a cut-off of 29 mut/Mb. Likewise, 15 of the 456 MSS tumors in the TCGA CRC cohort were also TMB-H with a cut-off of 9 muts/Mb. Expression of immune signatures across subgroups (MSS-TMB-H, MSI-H-TMB-H, and MSS-TMB-L) confirmed that the microenvironment of the MSS-TMB-H tumors was similar to that of the MSI-H-TMB-H tumors, but significantly more immune-responsive than that of the MSS-TMB-L tumors, indicating that MSI combined with TMB may be more precise than MSI alone for immune microenvironment prediction.

Conclusion

This study demonstrated that NGS panel-based method is both robust and tissue-efficient for comprehensive molecular diagnosis of CRC. It also underscores the importance of combining MSI and TMB information for discerning patients with different microenvironment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07942-1.

[Clinicopathological features and types of microsatellite instability in 1394 patients with colorectal cancer]

OBJECTIVE

To explore the clinicopathological features and types of genic mutations in DNA mismatch repair (MMR) in colorectal cancer (CRC).

METHODS

Immunohistochemistry was used to determine the expression of MMR proteins in 1394 patients with CRC, and PCR-capillary electrophoresis (PCR-CE) was used to detect microsatellite instability (MSI) in 106 cases of defective MMR (dMMR), 46 cases of proficient MMR (pMMR) with heterogeneous expression and 147 randomly selected cases of pMMR. The relationship between the expressions of MMR proteins and the clinicopathological features of the patients was evaluated. The consistency between the results of immunohistochemistry and PCR-CE was assessed.

RESULTS

Immunohistochemical staining showed an incidence of dMMR of 7.6% in the patients. The main type of dMMR was co-deletion of MLH1 and PMS2, accounting for 55.7% of the total dMMR cases. The deletion of MMR proteins was significantly correlated with the patients' age, tumor location, tumor size, gross type, histological type, degree of differentiation, lymph node status and TNM stage (P < 0.05), but not with gender (P > 0.05). The total accordance rate of immunohistochemistry and PCR-CE was 98.7% in these patients.

CONCLUSIONS

The main type of dMMR is co-deletion of MLH1 and PMS2 in patients with colorectal cancer. dMMR colorectal cancer has typical clinicopathological features and a lower incidence in China than in Western countries. The results of immunohistochemistry and PCR-CE are highly consistent for detecting dMMR in colorectal cancer patients.

Molecular Insights Into Colorectal Carcinoma

Colorectal carcinoma (CRC) is one of the most common type of cancers and a leading cause of cancer-related deaths worldwide and in the United States. CRC is a heterogeneous disease with a well-characterized stepwise accumulation molecular alteration associated with adenoma formation and progression to carcinoma. We review the genomic and epigenomic pathways, including chromosomal instability, microsatellite instability, and epigenetic instability or CpG island methylator phenotype, their characteristics, and prognosis. We describe the four consensus molecular subtypes of CRC established by the international Colorectal Cancer Subtyping Consortium, their mechanisms to develop cancer, molecular characterization, clinical features, and prognosis. Finally, we review currently used predictive biomarkers.

A novel NGS-based microsatellite instability (MSI) status classifier with 9 loci for colorectal cancer patients

Background

With the recent emergence of immune checkpoint inhibitors, microsatellite instability (MSI) status has become an important biomarker for immune checkpoint blockade therapy. There are growing technical demands for the integration of different genomic alterations profiling including MSI analysis in a single assay for full use of the limited tissues.

Methods

Tumor and paired control samples from 64 patients with primary colorectal cancer were enrolled in this study, including 14 MSI-high (MSI-H) cases and 50 microsatellite stable (MSS) cases determined by MSI-PCR. All the samples were sequenced by a customized NGS panel covering 2.2 MB. A training dataset of 28 samples was used for selection of microsatellite loci and a novel NGS-based MSI status classifier, USCI-msi, was developed. NGS-based MSI status, single nucleotide variant (SNV) and tumor mutation burden (TMB) were detected for all patients. Most of the patients were also independently detected by immunohistochemistry (IHC) staining.

Results

A 9-loci model for detecting microsatellite instability was able to correctly predict MSI status with 100% sensitivity and specificity compared with MSI-PCR, and 84.3% overall concordance with IHC staining. Mutations in cancer driver genes (APC, TP53, and KRAS) were dispersed in MSI-H and MSS cases, while BRAF p.V600E and frameshifts in TCF7L2 gene occurred only in MSI-H cases. Mismatch repair (MMR)-related genes are highly mutated in MSI-H samples.

Conclusion

We established a new NGS-based MSI classifier, USCI-msi, with as few as 9 microsatellite loci for detecting MSI status in CRC cases. This approach possesses 100% sensitivity and specificity, and performed robustly in samples with low tumor purity.

Immunogenic cell death in colon cancer prevention and therapy

Colorectal cancer (CRC) is a leading cause of cancer-related death worldwide. The colonic mucosa constitutes a critical barrier and a major site of immune regulation. The immune system plays important roles in cancer development and treatment, and immune activation caused by chronic infection or inflammation is well-known to increase cancer risk. During tumor development, neoplastic cells continuously interact with and shape the tumor microenvironment (TME), which becomes progressively immunosuppressive. The clinical success of immune checkpoint blockade therapies is limited to a small set of CRCs with high tumor mutational load and tumor-infiltrating T cells. Induction of immunogenic cell death (ICD), a type of cell death eliciting an immune response, can therefore help break the immunosuppressive TME, engage the innate components, and prime T cell-mediated adaptive immunity for long-term tumor control. In this review, we discuss the current understanding of ICD induced by antineoplastic agents, the influence of driver mutations, and recent developments to harness ICD in colon cancer. Mechanism-guided combinations of ICD-inducing agents with immunotherapy and actionable biomarkers will likely offer more tailored and durable benefits to patients with colon cancer.

