The APCI1307K allele and cancer risk in a community-based study of Ashkenazi Jews

Low-Penetrance Susceptibility Variants in Colorectal Cancer-Current Outlook in the Field

Colorectal cancer (CRC) is one of the most frequent and mortality-causing neoplasia, with various distributions between populations. Strong hereditary predispositions are the causatives of a small percentage of CRC, and most cases have no transparent genetic background. This is a vast arena for exploring cancer low-susceptibility genetic variants. Nonetheless, the research that has been conducted to date has failed to deliver consistent conclusions and often features conflicting messages, causing chaos in this field. Therefore, we decided to organize the existing knowledge on this topic. We screened the PubMed and Google Scholar databases. We drew up markers by gene locus gathered by hallmark: oncogenes, tumor suppressor genes, genes involved in DNA damage repair, genes involved in metabolic pathways, genes involved in methylation, genes that modify the colonic microenvironment, and genes involved in the immune response. Low-penetration genetic variants increasing the risk of cancer are often population-specific, hence the urgent need for large-scale testing. Such endeavors can be successful only when financial decision-makers are united with social educators, medical specialists, genetic consultants, and the scientific community. Countries' policies should prioritize research on this subject regardless of cost because it is the best investment. In this review, we listed potential low-penetrance CRC susceptibility alleles whose role remains to be established.

A truncation mutant of adenomatous polyposis coli impairs apical cell extrusion through elevated epithelial tissue tension

Tissue tension encompasses the mechanical forces exerted on solid tissues within animal bodies, originating from various sources such as cellular contractility, interactions with neighboring cells and the extracellular matrix. Emerging evidence indicates that an imbalance in such forces can influence structural organization, homeostasis, and potentially contribute to disease. For instance, heightened tissue tension can impede apical cell extrusion, leading to the retention of apoptotic or transformed cells. In this study, we investigate the potential role of adenomatous polyposis coli (APC) in modulating tissue tension. Our findings reveal that expression of an APC truncation mutant elevates epithelial tension via the RhoA/ROCK pathway. This elevation induces morphological alterations and hampers apoptotic cell extrusion in cultured epithelial cells and organoids, both of which could be mitigated by pharmacologically restoring the tissue tension. This raises the possibility that APC mutations may exert pathogenetic effects by altering tissue mechanics.

Case Series of Men with the Germline APC I1307K variant and Treatment-Emergent Neuroendocrine Prostate Cancer

INTRODUCTION

Somatic mutations in the Wnt signaling gene Adenomatous Polyposis Coli (APC) promote metastatic prostate cancer (PCa) progression. Less is known regarding the impact of germline APC mutations on PCa outcomes. We sought to investigate the prevalence of aggressive variant PCa (AVPC) and treatment-emergent neuroendocrine PCa (t-NEPC) in patients with the germline APC I1307K variant, an alteration found in 7% of Ashkenazi Jewish men.

MATERIALS AND METHODS

We report a retrospective cohort study comparing patients with PCa and either APC I1307K germline mutation, APC somatic mutations, or unselected patients. Proportions of patients with AVPC among all the cases were estimated along with 95% Clopper-Pearson exact confidence intervals (CI). Odds ratios with 95% CI were provided for the prevalence of t-NEPC and AVPC in patients with germline APC I1307K compared to patients with frameshift alterations in APC.

RESULTS

From 2016-2022, 18 patients with PCa at 3 institutions with the germline APC (I1307K) mutation were identified. Clinically-defined AVPC was found in 8 of the 15 cases with metastatic disease (53%; 95% CI: 26%-79%). Combined somatic alterations in two or more of RB1, TP53 or PTEN (molecularly-defined AVPC) were found in 5/18 cases (28%; 95% CI: 10%-54%). When compared to 20 patients with APC somatic frameshift mutations, patients with the germline APC I1307K variant had a significantly increased risk of AVPC (OR 7.2; 95% CI 1.27, 40.68).

CONCLUSION

PCa that develops in the presence of the germline APC I1307K mutation appear to be enriched for clinically-defined and molecularly-defined AVPC and in particular, for t-NEPC.

Position statement of the International Society for Gastrointestinal Hereditary Tumours (InSiGHT) on APC I1307K and cancer risk

While constitutional pathogenic variants in the APC gene cause familial adenomatous polyposis, APC c.3920T>A; p.Ile1307Lys (I1307K) has been associated with a moderate increased risk of colorectal cancer (CRC), particularly in individuals of Ashkenazi Jewish descent. However, published data include relatively small sample sizes, generating inconclusive results regarding cancer risk, particularly in non-Ashkenazi populations. This has led to different country/continental-specific guidelines regarding genetic testing, clinical management and surveillance recommendations for I1307K. A multidisciplinary international expert group endorsed by the International Society for Gastrointestinal Hereditary Tumours (InSiGHT), has generated a position statement on the APC I1307K allele and its association with cancer predisposition. Based on a systematic review and meta-analysis of the evidence published, the aim of this document is to summarise the prevalence of the APC I1307K allele and analysed the evidence of the associated cancer risk in different populations. Here we provide recommendations on the laboratory classification of the variant, define the role of predictive testing for I1307K, suggest recommendations for cancer screening in I1307K heterozygous and homozygous individuals and identify knowledge gaps to be addressed in future research studies. Briefly, I1307K, classified as pathogenic, low penetrance, is a risk factor for CRC in individuals of Ashkenazi Jewish origin and should be tested in this population, offering carriers specific clinical surveillance. There is not enough evidence to support an increased risk of cancer in other populations/subpopulations. Therefore, until/unless future evidence indicates otherwise, individuals of non-Ashkenazi Jewish descent harbouring I1307K should be enrolled in national CRC screening programmes for average-risk individuals.

Comprehensive Genetic Analysis of Druze Provides Insights into Carrier Screening

BACKGROUND

Druze individuals, like many genetically homogeneous and isolated populations, harbor recurring pathogenic variants (PV) in autosomal recessive (AR) disorders.

METHODS

Variant calling of whole-genome sequencing (WGS) of 40 Druze from the Human Genome Diversity Project (HGDP) was performed (HGDP-cohort). Additionally, we performed whole exome sequencing (WES) of 118 Druze individuals: 38 trios and 2 couples, representing geographically distinct clans (WES-cohort). Rates of validated PV were compared with rates in worldwide and Middle Eastern populations, from the gnomAD and dbSNP datasets.

RESULTS

Overall, 34 PVs were identified: 30 PVs in genes underlying AR disorders, 3 additional PVs were associated with autosomal dominant (AD) disorders, and 1 PV with X-linked-dominant inherited disorder in the WES cohort.

CONCLUSIONS

The newly identified PVs associated with AR conditions should be considered for incorporation into prenatal-screening options offered to Druze individuals after an extension and validation of the results in a larger study.

The role of next-generation sequencing in the examination of signaling genes in Brca1/2-negative breast cancer cases

INTRODUCTION

Breast cancer is the most prevalent malignancy in women worldwide. Although pathogenic variants in the BRCA1/2 genes are responsible for the majority of hereditary breast cancer cases, a substantial proportion of patients are negative for pathogenic variations in these genes. In cancers, the signal transduction pathways of the cell are usually affected first. Therefore, this study aimed to detect and classified genetic variations in non-BRCA signaling genes and investigate the underlying genetic causes of susceptibility to breast cancer.

