Teresa Ocaña

Aberrant gene promoter methylation associated with sporadic multiple colorectal cancer.

Background Colorectal cancer (CRC) multiplicity has been mainly related to polyposis and non-polyposis hereditary syndromes. In sporadic CRC, aberrant gene promoter methylation has been shown to play a key role in carcinogenesis, although little is known about its involvement in multiplicity. To assess the effect of methylation in tumor multiplicity in sporadic CRC, hypermethylation of key tumor suppressor genes was evaluated in patients with both multiple and solitary tumors, as a proof-of-concept of an underlying epigenetic defect. Methodology/Principal Findings We examined a total of 47 synchronous/metachronous primary CRC from 41 patients, and 41 gender, age (5-year intervals) and tumor location-paired patients with solitary tumors. Exclusion criteria were polyposis syndromes, Lynch syndrome and inflammatory bowel disease. DNA methylation at the promoter region of the MGMT, CDKN2A, SFRP1, TMEFF2, HS3ST2 (3OST2), RASSF1A and GATA4 genes was evaluated by quantitative methylation specific PCR in both tumor and corresponding normal appearing colorectal mucosa samples. Overall, patients with multiple lesions exhibited a higher degree of methylation in tumor samples than those with solitary tumors regarding all evaluated genes. After adjusting for age and gender, binomial logistic regression analysis identified methylation of MGMT2 (OR, 1.48; 95% CI, 1.10 to 1.97; p = 0.008) and RASSF1A (OR, 2.04; 95% CI, 1.01 to 4.13; p = 0.047) as variables independently associated with tumor multiplicity, being the risk related to methylation of any of these two genes 4.57 (95% CI, 1.53 to 13.61; p = 0.006). Moreover, in six patients in whom both tumors were available, we found a correlation in the methylation levels of MGMT2 (r = 0.64, p = 0.17), SFRP1 (r = 0.83, 0.06), HPP1 (r = 0.64, p = 0.17), 3OST2 (r = 0.83, p = 0.06) and GATA4 (r = 0.6, p = 0.24). Methylation in normal appearing colorectal mucosa from patients with multiple and solitary CRC showed no relevant difference in any evaluated gene. Conclusions These results provide a proof-of-concept that gene promoter methylation is associated with tumor multiplicity. This underlying epigenetic defect may have noteworthy implications in the prevention of patients with sporadic CRC.

MSH6 and MUTYH Deficiency Is a Frequent Event in Early-Onset Colorectal Cancer

Purpose: Early-onset colorectal cancer (CRC) is suggestive of a hereditary predisposition. Lynch syndrome is the most frequent CRC hereditary cause. The MUTYH gene has also been related to hereditary CRC. A systematic characterization of these two diseases has not been reported previously in this population. Experimental Design: We studied a retrospectively collected series of 140 patients ≤50 years old diagnosed with nonpolyposis CRC. Demographic, clinical, and familial features were obtained. Mismatch repair (MMR) deficiency was determined by microsatellite instability (MSI) analysis, and immunostaining for MLH1, MSH2, MSH6, and PMS2 proteins. Germline MMR mutations were evaluated in all MMR-deficient cases. Tumor samples with loss of MLH1 or MSH2 protein expression were analyzed for somatic methylation. Germline MUTYH mutations were evaluated in all cases. BRAF V600E and KRAS somatic mutational status was also determined. Results: Fifteen tumors (11.4%) were MSI, and 20 (14.3%) showed loss of protein expression (7 for MLH1/PMS2, 2 for isolated MLH1, 3 for MSH2/MSH6, 7 for isolated MSH6, and 1 for MSH6/PMS2). We identified 11 (7.8%) germline MMR mutations, 4 in MLH1, 1 in MSH2, and 6 in MSH6. Methylation analysis revealed one case with somatic MLH1 methylation. Biallelic MUTYH mutations were detected in four (2.8%) cases. KRAS and BRAF V600E mutations were present in 39 (27.9%) and 5 (3.6%) cases, respectively. Conclusions: Loss of MSH6 expression is the predominant cause of MMR deficiency in early-onset CRC. Our findings prompt the inclusion of MSH6 and MUTYH screening as part of the genetic counseling of these patients and their relatives. Clin Cancer Res; 16(22); 5402–13. ©2010 AACR.

Whole-exome sequencing identifies rare pathogenic variants in new predisposition genes for familial colorectal cancer.

