Genetic analysis of an inherited predisposition to colon cancer in a family with a variable number of adenomatous polyps

The E3 ligase HUWE1 increases the sensitivity of CRC to oxaliplatin through TOMM20 degradation

Continuous administration of oxaliplatin, the most widely used first-line chemotherapy drug for colorectal cancer (CRC), eventually leads to drug resistance. Increasing the sensitivity of CRC cells to oxaliplatin is a key strategy to overcome this issue. Impairment of mitochondrial function is a pivotal mechanism determining the sensitivity of CRC to oxaliplatin. We discovered an inverse correlation between Translocase of Outer Mitochondrial Membrane 20 (TOMM20) and oxaliplatin sensitivity as well as an inverse relationship between TOMM20 and HECT, UBA, and WWE domain containing E3 ligase 1 (HUWE1) expression in CRC. For the first time, we demonstrated that HUWE1 ubiquitinates TOMM20 directly and also regulates TOMM20 degradation via the PARKIN-mediated pathway. Furthermore, we showed that overexpression of HUWE1 in CRC cells has a negative effect on mitochondrial function, including the generation of ATP and maintenance of mitochondrial membrane potential, leading to increased production of ROS and apoptosis. This effect was amplified when cells were treated simultaneously with oxaliplatin. Our study conclusively shows that TOMM20 is a novel target of HUWE1. Our findings indicate that HUWE1 plays a critical role in regulating oxaliplatin sensitivity by degrading TOMM20 and inducing mitochondrial damage in CRC.

Mouse models in colon cancer, inferences, and implications

Mouse models of colorectal cancer (CRC) have been crucial in the identification of the role of genes responsible for the full range of pathology of the human disease and have proved to be dependable for testing anti-cancer drugs. Recent research points toward the relevance of tumor, angiogenic, and immune microenvironments in CRC progression to late-stage disease, as well as the treatment of it. This study examines important mouse models in CRC, discussing inherent strengths and weaknesses disclosed during their construction. It endeavors to provide both a synopsis of previous work covering how investigators have defined various models and to evaluate critically how researchers are most likely to use them in the future. Accumulated evidence regarding the metastatic process and the hope of using checkpoint inhibitors and immunological inhibitor therapies points to the need for a genetically engineered mouse model that is both immunocompetent and autochthonous.

Pancreatic Tumorigenesis: Precursors, Genetic Risk Factors and Screening

Pancreatic cancer (PC) is a highly malignant and aggressive tumor. Despite medical advancement, the silent nature of PC results in only 20% of all cases considered resectable at the time of diagnosis. It is projected to become the second leading cause in 2030. Most pancreatic cancer cases are diagnosed in the advanced stages. Such cases are typically unresectable and are associated with a 5-year survival of less than 10%. Although there is no guideline consensus regarding recommendations for screening for pancreatic cancer, early detection has been associated with better outcomes. In addition to continued utilization of imaging and conventional tumor markers, clinicians should be aware of novel testing modalities that may be effective for early detection of pancreatic cancer in individuals with high-risk factors. The pathogenesis of PC is not well understood; however, various modifiable and non-modifiable factors have been implicated in pancreatic oncogenesis. PC detection in the earlier stages is associated with better outcomes; nevertheless, most oncological societies do not recommend universal screening as it may result in a high false-positive rate. Therefore, targeted screening for high-risk individuals represents a reasonable option. In this review, we aimed to summarize the pathogenesis, genetic risk factors, high-risk population, and screening modalities for PC.

Evolutionary Origins of Metabolic Reprogramming in Cancer

Metabolic changes that facilitate tumor growth are one of the hallmarks of cancer. These changes are not specific to tumors but also take place during the physiological growth of tissues. Indeed, the cellular and tissue mechanisms present in the tumor have their physiological counterpart in the repair of tissue lesions and wound healing. These molecular mechanisms have been acquired during metazoan evolution, first to eliminate the infection of the tissue injury, then to enter an effective regenerative phase. Cancer itself could be considered a phenomenon of antagonistic pleiotropy of the genes involved in effective tissue repair. Cancer and tissue repair are complex traits that share many intermediate phenotypes at the molecular, cellular, and tissue levels, and all of these are integrated within a Systems Biology structure. Complex traits are influenced by a multitude of common genes, each with a weak effect. This polygenic component of complex traits is mainly unknown and so makes up part of the missing heritability. Here, we try to integrate these different perspectives from the point of view of the metabolic changes observed in cancer.

Statin Treatment as a Targeted Therapy for APC-Mutated Colorectal Cancer

Background

Mutations in the tumor suppressor gene Adenomatous Polyposis Coli (APC) are found in 80% of sporadic colorectal cancer (CRC) tumors and are also responsible for the inherited form of CRC, Familial adenomatous polyposis (FAP).

Methods

To identify novel therapeutic strategies for the treatment of APC mutated CRC, we generated a drug screening platform that incorporates a human cellular model of APC mutant CRC using CRISPR-cas9 gene editing and performed an FDA-approved drug screen targeting over 1000 compounds.

Results

We have identified the group of HMG-CoA Reductase (HMGCR) inhibitors known as statins, which cause a significantly greater loss in cell viability in the APC mutated cell lines and in in vivo APC mutated patient derived xenograft (PDX) models, compared to wild-type APC cells. Mechanistically, our data reveals this new synthetic lethal relationship is a consequence of decreased Wnt signalling and, ultimately, a reduction in the level of expression of the anti-apoptotic protein Survivin, upon statin treatment in the APC-mutant cells only. This mechanism acts via a Rac1 mediated control of beta-catenin.

Conclusion

Significantly, we have identified a novel synthetic lethal dependence between APC mutations and statin treatment, which could potentially be exploited for the treatment of APC mutated cancers.

From APC to the genetics of hereditary and familial colon cancer syndromes

Hereditary colorectal cancer (CRC) syndromes attributable to high penetrance mutations represent 9-26% of young-onset CRC cases. The clinical significance of many of these mutations is understood well enough to be used in diagnostics and as an aid in patient care. However, despite the advances made in the field, a significant proportion of familial and early-onset cases remains molecularly uncharacterized and extensive work is still needed to fully understand the genetic nature of CRC susceptibility. With the emergence of next-generation sequencing and associated methods, several predisposition loci have been unraveled, but validation is incomplete. Individuals with cancer-predisposing mutations are currently enrolled in life-long surveillance, but with the development of new treatments, such as cancer vaccinations, this might change in the not so distant future for at least some individuals. For individuals without a known cause for their disease susceptibility, prevention and therapy options are less precise. Herein, we review the progress achieved in the last three decades with a focus on how CRC predisposition genes were discovered. Furthermore, we discuss the clinical implications of these discoveries and anticipate what to expect in the next decade.