METHODS

Ninety-six patients without pathogenic variants in the BRCA1/2 genes who met the inclusion criteria were enrolled in the study, and 34 genes were analyzed using next-generation sequencing (NGS) for genetic analysis.

RESULTS

Based on the ClinVar database or American College of Medical Genetics criteria, a total of 55 variants of 16 genes were detected in 43 (44.8%) of the 96 patients included in the study. The pathogenic variants were found in the TP53, CHEK2, and RET genes, whereas the likely pathogenic variants were found in the FGFR1, FGFR3, EGFR, and NOTCH1 genes.

CONCLUSION

The examination of signaling genes in patients who met the established criteria for hereditary breast cancer but were negative for BRCA1/2 pathogenic variants provided additional information for approximately 8% of the families. The results of the present study suggest that NGS is a powerful tool for investigating the underlying genetic causes of occurrence and progression of breast cancer.

Ashkenazi Jewish and Other White APC I1307K Carriers Are at Higher Risk for Multiple Cancers

Purpose: APC I1307K has a higher prevalence among Ashkenazi Jews (AJ), and a two-fold increased risk for colorectal cancer (CRC) compared to non-Jewish populations. We assessed CRC and extracolonic malignancies among I1307K carriers from AJ and non-AJ whites (NAW). Methods: We compared the rate of I1307K in cancer patients who underwent germline genetic testing via a multi-gene panel with healthy subjects retrieved from the gnomAD database. Cases undergoing testing were not selected and testing was undertaken through a commercial laboratory. Results: Overall, 586/7624 (7.6%) AJ with cancer carried I1307K compared to 342/4918 (6.9%) in the AJ control group (p = NS). In the NAW, 318/141,673 (0.2%) cancer patients and 73/58,918 (0.1%) controls carried the variant [OR = 1.8, (95% CI 1.41−2.35), p < 0.001]. I1307K in NAW was associated with an increased risk of CRC [OR = 1.95, (95% CI 1.39−2.73), p < 0.01], melanoma [OR = 2.54, (95% CI 1.57−3.98)], breast [females, OR = 1.73, (95% CI 1.18−2.65), p < 0.01], and prostate cancer [males, OR = 2.42, (95% CI 1.45−3.94), p < 0.01]. Among AJ, the variant increased the risk for CRC [OR = 1.67, (95% CI 1.36−2.05), p < 0.001] and renal cancer [OR = 1.64, (95% CI 1.04−2.47)]. AJ men had a higher risk for any cancer [OR = 1.32, (95% CI 1.05−1.66), p < 0.05] and melanoma [OR = 2.04, (95% CI 1.24−3.22); p < 0.05]. Conclusions: This is the most extensive study to date conducted on I1307K carriers, although it is amenable to selection bias. NAW carrying I1307K had a higher risk of any cancer and several specific cancer types, whereas AJ carrying the variant had a risk for only a few select cancers. Our data add to the research base on I1307 carriers concerning future risk management.

Polygenic early-onset colorectal cancer in pediatric patients

Colorectal cancer in the pediatric population is a rare but transpirable phenomenon. The occurrence should prompt suspicion for underlying genetic mutations in the setting of a hereditary cancer predisposition syndrome. In this series, we outline three pediatric patients with colonic adenocarcinoma who were found to have one or more germline mutations. The presence of compound mutations may lead to a hypermutator phenotype resulting in earlier presentation of colorectal cancer in childhood and adolescence. The diagnosis of colorectal cancer in pediatric patients warrants timely recognition, multigene panel testing, genetic counseling for the patient and family, and increased surveillance for intestinal and extra-intestinal tumors.

Actionable genomic variants in 6045 participants from the Qatar Genome Program

In a clinical setting, DNA sequencing can uncover findings unrelated to the purpose of genetic evaluation. The American College of Medical Genetics and Genomics (ACMG) recommends the evaluation and reporting of 59 genes from clinic genomic sequencing. While the prevalence of secondary findings is available from large population studies, these data lack Arab and other Middle Eastern populations. The Qatar Genome Program (QGP) generates whole-genome sequencing (WGS) data and combines it with phenotypic information to create a comprehensive database for studying the Qatari and wider Arab and Middle Eastern populations at the molecular level. This study identified and analyzed medically actionable variants in the 59 ACMG genes using WGS data from 6045 QGP participants. Our results identified a total of 60 pathogenic and likely pathogenic variants in 25 ACMG genes in 141 unique individuals. Overall, 2.3% of the QGP sequenced participants carried a pathogenic or likely pathogenic variant in one of the 59 ACMG genes. We evaluated the QGP phenotype-genotype association of additional nonpathogenic ACMG variants. These variants were found in patients from the Hamad Medical Corporation or reported incidental findings data in Qatar. We found a significant phenotype association for two variants, c.313+3A>C in LDLR, and c.58C>T (p.Gln20*) in the TPM1.

Analysis of Sequence and Copy Number Variants in Canadian Patient Cohort With Familial Cancer Syndromes Using a Unique Next Generation Sequencing Based Approach

Background

Hereditary cancer predisposition syndromes account for approximately 10% of cancer cases. Next generation sequencing (NGS) based multi-gene targeted panels is now a frontline approach to identify pathogenic mutations in cancer predisposition genes in high-risk families. Recent evolvement of NGS technologies have allowed simultaneous detection of sequence and copy number variants (CNVs) using a single platform. In this study, we have analyzed frequency and nature of sequence variants and CNVs, in a Canadian cohort of patients, suspected with hereditary cancer syndrome, referred for genetic testing following specific genetic testing guidelines based on patient's personal and/or family history of cancer.

Methods

A 2870 patients were subjected to a single NGS based multi-gene targeted hereditary cancer panel testing algorithm to identify sequence variants and CNVs in cancer predisposition genes at our reference laboratory in Southwestern Ontario. CNVs identified by NGS were confirmed by alternative techniques like Multiplex ligation-dependent probe amplification (MLPA).

Results

A 15% (431/2870) patients had a pathogenic variant and 36% (1032/2870) had a variant of unknown significance (VUS), in a cancer susceptibility gene. A total of 287 unique pathogenic variant were identified, out of which 23 (8%) were novel. CNVs identified by NGS based approach accounted for 9.5% (27/287) of pathogenic variants, confirmed by alternate techniques with high accuracy.

Conclusion

This study emphasizes the utility of NGS based targeted testing approach to identify both sequence and CNVs in patients suspected with hereditary cancer syndromes in clinical setting and expands the mutational spectrum of high and moderate penetrance cancer predisposition genes.

BRCA in Gastrointestinal Cancers: Current Treatments and Future Perspectives

A strong association between pancreatic cancer and BRCA1 and BRCA2 mutations is documented. Based on promising results of breast and ovarian cancers, several clinical trials with poly (ADP-ribose) polymerase inhibitors (PARPi) are ongoing for gastrointestinal (GI) malignancies, especially for pancreatic cancer. Indeed, the POLO trial results provide promising and awaited changes for the pancreatic cancer therapeutic landscape. Contrariwise, for other gastrointestinal tumors, the rationale is currently only alleged. The role of BRCA mutation in gastrointestinal cancers is the subject of this review. In particular, we aim to provide the latest updates about novel therapeutic strategies that, exploiting DNA repair defects, promise to shape the future therapeutic scenario of GI cancers.

