Multiple Colorectal Adenomas Research Articles

Germline and somatic polymerase ϵ and δ mutations define a new class of hypermutated colorectal and endometrial cancers

Polymerases ϵ and δ are the main enzymes that replicate eukaryotic DNA. Accurate replication occurs through Watson–Crick base pairing and also through the action of the polymerases' exonuclease (proofreading) domains. We have recently shown that germline exonuclease domain mutations (EDMs) of POLE and POLD1 confer a high risk of multiple colorectal adenomas and carcinoma (CRC). POLD1 mutations also predispose to endometrial cancer (EC). These mutations are associated with high penetrance and dominant inheritance, although the phenotype can be variable. We have named the condition polymerase proofreading-associated polyposis (PPAP). Somatic POLE EDMs have also been found in sporadic CRCs and ECs, although very few somatic POLD1 EDMs have been detected. Both the germline and the somatic DNA polymerase EDMs cause an ‘ultramutated’, apparently microsatellite-stable, type of cancer, sometimes leading to over a million base substitutions per tumour. Here, we present the evidence for POLE and POLD1 as important contributors to the pathogenesis of CRC and EC, and highlight some of the key questions in this emerging field. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd

Abstract 4832: High calcium reduces multiple or advanced colorectal adenoma risk by nearly 90% among those with variant alleles in two critical genes in calcium reabsorption.

Abstract Despite the rapidly increasing use of colonoscopy, colorectal cancer still remains the 2nd most common cause of cancer death in the United States. Most of these colorectal cancers arise from adenomas. High calcium consumption has been linked to reduced risks of colorectal adenoma and cancer. However, results from a large clinical trial conducted in the general population were not consistent from those conducted among colorectal adenoma patients. Adenoma patients have a lower intake of calcium than general population. Furthermore, previous studies indicate there is substantial inter-individual variation in the ability to (re)absorb calcium, which is mostly attributed to genetic variation. Thus, we hypothesized that some of the inconsistency in previous studies was due to interactions between calcium and genetic polymorphisms involved in calcium homeostasis. In an NIH R01 project, we conducted a two- phase study to evaluate whether polymorphisms in KCNJ1 and 13 other genes modified the associations between calcium intake and risk of colorectal adenoma. Included in the study were 1818 cases and 3992 controls identified from the Tennessee Colorectal Polyp Study (TCPS), a colonoscopy-based case control study conducted in Nashville, TN. We identified in Phase 1 and replicated in Phase 2 that two polymorphisms in two genes (i.e. one SNP in each gene) significantly modified the associations between calcium intake and colorectal adenoma risk. One gene is potassium inwardly-rectifying channel, subfamily J, member 1 (KCNJ1), which etiologically leads to hereditary familial diseases with impairments in reabsorption for calcium. The p for interaction with the SNP in the KCNJ1 gene remained statistically significant after Bonferroni correction for multiple comparisons (all SNPs in 14 genes). In the combined analysis of these two genes, we found 52% of the study population carry at least one variant allele in one of two genes while 13% of the population carry variant alleles in both genes. We found among those with zero variant alleles in two genes, the highest tertile of calcium intake was not associated with adenoma risk with an OR (95% CI) of 1.06(0.65-1.72). Highest calcium intake tertile was significantly associated with a 39% reduced adenoma risk among those who carry variant allele in one gene (p for trend, 0.046), and with a 69% reduced risk among those with alleles in both genes (p for trend, 0.039). The corresponding reduction in risk with advanced or multiple adenomas increased to 89% (95%CI: 41%-98%) among those with variant alleles in both genes (p for interaction, 5.5×10−5). In summary, high intake of calcium may only protect against colorectal carcinogenesis among those who carry variant alleles in two genes, particularly for those who carry variant alleles in both genes. Citation Format: Xiangzhu Zhu, Martha J. Shrubsole, Reid M. Ness, Qiuyin Cai, Jirong Long, Zhi Chen, Ji Liang, Guoliang Li, Walter E. Smalley, Todd L. Edwards, Edward Giovannucci, Wei Zheng, Qi Dai. High calcium reduces multiple or advanced colorectal adenoma risk by nearly 90% among those with variant alleles in two critical genes in calcium reabsorption. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4832. doi:10.1158/1538-7445.AM2013-4832

Abstract 182: Differential response of epithelial cells from colorectal adenomas and adjacent nonneoplastic colonic mucosa to aspirin and atorvastatin in Apc+/Min-FCCC mice.

