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|Year : 2004 | Volume
| Issue : 3 | Page : 115--119
Polymorphism of GSTM1 and GSTT1 genes in prostate cancer: A study from North India
Rama Devi Mittal1, D SL Srivastava1, A Mandhani1, A Kumar1, B Mittal2,
1 Department of Urology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow - 226 014, India
2 Department of Genetics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow - 226 014, India
Rama Devi Mittal
Department of Urology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow - 226 014
BACKGROUND : Glutathione-S-transferases (GSTs) are active in the detoxification of wide variety of endogenous or exogenous carcinogens. The genetic polymorphisms of GSTM1 and GSTT1 genes have been studied earlier to evaluate the relative risk of various cancers. AIM, SETTING AND DESIGN : In the present study, we examined the association of the GSTM1 and GSTT1 gene polymorphisms with sporadic prostate cancer patients in north Indian population. MATERIAL AND METHODS : This case control study was undertaken over a period of 24 months and included 103 prostate cancer patients and 117 controls; both patients and controls originated from northern part of India. The GSTT1 and GSTM1 genotypes were identified by multiplex PCR in peripheral blood DNA samples. STATISTICAL ANALYSIS : Difference in genotype prevalence and association between case and control group were assessed by the Chi square and Fisher Exact tests. RESULTS : Frequencies of null genotypes in GSTT1 and GSTM1, was 11% (13/117) and 30% (35/117) respectively in control individuals. The frequencies of GSTT1 and GSTM1 null genotypes in prostate cancer patients were 34% (35/103) and 53% (55/103) respectively. CONCLUSION : Our study demonstrates that the null genotypes of GSTT1 and GSTM1 are substantially at higher risk for prostate carcinoma as compared to the normal healthy controls. The GSTT1 and GSTM1 null genotypes did not show significant association with tobacco usage in prostate cancer patients. However, the null genotypes were significantly stratified in 50-60 year-old patients when incidence of prostate cancer is high.
|How to cite this article:|
Mittal R, Srivastava D S, Mandhani A, Kumar A, Mittal B. Polymorphism of GSTM1 and GSTT1 genes in prostate cancer: A study from North India.Indian J Cancer 2004;41:115-119
|How to cite this URL:|
Mittal R, Srivastava D S, Mandhani A, Kumar A, Mittal B. Polymorphism of GSTM1 and GSTT1 genes in prostate cancer: A study from North India. Indian J Cancer [serial online] 2004 [cited 2020 Sep 25 ];41:115-119
Available from: http://www.indianjcancer.com/text.asp?2004/41/3/115/12679
Prostate cancer is the most commonly diagnosed cancer in men worldwide and is the second leading cause of cancer related mortality. The underlying mechanisms of the carcinogenesis and the progression of the disease remain largely obscure. Epidemiological studies have shown that dietary, genetic and other environmental factors may be involved in the development of the prostate cancer. The environment-gene interaction in carcinogenesis is well reflected by phase-I and phase-II enzymes that are involved in the metabolism of carcinogens. Phase-II enzymes such as Glutathione-S transferase, N- acetyltransferase and epoxide hydrolase are involved in the detoxification of chemical carcinogens and subsequently their role is expected to be protective.
In human GSTT1 and GSTM1 gene families display a genetic variability due to polymorphic deletions in the respective genes and subsequently both have null genotypes. Several studies have demonstrated that GSTM1 null genotype is a risk factor in lung and bladder cancer., The null genotype of GSTM1 has a decreased capability in detoxifying some carcinogens present in the tobacco smoke. The null genotype of GSTT1 and GSTM1 were also reported to be associated with an increased risk of bladder, breast, colon, oral,, and prostate cancer., Some studies indicated that GSTs polymorphism are associated with prostate cancer,,, others do not.,, Data also suggest that null genotypes of GSTM1 and GSTT1, both individually and in combination, are low-penetrance genetic risk factors for oral cancer in tobacco chewers of Indian ethnicity.,,
Although promising data from these studies are accumulating at a remarkable pace, they are still too sparse to support a role for a specific gene in prostate cancer risk. The present study was, therefore, undertaken to (1) Examine the relative impact of the genetic polymorphisms at the gene loci GSTT1 and GSTM1 on susceptibility to prostate cancer and 2) to investigate the implications of the null genotypes in North Indian prostate cancer patients in relation to the normal controls (both tobacco users and non tobacco users) by using multiplex PCR analysis
Materials and Methods
The study group consisted of 103 prostate cancer patients with mean age 62.5 ± 10.2 and 117 controls (benign prostate hyperplasia) with mean age of 54.5±13.9 Mean value of prostate serum antigen for prostate cancer patients were 12.5 ng/dl and for controls group were 3.4 ng/dl. Criteria for the patient selection were based on questionnaire covering medical, pathological, and histo-pathological records from the outpatient department of Sanjay Gandhi postgraduate institute of medical science, Lucknow from December 2001- December 2003. Only histologically confirmed prostate cancer patients were included. All cancer patients were higher Gleason scores (6-9) and in advance stage. Informed consent of the participants (cases and controls) was taken. Ethnic origin and race for cases and controls were similar. The inclusion criteria for the controls (only men) were absence of any prior history of cancer or pre-cancerous lesions. Serological (prostate serum antigen, DNA extraction and genotyping
Five ml of blood was collected in sterile EDTA vials from all subjects after informed consent. DNA was extracted from blood lymphocytes using the Proteinase K and phenol chloroform extraction procedure. Analysis for GSTM1 and GSTT1 gene polymorphism was done by multiplex PCR as described by Abdel- Rehman et al. Isolated DNA (100-500ng) was amplified in a total volume of 25 ml reaction mixture containing 18.75 pmol of each of the following primers. GSTM1: F- 5'-GAACTCCCTGAAAA GCTAAAGC-3'andR:5'-GTTGGGCTCAAATA TACGGTGG-3';GSTT1:F:5'-TTCCTTACTGGTCCT CACATCTC-3',R:5'TCACGGGATCATGGCC AGCA-3'. As an internal control, exon7 of CYP1A1 genes was co-amplified using the following primer F: 5'-GAACTGCCACTTCAGCTGTCT-3' and R: 5'CAGCTGCATTTGGAAGTGCTC-3'. Each set of reaction included both positive and negative controls. The multiplex PCR method was used to detect the presence or absence of the GSTT1 and GSTM1 genes in the genomic DNA samples, simultaneously in the same tube. The reaction mixture was subjected to initial denaturation at 94șC for 2 min, followed by 35 cycles of 94șC for 2 min, 59șC for 1 min and 72șC for 1 min. The final extension was done at 72șC for 10 min. DNA from positive for GSTM1 and GSTT1 genotypes yielded bands of 215 bp and 480 bp respectively while the internal positive control (CYP1A1) PCR product corresponded to 312 bp.
