Common polymorphisms in GSTM1, GSTT1, GSTP1, GSTA1 and susceptibility to colorectal cancer in the Central European population

Renata Hezova 0 Julie Bienertova-Vasku 2 3 Milana Sachlova 0 Veronika Brezkova 0 Anna Vasku 3 Marek Svoboda 0 Lenka Radov 4 Igor Kiss 0 Rostislav Vyzula 0 Ondrej Slaby 0 1 0 Department of Comprehensive Cancer Care, Masaryk Memorial Cancer Institute , Zluty kopec 7, 656 53, Brno , Czech Republic 1 Central European Institute of Technology, Masaryk University , Kamenice 753/5, 625 00, Brno , Czech Republic 2 Department of Paediatric Oncology, Masaryk University affiliated Hospital , Cernopolni 22, 612 00, Brno , Czech Republic 3 Department of Pathological Physiology, Medical Faculty, Masaryk University , Kamenice 753/5, 625 00, Brno , Czech Republic 4 Laboratory of Experimental Medicine, Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University and University Hospital in Olomouc , Krizkovskeho 8, 771 47, Olomouc , Czech Republic Background: Central Europe presents with the highest incidence of sporadic colorectal cancer (CRC) worldwide. As sporadic CRC represents a typical multifactorial disease, it is characterized by intense interaction of the genetic background with the environment. Glutathione S-transferases could act as attractive susceptibility genes for CRC, as they are directly involved in conjugation between glutathione and chemotherapeutics, environmental pollutants and a wide spectrum of xenobiotics. Methods: In this study, we investigated associations of polymorphisms in glutathione S-transferases (GSTs) genes, that is GSTA1, GSTT1, GSTM1 and GSTP1, with CRC in a total of 197 cases and 218 controls originating from the Czech Central European population. Polymorphisms were assessed by polymerase chain reaction/restriction fragment length polymorphism-based methods, allele-specific multiplex and allelic discrimination by real-time polymerase chain reaction. Results: None of investigated polymorphisms showed any associations with CRC, with the exception of GSTP1; where the heterozygote genotype Ile105Val was associated with decreased risk of CRC (P = 0.043). Conclusions: The frequencies observed in our study are in accordance with those from other European Caucasian populations. Based on our studies, examined variability in GST genes is not a major determinant of CRC susceptibility in the Central European population. - Background Colorectal cancer (CRC) represents the third most frequent type of cancer among males and the second most common cancer in females worldwide. Worldwide, every year, more than 1 million individuals will develop colorectal cancer and the disease-specific mortality rate is nearly 33% in the developed world [1], making the disease a substantial health as well as economic burden on society. Sporadic CRC is a typical multifactorial disease arising from maladaptive interaction between genetic background and certain environmental factors, such as diet or lifestyle, however, the exact role of the genetic background to sporadic CRC remains unclear. Glutathione S-transferases (GSTs) represent a superfamily of phase II metabolic enzymes that catalyze the conjugation between glutathione and chemotherapeutic drugs, carcinogens, environmental pollutants, and a broad spectrum of xenobiotics. GSTs are involved in the metabolism of isothiacyanates (ITCs), naturally occurring molecules that were recently shown to inhibit development of tumors in many experimental models [2] and that also induce apoptosis in human colon cancer cells [3]. GST izoenzymes are encoded by three separate families of genes (designated cytosolic, microsomal and mitochondrial transferases), with distinct evolutionary origins, which provide mammalian species with protection against electrophiles and oxidative stressors in the environment. Members of the cytosolic class Alpha, Mu, Pi and Theta GST, and also certain microsomal transferases (MGST2 and MGST3), are upregulated by a diverse spectrum of foreign compounds typified by phenobarbital, 1,4-bis[2-(3,5-dichloropyridyloxy)] benzene, pregnenolone16-carbonitrile, 3-methylcholanthrene, 2,3,7,8-tetrachlorodibenzo-p-dioxin, -naphthoflavone, butylated hydroxyanisole, ethoxyquin, oltipraz, fumaric acid, sulforaphane, coumarin, 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28oyl]imidazole,12-O-tetradecanoylphorbol-13-acetate, dexamethasone and thiazolidinediones. The polymorphisms in these genes lead mostly to reduction of enzymatic activity, for example, homozygotes for polymorphisms C69T in GSTA1 genes have reduced enzymatic activity compared to the wild-type homozygotes [4]. Also GSTP1, the most frequently distributed GST isoenzyme [5], harbors a functional polymorphism (rs1695, Ile105Val) [6] resulting in a lower enzyme activity [7]. Null genotype with no enzymatic activity in GSTM1 gene was reported in 40 to 60% of Caucasians [8] and GSTT1 null genotype is present at a frequency of 10 to 20% in Caucasian population [9]. Individuals with reduced GST enzymatic activity may present with decreased metabolism of ITCs, which could result in an increased pool of ITCs and, therefore, modified CRC risk. The Central European population represents a population with extremely high incidence of CRC [10] and it could well serve as a model population for the study of the genetic background to CRC. The role of GST izoenzymes has been already studied in the Czech population of 495 CRC patients in a larger multicentric study. The aim of our study was to replicate these findings on a smaller, highly homogeneous cohort [11] of CRC patients, that is, to determine whether common genetic polymorphisms in the most important isoenzymes of the GST family (GSTA, GSTM1, GSTP1 and GSTT1) predispose to the development of CRC cancer in this model population. Methods Patients and controls De novo diagnosed cases of CRC treated at the Masaryk Memorial Cancer Institute, Czech Republic, between January 2008 and December 2010 were enrolled into this study. The cases comprised a total of 197 subjects [105 men, 92 women; age (mean SD): 63 9 years) with the histologically confirmed diagnosis of CRC, whereas the control group included 218 cancer-free blood donor volunteers recruited from the same institute, had a similar age distribution (96 men, 122 women; mean age: 66 16 years) and had no previous personal history of cancer. Colonoscopy was not performed in controls to exclude CRC, but all subjects were symptom-free and presented with no anemia. All subjects had the same ethnicity (Caucasian). Written informed consent approved by the local ethical review board was obtained from all subjects and was archived. DNA isolation and genotyping Genomic DNA was isolated from whole peripheral blood using MagNA Pure DNA Isolation Kit (Roche Applied Science, Indianapolis, IN, USA). DNA concentration was measured on Nanodrop ND-1000 (NanoDrop Technologies Inc., Wilmington, DE, USA). For analyses of SNPs rs1695 in GSTP1 Ile105Val realtime PCR allelic discrimination was performed on a StepOne Real-Time PCR instrument (Life Technol (...truncated)