Purpose:Colorectal cancer is an important cause of mortality in the developed world. Hereditary forms are due to germ-line mutations in APC, MUTYH, and the mismatch repair genes, but many cases present familial aggregation but an unknown inherited cause. The hypothesis of rare high-penetrance mutations in new genes is a likely explanation for the underlying predisposition in some of these familial cases.Methods:Exome sequencing was performed in 43 patients with colorectal cancer from 29 families with strong disease aggregation without mutations in known hereditary colorectal cancer genes. Data analysis selected only very rare variants (0–0.1%), producing a putative loss of function and located in genes with a role compatible with cancer. Variants in genes previously involved in hereditary colorectal cancer or nearby previous colorectal cancer genome-wide association study hits were also chosen.Results:Twenty-eight final candidate variants were selected and validated by Sanger sequencing. Correct family segregation and somatic studies were used to categorize the most interesting variants in CDKN1B, XRCC4, EPHX1, NFKBIZ, SMARCA4, and BARD1.Conclusion:We identified new potential colorectal cancer predisposition variants in genes that have a role in cancer predisposition and are involved in DNA repair and the cell cycle, which supports their putative involvement in germ-line predisposition to this neoplasm.Genet Med 17 2, 131–142.

Prevalence of somatic mutl homolog 1 promoter hypermethylation in Lynch syndrome colorectal cancer.

Colorectal cancers (CRCs) that have microsatellite instability (MSI) and mutL homolog 1 (MLH1) immunoloss are observed in 3 clinical scenarios: Lynch syndrome (LS), sporadic MSI CRC, and Lynch‐like syndrome (LLS). v‐Raf murine sarcoma viral oncogene homolog B1 (BRAF) mutational analysis is used to differentiate LS from sporadic MSI CRC. The role of MLH1 promoter methylation status for the differential diagnosis of these clinical forms is not well established. The objectives of this study were: 1) to analyze MLH1 promoter methylation in MLH1‐deficient CRCs by pyrosequencing, and 2) to assess its role in the differential diagnosis of MLH1‐deficient CRCs.

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

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

New genes emerging for colorectal cancer predisposition

Colorectal cancer (CRC) is one of the most frequent neoplasms and an important cause of mortality in the developed world. This cancer is caused by both genetic and environmental factors although 35% of the variation in CRC susceptibility involves inherited genetic differences. Mendelian syndromes account for about 5% of the total burden of CRC, with Lynch syndrome and familial adenomatous polyposis the most common forms. Excluding hereditary forms, there is an important fraction of CRC cases that present familial aggregation for the disease with an unknown germline genetic cause. CRC can be also considered as a complex disease taking into account the common disease-commom variant hypothesis with a polygenic model of inheritance where the genetic components of common complex diseases correspond mostly to variants of low/moderate effect. So far, 30 common, low-penetrance susceptibility variants have been identified for CRC. Recently, new sequencing technologies including exome- and whole-genome sequencing have permitted to add a new approach to facilitate the identification of new genes responsible for human disease predisposition. By using whole-genome sequencing, germline mutations in the POLE and POLD1 genes have been found to be responsible for a new form of CRC genetic predisposition called polymerase proofreading-associated polyposis.

Epigenética del cáncer

The pathogenesis of cancer includes both genetic and epigenetic mechanisms. The term > refers to any alteration of gene expression, potentially hereditary, which is not accompanied by a modification in the DNA sequence. The effects of epigenetic changes include alteration of DNA transcription, aberrant activation of specific genes, predisposition of genetic instability through alteration of the control of chromosome replication and silencing of the genes implicated in cancer initiation and progression. Among the various epigenetic alterations that lead to altered gene expression, methylation is the main epigenomic mechanism implicated in cancer, whether through a phenomenon of overall hypomethylation or hypermethylation localized in the promoters of specific genes.

Novel MLH1 duplication identified in Colombian families with Lynch syndrome.

Purpose: Lynch syndrome accounts for 2–4% of all colorectal cancer, and is mainly caused by germline mutations in the DNA mismatch repair genes. Our aim was to characterize the genetic mutation responsible for Lynch syndrome in an extensive Colombian family and to study its prevalence in Antioquia.Methods: A Lynch syndrome family fulfilling Amsterdam criteria II was studied by immunohistochemistry and by multiplex ligation-dependent probe amplification (MLPA). Results were confirmed by additional independent MLPA, Southern blotting, and sequencing.Results: Index case tumor immunohistochemistry results were MLH1−, MSH2+, MSH6+, and PMS2−. MLPA analysis detected a duplication of exons 12 and 13 of MLH1. This mutation was confirmed and characterized precisely to span 4219 base pairs. Duplication screening in this family led to the identification of six additional carriers and 13 noncarriers. We also screened 123 early-onset independent colorectal cancer cases from the same area and identified an additional unrelated carrier.Conclusion: A novel duplication of exons 12 and 13 of the MLH1 gene was detected in two independent Lynch syndrome families from Colombia. A putative founder effect and prescreening Lynch syndrome Antioquia families for this specific mutation before thorough mismatch repair mutational screening could be suggested.

