Survival of MUTYH-associated polyposis patients with colorectal cancer and matched control colorectal cancer patients

Updated European guidelines for clinical management of familial adenomatous polyposis (FAP), MUTYH-associated polyposis (MAP), gastric adenocarcinoma, proximal polyposis of the stomach (GAPPS) and other rare adenomatous polyposis syndromes: a joint EHTG-ESCP revision

BACKGROUND

Hereditary adenomatous polyposis syndromes, including familial adenomatous polyposis and other rare adenomatous polyposis syndromes, increase the lifetime risk of colorectal and other cancers.

METHODS

A team of 38 experts convened to update the 2008 European recommendations for the clinical management of patients with adenomatous polyposis syndromes. Additionally, other rare monogenic adenomatous polyposis syndromes were reviewed and added. Eighty-nine clinically relevant questions were answered after a systematic review of the existing literature with grading of the evidence according to Grading of Recommendations, Assessment, Development, and Evaluation methodology. Two levels of consensus were identified: consensus threshold (≥67% of voting guideline committee members voting either 'Strongly agree' or 'Agree' during the Delphi rounds) and high threshold (consensus ≥ 80%).

RESULTS

One hundred and forty statements reached a high level of consensus concerning the management of hereditary adenomatous polyposis syndromes.

CONCLUSION

These updated guidelines provide current, comprehensive, and evidence-based practical recommendations for the management of surveillance and treatment of familial adenomatous polyposis patients, encompassing additionally MUTYH-associated polyposis, gastric adenocarcinoma and proximal polyposis of the stomach and other recently identified polyposis syndromes based on pathogenic variants in other genes than APC or MUTYH. Due to the rarity of these diseases, patients should be managed at specialized centres.

Mutational Signatures in Gastric Cancer and Their Clinical Implications

Gastric cancer is characterised by high inter- and intratumour heterogeneity. The majority of patients are older than 65 years and the global burden of this disease is increasing due to the aging of the population. The disease is usually diagnosed at advanced stages, which is a consequence of nonspecific symptoms. Few improvements have been made at the level of noninvasive molecular diagnosis of sporadic gastric cancer, and therefore the mortality rate remains high. A new field of mutational signatures has emerged in the past decade with advances in the genome sequencing technology. These distinct mutational patterns in the genome, caused by exogenous and endogenous mutational processes, can be associated with tumour aetiology and disease progression, and could provide novel perception on the treatment possibilities. This review assesses the mutational signatures found in gastric cancer and summarises their potential for use in clinical setting as diagnostic or prognostic biomarkers. Associated treatment options and biomarkers already implemented in clinical use are discussed, together with those that are still being explored or are in clinical studies.

Whole genome, transcriptome and methylome profiling enhances actionable target discovery in high-risk pediatric cancer

The Zero Childhood Cancer Program is a precision medicine program to benefit children with poor-outcome, rare, relapsed or refractory cancer. Using tumor and germline whole genome sequencing (WGS) and RNA sequencing (RNAseq) across 252 tumors from high-risk pediatric patients with cancer, we identified 968 reportable molecular aberrations (39.9% in WGS and RNAseq, 35.1% in WGS only and 25.0% in RNAseq only). Of these patients, 93.7% had at least one germline or somatic aberration, 71.4% had therapeutic targets and 5.2% had a change in diagnosis. WGS identified pathogenic cancer-predisposing variants in 16.2% of patients. In 76 central nervous system tumors, methylome analysis confirmed diagnosis in 71.1% of patients and contributed to a change of diagnosis in two patients (2.6%). To date, 43 patients have received a recommended therapy, 38 of whom could be evaluated, with 31% showing objective evidence of clinical benefit. Comprehensive molecular profiling resolved the molecular basis of virtually all high-risk cancers, leading to clinical benefit in some patients.

