A feasibility study of perioperative vitamin D supplementation in patients undergoing colorectal cancer resection

Background

Vitamin D supplementation improves colorectal cancer (CRC) survival outcomes in randomized trials. The aim of this study was to test the feasibility, safety and efficacy of vitamin D supplementation in the pre- and perioperative period in patients undergoing CRC surgery.

Methods

Patients were given 3200IU oral cholecalciferol (D3) per day perioperatively. Serial serum 25-hydroxyvitamin (25OHD) was measured by liquid chromatography tandem mass spectrometry and compared to untreated CRC controls. 25OHD and C-reactive protein (CRP) levels were compared using adjusted generalized linear mixed-effects models.

Results

A total of 122 patients underwent serial perioperative sampling, including 41 patients given high-dose perioperative supplementation. Supplementation was well-tolerated with no adverse or serious adverse events related to supplementation reported. Pre-operative supplementation increased 25OHD levels on the day of surgery (103.9 vs. 42.5 nmol/l, P = 8.2E-12). Supplementation increased 25OHD levels at all post-operative timepoints (P < 0.001) and attenuated the post-operative drop in 25OHD (46 vs. 24% drop, P = 3.0E-4). Rate of vitamin D peri-operative insufficiency was significantly less in those on supplementation (e.g., day 3-5, 14 vs. 84%, P = 1.41E-08), with multivariate modeling across all timepoints indicating a ∼59 nmol/l higher 25OHD compared to control patients (P = 3.7E-21). Post-operative CRP was lower in patients taking supplementation (e.g., day 3-5 timepoint; 129 vs. 81 mg/l, P = 0.04).

Conclusion

High dose pre-operative vitamin D supplementation is associated with higher perioperative 25OHD levels, lower rates of vitamin D insufficiency and reduced early post-operative CRP. Alongside published evidence for a beneficial effect of vitamin D on CRC survival outcomes, these novel findings provide strong rationale for early initiation of vitamin D supplementation after a diagnosis of CRC.

Double faecal immunochemical testing in patients with symptoms suspicious of colorectal cancer

BACKGROUND

Faecal immunochemical test (FIT)-directed pathways based on a single test have been implemented for symptomatic patients. However, with a single test, the sensitivity is 87 per cent at 10 µg haemoglobin (Hb) per g faeces. This aims of this study were to define the diagnostic performance of a single FIT, compared with double FIT in symptomatic populations.

METHODS

Two sequential prospective patient cohorts referred with symptoms from primary care were studied. Patients in cohort 1 were sent a single FIT, and those in cohort 2 received two tests in succession before investigation. All patients were investigated, regardless of having a positive or negative test (threshold 10 µg Hb per g).

RESULTS

In cohort 1, 2260 patients completed one FIT and investigation. The sensitivity of single FIT was 84.1 (95 per cent c.i. 73.3 to 91.8) per cent for colorectal cancer and 67.4 (61.0 to 73.4) per cent for significant bowel pathology. In cohort 2, 3426 patients completed at least one FIT, and 2637 completed both FITs and investigation. The sensitivity of double FIT was 96.6 (90.4 to 99.3) per cent for colorectal cancer and 83.0 (77.4 to 87.8) per cent for significant bowel pathology. The second FIT resulted in a 50.0 per cent reduction in cancers missed by the first FIT, and 30.0 per cent for significant bowel pathology. Correlation between faecal Hb level was only modest (rs = 0.58), and 16.8 per cent of double tests were discordant, 11.4 per cent in patients with colorectal cancer and 18.3 per cent in those with significant bowel pathology.

CONCLUSION

FIT in patients with high-risk symptoms twice in succession reduces missed significant colorectal pathology and has an acceptable workload impact.

Oral vitamin D supplementation induces transcriptomic changes in rectal mucosa that are linked to anti-tumour effects

BACKGROUND

The risk for several common cancers is influenced by the transcriptomic landscape of the respective tissue-of-origin. Vitamin D influences in vitro gene expression and cancer cell growth. We sought to determine whether oral vitamin D induces beneficial gene expression effects in human rectal epithelium and identify biomarkers of response.

METHODS

Blood and rectal mucosa was sampled from 191 human subjects and mucosa gene expression (HT12) correlated with plasma vitamin D (25-OHD) to identify differentially expressed genes. Fifty subjects were then administered 3200IU/day oral vitamin D3 and matched blood/mucosa resampled after 12 weeks. Transcriptomic changes (HT12/RNAseq) after supplementation were tested against the prioritised genes for gene-set and GO-process enrichment. To identify blood biomarkers of mucosal response, we derived receiver-operator curves and C-statistic (AUC) and tested biomarker reproducibility in an independent Supplementation Trial (BEST-D).

RESULTS

Six hundred twenty-nine genes were associated with 25-OHD level (P < 0.01), highlighting 453 GO-term processes (FDR<0.05). In the whole intervention cohort, vitamin D supplementation enriched the prioritised mucosal gene-set (upregulated gene-set P < 1.0E-07; downregulated gene-set P < 2.6E-05) and corresponding GO terms (P = 2.90E-02), highlighting gene expression patterns consistent with anti-tumour effects. However, only 9 individual participants (18%) showed a significant response (NM gene-set enrichment P < 0.001) to supplementation. Expression changes in HIPK2 and PPP1CC expression served as blood biomarkers of mucosal transcriptomic response (AUC=0.84 [95%CI 0.66-1.00]) and replicated in BEST-D trial subjects (HIPK2 AUC=0.83 [95%CI 0.77-0.89]; PPP1CC AUC=0.91 [95%CI 0.86-0.95]).

CONCLUSIONS

Higher plasma 25-OHD correlates with rectal mucosa gene expression patterns consistent with anti-tumour effects, and this beneficial signature is induced by short-term vitamin D supplementation. Heterogenous gene expression responses to vitamin D may limit the ability of randomised trials to identify beneficial effects of supplementation on CRC risk. However, in the current study blood expression changes in HIPK2 and PPP1CC identify those participants with significant anti-tumour transcriptomic responses to supplementation in the rectum. These data provide compelling rationale for a trial of vitamin D and CRC prevention using easily assayed blood gene expression signatures as intermediate biomarkers of response.

Risk of missing colorectal cancer with a COVID-adapted diagnostic pathway using quantitative faecal immunochemical testing

BACKGROUND

COVID-19 has brought an unprecedented challenge to healthcare services. The authors' COVID-adapted pathway for suspected bowel cancer combines two quantitative faecal immunochemical tests (qFITs) with a standard CT scan with oral preparation (CT mini-prep). The aim of this study was to estimate the degree of risk mitigation and residual risk of undiagnosed colorectal cancer.

METHOD

Decision-tree models were developed using a combination of data from the COVID-adapted pathway (April-May 2020), a local audit of qFIT for symptomatic patients performed since 2018, relevant data (prevalence of colorectal cancer and sensitivity and specificity of diagnostic tools) obtained from literature and a local cancer data set, and expert opinion for any missing data. The considered diagnostic scenarios included: single qFIT; two qFITs; single qFIT and CT mini-prep; two qFITs and CT mini-prep (enriched pathway). These were compared to the standard diagnostic pathway (colonoscopy or CT virtual colonoscopy (CTVC)).

