Genetic pathways in colorectal and other cancers

The role of MLH1, MSH2 and MSH6 in the development of colorectal cancer in Uganda

INTRODUCTION

In Uganda, colorectal cancer (CRC) is steadily increasing according to the Kampala Cancer Registry. In the West, microsatellite instability is detected in 90% of hereditary nonpolyposis colon cancers (HNPCC) which account for 1-2% of all CRC, and 15% of sporadic CRC. Germline mutations in MLH1 and MSH2 account for 90% of HNPCC in the West, whilst the remainder of cases are due to mutations in MSH6 and PMS2. The aim of this study was to determine the microsatellite instability (MSI) status and determine the proportions of MLH1, MSH2, and MSH6 pathological mutations in Ugandan CRC patients.

METHODOLOGY

This was a cross-sectional study carried out between 1st January 2008 to 15th September 2021. Patients were recruited prospectively from 16th September 2019 to 16th September 2021, from Masaka Regional Referral Hospital, Mulago National Referral Hospital, Uganda Martyrs' Hospital Lubaga and Mengo Hospital. From 1st January 2008 to 15th September 2019, CRC FFPE tissue blocks were obtained from the archives of the Department of Pathology, Makerere University. Data was abstracted from the medical case files for demographics, topography and stage. The histopathological subtype and grade of CRC were obtained by two consultant pathologists from the H&E slides. DNA was extracted from CRC formalin-fixed paraffin-embedded (FFPE) tissue blocks. Library preparation was completed using the Qiagen custom design panel. The custom panel represented 56 genes. The MLH-1, MSH2, MSH6, BRAF and KRAS genes were sequenced using the above library preparation and NGS sequencing. The MSI status was obtained if one of the MSI genes, MLH1, MSH2 or MSH6 was pathologically mutated. If none of the genes was pathologically mutated it was considered MSI negative, microsatellite stable (MSS). Immunohistochemistry was carried out to determine whether MLH1 and PMS2 was MMR proficient or deficient. Categorical data was summarized using frequencies and proportions corresponding to each of the three histopathological subtypes and MSI status subtypes. Continuous and categorical variables were analyzed using the chi-square and Fischer's exact tests. A p -value ≤ 0.05 was considered statistically significant for all the analyses.

RESULTS

Out of 127 CRC patients, the mean(SD) age of MSI cases was 55.6(16.9) years and of MSS cases was 55.4(15.5) years. The majority were MSS, 75(59.06%) followed by MSI, 52(40.9%). There were 14(11.02%) MLH-1 mutations, 30(23.62%) MSH2 mutations, and 26(20.47%) MSH6 mutations. BRAF mutational analysis showed only 5(3.9%) having pathologic missense BRAF V600 mutations. KRAS mutations consisted of only 8(6.3%) having pathologic missense KRAS mutations.

CONCLUSIONS

The high rate of MSI in Ugandan colorectal tumours was mainly associated with a lack of BRAF mutations and a high frequency of MSH2 and MSH6 MMR gene mutations. In CRC patients, identification of the causative mutation is recommended, however in a resource-limited setting, MSI testing and immunohistochemistry is more cost effective. In Ugandan CRC patients who meet at least one of the Bethesda criteria, MSI testing and immunohistochemistry may therefore be offered to obtain the MSI status of the tumour.

Analyzing aberrant DNA methylation in colorectal cancer uncovered intangible heterogeneity of gene effects in the survival time of patients

Colorectal cancer (CRC) involves epigenetic alterations. Irregular gene-methylation alteration causes and advances CRC tumor growth. Detecting differentially methylated genes (DMGs) in CRC and patient survival time paves the way to early cancer detection and prognosis. However, CRC data including survival times are heterogeneous. Almost all studies tend to ignore the heterogeneity of DMG effects on survival. To this end, we utilized a sparse estimation method in the finite mixture of accelerated failure time (AFT) regression models to capture such heterogeneity. We analyzed a dataset of CRC and normal colon tissues and identified 3406 DMGs. Analysis of overlapped DMGs with several Gene Expression Omnibus datasets led to 917 hypo- and 654 hyper-methylated DMGs. CRC pathways were revealed via gene ontology enrichment. Hub genes were selected based on Protein-Protein-Interaction network including SEMA7A, GATA4, LHX2, SOST, and CTLA4, regulating the Wnt signaling pathway. The relationship between identified DMGs/hub genes and patient survival time uncovered a two-component mixture of AFT regression model. The genes NMNAT2, ZFP42, NPAS2, MYLK3, NUDT13, KIRREL3, and FKBP6 and hub genes SOST, NFATC1, and TLE4 were associated with survival time in the most aggressive form of the disease that can serve as potential diagnostic targets for early CRC detection.

Gold (III) Derivatives in Colon Cancer Treatment

Cancer is one of the leading causes of morbidity and mortality worldwide. Colorectal cancer (CRC) is the third most frequently diagnosed cancer in men and the second in women. Standard patterns of antitumor therapy, including cisplatin, are ineffective due to their lack of specificity for tumor cells, development of drug resistance, and severe side effects. For this reason, new methods and strategies for CRC treatment are urgently needed. Current research includes novel platinum (Pt)- and other metal-based drugs such as gold (Au), silver (Ag), iridium (Ir), or ruthenium (Ru). Au(III) compounds are promising drug candidates for CRC treatment due to their structural similarity to Pt(II). Their advantage is their relatively good solubility in water, but their disadvantage is an unsatisfactory stability under physiological conditions. Due to these limitations, work is still underway to improve the formula of Au(III) complexes by combining with various types of ligands capable of stabilizing the Au(III) cation and preventing its reduction under physiological conditions. This review summarizes the achievements in the field of stable Au(III) complexes with potential cytotoxic activity restricted to cancer cells. Moreover, it has been shown that not nucleic acids but various protein structures such as thioredoxin reductase (TrxR) mediate the antitumor effects of Au derivatives. The state of the art of the in vivo studies so far conducted is also described.

Nanomedicines in the treatment of colon cancer: a focus on metallodrugs

Worldwide, colon cancer (CC) represents the fourth most common type of cancer and the fifth major cause of cancer-associated deaths. Surgical resection is considered the standard therapeutic choice for CC in early stages. However, in latter stages of the disease, adjuvant chemotherapy is essential for an appropriate management of this pathology. Metal-based complexes displaying cytotoxic properties towards tumor cells emerge as potential chemotherapeutic options. One metallodrug, oxaliplatin, was already approved for clinical use, playing an important role in the treatment of CC patients. Unfortunately, most of the newly designed metal-based complexes exhibit lack of selectivity against cancer cells, low solubility and permeability, high dose-limiting toxicity, and emergence of resistances. Nanodelivery systems enable the incorporation of metallodrugs at adequate payloads, solving the above-referred drawbacks. Moreover, drug delivery systems, depending on their physicochemical properties, are able to release the incorporated material preferentially at affected tissues/organs, enhancing the therapeutic activity in vivo, with concomitant fewer side effects. In this review, the general features and therapeutic management of CC will be addressed, with a special focus on preclinical or clinical studies using metal-based compounds. Furthermore, the use of different nanodelivery systems will also be described as tools to potentiate the therapeutic index of metallodrugs for the management of CC.

Personalised mapping of tumour development in synchronous colorectal cancer patients

Synchronous colorectal cancers (syCRCs) are two or more primary tumours identified simultaneously in a patient. Previous studies report high inter-tumour heterogeneity between syCRCs, suggesting independent origin and different treatment response, making their management particularly challenging, with no specific guidelines currently in place. Here, we performed in-depth bioinformatic analyses of genomic and transcriptomic data of a total of eleven syCRCs and one metachronous CRC collected from three patients. We found mixed microsatellite status between and within patients. Overlap of mutations between synchronous tumours was consistently low (<0.5%) and heterogeneity of driver events across syCRCs was high in all patients. Microbial analysis revealed the presence of Fusobacterium nucleatum species in patients with MSI tumours, while quantification of tumour immune infiltration showed varying immune responses between syCRCs. Our results suggest high heterogeneity of syCRCs within patients but find clinically actionable biomarkers that help predict responses to currently available targeted therapies. Our study highlights the importance of personalised genome and transcriptome sequencing of all synchronous lesions to aid therapy decision and improve management of syCRC patients.

