Regulation of MLH1 mRNA and protein expression by promoter methylation in primary colorectal cancer: a descriptive and prognostic cancer marker study.

BACKGROUND: In colorectal cancer MLH1 deficiency causes microsatellite instability, which is relevant for the patient's prognosis and treatment, and its putative heredity. Dysfunction of MLH1 is caused by sporadic gene promoter hypermethylation or by hereditary mutations as seen in Lynch Syndrome. The aim of this study was to determine in detail how DNA methylation regulates MLH1 expression and impacts clinical management. METHODS: Colorectal cancer samples were collected from 210 patients. The laboratory methods used to study these samples included methylation specific multiplex ligation-dependent probe amplification (MS-MLPA), real-time quantitative PCR (qPCR), and immunohistochemistry (IHC). RESULTS: We found that the MLH1 mRNA and protein expression levels were highly related. MS-MLPA was successful in tumors from 195 patients. In these tumors, hypermethylation was observed in promoter regions A (n = 57), B (n = 30), C (n = 28), and D (n = 47), and in intron 1 (n = 25). The promoter region C and intron 1 methylation levels were found to be excellently suited for discriminating between low and high gene expression levels, whereas those of promoter regions A, B and D were less specific. Hypermethylation in any region (n = 77) served as an independent prognostic factor (hazard ratio 0.56, 95 % confidence interval 0.36-0.89, p = 0.01). CONCLUSIONS: MLH1 inactivation through hypermethylation was found to be related to improved survival. Hypermethylation in promoter region C and intron 1 served as the most specific markers for this inactivation.

Gene expression of the mismatch repair gene MSH2 in primary colorectal cancer.

Microsatellite instability (MSI) is caused by defective mismatch repair (MMR) and is one of the very few molecular markers with proven clinical importance in colorectal cancer with respect to heredity, prognosis, and treatment effect. The gene expression of the MMR gene MSH2 may be a quantitative marker for the level of MMR and a potential molecular marker with clinical relevance. The aim was to investigate the gene expression of MSH2 in primary operable colorectal cancer in correlation with MSI, protein expression, and promoter hypermethylation. In a cohort of 210 patients, the primary tumor and lymphnode metastases were analyzed with immunohistochemistry, methylation and MSI analyses, and quantitative polymerase chain reaction (PCR). The median gene expression of MSH2 was 1.00 (range 0.16-11.2, quartiles 0.70-1.51) and there was good agreement between the gene expression in primary tumor and lymph node metastasis (Spearman's rho = 0.57, p < 0.001, n = 73). The validity of gene expression analysis was made probable by a significant correlation to protein expression (p = 0.005). MSI was most often caused by deficient MLH1 and was not correlated to MSH2 expression. Hypermethylation of the MSH2 gene promoter was only detected in 14 samples and only at a low level with no correlation to gene expression. MSH2 gene expression was not a prognostic factor for overall survival in univariate or multivariate analysis. The gene expression of MSH2 is a potential quantitative marker ready for further clinical validation.

Incidence, etiology and prognosis of first-time acute pancreatitis in young patients: a population-based cohort study.

BACKGROUND/AIMS: The etiology of acute pancreatitis (AP) seems to have changed during the last two decades, and since detection of mutations in the gene for cationic trypsinogen(PRSS1) causing hereditary pancreatitis some patients formerly diagnosed with idiopathic AP (IAP) turn out to have a genetic cause. METHODS: Data on patients <30 years of age, diagnosed with AP identified in the Danish National Registry of Patients, were retrieved. Patients previously diagnosed with IAP were offered genetic counseling and testing for mutations in the PRSS1, the Serine Protease Inhibitor Kazal type1 (SPINK1) and the Cystic Fibrosis Transmembrane Conductance Regulator gene (CFTR). RESULTS: The standardized incidence ratio (SIR) of AP increased from 3.56 per 100,000 person-years in the period 1980-1984 to 6.43 in 2000-2004 (p < 0.01). The SIR of women surpassed that of men in 1999. Among patients with former IAP, 3 had hereditary pancreatitis, 3 CFTR and 4 SPINK1 mutations after re-evaluation. CONCLUSION: The incidence of AP, especially in women, increased over time. More patients had gallstone-related and less alcohol-related AP in the period 1999-2004 compared to 1980-1999. Genetic causes of AP were found in 32% of those tested with IAP and as a minimum estimation in 4% of the total cohort. and IAP.

Genetic, epidemiological, and clinical aspects of hereditary pancreatitis: a population-based cohort study in Denmark.