American Society for Gastrointestinal Endoscopy guideline on the role of endoscopy in familial adenomatous polyposis syndromes

Familial adenomatous polyposis (FAP) syndrome is a complex entity, which includes FAP, attenuated FAP, and MUTYH-associated polyposis. These patients are at significant risk for colorectal cancer and carry additional risks for extracolonic malignancies. In this guideline, we reviewed the most recent literature to formulate recommendations on the role of endoscopy in this patient population. Relevant clinical questions were how to identify high-risk individuals warranting genetic testing, when to start screening examinations, what are appropriate surveillance intervals, how to identify endoscopically high-risk features, and what is the role of chemoprevention. A systematic literature search from 2005 to 2018 was performed, in addition to the inclusion of seminal historical studies. Most studies were from worldwide registries, which have compiled years of data regarding the natural history and cancer risks in this cohort. Given that most studies were retrospective, recommendations were based on epidemiologic data and expert opinion. Management of colorectal polyps in FAP has not changed much in recent years, as colectomy in FAP is the standard of care. What is new, however, is the developing body of literature on the role of endoscopy in managing upper GI and small-bowel polyposis, as patients are living longer and improved endoscopic technologies have emerged.

Comprehensive analysis of colorectal cancer-risk loci and survival outcome: A prognostic role for CDH1 variants

PURPOSE

Genome-wide association studies have identified common single nucleotide polymorphisms (SNPs) at 83 loci associated with colorectal cancer (CRC) risk in European populations. Because germline variation can also influence patient outcome, we studied the relationship between these SNPs and CRC survivorship.

EXPERIMENTAL DESIGN

For the 83 risk loci, 10 lead SNPs were directly genotyped, 72 were imputed and 1 was not genotyped nor imputed, in 1948 unrelated patients with advanced CRC from the clinical trials COIN and COIN-B (oxaliplatin and fluoropyrimidine chemotherapy ± cetuximab). A Cox survival model was used for each variant, and variants classified by pathway, adjusting for known prognostic factors. We imposed a Bonferroni threshold of P = 6.6 × 10-4 for multiple testing. We carried out meta-analyses of published risk SNPs associated with survival.

RESULTS

Univariate analysis identified six SNPs associated with overall survival (OS) (P < 0.05); however, only rs9939049 in CDH1 remained significant beyond the Bonferroni threshold (Hazard Ratio [HR] 1.44, 95% Confidence Intervals [CI]: 1.21-1.71, P = 5.0 × 10-5). Fine mapping showed that rs12597188 was the most significant SNP at this locus and remained significant after adjustment for known prognostic factors beyond multiple testing thresholds (HR 1.23, 95% CI: 1.13-1.34, P = 1.9 × 10-6). rs12597188 was also associated with poor response to therapy (OR 0.61, 95% CI: 0.42-0.87, P = 6.6 × 10-3). No combinations of SNPs within pathways were more significantly associated with survival compared with single variants alone, and no other risk SNPs were associated with survival in meta-analyses.

CONCLUSIONS

The CRC susceptibility SNP rs9939049 in CDH1 influences patient survival and warrants further evaluation as a prognostic biomarker.

Hereditary Cancer Syndromes-A Primer on Diagnosis and Management, Part 2: Gastrointestinal Cancer Syndromes

Hereditary causes due to mutations and defects in certain genes account for roughly 5% to 10% of all colorectal cancers. These inherited syndromes have been associated with a 60% to 100% lifetime risk for development of colorectal cancer, depending on the genetic syndrome, and many also carry an increased risk for multiple extracolonic malignancies. In this second part of a review series on hereditary cancer syndromes, the focus will be to provide guidance on the features and management of the most commonly encountered hereditary colorectal cancers and polyposis conditions including Lynch syndrome, familial adenomatous polyposis, MUTYH-associated polyposis, and hamartomatous polyposis.

Intussusception reveals MUTYH-associated polyposis syndrome and colorectal cancer: a case report

BACKGROUND

We are reporting a rare case of MUTYH-associated polyposis, a colorectal cancer hereditary syndrome, diagnosticated after an intussusception. Colorectal cancer is an important cause of cancer related mortality that can be manifested by an intussusception, a rare occurrence in adults and almost always related to tumors. Approximately 5% of colorectal cancers can be attributed to syndromes known to cause hereditary colorectal cancer, such as MUTYH-associated polyposis, autosomal genetic syndrome associated with this disease.

