The DNA mismatch repair (MMR) pathway corrects specific types of DNA replication errors that affect microsatellites and thus is critical for maintaining genomic integrity. The genes of the MMR pathway are highly conserved across different organisms. Likewise, defective MMR function universally results in microsatellite instability (MSI) which is a hallmark of certain types of cancer associated with the Mendelian disorder hereditary nonpolyposis colorectal cancer. (Lynch syndrome). To identify previously unrecognized deleted genes or loci that can lead to MSI, we developed a functional genomics screen utilizing a plasmid containing a microsatellite sequence that is a host spot for MSI mutations and the comprehensive homozygous diploid deletion mutant resource for Saccharomyces cerevisiae. This pool represents a collection of non-essential homozygous yeast diploid (2N) mutants in which there are deletions for over four thousand yeast open reading frames (ORFs). From our screen, we identified a deletion mutant strain of the PAU24 gene that leads to MSI. In a series of validation experiments, we determined that this PAU24 mutant strain had an increased MSI-specific mutation rate in comparison to the original background wildtype strain, other deletion mutants and comparable to a MMR mutant involving the MLH1 gene. Likewise, in yeast strains with a deletion of PAU24, we identified specific de novo indel mutations that occurred within the targeted microsatellite used for this screen.

The pathogenesis of microsatellite stable hereditary non-polyposis colorectal cancers (MSS HNPCC) is unclear. To identify genomic regions that might be involved in MSS HNPCC pathogenesis, we selected 20 pairs of MSS HNPCC for a genome-wide study using copy number variation targeted (CNV-targeted) CytoScan HD Array. A remarkably increased frequency of 20q gain (70%) and high levels of copy-neutral loss of heterozygosity (40%) were observed. The most frequent tumor-specific CNVs included amplifications (7p21.3-15.1, 8q13.3-24.3, 13q14.1-33.3 and 20q12-13.33) and deletions (8p11.23-23.1, 15q11.2-26.1, 17p13.1-13.3 and 18q11.2-21.33). In addition, 10 novel CNVs were discovered and led to identification of WDR16 and RAPGEF5 as candidate genes involved in tumorigenesis, displaying a robust correlation between expression and genomic alterations. Moreover, WDR16 and RAPGEF5 exhibited altered protein expression levels as assessed by immunohistochemistry (IHC) in 41 other independent samples. Finally, high consistencies (68-84%) were observed between CNVs by Array and quantitative PCR. These findings are important for further elucidating MSS HNPCC pathogenesis.

Lynch syndrome is the most common inherited colon cancer susceptibility syndrome. Lynch syndrome is characterized by a significantly increased risk for colon cancer and endometrial cancer and a smaller risk for several other associated cancers. Some periodic screening strategies, such as colonoscopy, reduce the incidence and mortality of Lynch syndrome. The aim of this review is to discuss the risks, surveillance tests and guidelines for the management of colonic and extracolonic tumors associated with Lynch syndrome. For extracolonic cancer, a benefit of surveillance is evident only for endometrial cancer. No definitive data show efficacy of chemopreventive drugs, although aspirin is a promising drug. In this review, the available evidence on the different screening strategies in Lynch syndrome will be discussed. Furthermore, the clinical and biological characteristics of this disease and their potential impact on prevention in individuals at risk are analyzed.

Observational studies report that higher intake of dietary fibre (a heterogeneous mix including non-starch polysaccharides and resistant starches) is associated with reduced risk of colorectal cancer, but no randomised trials with prevention of colorectal cancer as a primary endpoint have been done. We assessed the effect of resistant starch on the incidence of colorectal cancer.In the CAPP2 study, individuals with Lynch syndrome were randomly assigned in a two-by-two factorial design to receive 600 mg aspirin or aspirin placebo or 30 g resistant starch or starch placebo, for up to 4 years. Randomisation was done with a block size of 16. Post-intervention, patients entered into double-blind follow-up; participants and investigators were masked to treatment allocation. The primary endpoint for this analysis was development of colorectal cancer in participants randomly assigned to resistant starch or resistant-starch placebo with both intention-to-treat and per-protocol analyses. This study is registered, ISRCTN 59521990.463 patients were randomly assigned to receive resistant starch and 455 to receive resistant-starch placebo. At a median follow-up 52·7 months (IQR 28·9-78·4), 53 participants developed 61 primary colorectal cancers (27 of 463 participants randomly assigned to resistant starch, 26 of 455 participants assigned to resistant-starch placebo). Intention-to-treat analysis of time to first colorectal cancer showed a hazard ratio (HR) of 1·40 (95% CI 0·78-2·56; p=0·26) and Poisson regression accounting for multiple primary events gave an incidence rate ratio (IRR) of 1·15 (95% CI 0·66-2·00; p=0·61). For those completing 2 years of intervention, per-protocol analysis yielded a HR of 1·09 (0·55-2·19, p=0·80) and an IRR of 0·98 (0·51-1·88, p=0·95). No information on adverse events was gathered during post-intervention follow-up.Resistant starch had no detectable effect on cancer development in carriers of hereditary colorectal cancer. Dietary supplementation with resistant starch does not emulate the apparently protective effect of diets rich in dietary fibre against colorectal cancer.European Union, Cancer Research UK, Bayer Corporation, National Starch and Chemical Co, UK Medical Research Council, Newcastle Hospitals Trustees, Cancer Council of Victoria Australia, THRIPP South Africa, The Finnish Cancer Foundation, SIAK Switzerland, and Bayer Pharma.