Standardized Pathology Report for Colorectal Cancer, 2nd Edition

The first edition of the 'Standardized Pathology Report for Colorectal Cancer,' which was developed by the Gastrointestinal Pathology Study Group (GIP) of the Korean Society of Pathologists, was published 13 years ago. Meanwhile, there have been many changes in the pathologic diagnosis of colorectal cancer (CRC), pathologic findings included in the pathology report, and immunohistochemical and molecular pathology required for the diagnosis and treatment of colorectal cancer. In order to reflect these changes, we (GIP) decided to make the second edition of the report. The purpose of this standardized pathology report is to provide a practical protocol for Korean pathologists, which could help diagnose and treat CRC patients. This report consists of "standard data elements" and "conditional data elements." Basic pathologic findings and parts necessary for prognostication of CRC patients are classified as "standard data elements," while other prognostic factors and factors related to adjuvant therapy are classified as "conditional data elements" so that each institution could select the contents according to the characteristics of the institution. The Korean version is also provided separately so that Korean pathologists can easily understand and use this report. We hope that this report will be helpful in the daily practice of CRC diagnosis.

Construction of a nomogram to predict overall survival for patients with M1 stage of colorectal cancer: A retrospective cohort study

BACKGROUND

The M1 stage of colorectal cancer (CRC) has a poor prognosis. The aim of this study is to develop a reliable tool for the prediction for CRC patients with M1 stage, thus assisting the strategy of clinical diagnosis and treatment.

METHODS

CRC patient information collected in the Surveillance, Epidemiology, and End Results (SEER) database between 2004 and 2015 was extracted and evaluated. Multivariate analysis with Cox proportional hazards regression identified risk factors that predicted overall survival (OS) and the results were used to construct a nomogram to predict 3-, and 5-year OS in CRC patients with M1 stage. The Kaplan-Meier curve was plotted to evaluate OS differences.

RESULTS

A total of 19,796 patients from the SEER database were included for analysis. All patients were randomly allocated to 2 cohorts, the training cohort (n = 13,860) and the validation cohort (n = 5936). Patients' age at diagnosis; gender; race; tumor site; tumor grade; T and N stage; brain, lung, bone, and liver metastasis status; marital status; and therapy were associated with survival in the multivariate models. All these factors were incorporated to construct a nomogram. Additionally, we divide all 19,796 patients into high-risk group and low-risk group according to our nomogram, and plotted Kaplan-Meier curve. The result indicated that patients with higher risk had worse survival outcomes.

CONCLUSIONS

Our predictive model has the potential to provide an individualized risk estimate of survival in CRC patients with M1 stage.

The Four Horsemen in Colon Cancer

Worldwide, neoplasms of the gastrointestinal tract have a very high incidence and mortality. Among these, colorectal cancer, which includes colon and rectum malignancies, representing both highest incidence and mortality. While gallbladder cancer, another neoplasm associated to gastrointestinal tract occurs less frequently. Genetic factors, inflammation and nutrition are important risk factors associated with colorectal cancer development. Likewise, pathogenic microorganisms inducing intestinal dysbiosis have become an important scope to determine the role of bacterial infection on tumorigenesis. Interestingly, in human biopsies of different types of gastrointestinal tract cancer, the presence of different bacterial strains, such as Fusobacterium nucleatum, Escherichia coli, Bacteroides fragilis and Salmonella enterica have been detected, and it has been considered as a high-risk factor to cancer development. Therefore, pathogens infection could contribute to neoplastic development through different mechanisms; including intestinal dysbiosis, inflammation, evasion of tumoral immune response and activation of pro-tumoral signaling pathways, such as β catenin. Here, we have reviewed the suggested bacterial molecular mechanisms and their possible role on development and progression of gastrointestinal neoplasms, focusing mainly on colon neoplasms, where the bacteria Fusobacterium nucleatum, Escherichia coli, Bacteroides fragilis and Salmonella enterica infect.

Prevalence and molecular characteristics of defective mismatch repair epithelial ovarian cancer in a Japanese hospital-based population

Background

The prevalence and molecular characteristics of defective mismatch repair epithelial ovarian cancers in the Japanese population have scarcely been investigated.

Methods

Immunohistochemistry for mismatch repair proteins (MLH1, MSH2, MSH6 and PMS2) was performed in formalin-fixed paraffin-embedded sections prepared from resected primary epithelial ovarian cancers in patients who underwent oophorectomy at our institution between April 2005 and September 2014. Genetic and/or epigenetic alterations of the mismatch repair genes were investigated in patients with loss of any mismatch repair proteins in the tumor.

Results

There were 305 patients with a median age of 54 years (range, 18-83 years). Loss of expression in the ovarian tumor of one or more mismatch repair proteins was observed in 3 of the 305 patients (0.98%): 2 patients MLH1/PMS2 loss and 1 patient showed MSH2/MSH6 loss. Genetic testing of these three patients failed to reveal any pathogenic germline mutations of MLH1 or MSH2. One patient with MLH1/PMS2 loss showed hypermethylation of the promoter region of MLH1. Somatic mutations were found in each of the alleles of MLH1 (c.545dupG and deletion of exons 2-19) in the other patient with MLH1/PMS2 loss. In the patient with MSH2/MSH6 loss, two somatic mutations were detected in MSH2 (c.229_230delAG and c.1861C>T), although we could not determine whether these mutations were biallelic or not.

