Mutations in the adenomatous polyposis coli or ␤-catenin gene lead to cytosolic accumulation of ␤-catenin and, subsequently, to increased transcriptional activity of the ␤-catenin-T cell-factor/lymphoid-enhancer-factor complex. This process seems to play an essential role in the development of most colorectal carcinomas. To identify genes activated by ␤-catenin overexpression, we used colorectal cell lines for transfection with the ␤-catenin gene and searched for genes differentially expressed in the transfectants. There are four genes affected by ␤-catenin overexpression; three overexpressed genes code for two components of the AP-1 transcription complex, c-jun and fra-1, and for the urokinase-type plasminogen activator receptor (uPAR), whose transcription is activated by AP-1. The direct interaction of the ␤-catenin-T cell-factor͞lymphoid-enhancerfactor complex with the promoter region of c-jun and fra-1 was shown in a gel shift assay. The concomitant increase in ␤-catenin expression and the amount of uPAR was confirmed in primary colon carcinomas and their liver metastases at both the mRNA and the protein levels. High expression of ␤-catenin in transfectants, as well as in additionally analyzed colorectal cell lines, was associated with decreased expression of ZO-1, which is involved in epithelial polarization. Thus, accumulation of ␤-catenin indirectly affects the expression of uPAR in vitro and in vivo. Together with the other alterations, ␤-catenin accumulation may contribute to the development and progression of colon carcinoma both by dedifferentiation and through proteolytic activity.

Although APC mutations occur at a high frequency in colorectal cancers, few studies have performed a comprehensive analysis by screening the whole gene for mutations and assessing allelic loss. APC seems to act as a tumor-suppressor gene in a ''nonclassical'' fashion: data from familial adenomatous polyposis (FAP) show that the site of the germ-line mutation determines the type of ''second hit'' in FAP tumors, and simple protein inactivation is selected weakly, if at all. In this study, we screened the entire coding region of APC for mutations and assessed allelic loss in a set of 41 colorectal cancer cell lines. Of 41 cancers, 32 (83%) showed evidence of APC mutation and͞or allelic loss. We identified several APC mutations and found a ''hotspot'' for somatic mutation in sporadic colorectal tumors at codon 1,554. Our results suggest that APC mutations occur in the great majority of colorectal cancers, the exceptions almost all being RER؉ tumors, which may substitute for altered APC function by mutations in ␤-catenin and͞or at other loci. When combined with previously published data, our results show that there is interdependence of the ''two hits'' at APC in sporadic colorectal tumors as well as in FAP. APC mutations in the ''mutation cluster region,'' especially those close to codon 1,300, are associated with allelic loss, whereas tumors with mutations outside this region tend to harbor truncating mutations. The causes of this phenomenon are probably selection for retained N-terminal and lost C-terminal APC functions, effects on ␤-catenin levels, and APC protein stability.

ABSTRACT␤-catenin has functions as both an adhesion and a signaling molecule. Disruption of these functions through mutations of the ␤-catenin gene (CTNNB1) may be important in the development of colorectal tumors. We examined the entire coding sequence of ␤-catenin by reverse transcriptase-PCR (RT-PCR) and direct sequencing of 23 human colorectal cancer cell lines from 21 patients. In two cell lines, there was apparent instability of the ␤-catenin mRNA. Five different mutations (26%) were found in the remaining 21cell lines (from 19 patients). A three-base deletion (codon 45) was identified in the cell line HCT 116, whereas cell lines SW 48, HCA 46, CACO 2, and Colo 201 each contained single-base missense mutations (codons 33, 183, 245, and 287, respectively). All 23 cell lines had fulllength ␤-catenin protein that was detectable by Western blotting and that coprecipitated with E-cadherin. In three of the cell lines with CTNNB1 mutations, complexes of ␤-catenin with ␣-catenin and APC were detectable. In SW48 and HCA 46, however, we did not detect complexes of ␤-catenin protein with ␣-catenin and APC, respectively. These results show that selection of CTNNB1 mutations occurs in up to 26% of colorectal cancers from which cell lines are derived. In these cases, mutation selection is probably for altered ␤-catenin function, which may significantly alter intracellular signaling and intercellular adhesion and may serve as a complement to APC mutations in the early stages of tumorigenesis.