RESULTS

The COVID-adapted pathway included 422 patients, whereas the audit of qFIT included more than 5000 patients. The risk of missing a colorectal cancer, if present, was estimated as high as 20.2 per cent with use of a single qFIT as a triage test. Using both a second qFIT and a CT mini-prep as add-on tests reduced the risk of missed cancer to 6.49 per cent. The trade-off was an increased rate of colonoscopy or CTVC, from 287 for a single qFIT to 418 for the double qFIT and CT mini-prep combination, per 1000 patients.

CONCLUSION

Triage using qFIT alone could lead to a high rate of missed cancers. This may be reduced using CT mini-prep as an add-on test for triage to colonoscopy or CTVC.

Low plasma vitamin D is associated with adverse colorectal cancer survival after surgical resection, independent of systemic inflammatory response

OBJECTIVE

We assessed the effect of surgical resection of colorectal cancer (CRC) on perioperative plasma vitamin D (25OHD) and C-reactive protein (CRP) level. We investigated the relationship between circulating vitamin D level and CRC survival.

DESIGN

We sequentially sampled 92 patients undergoing CRC resection, and measured plasma 25OHD and CRP. For survival analyses, we assayed 25OHD and CRP in two temporally distinct CRC patient cohorts (n=2006, n=2100) and investigated the association between survival outcome, circulating vitamin D and systemic inflammatory response.

RESULTS

Serial sampling revealed a postoperative fall (mean 17.3 nmol/L; p=3.6e-9) in plasma 25OHD (nadir days 1-2). CRP peaked 3-5 days postoperatively (143.1 mg/L; p=1.4e-12), yet the postoperative fall in 25OHD was independent of CRP. In cohort analyses, 25OHD was lower in the 12 months following operation (mean=48.8 nmol/L) than preoperatively (54.8 nmol/L; p=1.2e-5) recovering after 24 months (52.2 nmol/L; p=0.002). Survival analysis in American Joint Committee on Cancer stages I-III demonstrated associations between 25OHD tertile and CRC mortality (HR=0.69; 95% CI 0.46 to 0.91) and all-cause mortality (HR=0.68; 95% CI 0.50 to 0.85), and was independent of CRP. We observed interaction effects between plasma 25OHD and rs11568820 genotype (functional VDR polymorphism) with a strong protective effect of higher 25OHD only in patients with GG genotype (HR=0.51; 95% CI 0.21 to 0.81). We developed an online tool for predicted survival (https://apps.igmm.ed.ac.uk/mortalityCalculator/) that incorporates 25OHD with clinically useful predictive performance (area under the curve 0.77).

CONCLUSIONS

CRC surgery induces a fall in circulating 25OHD. Plasma 25OHD level is a prognostic biomarker with low 25OHD associated with poorer survival, particularly in those with rs11568820 GG genotype. A randomised trial of vitamin D supplementation after CRC surgery has compelling rationale.

The Association of Coloproctology of Great Britain and Ireland consensus guidelines in surgery for inflammatory bowel disease

AIM

There is a requirement of an expansive and up to date review of surgical management of inflammatory bowel disease (IBD) that can dovetail with the medical guidelines produced by the British Society of Gastroenterology.

METHODS

Surgeons who are members of the ACPGBI with a recognised interest in IBD were invited to contribute various sections of the guidelines. They were directed to produce a procedure based document using literature searches that were systematic, comprehensible, transparent and reproducible. Levels of evidence were graded. An editorial board was convened to ensure consistency of style, presentation and quality. Each author was asked to provide a set of recommendations which were evidence based and unambiguous. These recommendations were submitted to the whole guideline group and scored. They were then refined and submitted to a second vote. Only those that achieved >80% consensus at level 5 (strongly agree) or level 4 (agree) after 2 votes were included in the guidelines.

RESULTS

All aspects of surgical care for IBD have been included along with 157 recommendations for management.

CONCLUSION

These guidelines provide an up to date and evidence based summary of the current surgical knowledge in the management of IBD and will serve as a useful practical text for clinicians performing this type of surgery.

The impact of vitamin D pathway genetic variation and circulating 25-hydroxyvitamin D on cancer outcome: systematic review and meta-analysis

BACKGROUND

Vitamin D has been linked with improved cancer outcome. This systematic review and meta-analysis investigates the relationship between cancer outcomes and both vitamin D-related genetic variation and circulating 25-hydroxyvitamin D (25OHD) concentration.

METHODS

A systematic review and meta-analysis of papers until November 2016 on PubMed, EMBASE and Web of Science pertaining to association between circulating vitamin D level, functionally relevant vitamin D receptor genetic variants and variants within vitamin D pathway genes and cancer survival or disease progression was performed.

RESULTS

A total of 44 165 cases from 64 studies were included in meta-analyses. Higher 25OHD was associated with better overall survival (hazard ratio (HR=0.74, 95% CI: 0.66-0.82) and progression-free survival (HR=0.84, 95% CI: 0.77-0.91). The rs1544410 (BsmI) variant was associated with overall survival (HR=1.40, 95% CI: 1.05-1.75) and rs7975232 (ApaI) with progression-free survival (HR=1.29, 95% CI: 1.02-1.56). The rs2228570 (FokI) variant was associated with overall survival in lung cancer patients (HR=1.29, 95% CI: 1.0-1.57), with a suggestive association across all cancers (HR=1.26, 95% CI: 0.96-1.56).

CONCLUSIONS

Higher 25OHD concentration is associated with better cancer outcome, and the observed association of functional variants in vitamin D pathway genes with outcome supports a causal link. This analysis provides powerful background rationale to instigate clinical trials to investigate the potential beneficial effect of vitamin D in the context of stratification by genotype.

The contributions of adjusted ambient ultraviolet B radiation at place of residence and other determinants to serum 25-hydroxyvitamin D concentrations

BACKGROUND

Solar ultraviolet B (UVB) radiation is the major source of vitamin D (vitD) for humans.

OBJECTIVES

To describe ambient UVB radiation at wavelengths that induce vitD synthesis (vitD-UVB) in Scotland, and to examine the relationship to serum 25-hydroxyvitamin D (25OHD).

METHODS

We estimated the average vitD-UVB dose for each day of the year and for each postcode area in Scotland, using the Tropospheric Emission Monitoring Internet Service database. Cumulative and weighted vitD-UVB (CW-vitD-UVB) exposure at place of residence was calculated for each participant. Plasma 25OHD was assayed in 1964 healthy participants.

RESULTS

Significant seasonal and geographical variation in vitD-UVB was observed. Ambient vitD-UVB exposure at place of residence was significantly associated with plasma 25OHD (P < 0·01). An average increase in 25OHD of 1 ng mL(-1) was observed for every 1000 mJ cm(-2) higher CW-vitD-UVB dose or for every 2·5 μg of daily supplement taken. Adequate 25OHD concentration (> 16 ng mL(-1)) was observed in the majority when CW-vitD-UVB dose was > 6000 mJ cm(-2), a level of ambient radiation achieved only in summer months in Scotland. When predicting vitD deficiency, dramatic improvement in the area under the curve was observed (from 0·55 to 0·70) after CW-vitD-UVB dose was added to the model, in addition to a range of other covariates.

CONCLUSIONS

Ambient vitD-UVB can be a useful predictor of vitD status. Geotemporally mapped measurements of vitD-UVB can be used as a proxy for vitD status or as a covariate in epidemiological research, particularly if 25OHD is unavailable.