Conclusions

The prevalence of defective mismatch repair epithelial ovarian cancer in the Japanese hospital-based population was extremely low. Molecular mechanism involved in such defective mismatch repair ovarian cancers seems to be epigenetic events through MLH1 promotor hypermethylation or somatically mutated mismatch repair genes without germline mismatch repair mutation.

Noninvasive Biomarkers of Colorectal Cancer: Role in Diagnosis and Personalised Treatment Perspectives

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths worldwide. It has been estimated that more than one-third of patients are diagnosed when CRC has already spread to the lymph nodes. One out of five patients is diagnosed with metastatic CRC. The stage of diagnosis influences treatment outcome and survival. Notwithstanding the recent advances in multidisciplinary management and treatment of CRC, patients are still reluctant to undergo screening tests because of the associated invasiveness and discomfort (e.g., colonoscopy with biopsies). Moreover, the serological markers currently used for diagnosis are not reliable and, even if they were useful to detect disease recurrence after treatment, they are not always detected in patients with CRC (e.g., CEA). Recently, translational research in CRC has produced a wide spectrum of potential biomarkers that could be useful for diagnosis, treatment, and follow-up of these patients. The aim of this review is to provide an overview of the newer noninvasive or minimally invasive biomarkers of CRC. Here, we discuss imaging and biomolecular diagnostics ranging from their potential usefulness to obtain early and less-invasive diagnosis to their potential implementation in the development of a bespoke treatment of CRC.

Detection of DNA Mismatch Repair Protein Abnormalities in Sudanese Colorectal Cancer Patients Using Immunohistochemical Methods

PURPOSE

DNA mismatch repair (MMR) protein abnormalities among 42 Sudanese colorectal cancer (CRC) patients were assessed.

METHODS

Sections were stained by immunohistochemical method to assess the abnormalities of MLH1, MSH2, MSH6, and PMS2.

RESULTS

Of the 42 included cases, 34 (80.95%) were MMR protein positive for all MMR proteins under assessment, 3 (7.14%) MSH2 inadequate, and 1 (2.38%) MSH6 inadequate. Abnormal MMR protein expression was found in 4 (9.5%) cases. Of these, 2 (50%) were MSH2 and MSH6 negative and 2 (50%) were MLH1 and PMS2 negative. Regarding microsatellite instability (MSI) results, the three cases that were MSH2 inadequate and positive for the rest by immunohistochemistry (IHC) showed stable results with both BAT 25 and 26. The case that was MSH6 inadequate showed stable results with both BAT 25 and 26. The 2 cases with MSH2- and MSH6-negative results were unstable with both BAT 25 and 26. Of the two cases that were MLH1 and PMS2 negative, one case showed non-evaluable results with both BAT 25 and 26 while the other case was unstable with BAT 26 and not evaluable with BAT 25.

CONCLUSIONS

The percentage of MMR protein-negative cases in Sudanese CRC patients appears to be relatively low compared to what is generally reported in certain studies in different countries. Furthermore, MLH1 and PMS2 and MSH2 and MSH6 abnormal expression detected by IHC seems to be the most common form of MMR protein abnormalities in Sudanese CRC patients. Concerning the results of IHC, MLH1 and MSH2 seem to be the most inactivated MMR genes in Sudanese CRC patients.

Clinicopathologic features of colorectal carcinoma: features predicting higher T-stage and nodal metastasis

OBJECTIVES

A rising frequency of colorectal carcinoma has been noted in recent years in Pakistan. In the present study, we aimed to evaluate clinicopathologic features of colorectal carcinoma in our population so that protocols could be developed to stratify patients that may require further biomarker/molecular testing. Furthermore, histological features which predict higher T and N stage were also evaluated.

RESULTS

Median age at diagnosis was 54.5 (19-85) years. 79% cases were of conventional adenocarcinoma while 13% cases were of mucinous carcinoma. Most of the cases were at T3 stage (81%), while 27 and 68% of cases revealed lymphovascular invasion and nodal metastasis respectively. Mucinous and signet ring tumors were associated with a higher N stage. Pre-existing polyp was associated with lower T and N stage. We found a high proportion of our cases to present at advanced T-stage. Tumor grade and lymphovascular invasion were found to be associated with higher N-stage while tumor infiltrating lymphocytes was associated with lower T and N-stage. Moreover, a high frequency of mucinous differentiation may be linked to microsatellite instability in our cases of colorectal carcinoma; therefore, we suggest that microsatellite instability testing in colorectal carcinoma should be evaluated in our setup.

Hypermutated tumours in the era of immunotherapy: The paradigm of personalised medicine

Immune checkpoint inhibitors have demonstrated unprecedented clinical activity in a wide range of cancers. Significant therapeutic responses have recently been observed in patients presenting mismatch repair-deficient (MMRD) tumours. MMRD cancers exhibit a remarkably high rate of mutations, which can result in the formation of neoantigens, hypothesised to enhance the antitumour immune response. In addition to MMRD tumours, cancers mutated in the exonuclease domain of the catalytic subunit of the DNA polymerase epsilon (POLE) also exhibit an ultramutated genome and are thus likely to benefit from immunotherapy. In this review, we provide an overview of recent data on hypermutated tumours, including MMRD and POLE-mutated cancers, with a focus on their distinctive clinicopathological and molecular characteristics as well as their immune environment. We also discuss the emergence of immune therapy to treat these hypermutated cancers, and we comment on the recent Food and Drug Administration approval of an immune checkpoint inhibitor, the programmed cell death 1 antibody (pembrolizumab, Keytruda), for the treatment of patients with metastatic MMRD cancers regardless of the tumour type. This breakthrough represents a turning point in the management of these hypermutated tumours and paves the way for broader strategies in immunoprecision medicine.