Abstract Although various agents have been identified that are efficacious in inhibiting colorectal adenomas in humans, the precise mechanisms responsible for their antitumor activity remain ill-defined. Significant insight into the use of agents for the prevention and treatment of colorectal cancer can be gained by examining the biological response of nonneoplastic colonic mucosa and colorectal adenomas to drug exposure. The present study compared the gene expression profile of neoplastic and nonneoplastic colonic epithelial cells following short-term administration of aspirin and atorvastatin to a strain of mice that uniquely develop multiple colorectal adenomas (Apc+/Min-FCCC). Tumor-bearing male Apc+/Min-FCCC mice (70 days of age) received either control Teklad 2018SX diet or diet supplemented with aspirin (300 ppm) or atorvastatin (100 ppm) for 7 days. At euthanasia, the colon was examined for gross lesions and matched pairs of colorectal adenomas and adjacent normal mucosa were frozen in OCT for gene expression analyses. Colonic epithelial cells were laser microdissected from pairs of pathologically-confirmed colorectal adenomas and nonneoplastic mucosa (4/treatment group). Amplified RNA was subjected to gene expression profiling using Agilent Mouse Whole Genome 4 X 44K microarrays. Genes differentially expressed in colon tissue from untreated vs. drug-treated mice were identified using LIMMA methodology and filtered (p = 0.01). The number of unique genes differentially expressed in neoplastic epithelial cells exposed to aspirin was 1052, while a much smaller set of genes (N=74) was altered in the nonneoplastic epithelium. Functional enrichment analyses revealed that the pathways modulated in nonneoplastic cells (i.e. protein folding, posttranscriptional regulation, DNA damage response, vascular permeability) were distinct from those altered in adenomas (i.e. cell adhesion, DNA repair, TOR signaling, apoptosis, glucose transport). In contrast, fewer genes were differentially expressed in neoplastic cells (N = 286) than in the adjacent nonneoplastic colonic mucosa (N = 749) following exposure to atorvastatin. The majority of the cellular processes modified in nonneoplastic cells by atorvastatin (i.e. DNA damage, cell death, immune function, cilium assembly) differed from those affected in neoplastic cells (i.e. lipid metabolism, apoptosis, cell cycle control, DNA repair). These data suggest that the mechanisms responsible for the protection conferred to nonneoplastic cells by aspirin or atorvastatin vary from those that lead to inhibition of tumor growth. Further mining of these expression data when combined with endoscopic monitoring of individual lesions during drug exposure should significantly enhance our understanding of the cellular processes responsible for their activity. (Supported by NIH N01 CN43309) Citation Format: Lisa Vanderveer, Suresh Paramasivam, Kara Williams, Harry Cooper, Karthik Devarajan, Suraj Peri, Yan Zhou, Laura Henik, Wen-Chi Chang, Ronald Lubet, Margie Clapper. Differential response of epithelial cells from colorectal adenomas and adjacent nonneoplastic colonic mucosa to aspirin and atorvastatin in Apc+/Min-FCCC mice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 182. doi:10.1158/1538-7445.AM2013-182

Mutational spectrum of the APC and MUTYH genes and genotype–phenotype correlations in Brazilian FAP, AFAP, and MAP patients