Co-occurrence of breast cancer and neuroendocrine tumours: New genetic insights beyond Multiple Endocrine Neoplasia syndromes

OBJECTIVE

Age-standardized incidence of female breast cancer is 145.1 per 100000/year and 5.86 per 100000/year for neuroendocrine tumours (NET) in Canada. Evidence is scarce about gene variants that may predispose patients to develop both neoplasms. The objective of this study was to identify germline gene variants associated with this combination of tumours.

DESIGN AND PATIENTS

A retrospective chart review (2007-2018) in a tertiary NET referral centre was completed. A series of 9 female patients with concurrent breast cancer and NET is presented. All patients underwent a 37 gene hereditary cancer next-generation sequencing panel.

RESULTS

Mean age was 61.4 years (35-85) at breast cancer diagnosis and 63.4 years (51-89) at NET diagnosis. Four patients had a pancreatic, three had a small bowel and two had a lung NET. Two patients were known cases of MEN1, and one patient was found to harbour a pathogenic variant in MEN1 and a variant of unknown significance (VUS) in ATM. A second patient was found to harbour a pathogenic variant in APC. A third patient was found to carry a pathogenic variant in PALB2 as well as a VUS in FANCM, MLH1 and STK11. Another patient was found to harbour a VUS in MSH2. One patient was found to carry a pathogenic variant in NTHL1.

CONCLUSION

The first cases of a PALB2, an APC and a NTHL1 pathogenic variants in patients with both breast cancer and NET were presented. NGS testing should be considered in specific patients with this combination of neoplasms, as certain germline variants beyond MEN1, have important implications for cancer surveillance.

High-frequency actionable pathogenic exome variants in an average-risk cohort

Exome sequencing is increasingly utilized in both clinical and nonclinical settings, but little is known about its utility in healthy individuals. Most previous studies on this topic have examined a small subset of genes known to be implicated in human disease and/or have used automated pipelines to assess pathogenicity of known variants. To determine the frequency of both medically actionable and nonactionable but medically relevant exome findings in the general population we assessed the exomes of 70 participants who have been extensively characterized over the past several years as part of a longitudinal integrated multiomics profiling study. We analyzed exomes by identifying rare likely pathogenic and pathogenic variants in genes associated with Mendelian disease in the Online Mendelian Inheritance in Man (OMIM) database. We then used American College of Medical Genetics (ACMG) guidelines for the classification of rare sequence variants. Additionally, we assessed pharmacogenetic variants. Twelve out of 70 (17%) participants had medically actionable findings in Mendelian disease genes. Five had phenotypes or family histories associated with their genetic variants. The frequency of actionable variants is higher than that reported in most previous studies and suggests added benefit from utilizing expanded gene lists and manual curation to assess actionable findings. A total of 63 participants (90%) had additional nonactionable findings, including 60 who were found to be carriers for recessive diseases and 21 who have increased Alzheimer's disease risk because of heterozygous or homozygous APOE e4 alleles (18 participants had both). Our results suggest that exome sequencing may have considerably more utility for health management in the general population than previously thought.

Outcomes of retesting BRCA negative patients using multigene panels

The utility of multigene panels in retesting patients who previously tested negative for a pathogenic mutation by BRCA1/2 testing is not well established. Patients who previously tested negative for a pathogenic BRCA1/2 mutation by standard sequencing, and who were seen in cancer genetics center between November 1, 2012 and June 30, 2015 for additional testing utilizing multigene panels, were identified using our genetic testing registry. Data on demographics, personal and family history of cancer, results of panel testing and the impact on patient management was collected retrospectively. A total of 122 patients underwent retesting during the study period. Thirteen (11%) pathogenic mutations were identified in the following genes: CHEK2(4), PALB2(3), ATM(2), CDH1, APC, BARD1 and MRE11A. Eleven out of these thirteen mutations were deemed actionable based on published guidelines. Of these eleven, seven patients had an actual change in clinical management as a result of retesting. Furthermore, retesting also led to a change in clinical management in the two patients with mutations in genes (BARD1 and MRE11A) which do not have clear guidelines for management. There were no significant differences in demographics and personal and family history of cancer between patients who tested positive and those who tested negative on retesting. This study demonstrates the clinical utility of multigene panels in a group of high risk individuals who previously tested negative for a BRCA1/2 mutation. This retesting approach revealed a pathogenic mutation in 11% of cases. Retesting led to significant change in clinical management in a majority of patients with actionable mutations (7 out of 11), as well as in those with mutations in genes which do not have specific management guidelines.

Genome-wide association studies of cancer: current insights and future perspectives

Genome-wide association studies (GWAS) provide an agnostic approach for investigating the genetic basis of complex diseases. In oncology, GWAS of nearly all common malignancies have been performed, and over 450 genetic variants associated with increased risks have been identified. As well as revealing novel pathways important in carcinogenesis, these studies have shown that common genetic variation contributes substantially to the heritable risk of many common cancers. The clinical application of GWAS is starting to provide opportunities for drug discovery and repositioning as well as for cancer prevention. However, deciphering the functional and biological basis of associations is challenging and is in part a barrier to fully unlocking the potential of GWAS.

Differential analysis of mutations in the Jewish population and their implications for diseases

Sequencing large cohorts of ethnically homogeneous individuals yields genetic insights with implications for the entire population rather than a single individual. In order to evaluate the genetic basis of certain diseases encountered at high frequency in the Ashkenazi Jewish population (AJP), as well as to improve variant annotation among the AJP, we examined the entire exome, focusing on specific genes with known clinical implications in 128 Ashkenazi Jews and compared these data to other non-Jewish populations (European, African, South Asian and East Asian). We targeted American College of Medical Genetics incidental finding recommended genes and the Catalogue of Somatic Mutations in Cancer (COSMIC) germline cancer-related genes. We identified previously known disease-causing variants and discovered potentially deleterious variants in known disease-causing genes that are population specific or substantially more prevalent in the AJP, such as in the ATP and HGFAC genes associated with colorectal cancer and pancreatic cancer, respectively. Additionally, we tested the advantage of utilizing the database of the AJP when assigning pathogenicity to rare variants of independent whole-exome sequencing data of 49 Ashkenazi Jew early-onset breast cancer (BC) patients. Importantly, population-based filtering using our AJP database enabled a reduction in the number of potential causal variants in the BC cohort by 36%. Taken together, population-specific sequencing of the AJP offers valuable, clinically applicable information and improves AJP filter annotation.

A Frameshift in CSF2RB Predominant Among Ashkenazi Jews Increases Risk for Crohn's Disease and Reduces Monocyte Signaling via GM-CSF

BACKGROUND & AIMS

Crohn's disease (CD) has the highest prevalence in Ashkenazi Jewish populations. We sought to identify rare, CD-associated frameshift variants of high functional and statistical effects.

METHODS

We performed exome sequencing and array-based genotype analyses of 1477 Ashkenazi Jewish individuals with CD and 2614 Ashkenazi Jewish individuals without CD (controls). To validate our findings, we performed genotype analyses of an additional 1515 CD cases and 7052 controls for frameshift mutations in the colony-stimulating factor 2-receptor β common subunit gene (CSF2RB). Intestinal tissues and blood samples were collected from patients with CD; lamina propria leukocytes were isolated and expression of CSF2RB and granulocyte-macrophage colony-stimulating factor-responsive cells were defined by adenomatous polyposis coli (APC) time-of-flight mass cytometry (CyTOF analysis). Variants of CSF2RB were transfected into HEK293 cells and the expression and functions of gene products were compared.