Mismatch repair deficiency screening in colorectal carcinoma by a four-antibody immunohistochemical panel in Pakistani population and its correlation with histopathological parameters

Background

Microsatellite instability (MSI) operates as the second major pathway in the colorectal carcinogenesis. Although genetic testing remains the gold standard for the detection of MSI, the College of American Pathologists (CAP) recommends an initial immunohistochemical workup with a four-antibody panel (MLH1, PMS2, MSH2, and MSH6) to screen for a defective mismatch repair system. An increased trend towards young age colorectal carcinoma (CRC) has been noticed in our population over recent years; however, neither screening for MSI by immunohistochemistry (IHC)/genetic testing was done nor were its morphological features studied. We aimed to determine the frequency of mismatch repair deficiency (dMMR) by loss of IHC expression of the aforementioned enzymes in CRC patients and its correlatation with clinicopathologic parameters.

Methods

This was a retrospective study conducted at Liaquat National Hospital, Karachi, between 2012 and 2015. A total of 100 cases of CRC were included in the study that underwent surgical resection. IHC stains using antibodies MLH1, PMS2, MSH2, and MSH6 were performed by DAKO EnVision method on representative tissue blocks. The results were interpreted by senior histopathologists and correlated with clinico-pathological parameters.

Results

A total of 100 cases of CRC were studied that included 51 males and 49 females. Thirty-four percent (n = 34) of the patients showed loss of IHC staining for MMR markers. Combined loss of expression for MLH1/PMS2 were observed in 16% (n = 16) of the cases. Loss of MSH2/MSH6 were seen in 6% (n = 6) of the cases. Loss of expression for all markers were noted in 7% (n = 7) of the cases. There were 5% (n = 5) of the cases that showed isolated loss of MLH1 only. The tumors with dMMR status were significantly associated with right-sided location (p = 0.013), exhibited intra-tumoral lymphocytosis (p = 0.007), and lymphovascular invasion (p = 0.043). No significant association was seen with gender, age, tumor stage, grade, or other morphological features.

Conclusion

The frequency of mismatch repair deficiency in CRC patients was found to be 34% in Pakistani population which warrants further genetic testing to exclude Lynch syndrome. Moreover, right-sided location and intra-tumoral lymphocyte count may be used to identify patients who may need further workup.

The current value of determining the mismatch repair status of colorectal cancer: A rationale for routine testing

Colorectal Cancer (CRC) is the third most prevalent cancer in men and women. Up to 15% of CRCs display microsatellite instability (MSI). MSI is reflective of a deficient mismatch repair (MMR) system and is most commonly caused by hypermethylation of the MLH1 promoter. However, it may also be due to autosomal dominant constitutional mutations in DNA MMR, termed Lynch Syndrome. MSI may be diagnosed via polymerase chain reaction (PCR) or alternatively, immunohistochemistry (IHC) can identify MMR deficiency (dMMR). Many institutions now advocate universal tumor screening of CRC via either PCR for MSI or IHC for dMMR to guide Lynch Syndrome testing. The association of sporadic MSI with methylation of the MLH1 promoter and an activating BRAF mutation may offer further exclusion criteria for genetic testing. Aside from screening for Lynch syndrome, MMR testing is important because of its prognostic and therapeutic implications. Several studies have shown MSI CRCs exhibit different clinicopathological features and prognosis compared to microsatellite-stable (MSS) CRCs. For example, response to conventional chemotherapy has been reported to be less in MSI tumours. More recently, MSI tumours have been shown to be responsive to immune-checkpoint inhibition providing a novel therapeutic strategy. This provides a rationale for routine testing for MSI or dMMR in CRC.

Screening for mismatch repair deficiency in colorectal cancer: data from three academic medical centers

Reflex immunohistochemistry (rIHC) for mismatch repair (MMR) protein expression can be used as a screening tool to detect Lynch Syndrome (LS). Increasingly the mismatch repair-deficient (dMMR) phenotype has therapeutic implications. We investigated the pattern and consequence of testing for dMMR in three Irish Cancer Centres (CCs). CRC databases were analyzed from January 2005-December 2013. CC1 performs IHC upon physician request, CC2 implemented rIHC in November 2008, and CC3 has been performing rIHC since 2004. The number of eligible patients referred to clinical genetic services (CGS), and the number of LS patients per center was determined. 3906 patients were included over a 9-year period. dMMR CRCs were found in 32/153 (21%) of patients at CC1 and 55/536 (10%) at CC2, accounting for 3% and 5% of the CRC population, respectively. At CC3, 182/1737 patients (10%) had dMMR CRCs (P < 0.001). Additional testing for the BRAF V600E mutation, was performed in 49 patients at CC3 prior to CGS referral, of which 29 were positive and considered sporadic CRC. Referrals to CGS were made in 66%, 33%, and 30% of eligible patients at CC1, CC2, and CC3, respectively. LS accounted for CRC in eight patients (0.8%) at CC1, eight patients (0.7%) at CC2, and 20 patients (1.2%) at CC3. Cascade testing of patients with dMMR CRC was not completed in 56%. Universal screening increases the detection of dMMR tumors and LS kindreds. Successful implementation of this approach requires adequate resources for appropriate downstream management of these patients.

Comparison of 627 patients with right- and left-sided colon cancer in China: Differences in clinicopathology, recurrence, and survival

Objective

Recent studies have reported increased mortality for right-sided colon cancers; however, the results are conflicting for different stage tumors. We examined the differences in clinicopathology between right- and left-sided colon cancers and the relationships between colon cancer location (right- and left-side) and 5-year disease-free survival (DFS) and overall survival (OS).