BackgroundPatients with multiple colorectal adenomas are currently screened for germline mutations in two genes, APC and MUTYH. APC-mutated patients present classic or attenuated familial adenomatous polyposis (FAP/AFAP), while patients carrying biallelic MUTYH mutations exhibit MUTYH-associated polyposis (MAP). The spectrum of mutations as well as the genotype-phenotype correlations in polyposis syndromes present clinical impact and can be population specific, making important to obtain genetic and clinical data from different populations.MethodsDNA sequencing of the complete coding region of the APC and MUTYH genes was performed in 23 unrelated Brazilian polyposis patients. In addition, mutation-negative patients were screened for large genomic rearrangements by multiplex ligation-dependent probe amplification, array-comparative genomic hybridization, and duplex quantitative PCR. Biallelic MUTYH mutations were confirmed by allele-specific PCR. Clinical data of the index cases and their affected relatives were used to assess genotype–phenotype correlations.ResultsPathogenic mutations were identified in 20 of the 23 probands (87%): 14 in the APC gene and six in the MUTYH gene; six of them (30%) were described for the first time in this series. Genotype-phenotype correlations revealed divergent results compared with those described in other studies, particularly regarding the extent of polyposis and the occurrence of desmoid tumors in families with mutations before codon 1444 (6/8 families with desmoid).ConclusionsThis first comprehensive investigation of the APC and MUTYH mutation spectrum in Brazilian polyposis patients showed a high detection rate and identified novel pathogenic mutations. Notably, a significant number of APC-positive families were not consistent with the predicted genotype-phenotype correlations from other populations.

Polypose liée à MUTYH

Inherited defects of base excision repair have not been associated with any human genetic disorder, although mutations of the genes mutM and mutY, which function in Escherichia coli base excision repair, lead to increased transversions of G:C to T:A. We have studied family N, which is affected with multiple colorectal adenomas and carcinoma but lacks an inherited mutation of the adenomatous polyposis coli gene (APC) that is associated with familial adenomatous polyposis. Here we show that 11 tumors from 3 affected siblings contain 18 somatic inactivating mutations of APC and that 15 of these mutations are G:C—>A transversions—a significantly greater proportion than is found in sporadic tumors or in tumors associated with familial adenomatous polyposis. Analysis of the human homolog of mutY, MYH, showed that the siblings were compound heterozygotes for the nonconservative missense variants Tyr165Cys and Gly382Asp. These mutations affect residues that are conserved in mutY of E. coli (Tyr82 and Gly253). Tyrosine 82 is located in the pseudo-helix-hairpin-helix (HhH) motif and is predicted to function in mismatch specificity. Assays of adenine glycosylase activity of the Tyr82Cys and Gly253Asp mutant proteins with 8-oxoG:A and G:A substrates show that their activity is reduced significantly. Our findings link the inherited variants in MYH to the pattern of somatic APC mutation in family N and implicate defective base excision repair in predisposition to tumors in humans.

Prediabetes Is Associated with a High-Risk Colorectal Adenoma

Type 2 diabetes mellitus is associated with an increased risk of colorectal neoplasia. However, association between prediabetes and colorectal adenoma has not been reported. The aim of this study was to evaluate the relationship between prediabetes and the presence of colorectal adenomas. Consecutive prediabetic subjects who underwent screening colonoscopy were enrolled at Kyung Hee University Hospital in Gangdong, Seoul, Korea, between June 2006 and May 2012. Non-prediabetic subjects were separately pooled from the database of the Center for Health Promotion between January 2012 and May 2012. Prediabetes was defined according to the recommendations of the American Diabetes Association. The prevalence of colorectal adenomas and their characteristics were compared between prediabetic and non-prediabetic groups. The prevalence of colorectal adenoma was higher in prediabetic subjects than in non-prediabetic subjects (39.6 vs. 30.6 %, respectively, p = 0.019). Prediabetic subjects had more multiple and high-risk adenomas than the control group in non-matched analysis (p = 0.000, respectively). In age-matched analysis, the prevalence of multiple and high-risk adenomas were significantly higher in a prediabetic group than those in a control group (44.4 vs. 28.4 %, p = 0.034; 51.9 vs. 34.6 %, p = 0.026, respectively). Furthermore, prediabetes (odds ratio = 2.198; 95 % confidence interval = 1.042-4.637; p = 0.039) was found to be an independent risk factor for a high-risk adenoma by multivariate analysis. The prevalence of multiple and high-risk colorectal adenomas is significantly higher in the prediabetic subjects than those in the control group. Furthermore, prediabetes was found to be an independent risk factor for a high-risk colorectal adenoma.

Germline mutations affecting the proofreading domains of POLE and POLD1 predispose to colorectal adenomas and carcinomas.