Candidate Gene Discovery in Hereditary Colorectal Cancer and Polyposis Syndromes-Considerations for Future Studies

To discover novel high-penetrant risk loci for hereditary colorectal cancer (hCRC) and polyposis syndromes many whole-exome and whole-genome sequencing (WES/WGS) studies have been performed. Remarkably, these studies resulted in only a few novel high-penetrant risk genes. Given this observation, the possibility and strategy to identify high-penetrant risk genes for hCRC and polyposis needs reconsideration. Therefore, we reviewed the study design of WES/WGS-based hCRC and polyposis gene discovery studies (n = 37) and provide recommendations to optimize discovery and validation strategies. The group of genetically unresolved patients is phenotypically heterogeneous, and likely composed of distinct molecular subtypes. This knowledge advocates for the screening of a homogeneous, stringently preselected discovery cohort and obtaining multi-level evidence for variant pathogenicity. This evidence can be collected by characterizing the molecular landscape of tumors from individuals with the same affected gene or by functional validation in cell-based models. Together, the combined approach of a phenotype-driven, tumor-based candidate gene search might elucidate the potential contribution of novel genetic predispositions in genetically unresolved hCRC and polyposis.

Effect of Adenomatous Polyposis Coli Loss on Tumorigenic Potential in Pancreatic Ductal Adenocarcinoma

Loss of the Adenomatous Polyposis Coli (APC) tumor suppressor in colorectal cancer elicits rapid signaling through the Wnt/β-catenin signaling pathway. In contrast to this well-established role of APC, recent studies from our laboratory demonstrated that APC functions through Wnt-independent pathways to mediate in vitro and in vivo models of breast tumorigenesis. Pancreatic ductal adenocarcinoma (PDAC) has an overall median survival of less than one year with a 5-year survival rate of 7.2%. APC is lost in a subset of pancreatic cancers, but the impact on Wnt signaling or tumor development is unclear. Given the lack of effective treatment strategies for pancreatic cancer, it is important to understand the functional implications of APC loss in pancreatic cancer cell lines. Therefore, the goal of this project is to study how APC loss affects Wnt pathway activation and in vitro tumor phenotypes. Using lentiviral shRNA, we successfully knocked down APC expression in six pancreatic cancer cell lines (AsPC-1, BxPC3, L3.6pl, HPAF-II, Hs 766T, MIA PaCa-2). No changes were observed in localization of β-catenin or reporter assays to assess β-catenin/TCF interaction. Despite this lack of Wnt/β-catenin pathway activation, the majority of APC knockdown cell lines exhibit an increase in cell proliferation. Cell migration assays showed that the BxPC-3 and L3.6pl cells were impacted by APC knockdown, showing faster wound healing in scratch wound assays. Interestingly, APC knockdown had no effect on gemcitabine treatment, which is the standard care for pancreatic cancer. It is important to understand the functional implications of APC loss in pancreatic cancer cells lines, which could be used as a target for therapeutics.

Prevalence of Germline Mutations in Polyposis and Colorectal Cancer-Associated Genes in Patients With Multiple Colorectal Polyps

BACKGROUND AND AIMS

Guidelines recommend genetic testing of patients with 10 or more cumulative adenomatous polyps. However, little is known about the utility of these tests-especially for older patients. We aimed to determine the prevalence of pathogenic mutations in patients with multiple colorectal polyps, stratified by age.

METHODS

We performed a cross-sectional study of patients with 10 or more colorectal polyps who underwent multigene panel testing (MGPT) from March 2012 through December 2016 (n = 3789). Demographic, clinical and family history data were obtained from test requisition forms and accompanying clinic notes, pedigrees, and pathology reports. Subjects were stratified based on reported polyp histology. Primary outcomes of interest were gene mutations associated with adenomatous polyposis, hamartomatous polyposis, and non-polyposis colorectal cancer syndromes.

RESULTS

Based on MGPT, the prevalence of mutations in adenomatous polyposis genes decreased with increasing age in all polyp count groups in the adenoma cohort (P < .001 for 10-19, 20-99, and 100 or more polyps). The prevalence of mutations in all genes of interest also decreased with increasing age but remained above 5% in all age and polyp cohorts. Increased age at testing was associated with a significantly lower risk of a mutation in any gene of interest with multivariate analysis. In the hamartoma cohort, the prevalence of mutations in hamartomatous polyposis genes was high regardless of polyp count (40% with 10-19 polyps, 72.1% with 20-99 polyps, and 50% with 100 or more polyps).

CONCLUSION

Our findings support continued genetic testing of patients with 10 or more polyps including adenomas and/or hamartomas. MGPT that includes analysis of polyposis and non-polyposis colorectal cancer genes should be considered for these patients given the high proportion with mutations (above 5%) in all age groups.

Missing heritability of complex diseases: Enlightenment by genetic variants from intermediate phenotypes

Diseases of complex origin have a component of quantitative genetics that contributes to their susceptibility and phenotypic variability. However, after several studies, a major part of the genetic component of complex phenotypes has still not been found, a situation known as "missing heritability." Although there have been many hypotheses put forward to explain the reasons for the missing heritability, its definitive causes remain unknown. Complex diseases are caused by multiple intermediate phenotypes involved in their pathogenesis and, very often, each one of these intermediate phenotypes also has a component of quantitative inheritance. Here we propose that at least part of the missing heritability can be explained by the genetic component of intermediate phenotypes that is not detectable at the level of the main complex trait. At the same time, the identification of the genetic component of intermediate phenotypes provides an opportunity to identify part of the missing heritability of complex diseases.

Evidence for a genetical contribution to non-smoking-related lung cancer

BACKGROUND

The majority of lung cancers are smoking-related, with environmental and genetical factors contributing. The interplay between environmental and genetical contributions in non-smoking-related lung cancers is less clear.

METHODS

We analysed a population-based computerised genealogy resource linked to a state-wide cancer registry of lung cancer cases (n=5544) for evidence of a genetical contribution to lung cancer predisposition in smoking (n=1747) and non-smoking cases (n=784). Statistical methods were used to test for significant excess relatedness of cases and estimate relative risk (RR) in close and distant relatives of lung cancer cases.

RESULTS

Significant excess relatedness was observed for all lung cancer cases (p<0.001) and for the subsets of smoking-related (p<0.001) and non-smoking-related (p<0.001) cases when all pairwise relationships were considered. Only the non-smoking-related subset of cases showed significant excess relatedness when close relationships were ignored (p=0.020). First-degree, second-degree, and fourth-degree relatives of non-smoking-related lung cancer cases had significantly elevated RR. An even higher elevated RR was observed for first-degree, second-degree, third-degree and fourth-degree relatives of smoking-related lung cancer cases.