RESULTS

In the discovery cohort, we associated CD with a frameshift mutation in CSF2RB (P = 8.52 × 10(-4)); the finding was validated in the replication cohort (combined P = 3.42 × 10(-6)). Incubation of intestinal lamina propria leukocytes with granulocyte-macrophage colony-stimulating factor resulted in high levels of phosphorylation of signal transducer and activator of transcription (STAT5) and lesser increases in phosphorylation of extracellular signal-regulated kinase and AK straining transforming (AKT). Cells co-transfected with full-length and mutant forms of CSF2RB had reduced pSTAT5 after stimulation with granulocyte-macrophage colony-stimulating factor, compared with cells transfected with control CSF2RB, indicating a dominant-negative effect of the mutant gene. Monocytes from patients with CD who were heterozygous for the frameshift mutation (6% of CD cases analyzed) had reduced responses to granulocyte-macrophage colony-stimulating factor and markedly decreased activity of aldehyde dehydrogenase; activity of this enzyme has been associated with immune tolerance.

CONCLUSIONS

In a genetic analysis of Ashkenazi Jewish individuals, we associated CD with a frameshift mutation in CSF2RB. Intestinal monocytes from carriers of this mutation had reduced responses to granulocyte-macrophage colony-stimulating factor, providing an additional mechanism for alterations to the innate immune response in individuals with CD.

Search for new loci and low-frequency variants influencing glioma risk by exome-array analysis

To identify protein-altering variants (PAVs) for glioma, we analysed Illumina HumanExome BeadChip exome-array data on 1882 glioma cases and 8079 controls from three independent European populations. In addition to single-variant tests we incorporated information on the predicted functional consequences of PAVs and analysed sets of genes with a higher likelihood of having a role in glioma on the basis of the profile of somatic mutations documented by large-scale sequencing initiatives. Globally there was a strong relationship between effect size and PAVs predicted to be damaging (P=2.29 × 10(-49)); however, these variants which are most likely to impact on risk, are rare (MAF<5%). Although no single variant showed an association which was statistically significant at the genome-wide threshold a number represented promising associations - BRCA2:c.9976A>T, p.(Lys3326Ter), which has been shown to influence breast and lung cancer risk (odds ratio (OR)=2.3, P=4.00 × 10(-4) for glioblastoma (GBM)) and IDH2:c.782G>A, p.(Arg261His) (OR=3.21, P=7.67 × 10(-3), for non-GBM). Additionally, gene burden tests revealed a statistically significant association for HARS2 and risk of GBM (P=2.20 × 10(-6)). Genome scans of low-frequency PAVs represent a complementary strategy to identify disease-causing variants compared with scans based on tagSNPs. Strategies to lessen the multiple testing burden by restricting analysis to PAVs with higher priors affords an opportunity to maximise study power.

Whole Genome Sequencing Defines the Genetic Heterogeneity of Familial Pancreatic Cancer

Pancreatic cancer is projected to become the second leading cause of cancer-related death in the United States by 2020. A familial aggregation of pancreatic cancer has been established, but the cause of this aggregation in most families is unknown. To determine the genetic basis of susceptibility in these families, we sequenced the germline genomes of 638 patients with familial pancreatic cancer and the tumor exomes of 39 familial pancreatic adenocarcinomas. Our analyses support the role of previously identified familial pancreatic cancer susceptibility genes such as BRCA2, CDKN2A, and ATM, and identify novel candidate genes harboring rare, deleterious germline variants for further characterization. We also show how somatic point mutations that occur during hematopoiesis can affect the interpretation of genome-wide studies of hereditary traits. Our observations have important implications for the etiology of pancreatic cancer and for the identification of susceptibility genes in other common cancer types.

SIGNIFICANCE

The genetic basis of disease susceptibility in the majority of patients with familial pancreatic cancer is unknown. We whole genome sequenced 638 patients with familial pancreatic cancer and demonstrate that the genetic underpinning of inherited pancreatic cancer is highly heterogeneous. This has significant implications for the management of patients with familial pancreatic cancer.

The APC I1307K allele conveys a significant increased risk for cancer

This study is the first attempt to evaluate the association between the APC I1307K variant and overall cancer risk. It is unique in both its large sample size and in the reliability of data in the control group. The findings described in this article have major implications in terms of identifying asymptomatic individuals who are at increased risk to harbor cancer and therefore targeted to be enrolled in specific early detection and prevention programs. The prevalence of the APC I1307K missense mutation among Ashkenazi Jews is ∼ 6%. Carriers are at an increased risk for colorectal neoplasia. In this study, we examined the association of this variant with non-colorectal cancers. Consecutive 13,013 healthy subjects who underwent screening at the Integrated Cancer Prevention Center between 2006 and 2014 were enrolled. This population was supplemented with 1,611 cancer patients from the same institution. Demographics, medical history, and pathological data were recorded. Mortality data were obtained from the Ministry of Health's registry. The prevalence of APC I1307K in cancer patients and healthy subjects was compared. The APC I1307K variant was detected in 189 (11.8%) cancer patients compared to 614 (4.7%) healthy subjects, reflecting an adjusted age and sex odds ratio (OR) of 2.53 (p < 0.0001). History of two or more cancer types was associated with a positive carrier prevalence (OR = 4.38 p < 0.0001). Males had significantly increased carrier prevalence in lung, urologic, pancreatic, and skin cancers. The carrier prevalence among females was significantly higher only in breast and skin cancers. Female carriers developed cancer at a significantly older age compared to non-carriers (average 62.7 years vs. 57.8, respectively, p = 0.027), had better survival rates (HR = 0.58, p = 0.022) and overall increased longevity (average age of death 78.8 vs. 70.4 years, respectively, p = 0.003). In conclusion, the APC I1307K variant is a reliable marker for overall cancer risk (OR 2.53). Further studies are needed to evaluate its use for specific cancer types-particularly in males. Female carriers have better prognosis and increased lifespan.

GREM1 germline mutation screening in Ashkenazi Jewish patients with familial colorectal cancer

BACKGROUND

A 40 kb ancestral germline duplication upstream of the GREM1 gene was reported in Ashkenazi families with hereditary mixed polyposis syndrome (HMPS).

OBJECTIVE

Assess the contribution of the GREM1 mutation to familial colorectal cancer (CRC) in Ashkenazim.

METHODS

Jewish Ashkenazi individuals (n = 472 155 males, 317 females) were genotyped for the GREM1 duplication, 194 with CRC, 131 had other cancer types (endometrial, pancreatic and ovarian) that show a syndromic association with CRC, and 147 were cancer-free with a suggestive family history of CRC.

RESULTS

One mutation carrier was found who fulfills the Amsterdam criteria for Lynch Syndrome (LS). The prevalence of this mutation amongst LS Ashkenazim is 0·7%.

CONCLUSION

If validated in additional studies it seems rational to recommend to look for the GREM1 founder mutation in Ashkenazi individuals with multiple colorectal polyps and/or fulfill the criteria for LS.