Many individuals with multiple or large colorectal adenomas, or early-onset colorectal cancer (CRC), have no detectable germline mutations in the known cancer predisposition genes. Using whole-genome sequencing, supplemented by linkage and association analysis, we identified specific heterozygous POLE or POLD1 germline variants in several multiple adenoma and/or CRC cases, but in no controls. The susceptibility variants appear to have high penetrance. POLD1 is also associated with endometrial cancer predisposition. The mutations map to equivalent sites in the proof-reading (exonuclease) domain of DNA polymerases ε and δ, and are predicted to impair correction of mispaired bases inserted during DNA replication. In agreement with this prediction, mutation carriers’ tumours were microsatellite-stable, but tended to acquire base substitution mutations, as confirmed by yeast functional assays. Further analysis of published data showed that the recently-described group of hypermutant, microsatellite-stable CRCs is likely to be caused by somatic POLE exonuclease domain mutations.

Cancer-associated variants and a common polymorphism of MUTYH exhibit reduced repair of oxidative DNA damage using a GFP-based assay in mammalian cells.

Biallelic germline mutations in the base excision repair enzyme gene MUTYH lead to multiple colorectal adenomas and carcinomas referred to as MUTYH-associated polyposis. MUTYH removes adenine misincorporated opposite the DNA oxidation product, 8-oxoguanine (OG), thereby preventing accumulation of G:C to T:A transversion mutations. The most common cancer-associated MUTYH variant proteins when expressed in bacteria exhibit reduced OG:A mismatch affinity and adenine removal activity. However, direct evaluation of OG:A mismatch repair efficiency in mammalian cells has not been assessed due to the lack of an appropriate assay. To address this, we developed a novel fluorescence-based assay of OG:A repair and measured the repair capacity of MUTYH-associated polyposis variants expressed in Mutyh-/- mouse embryonic fibroblasts (MEFs). The repair of a single site-specific synthetic lesion in a green fluorescent protein reporter leads to green fluorescent protein expression with co-expression of a red fluorescent protein serving as the transfection control. Cell lines that stably express the MUTYH-associated polyposis variants G382D and Y165C have significantly lower OG:A repair versus wild-type MEFs and MEFs expressing human wild-type MUTYH. The MUTYH allele that encodes the Q324H variant is found at a frequency above 40% in samples from different ethnic groups and has long been considered phenotypically silent but has recently been associated with increased cancer risk in several clinical studies. In vitro analysis of Q324H MUTYH expressed in insect cells showed that it has reduced enzyme activity similar to that of the known cancer variant G382D. Moreover, we find that OG:A repair in MEFs expressing Q324H was significantly lower than wild-type controls, establishing that Q324H is functionally impaired and providing further evidence that this common variant may lead to increased cancer risk.

Prevalence and Phenotypes of APC and MUTYH Mutations in Patients With Multiple Colorectal Adenomas

Patients with multiple colorectal adenomas may carry germline mutations in the APC or MUTYH genes. To determine the prevalence of pathogenic APC and MUTYH mutations in patients with multiple colorectal adenomas who had undergone genetic testing and to compare the prevalence and clinical characteristics of APC and MUTYH mutation carriers. Cross-sectional study conducted among 8676 individuals who had undergone full gene sequencing and large rearrangement analysis of the APC gene and targeted sequence analysis for the 2 most common MUTYH mutations (Y179C and G396D) between 2004 and 2011. Individuals with either mutation underwent full MUTYH gene sequencing. APC and MUTYH mutation prevalence was evaluated by polyp burden; the clinical characteristics associated with a pathogenic mutation were evaluated using logistic regression analyses. Prevalence of pathogenic mutations in APC and MUTYH genes. Colorectal adenomas were reported in 7225 individuals; 1457 with classic polyposis (≥100 adenomas) and 3253 with attenuated polyposis (20-99 adenomas). The prevalence of pathogenic APC and biallelic MUTYH mutations was 95 of 119 (80% [95% CI, 71%-87%]) and 2 of 119 (2% [95% CI, 0.2%-6%]), respectively, among individuals with 1000 or more adenomas, 756 of 1338 (56% [95% CI, 54%-59%]) and 94 of 1338 (7% [95% CI, 6%-8%]) among those with 100 to 999 adenomas, 326 of 3253 (10% [95% CI, 9%-11%]) and 233 of 3253 (7% [95% CI, 6%-8%]) among those with 20 to 99 adenomas, and 50 of 970 (5% [95% CI, 4%-7%]) and 37 of 970 (4% [95% CI, 3%-5%]) among those with 10 to 19 adenomas. Adenoma count was strongly associated with a pathogenic mutation in multivariable analyses. Among patients with multiple colorectal adenomas, pathogenic APC and MUTYH mutation prevalence varied considerably by adenoma count, including within those with a classic polyposis phenotype. APC mutations predominated in patients with classic polyposis, whereas prevalence of APC and MUTYH mutations was similar in attenuated polyposis. These findings require external validation.

