Evolution of colorectal cancer: change of pace and change of direction

Microbe-based therapies for colorectal cancer: Advantages and limitations

Cancer is one of the leading global causes of death in both men and women. Colorectal cancer (CRC) alone accounts for ∼10 % of total new global cases and poses an over 4% lifetime risk of developing cancer. Recent advancements in the field of biotechnology and microbiology concocted novel microbe-based therapies to treat various cancers, including CRC. Microbes have been explored for human use since centuries, especially for the treatment of various ailments. The utility of microbes in cancer therapeutics is widely explored, and various bacteria, fungi, and viruses are currently in use for the development of cancer therapeutics. The human gut hosts about 100 trillion microbes that release their metabolites in active, inactive, or dead conditions. Microbial secondary metabolites, proteins, immunotoxins, and enzymes are used to target cancer cells to induce cell cycle arrest, apoptosis, and death. Various approaches, such as dietary interventions, the use of prebiotics and probiotics, and fecal microbiota transplantation have been used to modulate the gut microbiota in order to prevent or treat CRC pathogenesis. The present review highlights the role of the gut microbiota in CRC precipitation, the potential mechanisms and use of microorganisms as CRC biomarkers, and strategies to modulate microbiota for the prevention and treatment of CRC.

[Value of combined detection of ITGA4 and SFRP2 gene methylation in stool DNA in diagnosis and prognostic evaluation of colorectal tumors]

OBJECTIVE

To investigate the value of quantitative detection of ITGA4 and SFRP2 gene methylation in stool DNA for the early diagnosis and prognostic evaluation of colorectal tumors.

OBJECTIVE

Real-time PCR was used for quantitative assessment of ITGA4 and SFRP2 gene methylation levels in stool samples of 85 patients with colorectal cancer, 65 patients with colorectal adenoma and 40 healthy subjects.

OBJECTIVE

The 3 groups were comparable for age and gender composition. Methylated ITGA4 and SFRP2 promoters were detected in 48.2% and 62.4% of patients with colorectal cancer, respectively, with a combined positivity of 81.2%. ITGA4 and SFRP2 promoter methylation was detected in 23.1% and 43.1% of patients with colorectal adenoma, respectively, with a combined positivity of 69.2%. The positivity rates of ITGA4 and SFRP2 methylation were significantly higher in patients with colorectal cancer than in those with colorectal adenoma (P < 0.001; P= 0.001) and healthy subjects (P < 0.001; P < 0.001). In colorectal cancer group, ITGA4 and SFRP2 promoter methylation levels were correlated with postoperative tumor recurrence in colorectal cancer group, and the relapse-free survival rate was significantly lower in positive patients for ITGA4 and SFRP2 promoter methylation than in the negative patients (P=0.0002; P=0.007). Multivariate analysis with the COX proportional hazard regression model showed that methylation of ITGA4 and SFRP2 gene promoters (P=0.01) and the degree of tumor differentiation (P=0.03) were associated with the recurrence of colorectal cancer, and were independent risk factors for the recurrence of colorectal cancer.

OBJECTIVE

Combined detection of ITGA4 and SFRP2 gene methylation levels in stool DNA can improve the early diagnosis rate of colorectal tumor. ITGA4 and SFRP2 promoter methylation and the degree of tumor differentiation are independent risk factors for colorectal cancer recurrence.

Cancer as a form of life: Musings of the cancer and evolution symposium

Advanced cancer is one of the major problems in oncology as currently, despite the recent technological and scientific advancements, the mortality of metastatic disease remains very high at 70-90%. The field of oncology is in urgent need of novel ideas in order to improve quality of life and prognostic of cancer patients. The Cancer and Evolution Symposium organized online October 14-16, 2020 brought together a group of specialists from different fields that presented innovative strategies for better understanding, preventing, diagnosing, and treating cancer. Today still, the main reasons behind the high incidence and mortality of advanced cancer are, on one hand, the paucity of funding and effort directed to cancer prevention and early detection, and, on the other hand, the lack of understanding of the cancer process itself. I argue that besides being a disease, cancer is also a form of life, and, this frame of reference may provide a fresh look on this complex process. Here, I provide a different angle to several contemporary cancer theories discussing them from the perspective of "cancer-forms of life" (i.e. bionts) point of view. The perspectives and the several "bionts" introduced here, by no means exclusive or comprehensive, are just a shorthand that will hopefully encourage the readers, to further explore the contemporary oncology theoretical landscape.

The "unnatural" history of colorectal cancer in Lynch syndrome: Lessons from colonoscopy surveillance

Individuals with Lynch syndrome (LS), one of the most common inherited cancer syndromes, are at increased risk of developing malignancies, in particular colorectal cancer (CRC). Regular colonoscopy with polypectomy is recommended to reduce CRC risk in LS individuals. However, recent independent studies demonstrated that a substantial proportion of LS individuals develop CRC despite regular colonoscopy. The reasons for this surprising observation confirmed by large prospective studies are a matter of debate. In this review, we collect existing evidence from clinical, epidemiological and molecular studies and interpret them with regard to the origins and progression of LS-associated CRC. Alongside with hypotheses addressing colonoscopy quality and pace of progression from adenoma to cancer, we discuss the role of alternative precursors and immune system in LS-associated CRC. We also identify gaps in current knowledge and make suggestions for future studies aiming at improved CRC prevention for LS individuals.

Clinicopathological and mutational differences between tumors with multiple metastases and single lung metastasis in colorectal cancer

Cancer metastasis, particularly multiple metastatic cancer, is a significant event that affects patient prognosis. However, single metastasis can be treated by partial resection, although the clinicopathological and molecular profile of single lung metastasis has not been thoroughly elucidated. The present study examined tumor heterogeneity by comparing the mutation status between primary colorectal cancer (CRC) and corresponding metastatic lesions to identify prognostic factors associated with single lung metastasis and multiple metastases. The present study enrolled 31 cases of CRC; 20 cases with multiple metastases and 11 cases with single lung metastasis. Clinicopathologically, all cases with multiple metastases were tubular adenocarcinoma, and 3/11 cases with single metastasis were mucinous adenocarcinoma originating from the left side, the remaining 8 cases were tubular adenocarcinoma from the left side. CRC cases with multiple metastases exhibited more frequent vascular invasion, but not lymphatic invasion, than those with single lung metastasis. Furthermore, CRC with multiple metastases was associated with strong tumor budding (P=0.04). Patients with CRC with multiple metastases had lower recurrence-free survival rates compared with those with single lung metastasis (P=0.02). However, there was no significant difference between these two groups in terms of overall survival rates. A next-generation sequencing cancer hotspot panel was used to analyze a heterochronous multiple metastases case, including brain metastasis. Sanger sequencing, immunohistochemistry and microsatellite instability were examined for all 31 cases to reveal the molecular features. KRAS and TP53 mutation signatures were largely preserved throughout the metastatic events. TP53/APC mutations and overexpression of p53 appeared to be associated with the presence of lymphovascular invasion and strong tumor budding, respectively, although these differences were not statistically significant. Early relapses in patients with CRC could be a sign for eventual multiple metastases, although these may not affect the overall survival of patients with CRC. Considerable mutational changes were seemingly rare during metastatic events in patients with CRC.