Methods

We identified patients from 2005 to 2008 with stage II/III colon cancer who underwent surgery for curative intent. We explored the impact of the tumor location on the postoperative DFS and OS using univariate and multivariate analyses.

Results

Of 627 patients, 50.6% (317/627) had right-sided colon cancer. These patients were more likely to have weight loss, second primary tumor, elevated preoperative carbohydrate antigen 19-9 (CA19-9), increased incidence of non-adenocarcinoma, more poorly differentiated tumors, vascular invasion, defective mismatch repair, and a lighter smoking history (P < 0.05). Right-sided colon cancer had a higher recurrence incidence compared with left-sided cancer (30.6% vs. 23.2%, P = 0.037), particularly with multiple metastatic sites in the first recurrence (17.5% vs. 5.6%, P = 0.020). Kaplan–Meier survival curves demonstrated a significant difference in the 5-year DFS rate between right- and left-sided cancers across all stages (68.1% vs. 75.2%, P = 0.043). However, there was no significant difference in the 5-year OS rate between the two groups (73.8% vs. 79.0%, P = 0.103). Subgroup analysis demonstrated that patients with left-sided colon cancer had a significantly better 5-year DFS and OS rates compared with those with right-sided disease at stage III (64.3% vs. 46.8%, P = 0.002; 69.5% vs. 53.5%, P = 0.006, respectively); there were no significant differences in the 5-year DFS and OS rates at stage II (85.2% vs. 85.9%, P = 0.819; 89.8% vs. 88.5%, P = 0.803, respectively). Adjusted Cox regression analysis showed no significant differences in the 5-year OS and DFS rates for stage II [hazard ratio (HR) = 1.203, 95% confidence interval (CI): 0.605–2.391, P = 0.598; HR = 0.980, 95% CI: 0.542–1.774, P = 0.948, respectively] or all stages combined (HR = 0.867, 95% CI: 0.613–1.227, P = 0.421; HR = 0.832, 95% CI: 0.606–1.142, P = 0.255, respectively). However, stage III left-sided cancer had higher 5-year OS and DFS rates (HR = 0.626, 95% CI: 0.414–0.948, P = 0.027; HR = 0.630, 95% CI: 0.428–0.926, P = 0.019, respectively).

Conclusion

We found that right- and left-sided colon cancers had significantly different clinicopathological characteristics. Right-sided colon cancer had a higher incidence of recurrence than left-sided disease. Patients with stage III right-sided colon cancer had a worse prognosis compared with those with stage III left-sided colon cancer.

Conventional colon adenomas harbor various disturbances in microsatellite stability and contain micro-serrated foci with microsatellite instability

Introduction

Colorectal cancer belongs to the most frequent occurring malignancies. A prediction of the clinical outcome and appropriate choice of neoadjuvant chemotherapy needs personalized insight to the main driving pathways. Because most CRCs have polyps as progenitor lesions, studying the pathways driving to adenomagenesis is no less important.

Goals

Our purpose was the evaluation of microsatellite stability status within conventional colon adenomas and also β-catenin, BRAFV600E and p53 contribution.

Material and methods

The cohort included 101 cases of typical colon adenomas with high grade epithelial dysplasia according to WHO. An immunohistochemistry method was used for the depiction of the expression of targeted proteins, as also their heterogeneity.

Results

Generally, we noted a 10% frequency of MSI events where MSI-H reached a 5% share occurred within the left colon and rectal polyps. β-catenin nuclear overexpression was noted with a 70% frequency and p53 with close to a 24% frequency. In addition, we found a presence of micro-serration foci more often within tubular adenomas, where focal MSI took place more often. Our results indicate that MSI events occur more often than had been theorized earlier. It results in tumour heterogeneity, more complex underlying pathways and finally ontogenetic molecular-diversity of tumours besides similar occurring histopathological features.

Serum and tissue markers in colorectal cancer: State of art

Colorectal cancer (CRC) represents one of the most commonly diagnosed cancers worldwide. It is the second leading cause of cancer death in Western Countries. In the last decade, the survival of patients with metastatic CRC has improved dramatically. Due to the advent of new drugs (irinotecan and oxaliplatin) and target therapies (i.e. bevacizumab, cetuximab, panitumab, aflibercept and regorafenib), the median overall survival has risen from about 12 mo in the mid nineties to 30 mo recently. Molecular studies have recently widened the opportunity for testing new possible markers, but actually, only few markers can be recommended for practical use in clinic. In the next future, the hope is to have a complete panel of clinical biomarkers to use in every setting of CRC disease, and at the same time: 1) to receive information about prognostic significance by their expression and 2) to be oriented in the choice of the adequate treatment. Moreover, molecular analyses have shown that the natural history of all CRCs is not the same. Individual patients with same stage tumors may have different long-term prognosis and response to therapy. In addition, some prognostic variables are likely to be more important than others. Here we review the role of serum and tissue markers according to the recently published English literature. This paper is an extension of the article "Biological and clinical markers in colorectal cancer: state of art" by Cappellani A published in Jan 2010.

Validation of a quantitative 12-multigene expression assay (Oncotype DX(®) Colon Cancer Assay) in Korean patients with stage II colon cancer: implication of ethnic differences contributing to differences in gene expression

Purpose

To evaluate the Recurrence Score^® of the quantitative 12-multigene expression assay and to determine risk groups based on the continuous Recurrence Score^® in Korean patients.

Method

A total of 95 patients with pathological T3N0 tumors and mismatch repair-proficient tumors were enrolled. The Recurrence Score^® was used to classify risk groups (low risk, <30; intermediate risk, 30–40; high risk, ≥41).