Modelling the effect of subcellular mutations on the migration of cells in the colorectal crypt

Background

Many cancers arise from mutations in cells within epithelial tissues. Mutations manifesting at the subcellular level influence the structure and function of the tissue resulting in cancer. Previous work has proposed how cell level properties can lead to mutant cell invasion, but has not incorporated detailed subcellular modelling

Results

We present a framework that allows the straightforward integration and simulation of SBML representations of subcellular dynamics within multiscale models of epithelial tissues. This allows us to investigate the effect of mutations in subcellular pathways on the migration of cells within the colorectal crypt. Using multiple models we find that mutations in APC, a key component in the Wnt signalling pathway, can bias neutral drift and can also cause downward invasion of mutant cells in the crypt.

Conclusions

Our framework allows us to investigate how subcellular mutations, i.e. knockouts and knockdowns, affect cell-level properties and the resultant migration of cells within epithelial tissues. In the context of the colorectal crypt, we see that mutations in APC can lead directly to mutant cell invasion.

Mechanism of Apoptosis Induced by Curcumin in Colorectal Cancer

Colorectal cancer (CRC) is among the top three cancer with higher incident and mortality rate worldwide. It is estimated that about over than 1.1 million of death and 2.2 million new cases by the year 2030. The current treatment modalities with the usage of chemo drugs such as FOLFOX and FOLFIRI, surgery and radiotherapy, which are usually accompanied with major side effects, are rarely cured along with poor survival rate and at higher recurrence outcome. This trigger the needs of exploring new natural compounds with anti-cancer properties which possess fewer side effects. Curcumin, a common spice used in ancient medicine was found to induce apoptosis by targeting various molecules and signaling pathways involved in CRC. Disruption of the homeostatic balance between cell proliferation and apoptosis could be one of the promoting factors in colorectal cancer progression. In this review, we describe the current knowledge of apoptosis regulation by curcumin in CRC with regard to molecular targets and associated signaling pathways.

THE CANONICAL WNT PATHWAY IN GASTRIC CARCINOMA

Background:

It is believed that the Wnt pathway is one of the most important signaling involved in gastric carcinogenesis.

Aim:

To analyze the protein expression of canonical and non-canonical Wnt pathways in gastric carcinoma.

Method:

The immunohistochemistry was performed in 72 specimens of gastric carcinomas for evaluating the expression of Wnt-5a, FZD5, GSK3β, axin, CK1, ubiquitin, cyclin D1 and c-myc.

Results:

There were significant differences for cytoplasm and nucleus ubiquitin for moderately and well differentiated tumors (p=0.03) and for those of the intestinal type of the Lauren classification (p=0.03). The absence of c-myc was related to Lauren’s intestinal tumors (p=0.03). Expression of CK1 in the cytoplasm was related to compromised margin (p=0.03). Expression of cyclin D1 protein was more intense in male patients (p=0.03) There was no relation of the positive or negative expression of the Wnt-5a, FZD5, GSK3 and Axin with any clinicopathological variables.

Conclusion:

The canonical WNT pathway is involved in gastric carcinoma.

Evaluation of potential anti-cancer activity of cationic liposomal nanoformulated Lycopodium clavatum in colon cancer cells

Research dealing with early diagnosis and efficient treatment in colon cancer to improve patient's survival is still under investigation. Chemotherapeutic agent result in high systemic toxicity due to their non-specific actions on DNA repair and/or cell replication. Traditional medicine such as Lycopodium clavatum (LC) has been claimed to have therapeutic potentials against cancer. The present study focuses on targeted drug delivery of cationic liposomal nanoformulated LC (CL-LC) in colon cancer cells (HCT15) and comparing the efficacy with an anti-colon cancer drug, 7-ethyl-10-hydroxy-camptothecin (SN38) along with its nanoformulated form (CL-SN38). The colloidal suspension of LC was made using thin film hydration method. The drugs were characterised using ultraviolet, dynamic light scattering, scanning electron microscopy, energy, dispersive X-ray spectroscopy. Invitro drug release showed kinetics of 49 and 89% of SN38 and LC, whereas CL-SN38 and CL-LC showed 73 and 74% of sustained drug release, respectively. Studies on morphological changes, cell viability, cytotoxicity, apoptosis, cancer-associated gene expression analysis of Bcl-2, Bax, p53 by real-time polymerase chain reaction and western blot analysis of Bad and p53 protein were performed. Nanoformulated LC significantly inhibited growth and increased the apoptosis of colon cancer cells indicating its potential anti-cancer activity against colon cancer cells.

Forward and reverse mutations in stages of cancer development

Background

Massive occurrences of interstitial loss of heterozygosity (LOH) likely resulting from gene conversions were found by us in different cancers as a type of single-nucleotide variations (SNVs), comparable in abundance to the commonly investigated gain of heterozygosity (GOH) type of SNVs, raising the question of the relationships between these two opposing types of cancer mutations.

Methods

In the present study, SNVs in 12 tetra sample and 17 trio sample sets from four cancer types along with copy number variations (CNVs) were analyzed by AluScan sequencing, comparing tumor with white blood cells as well as tissues vicinal to the tumor. Four published “nontumor”-tumor metastasis trios and 246 pan-cancer pairs analyzed by whole-genome sequencing (WGS) and 67 trios by whole-exome sequencing (WES) were also examined.

Results

Widespread GOHs enriched with CG-to-TG changes and associated with nearby CNVs and LOHs enriched with TG-to-CG changes were observed. Occurrences of GOH were 1.9-fold higher than LOH in “nontumor” tissues more than 2 cm away from the tumors, and a majority of these GOHs and LOHs were reversed in “paratumor” tissues within 2 cm of the tumors, forming forward-reverse mutation cycles where the revertant LOHs displayed strong lineage effects that pointed to a sequential instead of parallel development from “nontumor” to “paratumor” and onto tumor cells, which was also supported by the relative frequencies of 26 distinct classes of CNVs between these three types of cell populations.

Conclusions

These findings suggest that developing cancer cells undergo sequential changes that enable the “nontumor” cells to acquire a wide range of forward mutations including ones that are essential for oncogenicity, followed by revertant mutations in the “paratumor” cells to avoid growth retardation by excessive mutation load. Such utilization of forward-reverse mutation cycles as an adaptive mechanism was also observed in cultured HeLa cells upon successive replatings. An understanding of forward-reverse mutation cycles in cancer development could provide a genomic basis for improved early diagnosis, staging, and treatment of cancers.

Electronic supplementary material

The online version of this article (10.1186/s40246-018-0170-6) contains supplementary material, which is available to authorized users.

N_LyST: a simple and rapid screening test for Lynch syndrome

Aims

We sought to use PCR followed by high-resolution melting analysis to develop a single closed-tube screening panel to screen for Lynch syndrome. This comprises tests for microsatellite instability (MSI), MLH1 methylation promoter and BRAF mutation.

Methods

For MSI testing, five mononucleotide markers (BAT25, BAT26, BCAT25, MYB, EWSR1) were developed. In addition, primers were designed to interrogate Region C of the MLH1 promoter for methylation (using bisulphite-modified DNA) and to test for mutations in codon 600 of BRAF. Two separate cohorts from Nottingham (n=99, 46 with MSI, 53 being microsatellite stable (MSS)) and Edinburgh (n=88, 45 MSI, 43 MSS) were tested.

Results

All the cases (n=187) were blind tested for MSI and all were correctly characterised by our panel. The MLH1 promoter and BRAF were tested only in the Nottingham cohort. Successful blinded analysis was performed on the MLH1 promoter in 97 cases. All MSS cases showed a pattern of non-methylation while 41/44 cases with MSI showed full methylation. The three cases with MSI and a non-methylated pattern had aberrations in MSH2 and MSH6 expression. BRAF mutation was detected in 61% of MSI cases and 11% of MSS cases.

Finally, 12 cases were blind screened by using the whole panel as a single test. Of these, five were identified as MSS, four as MSI/non-LS and three as MSI/possible LS. These results were concordant with the previous data.

