Polymorphisms in Turkish population

Faculty of Pharmacy, Department of Toxicology, Gazi University, Ankara, Turkey. bensuka@gmail.com

High incidence and poor prognosis of lung cancer make it a major health problem worldwide. Although smoking is a major cause of lung cancer, only some smokers develop lung cancer, which suggests that there is a genetic predisposition in some individuals. 8-OHG is an important oxidative base lesion and may elevate due to cancer and smoking. It is repaired by 8-hydroxyguanine DNA glycosylase 1 (OGG1), which has several polymorphisms. Although the Ser326Cys polymorphism is consistently associated with a range of cancers, findings about this polymorphism and lung cancer risk are contradictory. To date, no study has examined this association in the Turkish population. We conducted a case-control study to investigate the association between OGG1 Ser326Cys polymorphism and the risk of lung cancer using PCR-RFLP. We also evaluated gene-smoking interaction and excretion of urinary 8-OHdG. Our results suggest that the OGG1 Ser326Cys polymorphism is not a genetic risk factor for lung cancer, and that the heterozygous genotype is associated with a significantly reduced risk for lung cancer. The levels of 8-OHdG did not correlate with the polymorphism and smoking. Larger association studies are needed to validate our findings, and mechanistic studies are needed to elucidate the underlying molecular mechanisms of this association.

Istanbul Erenkoy Psychiatric and Neurological Disorders Hospital, Istanbul, Turkey. cemsmile@hotmail.com

BACKGROUND: Oxidative stress and free radical-induced toxicity have been implicated in the pathophysiology of schizophrenia. In this study, we examined paraoxonase (PON1)-55/192 polymorphisms and PON1 activity in patients with schizophrenia, first-degree relatives of schizophrenic patients, and healthy controls. METHODS: This study consisted of 292 healthy participants, 267 unrelated patients with schizophrenia and 311 first-degree relatives of schizophrenic patients. PON1 55 (rs 854560) and PON1 192 (rs 662) polymorphisms were performed by restriction fragment length polymorphism. RESULTS: The frequencies of the QQ and LL genotypes were significantly overpresented in controls compared with those of schizophrenic patients and their relatives. In contrast, the RR genotype was more prevalent in patients than their relatives and healthy controls. The frequencies of the LM and QR genotypes in relatives were higher than controls. Serum PON1 activities of controls were significantly higher when compared with both schizophrenic patients and their relatives. The RR and LL genotypes were associated with a significantly increased PON1 activity as compared with QR or QQ and MM or LM genotypes, respectively, in all groups. CONCLUSION: This is the first study that shows the association between PON1-55/192 polymorphisms and schizophrenia. Our data suggest that the subjects carrying R allele or RR genotype might be susceptible to schizophrenia and subjects with QQ or LL might be protected against schizophrenia. First-degree relatives of schizophrenic patients have higher heterozygote genotypes, suggesting that this group can shift either to patient or control group depending on their allele types and environmental factors. PON1 genetic variations are also associated with PON1 activities. Reduced PON1 activity in patients and their relatives might result from the combined effects of more than one polymorphic variant in PON1 or other genes and/or increased oxidative stress, supporting the hypothesis that reactive oxygen species-mediated cellular damage might contribute to the neuropathology of schizophrenia.

Department of Medical Biology, Faculty of Medicine, Ankara University, Ankara, Turkey guvemg@yahoo.com.

Human P-glycoprotein (P-gp) is encoded by the MDR1 gene, which is located on chromosomal region 7q21 and consists of 28 exons. To date, over 50 single nucleotide polymorphisms (SNPs) have been reported for the MDR1 gene. The effect of these polymorphisms on P-gp function or their clinical impact is in most cases unknown, but some of the SNPs are known to be of functional relevance and can also alter the pharmacokinetics of substrate drugs. The aim of the current study was to analyze for the first time an existing silent MDR1 C1236T (Gly412Gly) polymorphism in a Turkish population. The genotype frequencies of C1236T SNP in a Turkish population were also compared with those in other populations. One hundred unrelated healthy subjects (48 females, 52 males) were included in this study and all them were of Turkish ethnicity. The genotyping of the C1236T SNP was performed by the polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method. The frequencies of the wild-type C and mutant T alleles were 45.5 and 54.5%, respectively. The distribution of C1236T genotype frequencies in our study group was found to be similar to that in Czech, Polish, Portuguese, Russian, Malay, and Japanese populations and different from that in French, German, Chinese, and Indian populations. The distributions of CC, CT, and TT genotypes were 20.0, 51.0, and 29.0%, respectively. Our study provides a framework for future studies concerning the role of polymorphic variants of MDR1 gene in the genesis of various diseases or in designing future pharmacogenetic and pharmacokinetic studies conducted with P-gp substrates in the Turkish population.

Department of Medical Biology and Genetics, Faculty of Medicine, Ondokuz Mayis University, 55139, Samsun, Turkey.

Genetic differences in the metabolism of xenobiotics have recently been suggested as modifiers of individual susceptibility to bladder cancer (BC). The objective of this study was to investigate the relationship between bladder tumor and variants of cytochrome p450 1A2 (CYP1A2) 734 C –> A, cytochrome p450 2D6 (CYP2D6) 1934 G –> A, glutathione S-transferase M1, (GSTM1 null), glutathione S-transferase T1 (GSTT1 null), and glutathione S-transferase P1 (GSTP1) I105 V. We investigated the distribution of these polymorphisms in 135 BC patients and in 128 age and sex-matched cancer-free controls. The polymorphisms were analyzed using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) assay and the multiplex PCR method. Genotype and allele frequencies and their associations with BC risk, demographic factors, smoking status, and tumor stage were investigated. The prevalence of GSTT1 null genotype in cases was 23%, compared with 7% in the control group (OR = 3.94, 95% CI = 1.70-9.38, P = 0.001). There was no association between the studied polymorphisms of CYP1A2, CYP2D6, GSTM1, and GSTP1 genes and BC. There was an association between smoking status and BC. These data seem to indicate that GSTT1 gene polymorphism may be associated with BC in the Turkish population studied. Further studies will be needed to clarify the role of such variation in determining susceptibility to BC.