Differential methylation of G-protein coupled receptor signaling genes in gastrointestinal neuroendocrine tumors

Neuroendocrine tumors (NETs) of the small intestine undergo large chromosomal and methylation changes. The objective of this study was to identify methylation differences in NETs and consider how the differentially methylated genes may impact patient survival. Genome-wide methylation and chromosomal copy number variation (CNV) of NETs from the small intestine and appendix were measured. Tumors were divided into three molecular subtypes according to CNV results: chromosome 18 loss (18LOH), Multiple CNV, and No CNV. Comparison of 18LOH tumors with MultiCNV and NoCNV tumors identified 901 differentially methylated genes. Genes from the G-protein coupled receptor (GPCR) pathways are statistically overrepresented in the differentially methylated genes. One of the highlighted genes from the GPCR pathway is somatostatin (SST), a clinical target for NETs. Patient survival based on low versus high methylation in all samples identified four significant genes (p < 0.05) OR2S2, SMILR, RNU6-653P, and AC010543.1. Within the 18LOH molecular subtype tumors, survival differences were identified in high versus low methylation of 24 genes. The most significant is TRHR (p < 0.01), a GPCR with multiple FDA-approved drugs. By separating NETs into different molecular subtypes based on chromosomal changes, we find that multiple GPCRs and their ligands appear to be regulated through methylation and correlated with survival. These results suggest opportunities for better treatment strategies for NETs based on molecular features.

FANCM c5791C>T stopgain mutation (rs144567652) is a familial colorectal cancer risk factor

Purpose

While familial aggregation of colorectal cancer (CRC) is recognized, the majority of the germline predisposition factors remain unidentified, and many high‐risk CRC pedigrees remain unexplained by known risk variants. Fanconi Anemia genes have been recognized to be associated with cancer risk. Notably, FANCM (OMIM 609644) variants have been reported to confer risk for CRC and breast cancer.

Methods

Exome sequencing of CRC‐affected cousins in a set of 47 independent extended high‐risk CRC pedigrees identified a candidate set of rare, shared variants. Variants were tested for association with risk in 744 Utah CRC cases and 1525 controls, and for segregation with CRC in affected relatives.

Results

A FANCM stopgain variant was observed in two CRC‐affected cousin pairs, each from an independent Utah high‐risk pedigree, and yielded a nonsignificant, but elevated OR = 2.05 in a set of Utah cases and controls. Segregation of the variant to other related CRC‐affected cases was observed in the two extended pedigrees.

Conclusion

A rare stopgain variant in FANCM (rs144567652) that is recognized as a breast cancer predisposition variant, and that has previously been proposed, but not confirmed, as a CRC predisposition variant, is validated here as a risk factor for familial CRC.

Associations of Tobacco and Alcohol Use with Risk of Neuroendocrine Tumors of the Small Intestine in Utah

BACKGROUND

Incidence of small-intestine neuroendocrine tumors (SINT) has been increasing in the United States over the past 40 years, with higher incidence in Utah than elsewhere. As information about how these tumors arise is limited, elucidating lifestyle factors associated with SINT in a statewide cohort could potentially identify those at risk to help mitigate their effects.

METHODS

Cases of SINT with a carcinoid histology (8240 or 8241) diagnosed in Utah from 1996 to 2014 with no prior history of cancer within 5 years (n = 433) were matched to population controls (1:10 ratio). Tobacco and alcohol exposures before case diagnosis were identified from International Classification of Diseases codes in statewide medical records and from self-reported data captured at patient encounters beginning in 1996. Multivariate logistic regression was used to estimate risk of SINT associated with tobacco and alcohol in cases compared with controls.

RESULTS

An increased risk of SINT was observed in tobacco-exposed individuals compared with unexposed [OR, 1.44; 95% confidence interval (CI), 1.11-1.86; P = 0.006]. Those who were exposed to alcohol exhibited an increased risk of SINT (OR, 1.62; 95% CI, 1.05-2.49; P = 0.03).

CONCLUSIONS

This study supports tobacco and alcohol use as risk factors for SINT, independent of family history. However, low rates of smoking and alcohol use in Utah coupled with higher rates of SINT suggest other factors may contribute to development of these tumors.

IMPACT

Although tobacco and alcohol modestly contribute to risk, our study suggests in addition to greater detection of tumors, other as-of-yet undefined exposures may drive rising SINT incidence.

Association of Sulindac and Erlotinib vs Placebo With Colorectal Neoplasia in Familial Adenomatous Polyposis: Secondary Analysis of a Randomized Clinical Trial

Importance

Patients with familial adenomatous polyposis (FAP) are at markedly increased risk for colorectal polyps and cancer. A combination of sulindac and erlotinib led to a 71% reduction in duodenal polyp burden in a phase 2 trial.

Objective

To evaluate effect of sulindac and erlotinib on colorectal adenoma regression in patients with FAP.

Design, Setting, and Participants

Prespecified secondary analysis for colorectal adenoma regression was carried out using data from a double-blind, randomized, placebo-controlled trial, enrolling 92 patients with FAP, conducted from July 2010 to June 2014 in Salt Lake City, Utah.

Interventions

Patients were randomized to sulindac, 150 mg twice daily, and erlotinib, 75 mg daily (n = 46), vs placebo (n = 46) for 6 months.

Main Outcomes and Measurements

The total number of polyps in the intact colorectum, ileal pouch anal anastomosis, or ileo-rectum were recorded at baseline and 6 months. The primary outcomes were change in total colorectal polyp count and percentage change in colorectal polyps, following 6 months of treatment.

Results

Eighty-two randomized patients (mean [SD] age, 40 [13] years; 49 [60%] women) had colorectal polyp count data available for this secondary analysis: 22 with intact colon, 44 with ileal pouch anal anastomosis and 16 with ileo-rectal anastomosis; 41 patients received sulindac/erlotinib and 41 placebo. The total colorectal polyp count was significantly different between the placebo and sulindac-erlotinib group at 6 months in patients with net percentage change of 69.4% in those with an intact colorectum compared with placebo (95% CI, 28.8%-109.2%; P = .009).

Conclusion and Relevance

In this double-blind, placebo-controlled, randomized trial we showed that combination treatment with sulindac and erlotinib compared with placebo resulted in significantly lower colorectal polyp burden after 6 months of treatment. There was a reduction in polyp burden in both those with an entire colorectum and those with only a rectal pouch or rectum.

Trial Registration

clinicaltrials.gov Identifier: NCT01187901.