Some single-nucleotide polymorphisms are associated with higher risk of colorectal cancer development and are suggested to explain part of the genetic contribution to Lynch syndrome. Aim: To evaluate the mutL homolog 1 (MLH1) I219V polymorphism in 124 unrelated South American individuals suspected of having Lynch syndrome, based on frequency, association with pathogenic MLH1 and mutS homolog 2 (MSH2) mutation and clinical features.DNA was obtained from peripheral blood and polymerase chain reaction (PCR) was performed, followed by direct sequencing.The Val allelic of the I219V polymorphism was found in 51.61% (64/124) of the individuals, with an allelic frequency of 0.3. MLH1 or MHS2 pathogenic mutations were found in 32.81% (21/64) and in 23.33% (14/60) of Val-carriers and non-carriers, respectively.The Val-carrying genotype was frequent in the studied population; however, it does not appear to exert any modifier effect on MLH1 or MSH2 pathogenic mutations and the development of colorectal cancer.

An overview of colorectal cancer discussed (Philip Paty) the good outcome after primary management with local control in 90-95 % of colon and 85 % in rectal cancer patients with major progression to metastases and to death related to hematogenous dissemination. The major disease pathways include the APC, aneuploid pathway involving mutations of P53, KRAS, SMAD 4, or the CMP/MSI pathway, mismatched repair defect as characterized by Lynch syndrome, the major hereditary form which may also have KRAS and P53 mutations. The common sporadic colorectal cancers are MS1 high, with many patients having BRAF and KRAS mutations. The sentinel node biopsy in colorectal cancer surgery may provide more definitive staging and perhaps modification of the extent of resection with better outcome as suggested by Dr. Saha. The identification of sentinel lymph nodes outside of the planned bowel resection may increase the resection biologically indicated by the sentinel lymph node location leading to better outcome. In a small study by Dr. Saha, the operation was enhanced in 21 % by extending the length of bowel resection, which increased node recovery to 18.5 nodes versus 12 nodes with the more conventional resection, increasing nodal recovery, and positivity to 60 % with reduction to five year recurrence rate to 9 % versus 27 % with the conventional resection. A new (Swiss) technique for pathologic node examination, the OSNA (the One Step Nucleic Acid diagnostic system), was presented which demonstrated increased detection of micro-metastases in a focused pathology study of 22 patients (Zuber) to 11 out of 15 patients versus the 7 micro-metastases identified by the standard single slide per node, and compared to 14 out of 15 with an intensive multi-slide technique. This suggests value in pursuing OSNA study by other centers with relevant clinical trials to establish its true value. An analysis of liver resection for metastatic colorectal cancer (CRC) emphasized the value of 10-year follow-up (DeAngelica). The 10-year survival of 102 patients among 612 patients was 17 % (Memorial Sloan Kettering data). At the five-year point 99 of 102 survivors were NED and 86 have been free of disease since the resection. The usual five-year figure after hepatic resection reveals that one-third of five-year survivors die from recurrence of distant disease suggesting the value of longer term follow-up in these patients. An additional question reviewed related to the role of neoadjuvant systemic chemotherapy (with response rates in the 50 % range) to produce down staging of the hepatic metastases and allow one to retrieve these patients with possible residual disease. In a series of 116 patients who had hepatic resection of CRC metastases in presence of regional node metastases, post neoadjuvant chemotherapy (normally not candidates for resection) these patients were demonstrated to have a 95 % recurrence at median time of 9 months. This raises a cautionary note to the literature report of five-year survivals in the 20-30 % range for hepatic metastases in presence of extra hepatic disease. Such may reflect patient selection rather than a true measure of the biology of disease, and warrant clinical trial evaluation. Lastly, regional therapy and overall systemic therapy were addressed by Dr. Kemeny. The CALGB study of hepatic artery infusion (HAI) with FUDR, dexamethasone versus 5FU leucovorin showed an overall survival of 24.4 months with HAI versus 20 months with systemic therapy (P = 0.0034). An adjuvant trial of HAI at MSK in 156 patients showed an overall survival benefit at 2 year and recent long term 10yr follow-up showing a significant overall survival of 41 % with HAI versus 27 % with systemic therapy (5FU leucovorin). In the neoadjuvant Nordlinger trial for hepatic metastases, there was a significant outcome differences-the preoperative therapy group had 9.2 % increase of progression free survival versus the surgery alone group which suggests the value of combining neoadjuvant surgery in good risk liver resection candidates. Conclude the final lesson from this well presented mini symposium confirms the need for continued evaluation of the numerous discussion points by clinical trial.