Factors affecting the treatment of multiple colorectal adenomas

Currently, no guidelines exist for the treatment of patients with multiple colorectal adenomas (MCRAs) (>10 but <100 synchronous nondiminutive polyps of the large bowel). This retrospective study aimed to investigate the clinical and molecular factors related to different treatments for MCRAs. Patients with MCRAs were consecutively enrolled from January 2003 to June 2011. Sequencing of their APC and MutYH genes was performed. The clinical, molecular, and family histories of the patients were collected using the Progeny database. The patient treatments were divided into three groups of increasing clinical weight: endoscopic polypectomy, segmental resection, and total colectomy. A logistic regression analysis of clinicomolecular factors related to different treatment options was performed. The study comprised 80 patients (32 women, 40%) with a median age of 53 years (range 13-74 years). The median number of polyps was 33 (range 10-90).The cases included 62 diffuse polyposis, 18 segmental polyposis coli and synchronous colorectal carcinomas (CRC; 34 cases, 43%). The pathogenetic mutations were biallelic MutYH (n = 19, 24%) and APC (n = 4, 5%). The mean follow-up period was 74 months (median 43 months, range 1-468 months). Endoscopic polypectomy was performed in 25 cases (31%), segmental resection in 16 cases (20%), and total colectomy in 39 cases (49%). The logistics regression analysis, considering all the patients, showed that the number of polyps, the presence of CRC, and mutation were correlated with more intensive treatment. For the patients without CRC, only the number of polyps was correlated with the severity of the treatment (p > 0.0166). "On the ROC (receiver operating characteristic) curve, 25 was the number of polyps that best discriminated between surgical and endoscopic therapy. The majority of patients with MCRAs undergo surgery. For patients without CRC, only the number of polyps, and not the presence of a disease-causing mutation, is correlated with increased heaviness of treatment. Patients with more than 25 polyps are more likely to undergo a surgical resection.

High prevalence of the c.1227_1228dup (p.Glu410GlyfsX43) mutation in Tunisian families affected with MUTYH-associated-polyposis

Germline mutations in the base excision repair gene MUTYH have been associated with recessive inheritance of multiple colorectal adenomas. Screening of the MUTYH gene was carried on index cases of 10 unrelated Tunisian families and on available DNA samples from some members. Three germline mutations: c.536A>G (p.Y179C), c.1187 G>A (p.G396D) and c.1227_1228dup (p.Glu410GlyfsX43), were identified in the homozygous or compound heterozygous state in 8 out of 10 families. The c.1227_1228dup (p.Glu410GlyfsX43) mutation was the most frequent, since it was found in biallelic homozygous in 7 probands and 2 members of family F1 and in compound heterozygous associated with the c.536 A>G (p.Y179C) or c.1187 G>A (p.G396D) in family F2. Haplotype analysis revealed that the 8 families are unrelated. Moreover, in sporadic colorectal cancer, the c.1227_1228dup (p.Glu410GlyfsX43) mutation was identified in 13% of patients compared to the p.G396D and p.Y179C found in 1.2 and 2.12% respectively. Our data shows the high prevalence of the p.Glu410GlyfsX43 mutation in Tunisian families affected with MUTYH associated polyposis as well as in sporadic colorectal carcinoma.