Use of panel tests in place of single gene tests in the cancer genetics clinic

Improved technology has made it possible to test for mutations within multiple genes simultaneously. It is not clear when these gene 'panels' should be used in the hereditary cancer setting. These analyses were intended to guide panel testing criteria. Offering hereditary panel testing as a first and final, 'single-tier', option was explored. A 'two-tiered' approach, in which panel testing is offered reflexively following stricter criteria, was then applied to the same data. Within our cohort of 105 patients, the single-tier approach was associated with a higher mutation detection rate (6.7% vs 3.8%) and variant of uncertain significance (VUS) rate (0.94 vs 0.23 average per person) compared to a two-tiered approach. Of the VUSs also identified in other patients by another lab, 53% were classified differently between laboratories. Individuals reporting African American race had more VUSs compared to other ancestry groups (p = 0.001). The test cost for a single-tier test was 21% more than a two-tiered approach. Single-tier panel testing was associated with higher mutation and VUS rates, and there is inconsistent classification of the VUS/low penetrant genes between laboratories.

The APC p.I1307K polymorphism is a significant risk factor for CRC in average risk Ashkenazi Jews

BACKGROUND

The p.I1307K adenomatous polyposis coli (APC) gene variant, prevalent among Ashkenazi Jews, may increase the risk for colorectal neoplasia. We studied the clinical importance of screening for this polymorphism in 3305 Israelis undergoing colonoscopy.

PATIENTS AND METHODS

Clinical data regarding potential risk factors for colorectal cancer (CRC) were collected from individuals undergoing colonoscopic examination at the Tel-Aviv medical center. The APC p.I1307K was detected using real-time PCR (polymerase chain reaction) from DNA extracted from peripheral mononuclear cells.

RESULTS

The overall prevalence of the p.I1307K polymorphism was 8.0% (10.1% among Ashkenazi and 2.7% among Sephardic Jews, p<0.001). The overall adjusted odds ratio (OR) for colorectal neoplasia among carriers was 1.51 (95% confidence intervals (CI), 1.16-1.98). Among average risk Ashkenazi Jews, the adjusted OR was 1.75 (95% CI 1.26-2.45). A multiplicative interaction was identified between Ashkenazi ethnicity and APC p.I1307K carrier status (P(INTERACTION) = 0.055). The histopathological features of adenomas and carcinomas did not differ between carriers and non-carriers.

CONCLUSIONS

The APC p.I1307K gene variant is an important risk factor for colorectal neoplasia in average risk Ashkenazi Jews. Carriers in this group should be considered for screening colonoscopy at the age of 40, to be repeated every 5 years, similar to recommendations in individuals with family history of colorectal cancer.

APC polymorphisms and the risk of colorectal neoplasia: a HuGE review and meta-analysis

Adenomatous polyposis coli gene (APC) polymorphisms may influence the risk for colorectal neoplasia. However, results thus far have been inconclusive. We performed a systematic literature search of the Medline, Embase, Cochrane Collaboration, and HuGE databases and reviewed the references of pertinent articles through May 2012. Odds ratios with 95% confidence intervals were used to estimate the association between 3 APC polymorphisms (D1822V, E1317Q, and I1307K) and colorectal neoplasia. In total, 40 studies from 1997 to 2010 were included in this meta-analysis, and individuals with the D1822V variant homozygote VV genotype had a slight decrease in the risk for colorectal neoplasia compared with the wild-type homozygote DD genotype (pooled odds ratio = 0.87, 95% confidence interval: 0.77, 0.99). There was a small association between the APC E1317Q polymorphism and a risk for colorectal neoplasia (variant vs. wild-type: pooled odds ratio = 1.41, 95% confidence interval: 1.14, 1.76), particularly for colorectal adenomas (variant vs. wild-type: odds ratio = 2.89, 95% confidence interval: 1.83, 4.56). Compared with those who carried the wild-type I1307K, Ashkenazi Jews who carried the I1307K variant were at a significantly increased risk for colorectal neoplasia, with a pooled odds ratio of 2.17 (95% confidence interval: 1.64, 2.86). Our study suggests that APC is a candidate gene for colorectal neoplasia susceptibility.

Diagnostic cancer genome sequencing and the contribution of germline variants

Whole-genome sequencing (WGS) is revolutionizing medical research and has the potential to serve as a powerful and cost-effective diagnostic tool in the management of cancer. We review the progress to date in the use of WGS to reveal how germline variants and mutations may be associated with cancer. We use colorectal cancer as an example of how the current level of knowledge can be translated into predictions of predisposition. We also address challenges in the clinical implementation of the variants in germline DNA identified through cancer genome sequencing. We call for the international development of standards to facilitate the clinical use of germline information arising from diagnostic cancer genome sequencing.

Polymorphisms in the adenomatous polyposis coli (APC) gene and advanced colorectal adenoma risk

While germline mutations in the adenomatous polyposis coli (APC) gene cause the hereditary colon cancer syndrome (familial adenomatous polyposis (FAP)), the role of common germline APC variants in sporadic adenomatous polyposis remains unclear. We studied the association of eight APC single nucleotide polymorphisms (SNPs), possibly associated with functional consequences, and previously identified gene-environment (dietary fat intake and hormone replacement therapy (HRT) use) interactions, in relation to advanced colorectal adenoma in 758 cases and 767 sex- and race-matched controls, randomly selected from the screening arm of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Cases had at least one verified advanced adenoma of the distal colon; controls, a negative sigmoidoscopy. We did not observe an association between genotypes for any of the eight APC SNPs and advanced distal adenoma risk (P(global gene-based)=0.92). Frequencies of identified common haplotypes did not differ between cases and controls (P(global haplotype test)=0.97). However, the risk for advanced distal adenoma was threefold higher for one rare haplotype (cases: 2.7%; controls: 1.6%) (odds ratio (OR)=3.27; 95% confidence interval (CI)=1.08-9.88). The genetic association between D1822V and advanced distal adenoma was confined to persons consuming a high-fat diet (P(interaction)=0.03). Similar interactions were not observed with HRT use. In our large, nested case-control study of advanced distal adenoma and clinically verified adenoma-free controls, we observed no association between specific APC SNPs and advanced adenoma. Fat intake modified the APC D1822V-adenoma association, but further studies are warranted.

Colorectal cancer: epidemiology, risk factors, and health services

Colorectal carcinoma is the third most common cancer in the United States in both men and women but still remains the second leading cause of cancer-related deaths. The risk of developing colorectal cancer increases with age. Additional risk factors include family history of colorectal cancer, heredity conditions such as polyposis and hereditary nonpolyposis colorectal cancer, and personal history of inflammatory bowel disease, polyps, and cancers. Health services is a new scientific discipline that examines the quality of care, often at the population level, and may examine parts or the entire spectrum of care.

Engaging diverse communities participating in clinical trials: case examples from across Africa

BACKGROUND

In the advent of increasing international collaborative research involving participants drawn from populations with diverse cultural backgrounds, community engagement becomes very critical for the smooth conduction of the research. The African Malaria Network Trust (AMANET) is a pan-African non-governmental organization that sponsors and technically supports malaria vaccine trials in various African countries.

CASE DESCRIPTION

AMANET sponsored phase Ib or IIb clinical trials of several malaria vaccine candidates in various Africa countries. In Burkina Faso, Mali and Tanzania trials of the merozoite surface protein 3 -- in its Long Synthetic Peptide configuration (MSP3 LSP) -- were conducted. In Mali, the apical membrane antigen 1 (AMA1) was tested, while a hybrid of glutamate rich protein (GLURP) and MSP3 (GMZ2) was tested in Gabon. AMANET recognizes the importance of engaging with the communities from which trial participants are drawn, hence community engagement was given priority in all project activities conducted in the various countries.

