Muti Abulafi

Whole-genome methylation analysis of benign and malignant colorectal tumours

Changes in DNA methylation, whether hypo‐ or hypermethylation, have been shown to be associated with the progression of colorectal cancer. Methylation changes substantially in the progression from normal mucosa to adenoma and to carcinoma. This phenomenon has not been studied extensively and studies have been restricted to individual CpG islands, rather than taking a whole‐genome approach. We aimed to study genome‐wide methylation changes in colorectal cancer. We obtained 10 fresh‐frozen normal tissue–cancer sample pairs, and five fresh‐frozen adenoma samples. These were run on the lllumina HumanMethylation27 whole‐genome methylation analysis system. Differential methylation between normal tissue, adenoma and carcinoma was analysed using Bayesian regression modelling, gene set enrichment analysis (GSEA) and hierarchical clustering (HC). The highest‐rated individual gene for differential methylation in carcinomas versus normal tissue and adenomas versus normal tissue was GRASP (padjustedu2009=u20091.59 × 10–5, BF = 12.62, padjustedu2009=u20091.68 × 10–6, BF = 14.53). The highest‐rated gene when comparing carcinomas versus adenomas was ATM (padjustedu2009=u20092.0 × 10–4, BF = 10.17). Hierarchical clustering demonstrated poor clustering by the CIMP criteria for methylation. GSEA demonstrated methylation changes in the Netrin–DCC and SLIT–ROBO pathways. Widespread changes in DNA methylation are seen in the transition from adenoma to carcinoma. The finding that GRASP, which encodes the general receptor for phosphoinositide 1‐associated scaffold protein, was differentially methylated in colorectal cancer is interesting. This may be a potential biomarker for colorectal cancer. Copyright

Adverse Features on Rectal MRI Identify a High-risk Group that May Benefit from More Intensive Preoperative Staging and Treatment

BackgroundMagnetic resonance imaging (MRI) is highly accurate in local staging of rectal cancer. It can identify features known to be associated with increased risk of metastatic disease. We evaluated the incidence of synchronous metastatic disease on fludeoxyglucose–positron emission tomography/computed tomography (FDG-PET/CT) and contrast-enhanced multiple-row detector computed tomography (ceMDCT) in MRI-stratified high- and low-risk rectal cancers. The aim was to determine the incidence of synchronous metastatic disease according to MRI risk features.MethodsA total of 236 patients with rectal cancer were recruited to a study evaluating FDG-PET/CT. All patients underwent MRI staging and were stratified into high and low risk (high risk: extramural venous invasion, extramural spread of >5xa0mm or T4, involved circumferential resection margin or intersphincteric plane involved for low rectal tumors). Confirmed metastases were those identified on FDG-PET/CT and ceMDCT.ResultsImaging data were available for 230 (97.5%) of 236 patients. Incidence of confirmed distant metastases was significantly greater in the MRI high-risk group, with 28 (20.7%) of 135 (95% confidence interval [CI] 14.8–28.3), versus the low-risk group, with 4 (4.2%) of 95 (95% CI 1.7–10.3) (odds ratio 6.0, 95% CI 2.0–17.6, Pxa0<xa00.001).ConclusionsAdverse features found on rectal MRI identify patients at increased risk of synchronous metastatic disease. This group may benefit from additional preoperative investigation for synchronous metastases such as FDG-PET/CT or liver MRI and from alternative neoadjuvant chemotherapy regimens including induction chemotherapy.