Fast and efficient microfluidic cell filter for isolation of circulating tumor cells from unprocessed whole blood of colorectal cancer patients

Liquid biopsy offers unique opportunities for low invasive diagnosis, real-time patient monitoring and treatment selection. The phenotypic and molecular profile of circulating tumor cells (CTCs) can provide key information about the biology of tumor cells, contributing to personalized therapy. CTC isolation is still challenging, mainly due to their heterogeneity and rarity. To overcome this limitation, a microfluidic chip for label-free isolation of CTCs from peripheral blood was developed. This device, the CROSS chip, captures CTCs based on their size and deformability with an efficiency of 70%. Using 2 chips, 7.5 ml of whole blood are processed in 47 minutes with high purity, as compared to similar technologies and assessed by in situ immunofluorescence. The CROSS chip performance was compared to the CellSearch system in a set of metastatic colorectal cancer patients, resulting in higher capture of DAPI+/CK+/CD45- CTCs in all individuals tested. Importantly, CTC enumeration by CROSS chip enabled stratification of patients with different prognosis. Lastly, cells isolated in the CROSS chip were lysed and further subjected to molecular characterization by droplet digital PCR, which revealed a mutation in the APC gene for most patient samples analyzed, confirming their colorectal origin and the versatility of the technology for downstream applications.

Expression of the Hepatocyte Growth Factor and C-Met in Colon Cancer: Correlation with Clinicopathological Features and Overall Survival

Aim and Background

The hepatocyte growth factor (HGF)/c-Met signaling system has been implicated in the development and progression of colon cancer, but the relationship between the expression of HGF or c-MET and clinicopathologic features remains controversial. In the study, we analyzed the expression of HGF and c-Met in colon cancer and assessed the influence of the expression of this growth factor and its receptor on clinical and histological parameters and patient survival.

Methods and Study Design

We investigated the mRNA expression of HGF and c-Met with real-time PCR in 90 unselected colon carcinomas and the corresponding normal mucosa. Furthermore, HGF and c-Met protein expression was investigated with immunohistochemistry in all the samples.

Results

The mRNA and protein expression levels of HGF and c-Met were significantly higher in colon cancer than in matched normal mucosa. The protein level in most of the cases investigated was correlated with the mRNA level. Overexpression of HGF and c-Met, at both protein and mRNA levels, was correlated with depth of invasion, lymph node metastases and overall AJCC stage. According to univariate analysis, the mean survival time was shorter in the HGF-positive and c-Met-positive groups. Multivariate Cox analysis showed that high M stage and the expression of c-Met independently had a negative impact on overall survival.

Conclusions

The HGF/c-Met signaling pathway may be involved in the pathogenesis and progression of colon cancer. C-Met overexpression can be used as a useful parameter to evaluate the prognosis of colon cancer.

Functional consequence of the p53 codon 72 polymorphism in colorectal cancer

Background

The codon 72 polymorphism in p53 has been implicated in colorectal cancer (CRC) risk, prognosis and CRC health disparities. We examined the functional consequence of this polymorphism in CRC.

Experimental Design

Plasmids (pCMV6) that express different phenotypes of p53 [p53 wild type (wt) at codon 72 (R72^wt), R72^wt with mutation at codon 273 cysteine (R72^273Cys), p53 mutation at codon 72 (P72^wt) and P72^wt with mutation at codon 273 (P72^273Cys)] were constructed. The CRC cell line Caco2, which does not express p53 for in vitro studies, was used as host. CRC xenografts were established in severe combined immunodeficient (SCID) mice using established cell lines. CRC surgical specimens, corresponding normal colon, and tumor xenografts were sequenced for codon 72 polymorphism of p53. Proteins signaling mechanisms were evaluated to assess the functional consequence of P72 phenotype of p53.

Results

This study demonstrated a significantly increased survival of cells expressing P72^wt, mutant phenotype, versus R72^wt phenotype. WB analyses revealed that P72^wt induced activation of p38 and RAF/MEK/ extracellular signal-regulated kinase (ERK) MAP kinases. Activation of CREB was found to be higher in tumors that exhibit P72 phenotype. Metastatic lesions of CRC expressed more phospho-CREB than non-metastatic lesions. The expression of P72^wt promoted CRC metastasis.

Conclusions

P72 contributes to the aggressiveness of CRC. Because P72 is over-expressed in CRC, specifically in African-American patients, this suggests a role for P72 in cancer health disparities. This work was supported by NIH/NCI Workforce Diversity Grant R21-CA171251 & U54CA118948.

MicroRNAs are important regulators of drug resistance in colorectal cancer

Despite of continuous development of cancer treatment over the past decades, drug resistance is still one of the major hurdles of effective therapy for advanced colorectal cancer (CRC) worldwide and the understanding of its underlying mechanisms remains limited. Data which have emerged suggests that many microRNAs (miRNAs) may contribute to drug resistance in CRC. Major findings on miRNA functions in drug resistance of CRC are systemically reviewed here, with the goal of providing new updates to broaden our comprehension of its mechanisms and evidence to utilize miRNAs as potential therapeutic targets for CRC treatment.

Clinicopathological, prognostic and predictive value of CD166 expression in colorectal cancer: a meta-analysis

CD166 has been identified as an important cancer stem cell (CSC) marker in colorectal cancer (CRC). The purpose of our study was to investigate the relationship between CD166 expression and clinical features and to examine the role of CD166 expression on the survival of patients with CRC. A total of 15 studies with 3,332 cases were identified in this meta-analysis. The pooled OR indicated that CD166 expression was significantly higher in CRC than in colonic adenomas or normal colonic mucosa (OR = 3.48, P = 0.002 and OR = 55.13, P = 0.017, respectively). CD166 expression was found to be negatively correlated with vascular invasion (OR = 0.75, P = 0.017), but it was not associated with gender, tumor location, lymph node status, distant metastasis, clinical stage, T classification or tumor differentiation. Meanwhile, CD166 expression was not associated with the prognosis of overall survival (OS) (HR = 1.20, 95% CI = 0.45-3.22, P = 0.72) in multivariate regression analysis. One study reported that CD166 expression may be a predictor of survival in stage II CRC patients using multivariate logistic regression analysis (OS: OR = 9.97, P = 0.035; disease-specific survival: OR = 29.02, P = 0.011). Our findings suggest that CD166 expression may be correlated with CRC carcinogenesis and a decreased risk of vascular invasion, and it may become a predictive biomarker of survival for stage II CRC patients, but additional studies with large sample sizes are essential to validate the prognostic and predictive values of CD166 expression.