Results

Fifty-four patients (56.8%) were aged over 70 years. There were 49 men (51.6%) and 56 cases of right-sided colon cancer (58.9%). Eight cases (8.4%) had well-differentiated tumors, and 86 cases (90.5%) showed moderate differentiation. Only one case (1.1%) had a poorly differentiated tumor. Three patients (3.2%) had lymphovascular invasion. Sixty-one patients were identified as low risk (64.2%) and 34 patients as intermediate risk (35.8%). There were no high-risk patients. Although not significant, the 3-year recurrence risk increased with the Recurrence Score^®.

Conclusion

Distribution patterns of risk groups based on the Recurrence Score^®, particularly the absence of a high-risk group, were different from the prior validation studies. These findings suggest that ethnic differences between Koreans and Western patients are potential contributing factors for different gene expressions in the quantitative 12-multigene expression assay.

Unusual Presentation of Recurrent Early Stage Endometrial Carcinoma 28 Years after Primary Surgery

Endometrial carcinoma is the most common neoplasia of female genital tract. The prognosis of early stage disease (FIGO I and FIGO II) is excellent: recurrence after surgery is less than 15%, most of which are reported within 3 years after primary treatment. Herein we report a case of late rectal recurrence from FIGO Ib endometrial adenocarcinoma. Patient had also familiar and personal history of colonic adenocarcinoma and previous findings of microsatellite instability (MSI); molecular analysis evidenced heterozygotic somatic mutation in MLH1 gene. Twenty-eight years after hysterectomy and bilateral salpingoovariectomy, a rectal wall mass was detected during routine colonoscopy. Patients underwent CT scan, pelvic MRI, and rectal EUS with FNA: histopathological and immunohistochemical analysis revealed differentiated carcinoma cells of endometrial origin. No neoadjuvant treatment was planned and low rectal anterior resection with protective colostomy was performed; histology confirmed rectal lesion as metastasis from endometrial carcinoma. Recurrence of early stage endometrial carcinoma after a long period from primary surgery is possible. It is important to keep in mind this possibility in order to set a correct diagnostic and therapeutic algorithm, including preoperative immunohistochemical staining, and to plan a prolonged follow-up program.

Lower prevalence of Lynch syndrome in colorectal cancer patients in a Japanese hospital-based population

PURPOSE

The aim of this study was to investigate the prevalence of Lynch syndrome among Japanese patients with surgically resected colorectal cancer at a single institution.

METHODS

Of 616 colorectal cancer patients who underwent surgical operation in our institution from January 2005 to August 2010, immunohistochemistry analyses for mismatch repair proteins (MLH1, MSH2, MSH6, and PMS2) and microsatellite instability (MSI) testing for surgically resected, formalin-fixed paraffin-embedded colorectal cancer specimens from 138 colorectal cancer patients under 60 years of age were undertaken. Hypermethylation of the MLH1 promoter and BRAF mutation were analyzed where necessary.

RESULTS

Seven patients were identified as candidates for genetic testing by mismatch repair protein loss (n = 7) or MSI-H (n = 6). Methylation of MLH1 was detected in one case. Three patients were diagnosed with Lynch syndrome, comprising 2.2 % of the total colorectal cancer patients younger than 60 years of age.

CONCLUSION

The prevalence of Lynch syndrome among hospital-based diagnosed cancer patients may therefore be lower than expected in Japan compared with Western populations.

Association between mismatch repair gene and irinotecan-based chemotherapy in metastatic colon cancer

Mismatch repair (MMR) gene is closely related to the pathogenesis of colon cancer. This study aimed to evaluate the association between MMR status and efficacy of irinotecan-based chemotherapy. As a target of 5-FU, thymidylate synthase (TS) expression level might be influenced by irinotecan. Understanding whether this influence of TS is related with MMR status is helpful to the further exploration of the mechanism of irinotecan sensitivity in metastatic colon cancer with different MMR status. One hundred eighty-four patients with metastatic colon cancer receiving irinotecan-based chemotherapy for the first-line treatment were included. Correlations between MMR and clinicopathological characteristics and prognosis were determined. Two pairs of colon cancer cell lines (HCT-116-hMLH1(Vector) (deficient MMR, dMMR) versus HCT-116-hMLH1(+) (proficient MMR, pMMR); SW480-shRNA-hMLH1 (dMMR) versus SW480-shRNA-Control (pMMR)) were established by regulating MMR status. Sensitivity of these cell lines to irinotecan was determined by MTT assay. Regulation of TS by irinotecan was evaluated by western blotting and quantitative real-time PCR assay. dMMR accounted for 18.5 % and was related with proximal colon cancer (p = 0.005), poorly differentiated tumors (p = 0.018) and favorable efficacy with a higher disease control rate (DCR), a longer progression-free survival (PFS) and a trend of longer overall survival (OS). dMMR colon cancer cells were more sensitive to irinotecan. TS expression level was reduced more in dMMR cells after irinotecan treatment (p < 0.05). Our study favors an increased sensitivity of irinotecan in colon cancer with dMMR status. MMR status may be a predictive biomarker of response to irinotecan-based chemotherapy in metastatic colon cancer.

Beyond the island: epigenetic biomarkers of colorectal and prostate cancer

Epigenetic dysregulation is a common feature across all cancer types. Epigenetic mechanisms, from DNA methylation to histone modifications, allow for a vast number of cellular phenotypes to be created from the same genetic material. Just as certain genetic changes play a key role in tumor initiation and progression, epigenetic changes may also set the course of tumor development and be required for malignant transformation. The most frequently studied epigenetic changes investigated thus far are global genomic DNA hypomethylation along with specific hypermethylation, predominantly at promoter CpG islands of tumor suppressor genes. In addition to DNA methylation changes at CpG islands, there is an abundance of other epigenetic alterations occurring within cancer cells including DNA methylation alterations outside of CpG islands, non-CpG methylation, changes in cytosine oxidative species (hydroxymethylcytosine, formylcytosine, carboxylcytosine) levels, and histone modifications. This chapter examines epigenetic alterations beyond the island, and summarizes recent findings in DNA-based epigenetic regulation of the two most commonly diagnosed cancers in the Western world: colorectal cancer and prostate cancer.