A study of genomic instability in early preneoplastic colonic lesions

It is difficult to explain the differential rates of progression of premalignant colonic lesions and differences in behaviour of morphologically similar lesions. Heterogeneity for microsatellite instability (MSI) and promoter methylation in driving these phenomena forward may explain this; however, no previous analysis has examined this in detail at the gland level, the smallest unit of colorectal premalignant lesions. We aimed to carry out an analysis of gland level genomic instability for MSI and promoter methylation. MSI occurred significantly more frequently (20%) in colonic glands than has previously been observed in whole colorectal polyps. Significant promoter methylation was seen in MLH1, PMS2, MLH3 and MSH3 as well as significant heterogeneity for both MSI and promoter methylation. Methylation and MSI may have a significant role in driving forward colorectal carcinogenesis, although in the case of MSI, this association is less clear as it occurs significantly more frequently than previously thought, and may simply be a passenger in the adenoma-carcinoma sequence. Promoter methylation in MLH1, MLH3, MSH3 and PMS2 was also found to be significantly associated with MSI and should be investigated further. A total of 273 colorectal glands (126 hyperplastic, 147 adenomatous) were isolated via laser capture microdissection (targeted at regions of MLH1 loss) from 93 colonic polyps and tested for MSI, and promoter methylation of the DNA mismatch repair genes MLH1, MSH2, MLH3, MSH6, PMS2, MGMT and MLH3 via methylation specific multiplex ligation-dependent probe amplification. Logistic regression modelling was then used to identify significant associations between promoter methylation and gland histological type and MSI status.

Local staging and assessment of colon cancer with 1.5-T magnetic resonance imaging

OBJECTIVE:nThe aim of this study was to assess the accuracy of 1.5-T MRI in the pre-operative local T and N staging of colon cancer and identification of extramural vascular invasion (EMVI).nnnMETHODS:nBetween 2010 and 2012, 60 patients with adenocarcinoma of the colon were prospectively recruited at 2 centres. 55 patients were included for final analysis. Patients received pre-operative 1.5-T MRI with high-resolution T2 weighted, gadolinium-enhanced T1 weighted and diffusion-weighted images. These were blindly assessed by two expert radiologists. Accuracy of the T-stage, N-stage and EMVI assessment was evaluated using post-operative histology as the gold standard.nnnRESULTS:nResults are reported for two readers. Identification of T3 disease demonstrated an accuracy of 71% and 51%, sensitivity of 74% and 42% and specificity of 74% and 83%. Identification of N1 disease demonstrated an accuracy of 57% for both readers, sensitivity of 26% and 35% and specificity of 81% and 74%. Identification of EMVI demonstrated an accuracy of 74% and 69%, sensitivity 63% and 26% and specificity 80% and 91%.nnnCONCLUSION:n1.5-T MRI achieved a moderate accuracy in the local evaluation of colon cancer, but cannot be recommended to replace CT on the basis of this study.nnnADVANCES IN KNOWLEDGE:nThis study confirms that MRI is a viable alternative to CT for the local assessment of colon cancer, but this study does not reproduce the very high accuracy reported in the only other study to assess the accuracy of MRI in colon cancer staging.

The rectosigmoid problem

The lack of consensus over the transition point for the end of the sigmoid and beginning of the rectum is a problem for the colorectal multidisciplinary team. In this review, we survey the wide number of landmarks for the rectosigmoid junction, and describe the theoretical and evidence-based strengths and weaknesses of each one. Without a reliable definition of the rectum, sigmoid and rectal cancers will be classified inconsistently. As the treatment strategies for sigmoid and rectal cancers are radically different, incorrect tumour localisation has a substantial impact on patient management, leading to under or over treatment. Inconsistent classification will confound investigation of metastatic patterns and treatment outcomes. Now that the rectosigmoid junction has been recognised as a distinct segment of colon by the International Classification of Diseases, further heterogeneity in management and outcomes could result to the detriment of patients and research. We describe a bespoke, anatomical and reliable landmark for the rectosigmoid junction; the sigmoid take-off.