CONCLUSIONS

Non-smoking-related lung cancer cases show significant excess relatedness for close and distant relationships, providing strong evidence for a genetical contribution as well as an environmental contribution. Significant excess relatedness for only close family relationships in all lung cancer cases and in only smoking-related lung cancer cases implies environmental contribution. Additionally, the highest RR for lung cancer was observed in the relatives of smoking-related lung cancer, suggesting predisposition gene carriers who smoke are at highest risk for lung cancer. Screening and gene identification should focus on high-risk pedigrees.

The genetic basis of familial adenomatous polyposis and its implications for clinical practice and risk management

Familial adenomatous polyposis (FAP) is an inherited disorder that represents the most common gastrointestinal polyposis syndrome. Germline mutations in the APC gene were initially identified as responsible for FAP, and later, several studies have also implicated the MUTYH gene as responsible for this disease, usually referred to as MUTYH-associated polyposis (MAP). FAP and MAP are characterized by the early onset of multiple adenomatous colorectal polyps, a high lifetime risk of colorectal cancer (CRC), and in some patients the development of extracolonic manifestations. The goal of colorectal management in these patients is to prevent CRC mortality through endoscopic and surgical approaches. Individuals with FAP and their relatives should receive appropriate genetic counseling and join surveillance programs when indicated. This review is focused on the description of the main clinical and genetic aspects of FAP associated with germline APC mutations and MAP.

Hereditary and common familial colorectal cancer: evidence for colorectal screening

Colorectal cancer (CRC) is the fourth most common cancer among men and women. Between 3 and 6% of all CRCs are attributed to well-defined inherited syndromes, including Lynch syndrome, familial adenomatous polyposis, MUTYH-associated polyposis and several hamartomatous conditions. Up to 30% of CRC cases exhibit common familial risk, likely related to a combination of inherited factors and environment. Identification of these patients through family history and appropriate genetic testing can provide estimates of cancer risk that inform appropriate cancer screening, surveillance and/or preventative interventions. This article examines the colon cancer syndromes, their genetic basis, clinical management and evidence supporting colorectal screening. It also deals with the category of common (non-syndromic) familial risk including risk determination and screening guidelines.

Polymorphisms in nucleotide excision repair genes and susceptibility to colorectal cancer in the Polish population

Xeroderma pigmentosum (XP) is a rare autosomal recessive disease that is associated with a severe deficiency in nucleotide excision repair. Genetic polymorphisms in XP genes may be associated with a change in DNA repair capacity, which could be associated with colorectal cancer development. We assessed the association between 94 single nucleotide polymorphisms (SNPs) within seven XP genes (XPA-XPG) and the colorectal cancer risk in the Polish population. We genotyped 758 unselected patients with colorectal cancer and 1,841 healthy adults. We found that a significantly decreased risk of colorectal cancer was associated with XPC polymorphism rs2228000_CT genotype (OR 0.59; p < 0.0001) and the rs2228000_TT genotype (OR 0.29; p < 0.0001) compared to the reference genotype (CC). And an increased disease risk was associated with the XPD SNP, rs1799793_AG genotype (OR 1.44, p = 0.018) and rs1799793_AA genotype (OR 3.31, p < 0.0001) compared to the reference genotype. Haplotype analysis within XPC, XPD and XPG revealed haplotypes associated with an altered colorectal cancer risk. Stratified analysis by gender showed differences between the association of three SNPs: XPC rs2228000, XPD rs1799793 and XPD rs238406 in females and males. Association analysis between age of disease onset and polymorphisms in XPD (rs1799793) and XPC (rs2228000) revealed differences in the prevalence of these variants in patients under and over 50 years of age. Our results confirmed that polymorphisms in XPC and XPD may be associated with the risk of colorectal cancer.

Recurrent desmoids determine outcome in patients with Gardner syndrome: a cohort study of three generations of an APC mutation-positive family across 30 years

PURPOSE

Screening of Gardner syndrome (GS) patients is tailored towards prevention of colorectal cancer (CRC). However, many patients suffer from desmoid tumors, which are challenging to treat due to invasive growth and local recurrence. The aims of our study were to determine the effectiveness of screening in GS and analyze outcome of desmoid tumors by treatment modality.

METHODS

This was a cohort study of a family of 105 descendants with GS. All family members who agreed were screened by endoscopy, and colorectal resection was performed upon pending malignancy. Resectable desmoids were excised, whereas large tumors were treated by a combination of brachytherapy (BT) and radiotherapy (RT). Main outcome measures were the incidence of CRC and overall and disease-specific mortality (ClinicalTrial.gov ID NCT01286662).

RESULTS

Thirty-seven of 105 family members have GS. Preventive colorectal resections were performed in 16 patients (15 %), with one death due to gastric cancer. In four patients who denied screening endoscopy, invasive tumors of the colon (three patients) and stomach developed. Of 33 desmoid tumors, 10 (30 %) were located in the mesentery, 17 (52 %) in the abdominal wall, and 6 (18 %) in extra-abdominal sites. Excision of 12 desmoids was performed in eight patients. Four desmoids were treated by BT and RT and showed full or partial remission.

CONCLUSIONS

Provided adequate screening, good long-term control of colorectal tumors is achievable. However, desmoid tumors determine survival and quality of life in many patients. Our data suggest good local control using a combination of brachytherapy/radiotherapy in large desmoids unsuitable for surgical resection.

Inflammatory bowel disease and familial adenomatous polyposis

BACKGROUND

Inflammatory bowel disease (IBD) and familial adenomatous polyposis (FAP) are uncommon diseases and both are associated with marked increased risk of colorectal cancer.

METHODS

We present a patient diagnosed in parallel with ulcerative colitis and FAP. Mutational analysis of the APC germline and somatic DNA was performed by sequencing.

RESULTS

This patient's phenotype consisted of polyps only on the right side of the colon (cecum and ascending colon) whereas the area affected by ulcerative colitis (descending colon and rectum) was free of polyps on endoscopy and microscopic adenomas on histology. This raises the possibility that mosaicism or inflammation in the presence of active ulcerative colitis modified the phenotypic expression of adenomatous polyposis in the left colon. Mosaicism was excluded by DNA analysis.

DISCUSSION

This case of a patient diagnosed with both inflammatory bowel disease and familial adenomatous polyposis offers potential insights into the distinct pathogenesis of cancer susceptibility within these syndromes, and suggests that a collision of phenotypes may influence their mutual presentation. Both of these conditions independently increase the risk of colorectal cancer.