A simple method to overcome the inhibitory effect of heparin on DNA amplification

BACKGROUND

Genetic material from large patient cohorts is increasingly central to translational genetic research. However, patient blood samples are a finite resource and their supply and storage are often dictated by clinical and not research protocols. Our experience supports difficulty in amplifying DNA from blood stored in herparin; a scenario that other researchers may have or will encounter. This technical note describes a number of simple steps that enable successful PCR amplification.

METHODS

DNA was extracted using the Illustra Nucleon Genomic DNA Extraction Kit. PCR amplification was attempted using a number of commercially available PCR mastermixes.

RESULTS

PCR DNA amplification failed using ReddyMix™ PCR Master Mix, Thermo-Start® (Thermo Scientific Inc. US) and ZymoTaq™ (Zymo research, US) PCR mastermixes, as demonstrated absence of products on gel electrophoresis. However, using the Invitrogen™ (Thermo Scientific Inc., US) Platinum® Taq DNA Polymerase, PCR products were identified on a 1% agarose gel for all samples. PCR products were cleaned with ExoSAP-IT® (Affymetrix Inc., US) and a sequencing reaction undertaken using a standard Big Dye protocol. Subsequent genotyping was successful for all samples for alleles at the CDH1 locus.

CONCLUSION

From our experience a standard phenol/chloroform purification and using the Invitrogen™ Platinum® Taq has enabled the amplification of whole blood samples taken into lithium heparin and stored frozen for up to a month. This simple method may enable investigators to utilise blood taken in lithium heparin for DNA extraction and amplification.

Diverticular disease in Scotland: 2000-2010

AIM

Symptomatic diverticular disease (DD) may be increasing in incidence in western society particularly in younger age groups. This study aimed to describe hospital admission rates and management for DD in Scotland between 2000 and 2010.

METHOD

Data were obtained from the Scottish Morbidity Records (SMR01). The study cohort included all patients with a hospital admission and a primary diagnosis of DD of the large intestine (ICD-10 primary code K57).

RESULTS

Scottish NHS hospitals reported 90 990 admissions for DD (in 87 314 patients) from 2000 to 2010. The annual number of admissions increased by 55.2% from 6591 in 2000 to 10,228 in 2010, an average annual increase per year of 4.5%. Most of the increase attributable to DD was due to elective day cases (3618 in 2000; 6925 in 2010) a likely consequence of a greater proportion of the population accessing colonoscopy over that time period. There was an 11% increase in inpatient admissions (2973-3303), 60% of these patients being women. Admissions in younger age groups increased proportionally in the later years of the study, and there was an association between DD admissions and greater deprivation. Despite an increase in complicated DD from 22.9% in 2000 to 27.1% in 2010 and a 16.8% increase in emergency inpatient admissions, the rate of surgery fell during the period of study.

CONCLUSION

This report supports findings of other population-based studies of western countries indicating that DD is an increasing burden on health service resources, particularly in younger age groups.

The MSH2 c.388_389del mutation shows a founder effect in Portuguese Lynch syndrome families

The MSH2 c.388_389del mutation has occasionally been described in Lynch families worldwide. At the Portuguese Oncology Institute in Porto, Portugal, we have identified 16 seemingly unrelated families with this germline mutation. To evaluate if this alteration is a founder or a recurrent mutation we performed haplotype analysis in the 16 Portuguese index cases and 55 relatives, as well as in four index cases and 13 relatives reported from Germany, Scotland, England, and Argentina. In the Portuguese families we observed a shared haplotype of approximately 10 Mb and all were originated from the north of Portugal. These results suggest that this alteration is a founder mutation in Portugal with a relatively recent origin. In the reported families outside Portugal with this mutation different haplotype backgrounds were observed, supporting the hypothesis that it occurred de novo on multiple occasions. We also conclude that the high proportion of families with the MSH2 c.388_389del mutation indicates that screening for this alteration as a first step may be cost-effective in the genetic testing of Lynch syndrome suspects of Portuguese ancestry, especially those originating from the north of Portugal.

TERC polymorphisms are associated both with susceptibility to colorectal cancer and with longer telomeres

BACKGROUND AND AIMS

Shorter telomeres have been associated with increased risk of malignancy, including colorectal cancer (CRC). Telomere length is heritable and may be an intermediate phenotype linked to genetic susceptibility to CRC.

METHODS

In a large sample, the study investigated whether candidate single nucleotide polymorphisms (SNP) in 'telomere biology' genes were associated with telomere length in leucocytes. SNP associated with an increased risk of CRC were searched for separately.

RESULTS

Carriers of the common allele at SNP rs10936599, near the telomerase RNA component (TERC) locus, had significantly longer telomeres. It was independently found that the same rs10936599 allele was associated with increased risk of both CRC and colorectal adenomas. Neither telomere length nor CRC risk was associated with variation near telomerase reverse transcriptase or other telomere biology genes. In silico analysis showed that SNP rs2293607 was strongly correlated with rs10936599, mapped within TERC transcripts, had a predicted effect on messenger RNA folding and lay at a reported transcription factor binding site. TERC mRNA were expressed, differing only at the alleles of rs2293607, in CRC cell line HCT116. The long-telomere/CRC-risk allele was associated with higher levels of TERC mRNA and the formation of longer telomeres.

CONCLUSIONS

Common genetic variation at TERC is associated with both longer telomeres and an increased risk of CRC, a potential mechanism being reduced levels of cell senescence or death. This finding is somewhat paradoxical, given retrospective studies reporting that CRC cases have shorter telomeres than controls. One possibility is that that association actually results from poorer survival in patients with longer telomeres.

SNP mistyping in genotyping arrays--an important cause of spurious association in case-control studies

Using genome-wide association studies to identify genetic variants contributing to disease has been highly successful with many novel genetic predispositions identified and biological pathways revealed. Several pitfalls for spurious association or non-replication have been highlighted: from population structure, automated genotype scoring for cases and controls, to age-varying association. We describe an important yet unreported source of bias in case-control studies due to variations in chip technology between different commercial array releases. As cases are commonly genotyped with newer arrays and freely available control resources are frequently used for comparison, there exists an important potential for false associations which are robust to standard quality control and replication design.

A large-scale meta-analysis to refine colorectal cancer risk estimates associated with MUTYH variants

Background:

Defective DNA repair has a causal role in hereditary colorectal cancer (CRC). Defects in the base excision repair gene MUTYH are responsible for MUTYH-associated polyposis and CRC predisposition as an autosomal recessive trait. Numerous reports have suggested MUTYH mono-allelic variants to be low penetrance risk alleles. We report a large collaborative meta-analysis to assess and refine CRC risk estimates associated with bi-allelic and mono-allelic MUTYH variants and investigate age and sex influence on risk.

Methods:

MUTYH genotype data were included from 20 565 cases and 15 524 controls. Three logistic regression models were tested: a crude model; adjusted for age and sex; adjusted for age, sex and study.

Results:

All three models produced very similar results. MUTYH bi-allelic carriers demonstrated a 28-fold increase in risk (95% confidence interval (CI): 6.95–115). Significant bi-allelic effects were also observed for G396D and Y179C/G396D compound heterozygotes and a marginal mono-allelic effect for variant Y179C (odds ratio (OR)=1.34; 95% CI: 1.00–1.80). A pooled meta-analysis of all published and unpublished datasets submitted showed bi-allelic effects for MUTYH, G396D and Y179C (OR=10.8, 95% CI: 5.02–23.2; OR=6.47, 95% CI: 2.33–18.0; OR=3.35, 95% CI: 1.14–9.89) and marginal mono-allelic effect for variants MUTYH (OR=1.16, 95% CI: 1.00–1.34) and Y179C alone (OR=1.34, 95% CI: 1.01–1.77).