Meta-Analysis of Oncological Outcomes of Sigmoid Cancers: A Hidden Epidemic of R1 “Palliative” Resections

BACKGROUNDnColon cancer outcomes are now inferior to rectal cancer outcomes. The sigmoid colon is the most common site of colonic cancer. The aim of this review was to investigate the oncological outcomes for sigmoid cancer.nnnMETHODSnA systematic review and meta-analysis was performed. We included any study of the oncological outcomes for sigmoid cancer such as local recurrence, distant recurrence and disease free survival. A systematic search was conducted in Medline from inception to November 2016. Study quality was evaluated with the Newcastle-Ottawa Scale. The study was registered on PROSPERO (CRD42017069326).nnnRESULTSnThe search terms returned 1323 results. We identified a total of 17 eligible studies including 5953 patients. The pooled local recurrence rate was 10.5% in 15 studies with 5148 patients (95% CI 0.07-0.14) and heterogeneity measured by I2 was 94%. The pooled distant recurrence rate was 19.5% (7 studies, 2040 patients, 95% CI (0.14-0.25), I2 90%). The pooled disease free survival at 5 years was 80.4% (5 studies, 2336 patients, 95% CI 78.6%-82.1%, I2 11.5%.). The median Newcastle-Ottawa score was 4 out of 9. R1 and R2 resections were excluded or not described in 16/17 studies. Two studies described R1 and R2 rates of 15-20%.nnnCONCLUSIONnThe pooled local recurrence rate of sigmoid cancer of 10.5% is higher than contemporary rates of local recurrence of rectal cancer. A large number of papers fail to describe or include R1 resections of sigmoid cancer, which are frequently described as palliative.

Variation in landmarks for the rectum: an MRI study

This study aimed to assess the reliability of measurements and bony landmarks for the rectosigmoid junction on MRI.

The DCC gene and colorectal cancer: the story is more complex

Dear Sir, The recent correspondence by Biyani et al. [1] is a thorough discussion of the recent hypothesis that carcinogenesis can occur in hyperplastic colonic polyps. However, the ‘Deleted in Colorectal Carcinoma’ (DCC) gene, which they refer, has not been definitively proved to be involved in the initiation of colorectal carcinogenesis. Mutations in the DCC gene were thought to be involved in this process [2], because 18q allelic loss was very frequently seen in colorectal carcinoma. Later studies identified this gene as being located at 18q21.3. Further analysis showed the DCC gene actually coded for a component of the receptor complex that mediated the effects of netrin-1, a molecule involved in axon guidance [3], which seemed an unlikely function for this role. In a study of 57 colorectal cancers, it was found that there were almost never any mutations in the DCC gene in human colorectal tumours showing 18q allelic loss [4]. Mouse knockout models of adenomatous polyposis coli (APC) ⁄ DCC have shown that loss of the DCC gene in mice that have adenomas initiated by APC loss causes a bias towards highly dysplastic adenomas [5]. The DCC gene possesses pro-apoptotic activity, thought to be because of cleavage by a capsase (cysteine protease) exposing a pro-apoptotic domain on the DCC receptor, which is inhibited by netrin-1. Over-expression of netrin-1 in mouse models, coupled with loss of the APC gene has been shown to suppress pro-apoptotic activity and is postulated to promote carcinogenesis [5]. However, studies of human colorectal cancers [5] have shown that only 7% of colorectal cancers have overexpression of netrin-1, implying that loss of the DCC receptor complex by 18q allelic loss or direct mutation may not confer the same selective advantage towards human colorectal cancer cells. Characterization and identification of other tumour suppressor genes in the region of 18q21 revealed two candidate genes, namely SMAD2 and SMAD4. The protein product of the SMAD4 gene encodes for intracellular mediators of the transforming growth factor (TGF)-b pathway [6,7]. The TGF-b pathway acts as a tumour suppressor pathway in normal colonic epithelium, as proved by inactivation studies in knock-out mice [8] and the SMAD2 and SMAD4 genes have been found to be mutated in colorectal cancer [9]. In conclusion, the DCC gene may play a role in the development and metastasis of colorectal cancer, although its role in initiation is still unclear.