Conclusion

We describe the Nottingham Lynch Syndrome Test (N_LyST). This is a quick, simple and cheap method for screening for Lynch syndrome.

Terpenoids as anti-colon cancer agents - A comprehensive review on its mechanistic perspectives

Multistep model of colon carcinogenesis has provided the framework to advance our understanding of the molecular basis of colon cancer. This multistage process of carcinogenesis takes a long period to transform from a normal epithelial cell to invasive carcinoma. Thus, it provides enough time to intervene the process of carcinogenesis especially through dietary modification. In spite of the in-depth understanding of the colon cancer etiology and pathophysiology and its association with diet, colon cancer remains a major cause of cancer mortality worldwide. Phytochemicals and their derivatives are gaining attention in cancer prevention and treatment strategies because of cancer chemotherapy associated adverse effects. Being the largest group of phytochemicals traditionally used for medicinal purpose in India and China, terpenoids are recently being explored as anticancer agents. Anticancer properties of terpenoids are associated with various mechanisms like counteraction of oxidative stress, potentiating endogenous antioxidants, improving detoxification potential, disrupting cell survival pathways and inducing apoptosis. This review gives a comprehensive idea of naturally occurring terpenoids as useful agents for the prevention of colon cancer with reference to their classes, sources and molecular targets. Based on the explored molecular targets further research in colon cancer chemoprevention is warranted.

MIIP haploinsufficiency induces chromosomal instability and promotes tumour progression in colorectal cancer

The gene encoding migration and invasion inhibitory protein (MIIP), located on 1p36.22, is a potential tumour suppressor gene in glioma. In this study, we aimed to explore the role and mechanism of action of MIIP in colorectal cancer (CRC). MIIP protein expression gradually decreased along the colorectal adenoma-carcinoma sequence and was negatively correlated with lymph node and distant metastasis in 526 colorectal tissue samples (p < 0.05 for all). Analysis of The Cancer Genome Atlas (TCGA) data showed that decreased MIIP expression was significantly associated with MIIP hemizygous deletion (p = 0.0005), which was detected in 27.7% (52/188) of CRC cases, and associated with lymph node and distant metastasis (p < 0.05 for both). We deleted one copy of the MIIP gene in HCT116 CRC cells using zinc finger nuclease technology and demonstrated that MIIP haploinsufficiency resulted in increased colony formation and cell migration and invasion, which was consistent with the results from siRNA-mediated MIIP knockdown in two CRC cell lines (p < 0.05 for all). Moreover, MIIP haploinsufficiency promoted CRC progression in vivo (p < 0.05). Genomic instability and spectral karyotyping assays demonstrated that MIIP haploinsufficiency induced chromosomal instability (CIN). Besides modulating the downstream proteins of APC/C^Cdc20 , securin and cyclin B1, MIIP haploinsufficiency inhibited topoisomerase II (Topo II) activity and induced chromosomal missegregation. Therefore, we report that MIIP is a novel potential tumour suppressor gene in CRC. Moreover, we characterized the MIIP gene as a novel CIN suppressor gene, through altering the stability of mitotic checkpoint proteins and disturbing Topo II activity. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Inflammation-based factors and prognosis in patients with colorectal cancer

Several parameters for predicting survival in patients with colorectal cancer have been identified, including the performance status, age, gender and tumor-node-metastasis (TNM) stage. Although the TNM stage is important and useful for predicting the prognosis and determining the appropriate treatment, it is well known that the survival time varies widely, even in patients with the same stage of disease. Therefore, the identification of new parameters capable of more precisely predicting patient survival is needed to help select the optimal treatment, especially in patients in the advanced stage of disease. Although the TNM stage reflects the tumor characteristics, cancer progression and survival are not determined solely based on the local characteristics of the tumor, but also the host systemic immune/inflammatory response. Therefore, using a combination of parameters that reflect both tumor characteristics and the host systemic inflammatory status is thought to be important for accurately predicting patient survival.

The hMLH1 -93G>A Polymorphism and Risk of Ovarian Cancer in the Chinese Population

Background

As a mismatch repair (MMR) gene, hMLH1 plays an important role in the maintenance of chromosomal integrity. Several studies have investigated the associations of hMLH1 -93G>A (rs1800734) and Ile219Val (rs1799977) in diverse tumor types with discordant results, but their roles in ovarian cancer in the Chinese population remains to be elucidated.

Methods

In a case-control analysis, we assessed the association between these two polymorphisms and ovarian cancer risk in 421 ovarian cancer patients and 689 control subjects in the Chinese population using logistic regression.

Results

We found that the variant hMLH1 genotypes (-93AA and AG) are associated with risk of ovarian cancer (adjusted odds ratio [OR] = 2.02, 95% confidence interval [CI] = 1.42–2.89) compared with the -93GG genotype. The A allele increases the risk of ovarian cancer in a dose-dependent manner (P<10⁻⁴). Functional test showed that -93A allele increased hMLH1 promoter transcriptional activity and the luciferase activity. However, no significant difference was found in the genotype frequencies at the Ile219Val site between the cases and controls.

Conclusions

These findings indicate that the -93G>A polymorphism in hMLH1 may affect ovarian cancer susceptibility in the Chinese population.

Genetic markers of recurrence in colorectal cancer

Colorectal cancer (CRC) worldwide belongs to one of the most frequent cancers affecting both genders. Surgery and 5-fluorouracil-based adjuvant chemotherapy are recommended for patients with high-risk stage II and stage III colon carcinoma. Mutations of genes encoding for specific proteins may have an impact on the time to recurrence. These proteins act over specific signaling pathways, are implicated in metabolic processes and regulate the cell cycle. Though many retrospective studies show strong associations between genetic mutations and the clinical outcome of patients with CRC, currently no validated biomarkers are used in clinical routine settings. Therefore, large prospective validation studies should be carried out in order to strengthen the position of genetic mutations in personalized treatment of patients with CRC.

Analysis of Wnt signalling dynamics during colon crypt development in 3D culture

Many systems biology studies lack context-relevant data and as a consequence the predictive capabilities can be limited in developing targeted cancer therapeutics. Production of colon crypt in vitro is ideal for studying colon systems biology. This report presents the first production of, to our knowledge, physiologically-shaped, functional colon crypts in vitro (i.e. single crypts with cells expressing Mucin 2 and Chromogranin A). Time-lapsed monitoring of crypt formation revealed an increased frequency of single-crypt formation in the absence of noggin. Using quantitative 3D immunofluorescence of β-catenin and E-cadherin, spatial-temporal dynamics of these proteins in normal colon crypt cells stimulated with Wnt3A or inhibited by cycloheximide has been measured. Colon adenoma cultures established from APC^min/+ mouse have developmental differences and β-catenin spatial localization compared to normal crypts. Quantitative data describing the effects of signalling pathways and proteins dynamics for both normal and adenomatous colon crypts is now within reach to inform a systems approach to colon crypt biology.

Bcl11b SWI/SNF-complex subunit modulates intestinal adenoma and regeneration after γ-irradiation through Wnt/β-catenin pathway

SWI/SNF chromatin remodeling complexes constitute a highly related family of multi-subunit complexes to modulate transcription, and SWI/SNF subunit genes are collectively mutated in 20% of all human cancers. Bcl11b is a SWI/SNF subunit and acts as a haploinsufficient tumor suppressor in leukemia/lymphomas. Here, we show expression of Bcl11b in intestinal crypt cells and promotion of intestinal tumorigenesis by Bcl11b attenuation in Apc (min/+) mice. Of importance, mutations or allelic loss of BCL11B was detected in one-third of human colon cancers. We also show that attenuated Bcl11b activity in the crypt base columnar (CBC) cells expressing the Lgr5 stem cell marker enhanced regeneration of intestinal epithelial cells after the radiation-induced injury. Interestingly, BCL11B introduction in human cell lines downregulated transcription of β-catenin target genes, whereas Bcl11b attenuation in Lgr5(+) CBCs increased expression of β-catenin targets including c-Myc and cyclin D1. Together, our results argue that Bcl11b impairment promotes tumor development in mouse and human intestine at least in part through deregulation of β-catenin pathway.