Predictors of Response Outcomes for Research Recruitment Through a Central Cancer Registry: Evidence From 17 Recruitment Efforts for Population-Based Studies

When recruiting research participants through central cancer registries, high response fractions help ensure population-based representation. We conducted multivariable mixed-effects logistic regression to identify case and study characteristics associated with making contact with and obtaining cooperation of Utah cancer cases using data from 17 unique recruitment efforts undertaken by the Utah Cancer Registry (2007-2016) on behalf of the following studies: A Population-Based Childhood Cancer Survivors Cohort Study in Utah, Comparative Effectiveness Analysis of Surgery and Radiation for Prostate Cancer (CEASAR Study), Costs and Benefits of Follow-up Care for Adolescent and Young Adult Cancers, Study of Exome Sequencing for Head and Neck Cancer Susceptibility Genes, Genetic Epidemiology of Chronic Lymphocytic Leukemia, Impact of Remote Familial Colorectal Cancer Risk Assessment and Counseling (Family CARE Project), Massively Parallel Sequencing for Familial Colon Cancer Genes, Medullary Thyroid Carcinoma (MTC) Surveillance Study, Osteosarcoma Surveillance Study, Prostate Cancer Outcomes Study, Risk Education and Assessment for Cancer Heredity Project (REACH Project), Study of Shared Genomic Segment Analysis and Tumor Subtyping in High-Risk Breast-Cancer Gene Pedigrees, Study of Shared Genomic Segment Analysis for Localizing Multiple Myeloma Genes. Characteristics associated with lower odds of contact included Hispanic ethnicity (odds ratio (OR) = 0.34, 95% confidence interval (CI): 0.27, 0.41), nonwhite race (OR = 0.46, 95% CI: 0.35, 0.60), and younger age at contact. Years since diagnosis was inversely associated with making contact. Nonwhite race and age ≥60 years had lower odds of cooperation. Study features with lower odds of cooperation included longitudinal design (OR = 0.50, 95% CI: 0.41, 0.61) and study brochures (OR = 0.70, 95% CI: 0.54, 0.90). Increased odds of cooperation were associated with including a questionnaire (OR = 3.19, 95% CI: 1.54, 6.59), postage stamps (OR = 1.60, 95% CI: 1.21, 2.12), and incentives (OR = 1.62, 95% CI: 1.02, 2.57). Among cases not responding after the first contact, odds of eventual response were lower when >10 days elapsed before subsequent contact (OR = 0.71, 95% CI: 0.59, 0.85). Obtaining high response is challenging, but study features identified in this analysis support better results when recruiting through central cancer registries.

Predictors of Response Outcomes for Research Recruitment Through a Central Cancer Registry: Evidence From 17 Recruitment Efforts for Population-Based Studies

When recruiting research participants through central cancer registries, high response fractions help ensure population-based representation. We conducted multivariable mixed-effects logistic regression to identify case and study characteristics associated with making contact with and obtaining cooperation of Utah cancer cases using data from 17 unique recruitment efforts undertaken by the Utah Cancer Registry (2007-2016) on behalf of the following studies: A Population-Based Childhood Cancer Survivors Cohort Study in Utah, Comparative Effectiveness Analysis of Surgery and Radiation for Prostate Cancer (CEASAR Study), Costs and Benefits of Follow-up Care for Adolescent and Young Adult Cancers, Study of Exome Sequencing for Head and Neck Cancer Susceptibility Genes, Genetic Epidemiology of Chronic Lymphocytic Leukemia, Impact of Remote Familial Colorectal Cancer Risk Assessment and Counseling (Family CARE Project), Massively Parallel Sequencing for Familial Colon Cancer Genes, Medullary Thyroid Carcinoma (MTC) Surveillance Study, Osteosarcoma Surveillance Study, Prostate Cancer Outcomes Study, Risk Education and Assessment for Cancer Heredity Project (REACH Project), Study of Shared Genomic Segment Analysis and Tumor Subtyping in High-Risk Breast-Cancer Gene Pedigrees, Study of Shared Genomic Segment Analysis for Localizing Multiple Myeloma Genes. Characteristics associated with lower odds of contact included Hispanic ethnicity (odds ratio (OR) = 0.34, 95% confidence interval (CI): 0.27, 0.41), nonwhite race (OR = 0.46, 95% CI: 0.35, 0.60), and younger age at contact. Years since diagnosis was inversely associated with making contact. Nonwhite race and age ≥60 years had lower odds of cooperation. Study features with lower odds of cooperation included longitudinal design (OR = 0.50, 95% CI: 0.41, 0.61) and study brochures (OR = 0.70, 95% CI: 0.54, 0.90). Increased odds of cooperation were associated with including a questionnaire (OR = 3.19, 95% CI: 1.54, 6.59), postage stamps (OR = 1.60, 95% CI: 1.21, 2.12), and incentives (OR = 1.62, 95% CI: 1.02, 2.57). Among cases not responding after the first contact, odds of eventual response were lower when >10 days elapsed before subsequent contact (OR = 0.71, 95% CI: 0.59, 0.85). Obtaining high response is challenging, but study features identified in this analysis support better results when recruiting through central cancer registries.

Small RNA sequencing of sessile serrated polyps identifies microRNA profile associated with colon cancer

Sessile serrated adenoma/polyps (SSA/Ps) of the colon account for 20-30% of all colon cancers. Small non-coding RNAs, including microRNAs (miRNAs), may function as oncogenes or tumor suppressor genes involved in cancer development. Small RNA sequencing (RNA-seq) was used to characterize miRNA profiles in SSA/Ps, hyperplastic polyps (HPs), adenomatous polyps and paired uninvolved colon. Our 108 small RNA-seq samples' results were compared to small RNA-seq data from 212 colon cancers from the Cancer Genome Atlas. Twenty-three and six miRNAs were differentially expressed in SSA/Ps compared to paired uninvolved colon and HPs, respectively. Differential expression of MIR31-5p, MIR135B-5p and MIR378A-5p was confirmed by RT-qPCR. SSA/P-specific miRNAs are similarly expressed in colon cancers containing genomic aberrations described in serrated cancers. Correlation of miRNA expression with consensus molecular subtypes suggests more than one subtype is associated with the serrated neoplasia pathway. Canonical pathway analysis suggests many of these miRNAs target growth factor signaling pathways.

Variables affecting penetrance of gastric and duodenal phenotype in familial adenomatous polyposis patients

BACKGROUND

Patients with familial adenomatous polyposis (FAP) frequently undergo colectomy to reduce the 70 to 90% lifetime risk of colorectal cancer. After risk-reducing colectomy, duodenal cancer and complications from duodenal surgeries are the main cause of morbidity. Our objective was to prospectively describe the duodenal and gastric polyp phenotype in a cohort of 150 FAP patients undergoing pre-screening for a chemoprevention trial and analyze variables that may affect recommendations for surveillance.

METHODS

Individuals with a diagnosis of FAP underwent prospective esophagogastroduodenoscopy using a uniform system of mapping of size and number of duodenal polyps for a 10 cm segment. Gastric polyps were recorded as the total number.

RESULTS

The distribution of the count and sum diameter of duodenal polyps were statistically different in two genotype groups, those with APC mutations associated with classic FAP had a greater count (median 17) and sum diameter of polyps (median 32 mm) than those with APC mutations associated with attenuated FAP (median count 4 and median sum diameter of 7 mm) (p < 0.0001). The number of gastric polyps did not differ based on genotype (p = 0.67) but advancing age correlated with severity of gastric polyposis (p = 0.019). Spigelman (modified) staging of II or greater was found in 88% of classic FAP patients and 48% attenuated FAP patients. Examples of severe and mild upper GI phenotype are observed in patients with identical APC mutations, showing that the APC mutation location is not absolutely predictive of an upper GI phenotype.

CONCLUSIONS

Most FAP patients have duodenal and gastric polyps which become more prevalent and advanced with age. Standard upper endoscopic surveillance is recommended based on personal history independent of APC mutation location.