Differential Features of Microsatellite-Unstable Colorectal Carcinomas Depending on EPCAM Expression Status

Background

Recent studies have revealed that a small subset of Lynch syndrome-associated colorectal carcinomas (CRCs) is caused by a germline EPCAM deletion-induced MSH2 epimutation. Based on the finding of this genetic alteration, we investigated the implications of EPCAM expression changes in microsatellite instability-high (MSI-H) CRCs.

Methods

Expression of EPCAM and DNA mismatch repair proteins was assessed by immunohistochemistry in 168 MSI-H CRCs. Using DNA samples of these tumors, MLH1 promoter methylation status was also determined by methylation-specific real-time polymerase chain reaction method (MethyLight).

Results

Among 168 MSI-H CRCs, complete loss (CL) and focal loss (FL) of EPCAM expression was observed in two (1.2%) and 22 (13.1%) cases, respectively. Both of the EPCAM-CL cases were found in MSH2-negative tumors without MLH1 promoter methylation. However, only nine of the 22 EPCAM-FL tumors had MSH2 deficiency. Of the 22 EPCAM-FL tumors, 13 showed MLH1 loss, and among them, nine cases were determined to have MLH1 methylation. EPCAM-FL was significantly associated with advanced stage (p=.043), distant metastasis (p=.003), poor differentiation (p=.001), and signet ring cell component (p=.004).

Conclusions

Loss of EPCAM expression is differentially associated with clinicopathological and molecular features, depending on the completeness of the loss, in MSI-H CRCs.

Molecular and prognostic heterogeneity of microsatellite-unstable colorectal cancer

Colorectal cancers (CRCs) with a high level of microsatellite instability (MSI-H) are clinicopathologically distinct tumors characterized by predominance in females, proximal colonic localization, poor differentiation, mucinous histology, tumor-infiltrating lymphocytes, a Crohn’s-like lymphoid reaction and a favorable prognosis. In terms of their molecular features, MSI-H CRCs are heterogeneous tumors associated with various genetic and epigenetic alterations, including DNA mismatch repair deficiency, target microsatellite mutations, BRAF mutations, a CpG island methylator phenotype-high (CIMP-H) status, and a low level of genomic hypomethylation. The molecular heterogeneity of MSI-H CRCs also depends on ethnic differences; for example, in Eastern Asian countries, relatively low frequencies of CIMP-H and BRAF mutations have been observed in MSI-H CRCs compared to Western countries. Although the prognostic features of MSI-H CRCs include a favorable survival of patients and low benefit of adjuvant chemotherapy, there may be prognostic differences based on the molecular heterogeneity of MSI-H CRCs. Here, we have reviewed and discussed the molecular and prognostic features of MSI-H CRCs, as well as several putative prognostic or predictive molecular markers, including HSP110 expression, beta2-microglobulin mutations, myosin 1a expression, CDX2/CK20 expression, SMAD4 expression, CIMP status and LINE-1 methylation levels.

Rhabdoid colorectal carcinomas: reports of two cases

Rhabdoid colorectal carcinomas are very rare and only 10 cases have been previously reported. We report two cases of rhabdoid colorectal carcinoma, one arising in the sigmoid colon of a 62-year-old man and another in the rectum of an 83-year-old woman. In both cases, the patients had advanced tumors with lymph node metastases. The tumors mostly showed a diffuse arrangement with rhabdoid features and small glandular regions were combined. Transitional areas from the adenocarcinomas to the rhabdoid tumors were also noted. Adenocarcinoma cells were positive for mixed cytokeratin (CK), CK20 and epithelial membranous antigen (EMA), but focal positive for vimentin. The rhabdoid tumor cells were positive for mixed CK, but focal positive or negative for CK20 and EMA. In addition, they were diffusely positive for vimentin, but negative for desmin. The histological and immunohistologial findings of these two cases suggest that the rhabodid tumor cells originated from dedifferentiated adenocarcinomas.

Loss of the proteins Bak and Bax prevents apoptosis mediated by histone deacetylase inhibitors

Burkitt lymphoma is characterized by deregulation of c-myc, and therapies targeting c-myc are under investigation as treatments. Histone deacetylase inhibitors are known to abrogate c-myc expression, leading us to examine their effect in a series of Burkitt lymphoma cell lines. While treatment with romidepsin, panobinostat, vorinostat, or belinostat for 48 h resulted in complete cell death in the Ramos and ST486 lines, CA46 and DG75 cells were resistant. In parallel studies, CA46 and DG75 cells were also insensitive to 48 h treatment with the Aurora kinase inhibitors (AKIs) MLN8237 (alisertib), VX-680 (tozasertib), or ZM447439. Bax knockdown is known to lead to HDI resistance, and we found that loss of Bax or both Bak and Bax correlated with resistance to both AKIs and HDIs in the Burkitt cell lines. As proof-of-concept to evaluate the contribution of Bax and Bak to HDI-mediated apoptosis, we found that apoptosis was unaffected in HCT-116 colon carcinoma cells lacking Bak, blunted in cells lacking Bax, and nearly completely abrogated in cells lacking both Bak and Bax compared with wild-type cells. To explore potential clinical variations in Bak and Bax expression, a series of samples from 16 patients diagnosed with Burkitt lymphoma was examined. While the majority of samples were positive for both Bak and Bax, some (3/16) expressed low levels of both proteins. We thus conclude that HDI-mediated and AKI-mediated apoptosis requires mitochondrial engagement, and that baseline Bax and Bak expression may serve as biomarkers for patients with Burkitt lymphoma likely to respond to HDI treatment.