CASE PRESENTATION

We present the case of a 44 years old male, that sought medical consultation with a complaint of abdominal discomfort, that after five days changed its characteristics. The patient was sent to the emergency department were a CT-scan revealed intestinal sub-occlusion by ileocolic invagination. Right colectomy was carried out. The anatomic-pathological examination revealed a moderately differentiated mucinous adenocarcinoma and multiples sessile polyps, which led to the suspicion of a genetic syndrome. In the genetics analysis two mutations were observed in the MUTYH gene, and MUTYH-associated polyposis was diagnosticated.

CONCLUSION

This case demonstrates the importance of meticulous analysis of the patient examinations results to identify possible discrete alterations that can lead to improved understanding of disease.

NTHL1 and MUTYH polyposis syndromes: two sides of the same coin?

It is now well established that germline genomic aberrations can underlie high-penetrant familial polyposis and colorectal cancer syndromes, but a genetic cause has not yet been found for the major proportion of patients with polyposis. Since next-generation sequencing has become widely accessible, several novel, but rare, high-penetrant risk factors for adenomatous polyposis have been identified, all operating in pathways responsible for genomic maintenance and DNA repair. One of these is the base excision repair pathway. In addition to the well-established role of the DNA glycosylase gene MUTYH, biallelic mutations in which predispose to MUTYH-associated polyposis, a second DNA glycosylase gene, NTHL1, has recently been associated with adenomatous polyposis and a high colorectal cancer risk. Both recessive polyposis syndromes are associated with increased risks for several other cancer types as well, but the spectrum of benign and malignant tumours in individuals with biallelic NTHL1 mutations was shown to be broader; hence the name NTHL1-associated tumour syndrome. Colorectal tumours encountered in patients with these syndromes show unique, clearly distinct mutational signatures that may facilitate the identification of these syndromes. On the basis of the prevalence of pathogenic MUTYH and NTHL1 variants in the normal population, we estimate that the frequency of the novel NTHL1-associated tumour syndrome is five times lower than that of MUTYH-associated polyposis. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Genetic Investigation of Polymorphic OGG1 and MUTYH Genes Towards Increased Susceptibility in Lung Adenocarcinoma and its Impact on Overall Survival of Lung Cancer Patients Treated with Platinum Based Chemotherapy

Genes OGG1 and MUTYH are the two primary genes in Base excision repair pathway. OGG1 hydrolyzes the sugar phosphate backbone and remove the damaged base creating abasic site. MUTYH complements OGG1 as it particularly remove adenine mispaired with 8-oxo-G. Both OGG1 and MUTYH act as a check for the mis-incorporation of bases may be due to damages incurred on DNA. DNA isolation for 326 lung cancer cases and 330 controls was followed by genotyping making use of PCR-RFLP. Logistic regression was done to analyze the risk towards lung cancer. Patients were followed through telephonic conversation. Kaplan meier and Cox-regression were used for survival analysis. OGG1 presented a high risk towards lung cancer (CG: OR = 2.44, p = 0.0003; CG + GG: OR = 1.88, p = 0.0093). On the same lines adenocarcinoma for OGG1 were potent risk factors towards lung cancer (CG: OR = 4.72, p = 0.0002; CG + GG: OR = 3.63, p = 0.0018). Single allelic carriers for MUTYH gene imposed a high risk towards overall lung susceptibility and for all the three histology. Stratified analysis for chemotherapeutic drugs revealed administration of Cisplatin/Carboplatin + Pemtrexed for OGG1Ser ³²⁶ Cys showed a better survival (MST CG vs. CC: 9.1 vs. 0.56, p = <0.0001; HR =0.051, p = 0.0025). Whereas, MUTYH Gln³²⁴His showed a smaller survival for mutant genotype (CC) (MST CC vs. GG: 4.0 vs. 9.4, p = 0.05; HR = 1.75, p = 0.26). Single allelic carriers for both OGG1 and MUTYH were risk factors towards lung cancer. The risk was amplified on combining both OGG1 and MUTYH.