TRIAL REGISTRATION

NCT 01187901 registered August 24, 2010, prospective to enrollment.

Pancreatic cancer as a sentinel for hereditary cancer predisposition

BACKGROUND

Genes associated with hereditary breast and ovarian cancer (HBOC) and colorectal cancer (CRC) predisposition have been shown to play a role in pancreatic cancer susceptibility. Growing evidence suggests that pancreatic cancer may be useful as a sentinel cancer to identify families that could benefit from HBOC or CRC surveillance, but to date pancreatic cancer is only considered an indication for genetic testing in the context of additional family history.

METHODS

Preliminary data generated at the Huntsman Cancer Hospital (HCH) included variants identified on a custom 34-gene panel or 59-gene panel including both known HBOC and CRC genes for respective sets of 66 and 147 pancreatic cancer cases, unselected for family history. Given the strength of preliminary data and corresponding literature, 61 sequential pancreatic cancer cases underwent a custom 14-gene clinical panel. Sequencing data from HCH pancreatic cancer cases, pancreatic cancer cases of the Cancer Genome Atlas (TCGA), and an unselected pancreatic cancer screen from the Mayo Clinic were combined in a meta-analysis to estimate the proportion of carriers with pathogenic and high probability of pathogenic variants of uncertain significance (HiP-VUS).

RESULTS

Approximately 8.6% of unselected pancreatic cancer cases at the HCH carried a variant with potential HBOC or CRC screening recommendations. A meta-analysis of unselected pancreatic cancer cases revealed that approximately 11.5% carry a pathogenic variant or HiP-VUS.

CONCLUSION

With the inclusion of both HBOC and CRC susceptibility genes in a panel test, unselected pancreatic cancer cases act as a useful sentinel cancer to identify asymptomatic at-risk relatives who could benefit from relevant HBOC and CRC surveillance measures.

A role for the vitamin D pathway in non-intestinal lesions in genetic and carcinogen models of colorectal cancer and in familial adenomatous polyposis

Vitamin D is implicated in the etiology of cancers of the gastrointestinal tract, usually characterized by alteration in the APC/β-catenin/TCF tumor suppressor pathway. The vitamin D receptor (VDR) is also implicated in cardiovascular and skin diseases as well as in immunity. Activated VDR can indirectly alter β-catenin nuclear localization and directly suppress β-catenin/TCF mediated transcriptional activity. We treated VDR null mice with the carcinogen azoxymethane (AOM) and generated mice bearing a mutated APC (hypomorph) on a VDR null background (Apc^1638N/+Vdr^−/−). VDR null mice do not develop GI or extra-colonic tumors but loss of VDR decreased intestinal tumor latency and increased progression to adenocarcinoma in both models. AOM treatment of VDR null mice also caused squamous cell carcinoma of the anus. Although levels and distribution of total or activated β-catenin in the epithelial component of tumors were unaffected by loss of VDR, β-catenin dependent cyclin D1 expression was affected suggesting a direct VDR effect on β-catenin co-activator activity. Extra-colonic mucosa manifestations in Apc^1638N/+Vdr^−/− animals included increased nuclear β-catenin in submucosal stromal cells, spleno- and cardiomegaly and large epidermoid cysts characteristic of the FAP variant, Gardner's syndrome. Consistent with this, SNPs in the VDR, vitamin D binding protein and CYP24 as well as mutations in APC distal to codon 850 were strongly associated with Gardners syndrome in a cohort of 457 FAP patients, This work suggests that alterations in the vitamin D/VDR axis are important in Gardner's syndrome, as well as in the etiology of anal cancer.

Population-based description of familial clustering of Chiari malformation Type I

OBJECTIVE

A population-based genealogical resource with linked medical data was used to define the observed familial clustering of Chiari malformation Type I (CM-I).

METHODS

All patients with CM-I were identified from the 2 largest health care providers in Utah; those patients with linked genealogical data were used to test hypotheses regarding familial clustering. Relative risks (RRs) in first-, second-, and third-degree relatives were estimated using internal cohort-specific CM-I rates; the Genealogical Index of Familiality (GIF) test was used to test for an excess of relationships between all patients with CM-I compared with the expected distribution of relationships for matched control sets randomly selected from the resource. Pedigrees with significantly more patients with CM-I than expected (p < 0.05) based on internal rates were identified.

RESULTS

A total of 2871 patients with CM-I with at least 3 generations of genealogical data were identified. Significantly increased RRs were observed for first- and third-degree relatives (RR 4.54, p < 0.001, and RR 1.36, p < 0.001, respectively); the RR for second-degree relatives was elevated, but not significantly (RR 1.20, p = 0.13). Significant excess pairwise relatedness was observed among the patients with CM-I (p < 0.001), and borderline significant excess pairwise relatedness was observed when all relationships closer than first cousins were ignored (p = 0.051). Multiple extended high-risk CM-I pedigrees with closely and distantly related members were identified.

CONCLUSIONS

This population-based description of the familial clustering of 2871 patients with CM-I provided strong evidence for a genetic contribution to a predisposition to CM-I.

Primary Ovarian Insufficiency and Azoospermia in Carriers of a Homozygous PSMC3IP Stop Gain Mutation

CONTEXT

The etiology of primary ovarian insufficiency (POI) remains unknown in most cases.

OBJECTIVE

We sought to identify the genes causing POI.

DESIGN

The study was a familial genetic study.

SETTING

The study was performed at two academic institutions.

PATIENTS

We identified a consanguineous Yemeni family in which four daughters had POI. A brother had azoospermia.

INTERVENTION

DNA was subjected to whole genome sequencing. Shared regions of homozygosity were identified using Truploidy and prioritized using the Variant Annotation, Analysis, and Search Tool with control data from 387 healthy subjects. Imaging and quantification of protein localization and mitochondrial function were examined in cell lines.

MAIN OUTCOME

Homozygous recessive gene variants shared by the four sisters.

RESULTS

The sisters shared a homozygous stop gain mutation in exon 6 of PSMC3IP (c.489 C>G, p.Tyr163Ter) and a missense variant in exon 1 of CLPP (c.100C>T, p.Pro34Ser). The affected brother also carried the homozygous PSMC3IP mutation. Functional studies demonstrated mitochondrial fragmentation in cells infected with the CLPP mutation. However, no abnormality was found in mitochondrial targeting or respiration.

CONCLUSIONS

The PSMC3IP mutation provides additional evidence that mutations in meiotic homologous recombination and DNA repair genes result in distinct female and male reproductive phenotypes, including delayed puberty and primary amenorrhea caused by POI (XX gonadal dysgenesis) in females but isolated azoospermia with normal pubertal development in males. The findings also suggest that the N-terminal missense mutation in CLPP does not cause substantial mitochondrial dysfunction or contribute to ovarian insufficiency in an oligogenic manner.