Clinicopathological characteristics of serrated polyps as precursors to colorectal cancer: Current status and management

Serrated polyps have long been thought to lack malignant potential in the human colorectum. However, identification of the serrated pathway to colorectal cancer based on molecular biology has improved our understanding of the pathogenesis of colorectal cancers. Accordingly, serrated polyps such as traditional serrated adenoma and sessile serrated adenoma/polyps (SSA/P) are now considered to be precursor lesions of the serrated pathway. Recently, serrated polyps were classified into three subtypes, consisting of hyperplastic polyp, SSA/P, and traditional serrated adenoma, according to the World Health Organization classification. It has been suggested that SSA/P in the proximal colon are a precursor lesion of pathogenesis of colorectal cancer and are characterized by BRAF mutation and a CpG island methylator phenotype with or without microsatellite instability. However, SSA/P is more challenging to detect by colonoscopy and is likely to account for some interval cancers, particularly in the proximal colon because it presents flat or sessile, isochroous appearance, and occasionally has a mucous cap. Furthermore, the possibility has been raised that pathologists misclassify SSA/P as hyperplastic polyp. It is important for gastroenterologists to recognize the endoscopic features of serrated polyps to facilitate their detection and removal and also to establish postpolypectomy surveillance guidelines. In this review, we discuss the recent classification of serrated polyps; the molecular characteristics of the serrated pathway; appropriate diagnostic methods using endoscopy, including a new image-enhanced endoscopic technique; and management of these lesions.

Methylation of SFRP2 gene as a promising noninvasive biomarker using feces in colorectal cancer diagnosis: a systematic meta-analysis

Methylation of secreted frizzled-related protein genes (SFRP) associated with the Wnt signaling pathway has previously been reported. However, the diagnostic role of SFRP methylation in colorectal cancer (CRC) remains unclear. A systematic search was performed to identify eligible articles for analysis. The pooled OR showed that SFRP1, SFRP2, SFRP4 and SFRP5 methylation was significantly higher in CRC and benign mucosal lesions than in normal colonic mucosa. When CRC was compared to benign mucosal lesions, SFRP1 and SFRP2 methylation had a significantly higher OR, but methylated SFRP4 and SFRP5 had a similar OR. Moreover, the pooled sensitivity, specificity and AUC (area under the curve) of methylated SFRP2 in feces of patients with CRC vs. healthy subjects was 0.71, 0.94 and 0.94, respectively. Therefore, methylation of SFRP1 and SFRP2 may be significantly correlated with CRC. However, in a study with small sample size, methylated SFRP4 and SFRP5 were not shown to be closely associated with CRC. Additionally, detection of SFRP2 methylation in feces presents a potential noninvasive biomarker for CRC diagnosis.

Expression of FOXP1 and Colorectal Cancer Prognosis

BACKGROUND

Forkhead box gene P1 (FOXP1) has proven to be a valuable prognostic biomarker in lymphomas, but little is known about this gene in colorectal cancer (CRC).

OBJECTIVES

To investigate the expression of FOXP1 in CRC and its potential associations with outcome in CRC.

METHODS

We studied the expression pattern of FOXP1 retrospectively via immunohistochemistry in a series of 165 - CRC cases. Fluorescent in situ hybridization and RNA sequencing on FOXP1 knockdown cell lines were performed to investigate the mechanism of action and target genes of FOXP1.

RESULTS

Complete loss of nuclear FOXP1 expression was observed in 11.5% of the subjects. A total of 70.9% of subjects showed a heterogeneous FOXP1 expression pattern, and 17.6% of them had high FOXP1 expression. Impaired expression of FOXP1 was significantly correlated with reduced survival rates by multivariate analysis (P = .004). We found no chromosomal aberrations involving FOXP1 in individuals with FOXP1 negativity via immunohistochemical testing. RNA sequencing revealed that genes involved in inflammation and cell proliferation were differentially expressed after FOXP1 knockdown.

CONCLUSIONS

In our case series, loss of FOXP1 was associated with reduced survival rates in CRC tissue. Also, FOXP1 affects proliferation and inflammatory reaction in colorectal neoplasia.

Tumour budding in colorectal cancer: what do we know and what can we do?

Budding is a process during which individual or small clusters of up to five tumour cells detach from the main tumour mass and invade into the surrounding stroma. In colorectal cancer, this feature is observed in 20-40% of cases and is associated with lymphovascular invasion, lymph node and distant metastases, and poor prognosis. A variety of scoring systems for budding have been proposed but so far a gold standard is lacking, hampering implementation of a budding score in guidelines for pathological examination of colorectal cancer. Furthermore, little is known about the mechanisms which cause tumour cells to detach from the main tumour mass and obtain increased invasive potential. In this review, we present an overview of tumour budding including its definition, scoring systems, prognostic relevance and biological mechanisms involved.

Molecular and pathogenetic aspects of tumor budding in colorectal cancer

In recent years, tumor budding in colorectal cancer has gained much attention as an indicator of lymph node metastasis, distant metastatic disease, local recurrence, worse overall and disease-free survival, and as an independent prognostic factor. Tumor buds, defined as the presence of single tumor cells or small clusters of up to five tumor cells at the peritumoral invasive front (peritumoral buds) or within the main tumor body (intratumoral buds), are thought to represent the morphological correlate of cancer cells having undergone epithelial–mesenchymal transition (EMT), an important mechanism for the progression of epithelial cancers. In contrast to their undisputed prognostic power and potential to influence clinical management, our current understanding of the biological background of tumor buds is less established. Most studies examining tumor buds have attempted to recapitulate findings of mechanistic EMT studies using immunohistochemical markers. The aim of this review is to provide a comprehensive summary of studies examining protein expression profiles of tumor buds and to illustrate the molecular pathways and crosstalk involved in their formation and maintenance.

Genetic pathways, prevention, and treatment of sporadic colorectal cancer

Epithelial cancer of the colon and rectum, also known as colorectal cancer (CRC), results from a progressive accumulation of genetic and epigenetic alterations that lead to uncontrolled growth of colonocytes, the cells lining the colon and rectum. CRC is the second leading cause of cancer-related deaths and the third most common cancer in men and in women in the U.S. Of all the patients diagnosed with CRC every year, it is estimated that the vast majority of CRCs are non-hereditary “sporadic cancers” with no apparent evidence of an inherited component. Sporadic CRC results from the cumulative effects of multiple genetic and epigenetic alterations caused by somatic mutations, which may themselves be the indirect result of several environmental factors. This review examines our current understanding of the major genetic alterations leading to colon cancer, options for prevention and early detection of CRC, and the currently available treatment approaches that may target these different genetic alterations.