Hereditary Colorectal Polyposis and Cancer Syndromes: A Primer on Diagnosis and Management

Colorectal cancer (CRC) is the fourth most common cancer amongst men and women. Between 3 and 6% of all CRCs are attributed to well-defined inherited syndromes, including Lynch syndrome, familial adenomatous polyposis (FAP), MUTYH-associated polyposis (MAP), and several hamartomatous polyposis conditions. Identification of these patients through family history and appropriate genetic testing can provide estimates of cancer risk that inform appropriate cancer screening, surveillance and/or preventative interventions. This narrative review examines the hereditary colorectal cancer and polyposis syndromes, their genetic basis, clinical management, and evidence supporting cancer screening.

Repair of 8-oxoG:A mismatches by the MUTYH glycosylase: Mechanism, metals and medicine

Reactive oxygen and nitrogen species (RONS) may infringe on the passing of pristine genetic information by inducing DNA inter- and intra-strand crosslinks, protein-DNA crosslinks, and chemical alterations to the sugar or base moieties of DNA. 8-Oxo-7,8-dihydroguanine (8-oxoG) is one of the most prevalent DNA lesions formed by RONS and is repaired through the base excision repair (BER) pathway involving the DNA repair glycosylases OGG1 and MUTYH in eukaryotes. MUTYH removes adenine (A) from 8-oxoG:A mispairs, thus mitigating the potential of G:C to T:A transversion mutations from occurring in the genome. The paramount role of MUTYH in guarding the genome is well established in the etiology of a colorectal cancer predisposition syndrome involving variants of MUTYH, referred to as MUTYH-associated polyposis (MAP). In this review, we highlight recent advances in understanding how MUTYH structure and related function participate in the manifestation of human disease such as MAP. Here we focus on the importance of MUTYH's metal cofactor sites, including a recently discovered "Zinc linchpin" motif, as well as updates to the catalytic mechanism. Finally, we touch on the insight gleaned from studies with MAP-associated MUTYH variants and recent advances in understanding the multifaceted roles of MUTYH in the cell, both in the prevention of mutagenesis and tumorigenesis.

A Specific Mutational Signature Associated with DNA 8-Oxoguanine Persistence in MUTYH-defective Colorectal Cancer

8-Oxoguanine, a common mutagenic DNA lesion, generates G:C>T:A transversions via mispairing with adenine during DNA replication. When operating normally, the MUTYH DNA glycosylase prevents 8-oxoguanine-related mutagenesis by excising the incorporated adenine. Biallelic MUTYH mutations impair this enzymatic function and are associated with colorectal cancer (CRC) in MUTYH-Associated Polyposis (MAP) syndrome. Here, we perform whole-exome sequencing that reveals a modest mutator phenotype in MAP CRCs compared to sporadic CRC stem cell lines or bulk tumours. The excess G:C>T:A transversion mutations in MAP CRCs exhibits a novel mutational signature, termed Signature 36, with a strong sequence dependence. The MUTYH mutational signature reflecting persistent 8-oxoG:A mismatches occurs frequently in the APC, KRAS, PIK3CA, FAT4, TP53, FAT1, AMER1, KDM6A, SMAD4 and SMAD2 genes that are associated with CRC. The occurrence of Signature 36 in other types of human cancer indicates that DNA 8-oxoguanine-related mutations might contribute to the development of cancer in other organs.