Management of colorectal cancer

Colorectal cancer is one of the most frequent solid tumors in the Western world. Treatment options are dependent on the stage of the disease, the performance status of the patient, and increasingly the molecular makeup of the tumor. In countries with surveillance programs, the incidence rate as well as the mortality rate has gone down because of the earlier stages at which the tumors are detected. For rectal cancer, standard of care differs from that of colon cancer with regard to perioperative treatment. In the metastatic setting, treatment options are uniform for colorectal cancer. Over the years, treatment options have emerged from single-agent 5-fluorouracil (5-FU) treatment to combination regimens using 5-FU and oxaliplatin or irinotecan or both. Treatment efficacy in the metastatic setting has been increased with the introduction of targeted substances. These include (a) the anti-vascular endothelial growth factor-A (anti-VEGF-A) antibody bevacizumab, (b) the anti-epidermal growth factor receptor (anti-EGFR) antibodies cetuximab and panitumumab, (c) the anti-angiogenic multi-kinase inhibitor regorafenib, and (d) the anti-angiogenic compound aflibercept. Anti-EGFR antibodies have shown efficacy only in the subpopulations of tumors that do not have any mutation in KRAS and NRAS exon 2, 3, 4. Physicians have the choice in the first line to use anti-EGFR or anti-VEGF inhibitors in combination with chemotherapy based on treatment goals and patient performance. In recent years, tumor location has been shown to be prognostic and predictive for clinical outcome. Right-sided sporadic colon cancers differ significantly in molecular characteristics and, with the exception of microsatellite instability (MSI-H) tumors, are associated with poor prognosis. Tumors based on hereditary non-polyposis colorectal cancer, on the other hand, have excellent prognosis in stage II and III disease. Recent efforts have focused on the molecular classification of colorectal cancer with the purpose of establishing molecularly defined subgroups.

STAT3 paradoxically stimulates β-catenin expression but inhibits β-catenin function

Wnt signalling and the signal transducer and activator of transcription 3 (STAT3) are oncogenic signalling pathways which are deregulated in colorectal cancer (CRC). Here we investigated the interaction of these two pathways. Firstly, we investigated biochemical interaction by inhibiting STAT3 and β-catenin (through gene knock-down and dominant-negative TCF4 expression) in nine CRC cell lines. β-catenin inhibition did not affect STAT3 levels, whereas STAT3 knock-down resulted in reduced β-catenin mRNA and protein levels. The reduction in β-catenin protein was not prevented by proteasome inhibition, and IL6-induced STAT3 activation resulted in increased β-catenin mRNA. This suggests that STAT3 positively regulates β-catenin (at a transcriptional level) and evaluation of 44 CRCs by immunostaining supported this by showing an association between nuclear STAT3 expression and nuclear β-catenin (P = 0.022). We tested the functional interaction between STAT3 and Wnt signalling by knocking down STAT3 and β-catenin individually and in combination. Knock-down of β-catenin and STAT3 individually inhibited cell proliferation (P < 0. 001 for each) through G1 arrest. However, simultaneous knock-down of STAT3 and β-catenin had a significantly weaker effect than knock-down of β-catenin alone (P < 0.01). Knock-down of STAT3 and β-catenin, individually and together, inhibited cell motility (P < 0.001) without evidence of interaction. We conclude that STAT3 regulates β-catenin but β-catenin does not regulate STAT3. The STAT3/β-catenin interaction is complex but may reduce the proliferative activity of β-catenin possibly by taking β-catenin protein beyond the optimal level. This may indicate biological differences in tumours where both STAT3 and β-catenin are activated compared to those where only one is activated.

tRNA modifications regulate translation during cellular stress

The regulation of gene expression in response to stress is an essential cellular protection mechanism. Recent advances in tRNA modification analysis and genome-based codon bias analytics have facilitated studies that lead to a novel model for translational control, with translation elongation dynamically regulated during stress responses. Stress-induced increases in specific anticodon wobble bases are required for the optimal translation of stress response transcripts that are significantly biased in the use of degenerate codons keyed to these modified tRNA bases. These findings led us to introduce the notion of tRNA modification tunable transcripts (MoTTs - transcripts whose translation is regulated by tRNA modifications), which are identifiable using genome-wide codon counting algorithms. In support of this general model of translational control of stress response, studies making use of detailed measures of translation, tRNA methyltransferase mutants, and computational and mass spectrometry approaches reveal that stress reprograms tRNA modifications to translationally regulate MoTTs linked to arginine and leucine codons, which helps cells survive insults by damaging agents. These studies highlight how tRNA methyltransferase activities and MoTTs are key components of the cellular stress response.

Phospholipase Cδ1 induces E-cadherin expression and suppresses malignancy in colorectal cancer cells

Colorectal cancer (CRC) is one of the most common causes of cancer-related deaths worldwide, and Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations in CRC predict the ineffectiveness of EGF receptor-targeted therapy. Previous transcriptional microarray analysis suggests the association between phospholipase Cδ1 (PLCδ1) expression and KRAS mutation status in CRC. However, both the roles and the regulatory mechanisms of PLCδ1 in CRC are not known. Here, we found that the expression of PLCδ1, one of the most basal PLCs, is down-regulated in CRC specimens compared with normal colon epithelium by immunohistochemistry. Furthermore, we examined the roles of PLCδ1 in CRC cell lines that harbor an activating KRAS mutation. Ectopic expression of PLCδ1 in CRC cells induced the expression of E-cadherin, whereas knockdown of PLCδ1 repressed the expression of E-cadherin. Moreover, the overexpression of PLCδ1 suppressed the expression of several mesenchymal genes and reduced cell motility, invasiveness, and in vivo tumorigenicity of SW620 CRC cells. We also showed that PLCδ1 expression is repressed by the KRAS/mitogen-activated protein kinase kinase (MEK) pathway. Furthermore, PLCδ1 suppressed the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 through E-cadherin induction in CRC cells, suggesting the presence of a negative regulatory loop between KRAS/MEK/ERK signaling and PLCδ1. These data indicate that PLCδ1 has tumor-suppressive functions in CRC through E-cadherin induction and KRAS/MEK/ERK signal attenuation.

RAS testing of colorectal carcinoma—a guidance document from the Association of Clinical Pathologists Molecular Pathology and Diagnostics Group

Analysis of colorectal carcinoma (CRC) tissue for KRAS codon 12 or 13 mutations to guide use of anti-epidermal growth factor receptor (EGFR) therapy is now considered mandatory in the UK. The scope of this practice has been recently extended because of data indicating that NRAS mutations and additional KRAS mutations also predict for poor response to anti-EGFR therapy. The following document provides guidance on RAS (i.e., KRAS and NRAS) testing of CRC tissue in the setting of personalised medicine within the UK and particularly within the NHS. This guidance covers issues related to case selection, preanalytical aspects, analysis and interpretation of such RAS testing.

A novel AMPK activator reduces glucose uptake and inhibits tumor progression in a mouse xenograft model of colorectal cancer

The anticancer activity of a novel pure 1,4-Diaryl-2-azetidinone (1), endowed with a higher solubility than the well known Combretastatin A4, is tested in mice. We previously reported that Compound (1) showed specific antiproliferative activity against duodenal and colon cancer cells, inducing activation of AMP-activated protein kinase and apoptosis. Here we estimate that the maximum tolerated dose in a mouse model is 40 mg/kg; the drug is well tolerated both in single dose and in repeated administration schedules. The drug displays a significant antitumor activity and a tumor growth delay when administered at the MTD both in single and fractionated i.v. administration in a mouse xenograft model of colorectal cancer. Arrest of tumor growth and relapse after drug suspension are parallel to modification in glucose demand as shown by PET studies with [(18)F] FDG. These data strongly support Compound (1) as a promising molecule for in vivo treatment of colorectal cancer.