Chemoprevention with Cyclooxygenase and Epidermal Growth Factor Receptor Inhibitors in Familial Adenomatous Polyposis Patients: mRNA Signatures of Duodenal Neoplasia

To identify gene expression biomarkers and pathways targeted by sulindac and erlotinib given in a chemoprevention trial with a significant decrease in duodenal polyp burden at 6 months (P < 0.001) in familial adenomatous polyposis (FAP) patients, we biopsied normal and polyp duodenal tissues from patients on drug versus placebo and analyzed the RNA expression. RNA sequencing was performed on biopsies from the duodenum of FAP patients obtained at baseline and 6-month endpoint endoscopy. Ten FAP patients on placebo and 10 on sulindac and erlotinib were selected for analysis. Purity of biopsied polyp tissue was calculated from RNA expression data. RNAs differentially expressed between endpoint polyp and paired baseline normal were determined for each group and mapped to biological pathways. Key genes in candidate pathways were further validated by quantitative RT-PCR. RNA expression analyses of endpoint polyp compared with paired baseline normal for patients on placebo and drug show that pathways activated in polyp growth and proliferation are blocked by this drug combination. Directly comparing polyp gene expression between patients on drug and placebo also identified innate immune response genes (IL12 and IFNγ) preferentially expressed in patients on drug. Gene expression analyses from tissue obtained at endpoint of the trial demonstrated inhibition of the cancer pathways COX2/PGE2, EGFR, and WNT. These findings provide molecular evidence that the drug combination of sulindac and erlotinib reached the intended tissue and was on target for the predicted pathways. Furthermore, activation of innate immune pathways from patients on drug may have contributed to polyp regression. Cancer Prev Res; 11(1); 4-15. ©2017 AACRSee related editorial by Shureiqi, p. 1.

Outcomes and complications of radiation therapy in patients with familial adenomatous polyposis

BACKGROUND

The outcomes, complications, and rates of secondary malignancies from radiation therapy (RT) are not known for patients with familial adenomatous polyposis (FAP).

METHODS

We queried the Hereditary Gastrointestinal Cancer Registry (HGCR) for patients with FAP who received RT. Outcomes assessed included acute and late treatment toxicity and secondary malignancies.

RESULTS

We identified 15 patients undergoing 18 treatment courses. Median follow-up was 3.1 years after RT. Treated sites included rectal cancer, desmoid, prostate cancer, breast cancer, melanoma, medulloblastoma, gastric cancer, and glioma. Secondary tumors occurred in two patients: a medulloblastoma was diagnosed in a patient treated for glioma, and a desmoid tumor was diagnosed in a patient treated for rectal cancer. All nine patients treated with intra-abdominal or pelvic RT had prior prophylactic proctocolectomies, yet only one patient experienced grade 3 gastrointestinal toxicity. Common Terminology Criteria for Adverse Events version 4 (CTCAE v4) toxicities were grade 1 in seven treatment courses (39%), grade 2 in five courses (28%), and grade 3 in two courses (11%).

CONCLUSIONS

In this cohort, RT was well tolerated with adverse effects comparable with non-FAP patients. Secondary in-field tumors occurred in 2 of 15 patients and their increased risk in this cohort was likely due to prior predilection from FAP itself, although an increased role of RT cannot be ruled out.

POLR2C Mutations Are Associated With Primary Ovarian Insufficiency in Women

CONTEXT

Primary ovarian insufficiency (POI) results from a premature loss of oocytes, causing infertility and early menopause. The etiology of POI remains unknown in a majority of cases.

OBJECTIVE

To identify candidate genes in families affected by POI.

DESIGN

This was a family-based genetic study.

SETTING

The study was performed at two academic institutions.

PATIENTS AND OTHER PARTICIPANTS

A family with four generations of women affected by POI (n = 5). Four of these women, three with an associated autoimmune diagnosis, were studied. The controls (n = 387) were recruited for health in old age.

INTERVENTION

Whole-genome sequencing was performed.

MAIN OUTCOME MEASURE

Candidate genes were identified by comparing gene mutations in three family members and 387 control subjects analyzed simultaneously using the pedigree Variant Annotation, Analysis and Search Tool. Data were also compared with that in publicly available databases.

RESULTS

We identified a heterozygous nonsense mutation in a subunit of RNA polymerase II (POLR2C) that synthesizes messenger RNA. A rare sequence variant in POLR2C was also identified in one of 96 women with sporadic POI. POLR2C expression was decreased in the proband compared with women with POI from another cause. Knockdown in an embryonic carcinoma cell line resulted in decreased protein production and impaired cell proliferation.

CONCLUSIONS

These data support a role for RNA polymerase II mutations as candidates in the etiology of POI. The current data also support results from genome-wide association studies that hypothesize a role for RNA polymerase II subunits in age at menopause in the population.

Abstract LB-074: Regression of duodenal neoplasia in familial adenomatous polyposis patients using COX and EGFR inhibition: A randomized placebo-controlled trial

The objective of this trial was to test the effect of a combination of COX and EGFR inhibition on duodenal adenoma progression in patients with familial adenomatous polyposis (FAP). FAP is caused by mutations in the APC gene and is characterized by the development of hundreds of colorectal adenomas and colorectal cancer. FAP patients are also at increased risk for duodenal neoplasia with a ∼10% lifetime risk of duodenal carcinoma. Surgical and endoscopic management of duodenal neoplasia is difficult and chemoprevention has not been successful. Preclinical data has illustrated that a combination of cyclooxygenase (COX) and epidermal growth factor (EGFR) inhibition diminishes small intestinal adenoma development by 87% in mice with germline Apc mutations. Therefore, we conducted a double blind, randomized, placebo-controlled trial in which FAP patients received combination therapy with 150 mg sulindac twice per day and 75 mg erlotinib daily or placebo for 6 months (NCT01187901). The total number and diameter of polyps in a 10cm segment of the proximal duodenum were mapped at baseline and 6 months. The primary outcome was change in total polyp burden, calculated as the sum of the diameters of polyps. We also evaluated RNA expression in duodenal tissue and polyps at endpoint from 10 patients on drug and 10 patients on placebo by RNA sequencing. Seventy-three randomized patients were included in the intention to treat analysis. Over six months, the median change in total duodenal polyp burden was an increase of 8.0 mm from baseline burden in the placebo group (23.0 to 31.0 mm) and the median change in the sulindac-erlotinib group was a decrease of 8.5 mm (29.0 to 19.5 mm). The estimated net difference in change between the two groups was -19.0 mm (95% CI: -32.0, -10.9; P&lt;0.001). Grade 1 and 2 adverse events were more common in the sulindac-erlotinib group, with an acne-like rash observed in 87% of patients receiving treatment and 20% of patients receiving placebo (P&lt;0.001). We identified ∼ 750 differentially expressed genes (fold ≥ 2, false discovery rate &lt; 0.05) in polyps from patients on placebo as compared with patient-matched normal duodenum which were unchanged in polyps from patients on drug. These differentially expressed genes suggested increased EGFR, prostaglandin E2 (PGE2 or COX2) and WNT signaling in duodenal polyps from patients on placebo but not on drug. In duodenal tissue from patients on drug when compared to tissue from patients on placebo, we identified differentially expressed genes suggestive of a reactivated immune response including interferon gamma and interleukin 12 signaling; a possible mechanism for the regression of duodenal polyps observed in drug treated patients. In conclusion, combined chemoprevention with sulindac and erlotinib in FAP patients is effective to lower duodenal polyp burden, block COX2 and EGFR activity, and may reactivate immune surveillance. At the doses tested, however, frequent adverse events may limit the use of these medications.

Part of this abstract was presented as part of a preliminary presentation.