Conclusions:

Overall, this large study refines estimates of disease risk associated with mono-allelic and bi-allelic MUTYH carriers.

Fecal calprotectin predicts the clinical course of acute severe ulcerative colitis

OBJECTIVES

Calprotectin is a granulocyte neutrophil-predominant cytosolic protein. Fecal concentrations are elevated in intestinal inflammation and may predict relapse in quiescent inflammatory bowel disease. We aim to investigate fecal calprotectin (FC) as a biomarker in predicting the clinical course of acute severe ulcerative colitis (ASUC).

METHODS

In 90 patients with ASUC requiring intensive in-patient medical therapy (January 2005-September 2007), we investigated the discriminant ability of FC to predict colectomy and corticosteroid and infliximab nonresponse. All patients received parenteral corticosteroids as first-line treatment; 21 (23.3%) were also treated with infliximab (5 mg/kg), after failure of corticosteroid therapy.

RESULTS

Of 90 patients, 31 (34.4%) required colectomy, including 11 (52.4%) of those treated with infliximab. Overall FC was high (1,020.0 microg/g interquartile range: 601.5-1,617.5). FC was significantly higher in patients requiring colectomy (1,200.0 vs. 887.0; P=0.04), with a trend toward significance when comparing corticosteroid nonresponders and responders (1,100.0 vs. 863.5; P=0.08), as well as between infliximab nonresponders and responders (1,795.0 vs. 920.5; P=0.06). Receiver-operator characteristic curve analysis yielded an area under the curve of 0.65 to predict colectomy (P=0.04), with a maximum likelihood ratio of 9.23, specificity 97.4%, and sensitivity 24.0% at a cutoff point of 1,922.5 microg/g. Kaplan-Meier analyses showed that using 1,922.5 microg/g over a median follow-up of 1.10 years, 87% of patients will need subsequent colectomy.

CONCLUSIONS

This is the first data set to demonstrate that FC levels are dramatically elevated in severe UC. These data raise the possibility that this biomarker can predict response to first or second-line medical therapy in this setting.

A prevalence screen of MRSA nasal colonisation amongst UK doctors in a non-clinical environment

Screening for methicillin-resistant Staphylococcus aureus (MRSA) carriage in healthcare workers (HCWs) is both contentious and confounded by a lack of knowledge of background prevalence rates. This study examines prevalence of nasal MRSA carriage amongst a spectrum of medical professionals in a non-clinical environment. Medical conference attendees volunteered for screening for nasal MRSA carriage, and anonymised demographic data and attitudes towards screening were recorded. Two hundred sixty volunteers participated. One hundred seventy-three participants (67%) were from the British Medical Association's Annual Representatives Meeting, and 87 participants (33%) were attending the Association of Surgeons in Training conference. Six (2%) participants were positive for MRSA nasal carriage (BMA = 1%, ASIT = 5%; p = 0.099). Participants from a surgical specialty (4.8%) were more likely to be MRSA positive (p = 0.039). All positive samples came from male participants (p = 0.182). However, there was no significant association with gender, seniority or country of employment and MRSA status. Routine screening for MRSA was supported by 63% of participants in HCWs; 36% had previously undergone such screening. MRSA nasal carriage rates within this cross-sectional study are lower than studies reporting carriage rates in HCWs within the clinical environment. Further research is required to examine the relationship between MRSA nasal colonisation status of a HCW and subsequent MRSA infection in patients.

Cascade genetic testing for mismatch repair gene mutations

Mismatch repair gene mutation carriers have a high risk of developing colorectal cancer, and can benefit from appropriate surveillance. A combined population based ascertainment cascade genetic testing approach provides a systematic and potentially effective strategy for identifying such carriers. We have developed a Markov Chain computer model system which simulates various factors influencing cascade genetic testing; including demographics, uptake, genetic epidemiology and family size. This was used to evaluate cascade genetic testing for mismatch repair gene mutations in theory and practice. Simulations focussed on the population of Scotland by way of illustration, and were based on a 20-year programme in which index cases were ascertained from colorectal cancer cases aged<55 years at onset. Results indicated that without practical barriers to cascade genetic testing, 545 (95% CI=522, 568) carriers could be identified; 42% of the population total. This comprised approximately 140 index cases, 302 asymptomatic relatives and 104 previously affected relatives. However, when realistic ascertainment and acceptance rates were used to inform simulations, only 257 (95% CI=246, 268) carriers, about 20% of the carrier population, were identifiable. Of these approximately 112 were index cases, 108 were asymptomatic relatives, and 37 were previously affected relatives. This contrast emphasises the importance of ascertainment and acceptance rates. Likewise the low number of index cases shows that case identification is a limiting factor. In the absence of robust data from epidemiological studies, these findings can inform decisions about the use of cascade genetic testing for mismatch repair gene mutations.

Outcomes of the rectal remnant following colectomy for ulcerative colitis

OBJECTIVE

Controversy surrounds the optimal surgical management of the distal rectal remnant during colectomy for ulcerative colitis (UC) and the potential benefit from the placement of a rectal catheter for remnant drainage. This study reviews the clinical outcomes of patients who have undergone colectomy for UC with intra-peritoneal closure of the rectal remnant.

METHOD

Analysis of prospective data lodged on Lothian Surgical Audit databases from patients treated in a tertiary coloproctology unit over 11 years.

RESULTS

One hundred and fifty-nine patients were identified, the mean age was 41.9 years, 63% were men. Failure of maximal medical therapy necessitated surgery for 78.1% patients, while 12.6% had acute perforation and 11.9% had toxic megacolon. Complications included five (3.1%) stump dehiscences, eight (5.0%) intra-abdominal/pelvic collections, four (2.5%) significant wound infections, three (1.9%) small bowel obstructions and three (1.9%) deaths. Within the follow-up period, 62.3% patients had an ileo-pouch anal anastomosis (IPAA), 7.5% patients had a completion proctectomy, 10.1% patients within the series had a retained rectal remnant after 1 year follow up, the remaining patients had less than 1 year follow up.

CONCLUSION

The intra-peritoneal rectal stump following colectomy for UC is associated with low rates of pelvic sepsis and a high proportion of patients successfully proceeding to IPAA.

Bacterial contamination of hospital bed-control handsets in a surgical setting: a potential marker of contamination of the healthcare environment

INTRODUCTION

Patients undergoing colorectal surgical resections have a high incidence of surgical site infection (SSI). Many patient-specific risk factors have been recognised in association with SSI in such patients, but environmental contamination is increasingly recognised as a contributor to hospital-acquired infection (HAI). This study set out to describe the bacterial contamination of the patient environment, using hospital bed-control handsets, as they are frequently handled by both staff and patients and represent a marker of environmental contamination.

PATIENTS AND METHODS

On two unannounced sampling events, 1 week apart, 140 bacteriological assessments were made of 70 hospital bed control handsets within a specialist colorectal surgical unit.