DNA content analysis of colorectal cancer defines a distinct 'microsatellite and chromosome stable' group but does not predict response to radiotherapy

Colorectal cancers (CRC) are thought to have genetic instability in the form of either microsatellite instability (MSI) or chromosomal instability (CIN). Recently, tumours have been described without either MSI or CIN, that is, microsatellite and chromosome stable (MACS) CRCs. We investigated the (i) frequency of the MACS-CRCs and (ii) whether this genotype predicted responsiveness to neoadjuvant chemoradiotherapy. To examine the frequency of MACS-CRCs, DNA content (ploidy) was examined in 89 sporadic microsatellite-stable CRCs using flow cytometry. The tumours were also screened for mutations in KRAS/BRAF/TP53/PIK3CA by QMC-PCR. To examine the value of tumour ploidy in predicting response to chemoradiotherapy, DNA content was tested in a separate group of 62 rectal cancers treated with neoadjuvant chemoradiotherapy. Fifty-one of 89 CRCs (57%) were aneuploid and 38 (43%) were diploid. There was no significant association between mutations in TP53/KRAS/BRAF/PIK3CA and ploidy. Testing of association between mutations revealed only mutual exclusivity of KRAS/BRAF mutation (P < 0.001). Of the 62 rectal cancers treated with neoadjuvant chemoradiotherapy, 22 had responded (Mandard tumour regression grade 1/2) and 40 failed to respond (Grade 3-5). Twenty-five of 62 (40%) tumours were diploid, but there was no association between ploidy and response to therapy. We conclude that MACS-CRCs form a significant proportion of microsatellite-stable CRCs with a mutation profile overlapping that of CRCs with CIN. A diploid genotype does not, however, predict the responsiveness to radiotherapy.

Management of colorectal cancer

Colorectal cancer is one of the most frequent solid tumors in the Western world. Treatment options are dependent on the stage of the disease, the performance status of the patient, and increasingly the molecular makeup of the tumor. In countries with surveillance programs, the incidence rate as well as the mortality rate has gone down because of the earlier stages at which the tumors are detected. For rectal cancer, standard of care differs from that of colon cancer with regard to perioperative treatment. In the metastatic setting, treatment options are uniform for colorectal cancer. Over the years, treatment options have emerged from single-agent 5-fluorouracil (5-FU) treatment to combination regimens using 5-FU and oxaliplatin or irinotecan or both. Treatment efficacy in the metastatic setting has been increased with the introduction of targeted substances. These include (a) the anti-vascular endothelial growth factor-A (anti-VEGF-A) antibody bevacizumab, (b) the anti-epidermal growth factor receptor (anti-EGFR) antibodies cetuximab and panitumumab, (c) the anti-angiogenic multi-kinase inhibitor regorafenib, and (d) the anti-angiogenic compound aflibercept. Anti-EGFR antibodies have shown efficacy only in the subpopulations of tumors that do not have any mutation in KRAS and NRAS exon 2, 3, 4. Physicians have the choice in the first line to use anti-EGFR or anti-VEGF inhibitors in combination with chemotherapy based on treatment goals and patient performance. In recent years, tumor location has been shown to be prognostic and predictive for clinical outcome. Right-sided sporadic colon cancers differ significantly in molecular characteristics and, with the exception of microsatellite instability (MSI-H) tumors, are associated with poor prognosis. Tumors based on hereditary non-polyposis colorectal cancer, on the other hand, have excellent prognosis in stage II and III disease. Recent efforts have focused on the molecular classification of colorectal cancer with the purpose of establishing molecularly defined subgroups.

Colon cryptogenesis: asymmetric budding

The process of crypt formation and the roles of Wnt and cell-cell adhesion signaling in cryptogenesis are not well described; but are important to the understanding of both normal and cancer colon crypt biology. A quantitative 3D-microscopy and image analysis technique is used to study the frequency, morphology and molecular topography associated with crypt formation. Measurements along the colon reveal the details of crypt formation and some key underlying biochemical signals regulating normal colon biology. Our measurements revealed an asymmetrical crypt budding process, contrary to the previously reported symmetrical fission of crypts. 3D immunofluorescence analyses reveals heterogeneity in the subcellular distribution of E-cadherin and β-catenin in distinct crypt populations. This heterogeneity was also found in asymmetrical budding crypts. Singular crypt formation (i.e. no multiple new crypts forming from one parent crypt) were observed in crypts isolated from the normal colon mucosa, suggestive of a singular constraint mechanism to prevent aberrant crypt production. The technique presented improves our understanding of cryptogenesis and suggests that excess colon crypt formation occurs when Wnt signaling is perturbed (e.g. by truncation of adenomatous polyposis coli, APC protein) in most colon cancers.

Sessile serrated adenomas in the proximal colon are likely to be flat, large and occur in smokers

AIM

To examine the epidemiology and the morphology of the proximal sessile serrated adenomas (SSAs).

METHODS

We conducted a retrospective study to identify patients with SSAs using a university-based hospital pathology database query from January 2007 to April 2011. Data collected included: age, gender, ethnicity, body mass index, diabetes, smoking, family history of colorectal cancer, aspirin, and statin use. We collected data on morphology of SSAs including site (proximal or distal), size, and endoscopic appearance (flat or protuberant). We also compared proximal SSAs to proximal tubular adenomas detected during same time period.

RESULTS

One hundred and twenty patients with SSAs were identified: 61% were distal and 39% were proximal SSAs. Proximal SSAs were more likely to be flat than distal (100% vs 78% respectively; P = 0.0001). Proximal SSAs were more likely to occur in smokers (OR = 2.63; 95%CI: 1.17-5.90; P = 0.02) and in patients with family history of colorectal cancer (OR = 4.72; 95%CI: 1.43-15.55; P = 0.01) compared to distal. Proximal SSAs were statistically more likely to be ≥ 6 mm in size (OR = 2.94; P = 0.008), and also more likely to be large (≥ 1 cm) (OR = 4.55; P = 0.0005) compared to the distal lesions. Smokers were more likely to have proximal (P = 0.02), flat (P = 0.01) and large (P = 0.007) SSAs compared to non-smokers. Compared to proximal tubular adenomas, proximal SSAs were more likely to be large and occur in smokers.

CONCLUSION

Proximal SSAs which accounted for two-fifths of all SSAs were more likely to present as flat lesions, larger SSAs, and were more likely to occur in smokers and in patients with family history of colorectal cancer. Our data has implications for colorectal cancer screening.

Polyp and adenoma detection rates in the proximal and distal colon

OBJECTIVES

Little is known about the correlation between the polyp detection rate (PDR) and the adenoma detection rate (ADR) in individual colonic segments. The adenoma-to-polyp detection rate quotient (APDRQ) has been utilized in retrospective study as a constant to estimate ADR from PDR. It has been previously stated that diminutive polyps in the rectum are more likely to be non-adenomatous, compared with more proximal segments, yet the APDRQ uses data from the entire colon. We sought to characterize and compare ADR and PDR in each colonic segment, estimate ADR using the conversion factor, APDRQ, and assess the correlation between estimated and actual ADR for each colonic segment.

METHODS

As part of a quality improvement program, a retrospective chart review was conducted of all outpatient colonoscopies performed by 20 gastroenterologists between 1 October 2010 and 31 March 2011 at a single academic tertiary-care referral center. PDR, ADR, and the APDRQ were calculated for each gastroenterologist, using data from the entire colon and then for each colonic segment separately. Actual ADR was compared with estimated ADR based on the measured APDRQ.

RESULTS

During 1,921 colonoscopies, 2,285 polyps were removed; 1,122 (49%) were adenomas. The mean (s.d.) PDR for the group was 49% (12.4%) (range, 16-64%). The mean (s.d.) ADR was 31% (7.4%) (range, 13-42%). PDR and ADR correlated well in segments proximal to the splenic flexure, but diverged in distal segments. ADR was significantly higher in the right colon (17.1%) than in the left (13.5%) (P=0.001). The correlation between estimated and actual ADR using the APDRQ was significantly higher in the right colon (r=0.95 (95% confidence interval (CI), 0.87-0.98)) than in the left (r=0.59 (95% CI, 0.17-0.83)) (P<0.05).

CONCLUSIONS

Although PDR and ADR correlate well in segments proximal to the splenic flexure, they do not correlate well in the left colon. Caution should be exercised when using PDR as a surrogate for ADR if data from the rectum and sigmoid are included.