Comprehensive genome- and transcriptome-wide analyses of mutations associated with microsatellite instability in Korean gastric cancers

Microsatellite instability (MSI) is a critical mechanism that drives genetic aberrations in cancer. To identify the entire MS mutation, we performed the first comprehensive genome- and transcriptome-wide analyses of mutations associated with MSI in Korean gastric cancer cell lines and primary tissues. We identified 18,377 MS mutations of five or more repeat nucleotides in coding sequences and untranslated regions of genes, and discovered 139 individual genes whose expression was down-regulated in association with UTR MS mutation. In addition, we found that 90.5% of MS mutations with deletions in gene regions occurred in UTRs. This analysis emphasizes the genetic diversity of MSI-H gastric tumors and provides clues to the mechanistic basis of instability in microsatellite unstable gastric cancers.

Era of universal testing of microsatellite instability in colorectal cancer

Colorectal cancer (CRC) incidence and mortality are constantly decreasing, but CRC still remains the third most prevalent cancer and the third most common cause of cancer death in both males and females in the United States. Recent rapid declines in CRC incidence rates have largely been attributed to increases in screening that can detect and remove precancerous polyps, and the decrease in death rates for CRC largely reflects improvements in early detection, treatment and the understanding of molecular/genetic basis of CRC. One of the important molecular/genetic findings is the presence of microsatellite instability (MSI) in CRCs. Many studies have shown the importance of MSI testing in diagnosing Lynch syndrome and predicting prognosis and response to chemotherapeutic agents in CRCs. Increased emphasis has been placed on the importance of MSI testing for all newly diagnosed individuals with CRCs. Both immunohistochemical staining (IHC) and polymerase chain reaction (PCR)-based MSI testing show high sensitivity and specificity in detecting MSI. The current clinical guidelines and histopathology features are indicative of, but not reliable in diagnosing Lynch syndrome and CRCs with MSI. Currently, there are evidences that universal testing for MSI starting with either IHC or PCR-based MSI testing is cost effective, sensitive, specific and is getting widely accepted.

Targeted therapies in colorectal cancer-an integrative view by PPPM

In developed countries, colorectal cancer (CRC) is the third most common malignancy, but it is the second most frequent cause of cancer-related death. Clinicians are still faced with numerous challenges in the treatment of this disease, and future approaches which target the molecular features of the disorder will be critical for success in this disease setting. Genetic analyses of many solid tumours have shown that up to 100 protein-encoding genes are mutated. Within CRC, numerous genetic alterations have been identified in a number of pathways. Therefore, understanding the molecular pathology of CRC may present information on potential routes for treatment and may also provide valuable prognostic information. This will be particularly pertinent for molecularly targeted treatments, such as anti-vascular endothelial growth factor therapies and anti-epidermal growth factor receptor (EGFR) monoclonal antibody therapy. KRAS and BRAF mutations have been shown to predict response to anti-EGFR therapy. As EGFR can also signal via the phosphatidylinositol 3-kinase (PI3K) kinase pathway, there is considerable interest in the potential roles of members of this pathway (such as PI3K and PTEN) in predicting treatment response. Therefore, a combined approach of new techniques that allow identification of these biomarkers alongside interdisciplinary approaches to the treatment of advanced CRC will aid in the treatment decision-making process and may also serve to guide future therapeutic approaches.

Predictive markers for the response to 5-fluorouracil therapy in cancer cells: Constant-field gel electrophoresis as a tool for prediction of response to 5-fluorouracil-based chemotherapy

The prediction of response or severe toxicity and therapy individualisation are extremely important in cancer chemotherapy. There are few tools to predict chemoresponse or toxicity in cancer patients. We investigated the correlation between the induction and repair of DNA double-strand breaks (DSBs) using constant-field gel electrophoresis (CFGE) and evaluating cell cycle progression and the sensitivity of four cancer cell lines to 5-fluorouracil (5FU). Using a sulphorhodamine-B assay, colon carcinoma cells (HCT116) were found to be the most sensitive to 5FU, followed by liver carcinoma cells (HepG2) and breast carcinoma cells (MCF-7). Cervical carcinoma cells (HeLa) were the most resistant. As measured by CFGE, DSB induction, but not residual DSBs, exhibited a significant correlation with the sensitivity of the cell lines to 5FU. Flow cytometric cell cycle analysis revealed that 14% of HCT116 or HepG2 cells and 2% of MCF-7 cells shifted to sub-G1 phase after a 96-h incubation with 5FU. Another 5FU-induced cell cycle change in HCT116, HepG2 and MCF-7 cells was the mild arrest of cells in G1 and/or G2/M phases of the cell cycle. In addition, 5FU treatment resulted in the accumulation of HeLa cells in the S and G2/M phases. Determination of Fas ligand (Fas-L) and caspase 9 as representative markers for the extrinsic and intrinsic pathways of apoptosis, respectively, revealed that 5FU-induced apoptosis in HCT116 and HepG2 results from the expression of Fas-L (extrinsic pathway). Therefore, the induction of DNA DSBs by 5FU, detected using CFGE, and the induction of apoptosis are candidate predictive markers that may distinguish cancer cells which are likely to benefit from 5FU treatment and the measurement of DSBs using CFGE may aid the prediction of clinical outcome.