Colorectal polyps and polyposis syndromes

A polyp is defined as any mass protruding into the lumen of a hollow viscus. Colorectal polyps may be classified by their macroscopic appearance as sessile (flat, arising directly from the mucosal layer) or pedunculated (extending from the mucosa through a fibrovascular stalk). Colorectal polyps may also be histologically classified as neoplastic or as non-neoplastic (hyperplastic, hamartomatous, or inflammatory). The neoplastic polyps are of primary importance because they harbor a malignant potential, which represents a stage in the development of colorectal cancer. For this reason, it is essential to identify these polyps at a sufficiently early stage, when a simple outpatient procedure to remove them can interrupt the development of colorectal cancer and prevent disease and death. When invasive carcinoma arises in a polyp, careful consideration must be given to ensuring the adequacy of treatment. Although most neoplastic polyps do not evolve into cancer, it is well accepted that the majority of colorectal carcinomas evolve from adenomatous polyps; the sequence of events leading to this transformation is referred to as the adenoma-to-carcinoma sequence.

The presence of a systemic process that promotes the development of multiple gastro-intestinal polyps is termed ‘polyposis’. Hereditary gastro-intestinal polyposis syndromes account for approximately 1% of all cases of colorectal cancer and are associated with a broad spectrum of extra-colonic tumors. Early detection and accurate classification of these syndromes are essential, in order to initiate a surveillance program for the early detection of cancer. Several polyposis syndromes have been described, each having its own genetic basis and characteristic polyp distribution, clinical presentation, and malignancy risk.

Diagnostic modalities and treatment options for neoplastic polyps—as well as the most prevalent polyposis syndromes—are reviewed below.

The role of insulin-like growth factor 1 and its receptor in the formation and development of colorectal carcinoma

OBJECTIVE

To investigate the role of insulin-like growth factor (IGF)-1 and its receptor (IGF1R) in the formation and development of colorectal carcinoma.

METHODS

Colorectal tissue and matching serum samples were collected from patients with adenomatous polyps or carcinoma and healthy control subjects. IGF1R mRNA levels were determined via quantitative real-time reverse transcription-polymerase chain reaction. Serum IGF1 was quantified using enzyme-linked immunosorbent assay.

RESULTS

Serum IGF1 concentrations and mucosal IGF1R mRNA levels were significantly higher in patients with adenomatous polyps (n = 24) or carcinoma (n = 13) compared with healthy control subjects (n = 13). There was a significant positive correlation between serum IGF1 and mucosal IGF1R mRNA in patients with adenomatous polyps.

CONCLUSIONS

High circulating IGF1 concentrations and mucosal IGF1R expression may play important roles in both the formation and development of colorectal carcinoma. IGF1 and its receptor may be activated before carcinogenesis, and may promote the growth and malignant transformation of adenomatous polyps. IGF1 and IGF1R may be useful biomarkers for evaluating the stage and risk of carcinogenesis.

A population-based study of hereditary non-polyposis colorectal cancer: evidence of pathologic and genetic heterogeneity

Hereditary non-polyposis colorectal cancer (HNPCC) may be the result of Lynch syndrome (LS) caused by mutations in mismatch repair (MMR) genes, a syndrome of unknown etiology called familial colorectal cancer type-X (FCCTX), or familial serrated neoplasia associated with the colorectal cancer (CRC) somatic BRAF mutation. To determine the cause of HNPCC in the founder population of the island of Newfoundland, we studied 37 families with LS and 29 families without LS who fulfilled the Amsterdam I criteria. In non-LS, four index CRCs were BRAF mutation positive, one of which was microsatellite instable. Geographic clustering of LS families caused by three different founder mutations in MSH2 was observed. Nine unique MMR mutations in four MMR genes were identified in single families distributed in different geographic isolates. The geographic distribution of non-LS was similar to LS. The coefficient of relatedness using genotype data was significantly higher for non-LS than for all CRC. Extensive genealogic investigation failed to connect non-LS families and in some clusters pathologic CRC heterogeneity was observed. We conclude that non-LS HNPCC may be a heterogeneous disorder with different pathogenic pathways, and that the geographic distribution is consistent with multiple different mutations in unknown CRC susceptibility gene(s).

Serrated polyps of the colon: how reproducible is their classification?

For several years, the lack of consensus on definition, nomenclature, natural history, and biology of serrated polyps (SPs) of the colon has created considerable confusion among pathologists. According to the latest WHO classification, the family of SPs comprises hyperplastic polyps (HPs), sessile serrated adenomas/polyps (SSA/Ps), and traditional serrated adenomas (TSAs). The term SSA/P with dysplasia has replaced the category of mixed hyperplastic/adenomatous polyps (MPs). The present study aimed to evaluate the reproducibility of the diagnosis of SPs based on currently available diagnostic criteria and interactive consensus development. In an initial round, H&E slides of 70 cases of SPs were circulated among participating pathologists across Europe. This round was followed by a consensus discussion on diagnostic criteria. A second round was performed on the same 70 cases using the revised criteria and definitions according to the recent WHO classification. Data were evaluated for inter-observer agreement using Kappa statistics. In the initial round, for the total of 70 cases, a fair overall kappa value of 0.318 was reached, while in the second round overall kappa value improved to moderate (kappa = 0.557; p < 0.001). Overall kappa values for each diagnostic category also significantly improved in the final round, reaching 0.977 for HP, 0.912 for SSA/P, and 0.845 for TSA (p < 0.001). The diagnostic reproducibility of SPs improves when strictly defined, standardized diagnostic criteria adopted by consensus are applied.

A review of spatial computational models for multi-cellular systems, with regard to intestinal crypts and colorectal cancer development

Colon rectal cancers (CRC) are the result of sequences of mutations which lead the intestinal tissue to develop in a carcinoma following a "progression" of observable phenotypes. The actual modeling and simulation of the key biological structures involved in this process is of interest to biologists and physicians and, at the same time, it poses significant challenges from the mathematics and computer science viewpoints. In this report we give an overview of some mathematical models for cell sorting (a basic phenomenon that underlies several dynamical processes in an organism), intestinal crypt dynamics and related problems and open questions. In particular, major attention is devoted to the survey of so-called in-lattice (or grid) models and off-lattice (off-grid) models. The current work is the groundwork for future research on semi-automated hypotheses formation and testing about the behavior of the various actors taking part in the adenoma-carcinoma progression, from regulatory processes to cell-cell signaling pathways.

A review of spatial computational models for multi-cellular systems, with regard to intestinal crypts and colorectal cancer development

Colon rectal cancers (CRC) are the result of sequences of mutations which lead the intestinal tissue to develop in a carcinoma following a "progression" of observable phenotypes. The actual modeling and simulation of the key biological structures involved in this process is of interest to biologists and physicians and, at the same time, it poses significant challenges from the mathematics and computer science viewpoints. In this report we give an overview of some mathematical models for cell sorting (a basic phenomenon that underlies several dynamical processes in an organism), intestinal crypt dynamics and related problems and open questions. In particular, major attention is devoted to the survey of so-called in-lattice (or grid) models and off-lattice (off-grid) models. The current work is the groundwork for future research on semi-automated hypotheses formation and testing about the behavior of the various actors taking part in the adenoma-carcinoma progression, from regulatory processes to cell-cell signaling pathways.