Single nucleotide polymorphism in hMLH1 promoter and risk of tobacco-related oral carcinoma in high-risk Asian Indians

hMLH1 is a member of mismatch repair genes (MMR) that plays a crucial role in correcting replication errors, cell cycle arrest, apoptosis and oxidative stress. We explored the risk associated with hMLH1 -93 A>G (rs 1800734) single nucleotide polymorphism (SNP) with the oral squamous cell carcinoma (OSCC) in Asian Indians. We genotyped 242 patients with tobacco-related OSCC and 205 healthy controls by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. The frequency of AA genotype was found to be significantly (Pc<0.0006) lower in patients as compared to the controls (21.49% vs. 47.8%) while GG genotype showed significantly higher (Pc<0.0006) prevalence in patients as compared to the healthy controls (41.32% vs. 13.66%). In logistic regression analysis AG (adjusted OR=1.95, 95% CI=0.72-5.26) and GG genotype (adjusted OR=4.5, 95% CI=1.54-13.16, P=0.006) appeared susceptible when compared with the wild-type AA genotype. The allelic distribution showed that variant G allele is significantly higher (Pc<0.0004) in patients and associated with increased risk (adjusted OR=2.36, 95% CI=1.33-4.19, P=0.003) as compared to the wild-type A allele. Altogether, our results suggest that the hMLH1 -93 A>G polymorphism is associated with the higher risk of tobacco-related OSCC in Asian Indians and could be useful in screening population at a higher risk.

Alterations in K-ras, APC and p53-multiple genetic pathway in colorectal cancer among Indians

The incidence of colorectal cancer (CRC) is increasing rapidly in Asian countries during the past few decades, but no comprehensive analysis has been done to find out the exact cause of this disease. In this study, we investigated the frequencies of mutations and expression pattern of K-ras, APC (adenomatosis polyposis coli) and p53 in tumor, adjoining and distant normal mucosa and to correlate these alterations with patients clinicopathological parameters as well as with the survival. Polymerase chain reaction (PCR)-restriction digestion was used to detect mutations in K-ras and PCR-SSCP (Single Strand Conformation Polymorphism) followed by DNA sequencing was used to detect mutations in APC and p53 genes. Immunohistochemistry was used to detect the expression pattern of K-ras, APC and p53 proteins. The frequencies of mutations of K-ras, APC and p53 in 30 tumor tissues samples were 26.7 %, 46.7 % and 20 %, respectively. Only 3.3 % of tumors contained mutations in all the three genes. The most common combination of mutation was APC and p53 whereas mutation in both p53 and K-ras were extremely rare. There was no association between the mutations and expression pattern of K-ras, APC and p53 (p>0.05). In Indians, the frequency of alterations of K-ras and APC is similar as in Westerns, whereas the frequency of p53 mutation is slightly lower. The lack of multiple mutations in tumor specimens suggests that these genetic alterations might have independent influences on CRC development and there could be multiple alternative genetic pathways to CRC in our present study cohort.

Aberrant promoter methylation of the RASSF1A and APC genes in epithelial ovarian carcinoma development

PURPOSE

Tumor suppressor gene (TSG) silencing through promoter hypermethylation plays an important role in cancer development. The aim of this study was to assess the extent of methylation of the RASSF1A and APC TSG promoters in ovarian epithelial adenomas, low malignant potential tumours and carcinomas in order to reveal a role for epigenetic TSG silencing in the development of these ovarian malignancies.

METHOD

The promoter methylation status of the RASSF1A and APC genes was assessed in 19 benign cystadenomas, 14 low malignant potential (LMP) tumours, and 86 carcinomas using methylation specific PCR (MSP).

RESULTS

The methylation frequencies of the RASSF1A and APC gene promoters in benign cystadenomas were found to be 37 % and 16 %, respectively. The LMP tumours exhibited RASSF1A and APC gene promoter methylation frequencies of 50 % and 28 %, respectively, whereas the carcinomas exhibited methylation frequencies of 58 % and 29 %, respectively. Methylation of either the RASSF1A or the APC gene promoter was encountered in 58 % of the invasive carcinomas.

CONCLUSION

The observed aberrant methylation frequencies of the RASSF1A and APC gene promoters indicate that an accumulation of epigenetic events at these specific TSG promoters may be associated with the malignant transformation of benign cystadenomas and LMP tumours to carcinomas.

Inverse Correlation Between an Organ's Cancer Rate and Its Evolutionary Antiquity

Human cancer rates vary dramatically across the range of internal organs in the body, but there is no single model to explain the variation and there is also no obvious overall pattern to it. Theories have been proposed to account for high rates in particularly cancer-prone organs, and they usually concentrate on the peculiar vulnerability of certain cells to mutation (e.g., lung cells' direct exposure to airborne carcinogens). These explanations are valuable for understanding mechanisms of disease and also for cancer prevention, but they address neither the overall distribution of cancers nor the possibility that some states of differentiation may be intrinsically less stable than others to the effects of random mutation, a possibility predicted on purely theoretical grounds many years ago. This brief report describes an overall pattern to human organ-specific cancer incidence data and shows that organ-specific cancer rates correlate negatively with an organ's evolutionary antiquity. Although the relationship may just be coincidental, it suggests the possibility that recently-evolved differentiation states may be intricnsically more vulnerable to neoplastic change. Extrapolation of the regression line to a cancer incidence of zero equates to a level of tissue organization typical of 660 Myr ago; the inferred beginning of neoplasia therefore coincides with the rise of complex multicellular animals.

The utility of diagnostic biopsy specimens for predictive molecular testing in colorectal cancer

AIMS

If stratified medicine is to be applied in the neoadjuvant setting, predictive testing will have to be undertaken on preoperative diagnostic biopsy specimens. The aim of this study was to evaluate whether a diagnostic biopsy was adequately representative of the main tumour in colorectal cancer.

METHODS AND RESULTS

Thirty cases of paired biopsy and subsequent resection specimens were randomly selected. Samples were screened for mutation in KRAS (codons 12/13, 61, and 146), BRAF (codon 600 and exon 11), PIK3CA (exons 1, 9, and 20), TP53 (exons 5-8), and microsatellite instability, using the quick multiplex consensus or standard polymerase chain reaction (PCR) protocols followed by high-resolution melting analysis. A total of 570 paired PCR tests were performed for mutation detection, and identical results were obtained in both biopsy and resection specimens in 569 tests (>99% concordance). Four cases (13%) showed microsatellite instability, and, in all four cases, instability was seen at identical mononucleotide markers in both biopsy and matched resection specimens.

CONCLUSIONS

This is the first study to show that diagnostic biopsy specimens, even though they are a tiny sample of the tumour, are sufficiently representative for use in predictive testing for early driver mutations in colorectal cancer.

Wnt signalling pathway parameters for mammalian cells

Wnt/β-catenin signalling regulates cell fate, survival, proliferation and differentiation at many stages of mammalian development and pathology. Mutations of two key proteins in the pathway, APC and β-catenin, have been implicated in a range of cancers, including colorectal cancer. Activation of Wnt signalling has been associated with the stabilization and nuclear accumulation of β-catenin and consequential up-regulation of β-catenin/TCF gene transcription. In 2003, Lee et al. constructed a computational model of Wnt signalling supported by experimental data from analysis of time-dependent concentration of Wnt signalling proteins in Xenopus egg extracts. Subsequent studies have used the Xenopus quantitative data to infer Wnt pathway dynamics in other systems. As a basis for understanding Wnt signalling in mammalian cells, a confocal live cell imaging measurement technique is developed to measure the cell and nuclear volumes of MDCK, HEK293T cells and 3 human colorectal cancer cell lines and the concentrations of Wnt signalling proteins β-catenin, Axin, APC, GSK3β and E-cadherin. These parameters provide the basis for formulating Wnt signalling models for kidney/intestinal epithelial mammalian cells. There are significant differences in concentrations of key proteins between Xenopus extracts and mammalian whole cell lysates. Higher concentrations of Axin and lower concentrations of APC are present in mammalian cells. Axin concentrations are greater than APC in kidney epithelial cells, whereas in intestinal epithelial cells the APC concentration is higher than Axin. Computational simulations based on Lee's model, with this new data, suggest a need for a recalibration of the model.A quantitative understanding of Wnt signalling in mammalian cells, in particular human colorectal cancers requires a detailed understanding of the concentrations of key protein complexes over time. Simulations of Wnt signalling in mammalian cells can be initiated with the parameters measured in this report.