Prevalence and Penetrance of Major Genes and Polygenes for Colorectal Cancer

Background: Although high-risk mutations in identified major susceptibility genes (DNA mismatch repair genes and MUTYH) account for some familial aggregation of colorectal cancer, their population prevalence and the causes of the remaining familial aggregation are not known.Methods: We studied the families of 5,744 colorectal cancer cases (probands) recruited from population cancer registries in the United States, Canada, and Australia and screened probands for mutations in mismatch repair genes and MUTYH We conducted modified segregation analyses using the cancer history of first-degree relatives, conditional on the proband's age at diagnosis. We estimated the prevalence of mutations in the identified genes, the prevalence of HR for unidentified major gene mutations, and the variance of the residual polygenic component.Results: We estimated that 1 in 279 of the population carry mutations in mismatch repair genes (MLH1 = 1 in 1,946, MSH2 = 1 in 2,841, MSH6 = 1 in 758, PMS2 = 1 in 714), 1 in 45 carry mutations in MUTYH, and 1 in 504 carry mutations associated with an average 31-fold increased risk of colorectal cancer in unidentified major genes. The estimated polygenic variance was reduced by 30% to 50% after allowing for unidentified major genes and decreased from 3.3 for age <40 years to 0.5 for age ≥70 years (equivalent to sibling relative risks of 5.1 to 1.3, respectively).Conclusions: Unidentified major genes might explain one third to one half of the missing heritability of colorectal cancer.Impact: Our findings could aid gene discovery and development of better colorectal cancer risk prediction models. Cancer Epidemiol Biomarkers Prev; 26(3); 404-12. ©2016 AACR.

Cutaneous Sebaceous Lesions in a Patient With MUTYH-Associated Polyposis Mimicking Muir-Torre Syndrome

A 76-year-old white male with a history of adenocarcinoma of the rectosigmoideum and multiple colonic polyps removed at the age of 38 and 39 years by an abdominoperitoneal amputation and total colectomy, respectively, presented with multiple whitish and yellowish papules on the face and a verrucous lesion on the trunk. The lesions were surgically removed during the next 3 years and a total of 13 lesions were investigated histologically. The diagnoses included 11 sebaceous adenomas, 1 low-grade sebaceous carcinoma, and 1 squamous cell carcinoma. In some sebaceous lesions, squamous metaplasia, intratumoral heterogeneity, mucinous changes, and peritumoral lymphocytes as sometimes seen in sebaceous lesions in Muir-Torre syndrome were noted. Mutation analysis of the peripheral blood revealed a germline mutation c.692G>A,p.(Arg231His) in exon 9 and c.1145G>A, p.(Gly382Asp) in exon 13 of the MUTYH gene. A KRAS mutation G12C (c.34G>T, p.Gly12Cys) was detected in 1 sebaceous adenoma and a NRAS mutation Q61K (c.181C>A, p.Gln61Lys) was found in 2 other sebaceous adenomas. No germline mutations in MLH1, MSH2, MSH6 and PMS2 genes, no microsatellite instability, no aberrant methylation of MLH1 promoter, and no somatic mutations in MSH2 and MSH6 were found. An identical MUTYH germline mutation was found in the patient's daughter. Despite striking clinicopathological similarities with Muir-Torre syndrome, the molecular biologic testing confirmed the final diagnosis of MUTYH-associated polyposis.

Next-Generation Sequencing Panels for the Diagnosis of Colorectal Cancer and Polyposis Syndromes: A Cost-Effectiveness Analysis

PURPOSE

To evaluate the cost effectiveness of next-generation sequencing (NGS) panels for the diagnosis of colorectal cancer and polyposis (CRCP) syndromes in patients referred to cancer genetics clinics.

PATIENTS AND METHODS

We developed a decision model to evaluate NGS panel testing compared with current standard of care in patients referred to a cancer genetics clinic. We obtained data on the prevalence of genetic variants from a large academic laboratory and calculated the costs and health benefits of identifying relatives with a pathogenic variant, in life-years and quality-adjusted life-years (QALYs). We classified the CRCP syndromes according to their type of inheritance and penetrance of colorectal cancer. One-way and probabilistic sensitivity analyses were conducted to assess uncertainty.

RESULTS

Evaluation with an NGS panel that included Lynch syndrome genes and other genes associated with highly penetrant CRCP syndromes led to an average increase of 0.151 year of life, 0.128 QALY, and $4,650 per patient, resulting in an incremental cost-effectiveness ratio of $36,500 per QALY compared with standard care and a 99% probability that this panel was cost effective at a threshold of $100,000 per QALY. When compared with this panel, the addition of genes with low colorectal cancer penetrance resulted in an incremental cost-effectiveness ratio of $77,300 per QALY.

CONCLUSION

The use of an NGS panel that includes genes associated with highly penetrant CRCP syndromes in addition to Lynch syndrome genes as a first-line test is likely to provide meaningful clinical benefits in a cost-effective manner at a $100,000 per QALY threshold.