Cancer Stem Cells in Colorectal Cancer: Genetic and Epigenetic Changes

Colorectal cancer (CRC), an age-related disease, is the third most common cancer in the world. Although sporadic CRC, that affects 80-85% of CRC patients, is a multi-step process initiated by APC gene mutation, it is becoming increasingly evident that a small sub-population of cells termed cancer stem/stem-like cells (CSCs/CSLCs) plays critical roles in the progression of this malignancy specially the recurrence and drug resistance. The current review will summarize genetic and epigenetic changes observed at different stages in the progression of sporadic CRC. In addition, roles of miRNAs that control gene expression and CSCs/CSLCs in regulating proliferation, differentiation, and survival of the colon cancer cells will be summarized.

The genetics of cancer risk

One hundred years ago, decades before the discovery of the structure of DNA, debate raged regarding how human traits were passed from one generation to the next. Phenotypes, including risk of disease, had long been recognized as having a familial component. Yet it was difficult to reconcile genetic segregation as described by Mendel with observations exhaustively documented by Karl Pearson and others regarding the normal distribution of human characteristics. In 1918, R. A. Fisher published his landmark article, "The Correlation Between Relatives on the Supposition of Mendelian Inheritance," bridging this divide and demonstrating that multiple alleles, all individually obeying Mendel's laws, account for the phenotypic variation observed in nature.Since that time, geneticists have sought to identify the link between genotype and phenotype. Trait-associated alleles vary in their frequency and degree of penetrance. Some minor alleles may approach a frequency of 50% in the human population, whereas others are present within only a few individuals. The spectrum for penetrance is similarly wide. These characteristics jointly determine the segregation pattern of a given trait, which, in turn, determine the method used to map the trait. Until recently, identification of rare, highly penetrant alleles was most practical. Revolutionary studies in genomics reported over the past decade have made interrogation of most of the spectrum of genetic variation feasible.The following article reviews recent discoveries in the genetic basis of inherited cancer risk and how these discoveries inform cancer biology and patient management. Although this article focuses on prostate cancer, the principles are generic for any cancer and, indeed, for any trait.

Genotype-phenotype correlation in colorectal polyposis

Familial adenomatous polyposis (FAP) has been divided into three clinical subtypes: mild, classical and severe. This study aimed to investigate for a correlation between genotype and phenotype. A codon-specific survival difference is unknown. A retrospective longitudinal study of 492 patients on the Manchester Polyposis Registry was conducted. Patients were grouped according to genotypes: 0, unknown mutation; 1, adenomatous polyposis coli (APC) 0-178 (and 312-412 of exon 9); 2, APC >1550; 3, APC 179-1249; 4, APC 1250-1549; and 5, MutYH. Date of onset of polyposis, incidence of colorectal cancer (CRC), survival and actuarial time to surgery were calculated. Median age of onset of polyposis for genotype 0 was 20.3 years, genotype 1 35.6 years, genotype 2 32.2, genotype 3 15.9 years, and genotype 4 14.8 years (p < 0.0001). Age of onset of CRC was similar between genotypes. Median survival for genotype 0 was 56.6 years, genotype 1 74.9 years, genotype 2 61.0 years, genotype 3 63.0 years, genotype 4 48.1 years, and genotype 5 69.7 years (p = 0.003). This survival difference was also seen when patients who underwent screening and those who did not were analysed separately. Survival in the screened population was 53.9 years in genotype 4 and 72.9 years in genotype 3. Patients with genotype 4 (APC 1249-1549) have a significantly worse survival despite screening and early prophylactic surgery. This analysis supports a genotype-phenotype correlation. Patients with a mutation APC 1249-1549 develop polyposis at an early age and have a worse survival. Patients with a mutation APC 0-178 or 312-412 develop polyposis later and have an improved survival. This survival difference has not previously been documented.

[Colorectal polyposis syndrome: a guide to diagnosis]

Biopsies and resection specimens of the gastrointestinal tract are a major part of the routine workload in many histopathology departments, whereby polypoid lesions are generally the main focus. In addition to distinguishing non-neoplastic from neoplastic polyps and evaluating the grade of dysplasia of the latter, the pathologist should always consider the possibility of an underlying polyposis syndrome. Not only have additional hereditary polyposis syndromes been identified in recent years due to a better understanding of their genetic and epigenetic alterations but also knowledge on well known polyposes has improved, leading to subtyping of various forms according to their different genotype. It is essential for the histopathologist to understand that the conventional histomorphology of individual polyps combined with information on the number and distribution of these lesions and clinical data can provide clues regarding a possible hereditary background. Therefore, the correct histological assessment of polyps is not just about getting the diagnosis right, it might also lead to genetic screening of family members and spouses.

Colorectal adenomas and cancer link to chromosome 13q22.1-13q31.3 in a large family with excess colorectal cancer

BACKGROUND

Colorectal cancer is the fourth most common type of cancer and the second most common cause of cancer death. Fewer than 5% of colon cancers arise in the presence of a clear hereditary cancer condition; however, current estimates suggest that an additional 15-25% of colorectal cancers arise on the basis of unknown inherited factors.

AIM

To identify additional genetic factors responsible for colon cancer.

METHODS

A large kindred with excess colorectal cancer was identified through the Utah Population Database and evaluated clinically and genetically for inherited susceptibility.

RESULTS

A major genetic locus segregating with colonic polyps and cancer in this kindred was identified on chromosome 13q with a non-parametric linkage score of 24 (LOD score of 2.99 and p=0.001). The genetic region spans 21 Mbp and contains 27 RefSeq genes. Sequencing of all candidate genes in this region failed to identify a clearly deleterious mutation; however, polymorphisms segregating with the phenotype were identified. Chromosome 13q is commonly gained and overexpressed in colon cancers and correlates with metastasis, suggesting the presence of an important cancer progression gene. Evaluation of tumours from the kindred revealed a gain of 13q as well.

CONCLUSIONS

This identified region may contain a novel gene responsible for colon cancer progression in a significant proportion of sporadic cancers. Identification of the precise gene and causative genetic change in the kindred will be an important next step to understanding cancer progression and metastasis.

Impact of group IVA cytosolic phospholipase A2 gene polymorphisms on phenotypic features of patients with familial adenomatous polyposis

OBJECTIVE

Group IVA cytosolic phospholipase A(2) (cPLA(2)alpha) plays a key role in tumorigenesis via generating arachidonic acids as the substrate of cyclooxygenase. The aim of this study was to elucidate the possible associations between cPLA ( 2 )alpha gene polymorphisms and phenotypic features of patients with familial adenomatous polyposis (FAP).