Wnt signalling pathway parameters for mammalian cells

Wnt/β-catenin signalling regulates cell fate, survival, proliferation and differentiation at many stages of mammalian development and pathology. Mutations of two key proteins in the pathway, APC and β-catenin, have been implicated in a range of cancers, including colorectal cancer. Activation of Wnt signalling has been associated with the stabilization and nuclear accumulation of β-catenin and consequential up-regulation of β-catenin/TCF gene transcription. In 2003, Lee et al. constructed a computational model of Wnt signalling supported by experimental data from analysis of time-dependent concentration of Wnt signalling proteins in Xenopus egg extracts. Subsequent studies have used the Xenopus quantitative data to infer Wnt pathway dynamics in other systems. As a basis for understanding Wnt signalling in mammalian cells, a confocal live cell imaging measurement technique is developed to measure the cell and nuclear volumes of MDCK, HEK293T cells and 3 human colorectal cancer cell lines and the concentrations of Wnt signalling proteins β-catenin, Axin, APC, GSK3β and E-cadherin. These parameters provide the basis for formulating Wnt signalling models for kidney/intestinal epithelial mammalian cells. There are significant differences in concentrations of key proteins between Xenopus extracts and mammalian whole cell lysates. Higher concentrations of Axin and lower concentrations of APC are present in mammalian cells. Axin concentrations are greater than APC in kidney epithelial cells, whereas in intestinal epithelial cells the APC concentration is higher than Axin. Computational simulations based on Lee's model, with this new data, suggest a need for a recalibration of the model.A quantitative understanding of Wnt signalling in mammalian cells, in particular human colorectal cancers requires a detailed understanding of the concentrations of key protein complexes over time. Simulations of Wnt signalling in mammalian cells can be initiated with the parameters measured in this report.

Cancer biomarkers: selecting the right drug for the right patient

This Perspective highlights biomarkers that are expressed as a consequence of cancer development and progression. We focus on those biomarkers that are most relevant for identifying patients who are likely to respond to a given therapy, as well as those biomarkers that are most effective for measuring patient response to therapy. These two measures are necessary for selecting the right drug for the right patient, regardless of whether the setting is in drug development or in the post-approval use of the drug for patients with cancer. We also discuss the innovative designs of clinical trials and methodologies that are used to validate and qualify biomarkers for use in specific contexts. Furthermore, we look ahead to the promises and challenges in the field of cancer biomarkers.

Polycyclic aromatic hydrocarbons and digestive tract cancers: a perspective

Cancers of the colon are most common in the Western world. In majority of these cases, there is no familial history and sporadic gene damage seems to play an important role in the development of tumors in the colon. Studies have shown that environmental factors, especially diet, play an important role in susceptibility to gastrointestinal (GI) tract cancers. Consequently, environmental chemicals that contaminate food or diet during preparation become important in the development of GI cancers. Polycyclic aromatic hydrocarbons (PAHs) are one such family of ubiquitous environmental toxicants. These pollutants enter the human body through consumption of contaminated food, drinking water, inhalation of cigarette smoke, automobile exhausts, and contaminated air from occupational settings. Among these pathways, dietary intake of PAHs constitutes a major source of exposure in humans. Although many reviews and books on PAHs and their ability to cause toxicity and breast or lung cancer have been published, aspects on contribution of diet, smoking and other factors toward development of digestive tract cancers, and strategies to assess risk from exposure to PAHs have received much less attention. This review, therefore, focuses on dietary intake of PAHs in humans, animal models, and cell cultures used for GI cancer studies along with epidemiological findings. Bioavailability and biotransformation processes, which influence the disposition of PAHs in body and the underlying causative mechanisms of GI cancers, are also discussed. The existing data gaps and scope for future studies is also emphasized. This information is expected to stimulate research on mechanisms of sporadic GI cancers caused by exposure to environmental carcinogens.

Identification of MAGI1 as a tumor-suppressor protein induced by cyclooxygenase-2 inhibitors in colorectal cancer cells

Cyclooxyganase-2 (COX-2), a rate-limiting enzyme in the prostaglandin synthesis pathway, is overexpressed in many cancers and contributes to cancer progression through tumor cell-autonomous and paracrine effects. Regular use of non-steroidal anti-inflammatory drugs or selective COX-2 inhibitors (COXIBs) reduces the risk of cancer development and progression, in particular of the colon. The COXIB celecoxib is approved for adjunct therapy in patients with Familial adenomatous polyposis at high risk for colorectal cancer (CRC) formation. Long-term use of COXIBs, however, is associated with potentially severe cardiovascular complications, which hampers their broader use as preventive anticancer agents. In an effort to better understand the tumor-suppressive mechanisms of COXIBs, we identified MAGUK with Inverted domain structure-1 (MAGI1), a scaffolding protein implicated in the stabilization of adherens junctions, as a gene upregulated by COXIB in CRC cells and acting as tumor suppressor. Overexpression of MAGI1 in CRC cell lines SW480 and HCT116 induced an epithelial-like morphology; stabilized E-cadherin and β-catenin localization at cell-cell junctions; enhanced actin stress fiber and focal adhesion formation; increased cell adhesion to matrix proteins and suppressed Wnt signaling, anchorage-independent growth, migration and invasion in vitro. Conversely, MAGI1 silencing decreased E-cadherin and β-catenin localization at cell-cell junctions; disrupted actin stress fiber and focal adhesion formation; and enhanced Wnt signaling, anchorage-independent growth, migration and invasion in vitro. MAGI1 overexpression suppressed SW480 and HCT116 subcutaneous primary tumor growth, attenuated primary tumor growth and spontaneous lung metastasis in an orthotopic model of CRC, and decreased the number and size of metastatic nodules in an experimental model of lung metastasis. Collectively, these results identify MAG1 as a COXIB-induced inhibitor of the Wnt/β-catenin signaling pathway, with tumor-suppressive and anti-metastatic activity in experimental colon cancer.

NGAL expression is elevated in both colorectal adenoma-carcinoma sequence and cancer progression and enhances tumorigenesis in xenograft mouse models

PURPOSE

There is growing evidence implicating that neutrophil gelatinase-associated lipocalin (NGAL) plays a role in the development and progression of cancers. However, the effect of NGAL in colorectal carcinoma (CRC) has not been clearly elucidated. In this study, we investigated the role of NGAL in the tumorigenesis and progression of CRC and evaluated the clinical value of NGAL expression.

EXPERIMENTAL DESIGN

We examined NGAL expression in 526 colorectal tissue samples, including 53 sets of matched specimens (histologically normal mucosa, adenomas, and carcinomas) using immunohistochemical analysis. In CRCs, correlations between NGAL expression and clinicopathologic parameters were analyzed, and survival analysis was conducted. The role of NGAL was further tested using mouse xenograft models.

RESULTS

NGAL expression was elevated during the colorectal adenoma-carcinoma sequence both among the 526 cases (r(s) = 0.66, P < 0.001) and in the 53 sets of matched specimens (r(s) = 0.60, P < 0.001). In CRCs, NGAL expression was associated with cancer stage (P = 0.041) and tumor recurrence in stage II patients (P = 0.037). Survival analysis revealed that NGAL expression was an independent prognostic factor for overall survival (HR = 1.84, P = 0.004) and for disease-free survival of stage II patients (HR = 5.88, P = 0.021). In mouse models, the xenografts in cecum and spleen were heavier and more numerous in the group injected with NGAL-overexpressing CRC cells (P < 0.05).

CONCLUSIONS

NGAL overexpression may promote the tumorigenesis and progression of CRC. Detecting NGAL expression in tumor tissues may be useful for evaluating prognosis of patients with CRC.