RESULTS

Of the handsets examined, 67 (95.7%) demonstrated at least one bacterial species (52.9% grew 1, 30% grew 2 and 12.9% grew 3 or more bacterial species). Of these, 29 (41.4%) bed-control handsets grew bacteria known to cause nosocomial infection, including 22 (31.4%) handsets which grew Enterococcus spp., 9 (12.9%) which grew MRSA, 2 (2.9%) which grew MSSA, 2 (2.9%) which grew coliforms, and 1 (1.4%) handset which grew anaerobes. At 1-week follow-up, 31 bed-control handsets showed evidence of contamination by the same bacterial species.

CONCLUSIONS

This study revealed high levels of bacteria known to cause HAI, contaminating hospital bed-control handsets in a surgical setting. Further study is now required to confirm whether hospital environmental contamination is causally involved in SSI.

Germline mutation prevalence in the base excision repair gene, MYH, in patients with endometrial cancer

Germline mutations in the base excision repair gene, MutY human homolog (MYH), have recently been associated with a recessively inherited multiple adenoma polyposis syndrome and colorectal cancer. The spectrum of extracolonic lesions is still being characterized, although preliminary reports suggest that bi-allelic mutation carriers may share some of the clinical features of other hereditary colon cancer syndromes. Of 225 endometrial cancer patients, we identified one individual as a compound heterozygote, carrying mutations Y165C and G382D of MYH, and five individuals with heterozygous defects (three G382D and two Y165C). The patient with the bi-allelic Y165C/G382D mutation also had a sebaceous carcinoma, a feature of Muir-Torre syndrome. Although several intronic polymorphisms were detected in the heterozygous carriers, no other pathogenic variants were identified. While not conclusive, this novel and interesting finding provides evidence that bi-allelic germline mutations in MYH may increase susceptibility to endometrial cancer.

Contribution of the NOD1/CARD4 insertion/deletion polymorphism +32656 to inflammatory bowel disease in Northern Europe

BACKGROUND

NOD1/CARD4 and NOD2/CARD15 are both intracellular pattern-recognition receptors. The NOD1/CARD4 gene lies within a previously described inflammatory bowel disease (IBD) locus (7p14). An association has been suggested between the NOD1/CARD4+32656 deletion*1 variant of a complex deletion*1/insertion*2 polymorphism and IBD in 1 recent study in Europe. Our aim was to assess the influence of NOD1/CARD4+32656 on disease susceptibility and phenotype in the Scottish and Swedish IBD populations.

METHODS

A total of 3,962 individuals (1,791 IBD patients, 522 parents, 1,649 healthy controls) from 2 independent populations (Scotland and Sweden) were genotyped for NOD1/CARD4+32656 A/C by TaqMan and direct sequencing. Case-control, Transmission Disequilibrium Testing (TDT) and detailed genotype-phenotype (Montreal) analyses were performed. The case-control analysis had 80% power to detect an effect size of odds ratio (OR) 1.21 for IBD.

RESULTS

In case-control analyses in Scottish and Swedish patients, none of the genotypes studied in IBD, Crohn's disease (CD) or ulcerative colitis (UC), differed significantly from controls (deletion*1 allelic frequency 73.9%, 73.6%, 73.9%, and 73.6%, respectively: all P > 0.8). No epistatic interaction with NOD2/CARD15 was seen for CD susceptibility. TDT analysis in our Scottish early onset cohort was negative.

CONCLUSIONS

This variant allele of NOD1/CARD4+32656 is not associated with a strong effect on susceptibility to IBD in children and adults in Northern Europe. A gene-wide haplotype-based approach may be preferable to analysis of individual variants to assess the contribution of the NOD1/CARD4 gene to IBD.

Long-term cancer risk of the anorectal cuff following restorative proctocolectomy assessed by p53 expression and cuff dysplasia

OBJECTIVE

Restorative proctocolectomy (RP) for ulcerative colitis (UC) retains a 'cuff' of columnar rectal epithelium that has unknown risk of malignant change. Markers of malignant potential in UC include aberrant p53 expression and dysplasia. We undertook a prospective study comprising serial surveillance biopsy and assessed the occurrence of aberrant p53 expression, epithelial dysplasia and carcinoma in the retained anorectal cuff following stapled RP.

METHOD

A total of 110 patients who underwent stapled RP for UC between 1988 and 1998 were followed up by cuff surveillance biopsies under general anaesthesia. Histological samples were analysed by a specialist colorectal pathologist for the presence of rectal mucosa, dysplasia and carcinoma. Immunohistochemistry for p53 expression was performed for each most recent cuff biopsy. Median follow-up was 56 months (12-145) and median time since diagnosis of UC was 8.8 years (2-32).

RESULTS

Rectal mucosa was obtained from the cuff in 65% of biopsies. No overt carcinomas developed during the follow-up period and there was no dysplasia or carcinoma in any cuff biopsy. The p53 overexpression was identified in 38 specimens (50.6%), but was also identified in controls (3/3 colitis, 3/3 ileal pouch and 6/6 stapled haemorrhoidectomy donuts).

CONCLUSION

The lack of carcinoma and dysplasia in the columnar cuff epithelium specimens is reassuring. The lack of stabilized p53 and absence of a relationship between p53 stabilization and dysplasia up to 12 years after pouch formation suggests neoplastic transformation is a rare event. Furthermore, p53 expression was not useful in surveillance of cuff biopsies from patients who have undergone RP for UC and the search should continue for alternative predysplastic markers. These data suggest that in patients who do not have high-grade dysplasia or colorectal cancer at the time of RP, cuff surveillance in the first decade after pouch formation is unnecessary. However, we consider regular cuff surveillance biopsies should continue for patients with high-grade dysplasia, whether or not there was a carcinoma in the original colectomy specimen.

Prevalence of family history of colorectal cancer in the general population

BACKGROUND

Robust estimates of the prevalence of a family history of colorectal cancer in the general population are essential to inform planning of provision for colonoscopic surveillance and for clinical genetics services. However, there is a paucity of high-quality data.

METHODS

Computerized record linkage was used to assess systematically the family history of 160 cancer-free community subjects and thereby provide prevalence data that are independent of participant recall. The data set comprised 2664 first- and second-degree relatives of study subjects, with 148 068 years at risk.

RESULTS

Of people in the 30-70 years age range, 9.4 (95 per cent confidence interval (c.i.) 5.8 to 14.9) per cent had a first-degree relative affected by colorectal cancer, and 28.8 (95 per cent c.i. 22.3 to 36.2) per cent had an affected first- or second-degree relative. Between 0 and 3.1 per cent of study subjects merited colonic surveillance, depending on the stringency of the guidelines used.

CONCLUSION

An appreciable proportion of the general population has a relative affected by colorectal cancer, sufficient to merit screening under certain criteria. In the absence of good-quality evidence supporting colonoscopic surveillance in groups at moderate risk, these data directly inform the planning of services for people with a family history of colorectal cancer. However, the clinical risk and financial implications of screening should be taken into account.