Prognostic significance and gene expression profiles of p53 mutations in microsatellite-stable stage III colorectal adenocarcinomas

Although the prognostic value of p53 abnormalities in Stage III microsatellite stable (MSS) colorectal cancers (CRCs) is known, the gene expression profiles specific to the p53 status in the MSS background are not known. Therefore, the current investigation has focused on identification and validation of the gene expression profiles associated with p53 mutant phenotypes in MSS Stage III CRCs. Genomic DNA extracted from 135 formalin-fixed paraffin-embedded tissues, was analyzed for microsatellite instability (MSI) and p53 mutations. Further, mRNA samples extracted from five p53-mutant and five p53-wild-type MSS-CRC snap-frozen tissues were profiled for differential gene expression by Affymetrix Human Genome U133 Plus 2.0 arrays. Differentially expressed genes were further validated by the high-throughput quantitative nuclease protection assay (qNPA), and confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) and by immunohistochemistry (IHC). Survival rates were estimated by Kaplan-Meier and Cox regression analyses. A higher incidence of p53 mutations was found in MSS (58%) than in MSI (30%) phenotypes. Both univariate (log-rank, P = 0.025) and multivariate (hazard ratio, 2.52; 95% confidence interval, 1.25-5.08) analyses have demonstrated that patients with MSS-p53 mutant phenotypes had poor CRC-specific survival when compared to MSS-p53 wild-type phenotypes. Gene expression analyses identified 84 differentially expressed genes. Of 49 down-regulated genes, LPAR6, PDLIM3, and PLAT, and, of 35 up-regulated genes, TRIM29, FUT3, IQGAP3, and SLC6A8 were confirmed by qNPA, qRT-PCR, and IHC platforms. p53 mutations are associated with poor survival of patients with Stage III MSS CRCs and p53-mutant and wild-type phenotypes have distinct gene expression profiles that might be helpful in identifying aggressive subsets.

Expression of IGF-1R in Colorectal Polyps and its Role in Colorectal Carcinogenesis

Insulin-like Growth Factor Receptor 1 (IGF-1R) may play a role in the neoplastic progression of colorectal cancer because it is related to both cellular proliferation and differentiation. The aim of this study was to further elucidate the role of IGF-1R in colorectal carcinogenesis by evaluating IGF-1R expression in different types of precancerous colorectal polyps and comparing its expression to normal mucosa and colorectal carcinoma. A total of 47 colorectal polyps and their respective adjacent normal mucosa were collected from 32 patients. In addition, 20 colorectal adenocarcinoma tissues were obtained from patients undergoing colorectal resection, and 12 normal non-malignant colorectal mucosal tissues collected from outpatients served as the control group. The pit patterns of polyps were classified by the Kudo classification scheme through magnifying chromoendoscopy. Immunohistochemistry and quantitative real-time RT-PCR were utilized for expression analysis of IGF-1R in colorectal mucosa, polyps, and adenocarcinoma tissue. The results of immunohistochemistry showed no significant differences in IGF-1R expression in inflammatory polyps compared with their surrounding normal mucosa by the Mann-Whitney U test (p = 0.251); however, tubular adenoma and villous adenoma tissues exhibited significantly higher levels of IGF-1R expression (p = 0.000). The results of real-time RT-PCR showed that IGF-1R was transcribed at a high level in colorectal adenomatous polyps and adenocarcinoma compared with their respective paired normal mucosa. Spearman's rank correlation two-variable analysis was used to demonstrate a significant correlation between the expression of IGF-1R and neoplastic progression from normal mucosa to adenomatous polyps and finally to colorectal cancer (r = 0.574, p = 0.000). This study suggests that the expression of IGF-1R correlates with the degree of carcinogenesis. In addition, these results demonstrated that there is a significant correlation between the level of IGF-1R expression and pit patterns of polyps (r = 0.432, p = 0.002). Thus, IGF-1R might be a factor in the morphological change of colorectal mucosal crypts, and it may play an important role in the growth and malignant transformation of precancerous polyps. These results suggest that IGF-1R can be considered a biomarker for the stage and risk of carcinogenesis during neoplastic initiation and progression along the colorectal normal mucosa-polyp-cancer sequence. Inhibitors of IGF-1R are not only a promising targeted anticancer strategy, but also a possible option for the chemoprevention of colorectal cancer.

The detection of premalignant colon polyps during colonoscopy is stable throughout the workday

BACKGROUND

Recent studies have shown that colonoscopic polyp detection decreases as the workday progresses. This may reflect time-dependent factors such as colonoscopist fatigue and decreased colon cleanliness, which can be addressed through adaptations in colonoscopy practice.

OBJECTIVE

To test for time-of-day differences in adenomatous polyp (AP) and sessile serrated polyp (SSP) detection in a practice that uses split-dose bowel preparation and moderated daily colonoscopist procedure loads.

DESIGN

Retrospective chart review.

SETTING

Community-based, group gastroenterology practice.

PATIENTS

This study involved 2439 patients undergoing surveillance or screening colonoscopy.

INTERVENTION

Colonoscopy.

MAIN OUTCOME MEASUREMENTS

Detection rate of all premalignant polyps (PMPs), and of APs and SSPs, individually.

RESULTS

A total of 1183 PMPs were identified in 1486 eligible patients (mean PMP/colonoscopy = 0.80; PMP detection rate = 47%). In univariate and multivariate analyses, PMP detection as well as detection of APs or SSPs individually did not vary significantly in relation to the hour of the day. In a binary comparison of morning (am) versus afternoon (pm) procedures, the total polyp detection rate was 67% and 66%, respectively. For PMPs, APs, SSPs, and hyperplastic polyps (HPs), the am and pm detection rates were 46% and 47%, 41% and 44%, 8% and 8%, and 27% and 24%, respectively. Bowel preparation quality was independent of time of day and was rated excellent or good in 86% to 87% of cases.

LIMITATIONS

Retrospective, nonrandomized study.

CONCLUSION

Stable PMP, AP, SSP, and HP detection rates throughout the workday occur under certain practice conditions, including the use of split-dose bowel preparation and/or moderated daily colonoscopist procedure loads.