Specific variants in the MLH1 gene region may drive DNA methylation, loss of protein expression, and MSI-H colorectal cancer

BACKGROUND

We previously identified an association between a mismatch repair gene, MLH1, promoter SNP (rs1800734) and microsatellite unstable (MSI-H) colorectal cancers (CRCs) in two samples. The current study expanded on this finding as we explored the genetic basis of DNA methylation in this region of chromosome 3. We hypothesized that specific polymorphisms in the MLH1 gene region predispose it to DNA methylation, resulting in the loss of MLH1 gene expression, mismatch-repair function, and consequently to genome-wide microsatellite instability.

METHODOLOGY/PRINCIPAL FINDINGS

We first tested our hypothesis in one sample from Ontario (901 cases, 1,097 controls) and replicated major findings in two additional samples from Newfoundland and Labrador (479 cases, 336 controls) and from Seattle (591 cases, 629 controls). Logistic regression was used to test for association between SNPs in the region of MLH1 and CRC, MSI-H CRC, MLH1 gene expression in CRC, and DNA methylation in CRC. The association between rs1800734 and MSI-H CRCs, previously reported in Ontario and Newfoundland, was replicated in the Seattle sample. Two additional SNPs, in strong linkage disequilibrium with rs1800734, showed strong associations with MLH1 promoter methylation, loss of MLH1 protein, and MSI-H CRC in all three samples. The logistic regression model of MSI-H CRC that included MLH1-promoter-methylation status and MLH1 immunohistochemistry status fit most parsimoniously in all three samples combined. When rs1800734 was added to this model, its effect was not statistically significant (P-value  = 0.72 vs. 2.3×10(-4) when the SNP was examined alone).

CONCLUSIONS/SIGNIFICANCE

The observed association of rs1800734 with MSI-H CRC occurs through its effect on the MLH1 promoter methylation, MLH1 IHC deficiency, or both.

Comparative analysis of pyrosequencing and QMC-PCR in conjunction with high resolution melting for KRAS/BRAF mutation detection

Mutation detection is important in cancer management. Several methods are available of which high resolution melting (HRM) analysis and pyrosequencing are the most versatile. We undertook a comparative analysis of these techniques. The methods are: To compare the limit of detection (LOD), mutations in KRAS (codon 12/13 hotspot) and BRAF (V600E hotspot) were tested. DNA mixtures containing mutant alleles at a frequency of around 25%/12.5%/6%/3%/ 1.5%/0.8% were analysed. To compare frequency of mutation detection, 22 DNA samples (nine high quality samples from cell lines, 13 low quality samples from formalin-fixed paraffin-embedded tissue) were tested for three hotspots in KRAS (codons 12/13, 61 and 146) and two hotspots in BRAF (V600E and exon 11). HRM analysis of KRAS (codon12/13) and BRAF (V600E) showed that 3% and 1.5% mutant alleles respectively could be reliably detected whilst pyrosequencing reliably detected 6% mutant alleles in each case. Of 110 tests performed on 22 DNA samples, in 109 cases HRM and pyrosequencing gave identical results. Two of the samples tested had previously been called as wild type for KRAS by direct Sanger sequencing but were found to be mutant by both HRM and pyrosequencing. Both HRM and pyrosequencing can detect small numbers of mutant alleles although HRM has a lower limit of detection. Both are suitable for use in mutation detection and are both more sensitive than Sanger sequencing.

Detection of metabolic alterations in non-tumor gastrointestinal tissue of the Apc(Min/+) mouse by (1)H MAS NMR spectroscopy

In this study, we have used metabolic profiling (metabolomics/metabonomics) via high resolution magic angle spinning (HRMAS) and solution state (1)H NMR spectroscopy to characterize small bowel and colon tissue from the Apc(Min/+) mouse model of early gastrointestinal (GI) tumorigenesis. Multivariate analysis indicated the presence of metabolic differences between the morphologically normal/non-tumor tissue from approximately 10 week-old Apc(Min/+) mice and their wild-type litter mates. The metabolic profile of isolated lamina propria and epithelial cells from the same groups could also be discriminated on the basis of genotype. Accounting for systematic variation in individual metabolite levels across different anatomical regions of the lower GI tract, the metabolic phenotype of Apc(Min/+) lamina propria tissue was defined by significant increases in the phosphocholine/glycerophosphocholine ratio (PC/GPC, +21%) and decreases in GPC (-25%) and the gut-microbial cometabolite dimethylamine (DMA, -40%) relative to wild type. In the whole tissue, elevated lactate (+15%) and myo-inositol (+19%) levels were detected. As the metabolic changes occurred in non-tumor tissue from animals of very low tumor burden (<2 polyps/animal), they are likely to represent the specific consequence of reduced Apc function and very early events in tumorigenesis. The observed increase in PC/GPC ratio has been previously reported with immortalisation and malignant transformation of cells and is consistent with the role of Apc as a tumor suppressor. Phospholipase A2, which hydrolyses phosphatidylcholine to Acyl-GPC, is a known modifier gene of the model phenotype (Mom1), and altered expression of choline phospholipid enzymes has been reported in gut tissue from Apc(Min/+) mice. These results indicate the presence of a metabolic phenotype associated with "field cancerization", highlighting potential biomarkers for monitoring disease progression, for early evaluation of response to chemoprevention, and for predicting the severity of the polyposis phenotype in the Apc(Min/+) model.

C-terminal Tensin-like (CTEN) is an oncogene which alters cell motility possibly through repression of E-cadherin in colorectal cancer

The Tensin gene family encodes proteins thought to modulate integrin function. C-terminal Tensin-like (CTEN) is a member of the Tensin gene family which lacks the N-terminus actin-binding domain. Cten is reported to have both oncogenic and tumour-suppressor functions. We investigated the role that Cten may play in colorectal cancer (CRC). By quantitative RT-PCR CTEN is up-regulated (i.e. > two-fold increase) in 62% of cell lines and 69% of tumours compared with normal mucosa, consistent with CTEN being a possible oncogene. Stable transfection of HCT116 and SW480 (CRC cell lines with low endogenous Cten expression) with a Cten expression vector gave identical results in both cell lines. Forced Cten expression did not cause change in cell numbers, although it did confer resistance to staurosporine-induced apoptosis (p < 0.005). Cten also induced epithelial-mesenchymal transition (EMT) in tumour cells accompanied by a significant increase in both cell migration (transwell migration and cell wounding assays, p < 0.001 and p < 0.05, respectively) and cell invasion (invasion through Matrigel, p < 0.001). Given the observed EMT, we investigated the levels of E-cadherin. Cten induction was associated with a reduction in E-cadherin protein expression but not levels of E-cadherin mRNA. These data suggest that CTEN is an oncogene in CRC which stimulates EMT, cell migration and invasion and may therefore have a role in tumour invasion/spread. Furthermore, Cten induction is associated with post-transcriptional repression of E-cadherin.

Cadherin-bound beta-catenin feeds into the Wnt pathway upon adherens junctions dissociation: evidence for an intersection between beta-catenin pools

β-catenin is an essential component of two cellular systems: cadherin-based adherens junctions (AJ) and the Wnt signaling pathway. A functional or physical connection between these β-catenin pools has been suggested in previous studies, but not conclusively demonstrated to date. To further examine this intersection, we treated A431 cell colonies with lysophosphatidic acid (LPA), which forces rapid and synchronized dissociation of AJ. A combination of immunostaining, time-lapse microscopy using photoactivatable-GFP-tagged β-catenin, and image analyses indicate that the cadherin-bound pool of β-catenin, internalized together with E-cadherin, accumulates at the perinuclear endocytic recycling compartment (ERC) upon AJ dissociation, and can be translocated into the cell nucleus upon Wnt pathway activation. These results suggest that the ERC may be a site of residence for β-catenin destined to enter the nucleus, and that dissociation of AJ may influence β-catenin levels in the ERC, effectively affecting β-catenin substrate levels available downstream for the Wnt pathway. This intersection provides a mechanism for integrating cell-cell adhesion with Wnt signaling and could be critical in developmental and cancer processes that rely on β-catenin-dependent gene expression.