Aspirin-induced nuclear translocation of NFkappaB and apoptosis in colorectal cancer is independent of p53 status and DNA mismatch repair proficiency

Substantial evidence indicates nonsteroidal anti-inflammatory drugs (NSAIDs) protect against colorectal cancer (CRC). However, the molecular basis for this anti-tumour activity has not been fully elucidated. We previously reported that aspirin induces signal-specific IκBα degradation followed by NFκB nuclear translocation in CRC cells, and that this mechanism contributes substantially to aspirin-induced apoptosis. We have also reported the relative specificity of this aspirin-induced NFκB-dependent apoptotic effect for CRC cells, in comparison to other cancer cell types. It is now important to establish whether there is heterogeneity within CRC, with respect to the effects of aspirin on the NFκB pathway and apoptosis. p53 signalling and DNA mismatch repair (MMR) are known to be deranged in CRC and have been reported as potential molecular targets for the anti-tumour activity of NSAIDs. Furthermore, both p53 and MMR dysfunction have been shown to confer resistance to chemotherapeutic agents. Here, we set out to determine the p53 and hMLH1 dependency of the effects of aspirin on NFκB signalling and apoptosis in CRC. We specifically compared the effects of aspirin treatment on cell viability, apoptosis and NFκB signalling in an HCT-116 CRC cell line with the p53 gene homozygously disrupted (HCT-116^p53−/−) and an HCT-116 cell line rendered MMR proficient by chromosomal transfer (HCT-116^+ch3), to the parental HCT-116 CRC cell line. We found that aspirin treatment induced apoptosis following IκBα degradation, NFκB nuclear translocation and repression of NFκB-driven transcription, irrespective of p53 and DNA MMR status. These findings are relevant for design of both novel chemopreventative agents and chemoprevention trials in CRC.

Prognosis in DNA mismatch repair deficient colorectal cancer: are all MSI tumours equivalent?

Microsatellite instability (MSI) in colorectal tumours is the hallmark of defective DNA mismatch repair (MMR) and high level MSI can be detected in up to 15% of incident colorectal cancers. MSI in sporadic colorectal tumours is primarily due to epigenetic silencing of MLH1 while MSI is almost universal in tumours from HNPCC family members due to germline MMR gene mutation with loss or mutational inactivation of the second copy as a somatic event. There is evidence that tumour MSI is associated with a better outcome than the generality of large bowel malignancy. However, although MSI occurs in both sporadic colorectal cancer and in tumours arising in patients with germline MMR gene mutations, cancer survival should not be considered to be equivalent for these two groups with MSI tumours simply because both exhibit similarities in molecular phenotype. Here, we review the evidence on prognosis in patients with sporadic MSI tumours compared to those who have inherited a germline DNA MMR repair gene defect. In addition, we explore whether there are variables that afford opportunity to distinguish three groups on the basis of MSI status, namely: sporadic MSI tumours; MSI tumours in carriers of germline MMR gene defects; microsatellite stable (MSS) tumours. Differences in prognosis between these three groups is important because it underpins the rationale for surveillance and early identification of tumours in MMR gene carriers, as well as refining understanding of the influence of MSI on cancer progression. Furthermore, we discuss the effect of MSI on the effectiveness of chemotherapy regimens.

Assessment of outcomes after colorectal cancer resection in the elderly as a rationale for screening and early detection

BACKGROUND

Clinical, social and survival outcomes in elderly patients undergoing bowel cancer surgery were studied to explore the justification for the current upper age limit in colorectal cancer screening programmes.

METHODS

Scottish national data were analysed to determine age-specific population survival following a diagnosis of colorectal cancer. Detailed analysis of outcome variables was undertaken in a cohort of 180 patients aged over 80 years who underwent resection of colorectal cancer.

RESULTS

Population analysis revealed that the absolute risk of developing colorectal cancer was highest in those aged over 80 years, but relative survival was disproportionately poor. Of 180 patients in this age group, 30.0 per cent required an emergency procedure and only 4.6 per cent had Dukes' stage A tumours. Determinants of all-cause mortality were tumour stage (P < 0.001) and degree of co-morbidity (P = 0.004). Some 88.0 per cent of elderly patients returned to the same category of accommodation as that before admission.

CONCLUSION

Colorectal cancer is increasingly common in people aged over 80 years and survival is disproportionately poor compared with that in other age groups. Elective management of early-stage cancer has a better outcome than emergency surgery. The majority of patients maintain social independence. These population and hospital data provide a rationale for early, and even presymptomatic, detection of colorectal cancer in the elderly.

Evidence for colorectal cancer cell specificity of aspirin effects on NF kappa B signalling and apoptosis

Epidemiological evidence indicates that non-steroidal anti-inflammatory drugs (NSAIDs) protect against colorectal cancer (CRC) to a greater degree than other non-gastrointestinal cancers, but the molecular basis for this difference is unknown. We previously reported that aspirin induces signal-specific IκBα degradation followed by NFκB nuclear translocation in CRC cells, and that this mechanism contributes substantially to aspirin-induced apoptosis. Here, we explored the hypothesis that cell-type specific effects on NFκB signalling are responsible for the observed differences in protection by aspirin against CRC compared to breast and gynaecological cancers. We also assessed whether COX-2 expression, mutation status of adenomatous polyposis coli (APC), β-catenin, p53, or DNA mismatch repair (MMR) genes in CRC lines influenced aspirin-induced effects. We found that aspirin induced concentration-dependent IκBα degradation, NFκB nuclear translocation and apoptosis in all CRC lines studied. However, there was no such effect on the other cancer cell types, indicating a considerable degree of cell-type specificity. The lack of effect on NFκB signalling, paralleled by absence of an apoptotic response to aspirin in non-CRC lines, strongly suggests a molecular rationale for the particular protective effect of NSAIDs against CRC. Effects on NFκB and apoptosis were observed irrespective of COX-2 expression, or mutation status in APC, β-catenin, p53 and DNA MMR genes, underscoring the generality of the aspirin effect on NFκB in CRC cells. These findings raise the possibility of cell-type specific targets for the development of novel chemopreventative agents.

Accuracy of reporting of family history of colorectal cancer

BACKGROUND AND AIMS

Family history is used extensively to estimate the risk of colorectal cancer but there is considerable potential for recall bias and inaccuracy. Hence we systematically assessed the accuracy of family history reported at interview compared with actual cancer experience in relatives.

METHODS

Using face to face interviews, we recorded family history from 199 colorectal cancer cases and 133 community controls, totalling 5637 first and second degree relatives (FDRs/SDRs). We linked computerised cancer registry data to interview information to determine the accuracy of family history reporting.

RESULTS

Cases substantially underreported colorectal cancer arising both in FDRs (sensitivity 0.566 (95% confidence interval (CI) 0.433, 0.690); specificity 0.990 (95% CI 0.983, 0.994)) and SDRs (sensitivity 0.271 (95% CI 0.166, 0.410); specificity 0.996 (95% CI 0.992, 0.998)). There was no observable difference in accuracy of reporting family history between case and control interviewees. Control subjects similarly underreported colorectal cancer in FDRs (sensitivity 0.529 (95% CI 0.310, 0.738); specificity 0.995 (95% CI 0.989, 0.998)) and SDRs (sensitivity 0.333 (95% CI 0.192, 0.512); specificity 0.995 (95% CI 0.991, 0.995)). To determine practical implications of inaccurate family history, we applied family history criteria before and after record linkage. Only two of five families reported at interview to meet surveillance criteria did so after validation, whereas only two of six families that actually merited surveillance were identified by interview.

CONCLUSIONS

This study has quantified the inaccuracy of interview in identifying people at risk of colorectal cancer due to a family history. Colorectal cancer was substantially underreported and so family history information should be interpreted with caution. These findings have considerable relevance to identifying patients who merit surveillance colonoscopy and to epidemiological studies.