Early-onset colorectal cancer (CRC) represents a clinically distinct form of CRC that is often associated with a poor prognosis. Methylation levels of genomic repeats such as LINE-1 elements have been recognized as independent factors for increased cancer-related mortality. The methylation status of LINE-1 elements in early-onset CRC has not been analyzed previously.We analyzed 343 CRC tissues and 32 normal colonic mucosa samples, including 2 independent cohorts of CRC diagnosed ≤ 50 years old (n=188), a group of sporadic CRC >50 years (MSS n=89; MSI n=46), and a group of Lynch syndrome CRCs (n=20). Tumor mismatch repair protein expression, microsatellite instability status, LINE-1 and MLH1 methylation, somatic BRAF V600E mutation, and germline MUTYH mutations were evaluated.Mean LINE-1 methylation levels (± SD) in the five study groups were early-onset CRC, 56.6% (8.6); sporadic MSI, 67.1% (5.5); sporadic MSS, 65.1% (6.3); Lynch syndrome, 66.3% (4.5) and normal mucosa, 76.5% (1.5). Early-onset CRC had significantly lower LINE-1 methylation than any other group (p<0.0001). Compared to patients with <65% LINE-1 methylation in tumors, those with ≥ 65% LINE-1 methylation had significantly better overall survival (p=0.026, log rank test).LINE-1 hypomethylation constitutes a potentially important feature of early-onset CRC, and suggests a distinct molecular subtype. Further studies are needed to assess the potential of LINE-1 methylation status as a prognostic biomarker for young people with CRC.

Lynch syndrome (LS), or hereditary nonpolyposis colorectal cancer, is caused by mutations in mismatch repair (MMR) genes. An increased risk for upper tract urothelial carcinoma (UTUC) has been described in this population; however, data regarding the risk for bladder cancer (BCa) are sparse.To assess the risk of BCa in MMR mutation carriers and suggest screening and management recommendations.Cancer data from 1980 to 2007 were obtained from the Familial Gastrointestinal Cancer Registry in Toronto for 321 persons with known MMR mutations: mutL homolog 1, colon cancer, nonpolyposis type 2 (E. coli) (MLH1); mutS homolog 2, colon cancer, nonpolyposis type 1 (E. coli) (MSH2); mutS homolog 6 (E. coli) (MSH6); and PMS2 postmeiotic segregation increased 2 (S. cerevisiae) (PMS2). OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Standardized incidence ratios from the Ontario Cancer Registry, using the Surveillance Epidemiology and End Results public database, were used to compare cancer risk in patients with MMR mutations with the Canadian population. Microsatellite instability analysis and immunohistochemistry (IHC) of the MMR proteins were also performed and the results compared with matched sporadic bladder tumors.Eleven of 177 patients with MSH2 mutations (6.21%, p<0.001 compared with the Canadian population) were found to have BCa, compared with 3 of 129 patients with MLH1 mutations (2.32%, p>0.05). Of these 11 tumors, 81.8% lacked expression of MSH2 on IHC, compared with the matched sporadic cases, which all displayed normal expression of MSH2 and MLH1. The incidence of UTUC among MSH2 carriers was 3.95% (p<0.001), and all tumors were found to be deficient in MSH2 expression on IHC. Mutations in the intron 5 splice site and exon 7 of the MSH2 gene increased the risk of urothelial cancer. Limitations include possible inflated risk estimates due to ascertainment bias.LS patients with MSH2 mutations are at an increased risk for not only UTUC but also BCa and could be offered appropriate screening.