DISCUSSION AND EVALUATION

Existing local social systems were used to engage the communities from which clinical trial participants were drawn. This article focuses on community engagement activities employed at various AMANET-supported clinical trial sites in different countries, highlighting subtle differences in the approaches used. The paper also gives some general pros and cons of community engagement.

CONCLUSIONS

Community engagement enables two-way sharing of accurate information and ideas between researchers and researched communities, which helps to create an environment conducive to smooth research activities with enhanced sense of research ownership by the communities.

Ethical and practical challenges surrounding genetic and genomic research in developing countries

The nature of some potential benefits and risks associated with genetic research is different from the types of potential benefits and risks associated with other types of health research such as clinical trials and biomedical research involving humans. Whereas most potential risks associated with biomedical research or clinical trials are mainly biological in nature, potential risks associated with genetic research are mainly of socioeconomic nature. Although the peculiarity of some of the aspects of genetic research and the complexity of the science involved are acknowledged, the extent to which these characteristics hinder firstly disclosure of information to participants and their communities and secondly comprehension of the disclosed information is a practical challenge that tends to be exaggerated in some cases. In this article, a brief overview of the various types of genetic research will be given in order to set the scene for some ethical and practical issues surrounding the research in developing countries that will be discussed subsequently. Case studies that illustrate some of the ethical and practical issues flagged will be given, followed by suggestions on possible ways of tackling some of the challenges in developing country settings. Nevertheless, genetic and genomic research could go a long way in providing knowledge that could be useful in the development of drugs and vaccines for many diseases affecting the developing countries.

3020insC insertion in NOD2/CARD15 gene, a prevalent variant associated with anti-Saccharomyces cerevisiae antibodies and ileal location of Crohn's disease in Tunisian population

OBJECTIVE

Our aim is to investigate the relation between CARD15 3020insC mutation, anti-Saccharomyces cerevisiae antibodies (ASCA) and disease phenotype, in Tunisian inflammatory bowel disease (IBD) patients.

MATERIALS

A hundred Tunisian patients with IBD (75 Crohn's disease CD and 25 ulcerative colitis UC) and 60 matched healthy controls were studied.

METHODS

CARD15 mutation was analysed by using an allele-specific polymerase chain reaction and sequencing. Assessment of ASCA in serum was performed by ELISA.

RESULTS

The frequency of the mutation was significantly higher in Crohn's disease than in control (p = 0,0005; OR = 20.45; CI 95% = 2.86-413.85) and did not differ statistically in UC group (p = 0, 05) from control. ASCAs were present in 60% of CD and 20, 8% of UC.

CONCLUSION

This study suggests that in northern Tunisian population, 3020insC mutation in NOD2/CARD15 gene is a prevalent mutation leading to the typical Crohn's disease including ileal location, stricturing and penetrating clinical types and ASCA expression.

Association of genetic variation in genes implicated in the beta-catenin destruction complex with risk of breast cancer

Aberrant Wnt/beta-catenin signaling leading to nuclear accumulation of the oncogene product beta-catenin is observed in a wide spectrum of human malignancies. The destruction complex in the Wnt/beta-catenin pathway is critical for regulating the level of beta-catenin in the cytoplasm and in the nucleus. Here, we report a comprehensive study of the contribution of genetic variation in six genes encoding the beta-catenin destruction complex (APC, AXIN1, AXIN2, CSNK1D, CSNK1E, and GSK3B) to breast cancer using a Mayo Clinic Breast Cancer Case-Control Study. A total of 79 candidate functional and tagging single nucleotide polymorphisms (SNP) were genotyped in 798 invasive cases and 843 unaffected controls. Of these, rs454886 in the APC tumor suppressor gene was associated with increased breast cancer risk (per allele odds ratio, 1.23; 95% confidence intervals, 1.05-1.43; P(trend) = 0.01). In addition, five SNPs in AXIN2 were associated with increased risk of breast cancer (P(trend) < 0.05). Haplotype-based tests identified significant associations between specific haplotypes in APC and AXIN2 (P < or = 0.03) and breast cancer risk. Further characterization of the APC and AXIN2 variants suggested that AXIN2 rs4791171 was significantly associated with risk in premenopausal (P(trend) = 0.0002) but not in postmenopausal women. The combination of our findings and numerous genetic and functional studies showing that APC and AXIN2 perform crucial tumor suppressor functions suggest that further investigation of the contribution of AXIN2 and APC SNPs to breast cancer risk are needed.

Functional characterization of the novel APC N1026S variant associated with attenuated familial adenomatous polyposis

BACKGROUND & AIMS

We identified the APC N1026S variant of unknown malignant potential in the adenomatous polyposis coli (APC) gene in a Spanish attenuated familial adenomatous polyposis (AFAP) family. The variant was located in the first of the 4 highly conserved 15-amino acid (AA) repeats within the beta-catenin union domain. Our aim was to determine its functional relevance to establish its pathogenicity.

METHODS

N1026S variant was analyzed in 22 members of the AFAP family studied, in 236 sporadic colorectal cancer cases, 203 matched controls, and 205 unrelated familial colorectal cancer cases. To assess its effects on beta-catenin binding, beta-catenin/Tcf-4-mediated transcription and beta-catenin subcellular distribution we performed affinity chromatography experiments, BIAcore 1000 (BIAcore AB, Uppsala, Sweden) assays, luciferase reporter assays, assessment of c-myc messenger RNA levels, and cell fractionation.

RESULTS

N1026S variant cosegregated with the disease in the AFAP family studied. None of the sporadic or familial cases as well as the controls analyzed was positive for the variant. N1026S variant completely precluded beta-catenin binding to the first 15-AA repeat and diminished it when all four 15-AA repeats were present. Expression of APC N1026S in SW480 and DLD-1 cells did not diminish beta-catenin/Tcf-4-mediated transcription as effectively as APC wild-type. N1026S did not decrease c-myc transcription in DLD1 cells and nuclear beta-catenin in SW480 cells as effectively as WT.

CONCLUSIONS

These findings strongly support a pathogenic role of the APC N1026S variant in the AFAP phenotype, reinforcing the importance of functional characterization of APC variants for genetic counseling.

Mutational screening of the APC gene in Chilean families with familial adenomatous polyposis: nine novel truncating mutations

PURPOSE

Familial adenomatous polyposis is characterized by the development of hundreds of adenomatous polyps located mainly in the colon and rectum. Patients with familial adenomatous polyposis who do not receive treatment will develop cancer before aged 40 years. This disease is caused by germline mutations in the adenomatous polyposis coli gene. Different studies have shown a correlation between the location of the mutation and the clinical phenotype, such as the grade of severity and/or the presence of extracolonic manifestations, such as desmoid tumors. This study was designed to identify germline mutation in the adenomatous polyposis coli gene in Chilean families with familial adenomatous polyposis.

METHODS

We examined the adenomatous polyposis coli gene in 24 Chilean families with familial adenomatous polyposis. The adenomatous polyposis coli gene was screened for mutations combining single strand conformation polymorphism technique, protein truncation test, and DNA sequencing.