Prognostic value of colorectal cancer biomarkers

Despite the large amount of data in cancer biology and many studies into the likely survival of colorectal cancer (CRC) patients, knowledge regarding the issue of CRC prognostic biomarkers remains poor. The Tumor-Node-Metastasis (TNM) staging system continues to be the most powerful and reliable predictor of the clinical outcome of CRC patients. The exponential increase of knowledge in the field of molecular genetics has lead to the identification of specific alterations involved in the malignant progression. Many of these genetic alterations were proposed as biomarkers which could be used in clinical practice to estimate CRC prognosis. Recently there has been an explosive increase in the number of putative biomarkers able to predict the response to specific adjuvant treatment. In this review we explore and summarize data concerning prognostic and predictive biomarkers and we attempt to shed light on recent research that could lead to the emergence of new biomarkers in CRC.

DNA methylation patterns in bladder cancer and washing cell sediments: a perspective for tumor recurrence detection

Background

Epigenetic alterations are a hallmark of human cancer. In this study, we aimed to investigate whether aberrant DNA methylation of cancer-associated genes is related to urinary bladder cancer recurrence.

Methods

A set of 4 genes, including CDH1 (E-cadherin), SFN (stratifin), RARB (retinoic acid receptor, beta) and RASSF1A (Ras association (RalGDS/AF-6) domain family 1), had their methylation patterns evaluated by MSP (Methylation-Specific Polymerase Chain Reaction) analysis in 49 fresh urinary bladder carcinoma tissues (including 14 cases paired with adjacent normal bladder epithelium, 3 squamous cell carcinomas and 2 adenocarcinomas) and 24 cell sediment samples from bladder washings of patients classified as cancer-free by cytological analysis (control group). A third set of samples included 39 archived tumor fragments and 23 matched washouts from 20 urinary bladder cancer patients in post-surgical monitoring. After genomic DNA isolation and sodium bisulfite modification, methylation patterns were determined and correlated with standard clinic-histopathological parameters.

Results

CDH1 and SFN genes were methylated at high frequencies in bladder cancer as well as in paired normal adjacent tissue and exfoliated cells from cancer-free patients. Although no statistically significant differences were found between RARB and RASSF1A methylation and the clinical and histopathological parameters in bladder cancer, a sensitivity of 95% and a specificity of 71% were observed for RARB methylation (Fisher's Exact test (p < 0.0001; OR = 48.89) and, 58% and 17% (p < 0.05; OR = 0.29) for RASSF1A gene, respectively, in relation to the control group.

Conclusion

Indistinct DNA hypermethylation of CDH1 and SFN genes between tumoral and normal urinary bladder samples suggests that these epigenetic features are not suitable biomarkers for urinary bladder cancer. However, RARB and RASSF1A gene methylation appears to be an initial event in urinary bladder carcinogenesis and should be considered as defining a panel of differentially methylated genes in this neoplasia in order to maximize the diagnostic coverage of epigenetic markers, especially in studies aiming at early recurrence detection.

DNA methylation patterns of the CDH1, RARB, and SFN genes in choroid plexus tumors

Genetic and epigenetic alterations in choroid plexus tumors, a rare neuroepithelial neoplasm most frequently detected in children, are poorly characterized. Epigenetic silencing associated with aberrant CpG island methylation is one mechanism leading to the loss of tumor suppressor functions in cancer cells. Using methylation-specific polymerase chain reaction, the methylation patterns of the genes CDH1 (E-cadherin), RARB (retinoic acid receptor, beta), and SFN (stratifin; 14-3-3sigma) were retrospectively investigated in eight choroid plexus tumors (five papillomas, two atypical papillomas, and one carcinoma), as well as in two normal cortexes obtained after autopsy from male individuals aged 6 months and 64 years. Among the six pediatric tumors, the mean age at diagnosis was 1.8 years old (range, 0.2-6) and the two adult tumors were detected in a 66-year-old man and a 45-year-old woman. A high frequency of hypermethylation was detected in CDH1 and SFN genes in tumoral and normal cortex tissues. Tumor-specific RARB hypermethylation was observed in four papillomas. Further studies are required to evaluate the role of aberrant methylation in choroid plexus tumor progression.

Molecular heterogeneity of colorectal cancer: Implications for cancer control

Colorectal cancer (CRC) is a multi-pathway disease. A molecular approach to the classification of CRC utilises: (1) the type of genetic instability, specifically microsatellite instability (MSI) versus stable (MSS), and (2) the presence of DNA methylation or the CpG island methylator phenotype (CIMP). The MSS/CIMP-neg subset evolves through the classical adenoma-carcinoma sequence while the MSI/CIMP-pos and MSS/CIMP-pos subsets evolve through the recently recognised 'serrated pathway'. This review will show that the existence of two or more independent pathways to CRC is relevant to cancer prevention. In particular, new strategies for detecting and managing sessile serrated polyps will need to be developed and evaluated.

Surveillance of patients following surgery with curative intent for colorectal cancer

Surveillance after resection of colorectal cancer with curative intent is an important component of post-operative care. Clinical review, imaging, colonoscopy, and cost to the community are among significant issues to consider in planning a surveillance regime. This review aims to identify the available evidence for the use of surveillance and its individual components. The literature pertaining to follow-up of patients following potentially curative surgery for colorectal cancer was reviewed in order to formulate a summary of the wide range of clinical practice. There is evidence of improved survival of patients undergoing more intense follow-up compared with those having minimal surveillance, with an estimated overall 5-year gain of up to 10%. The efficacy of individual components of follow-up regimes remains unclear, but an overall package of ‘intensive’ follow-up including clinical review, liver imaging, and colonoscopy appears to be of benefit. It is cost-effective and can be specialist or community-based.

Colorectal carcinogenesis: Road maps to cancer

This review explores the chief genetic and epigenetic events that promote pathological progression in colorectal carcinogenesis. This article discusses the molecular and pathological basis for classifying colorectal neoplasia into suppressor, mutator and methylator pathways. These differing mechanisms of genomic instability are associated with specific cancer characteristics, and may provide the opportunity for more effective prevention and surveillance strategies in the future. This is the first review in a series of five topics outlining important and developing aspects of colorectal cancer.

Evidence for the role of aberrant DNA methylation in the pathogenesis of Lynch syndrome adenomas

Colorectal cancer (CRC) forms through a series of histologic steps that are accompanied by mutations and epigenetic alterations, which is called the polyp-cancer sequence. The role of epigenetic alterations, such as aberrant DNA methylation, in the polyp-cancer sequence in sporadic CRC and particularly in hereditary colon cancer is not well understood. Consequently, we assessed the methylation status of CDKN2A/p16, MGMT, MLH1 and p14(ARF) in adenomas arising in the Lynch syndrome, a familial colon cancer syndrome caused by MLH1 and MSH2 mutations, to determine if DNA methylation is a "second hit" mechanism in CRC and to characterize the role of DNA methylation in the polyp phase of the Lynch syndrome. We found MLH1 and p14(ARF) are methylated in 53 and 60% of the Lynch syndrome adenomas and in 4 and 20% of sporadic adenomas, whereas CDKN2A/p16 and MGMT are methylated in 6 and 14% of the Lynch syndrome adenomas versus 50 and 64% of sporadic adenomas. Therefore, the frequency and pattern of gene methylation varies between the Lynch syndrome and sporadic colon adenomas, implying differences in the molecular pathogenesis of the tumors. MLH1 methylation in the Lynch syndrome adenomas suggests gene methylation might have a role in the initiation of these neoplasms.