Alterations of the base excision repair gene MUTYH in sporadic colorectal cancer

The base excision repair gene MUTYH encodes glycosylase which removes adenine residues mispaired with 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OHG). Biallelic germline mutations of the MUTYH gene are known to cause multiple colorectal adenomas including polyposis and cancer, mostly due to G:C➝T:A transversions in proto-oncogenes or tumor suppressor genes. The risk of colorectal cancer (CRC) in monoallelic mutation carriers of MUTYH is estimated to be higher in comparison with non-carriers. To investigate the possible role in sporadic CRC, we examined alterations of the MUTYH gene including somatic mutations and allelic loss in 101 cases of sporadic CRC, together with the KRAS mutation in some cases. MUTYH mutations in cancer DNA were detected in 3 cases, while mutations were also found in DNA samples from normal tissues, indicating that all were germline mutations. Allelic loss at the MUTYH locus was found in 10 of 51 (20.0%) CRC cases and KRAS mutations were found in 33 of the 101 (32.7%) samples. There was no significant difference in the rate of G:C➝T:A transversion in KRAS between cases with allelic loss (1 of 10, 10.0%) and without allelic loss (9 of 41, 22.0%). Investigation of quantitative allelic imbalance at SNP rs3219489 of MUTYH showed that CRC cases with C allele dominance (minor type corresponding to His) were more frequently detected with G:C➝T:A transversions than in those with G allele dominance (major type corresponding to Gln). In conclusion, somatic alterations of MUTYH in sporadic CRC were rare, similar to other DNA repair genes. However, it is possible that unknown mutations of regions not analyzed in this study and epigenetic changes of the promoter region of MUTYH may contribute to the disease.

Role of Base Excision Repair Enzyme MUTYH in the Repair of 8-Hydroxyguanine and MUTYH-Associated Polyposis (MAP)

Abstract 8-Hydroxyguanine (8OHG) is an oxidized form of guanine, and the formation of 8OHG in DNA causes a G:C to T:A transversion mutation, since 8OHG can pair with adenine as well as cytosine. The base excision repair gene MUTYH encodes a DNA glycosylase for adenine mispaired with 8OHG and is thus involved in the prevention of mutations caused by 8OHG. Biallelic mutations of the MUTYH gene are responsible for MUTYH-associated polyposis (MAP), which is a hereditary disease and is characterized by a predisposition to multiple colorectal adenomas and carcinomas. This article reviews the repair function of MUTYH towards 8OHG, the functional characterization of MUTYH variants, the characteristics of MAP tumors, and the management of MAP patients.

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.

Detection of Colorectal Adenomas Using a Bioactivatable Probe Specific for Matrix Metalloproteinase Activity

A significant proportion of colorectal adenomas, in particular those that lack an elevated growth component, continue to escape detection during endoscopic surveillance. Elevation of the activity of matrix metalloproteinases (MMPs), a large family of zinc endopeptidases, in adenomas serves as a biomarker of early tumorigenesis. The goal of this study was to assess the feasibility of using a newly developed near-infrared bioactivatable probe (MMPSense 680) that reports the activity of a broad array of MMP isoforms to detect early colorectal adenomas. Adenomatous polyposis coli (Apc)+/Min-FCCC mice that spontaneously develop multiple colorectal adenomas were injected with MMPSense 680, and the colons were imaged in an IVIS Spectrum system ex vivo. Image analyses were correlated with histopathologic findings for all regions of interest (ROIs). The biochemical basis of fluorescent signal was investigated by immunohistochemical staining of MMP-7 and -9. A strong correlation (Kendall = 0.80) was observed between a positive signal and the presence of pathologically confirmed colonic adenomas; 92.9% of the 350 ROIs evaluated were classified correctly. The correlation between two independent observers was 0.87. MMP-7 expression was localized to epithelial cells of adenomas and microadenomas, whereas staining of MMP-9 was found in infiltrating polymorphonuclear leukocytes within the adenomas. MMPSense 680 identifies colorectal adenomas, both polypoid and nonpolypoid, in Apc+/Min-FCCC mice with high specificity. Use of this fluorescent probe in combination with colonoscopy could aid in preventing colorectal neoplasias by providing new opportunities for early detection and therapeutic intervention.