RESULTS

We detected 17 different truncating mutations in 21 of 24 families (87.5 percent); 9 of these were novel. Fourteen mutations were detected in exon 15, being the most frequent c.3,927_3,931delAAAGA, found in 3 of 21 families (14 percent). Eight families (33 percent) showed at least one patient affected with desmoid tumors, presenting mutations between codons 849 and 1,533. Interestingly, two mutations, c.3,632dupA and c.3,783_3,784delTT, leading into a truncating protein at codons 1,216 and 1,274, were associated with almost 100 percent penetrance for desmoid tumors among relatives.

CONCLUSIONS

We achieved 87 percent mutation detection rate in adenomatous polyposis coli gene; more than 50 percent of them were novel. The high percentage of novel mutations found may be because of the genetic composition of the Chilean population, which is an admixture of Amerindian and Spaniards, and the scarce information in the literature about similar populations.

The APC E1317Q and I1307K polymorphisms in non-colorectal cancers

Mutation of the adenomatous polyposis coli (APC) gene is an important initiating factor in the early stages of the multi-step colorectal cancer (CRC) carcinogenesis. APC E1317Q and I1307K variants have been linked to CRC. The aim of this study was to examine the association of these variants with non-colorectal cancers. Mutation screening was performed using real-time PCR. The APC E1317Q variant was detected in 1.25% individuals undergoing testing. Among 2076 patients that were analyzed for this mutation, 404 had cancer outside of the colon. None of the non-colorectal cancer patients was a carrier of the E1317Q polymorphism. The I1307K variant was found in 32 subjects with non-CRC (7.9%). We conclude herein that the E1317Q gene variant in the APC gene is not found in cancers outside of the colon. The prevalence of the more common I1307K variant is similar to that of CRC.

How the I1307K adenomatous polyposis coli gene variant contributes in the assessment of risk of colorectal cancer, but not stomach cancer, in a Turkish population

Germline and somatic truncating mutations of the adenomatous polyposis coli gene (APC) are thought to initiate colorectal tumor formation in familial adenomatous polyposis syndrome and sporadic colorectal carcinogenesis, respectively. Recently, an isoleucine-lysine polymorphism at codon 1307 (I1307K) of the APC gene has been identified in 6-7% of the Ashkenazi Jewish population. To assess the risk of this common APC allelic variant in colorectal carcinogenesis, a cohort of unselected Turkish subjects with stomach or colorectal cancer (or both) was analyzed for the APC I1307K polymorphism. Genomic DNA was extracted from patients by obtaining all stomach and colon malign polipose tissues using nuclei lysis methods. Detection of the I1307K mutation was performed using the commercial Pronto APC kit according to the manufacturer's instructions. The APC I1307K allele was identified in 7 of 57 stomach carcinoma patients (12.3%; P > 0.05) and 30 of 56 colon carcinoma patients (53.6%; P < 0.05) using antigen-anticor interaction methods. Comparing the frequencies of the two separate population control groups, the APC I1307K allele is associated with an estimated relative risk of 1.9 for colorectal neoplasia. Furthermore, APC I1307K carriers had greater numbers of adenomas and colorectal cancers per patient than noncarriers. The conclusion is that the APC I1307K variant leads to increased adenoma formation and colorectal cancer. The estimated relative risk for carriers may justify specific clinical screening for Turkish people expected to harbor this allele, and genetic testing in the long term may significantly promote colorectal cancer prevention in this population.

Perceptions of genetic testing for cancer predisposition among Ashkenazi Jewish women

BACKGROUND

Clinical genetic testing can help identify individuals who are predisposed to a variety of diseases and conditions; thus, it is important to understand attitudes and perceptions of individuals who may consider or who may be offered such testing.

METHODS

We examined knowledge and attitudes about cancer genetic testing among 59 women of Ashkenazi Jewish descent (age 25-80 years) through six focus group discussions. Participants were asked about their knowledge and experience with hereditary conditions and genetic testing, and attitudes regarding risk management options, genetic privacy, and potential discrimination issues.

RESULTS

Although 54% reported having a personal and/or some family history of breast, ovarian, or colorectal cancer, none had undergone cancer genetic counseling or testing and few expressed an interest or intention in doing so. While most endorsed benefits of genetic testing for those with a significant cancer family history, women also expressed concerns over the possible distress of learning that one carried a cancer-predisposing mutation and suggested that increasing cancer screening practices may be preferable to having genetic testing. Participants doubted the ability of state genetic privacy legislation to protect against insurance or employment discrimination.

CONCLUSION

Findings underscore the need for public education on the broad range of benefits and limitations associated with genetic testing, in order to help consumers to appropriately interpret complex information and make decisions about these services.

The I1307K APC polymorphism in Ashkenazi Jews with colorectal cancer: clinical and pathologic features

Colorectal cancer is common in Ashkenazi Jews. The I1307K APC mutation occurs in 6-7% of Ashkenazi Jews and increases the risk of colorectal cancer. This study aimed to describe the clinical, pathologic and epidemiologic features of colorectal cancer in I1307K carriers to determine whether there were any features which might warrant individual screening for the mutation. In all, 215 Ashkenazi Jews with a personal history of colorectal cancer were enrolled. Clinical and family history, pathology reports, and slides were obtained and blood drawn for I1307K determination. The presence of the mutation was determined by PCR from white blood cell DNA. Colorectal cancer pathology slides were read in a blinded fashion. Of the 215 enrolled patients, 26 (12.1%) tested positive for I1307K. There was no difference in the pathologic features between colorectal cancers in Ashkenazi carriers compared to noncarriers. There was no difference in the age at diagnosis or history of second or other primaries. Carriers had an increased likelihood of having a first-degree relative with colorectal cancer (50%) compared to noncarriers (28%, P < 0.04). We could find no distinguishing feature other than family history that characterizes I1307K positive colorectal cancers. We could find no group of Ashkenazi Jews with colorectal cancer for whom screening for I1307K would be clinically useful.

Gene-gene, gene-environment & multiple interactions in colorectal cancer

This review comprehensively evaluates the influence of gene-gene, gene-environment and multiple interactions on the risk of colorectal cancer (CRC). Methods of studying these interactions and their limitations have been discussed herein. There is a need to develop biomarkers of exposure and of risk that are sensitive, specific, present in the pathway of the disease, and that have been clinically tested for routine use. The influence of inherited variation (polymorphism) in several genes has been discussed in this review; however, due to study limitations and confounders, it is difficult to conclude which ones are associated with the highest risk (either individually or in combination with environmental factors) to CRC. The majority of the sporadic cancer is believed to be due to modification of mutation risk by other genetic and/or environmental factors. Micronutrient deficiency may explain the association between low consumption of fruit/vegetables and CRC in human studies. Mitochondrial modulation by dietary factors influences the balance between cell renewal and death critical in colon mucosal homeostasis. Both genetic and epigenetic interactions are intricately dependent on each other, and collectively influence the process of colorectal tumorigenesis. The genetic and environmental interactions present a good prospect and a challenge for prevention strategies for CRC because they support the view that this highly prevalent cancer is preventable.