PATIENTS AND METHODS

A tag single nucleotide polymorphisms (SNPs)-based genotype-phenotype association study of the cPLA ( 2 )alpha gene was conducted in 73 Japanese patients from 59 families with FAP. Based on the HapMap database, seven tag SNPs of the cPLA ( 2 )alpha gene were selected and genotyped by direct sequencing analysis. The genotype-phenotype association in relation to the adenomatous polyposis coli (APC) gene mutation was also assessed.

RESULTS

The single SNP analysis showed that rs3820185 C allele [odds ratio (OR), 2.5; 95% confidence interval (CI), 1.2-4.9] and rs127446200 GG genotype (OR, 10.9; 95%CI, 1.6-69.8), were more frequent in patients with gastric fundic gland polyposis (FGP) than in those without. Rs12749354 C allele was more frequently found in patients with small intestinal adenoma (OR, 7.0; 95% CI, 1.5-30.4; p = 0.008). This association was also significant when adjusted for covariates (age, sex, and APC mutation) in a logistic regression analysis (adjusted OR, 7.4; 95% CI, 1.2-64.2; p = 0.027).

CONCLUSIONS

The cPLA ( 2 )alpha gene may be a possible disease modifier gene in FAP.

Large intron 14 rearrangement in APC results in splice defect and attenuated FAP

Familial adenomatous polyposis [FAP (OMIM 175100)] is an autosomal dominant colorectal cancer predisposition syndrome characterized by hundreds to thousands of colonic polyps and, if untreated by a combination of screening and/or surgical intervention, an approximately 99% lifetime risk of colorectal cancer. A subset of FAP patients develop an attenuated form of the condition characterized by lower numbers of colonic polyps (highly variable, but generally less than 100) and a lower lifetime risk of colorectal cancer, on the order of 70%. We report the diagnosis of three attenuated FAP families due to a 1.4-kb deletion within intron 14 of APC, originally reported clinically as a variant of unknown significance (VUS). Sequence analysis suggests that this arose through an Alu-mediated recombination event with a locus on chromosome 6q22.1. This mutation is inherited by family members who presented with an attenuated FAP phenotype, with variable age of onset and severity. Sequence analysis of mRNA revealed an increase in the level of aberrant splicing of exon 14, resulting in the generation of an exon 13-exon 15 splice-form that is predicted to lead to a frameshift and protein truncation at codon 673. The relatively mild phenotypic presentation and the intra-familial variation are consistent with the leaky nature of exon 14 splicing in normal APC. The inferred founder of these three families may account for as yet undetected affected branches of this kindred. This and similar types of intronic mutations may account for a significant proportion of FAP cases where APC clinical analysis fails because of the current limitations of testing options.

The hMSH2 and hMLH1 genes in hereditary nonpolyposis colorectal cancer

Hereditary nonpolyposis colorectal cancer (HNPCC) is the most common inherited colorectal cancer predisposing condition. HNPCC is an important problem for the surgeon because up to 60% of carriers of mismatch repair (MMR) gene mutations develop colorectal cancer (CRC), commonly before age 50 years. When CRC is diagnosed, the surgeon is in the ideal position to order appropriate tumor testing for microsatellite instability or immunohistochemical stains for loss of MMR gene associated protein, if this has not already been done. This article reviews the history of HNPCC, its clinical features, gene discovery, development of clinical genetic workup, and clinical surveillance, with an emphasis on the two major HNPCC genes, hMSH2 and hMLH1. It is not always possible to discuss these specific genes without commenting on the broader problem of HNPCC diagnosis and management.

Realistic expectations of prepulse inhibition in translational models for schizophrenia research

INTRODUCTION

Under specific conditions, a weak lead stimulus, or "prepulse", can inhibit the startling effects of a subsequent intense abrupt stimulus. This startle-inhibiting effect of the prepulse, termed "prepulse inhibition" (PPI), is widely used in translational models to understand the biology of brainbased inhibitory mechanisms and their deficiency in neuropsychiatric disorders. In 1981, four published reports with "prepulse inhibition" as an index term were listed on Medline; over the past 5 years, new published Medline reports with "prepulse inhibition" as an index term have appeared at a rate exceeding once every 2.7 days (n=678). Most of these reports focus on the use of PPI in translational models of impaired sensorimotor gating in schizophrenia. This rapid expansion and broad application of PPI as a tool for understanding schizophrenia has, at times, outpaced critical thinking and falsifiable hypotheses about the relative strengths vs. limitations of this measure.

OBJECTIVES

This review enumerates the realistic expectations for PPI in translational models for schizophrenia research, and provides cautionary notes for the future applications of this important research tool.

CONCLUSION

In humans, PPI is not "diagnostic"; levels of PPI do not predict clinical course, specific symptoms, or individual medication responses. In preclinical studies, PPI is valuable for evaluating models or model organisms relevant to schizophrenia, "mapping" neural substrates of deficient PPI in schizophrenia, and advancing the discovery and development of novel therapeutics. Across species, PPI is a reliable, robust quantitative phenotype that is useful for probing the neurobiology and genetics of gating deficits in schizophrenia.

Colorectal polyposes: from phenotype to diagnosis

The colorectal polyposes are uncommon and frequently present diagnostic difficulties. Although the final diagnostic arbiter is the demonstration of a germline mutation, this may not always be demonstrable, and some forms of colorectal polyposis have no known genetic basis. Therefore, an accurate description of the phenotype by the pathologist is central to the establishment of a working diagnosis. This can direct the search for the underlying genetic cause (if any) and is also essential for establishing the magnitude of risk of colorectal malignancy for the patient and the patient's relatives. The pathologist may be provided with only a small and selected sample of endoscopically resected polyps or with prodigious numbers of polyps (too many to sample) when receiving a surgical specimen. Each type of polyposis presents its own particular diagnostic problems that may relate to polyp numbers, gross recognition of small or flat polyps, incomplete development of the full phenotype at the stage of investigation, and the histological classification of unusual or mixed polyps. The aim of this review is to highlight the principles and pitfalls in achieving a comprehensive description of the various types of colorectal polyposis, including classical FAP, attenuated FAP, MUTYH- (formerly MYH-) associated polyposis (MAP), other presentations of multiple adenomas, Peutz-Jeghers syndrome (P-JS), juvenile polyposis syndrome (JPS), Cowden syndrome (CS), hereditary mixed polyposis syndrome (HMPS), and hyperplastic polyposis syndrome (HPS).

American founder mutation for attenuated familial adenomatous polyposis

BACKGROUND & AIMS

Specific mutations in the adenomatous polyposis coli (APC) gene can lead to an attenuated form of familial adenomatous polyposis (AFAP). Although AFAP mutation carriers have a 69% risk of colorectal cancer by age 80, clinical recognition remains a challenge in some cases because they present with few colonic adenomas and are difficult to distinguish clinically from patients with sporadic polyps.