Heritable factors account for approximately 35% of colorectal cancer (CRC) risk, and almost 30% of the population in the UK have a family history of CRC. The quantification of an individual’s lifetime risk of gastrointestinal cancer may incorporate clinical and molecular data, and depends on accurate phenotypic assessment and genetic diagnosis. In turn this may facilitate targeted risk-reducing interventions, including endoscopic surveillance, preventative surgery and chemoprophylaxis, which provide opportunities for cancer prevention. This guideline is an update from the 2010 British Society of Gastroenterology/Association of Coloproctology of Great Britain and Ireland (BSG/ACPGBI) guidelines for colorectal screening and surveillance in moderate and high-risk groups; however, this guideline is concerned specifically with people who have increased lifetime risk of CRC due to hereditary factors, including those with Lynch syndrome, polyposis or a family history of CRC. On this occasion we invited the UK Cancer Genetics Group (UKCGG), a subgroup within the British Society of Genetic Medicine (BSGM), as a partner to BSG and ACPGBI in the multidisciplinary guideline development process. We also invited external review through the Delphi process by members of the public as well as the steering committees of the European Hereditary Tumour Group (EHTG) and the European Society of Gastrointestinal Endoscopy (ESGE). A systematic review of 10 189 publications was undertaken to develop 67 evidence and expert opinion-based recommendations for the management of hereditary CRC risk. Ten research recommendations are also prioritised to inform clinical management of people at hereditary CRC risk.

APC is often cited as a prime example of a tumor suppressor gene. Truncating germline and somatic mutations (or, infrequently, allelic loss) occur in tumors in FAP (familial adenomatous polyposis). Most sporadic colorectal cancers also have two APC mutations. Clues from attenuated polyposis, missense germline variants with mild disease and the somatic mutation cluster region (codons 1,250-1,450) indicate, however, that APC mutations might not result in simple loss of protein function. We have found that FAP patients with germline APC mutations within a small region (codons 1,194-1,392 at most) mainly show allelic loss in their colorectal adenomas, in contrast to other FAP patients, whose 'second hits' tend to occur by truncating mutations in the mutation cluster region. Our results indicate that different APC mutations provide cells with different selective advantages, with mutations close to codon 1,300 providing the greatest advantage. Allelic loss is selected strongly in cells with one mutation near codon 1,300. A different germline-somatic APC mutation association exists in FAP desmoids. APC is not, therefore, a classical tumor suppressor. Our findings also indicate a new mechanism for disease severity: if a broader spectrum of mutations is selected in tumors, the somatic mutation rate is effectively higher and more tumors grow.

ITTC, nSTAT1 and strong MHC class I expression on tumours identify patients with improved survival and an intact tumour immune system that may benefit from immunotherapy. Conversely, loss of these markers identifies patients whose tumours have escaped immunosurveillance and are unlikely to benefit from immunotherapy.

Abnormalities in the Wnt signalling pathway are found in a wide range of cancers. The diverse origin of these malignancies implies that the contribution that disrupted Wnt signalling makes to tumourigenesis is not limited to specific tissue types and thus can be regarded as a step which is 'generic' to the process of carcinogenesis. In recent years, rapid progress has been made in the understanding of the Wnt signalling pathway, giving an insight into how inappropriate activation of this pathway may facilitate the neoplastic conversion of a normal cell. Furthermore, elucidation of the mechanisms that regulate Wnt signalling has led to the possibility of manipulating these mechanisms in order to downregulate Wnt signalling in established tumours. In this review, the Wnt signalling pathway is described. The role of aberrant Wnt signalling in tumour development is discussed together with its clinical implications for anti-tumour therapy.

Classical familial adenomatous polyposis (FAP) is a high-penetrance autosomal dominant disease that predisposes to hundreds or thousands of colorectal adenomas and carcinoma and that results from truncating mutations in the APC gene. A variant of FAP is attenuated adenomatous polyposis coli, which results from germ-line mutations in the 5 and 3 regions of the APC gene. Attenuated adenomatous polyposis coli patients have ''multiple'' colorectal adenomas (typically fewer than 100) without the f lorid phenotype of classical FAP. Another group of patients with multiple adenomas has no mutations in the APC gene, and their phenotype probably results from variation at a locus, or loci, elsewhere in the genome. Recently, however, a missense variant of APC (I1307K) was described that confers an increased risk of colorectal tumors, including multiple adenomas, in Ashkenazim. We have studied a set of 164 patients with multiple colorectal adenomas and͞or carcinoma and analyzed codons 1263-1377 (exon 15G) of the APC gene for germ-line variants. Three patients with the I1307K allele were detected, each of Ashkenazi descent. Four patients had a germ-line E1317Q missense variant of APC that was not present in controls; one of these individuals had an unusually large number of metaplastic polyps of the colorectum. There is increasing evidence that there exist germ-line variants of the APC gene that predispose to the development of multiple colorectal adenomas and carcinoma, but without the f lorid phenotype of classical FAP, and possibly with importance for colorectal cancer risk in the general population.