Mammary tumorigenesis in ApcMin/+ mice is enhanced by X irradiation with a characteristic age dependence

The Apc(Min/+) (Min) mouse is genetically predisposed to both intestinal and mammary tumorigenesis. We investigated age-related changes in the susceptibility of mice (before, during and after puberty) to radiation-induced mammary tumorigenesis using this model. Female Min and wild-type mice having the C57BL/6J background were irradiated with 2 Gy of X rays at 2, 5, 7 and 10 weeks and killed humanely at 18 weeks of age. Min mice irradiated at 7-10 weeks of age (after puberty) developed mammary tumors with squamous metaplasia, whereas their wild-type littermates did not. Interestingly, irradiation of Min mice at 2-5 weeks (before and during puberty, respectively) did not induce mammary tumors but rather cystic nodules with metaplasia. The mammary tumors exhibited increased nuclear beta-catenin protein and loss of the wild-type Apc allele. Our results show that susceptibility to radiation-induced mammary tumorigenesis increases after puberty in Min mice, suggesting that the tumorigenic effect of ionizing radiation targets the lobular-alveolar progenitor cells, which increase in number with age and are controlled by beta-catenin signaling.

APC I1307K and the Risk of Prostate Cancer

The kin-cohort design has been proposed as an alternative to traditional case-control and cohort measures to evaluate inherited susceptibility to cancer in population-based studies. Here, we used this design to evaluate inherited susceptibility to prostate cancer associated with APC I1307K using data from the Molecular Epidemiology of Colorectal Cancer study. Two techniques were used to compare the incidence of prostate cancer in APC I1307K carriers. First, we compared the incidence of prostate cancer in relatives of mutation carriers and noncarriers using standard techniques for survival analysis. Second, we used the marginal maximum likelihood method for kin-cohort analysis to infer the genotypes in the relatives. We also evaluated APC I1307K in 75 Ashkenazi Jewish individuals with prostate cancer from 27 families enrolled in the University of Michigan Prostate Cancer Genetic Study. We observed a slightly increased risk of prostate cancer in relatives of APC I1307K carriers, however, this difference was not statistically significant (hazard ratio, 1.6; 95% confidence intervals, 0.7-3.4). Similar conclusions were drawn using both techniques for kin-cohort analysis. APC I1307K was found in 7.4% of families genotyped, which is slightly higher than the allele prevalence reported in Ashkenazi Jews in the general population. In addition, we did not observe loss of heterozygosity at APC or a somatic mutation near APC I1307K using microdissected tumor DNA from mutation carriers enrolled in the Prostate Cancer Genetic Study. Overall, the evidence for an association between APC I1307K and prostate cancer is not compelling. APC I1307K is unlikely to play a clinically meaningful role in susceptibility to prostate cancer.

Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal-dominant colorectal cancer syndrome, caused by a germline mutation in the adenomatous polyposis coli (APC) gene, on chromosome 5q21. It is characterized by hundreds of adenomatous colorectal polyps, with an almost inevitable progression to colorectal cancer at an average age of 35 to 40 yr. Associated features include upper gastrointestinal tract polyps, congenital hypertrophy of the retinal pigment epithelium, desmoid tumors, and other extracolonic malignancies. Gardner syndrome is more of a historical subdivision of FAP, characterized by osteomas, dental anomalies, epidermal cysts, and soft tissue tumors. Other specified variants include Turcot syndrome (associated with central nervous system malignancies) and hereditary desmoid disease. Several genotype-phenotype correlations have been observed. Attenuated FAP is a phenotypically distinct entity, presenting with fewer than 100 adenomas. Multiple colorectal adenomas can also be caused by mutations in the human MutY homologue (MYH) gene, in an autosomal recessive condition referred to as MYH associated polyposis (MAP). Endoscopic screening of FAP probands and relatives is advocated as early as the ages of 10-12 yr, with the objective of reducing the occurrence of colorectal cancer. Colectomy remains the optimal prophylactic treatment, while the choice of procedure (subtotal vs proctocolectomy) is still controversial. Along with identifying better chemopreventive agents, optimizing screening of extracolonic cancers and applying new radiological and endoscopic technology to the diagnosis and management of extracolonic features are the major challenges for the future.

Colorectal polyps in carriers of the APC I1307K polymorphism

PURPOSE

The probability of colorectal cancer is moderately increased among carriers of the APC I1307K polymorphism. However, it is not known if endoscopic surveillance of this high-risk group is warranted. The prevalence of polyps and adenomas in specimens of colorectal cancer who are carriers and noncarriers of the APC I1307K polymorphism is compared.

METHOD

Prevalence of adenomatous polyps in the pathology specimens of the study participants, stratified by their APC I1307K polymorphism status, was studied in 900 consecutive cases of colorectal cancer diagnosed in northern Israel between 1998 and 2002, within the framework of a population-based, case-controlled study (MECC Study).

RESULTS

The APC I1307K mutation was detected in 78 colorectal cancer cases (8.7 percent) of the study population. Prevalence was higher among Ashkenazi Jews (11.2 percent) than among non-Ashkenazi Jews (2.7 percent) or Arabs (3.1 percent). After adjustment for age, APC I1307K carriers were significantly more likely than noncarriers to have polyps in their surgical specimen (51.3 percent vs. 32.6 percent, P = 0.002). Adenomas with a tubular component (either tubular adenomas or tubulovillous adenomas), but not villous adenomas, were significantly more frequent among carriers (37.2 percent vs. 23.6 percent, P = 0.005).

CONCLUSION

Together with former evidence of I1307K being a risk factor for colorectal cancer, these data suggest that colonoscopic surveillance for colorectal adenomas and cancer may be warranted in I1307K carriers, even in the absence of other identifiable risk factors.

Factors Influencing Uptake of Genetic Testing For Colorectal Cancer Risk in an Australian Jewish Population

There is a significant excess of colorectal cancer in the Australian Ashkenazi Jewish community. This excess can partially be attributed to inherited factors that are over represented in this population, such as the APC variant I1307K, which is associated with a modest increase in colorectal cancer risk. There is currently only sporadic clinical genetic testing offered for this variant, as neither the exact increase in cancer risk and therefore the appropriate screening strategies for I1307K carriers, nor the acceptability of such testing in Jewish communities have been determined. This study reports a high acceptability of such genetic testing within a community sample of 300 Australian Jewish individuals--94% of participants would have a test for predisposition to colorectal cancer and a majority would make this decision based on the desire for information for their families and to decrease their own cancer risk. Some concerns were noted about genetic testing for cancer predisposition, including insurance discrimination, test accuracy and confidentiality.

Inherited susceptibility to colorectal cancer

The principal Mendelian disorders predisposing to colorectal cancer are familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). FAP is due to mutations in the APC gene. HNPCC is due to a mutation in one of at least five mismatch repair genes. Identification of individuals with these conditions is important because colon cancer will occur in approximately 80% and onset is early. For FAP, protein truncation testing will identify the vast majority of mutations. For HNPCC, 80%-95% can be identified by microsatellite instability testing. A current U.S. study reports that 12% of consecutive colorectal cancers have high microsatellite instability and that, of this 12%, 25% have detectable mutations of MLH1, MSH2, or MSH6. Potential benefits of identification include improved compliance with recommended surveillance, early detection of polyps, reduction in cancer mortality, offering of testing to relatives, and reassurance for relatives found to be negative with attendant savings in the time and expense of surveillance.

Endoscopic management of familial colonic neoplasia

Heredity plays an important causative role in a large percentage of colorectal cancers. Clinical recognition of the hereditary polyposis syndromes, hereditary nonpolyposis colorectal cancer, and common familial colorectal cancer is essential because screening, surveillance, and treatment among affected individuals and their family members differs from that recommended for the general population. More intensive cancer screening and surveillance is required if premature death is to be avoided. Genetic testing is commercially available for most of the hereditary colorectal cancer syndromes and can greatly facilitate the management of patients if properly undertaken.