METHODS

Family relationships were established using family history reports, the Utah Population Database, and the public records of the Mormon Church. Genetic analysis of representative family members was performed using a 10,000 single nucleotide polymorphism array platform. Colonoscopy data were available on 120 individuals with the AFAP mutation.

RESULTS

Two large AFAP kindreds with the identical APC disease-causing mutation (c.426_427delAT) were linked to a founding couple who came to America from England around 1630. Genetic analysis showed that the 2 families share a conserved haplotype of 7.17 Mbp surrounding the mutant APC allele. The data show that 36.6% of the mutation-positive family members have fewer than 10 colonic adenomatous polyps, and 3 (6.8%) of these individuals were diagnosed with colorectal cancer.

CONCLUSIONS

In view of the apparent age of this mutation, a notable fraction of both multiple-adenoma patients and perhaps even colon cancer cases in the United States could be related to this founder mutation. The colon cancer risk associated with the mutation makes genetic testing of considerable importance in patients with a personal or family history of either colonic polyps or cancer at a young age.

Do we know all there is to know about Familial Adenomatous Polyposis?

Familial Adenomatous Polyposis (FAP) and Attenuated FAP (AFAP) are caused by a germline mutation in the Adenomatous polyposis coli (APC) gene. Recently, a new pathway characterized by a biallelic mutation in the MYH gene, with a recessive model of inheritance was discovered for this inherited syndrome. This report describes a Tunisian patient with an attenuated FAP phenotype, presenting seven colon polyps and an adenocarcinoma but no detectable germline mutations in the FAP target genes. A well known somatic mutation was found in the APC mutation cluster region (MCR). This case shows that further studies are needed to fully understand all the pathways of the FAP syndrome.

Gastrointestinal polyposes: clinical, pathological and molecular features

This article focuses mainly on noninflammatory epithelial polyposes, particularly the diagnostically important morphological and molecular features of the more recently recognized and/or more poorly understood conditions. One of the most important, but often neglected, of these is hyperplastic polyposis.

Deletion mutation of BRAF in a serrated adenoma from a patient with familial adenomatous polyposis

BRAF gene mutations in the colorectum have been associated with serrated adenomas and less frequently with hyperplastic polyps, villous adenomas, tubular adenomas, and carcinomas. Most BRAF mutations in the colon have been reported as a V600E substitution. We report a case with a very rare deletion mutation of BRAF (c.1799-1801delTGA, p.Val600_Lys601delinsGlu) in a serrated adenoma; the patient has familial adenomatous polyposis with a germline mutation of the APC gene (c.3578delA, p.Gln1193ArgfsX1264). Genetic studies on fundic gland polyps and tubular adenomas from the same patient failed to demonstrate BRAF mutation. This case is the first reported with a deletion mutation of BRAF found in the colon.

Germline mutations in APC and MUTYH are responsible for the majority of families with attenuated familial adenomatous polyposis

A small fraction of families with familial adenomatous polyposis (FAP) display an attenuated form of FAP (AFAP). We aimed to assess the presence of germline mutations in the MUTYH and adenomatous polyposis coli (APC) genes in AFAP families and to compare the clinical features between the two causative genes. Families with clinical AFAP were selected from the Dutch Polyposis Registry according to the following criteria: (a) at least two patients with 10-99 adenomas diagnosed at age >30 years or (b) one patient with 10-99 adenomas at age >30 years and a first-degree relative with colorectal cancer (CRC) with a few adenomas, and, applying for both criteria, no family members with more than 100 polyps before the age of 30 years. All probands were screened for germline mutations in the APC and MUTYH genes. Twenty-five of 315 Dutch families with FAP (8%) met our criteria for AFAP. These families included 146 patients with adenomas and/or CRC. Germline APC mutations were identified in nine families and biallelic MUTYH mutations in another nine families. CRC was identified at a mean age of 54 years (range 24-83 years) in families with APC and at 50 years (range 39-70 years) in families with MUTYH (p = 0.29). APC and biallelic MUTYH mutations are responsible for the majority of AFAP families. Based on our results and those reported in the literature, we recommend colonoscopy once every 2 years in AFAP families, starting surveillance from the late teens in APC mutation carriers and from age 20-25 years in biallelic MUTYH mutation carriers.

The AAPC case, with an early onset of colorectal cancer

INTRODUCTION

Attenuated adenomatous polyposis coli (AAPC) is a variant of the familial adenomatous polyposis (FAP) characterized by the occurrence of sparse polyps in the colon, stomach, and duodenum with a late onset of colorectal cancer. The AAPC syndrome is associated with mutations at the 5' region of the APC gene. Until recently, the fragment encompassing codons 157 and 170 was considered as boundary for the described cases of AAPC and FAP syndromes.

MATERIALS AND METHODS

This study describes a case of the AAPC syndrome caused by a CCTT deletion at codon 173, with polyps diagnosed at the age of 17. The father and grandfather of the proband died of colorectal cancer (CRC), which developed from untreated polyps, at the age 35 and 40, respectively.

RESULTS AND DISCUSSIONS

In the case of the proband's father, the untreated polyps led to death after 12 years. The proband revealed a low number of polyps and an extra colon feature characteristic of AAPC, but the polyps onset and the death of CRC of two family members, who refused colectomy, was very early and characteristic for FAP. An atypical course of AAPC must be taken into consideration both in genetic counseling and in qualifying the patients with AAPC for the surgical treatment.

Balance between endoscopic and genetic information in the choice of ileorectal anastomosis for familial adenomatous polyposis

BACKGROUND AND OBJECTIVES

The number of rectal polyps and the site of mutations in the APC (Adenomatous polyposis coli) gene have been used to guide the surgical management in patients with familial adenomatous polyposis (FAP). The aim of this study is to assess the utility of the APC mutation screening compared to the degree of the rectal polyposis in surgical decision making.

METHODS

The post-surgical courses of 25 patients submitted to subtotal colectomy with ileorectal anastomosis (IRA) were reviewed. Preservation of the rectum was prospectively decided on the basis of well-defined endoscopic criteria. The number of rectal polyps was assessed preoperatively and every 6-12 months. APC gene was screened for mutations by heteroduplex analysis, single strand conformation polymorphism, in vitro synthesized protein (IVSP), and DNA sequencing. Patients negative for APC mutations were tested for MYH mutations.