Citation Format: Deborah W. Neklason, Don A. Delker, Kenneth M. Boucher, Priyanka Kanth, Kathryn Byrne, Philip Bernard, Wade Samowitz, Michelle W. Done, Therese Berry, Lisa Pappas, Laurel Smith, Danielle Sample, Rian Davis, Matthew K. Topham, Randall W. Burt, Scott K. Kuwada, N Jewel Samadder. Regression of duodenal neoplasia in familial adenomatous polyposis patients using COX and EGFR inhibition: A randomized placebo-controlled trial. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-074.

Point Mutations in Exon 1B of APC Reveal Gastric Adenocarcinoma and Proximal Polyposis of the Stomach as a Familial Adenomatous Polyposis Variant

Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS) is an autosomal-dominant cancer-predisposition syndrome with a significant risk of gastric, but not colorectal, adenocarcinoma. We mapped the gene to 5q22 and found loss of the wild-type allele on 5q in fundic gland polyps from affected individuals. Whole-exome and -genome sequencing failed to find causal mutations but, through Sanger sequencing, we identified point mutations in APC promoter 1B that co-segregated with disease in all six families. The mutations reduced binding of the YY1 transcription factor and impaired activity of the APC promoter 1B in luciferase assays. Analysis of blood and saliva from carriers showed allelic imbalance of APC, suggesting that these mutations lead to decreased allele-specific expression in vivo. Similar mutations in APC promoter 1B occur in rare families with familial adenomatous polyposis (FAP). Promoter 1A is methylated in GAPPS and sporadic FGPs and in normal stomach, which suggests that 1B transcripts are more important than 1A in gastric mucosa. This might explain why all known GAPPS-affected families carry promoter 1B point mutations but only rare FAP-affected families carry similar mutations, the colonic cells usually being protected by the expression of the 1A isoform. Gastric polyposis and cancer have been previously described in some FAP-affected individuals with large deletions around promoter 1B. Our finding that GAPPS is caused by point mutations in the same promoter suggests that families with mutations affecting the promoter 1B are at risk of gastric adenocarcinoma, regardless of whether or not colorectal polyps are present.

Gene Signature in Sessile Serrated Polyps Identifies Colon Cancer Subtype

Sessile serrated colon adenoma/polyps (SSA/P) are found during routine screening colonoscopy and may account for 20% to 30% of colon cancers. However, differentiating SSA/Ps from hyperplastic polyps (HP) with little risk of cancer is challenging and complementary molecular markers are needed. In addition, the molecular mechanisms of colon cancer development from SSA/Ps are poorly understood. RNA sequencing (RNA-Seq) was performed on 21 SSA/Ps, 10 HPs, 10 adenomas, 21 uninvolved colon, and 20 control colon specimens. Differential expression and leave-one-out cross-validation methods were used to define a unique gene signature of SSA/Ps. Our SSA/P gene signature was evaluated in colon cancer RNA-Seq data from The Cancer Genome Atlas (TCGA) to identify a subtype of colon cancers that may develop from SSA/Ps. A total of 1,422 differentially expressed genes were found in SSA/Ps relative to controls. Serrated polyposis syndrome (n = 12) and sporadic SSA/Ps (n = 9) exhibited almost complete (96%) gene overlap. A 51-gene panel in SSA/P showed similar expression in a subset of TCGA colon cancers with high microsatellite instability. A smaller 7-gene panel showed high sensitivity and specificity in identifying BRAF-mutant, CpG island methylator phenotype high, and MLH1-silenced colon cancers. We describe a unique gene signature in SSA/Ps that identifies a subset of colon cancers likely to develop through the serrated pathway. These gene panels may be utilized for improved differentiation of SSA/Ps from HPs and provide insights into novel molecular pathways altered in colon cancer arising from the serrated pathway. Cancer Prev Res; 9(6); 456-65. ©2016 AACR.

Effect of Sulindac and Erlotinib vs Placebo on Duodenal Neoplasia in Familial Adenomatous Polyposis: A Randomized Clinical Trial

IMPORTANCE

Patients with familial adenomatous polyposis (FAP) are at markedly increased risk for duodenal polyps and cancer. Surgical and endoscopic management of duodenal neoplasia is difficult and chemoprevention has not been successful.

OBJECTIVE

To evaluate the effect of a combination of sulindac and erlotinib on duodenal adenoma regression in patients with FAP.

DESIGN, SETTING, AND PARTICIPANTS

Double-blind, randomized, placebo-controlled trial, enrolling 92 participants with FAP, conducted from July 2010 through June 2014 at Huntsman Cancer Institute in Salt Lake City, Utah.

INTERVENTIONS

Participants with FAP were randomized to sulindac (150 mg) twice daily and erlotinib (75 mg) daily (n = 46) vs placebo (n = 46) for 6 months.

MAIN OUTCOMES AND MEASURES

The total number and diameter of polyps in the proximal duodenum were mapped at baseline and 6 months. The primary outcome was change in total polyp burden at 6 months. Polyp burden was calculated as the sum of the diameters of polyps. The secondary outcomes were change in total duodenal polyp count, change in duodenal polyp burden or count stratified by genotype and initial polyp burden, and percentage of change from baseline in duodenal polyp burden.

RESULTS

Ninety-two participants (mean age, 41 years [range, 24-55]; women, 56 [61%]) were randomized when the trial was stopped by the external data and safety monitoring board because the second preplanned interim analysis met the prespecified stopping rule for superiority. Grade 1 and 2 adverse events were more common in the sulindac-erlotinib group, with an acne-like rash observed in 87% of participants receiving treatment and 20% of participants receiving placebo (P < .001). Only 2 participants experienced grade 3 adverse events. [table: see text].

CONCLUSIONS AND RELEVANCE

Among participants with FAP, the use of sulindac and erlotinib compared with placebo resulted in a lower duodenal polyp burden after 6 months. Adverse events may limit the use of these medications at the doses used in this study. Further research is necessary to evaluate these preliminary findings in a larger study population with longer follow-up to determine whether the observed effects will result in improved clinical outcomes.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT 01187901.

Evidence for a heritable contribution to neuroendocrine tumors of the small intestine

Small intestinal neuroendocrine tumors (SI-NETs) are rare tumors arising from the enterochromaffin cells of the gut. Having a first-degree relative with a SI-NET has been shown to confer a substantial risk arising from shared environment and genetics. Heritable risk was examined using a computerized genealogy linked to historical statewide cancer data. A population-based analysis of the observed familial clustering of SI-NETs was performed to assess the genetic risk in distant relatives. A test for significant excess relatedness of 384 individuals with genealogy data and histologically confirmed SI-NETs was performed by comparing pairwise relatedness of cases to 1000 sets of matched controls. Overall significant excess pairwise relatedness was found for the 384 cases (P<0.001) and was still observed when closer than first cousin relationships were ignored (P=0.041). Relative risks (RRs) for SI-NETs were estimated as a ratio of observed to expected number of SI-NET cases among each relationship class. Siblings have a 13.4-fold (P<0.0001) and parents have a 6.5-fold (P=0.143) RR, suggesting both genetic and environmental influences. The risk extends out to third-degree relatives with a 2.3-fold RR (P=0.008). Metachronous cancers were also reported in 26% of the SI-NET cases demonstrating an increased RR of colon, bladder, non-Hodgkin lymphoma, melanoma, and prostate cancers. Although SI-NETs are rare, relatives of these cases are at a significantly elevated risk of developing a SI-NET due to heritable genetic factors. Definition of the genetic risk factors will be an important tool for earlier diagnosis and better outcomes for SI-NETs.