Statistical analysis was done with SPSS software. Difference in genotype prevalence and association between case and control group were assessed by the Chi square and Fisher Exact tests. Odds ratio (OR) and its 95% Confidence Interval (CI) were obtained by summarizing data over two habit strata (Tobacco users/ non-users) and four age strata (70). Correlation coefficient, OR and 95% CI were used to describe the strength of association
The study included 103 cases and 117 controls. The distribution of the genotypes of GSTT1 and GSTM1 in control and cancer patients (Ca-P) is shown in [Table:1]. Detection of GSTT1 and GSTM1 null allele homozygotes was carried out by sequence- specific amplification using CYP1A1 gene as an internal control. Among patients with prostate carcinoma 34%were homozygous for the GSTT1 null allele as compared to the11% among the controls [Figure:1] ( 2 50 years was significantly more than the controls. However, GSTM1 null genotype alleles were observed to have significant distribution in the age range of 50-60 only in prostate cancer as compared to the controls.
The results of our study and other reports suggest that polymorphic variations in the glutathione S-transferase (GSTs) are associated with cancer susceptibility. It is assumed that the presence of carcinogen-metabolizing enzymes in human prostate with a high inter-individual variability may be involved in the regulation of local levels of carcinogens and mutagens and may underlie interindividual differences in cancer susceptibility. Moreover GSTs also modulate the induction of other enzymes and proteins important for cellular functions. Hence this class of enzyme is important for maintaining cellular genomic integrity and as a result plays an important role in cancer susceptibility.
The results observed indicated that null genotypes of GSTM1 and GSTT1 envisage higher risk for prostate cancer as compared to controls [Table:1]. Our observations concur with previous report in Chilean population where an increased risk of prostate cancer for GSTM1 null genotype was observed; however, differ from USA population where decreased risk of prostate cancer for GSTM1 null genotype was observed. On the contrary in German, Japanese, Portuguese, United Kingdom, and in American studies, no association of GSTM1 null genotype could be established.
In the present study, we observed that GSTT1 null genotype was even more prevalent among prostate cancer patients. Since GSTT1 particularly is strongly involved in the metabolism of lower molecular weight electrophillic molecules the decreased frequency of genotype encoding active GSTT1 than GSTM1 might reflect a greater role of carcinogens of this kind., Interestingly our observation matches to that reported in Scandinavian and German population, but differ from recent American study in prostate cancer patients where an increased frequency of GSTT1positive genotypes was found independent of race. However, in Japanese, Portuguese, United Kingdom, Chilean, and in American studies reported non- significant association. These variations may be possibly attributed to the underlying geographic/ethnic factors.
The association between genetic susceptibility and exposure to the primary environmental risk factor for prostate cancer-tobacco was also investigated [Table:2]. Usually this increase is particularly pronounced among smokers but since the smoking status of the patients was not quantitated sufficiently and due to small number of patients, no significant association could be established between the smokers and non-smokers. It appears that the effect of GSTM1/GSTT1 null alleles is obviously strong enough to be discerned even without prior stratification according to tobacco exposure. Of the various ages strata selected [Table:3] the age between 50-60 years exhibited significant variation between the control and the cancer patients for GSTT1 and GSTM1 null genotypes. This clearly demonstrated that the changes in null genotypes were most significantly pronounced during this age, which also corresponds to cancer susceptibility. This observation is also in agreement to those reported by Chen et al.
There is abundant evidence that polymorphism in individual GST genes are important modulators of cancer susceptibility. The present study indicates that both GSTM1 and GSTT1 genotypes may nevertheless be relevant since an approximate 2-3 fold greater prevalence of null allele homozygotes were found among the prostate carcinoma patients as compared to controls. To the best of our knowledge, this is the first genetic study in Indian population in prostate cancer, which demonstrated that null alleles of GSTT1 and GSTM1 are strong predisposing risk factors for prostate cancer in the North India.
The authors are grateful to the Director, Sanjay Gandhi PGIMS for providing the necessary facilities. One of us (D.S.L. Srivastava) is thankful to Council of Scientific and Industrial Research, New Delhi, for awarding research fellow ship.
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