Approximately 1-2% of colorectal cancers (CRC) arise because of germline mutations in DNA mismatch repair genes, referred to as Lynch syndrome. These tumours show microsatellite instability (MSI) and loss of expression of mismatch repair proteins. Presymptomatic identification of mutation carriers has been demonstrated to improve survival; however, there is concern that many are not being identified using current practices. We evaluated population-based MSI screening of CRC in young patients as a means of ascertaining mutation carriers. CRC diagnosed in patients aged <60 years were identified from pathology records. No prior information was available on family history of cancer. PCR techniques were used to determine MSI in the BAT-26 mononucleotide repeat and mutation in the BRAF oncogene. Loss of MLH1, MSH2, MSH6 and PMS2 protein expression was evaluated in MSI1 tumours by immunohistochemistry. MSI1 tumours were found in 105/1,344 (7.8%) patients, of which 7 were excluded as possible Lynch syndrome because of BRAF mutation. Of the 98 ''red flag'' cases that were followed up, 25 were already known as mutation carriers or members of mutation carrier families. Germline test results were obtained for 35 patients and revealed that 22 showed no apparent mutation, 11 showed likely pathogenic mutations and 2 had unclassified variants. The proportion of MSI1 cases in different age groups that were estimated to be mutation carriers was 89% (<30 years), 83% (30-39), 68% (40-49) and 17% (50-59). We recommend MSI as the initial test for population-based screening of Lynch syndrome in younger CRC patients, regardless of family history. ' 2008 Wiley-Liss, Inc.Key words: HNPCC; colorectal cancer; microsatellite instability; BRAF Hereditary non-polyposis colorectal cancer (HNPCC), or Lynch syndrome, is mainly caused by mutations in the DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2. 1,2 It accounts for approximately 1-2% of all colorectal cancers (CRC) and is also associated with an increased risk of endometrial and other extracolonic cancers. As a consequence of deficient MMR, almost all CRCs from patients with Lynch syndrome show microsatellite instability (MSI) in their tumour DNA. The MSI phenotype is characterized by ubiquitous changes in the length of nucleotide repeat sequences, with mononucleotide repeat tracts being particularly susceptible to deletions. 3 MSI is almost always accompanied by a loss of expression of MMR proteins. The most commonly observed combinations are loss of MLH1 with PMS2 and of MSH2 with MSH6, although other rarer patterns of loss have been reported. 4,5 Approximately 10% of sporadic CRCs also exhibit MSI and these tumours occur most frequently in the proximal colon of older women. 3 The large majority of sporadic MSI1 CRCs arise because of acquired, methylation-induced transcriptional silencing of MLH1 gene expression. 6 The MSI phenotype cannot therefore be used alone as a specific marker for Lynch syndrome. However, the presence of a hot-spot point mutation (V600E) in the BRAF onc...

Evidence that activating mutations of the KRAS oncogene abolish the response to anti-epidermal growth factor receptor therapy has revolutionized the treatment of advanced colorectal cancer. This has resulted in the urgent demand for KRAS mutation testing in the clinical setting to aid choice of therapy. The aim of this study was to evaluate six different KRAS mutation detection methodologies on two series of primary colorectal cancer samples. Two series of 80 frozen and 74 formalin-fixed paraffin-embedded tissue samples were sourced and DNA was extracted at a central site before distribution to seven different testing sites. KRAS mutations in codons 12 and 13 were assessed by using single strand conformation polymorphism analysis, pyrosequencing, high resolution melting analysis, dideoxy sequencing, or the commercially available TIB Molbiol (Berlin, Germany) or DxS Diagnostic Innovations (Manchester, UK) kits. In frozen tissue samples, concordance in KRAS status (defined as consensus in at least five assays) was observed in 66/80 (83%) cases. In paraffin tissue, concordance was 46/74 (63%) if all assays were considered or 71/74 (96%) using the five best performing assays. These results demonstrate that a variety of detection methodologies are suitable and provide comparable results for KRAS mutation analysis of clinical

The matrix metalloproteinases (MMPs) have been shown to play important roles in cancer progression. In this study we examined whether common genetic variants in two key MMPs are associated with phenotypic features of breast cancers and patient outcome. A single nucleotide polymorphism in the promoter region of MMP-2 (-1306 C-->T) abolishes Sp1 binding and is associated with lower transcriptional activity, while another in the promoter region of MMP-9 (-1562 C-->T) increases the transcription of this gene. MMP-2 TT homozygous patients had smaller tumors (p=0.006) and contained lower concentrations of estrogen receptor (ER; p=0.002) compared to patients with the MMP-2 CC or CT genotype. Homozygosity for the MMP-2 -1306 T allele was associated with markedly different patient survival depending upon tumor ER status. For patients with ER negative tumors, the MMP-2 TT genotype was associated with poor survival (2/8 patients alive at end of study, 25%) compared to the CC or CT genotypes (59/70, 84%; p < 0.001). For patients with ER positive tumors, the MMP-2 TT genotype was associated with a trend for very good survival (10/10, 100%) compared to the CC or CT genotypes (130/157, 83%; p=0.16). The MMP-9 -1562 T allele was associated with features of good prognosis including non-ductal type histology, positive ER status and the absence of TP53 mutation. Patients with MMP-9 -1562 CT or TT genotypes showed marginally better prognosis compared to CC homozygotes (p=0.06). These findings suggest that breast cancer phenotype and outcome can be influenced by common functional polymorphisms in MMP genes.

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