RESULTS

On the basis of preoperative polyp rectal count we categorized patients as follows: Group I, 5 or fewer adenomas; Group II, 6-9 adenomas; Group III, 10 or more adenomas. After a follow-up ranging from 12 to 225 months we have observed a significant difference of recurrent rectal adenomas between Groups I-II versus III. No difference was detected among patients of Group I and II. The mean number of adenomas/year/patient was 0.67, 1.62, and 9.29 for Group I, II, and III, respectively. Carpeting polyposis of the rectal stump developed in three patients with APC mutation at codon 1309 and two of them needed later proctectomy. Diffuse rectal polyposis was observed in one patient with mutation at exon 9 who had 10 small polyps at time of surgery. Mutation at the 5'-end of APC (codons 144-232), mutation of MYH and unknown APC or MYH mutation were correlated with a low number of polyps both at presentation and follow-up. No IRA patients developed rectal cancer.

CONCLUSIONS

In our experience fewer than 10 rectal polyps at presentation can predict a favorable outcome after IRA. Identification of specific germ-line APC or MYH mutation can address the choice of surgical treatment.

Impact of Phospholipase A2 group IIa gene polymorphism on phenotypic features of patients with familial adenomatous polyposis

PURPOSE

Phospholipase A2 Group IIa has been suggested to be a possible disease modifier gene in familial adenomatous polyposis. This investigation was designed to elucidate possible association between phospholipase A2 Group IIa polymorphism and phenotypes of patients with familial adenomatous polyposis.

METHODS

Phospholipase A2 Group IIa was examined by polymerase chain reaction-based single strand conformation polymorphism and direct sequencing in 55 patients from 45 families with familial adenomatous polyposis. The patients were examined by gastroduodenoscopy plus biopsy with respect to fundic gland polyposis and gastroduodenal adenomas. Helicobacter pylori status was determined by rapid urease test. Contributions of genetic alteration and Helicobacter pylori infection to intestinal and extraintestinal lesions were investigated.

RESULTS

Four types of single nucleotide polymorphism were found in exon 3 of phospholipase A2 Group IIa, among which single nucleotide polymorphism in codon 32 was the most frequent. The prevalence of fundic gland polyposis was higher in patients positive for single nucleotide polymorphism of phospholipase A2 Group IIa than those negative for single nucleotide polymorphism (61 vs. 33 percent; P < 0.05). In contrast, positive rate of Helicobacter pylori infection was lower in the former than in the latter (22 vs. 52 percent; P < 0.05). The prevalence of the other phenotypes was not different significantly. Logistic regression analysis revealed a possibility toward single nucleotide polymorphism of phospholipase A2 Group IIa as an independent risk factor for fundic gland polyposis (95 percent confidence interval, 00.9-14.3; P = 0.06).

CONCLUSIONS

Phospholipase A2 Group IIa may be a modifier gene for fundic gland polyposis in patients with familial adenomatous polyposis.

Deconstructing schizophrenia: an overview of the use of endophenotypes in order to understand a complex disorder

The genetics of schizophrenia has been approached utilizing a variety of methods. One emerging strategy is the use of endophenotypes in order to understand and identify the functional importance of genetically transmitted, brain-based deficits across schizophrenia kindreds. The endophenotype strategy is a topic of this issue of Schizophrenia Bulletin. Endophenotypes are quantitative, heritable, trait-related deficits typically assessed by laboratory-based methods rather than clinical observation. Endophenotypes are seen as closer to genetic variation than are clinical symptoms of schizophrenia, and are therefore closely linked to heritable risk factors. There has been a broad expansion of opportunities available to psychiatric neuroscientists who use the endophenotype strategy to understand the genetic basis of schizophrenia. In this context, genetic variation such as single nucleotide polymorphisms (SNPs) induces abnormalities in endophenotypic domains such as neurocognition, neurodevelopment, metabolism, and neurophysiology. This article discusses the challenges that abound in genetic research of schizophrenia, including issues in ascertainment, epistasis, ethnic diversity, and the potentially normalizing effects of second-generation antipsychotic medications on neurocognitive and neurophysiological measures. Robust strategies for meeting these challenges are discussed in this review and the subsequent articles in this issue. This article summarizes conceptual advances and progress in the measurement and use of endophenotypes in schizophrenia that form the basis of the multisite National Institute of Mental Health Consortium on the Genetics of Schizophrenia. The endophenotype strategy offers powerful and exciting opportunities to understand the genetically conferred neurobiological vulnerabilities and possible new strong inference and molecularly based treatments for schizophrenia.

Subtyping schizophrenia: implications for genetic research

Phenotypic variability and likely extensive genetic heterogeneity have been confounding the search for the causes of schizophrenia since the inception of the diagnostic category. The inconsistent results of genetic linkage and association studies using the diagnostic category as the sole schizophrenia phenotype suggest that the current broad concept of schizophrenia does not demarcate a homogeneous disease entity. Approaches involving subtyping and stratification by covariates to reduce heterogeneity have been successful in the genetic study of other complex disorders, but rarely applied in schizophrenia research. This article reviews past and present attempts at delineating schizophrenia subtypes based on clinical features, statistically derived measures, putative genetic indicators, and intermediate phenotypes, highlighting the potential utility of multidomain neurocognitive endophenotypes.

Familial adenomatous polyposis (FAP): genotype correlation to FAP phenotype with osteomas and sebaceous cysts

Gardner syndrome is characterized by the triad of colorectal adenomas, soft and hard tissue tumors. This disorder was regarded as a separate disease until the identification of the APC gene when it was recognized that mutations in the APC gene were the underlying cause of both Gardner syndrome and familial adenomatous polyposis (FAP). The present study aimed at examining whether a particular APC genotype could be delineated in FAP patients with benign extracolonic manifestations: sebaceous cysts and/or osteomas. A questionnaire was sent to all Danish FAP patients (N = 234) asking for occurrence of sebaceous cysts and palpable osteomas. Medical records later verified positive findings, when possible. The results for each patient were correlated to the position of his or her mutation in the APC gene. Positive participation compliance was 77% (N = 180), and in 105 of these patients the pathogenic APC mutation was known. Palpable osteomas were reported in 17 of the patients in whom a pathogenic mutation had been identified. Osteomas were only identified in patients with mutations between codon 767 and 1513, a gene area also associated with congenital hypertrophy of the retinal-pigmented epithelium (CHRPE) and hepatoblastoma. Sebaceous cysts were reported in 51% of the patients, and their APC mutations were evenly distributed in the gene with no particular hotspot. Osteomas appeared most frequently in patients with sebaceous cysts, odds ratio 6.6, P < 0.001. The study provides molecular evidence that Gardner syndrome is a variant of FAP and essentially obsolete in clinical practice.