Confidentiality & the Risk of Genetic Discrimination: What Surgeons Need to Know

In the past decade, laws have been passed to provide legal protections against genetic discrimination. Many members of the public and medical providers are unaware of the legislation, and concerns about genetic privacy can prevent delivery of optimal medical care. Patient health information, including genetic testing and family history, is protected under the Health Insurance Portability and Accountability Act and the Genetic Information Nondiscrimination Act. Additional protections are granted through the Americans with Disabilities Act, state laws, and the Affordable Care Act. Communicating a genetic test result back to a patient is important for medical management decisions and family members.

APC promoter 1B deletion in seven American families with familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is a colorectal cancer predisposition syndrome caused by mutations in the adenomatous polyposis coli (APC) gene. Clinical genetic testing fails to identify disease causing mutations in up to 20% of clinically apparent FAP cases. Following the inclusion of multiplex ligation-dependent probe amplification (MLPA) probes specific for APC promoter 1B, seven probands were identified with a deletion of promoter 1B. Using haplotype analysis spanning the APC locus, the seven families appear to be identical by descent from a common founder. The clinical phenotype of 19 mutation carriers is classical FAP with colectomy at an average age of 24. The majority of cases had a large number of duodenal and gastric polyps. Measurements of allele-specific expression of APC mRNA using TaqMan assay confirmed that relative expression in the allele containing the promoter 1B deletion was reduced 42-98%, depending on tissue type. This study confirms the importance of APC promoter deletions as a cause of FAP and identifies a founder mutation in FAP patients from the United States.

RNA sequencing of sessile serrated colon polyps identifies differentially expressed genes and immunohistochemical markers

BACKGROUND

Sessile serrated adenomas/polyps (SSA/Ps) may account for 20-30% of colon cancers. Although large SSA/Ps are generally recognized phenotypically, small (<1 cm) or dysplastic SSA/Ps are difficult to differentiate from hyperplastic or small adenomatous polyps by endoscopy and histopathology. Our aim was to define the comprehensive gene expression phenotype of SSA/Ps to better define this cancer precursor.

RESULTS

RNA sequencing was performed on 5' capped RNA from seven SSA/Ps collected from patients with the serrated polyposis syndrome (SPS) versus eight controls. Highly expressed genes were analyzed by qPCR in additional SSA/Ps, adenomas and controls. The cellular localization and level of gene products were examined by immunohistochemistry in syndromic and sporadic SSA/Ps, adenomatous and hyperplastic polyps and controls. We identified 1,294 differentially expressed annotated genes, with 106 increased ≥10-fold, in SSA/Ps compared to controls. Comparing these genes with an array dataset for adenomatous polyps identified 30 protein coding genes uniquely expressed ≥10-fold in SSA/Ps. Biological pathways altered in SSA/Ps included mucosal integrity, cell adhesion, and cell development. Marked increased expression of MUC17, the cell junction protein genes VSIG1 and GJB5, and the antiapoptotic gene REG4 were found in SSA/Ps, relative to controls and adenomas, were verified by qPCR analysis of additional SSA/Ps (n = 21) and adenomas (n = 10). Immunohistochemical staining of syndromic (n≥11) and sporadic SSA/Ps (n≥17), adenomatous (n≥13) and hyperplastic (n≥10) polyps plus controls (n≥16) identified unique expression patterns for VSIG1 and MUC17 in SSA/Ps.

CONCLUSION

A subset of genes and pathways are uniquely increased in SSA/Ps, compared to adenomatous polyps, thus supporting the concept that cancer develops by different pathways in these phenotypically distinct polyps with markedly different gene expression profiles. Immunostaining for a subset of these genes differentiates both syndromic and sporadic SSA/Ps from adenomatous and hyperplastic polyps.

Shared genomic segment analysis: the power to find rare disease variants

Shared genomic segment (SGS) analysis uses dense single nucleotide polymorphism genotyping in high-risk (HR) pedigrees to identify regions of sharing between cases. Here, we illustrate the power of SGS to identify dominant rare risk variants. Using simulated pedigrees, we consider 12 disease models based on disease prevalence, minor allele frequency and penetrance to represent disease loci that explain 0.2-99.8% of total disease risk. Pedigrees were required to contain ≥ 15 meioses between all cases and to be HR based on significant excess of disease (P < 0.001 or P < 0.00001). Across these scenarios, the power for a single pedigree ranged widely. Nonetheless, fewer than 10 pedigrees were sufficient for excellent power in the majority of models. Power increased with the risk attributable to the disease locus, penetrance and the excess of disease in the pedigree. Sharing allowing for one sporadic case was uniformly more powerful than sharing using all cases. Furthermore, an SGS analysis using a large attenuated familial adenomatous polyposis pedigree identified a 1.96 Mb region containing the known causal APC gene with genome-wide significance. SGS is a powerful method for detecting rare variants and a valuable complement to genome-wide association studies and linkage analysis.

Activating mutation in MET oncogene in familial colorectal cancer

Background

In developed countries, the lifetime risk of developing colorectal cancer (CRC) is 5%, and it is the second leading cause of death from cancer. The presence of family history is a well established risk factor with 25-35% of CRCs attributable to inherited and/or familial factors. The highly penetrant inherited colon cancer syndromes account for approximately 5%, leaving greater than 20% without clear genetic definition. Familial colorectal cancer has been linked to chromosome 7q31 by multiple affected relative pair studies. The MET proto-oncogene which resides in this chromosomal region is considered a candidate for genetic susceptibility.

Methods

MET exons were amplified by PCR from germline DNA of 148 affected sibling pairs with colorectal cancer. Amplicons with altered sequence were detected with high-resolution melt-curve analysis using a LightScanner (Idaho Technologies). Samples demonstrating alternative melt curves were sequenced. A TaqMan assay for the specific c.2975C >T change was used to confirm this mutation in a cohort of 299 colorectal cancer cases and to look for allelic amplification in tumors.

Results

Here we report a germline non-synonymous change in the MET proto-oncogene at amino acid position T992I (also reported as MET p.T1010I) in 5.2% of a cohort of sibling pairs affected with CRC. This genetic variant was then confirmed in a second cohort of individuals diagnosed with CRC and having a first degree relative with CRC at prevalence of 4.1%. This mutation has been reported in cancer cells of multiple origins, including 2.5% of colon cancers, and in <1% in the general population. The threonine at amino acid position 992 lies in the tyrosine kinase domain of MET and a change to isoleucine at this position has been shown to promote metastatic behavior in cell-based models. The average age of CRC diagnosis in patients in this study is 63 years in mutation carriers, which is 8 years earlier than the general population average for CRC.

Conclusions

Although the MET p.T992I genetic mutation is commonly found in somatic colorectal cancer tissues, this is the first report also implicating this MET genetic mutation as a germline inherited risk factor for familial colorectal cancer. Future studies on the cancer risks associated with this mutation and the prevalence in different at-risk populations will be an important extension of this work to define the clinical significance.