ACG clinical guideline: Genetic testing and management of hereditary gastrointestinal cancer syndromes

This guideline presents recommendations for the management of patients with hereditary gastrointestinal cancer syndromes. The initial assessment is the collection of a family history of cancers and premalignant gastrointestinal conditions and should provide enough information to develop a preliminary determination of the risk of a familial predisposition to cancer. Age at diagnosis and lineage (maternal and/or paternal) should be documented for all diagnoses, especially in first- and second-degree relatives. When indicated, genetic testing for a germline mutation should be done on the most informative candidate(s) identified through the family history evaluation and/or tumor analysis to confirm a diagnosis and allow for predictive testing of at-risk relatives. Genetic testing should be conducted in the context of pre- and post-test genetic counseling to ensure the patient's informed decision making. Patients who meet clinical criteria for a syndrome as well as those with identified pathogenic germline mutations should receive appropriate surveillance measures in order to minimize their overall risk of developing syndrome-specific cancers. This guideline specifically discusses genetic testing and management of Lynch syndrome, familial adenomatous polyposis (FAP), attenuated familial adenomatous polyposis (AFAP), MUTYH-associated polyposis (MAP), Peutz-Jeghers syndrome, juvenile polyposis syndrome, Cowden syndrome, serrated (hyperplastic) polyposis syndrome, hereditary pancreatic cancer, and hereditary gastric cancer.

Common MUTYH mutations and colorectal cancer risk in multiethnic populations

MUTYH is associated with colorectal cancer (CRC) risk. We studied the frequency of MUTYH and risk of CRC in Arabs, North African and European Jews. Participants were all 593 Sephardi Moroccan Jews (232 cases, 361 controls) and all 631 Arabs (327 cases, 304 controls) recruited into a population-based study of colorectal cancer in Israel, as well as a random sample of 189 Ashkenazi Jewish cases. Two MUTYH mutations, G396D and Y179C, were studied in 1,413 individuals, with MUTYH sequence analysis in 46 cases with CRC in a sibling or adenoma. No carriers of mutations in MUTYH were identified in Ashkenazi Jews and only one in Arabs. In Sephardi Jews, 28 carriers of G396D, 25 (4.2%) heterozygotes and 3 (0.5%) homozygotes were identified. Four (0.7%) were heterozygote carriers of the Y179C mutation. Two compound heterozygous carriers of Y179C and G396D were identified. Homozygote carriers of G396D had nonsignificantly elevated risk of CRC (OR = 11.0, 95% CI: 0.91-213.9, p = 0.06), and combined bi-allelic carriers of G396D and Y179C had increased risk, OR = 17.4, 95% CI = (1.9-316.7, p = 0.009). Four of five bi-allelic carriers reported a family history of CRC. Sequencing of 46 colorectal cancer cases with family history and additional adenomas, did not identify any other non-founder mutations. MUTYH carriers of the two common founder mutations are profoundly under-represented among both Ashkenazi Jews and Arabs. The prevalence of MUTYH carriers of the common mutations is much higher in Sephardi Jews. Bi-allelic carriers of mutations in MUTYH, are associated with highly risk of colorectal cancer.

MUTYH-associated colorectal cancer and adenomatous polyposis

MUTYH-associated polyposis (MAP) was first described in 2002. MUTYH is a component of a base excision repair system that protects the genomic information from oxidative damage. When the MUTYH gene product is impaired by bi-allelic germline mutation, it leads to the mutation of cancer-related genes, such as the APC and/or the KRAS genes, via G to T transversion. MAP is a hereditary colorectal cancer syndrome inherited in an autosomal-recessive fashion. The clinical features of MAP include the presence of 10-100 adenomatous polyps in the colon, and early onset of colorectal cancer. Ethnic and geographical differences in the pattern of the MUTYH gene mutations have been suggested. In Caucasian patients, c.536A>G (Y179C) and c.1187G>A (G396D) mutations are frequently detected. In the Asian population, Y179C and G396D are uncommon, whereas other variants are suggested to be the major causes of MAP. We herein review the literature on MUTYH-associated colorectal cancer and adenomatous polyposis.