Evolution of the nomenclature for the hereditary colorectal cancer syndromes

The hereditary forms of colorectal cancer have been given many names historically as the manifestations have been gradually understood. Lynch syndrome has had several names, most prominently 'Hereditary Nonpolyposis Colorectal Cancer' or HNPCC. Clarification of the genetic basis and full phenotypic expression of this disease mandates a more clinically useful name that clarifies the consideration of non-colonic cancers in a family history, and unifies the diagnosis around the germline mutation in a DNA mismatch repair (MMR) gene. The term 'Lynch syndrome' is proposed for the autosomal dominant disease caused by a germline mutation in a DNA MMR gene.

The use of neurophysiological endophenotypes to understand the genetic basis of schizophrenia

Specifying the complex genetic architecture of the “fuzzy” clinical phenotype of schizophrenia is an imposing problem. Utilizing metabolic, neurocognitive, and neurophysiological “intermediate” endophenotypic measures offers significant advantages from a statistical genetics stand-point. Endophenotypic measures are amenable to quantitative genetic analyses, conferring upon them a major methodological advantage compared with largely qualitative diagnoses using the Diagnostic and Statistical Manual of Mental Health, 4th Edition (DSM-IV). Endophenotypic deficits occur across the schizophrenia spectrum in schizophrenia patients, schizotypal patients, and clinically unaffected relatives of schizophrenia patients, Neurophysiological measures, such as P50 event-related suppression and the prepulse inhibition (PPI) of the startle response, are endophenotypes that can be conceptualized as being impaired because of a single genetic abnormality in the functional cascade of DNA to RNA to protein. The “endophenotype approach” is also being used to understand other medical disorders, such as colon cancer, hemochromatosis, and hypertension, where there is interplay between genetically conferred vulnerability and nongenetic stressors. The power and utility of utilizing endophenotypes to understand the genetics of schizophrenia is discussed in detail in this article.

The emergence of a new paradigm of pharmacogenomics

A series of qualitatively new properties of the complex polygenic systems are transforming the dominant, genome-centric approach of pharmacogenomics towards a more integrative, holistic paradigm. The recent concepts of interposition of regulatory networks between genotype and phenotype, and the emergence of epigenotype as the locus of integration of genetic background with nutritional and lifestyle influences, render problematic any prediction of the consequences of individual gene alterations. In addition, the redefinition of the traditional boundaries of clinical phenotypes, with the promotion of the endophenotypes as methodological strategy, and the initiative of the phenome elucidation, reshape both the research, as well as the application, of pharmacogenomics. These concepts and developments can explain some of the complexity, and the multifactorial nature, of most drug responses and imply another understanding of education in the field, which aims at stimulating a critical reflection on these major shifts prior to a practical training on the immediate application of pharmacogenomics.

Genetic testing for germline mutations of the APC gene in patients with apparently sporadic desmoid tumors but a family history of colorectal carcinoma

PURPOSE

Desmoid tumors, also known as aggressive fibromatosis, occur with an incidence of 10 to 15 percent in patients affected by familial adenomatous polyposis, an autosomal inherited disease caused by germline mutations in the APC gene. However, sporadic forms with no hereditary background exist. The aim of this study was to find out whether there are APC germline mutations in apparently sporadic desmoid tumor patients without clinical or familial signs of familial adenomatous polyposis but with a family history of colorectal carcinoma in at least one family member.

METHODS

Genomic DNA and mRNA were isolated from peripheral blood leukocytes of index patients of eight nonrelated families. Mutation screening was performed using reverse transcriptase polymerase chain reaction-based protein truncation test for APC exons 1-14. The large APC exon 15 was scrutinized by the protein truncation test of four overlapping genomic fragments. Additionally, genomic DNA from five desmoid tumors was analyzed for loss of heterozygosity at D5S346 close to the APC locus.

RESULTS

No translational stop mutations typical for familial adenomatous polyposis could be found in the APC gene in any of the analyzed blood samples from the desmoid tumor patients. Additionally, no loss of heterozygosity at D5S346 was found in four of five desmoids; one tumor was not informative.

CONCLUSIONS

These results may suggest that patients with sporadic desmoids and no clinical signs of familial adenomatous polyposis detected on careful examination, esophagogastroduodenoscopy, and complete colonoscopy do not need to be tested routinely for germline mutations of the APC gene. However, as large studies dealing with this problem are absent, it might be more time and cost effective to perform an APC mutational analysis instead.

From Colonic Polyps to Colon Cancer: Pathophysiology, Clinical Presentation, and Diagnosis

Epidemiologists, basic researchers, clinicians, and public health administrators unite! Develop and implement a simple, safe, and effective preventive and screening test for colon cancer. The public will willingly and enthusiastically accept such a test. Many thousands of lives are at stake every year.

Intraductal papillary mucinous neoplasm of the pancreas in a patient with attenuated familial adenomatous polyposis

A 67 year old man with a clinical diagnosis of attenuated familial adenomatous polyposis (AFAP) and a past history of synchronous colon cancers in the transverse colon was also found to have an intraductal papillary mucinous neoplasm (IPMN) of the pancreas. In addition, several foci of heterotopic gastric oxyntic mucosa were noted in the duodenum, interspersed with flat and polypoid adenomas. The duodenal adenomas showed low grade dysplasia, loss of adenomatous polyposis coli (APC) protein expression, but retention of beta catenin staining, localised to the nucleus and cytoplasm. The IPMN in the pancreas showed an identical immunohistochemical profile to the duodenal adenomas. The heterotopic gastric foci in the duodenum were negative for the APC protein, and beta catenin staining was membranous in location. Although the patient did not show germline truncating APC mutations or mutations in the MYH gene, the past history, clinical features, and immunohistochemical profile of the various lesions suggest strongly that the IPMN is part of the spectrum of lesions encountered in AFAP. Whether the heterotopic oxyntic gastric mucosa in the duodenum is also related is unclear, but it may represent a forme fruste of fundic gland polyps.

Signaling pathways in intestinal development and cancer

The study of the epithelium of the adult mammalian intestine touches upon many modern aspects of biology. The epithelium is in a constant dialogue with the underlying mesenchyme to control stem cell activity, proliferation in transit-amplifying compartments, lineage commitment, terminal differentiation and, ultimately, cell death. There are spatially distinct compartments dedicated to each of these events. The Wnt, TGF-beta, BMP, Notch, and Par polarity pathways are the major players in homeostatic control of the adult epithelium. Several hereditary cancer syndromes deregulate these same signaling cascades through mutational (in)activation. Moreover, these mutations often also occur in sporadic tumors. Thus symmetry exists between the roles that these signaling pathways play in physiology and in cancer of the intestine. This is particularly evident for the Wnt/APC pathway, for which the mammalian intestine has become one of the most-studied paradigms. Here, we integrate recent knowledge of the molecular inner workings of the prototype signaling cascades with their specific roles in intestinal epithelial homeostasis and in neoplastic transformation of the epithelium.