Meta association of colorectal cancer confirms risk alleles at 8q24 and 18q21.

BACKGROUND: Genome-wide association studies of colorectal cancer (CRC) have identified genetic variants that reproducibly associate with CRC. Associations of 12 single nucleotide polymorphisms at 8q24, 9p24, and 18q21 (SMAD7) and CRC were investigated in a three-center collaborative study including two U.K. case-control cohorts (Sheffield and Leeds) and a U.S. case-control study of CRC cases from high-risk Utah pedigrees. METHODS: Our combined resource included 1,092 CRC case subjects and 1,060 age- and sex-matched controls. Meta statistics and Monte Carlo significance testing using Genie software provided a valid combined analysis of our mixed independent and related case-control resource. We also evaluated whether these associations differed by sex, age at diagnosis, family history, or tumor site. RESULTS: At 8q24, we observed two independent significant associations at single nucleotide polymorphisms located in two different risk regions of 8q24: rs6983267 in region 3 [P(trend) = 0.01; per allele odds ratio (OR), 1.17; 95% confidence intervals (95% CI), 1.03-1.32] and rs10090154 in region 5 (P(trend) = 0.05; per allele OR, 1.24; 95% CI, 1.01-1.51). At 18q21, associations were observed in distal colon tumors but not in proximal or rectal cancers: rs4939827 (P(trend) = 0.007; per allele OR, 0.77; 95% CI, 0.64-0.93; case-case p(diff) = 0.03) and rs12953717 (P(trend) = 0.01; per allele OR, 1.27; 95% CI, 1.06-1.52). We were unable to detect any associations at 9p24 with CRC. CONCLUSIONS: Our investigation confirms that variants across multiple risk regions of 8q24 are associated with CRC, and that associations at 18q21 differ by tumor site.

MLH1 -93G>A promoter polymorphism and risk of mismatch repair deficient colorectal cancer.

Rare inherited mutations in the mutL homolog 1 (MLH1) DNA mismatch repair gene can confer an increased susceptibility to colorectal cancer (CRC) with high penetrance where disease frequently develops in the proximal colon. The core promoter of MLH1 contains a common single nucleotide polymorphism (SNP) (-93G>A, dbSNP ID:rs1800734) located in a region essential for maximum transcriptional activity. We used logistic regression analysis to examine the association between this variant and risk of CRC in patients in the United Kingdom. All statistical tests were 2 sided. In an analysis of 1,518 patients with CRC, homozygosity for the MLH1 -93A variant was associated with a significantly increased 3-fold risk of CRC negative for MLH1 protein by immunohistochemistry (odds ratio (OR): AA vs GG = 3.30, 95% CI 1.46-7.47, n = 1392, p = 0.004, MLH1 negative vs MLH1 positive CRC) and with a 68% excess of proximal CRC (OR: AA vs GG=1.68, 95% confidence interval (CI) 1.00-2.83, n = 1,518, p = 0.05, proximal vs distal CRC). These findings suggest that the MLH1 -93G>A polymorphism defines a low penetrance risk allele for CRC.

Acute rectal ischaemia following emergency abdominal aortic aneurysm surgery.

We present a case of isolated rectal ischaemia, a rare complication after emergency surgery for a ruptured abdominal aneurysm. We discuss the possible aetiology of this condition and how this rare condition may be missed unless care is taken at the time of reoperation.

Identification of candidate driver genes in common focal chromosomal aberrations of microsatellite stable colorectal cancer.

Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide. Chromosomal instability (CIN) is a major driving force of microsatellite stable (MSS) sporadic CRC. CIN tumours are characterised by a large number of somatic chromosomal copy number aberrations (SCNA) that frequently affect oncogenes and tumour suppressor genes. The main aim of this work was to identify novel candidate CRC driver genes affected by recurrent and focal SCNA. High resolution genome-wide comparative genome hybridisation (CGH) arrays were used to compare tumour and normal DNA for 53 sporadic CRC cases. Context corrected common aberration (COCA) analysis and custom algorithms identified 64 deletions and 32 gains of focal minimal common regions (FMCR) at high frequency (>10%). Comparison of these FMCR with published genomic profiles from CRC revealed common overlap (42.2% of deletions and 34.4% of copy gains). Pathway analysis showed that apoptosis and p53 signalling pathways were commonly affected by deleted FMCR, and MAPK and potassium channel pathways by gains of FMCR. Candidate tumour suppressor genes in deleted FMCR included RASSF3, IFNAR1, IFNAR2 and NFKBIA and candidate oncogenes in gained FMCR included PRDM16, TNS1, RPA3 and KCNMA1. In conclusion, this study confirms some previously identified aberrations in MSS CRC and provides in silico evidence for some novel candidate driver genes.

Genetic variants in XRCC2: new insights into colorectal cancer tumorigenesis.

Polymorphisms in DNA double-strand break repair gene XRCC2 may play an important role in colorectal cancer etiology, specifically in disease subtypes. Associations of XRCC2 variants and colorectal cancer were investigated by tumor site and tumor instability status in a four-center collaboration including three U.K. case-control studies (Sheffield, Leeds, and Dundee) and a U.S. case-control study of cases from high-risk Utah pedigrees (total: 1,252 cases and 1,422 controls). The 14 variants studied were tagging single nucleotide polymorphisms (SNP) selected from National Institute of Environmental Health Sciences/HapMap data supplemented with SNPs identified from sequencing of 125 cases chosen to represent multiple colorectal cancer groups (familial, metastatic disease, and tumor subsite). Monte Carlo significance testing using Genie software provided valid meta-analyses of the total resource that includes family-based data. Similar to reports of colorectal cancer and other cancer sites, the rs3218536 R188H allele was not associated with increased risk. However, we observed a novel, highly significant association of a common SNP, rs3218499G>C, with increased risk of rectal tumors (odds ratio, 2.1; 95% confidence interval, 1.3-3.3; P(chi2) = 0.0006) versus controls, with the largest risk found for female rectal cases (odds ratio, 3.1; 95% confidence interval, 1.6-6.1; P(chi2) = 0.0006). This difference was significantly different to that for proximal and distal colon cancers (P(chi2) = 0.02). Our investigation supports a role for XRCC2 in colorectal cancer tumorigenesis, conferring susceptibility to rectal tumors.

Association of adult celiac disease with surgical abdominal pain: a case-control study in patients referred to secondary care.

BACKGROUND: Acute abdominal pain is the most common indication for surgical admission. Nonspecific abdominal pain (NSAP) may account for up to 40% of cases. There has been no published prospective study in which adult patients presenting with acute abdominal pain are investigated for celiac disease. AIMS: We aimed to assess the association of celiac disease with surgical abdominal pain. PATIENTS AND METHODS: A case-control study was undertaken involving 300 consecutive new unselected patients presenting with acute abdominal pain (in a university hospital) and healthy controls (age and sex matched) without abdominal pain (n = 300). Initial investigations for celiac disease were immunoglobulins, IgA/IgG anti-gliadin (AGA), and endomysial antibodies (EMA). Any patient with a positive IgA AGA, EMA, or only IgG AGA in the presence of IgA deficiency was offered a small bowel biopsy to confirm the diagnosis. RESULTS: : There were 33 patients with abdominal pain who had positive antibodies, of whom 9 had histologically confirmed celiac disease (6 EMA positive; 3 EMA negative). One antibody positive patient (EMA in isolation) declined duodenal biopsy and the remaining 23 had normal duodenal mucosa. Within the control group, there were 2 cases of celiac disease. Compared with matched controls the association of acute abdominal pain with celiac disease gave an odds ratio 4.6. (P = 0.068, 95% confidence interval, 1.11-19.05). When only considering NSAP the prevalence of celiac disease was highly significant at 10.5% (9 of 86, P = 0.006). Patients' symptoms improved on a gluten-free diet at 12- to 18-month follow-up. CONCLUSION: Celiac disease was diagnosed in 3% of patients who presented with unselected acute abdominal pain to secondary care. Targeting patients who have NSAP or celiac associated symptoms/diseases may improve the diagnostic yield.