OBJECTIVES: In a population-based, well-defined group of patients first regarded as having pancreatitis of unknown origin (PUO), we identified, described, and compared the clinical and genetic aspects of patients with hereditary pancreatitis (HP) and with cystic fibrosis transmembrane conductance regulator gene (CFTR) and serine protease inhibitor Kazal type 1 gene (SPINK1) mutations with patients who retained the diagnosis of true idiopathic pancreatitis (tIP) after genetic testing for HP, SPINK1, and CFTR mutations. METHODS: Patients with PUO were identified in the Danish National Registry of Patients or were referred by clinicians. DNA from blood was analyzed for cationic trypsinogen (PRSS1), SPINK1, and CFTR mutations. Considering the diagnosis of HP, a pedigree was drawn for each patient. RESULTS: A genetic mutation was found in 40% of 122 patients with PUO. After testing first-degree relatives of the 18 initially identified HP patients, 38 HP patients in total were identified, and 28 patients had SPINK1-CFTR mutations. Among HP patients, no p.N29I mutations were found and the p.A16V mutation was more frequent than previously reported, 45 and 32% had exocrine and endocrine insufficiency, respectively, and among tIP patients 9 and 12%, respectively. Pancreatic cancer was diagnosed in 5% of the HP families. CONCLUSIONS: The genotype of the Danish population with HP differs from that of previously described cohorts. The occurrence of exocrine and endocrine insufficiency is higher among patients with HP than in patients with SPINK1-CFTR mutations and tIP, and more HP families develop pancreatic cancer. Genetic testing thus helps to predict the prognosis of the pancreatitis.

Molecular biology from bench-to-bedside - which colorectal cancer patients should be referred for genetic counselling and risk assessment.

Lynch syndrome is associated with deficiency of the mismatch repair genes MLH1, MSH2, MSH6 or PMS2. However, most MLH1 deficient tumours are sporadic in origin, and they can be identified if harbouring a BRAF V600E mutation or hypermethylation of the MLH1 gene promoter. The aim of this study was to validate our previously suggested clinically applicable strategy based on molecular characteristics for identifying which patients to refer for genetic counselling. The strategy was validated in an unselected cohort of 287 colorectal cancer patients. All tumours were tested for MLH1, PMS2, MSH2 and MSH6 protein expression with immunohistochemistry. DNA from MLH1 negative tumours was sequenced for BRAF mutations. If BRAF was wild-type, MLH1 promoter was subsequently analyzed for promoter hypermethylation. Most tumours, 251 (88%), stained positive for all four proteins. Six (2%) had negative MSH2 and one (<1%) isolated loss of MSH6. MLH1 and PMS2 were negative in 29 cases (10%). DNA quality allowed BRAF analysis in 27 of these with 14 mutations and 13 wild-type. DNA quality allowed methylation analysis in 11 of the 13 BRAF wild-type, and all but one were methylated. Subsequently, Lynch syndrome could not be ruled out in 12 patients. A follow-up at 8-10 years revealed four definite cases of Lynch syndrome and three highly suspicious. An easy and clinically applicable step-wise approach with immunohistochemistry (100%), BRAF sequencing (10%) and methylation analysis (5%) identified several patients with hereditary cancer. It is feasible to perform a molecular screening to select patients for genetic counselling.

Incidence, prevalence, etiology, and prognosis of first-time chronic pancreatitis in young patients: a nationwide cohort study.

BACKGROUND/AIMS: Publications on etiology of chronic pancreatitis (CP) are infrequent. Etiologies today encompass genetic disorders. We wanted to describe etiologies of today and identify patients with genetic disorders like hereditary pancreatitis (HP), mutations in Serine Protease Inhibitor Kazal type1 (SPINK1), and the Cystic Fibrosis Transmembrane Conductance Regulator gene (CFTR) among patients formerly considered to have idiopathic CP. METHODS: Data on patients diagnosed with first-time CP < 30 years of age in Denmark identified in the Danish National Registry of Patients were retrieved. Patients previously considered to have idiopathic pancreatitis were offered genetic counseling and evaluation for HP, SPINK1, and CFTR mutations. RESULTS: In the period 1980-2004, 580 patients < 30 years of age presented with CP, the standardized prevalence ratio of CP increased from 11.7 per 100,000 person years in 1980-1984 to 17.0 per 100,000 in 2000-2004 (p < 0.001). The odds ratio (OR) having gallstone-related CP increased in the latter time period, especially in women, that of alcohol-induced CP decreased over time. OR having idiopathic CP increased in the latter period; 50% of patients with idiopathic pancreatitis accepted genetic reevaluation; 28 patients had a genetic mutation that totally or partly could explain their pancreatitis, nine of these had two, and 11 patients had HP. CONCLUSION: The prevalence of CP, especially in women, increased over time. Genetic causes that partly or totally could explain the CP were found in 54.90% (95% CI (40.45-68.62)) of those with idiopathic CP, as a minimum estimation 1.9% (95% CI (1.00-3.47)) of the total cohort had HP.

Microsatellite instability and the association with plasma homocysteine and thymidylate synthase in colorectal cancer.

The possible associations between microsatellite instability, homocysteine and thymidylate synthase were investigated in tumors and plasma from 130 patients with colorectal cancer. Other analyses included thymidylate synthase and 5,10-methylene-tetrahydrofolate reductase gene polymorphisms, carcinoembryonic antigen, vitamin B12, and folate. Microsatellite instability of tumors was associated with higher levels of plasma homocysteine (p = 0.008) and higher protein expression of thymidylate synthase (p < 0.001). Supplemental analyses ruled out that the finding could be explained by the other analyzed factors. CEA was not associated with neither homocysteine nor microsatellite instability. The data suggests that there is a more pronounced methyl unit deficiency in microsatellite instable tumors.