Endoscopic requirements of colorectal cancer screening programs in average-risk population. Estimation according to a Markov model

BACKGROUND Although colorectal cancer (CRC) screening strategies are quite common in the United States, their systematic introduction in Europe has been delayed until the year 2008. To estimate endoscopic requirements of four different CRC screening strategies (annual and biennial fecal occult blood testing (FOBT), flexible sigmoidoscopy every 5 years, and colonoscopy every 10 years) in an average-risk population. METHODS A long-term Markov process model was designed combining three adherence rates for the four above-mentioned screening strategies in individuals aged from 50 to 74. Estimations included endoscopic procedures performed for both screening and surveillance purposes. Models were adjusted for age-related adenoma and CRC incidence rates, life expectancy, and cancer-related survival. RESULTS The mean number of annual colonoscopies per 100,000 individuals aged 50-74 ranged from 100 to 271 for annual FOBT, from 75 to 203 for biennial FOBT, from 222 to 601 for sigmoidoscopy, and from 903 to 2,449 for colonoscopy-based strategies, depending on the adherence rate. According to these estimations, annual and biennial FOBT strategies would generate a slight decrease of current endoscopic activity (1.4-3.8% and 2.7-7.2%, respectively), whereas sigmoidoscopy and colonoscopy-based strategies would induce a 4.7-12.8% and 32-87% increase, respectively, with respect to a non-screening scenario. The model confirmed a 3-16% mean reduction of CRC incidence depending on the strategy and adherence rate. CONCLUSION Whereas endoscopic capacity exists for widespread CRC screening with annual or biennial FOBT, implementation of potentially more effective strategies, such as flexible sigmoidoscopy or colonoscopy, would result in a significant increase of current endoscopic resources.

Reassessment colonoscopy to diagnose serrated polyposis syndrome in a colorectal cancer screening population

Background and study aims Serrated polyposis syndrome (SPS) is a high risk condition for colorectal cancer (CRC). Surveillance strategies for patients with serrated lesions remain controversial. We aimed to evaluate a diagnostic strategy to detect SPS consistently during reassessment colonoscopy in patients with proximal serrated lesions. Methods This was a retrospective study of all individuals from a fecal immunochemical test (FIT)-based CRC screening program (2010 - 2013) with one or more serrated lesions of ≥ 5 mm proximal to the sigmoid colon on baseline colonoscopy. We analyzed all individuals empirically scheduled for a reassessment colonoscopy aimed at diagnosing SPS within 1 year. Reassessment colonoscopy was performed with standard white-light or chromoendoscopy ± high definition endoscopy depending on availability. SPS diagnosis was based on the cumulative number of polyps in both the baseline and reassessment colonoscopies. Factors associated with SPS diagnosis were analyzed. Results From 3444 screening colonoscopies, 196 patients met the study entry criteria, of whom 11 patients (0.32 %) met the criteria for SPS on baseline colonoscopy. Reassessment colonoscopies were performed in 71 patients at 11.9 ± 1.7 months and detected 20 additional patients with SPS, a tripling of the rate of SPS up to 0.90 %. Independent factors associated with SPS diagnosis were: having five or more proximal serrated lesions (odds ratio [OR] 4.01 [95 % confidence interval 1.20 - 13.45]; P = 0.02) or two or more sessile serrated polyps ≥ 10 mm (OR 6.35 [1.40 - 28.81]; P = 0.02) on baseline colonoscopy and the use of chromoendoscopy ± high definition endoscopy during reassessment colonoscopy (OR 4.99 [1.11 - 22.36]; P = 0.04). Conclusions A 1-year reassessment colonoscopy using chromoendoscopy and high definition endoscopes substantially improves SPS detection in individuals from a FIT-based screening program with proximal serrated lesions. Five or more proximal serrated lesions or two or more sessile serrated polyps ≥ 10 mm could be thresholds for requiring a reassessment colonoscopy. Prospective studies are required to validate these results and adjust surveillance recommendations in patients with serrated lesions.