DNA Image Cytometry Is a Useful Adjunct Tool in the Prediction of Disease Outcome in Patients with Stage II and Stage III Colorectal Cancer

BACKGROUND

We assessed the prognostic value of the nuclear DNA content measured in the primary tumours of 123 patients with stage II or stage III colorectal cancer (CRC).

METHODS

Isolated nuclei from paraffin sections were stained with the Feulgen reaction, and DNA was measured using a computer-assisted image analysis cytometry system. We applied 4 different approaches in the analysis of DNA histograms: the ABCDE approach, histogram range, peak evaluation and DNA cut-off values.

RESULTS

Using the histogram range, the narrow range was rare (3.7%) in patients who died of disease (n = 28) as compared with 16.4% among those alive (n = 74; p = 0.017). Modal peak evaluation was a significant predictor of disease-free survival (DFS; Kaplan-Meier log-rank p = 0.0235). In the range evaluation, the 1st set (low-start gates) was a significant predictor of DFS (log-rank p = 0.0121), where disease recurrence was closely associated with the widest range (1.8->10c; c = haploid DNA content) gates. Recurrence-free survival was 3 times better in narrow-gate histograms than wide-range histograms (p < 0.03). The 1st set also proved to be a significant predictor of disease-specific survival (DSS; log-rank p = 0.0045), which was markedly better (77.8-90.0%) among the patients with the narrow-gate histograms. Grading of the histogram range into 2 categories (with 6.0c as cut-off), was a powerful predictor of both DSS (log-rank p = 0.0092) and 5-year DFS (p = 0.0106) in the whole series, and separately in stage III (but not stage II) disease, with p = 0.0131 and p = 0.0201, respectively.

CONCLUSION

The DNA image cytometry with careful analysis of the histograms may provide valuable prognostic information in CRC, with potential clinical implications in patient management, particularly in predicting the patients at high risk for recurrence who should be considered as candidates for adjuvant therapy.

Colorectal serrated adenocarcinoma

Colorectal cancer (CRC) ranks among the three most common cancers in terms of both cancer incidence and cancer-related deaths in most Western countries. Serrated adenocarcinoma is a recently described, distinct variant of CRC, accounting for about 7.5% of all CRCs and up to 17.5% of most proximal CRCs. It has been postulated that about 10-15% of sporadic CRCs would have their origin in serrated polyps that harbour a significant malignant potential. These lesions include hyperplastic-type aberrant crypt foci, hyperplastic polyps, sessile serrated adenomas, admixed polyps and serrated adenomas, and constitute the so-called 'serrated pathway', which is distinct from both the conventional adenoma-carcinoma pathway and the mutator pathway of hereditary non-polyposis CRC and is characterized by early involvement of oncogenic BRAF mutations, excess CpG island methylation (CIM) and subsequent low- or high-level DNA microsatellite instability (MSI). Methylation of hMLH1 is likely to explain the increased frequency of high-level MSI (16%) and methylation of MGMT is postulated to explain the low-level MSI (29%) in serrated adenocarcinomas. Reproducible histopathological criteria for serrated adenocarcinoma have recently been established and they have been qualified by DNA expression analysis for 7928 genes, showing clustering of serrated adenocarcinomas into a molecular entity apart from conventional adenocarcinoma, and representing with distinct down-regulation of EPHB2, PTCH and up-regulation of HIF1alpha.

Advanced colorectal polyps with the molecular and morphological features of serrated polyps and adenomas: concept of a 'fusion' pathway to colorectal cancer

AIM

To establish and explain the pattern of molecular signatures across colorectal polyps.

METHODS AND RESULTS

Thirty-two sessile serrated adenomas (SSA), 10 mixed polyps (MP), 15 traditional serrated adenomas (SA), 49 hyperplastic polyps (HP) and 84 adenomas were assessed for mutation of KRAS and BRAF and aberrant expression of p53. The findings were correlated with loss of expression of O-6-methylguanine DNA methyltransferase (MGMT). KRAS mutation occurred more frequently (26.5%) than BRAF mutation (4.8%) in adenomas (P < 0.001) and particularly in adenomas with villous architecture (50%). Loss of expression of MGMT correlated with KRAS mutation in small tubular adenomas (P < 0.04). BRAF mutation was frequent in HPs (67%) and SSAs (81%), while KRAS mutation was infrequent (4% and 3%, respectively). Of MPs and SAs, 72% had either BRAF or KRAS mutation. Aberrant expression of p53 was uncommon overall, but occurred more frequently in MPs and SAs (12%) than adenomas (1%) (P < 0.04) and there was concordant loss of expression of MGMT.

CONCLUSIONS

Molecular alterations that are characteristic of the serrated pathway and adenoma-carcinoma sequence can co-occur in a minority of advanced colorectal polyps that then show morphological features of both pathways. These lesions account for only 2% of colorectal polyps, but may be relatively aggressive.

Microsatellite instability in colorectal cancer

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Morphology and microsatellite instability in sporadic serrated and non-serrated colorectal cancer

Colorectal serrated adenocarcinoma originates from serrated adenoma, but definite histological criteria have not yet been established. It presents with frequent DNA microsatellite instability (MSI), but the frequency of low-level (MSI-L) and high-level MSI (MSI-H) and the expression of mismatch-repair (MMR) enzymes in serrated adenocarcinoma are not known. To address these questions, morphological criteria for serrated cancers were established, their validity was tested, and MSI analysis was performed with NIH consensus markers and MMR enzyme immunohistochemistry for hMLH1, hMSH2, and hMSH6 in 35 serrated and 75 non-serrated colorectal carcinomas. Serrated carcinomas frequently showed a serrated, mucinous or trabecular growth pattern; abundant eosinophilic cytoplasm; chromatin condensation; preserved polarity; and the absence of necrosis. With these features, it was possible to distinguish them from non-serrated cancers, with the mean kappa score for five observers being 0.509. MSI analysis was successful in 31 serrated and 73 non-serrated carcinomas. 54.8% of serrated carcinomas were microsatellite-stable (MSS), 29.0% presented with MSI-L, and 16.1% presented with MSI-H, whereas 78.1% of non-serrated carcinomas were MSS, 13.7% were MSI-L, and 8.2% were MSI-H. MSI-L was more common in serrated cancers (p=0.035) and it was associated with patchy immunohistochemical staining (33.3%) of MLH1. MSI-H did not differ between serrated and non-serrated cancers (p=0.14). These results suggest that the biological background of serrated carcinomas differs from sporadic non-serrated colorectal cancer, but is not directly related to MSI.