Colonoscopy surveillance of individuals at risk of familial colorectal cancer

BACKGROUND

Individuals with first degree relatives affected with colorectal cancer (CRC) at a young age, or more than one relative affected but who do not fulfil the Amsterdam criteria for a diagnosis of hereditary non-polyposis colon cancer (HNPCC), are believed to be at an increased risk of CRC. However, there is a paucity of prospective data on the potential benefit of colonoscopic surveillance in such groups categorised by empiric family history criteria. We report a prospective study of 448 individuals seeking counselling about their perceived family history of CRC.

PATIENTS AND METHODS

Following pedigree tracing, verification, and risk assignment by genetic counsellors, colonoscopy was undertaken for those at a moderate or high risk (HNPCC). Those classified as low risk were reassured and discharged without surveillance. Here we report our findings at the prevalence screen in the 176 patients of the 448 assessed who underwent colonoscopy.

RESULTS

Fifty three individuals had a family history that met Amsterdam criteria (median age 43 years) and 123 individuals were classed as moderate risk (median age 43 years). No cancers were detected at colonoscopy in any group. Four individuals (8% (95% confidence limits (CL) 0.4-15%)) in the high risk group had an adenoma detected at a median age of 46 years and all four were less than 50 years of age. Five (4% (95% CL 0.6- 8%)) of the moderate risk individuals had an adenoma at a median age of 54 years, two of whom were less than 50 years of age.

CONCLUSIONS

These findings indicate that the prevalence of significant neoplasia in groups defined by family history is low, particularly in younger age groups. These prospective data call into question the value of colonoscopy before the age of 50 years in moderate risk individuals.

Mismatch repair genes hMLH1 and hMSH2 and colorectal cancer: a HuGE review

Evidence to support a role for the mismatch repair genes human mutL homolog 1 (hMLH1) and human mutS homolog 2 (hMSH2) in the etiology of colorectal cancer has come from linkage analysis, segregation studies, and molecular biologic analysis. More recently, carriers of potentially pathogenic mutations in the hMLH1/hMSH2 genes have consistently been shown to be at a greatly increased risk of developing colorectal cancer compared with the general population. When considered together, the available evidence shows a strong, consistent, and biologically plausible association between mismatch repair gene mutations and colorectal cancer. The penetrance of mutations in hMLH1/hMSH2 is incomplete and is significantly higher in males (approximately 80%) than in females (approximately 40%). To date, evidence for gene-gene or gene-environment interactions is limited, although preliminary studies have revealed a number of avenues that merit exploration. Population screening for mutation carriers is not currently a feasible option, and mutation analysis remains restricted to either relatives of mutation carriers or colorectal cancer cases selected on the basis of phenotype.

Whole-gene APC deletions cause classical familial adenomatous polyposis, but not attenuated polyposis or "multiple" colorectal adenomas

Familial adenomatous polyposis (FAP) is a dominantly inherited colorectal tumor predisposition that results from germ-line mutations in the APC gene (chromosome 5q21). FAP shows substantial phenotypic variability: classical polyposis patients develop more than 100 colorectal adenomas, whereas those with attenuated polyposis (AAPC) have fewer than 100 adenomas. A further group of individuals, so-called "multiple" adenoma patients, have a phenotype like AAPC, with 3-99 polyps throughout the colorectum, but mostly have no demonstrable germ-line APC mutation. Routine mutation detection techniques fail to detect a pathogenic APC germ-line mutation in approximately 30% of patients with classical polyposis and 90% of those with AAPC/multiple adenomas. We have developed a real-time quantitative multiplex PCR assay to detect APC exon 14 deletions. When this technique was applied to a set of 60 classical polyposis and 143 AAPC/multiple adenoma patients with no apparent APC germ-line mutation, deletions were found exclusively in individuals with classical polyposis (7 of 60, 12%). Fine-mapping of the region suggested that the majority (6 of 7) of these deletions encompassed the entire APC locus, confirming that haploinsufficiency can result in a classical polyposis phenotype. Screening for germ-line deletions in APC mutation-negative individuals with classical polyposis seems warranted.

Nuclear thymidylate synthase expression, p53 expression and 5FU response in colorectal carcinoma

Thymidylate synthase (TS) is a key enzyme in DNA synthesis and is inhibited by metabolites of the chemotherapeutic agent 5-fluorouracil (5FU). Nuclear expression of TS in human tissue in vivo has not been characterised and its clinicopathological correlates in malignancy are unknown. 52 cases of primary colorectal carcinoma (CRC) and 24 cases of matched metastatic carcinoma were studied immunohistochemically using the monoclonal antibody TS106. The degree of nuclear TS immunostaining correlated closely with levels of TS mRNA expression amongst 10 CRCs studied. Strong nuclear immunostaining was seen in normal basal crypt colonocytes and germinal centre cells, and in a varying proportion of adenocarcinoma cells. Amongst the primary carcinomas, higher TS nuclear expression was associated with prominent extracellular mucin production and right-sided location. Higher TS nuclear expression also showed a significant association with poorer response to protracted venous infusional 5FU therapy. There was no clear association between TS nuclear expression and Ki67 or p53 expression assessed immunohistochemically. There was a strong positive correlation between TS nuclear expression in primary and metastatic CRC but the latter generally showed higher expression than matched primary tumour tissue. These findings confirm the nuclear expression of TS protein in human cells in vivo and provide new insight into how such expression may relate to the behaviour of CRCs.

Mutation frequency in coding and non-coding repeat sequences in mismatch repair deficient cells derived from normal human tissue

Repetitive tracts within the coding regions of TGFBR2 and BAX are frequently mutated in mismatch repair deficient tumours and are implicated in tumour progression. However, there has been little study of the balance between selection pressure and inherent instability at sequences within these genes. To determine whether TGFBR2 and BAX are inherently prone to mutations in the presence of MMR defects, we studied MMR deficient cells derived from B-lymphocytes. By analysing cells derived from normal tissue we aimed to minimize the effects of selection pressures that bias the apparent frequency of mutation. We definitively show that certain sequences, usually repaired by MMR, are inherently unstable. Using a small pool PCR technique we confirmed these cells exhibit microsatellite instability. Additionally, we demonstrate that MMR deficiency results in an excess of mutations, specifically at the poly(A)(10) tract compared to other regions of the TGFBR2 gene (P<0.001). Conversely, an excess of mutations does not appear to arise at the poly(G)(8) tract of the BAX gene. These studies provide insight into the mechanism by which TGFBR2 and BAX genes become mutated during tumorigenesis. These findings invoke the notion of "unmasking" specific hypermutable sequences in particular genes adding further complexity to the concept of the mutator phenotype.

Hypermutability at a poly(A/T) tract in the human germline

Poly(A/T) tracts are abundant simple sequence repeats (SSRs) within the human genome. They constitute part of the coding sequence of a variety of genes, encoding polylysine stretches that are important for protein function. Assessment of poly(A/T) tract stability is also used to identify microsatellite unstable colorectal cancers, which are characteristic of tumours defective in DNA mismatch repair. Despite their importance, little is known about the stability of poly(A/T) SSRs in the human germline. We have determined the stability of a paradigm poly(A/T) tract, BAT-40, by study of population allele frequencies, mutation frequency in families and mutation frequency in sperm DNA. We show that the locus is polymorphic, with a level of heterozygosity of 59.7%. Germline mutation was observed in 13 of 187 germline transmissions (7.0%) in 10 families suggesting BAT-40 is unstable in the germline. Further evidence for germline instability at BAT-40 was provided by small pool PCR analysis of matched blood and sperm DNA templates, revealing a significantly elevated frequency of mutation in the germline (P < 0.001). These findings provide insight into poly(A/T) tract stability in the germline. They also have relevance to the study of gene expression and to determination of microsatellite instability in tumours.