Associations of Cigarette Smoking and Alcohol Consumption With Advanced or Multiple Colorectal Adenoma Risks: A Colonoscopy-based Case-Control Study in Korea

The associations between alcohol consumption and cigarette smoking habits and the risk for colorectal adenomatous polyps according to the detailed clinical information about polyps were assessed in a large colonoscopy-based study. The study enrolled participants who visited the National Cancer Center of the Republic of Korea for cancer screening between April 2007 and April 2009. In 1,242 newly diagnosed colorectal adenoma patients and 3,019 polyp-free controls, past smokers (odds ratio (OR) = 1.31, 95% confidence interval (CI): 1.04, 1.65) and current smokers (OR = 1.70, 95% CI: 1.37, 2.11) had increased risks for adenomas compared with nonsmokers. Cigarette smoking conferred an even higher risk for advanced adenomas and 3 or more adenomas than for low-risk adenomas or a single adenoma. Dose-response relations were observed among the daily number of cigarettes smoked, the duration of smoking, the pack-years of smoking, and the risk for adenomas. A longer duration of alcohol consumption was associated with a higher risk for advanced adenomas (for >28 years of consumption: OR = 2.0, 95% CI: 1.10, 3.64) and 3 or more adenomas (OR = 2.19, 95% CI: 1.27, 3.76). In conclusion, cigarette smoking and alcohol consumption play roles in colorectal carcinogenesis, and the association differs by the clinical features of the adenomas.

Sa1587 Is the Prevalence of Colorectal Adenoma Higher in Patients With Gastric Neoplasm?

Colorectal cancer is more frequently detected among primary gastric cancer patients. We aimed to compare the prevalence of colorectal adenomas between patients with gastric neoplasm and healthy controls. This study was retrospectively performed in Chung-Ang University Hospital from January 2005 through June 2010. A total of 172 patients with gastric neoplasm who underwent colonoscopy were enrolled. Age and sex matched 860 subjects without gastric neoplasm who underwent colonoscopy in health promotion center were enrolled as the controls. Various factors were evaluated such as gender, age, body mass index (BMI), abdominal circumference, and the frequency of multiple (≥2 sites), large (≥1cm) and proximal (cecum to splenic flexure) colorectal adenomas. Advanced colorectal adenoma was defined by any of the followings; (1) polyp size at least 1.0 cm, (2) containing ≥25% villous features, or high-grade dysplasia, or adenocarcinoma by histologic examination. The sex ratio was 132:40 (male: female) in the gastric neoplasm group and 662:198 in the controls. The mean age was 59.6±9.9 in the gastric neoplasm group and 57.9±10.0 in the controls. BMI and abdominal circumference were greater in the controls than in the gastric neoplasm group (23.1±2.9 vs. 24.2±2.8 and 79.7±2.9 vs. 83.7±2.8, respectively). Among 172 patients with gastric neoplasm, low grade dysplasia, high grade dysplasia, and adenomcarinoma were 54, 5, and 113 patients, respectively. The prevalence of colorectal adenoma and multiple adenomas were tended to be higher in the gastric neoplasm group than in the controls (36.9% vs. 29.9%, and 17.7% vs.12.2%, respectively, p>0.05). The prevalence of advanced, large, and proximal colon adenoma were significantly higher in the gastric neoplasm group than in the controls (11.5% vs. 3.0%, 10.8% vs. 4.5%, and 26.2% vs. 16.7%, respectively, p<0.05). These results were similar with those in the subgroup analyses among subjects without general and abdominal obesity. In the regression analyses, the odds ratios of advanced, large and proximal colon adenomas were 4.5 (95% CI 2.5-8.2), 2.3 (95% CI 1.3-3.9), and 1.6 (95% CI 1.1-2.3), respectively, in the patients with gastric neoplasm compared to the controls. The prevalence of advanced colorectal adenoma and proximal colon adenoma were significantly higher in patients with gastric neoplasm than in healthy subjects. The patients with gastric adenoma or adenocarcinoma might need more vigorous screening for colorectal adenoma.

A new phenotypic manifestation of familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominant disease with hundreds of colorectal adenomas in teenagers and progression to colorectal cancer if colectomy is not performed. We investigated the association of two phenotypic manifestations-oral mucosal vascular density (OMVD) and oral mucosal reflectance (OMR)--with FAP and patients with multiple colorectal adenomas. Thirty-three patients with FAP from 29 unrelated pedigrees with APC gene mutation, 5 with multiple adenomas and no known gene mutations, and 50 population controls were evaluated for the two different manifestations utilizing a photographic/spectrophotometric system capturing images and reflectance at various wavelengths. Statistical analysis was performed with student t test and test performance characteristics were calculated. There were no significant differences in demographic variables between the FAP and control group. A significant difference in OMVD between FAP patients and controls was noted, P < 0.001. The sensitivity and specificity of oral mucosal vascular density for FAP was 91 and 90%, respectively. No association between this phenotypic manifestation and age or gender was found. All 5 patient with multiple polyps were positive for OMVD and the value was significantly higher than controls, P = 0.002. No significant difference was noted in OMR between the two patient groups and controls. OMVD is a new phenotypic manifestation in patients with FAP and also may identify those with multiple adenomas without known gene mutation.