Familial colon cancer syndromes: an update of a rapidly evolving field

Colorectal cancer (CRC) is a major cause of morbidity and mortality in the world. Up to 30 % of CRCs have evidence of a familial component, and about 5 % are thought to be due to well-characterized inherited mutations. This review will focus on recent developments in the understanding of the individual hereditary CRC syndromes, including Lynch syndrome, familial CRC type X, familial adenomatous polyposis, MutYH-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis syndrome, PTEN hamartomatous syndrome, and serrated polyposis syndrome. Advances within the area of hereditary colon cancer syndromes paint a picture of a rapidly moving, rapidly maturing, and increasingly collaborative field with many opportunities for ongoing research and development.

[Hereditary colorectal cancer]

Up to 5% of all diagnosed colorectal cancers has a hereditary cuase. Colon cancer arise in younger individuals, and extracolonic tumors are also frequent. A precise understanding of main syndromes will allow the proper management of these patients, including genetic counselling, screening and prophylactic surgery.

Genetic polymorphisms in detoxification and DNA repair genes and susceptibility to glycidamide-induced DNA damage

Acrylamide (AA) is a probable human carcinogen formed in carbohydrate-rich foodstuffs upon heating. Glycidamide (GA), the AA metabolite formed by epoxidation, is considered the ultimate genotoxic agent. In this study, the in vitro genotoxic potential of AA and GA in human whole blood leukocytes was compared using the alkaline comet assay. Although AA did not induce significant DNA damage in the concentrations tested (up to 1000 μM), GA markedly increased the percentage of tail DNA at concentrations ≥250 μM. Further, this study addressed the role of genetic polymorphisms in key genes involved in metabolism and DNA repair pathways (BER, NER, HRR, and NHEJ) on GA-induced genotoxicity assessed by the alkaline comet assay. The results obtained suggested associations between DNA damage and polymorphisms of BER (MUTYH Gln335His and XRCC1 Gln399Arg) and NER (XPC Ala499Val) genes, either alone or in combination.

Reduced expression of MUTYH with suppressive activity against mutations caused by 8-hydroxyguanine is a novel predictor of a poor prognosis in human gastric cancer

The MUTYH gene encodes a DNA glycosylase that can initiate the excision repair of adenine mispaired with 8-hydroxyguanine (8OHG) and is responsible for a susceptibility to multiple colorectal adenomas and carcinomas. To determine whether the MUTYH gene is involved in gastric carcinogenesis, we first examined the expression level of MUTYH in gastric cancer. The reduced expression of MUTYH mRNA transcript was detected in both gastric cancer cell lines and primary gastric cancers using qRT-PCR analysis. Immunohistochemical analysis also showed a significant reduction in MUTYH protein expression in gastric cancer, compared with non-cancerous gastric epithelium (immunohistochemical score, 175.5 ± 43.0 versus 281.5 ± 24.8; p < 0.0001). Among the gastric cancers, the MUTYH expression level was significantly associated with the histopathology (p < 0.0001) and the pT stage (p < 0.001). The outcome of patients with gastric cancer exhibiting low MUTYH expression was significantly worse than the outcome of patients with gastric cancer exhibiting high MUTYH expression (p = 0.0007, log-rank test) and a multivariate analysis revealed that reduced MUTYH expression was an independent predictor of a poor survival outcome among the gastric cancer patients (hazard ratio, 1.865; 95% confidence interval, 1.028-3.529; p = 0.0401). We next compared the functional effects of MUTYH on gastric cancer cells, based on their MUTYH expression levels. MUTYH-over-expressing stable clones of the gastric cancer cell line AGS showed: (a) higher DNA cleavage activity towards adenine:8OHG mispair-containing substrates; (b) higher suppressive activity against mutations caused by 8OHG in a supF forward mutation assay; and (c) higher suppressive activity for cellular proliferation than empty vector-transfected AGS clones. These results suggested that MUTYH is a suppressor of mutations caused by 8OHG in gastric cells and that its reduced expression is associated with a poor prognosis in gastric cancer.