Maximum-likelihood estimation of recent shared ancestry (ERSA)

Accurate estimation of recent shared ancestry is important for genetics, evolution, medicine, conservation biology, and forensics. Established methods estimate kinship accurately for first-degree through third-degree relatives. We demonstrate that chromosomal segments shared by two individuals due to identity by descent (IBD) provide much additional information about shared ancestry. We developed a maximum-likelihood method for the estimation of recent shared ancestry (ERSA) from the number and lengths of IBD segments derived from high-density SNP or whole-genome sequence data. We used ERSA to estimate relationships from SNP genotypes in 169 individuals from three large, well-defined human pedigrees. ERSA is accurate to within one degree of relationship for 97% of first-degree through fifth-degree relatives and 80% of sixth-degree and seventh-degree relatives. We demonstrate that ERSA's statistical power approaches the maximum theoretical limit imposed by the fact that distant relatives frequently share no DNA through a common ancestor. ERSA greatly expands the range of relationships that can be estimated from genetic data and is implemented in a freely available software package.

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.

Hereditary and familial colon cancer

Between 2% to 5% of all colon cancers arise in the setting of well-defined inherited syndromes, including Lynch syndrome, familial adenomatous polyposis, MUTYH-associated polyposis, and certain hamartomatous polyposis conditions. Each is associated with a high risk of colon cancer. In addition to the syndromes, up to one-third of colon cancers exhibit increased familial risk, likely related to inheritance. A number of less penetrant, but possibly more frequent susceptibility genes have been identified for this level of inheritance. Clarification of predisposing genes allows for accurate risk assessment and more precise screening approaches. This review examines the colon cancer syndromes, their genetics and management, and also the common familial colon cancers with current genetic advances and screening guidelines.

Common familial colorectal cancer linked to chromosome 7q31: a genome-wide analysis

Present investigations suggest that approximately 30% of colorectal cancer cases arise on the basis of inherited factors. We hypothesize that the majority of inherited factors are moderately penetrant genes, common in the population. We use an affected sibling pair approach to identify genetic regions that are coinherited by siblings with colorectal cancer. Individuals from families with at least two siblings diagnosed with colorectal adenocarcinoma or high-grade dysplasia were enrolled. Known familial colorectal cancer syndromes were excluded. A genome-wide scan on 151 DNA samples from 70 kindreds was completed using deCODE 1100 short tandem repeat marker set at an average 4-cM density. Fine mapping on a total of 184 DNAs from 83 kindreds was done in regions suggesting linkage. Linkage analysis was accomplished with Merlin analysis package. Nonparametric linkage analysis revealed three genetic regions with logarithm of the odds (LOD) scores >or=2.0: Ch. 3q29, LOD 2.61 (P = 0.0003); Ch. 4q31.3, LOD 2.13 (P = 0.0009); and Ch. 7q31.31, LOD 3.08 (P = 0.00008). Affected siblings with increased sharing at the 7q31 locus have a 3.8-year (+/- 3.5) earlier age of colorectal cancer onset although this is not statistically significant (P = 0.11). No significant linkage was found near genes causing known syndromes or regions previously reported (8q24, 9q22, and 11q23). The chromosome 3q21-q24 region reported to be linked in colorectal cancer relative pairs is supported by our study, albeit a minor peak (LOD 0.9; P = 0.02). No known familial cancer genes reside in the 7q31 locus, and thus the identified region may contain a novel susceptibility gene responsible for common familial colorectal cancer.

Colonic adenoma risk in familial colorectal cancer--a study of six extended kindreds

OBJECTIVES

Most colorectal cancers (CRCs) arise from adenomatous polyps, but the effects of CRC family history on adenoma risk are not well known. This issue is clinically relevant since several medical societies currently recommend earlier and more rigorous colorectal screening for individuals with a strong family history of CRC.

METHODS

Colonoscopies were performed in 236 first-, second-, and third-degree relatives of 40 index CRC cases from six large kindreds selected from a large population database. The kindreds were selected for significantly greater risk of CRCs compared with the overall population. Known hereditary colon cancer syndromes were clinically and genetically excluded.

RESULTS

Thirty-seven percent of relatives were found to have adenomas on colonoscopy. The average age of diagnosis for colon cancer was 63 yr and advanced adenomas 56 yr. Independent predictors of adenomatous polyps in the relatives were advancing age (P < 0.0001), male gender (P < 0.001), and greater degree of relation to CRC cases (P < 0.01). There was no significant predilection of colorectal tumors for the right or left colon. A higher degree of relationship to CRC cases was a significant predictor of having simple and advanced adenomas, but not hyperplastic polyps after adjustment for age and gender.

CONCLUSIONS

These data support the current recommendations for colonoscopy starting before the age of 50 yr in individuals with a strong family history of CRC.

Gonadal mosaicism and familial adenomatous polyposis

De novo mutations in the adenomatous polyposis coli (APC) gene are estimated to constitute approximately 25% of familial adenomatous polyposis (FAP) cases. A small percentage of these arise in the mosaic form, affecting only a subset of cells in the affected individual. A family is described here whereby an unaffected mother with no detectible mutation in APC, transmitted the identical APC c.4729G>T (p.Glu1577X) mutation to two children. A third child, with the same APC allelic haplotype received a normal APC allele, suggesting that the mutation originated in the gonadal tissues of the mother. These results underscore the utility of mutation-specific genetic testing for the parents and siblings of a proband of an adult-onset disease, even if the proband appears to have a de novo mutation. Parents who test negative for the mutation should be counseled about the possibility of having another affected child due to gonadal mosaicism.

Disease-associated casein kinase I delta mutation may promote adenomatous polyps formation via a Wnt/beta-catenin independent mechanism

The Wnt signaling pathway is critical for embryonic development and is dysregulated in multiple cancers. Two closely related isoforms of casein kinase I (CKIdelta and epsilon) are positive regulators of this pathway. We speculated that mutations in the autoinhibitory domain of CKIdelta/epsilon might upregulate CKIdelta/epsilon activity and hence Wnt signaling and increase the risk of adenomatous polyps and colon cancer. Exons encoding the CKIepsilon and CKIdelta regulatory domains were sequenced from DNA obtained from individuals with adenomatous polyps and a family history of colon cancer unaffected by familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer (HNPCC). A CKIdelta missense mutation, changing a highly conserved residue, Arg324, to His (R324H), was found in an individual with large and multiple polyps diagnosed at a relatively young age. Two findings indicate that this mutation is biologically active. First, ectopic ventral expression of CKIdelta(R324H) in Xenopus embryos results in secondary axis formation with an additional distinctive phenotype (altered morphological movements) similar to that seen with unregulated CKIepsilon. Second, CKIdelta(R324H) is more potent than wildtype CKIdelta in transformation of RKO colon cancer cells. Although the R324H mutation does not significantly change CKIdelta kinase activity in an in vitro kinase assay or Wnt/beta-catenin signal transduction as assessed by a beta-catenin reporter assay, it alters morphogenetic movements via a beta-catenin-independent mechanism in early Xenopus development. This novel human CKIdelta mutation may alter the physiological role and enhance the transforming ability of CKIdelta through a Wnt/beta-catenin independent mechanism and thereby influence colonic adenoma development.