Paediatric intestinal cancer and polyposis due to bi-allelic PMS2 mutations: Case series, review and follow-up guidelines

Background Bi-allelic germline mutations of one of the DNA mismatch repair genes, so far predominantly found in PMS2, cause constitutional MMR-deficiency syndrome. This rare disorder is characterised by paediatric intestinal cancer and other malignancies. We report the clinical, immunohistochemical and genetic characterisation of four families with bi-allelic germline PMS2 mutations. We present an overview of the published gastrointestinal manifestations of CMMR-D syndrome and propose recommendations for gastro-intestinal screening. Methods and Results The first proband developed a cerebral angiosarcoma at age 2 and two colorectal adenomas at age 7. Genetic testing identified a complete PMS2 gene deletion and a frameshift c.736_741delinsTGTGTGTGAAG (p.Pro246CysfsX3) mutation. In the second family, both the proband and her brother had multiple intestinal adenomas, initially wrongly diagnosed as familial adenomatous polyposis. A splice site c.2174+1G>A, and a missense c.137G>T (p.Ser46Ile) mutation in PMS2 were identified. The third patient was diagnosed with multiple colorectal adenomas at age 11; he developed a high-grade dysplastic colorectal adenocarcinoma at age 21. Two intragenic PMS2 deletions were found. The fourth proband developed a cerebral anaplastic ganglioma at age 9 and a high-grade colerectal dysplastic adenoma at age 10 and carries a homozygous c.2174+1G>A mutation. Tumours of all patients showed microsatellite instability and/or loss of PMS2 expression. Conclusions Our findings show the association between bi-allelic germline PMS2 mutations and severe childhood-onset gastrointestinal manifestations, and support the notion that patients with early-onset gastrointestinal adenomas and cancer should be investigated for CMMR-D syndrome. We recommend yearly follow-up with colonoscopy from age 6 and simultaneous video-capsule small bowel enteroscopy from age 8.

DNA glycosylase encoded by MUTYH functions as a molecular switch for programmed cell death under oxidative stress to suppress tumorigenesis

8-oxoguanine is a major base lesion in DNA or in nucleotides caused by oxidative stress, and is highly mutagenic because it can pair with adenine as well as cytosine. Adenine DNA glycosylase, encoded by the human mutY homolog gene, MUTYH, excises adenine in the nascent strand when inserted opposite 8-oxoguanine in template DNA, and thus suppresses mutagenesis caused by 8-oxoguanine that has accumulated in DNA due to oxidative stress. Several germ-line mutations in MUTYH are predisposed to MUTYH-associated polyposis, an autosomal recessive disorder characterized by multiple colorectal adenomas and carcinomas. Loss of function of MUTYH leads to an accumulation of somatic mutations in APC and KRAS genes, resulting in the development of adenomas/carcinomas. We recently demonstrated that accumulation of 8-oxoguanine in nuclear and mitochondrial DNA triggers two distinct cell death pathways that are independent of each other. Both pathways are initiated by the accumulation of MUTYH-generated single-strand breaks (SSBs) in nuclear or mitochondrial DNA. Our findings indicate that MUTYH-induced cell death due to oxidative stress results in an efficient elimination of mutagenic cells that have accumulated high levels of 8-oxoguanine in their DNAs. It is most likely that loss of function of MUTYH in stem or progenitor cells in the intestinal epithelium of MUTYH-associated polyposis patients results in escape from programmed cell death; however, accumulated 8-oxoguanine causes various mutations in APC or KRAS genes in these proliferative cells, thereby promoting tumorigenesis. We thus propose that MUTYH suppresses tumorigenesis under conditions of oxidative stress by inducing cell death and by suppressing mutagenesis.