Clinicopathologic features in colorectal cancer patients with microsatellite instability

The microsatellite instability (MSI) mutational pathway is critical to carcinogenesis in a small but significant proportion of colorectal cancers. While MSI is identified in most cancers in individuals with hereditary non-polyposis colorectal cancer, the majority of MSI tumors are found in individuals with sporadic disease. Colorectal cancers arising as a result of MSI have distinct clinicopathologic features distinguishing them from those with microsatellite stability. MSI colorectal cancers affect a larger percentage of women, are usually localized proximal to the splenic flexure, and have a higher incidence of synchronous and metachronous tumors. They are associated with a mucinous histology, tumor-infiltrating lymphocytes, a Crohn's-like inflammatory response, and a higher grade but lower stage. Overall survival is better in individuals with MSI. The benefit of chemotherapy in MSI colorectal cancers, with and without lymph node metastases, remains unclear.

The immunogenicity of colorectal cancers with high-degree microsatellite instability

BACKGROUND

High-degree microsatellite instability (MSI-H) is a feature of approximately 15% of sporadic colorectal cancers. Patients with MSI-H cancers have been reported to have a better prognosis than those with non-MSI-H cancers. The MSI-H subset is also characterised by a dense infiltrate of intra-epithelial lymphocytes and the hypothesis that the latter represents an efficacious immune response contributing to improved outcome is very attractive.

METHODS

Data for this review were identified by searches of MEDLINE, PubMed, and cross references from relevant articles using the search terms 'microsatellite instability', 'colorectal cancer' and 'immunology', 'immune response' or 'immunogenicity'.

RESULTS

A total of 38 articles were identified by the search criteria and a further 95 articles by cross-referencing. The relevance of the articles to be interviewed was established by hand searching. Out of a total of 133 articles identified, 47 articles were rejected due to lack of relevance. A total of 86 articles were included in the review, pertaining to microsatellite instability in colorectal cancer, and immune mechanisms in colorectal cancer.

CONCLUSION

It is suggested that this distinct group of colorectal cancers may have inherent immunogenic properties and that further elucidation of these may be invaluable to the development of successful immunotherapy.

Targeting epigenetic regulatory mechanisms in cancer chemoprevention

Dysregulation of the epigenome plays a fundamental role in tumour development. Epigenetic events are a major mechanism for inactivating tumour suppressor and DNA repair genes and occur ubiquitously during the early stages of tumour development. Unlike genes inactivated by mutation, genes silenced epigenetically are intact and potentially responsive to reactivation by small molecules. This review discusses the potential for restoring epigenetic balance as a means to prevent cancer.

The risk of metachronous neoplasia in patients with serrated adenoma

Serrated adenomas are the precursors of at least 5.8% of colorectal cancers; otherwise little is known of their clinical significance in comparison with conventional adenomas and hyperplastic polyps. We compared the risk of metachronous lesions in colorectal serrated adenomas, conventional adenomas, and hyperplastic polyps. A consecutive series of patients with colorectal polyps first diagnosed from January 1978 to December 1982 and follow-up specimens to the end of 2000 was reviewed, and 239 polyps fulfilling the selection criteria were chosen as index polyps. The type of polyp seen in follow-up correlated significantly with the type of the initial lesion. Serrated adenomas were estimated to grow faster than conventional adenomas, but the incidence of colorectal cancer did not differ significantly between serrated (2/38 [5%]) and conventional adenomas (2.2%). The results indicate that serrated adenomas are lesions with a significant risk of metachronous serrated adenomas and the development of cancer. We emphasize the need for the proper recognition and management of serrated adenomas.

Aberrantly Methylated CDKN2A, MGMT, and MLH1 in Colon Polyps and in Fecal DNA from Patients with Colorectal Polyps

Colon cancer is the third leading cause of cancer-related death in the United States, affecting ∼147,000 people each year. Most colon cancers arise from benign neoplasms and evolve into adenocarcinomas through a stepwise histologic progression sequence that starts from adenomas or hyperplastic polyps/serrated adenomas. Genetic alterations and, more recently, epigenetic alterations have been associated with specific steps in this polyp-adenocarcinoma sequence and likely drive the histologic progression of colon cancer. Consequently, we have assessed in colon adenomas and hyperplastic polyps the methylation status of MGMT, CDKN2A, and MLH1 to determine the timing and frequency of these events in the polyp-carcinoma progression sequence and subsequently to analyze the potential for these methylated genes to be molecular markers for adenomas and hyperplastic polyps. We have found that methylated MGMT, CDKN2A, and MLH1 occur in 49%, 34%, and 7% of adenomas and in 5%, 10%, and 7% of hyperplastic polyps, respectively, and that they are more common in histologically advanced adenomas. Furthermore, analysis of fecal DNA from persons who have undergone colonoscopic exams revealed methylated CDKN2A, MGMT, and MLH1 in fecal DNA from 31%, 48%, and 0% of individuals with adenomas and from 16%, 27%, and 10% of individuals with no detectable polyps, respectively. These results show that aberrant methylated genes can be detected frequently in sporadic colon polyps and that they can be detected in fecal DNA. Notably, improvements in the specificity and sensitivity of the fecal DNA-based assays will be needed to make them clinically useful diagnostic tests for polyps.

Prognostic implications of hMLH1 and p53 immunohistochemical status in right-sided colon cancer

PURPOSE

Extensive research into the molecular biology of colorectal cancer has identified a plethora of molecular markers reputed to provide independent prognostic information. p53 mutational status has been associated with both improved and reduced survival; however, tumors expressing a particular phenotype associated with defective mismatch repair consistently do better. This study was designed to examine site-specific survival implications of p53 and mismatch repair status.

METHODS

Mismatch repair (hMLH1 and hMSH2) and p53 status was investigated immunohistochemically in 111 proximal colon cancers along with tumor TNM stage, grade, and extramural vascular invasion. Fisher's exact test was used to assess categoric data; univariate and multivariate models compared survival between the respective tumor phenotypes.

RESULTS

Thirty-two percent of tumors showed loss of expression of hMLH1 and in a multivariate analysis were associated with a significant survival advantage after adjustment for tumor stage, p53 status, and extramural vascular invasion (hazard ratio, 0.29; 95 percent confidence interval, 0.1-0.87; P = 0.027). Only two tumors showed loss of expression of hMSH2, which was not related further to survival. Aberrant p53 expression was detected in 39 percent of tumors. Such expression was found to be associated with a significantly reduced survival in univariate analysis (P = 0.037, log-rank test) but not in a multivariate model. Subgroup analysis showed no association between survival and p53 expression in mismatch repair proficient tumors.

CONCLUSIONS

Loss of hMLH1 expression is an independent predicator of improved survival in this series and perhaps the underlying cause of the observed survival difference associated with p53 expression.