Frequency of familial colon cancer and hereditary nonpolyposis colorectal cancer (Lynch syndrome) in a large population database

BACKGROUND AND AIMS

Estimates have been made concerning the fraction of colorectal cancer (CRC) cases that meet Amsterdam I criteria but not Amsterdam II criteria. The aim of this study was to determine in a population setting what fraction of CRC cases can be considered familial high-risk, what fraction of these meet Amsterdam I or II criteria, and what fraction of CRC cases overall meet Amsterdam I and II criteria.

METHODS

The Utah Population Data Base (UPDB), which links Utah genealogies to the Utah Cancer Registry, was used to examine the aims of the study. Familial high-risk was operationally defined as CRC occurring at an age <50 years or as a part of a first-degree relative pair. A subset of Amsterdam positive cancers was tested for microsatellite instability (MSI) to determine what fraction of Amsterdam families was likely to have hereditary nonpolyposis colorectal cancer (HNPCC).

RESULTS

Of the 6,628 CRC cases in the UPDB, 24.5% met the criteria for familial high-risk. Of these, 2.6% met Amsterdam I criteria and 5.5% Amsterdam II. Of total data base CRC cases, 0.8% met Amsterdam I criteria and 2.3% Amsterdam II. In a subset of colon tumors from Amsterdam families, 70% were MSI stable.

CONCLUSIONS

Although nearly 25% of CRC cases in our population data base met a simple definition of familial high-risk, only a small fraction of these and a smaller fraction of total CRC cases met Amsterdam I or II criteria. Less than half of a limited set of tumors from Amsterdam families were MSI positive.

Genetic testing for inherited colon cancer

The genes associated with each of the inherited syndromes of colon cancer have now been identified, and genetic testing is available for diagnosis. These syndromes include familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, Peutz-Jeghers syndrome, juvenile polyposis syndrome, and, possibly, Cowden's syndrome. Clinical genetic testing approaches have been developed for each of these syndromes and are now a part of accepted clinical care. Disease-causing mutations can be found in the majority of families affected with one of the inherited syndromes, and, most importantly, once a mutation is found in an index case of the family, relatives can be tested for the presence or absence of that mutation with near 100% accuracy. Cancer screening and management in syndrome families is then based on the results of genetic testing. For the physician to order and properly interpret genetic tests, a basic understanding of the types of mutations that lead to inherited disease and the methods for detecting them is vital. These issues will be presented. Additional clinical issues somewhat unique to genetic testing include genetic counseling and informed consent for genetic testing, both of which will also be reviewed. Often the most difficult aspect of genetic testing is deciding which patients and families should undergo the testing. Furthermore, this issue is quite specific for each of the syndromes. Thus, following presentation of general principles of selection for genetic testing, a detailed approach for identifying persons who should undergo testing for each of the individual syndromes will be given, together with relevant descriptions of the syndromes. Finally, the ongoing work to discover new and possibly more common but less penetrant colon cancer susceptibility genes that cause common familial colon cancer will be presented.

Genetic testing and phenotype in a large kindred with attenuated familial adenomatous polyposis

BACKGROUND & AIMS

An attenuated form of familial adenomatous polyposis has been described, but the phenotype remains poorly understood.

METHODS

We performed genetic testing on 810 individuals from 2 attenuated familial adenomatous polyposis kindreds harboring an identical germline adenomatous polyposis coli gene mutation. Colonoscopy was performed on mutation-positive persons.

RESULTS

The disease-causing mutation was present in 184 individuals. Adenomatous polyps were present in 111 of 120 gene carriers who had colonoscopy at an average age of 41 years. The median number of adenomas was 25 (range, 0-470), with striking variability of polyp numbers and a proximal colonic predominance of polyps. Colorectal cancer occurred in 27 mutation carriers (average age, 58 years; range, 29-81 years), with 75% in the proximal colon. The cumulative risk of colorectal cancer by age 80 was estimated to be 69%. An average of 3.4 recurrent polyps (range, 0-29) were found in the postcolectomy rectal remnant over a mean of 7.8 years (range, 1-34 years), with 1 rectal cancer.

CONCLUSIONS

This investigation shows that attenuated familial adenomatous polyposis in the kindreds examined shows a much smaller median number of polyps than typical familial adenomatous polyposis, a wide variability in polyp number even at older ages, and a more proximal colonic location of polyps and cancer, yet it is associated with an extremely high risk of colon cancer. The phenotype of attenuated familial adenomatous polyposis mimics typical familial adenomatous polyposis in some cases but in others is difficult to distinguish from sporadic adenomas and colorectal cancer, thus making genetic testing particularly important.

Intron 4 mutation in APC gene results in splice defect and attenuated FAP phenotype

The adenomatous polyposis coli (APC) protein is a tumor suppressor frequently involved in the development of inherited and sporadic colon cancers. Somatic mutations of the APC gene are found in 80% of all colon cancers. Inherited mutations result in familial adenomatous polyposis (FAP) as well as an attenuated form of this syndrome. FAP is characterized by the early age onset of hundreds to thousands of colonic adenomatous polyps and a virtual certainty of colon cancer unless the colon is removed. The attenuated form of FAP (AFAP) is characterized by fewer adenomas, later onset of adenomas and cancer, and a decreased lifetime cancer risk. We report a 37-year-old man with a history of more than 50 colonic adenomatous polyps, located predominately in the right colon. An insertion of a single thymidine between the second and third base pairs of intron 4 of the APC gene was identified (c.531+2_531+3insT). Monoallelic hybrid cells harboring a single copy of human chromosome 5 were generated from patient lymphoblasts. Sequencing of the APC cDNA product from these cells revealed a single RNA transcript with aberrant splicing in the mutant mRNA whereby exon 4 is deleted. The translational reading frame is shifted after codon 140 and a translational stop is generated predicting a truncated protein of 147 amino acids, thus indicating that the intronic mutation is disease causing. The lack of a secondary transcript from the mutant allele suggests that incomplete exon skipping is not the molecular mechanism behind the attenuated phenotype.

Biochemical variants of Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz (SLO or RSH) syndrome is characterized by multiple congenital anomalies, mental retardation, and defective growth; it results from an inherited defect in the biosynthesis of cholesterol. Patients have elevated plasma concentrations of 7-dehydrocholesterol, the immediate biosynthetic precursor of cholesterol and most also have low circulating levels of cholesterol. To understand better the biochemical basis of clinical variability, we evaluated cholesterol biosynthesis in lymphoblasts from 3 unrelated SLOS patients with distinct phenotypes. One patient has "type I SLOS", the second has the more severe "type II SLOS" and the third is classified as atypical and had been postulated to have a defect in sterol transport. The lymphoblasts of each patient show normal subcellular localization of cholesterol and 7-dehydrocholesterol by gradient fractionation. Biochemical differences in the ability of the lymphoblasts to convert 7-dehydrocholesterol to cholesterol are described and correspond to the severity of disease (type II > type I > atypical). Recently, the gene responsible for most SLOS cases (DHCR7) was mapped to chromosome 11 and mutations in DHCR7 were found in each of these patients. The biochemical differences described here likely result from the different mutations observed in DHCR7.