Suppression of intestinal and mammary neoplasia by lifetime administration of aspirin in Apc(Min/+) and Apc(Min/+), Msh2(-/-) mice

Numerous studies have indicated that exposure to nonsteroidal anti-inflammatory drugs is associated with a lowered risk of colorectal cancer. However, analyses of the effect of aspirin upon tumorigenesis in Apc(Min/+) mice have yielded contrasting results. We show that adult dietary exposure to aspirin does not suppress intestinal tumorigenesis in Apc(Min/+) mice, but that continual exposure from the point of conception does. To test whether this regime could suppress the phenotype of murine models of hereditary nonpolyposis colorectal cancer, Msh2-deficient mice were exposed to aspirin. This did not modify the mutator phenotype of Msh2(-/-) mice, but weakly extended survival. Finally, we analyzed (Apc(Min/+), Msh2(-/-)) mice and found that lifetime aspirin exposure significantly delayed the onset of both intestinal and mammary neoplasia. Thus embryonic and perinatal exposure to aspirin suppresses neoplasia specifically associated with the loss of Apc function, opening a potential window of opportunity for nonsteroidal anti-inflammatory drug intervention.

Early-onset colorectal cancer with stable microsatellite DNA and near-diploid chromosomes

Colorectal cancer has been described in terms of genetic instability selectively affecting either microsatellite sequences (MIN) or chromosome number and structure (CIN). A subgroup with apparently stable, near-diploid chromosomes and stable microsatellites (MACS) also exists. These distinctions are important, partly because of their value in highlighting different pathways of carcinogenesis, and partly because of their direct relevance to prognosis. Study of early-onset cancer has often proved a fruitful resource for the identification of the nature and function of cancer susceptibility genes. In a study of colorectal cancer with stable microsatellite DNA, we describe 22 early-onset tumours (mean age=33), compared with 16 late-onset tumours (mean age=68). Both groups contained carcinomas with the MACS phenotype, characterized by near diploid DNA content, as defined by flow cytometry, and minimal chromosome arm deletion or amplification (six or less events per genome), determined by comparative genomic hybridization (CGH). Minimal chromosome imbalance correlated strongly with diploid DNA content (P<0.001). The proportion of MACS cancers was significantly greater in early-onset as compared to late-onset tumours (64 vs 13%, P=0.005). Of the chromosome arm imbalances commonly observed in late-onset tumours, only 18q- was observed more than twice amongst the 14 early-onset MACS tumours. Seventy-nine per cent of these MACS tumours were located in the distal colon, and 69% were at advanced clinico-pathological stages (with lymph node or distant metastasis). A positive family history of colorectal or other cancers was elicited in seven patients in the MACS early-onset group, and one additional patient in this group had a metachronous ovarian cancer. The results suggest that MACS cancer may have a genetic basis different from either MIN or CIN, and further studies of these cancers may lead to discovery of new mechanisms of colorectal carcinogenesis and cancer susceptibility.

Population carrier frequency of hMSH2 and hMLH1 mutations

Knowledge of population carrier frequency for DNA mismatch repair (MMR) gene mutations would contribute to understanding the burden of cancer due to genetic susceptibility, but robust prevalence estimates are lacking. To estimate carrier frequency, we genotyped a cohort of relatives of mutation carriers and determined their colorectal cancer prevalence. Systematic Finnish and US data were combined with Scottish genotype and cancer prevalence data in a Bayesian calculation. The estimated carrier prevalence in the population aged 15-74 years is 1:3139 (95% Cl = 1:1247-1:7626) and these carriers are at high risk of colorectal and other cancers.

Sequence interruptions confer differential stability at microsatellite alleles in mismatch repair-deficient cells

Determinants of instability at a given microsatellite repeat merits investigation in view of relevance to understanding evolution of mutations at such sequences in human populations. The microsatellite D2S123 was studied as a paradigm CA repeat marker. Furthermore, this marker is one of a recommended panel used in molecular screening for hereditary non-polyposis colorectal cancer (HNPCC). In this investigation we show that the mutation rate at the D2S123 locus is markedly influenced by intra-allelic sequence variation within the repetitive tract itself. We employed a novel approach to characterize the nature of instability at D2S123, by utilizing cells derived from a non-tumour lineage, which harbour a dominant negative mismatch repair (MMR) mutation and a mutator phenotype. Individual alleles were typed using a semi-quantitative small pool PCR technique and this demonstrated substantial allele-these specific bias in susceptibility to mutation at the D2S123 locus. In support of these in vitro data, bias in allele mutation rate was also observed in tumours from 41 HNPCC patients, which was dependent on constitutional genotype. Sequencing of cell line and patient DNAs revealed that short alleles are significantly more susceptible to mutation due to the presence of uninterrupted CA repeats. Long D2S123 alleles are intrinsically more stable because of a TA interspersion within the repetitive tract. In addition to extending understanding of mutation at CA repeat dinucleotide tracts, these findings have considerable relevance both to screening programmes and to correlation of microsatellite instability (MSI) with colon cancer survival. The manifestation of tumour MSI may be substantially influenced by constitutional genotype.

NF-kappaB kinetics predetermine TNF-alpha sensitivity of colorectal cancer cells

BACKGROUND

Tumour necrosis factor (TNF)-alpha has considerable anti-tumour activity and may have potential as a treatment for metastatic colorectal cancer. However, TNF-alpha responses in patients and cell lines are variable and TNF-alpha treatment is associated with dose limiting clinical toxicity. Activation of NF-kappaB is protective against TNF-alpha induced cell death, and this may explain tumour resistance.

METHODS

In order to provide further understanding of determinants of TNF-alpha responses, we studied TNF-alpha induced NF-kappaB activation and variable tumour responses. We analysed the kinetics of TNF-alpha induced NF-kappaB activation in colorectal cancer cells and determined whether it is possible to sensitize colorectal tumour cells to TNF-alpha by modulation of NF-kappaB signalling.

RESULTS

We demonstrated that sustained NF-kappaB activation exceeding 16 h was observed in HRT18 and SW480 cells and was associated with TNF-alpha resistance. In contrast, transient NF-kappaB activation in HCT116 cells was associated with sensitivity to cytotoxic TNF-alpha effects, suggesting that NF-kappaB kinetics may have utility as clinical marker of TNF-alpha tumour resistance. Despite variable TNF-alpha responses and NF-kappaB kinetics, all three colorectal cancer cell lines were highly sensitive to treatment with the TNF-related apoptosis-inducing ligand (TRAIL) which induced only transient NF-kappaB activation. This further supports the notion of a pre-determined NF-kappaB response influencing receptor-mediated cell death. We also show that stable transfection and adenoviral-mediated expression of IkappaB(A32/36) can be used to confer TNF-alpha sensitivity to colorectal tumour cells previously resistant.

CONCLUSIONS

These findings indicate that a combined approach using gene therapy and recombinant TNF-alpha merits further appraisal. Furthermore, the kinetics of the TNF-alpha response could be determined using a 'test-dose' to indicate whether individual patients might benefit from this gene therapy approach.