|Year : 2022 | Volume
| Issue : 2 | Page : 122-125
Genetic polymorphism of carcinogen metabolic enzymes in oral submucous fibrosis
Sunu Ramachandran1, Anita Balan1, C Tinky Bose1, Prabha Balaram2, V Nityasri3
1 Department of Oral Medicine and Radiology, Government Dental College, Trivandrum, India
2 Research Regional Cancer Center, Medical College, Trivandrum, India
3 Kerala University of Health Sciences, Thrissur, Kerala, India
|Date of Submission||25-Jul-2021|
|Date of Decision||03-May-2022|
|Date of Acceptance||05-May-2022|
|Date of Web Publication||22-Jun-2022|
Sarovaram, PRRA 23, Charuvila Lane, Pazhaya Road, Medical College, Thiruvananthapuram, Kerala
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Biotransformation plays a crucial role in carcinogen activity. Genetic polymorphisms in xenobiotic-metabolizing enzymes crucial to a carcinogen and drug metabolism lead to variations in their activity. These enzymes increase cancer risk by an altered action on environmental carcinogens. The objective of this study was to analyze the significance of genetic polymorphisms in CYP1A1 and GSTM1 (carcinogen-metabolizing enzymes) genes in patients with oral submucous fibrosis (OSMF). Method: The study subjects included 50 patients. Twenty-five were diagnosed with OSMF, 5 with malignant transformation in OSMF, and 20 age and sex-matched healthy controls. Genotypes of CYP1A1 and GSTM1 were determined by polymerase chain reaction-restricted frequency length polymorphism. Results: 10%, 40%, and 60% GSTM1 null genotype were observed in normal subjects, OSMF patients, and OSMF patients with malignancy, respectively. 15%, 48%, and 40% CYP1A1 polymorphism were noted in normal subjects, OSMF patients, and OSMF with malignancy, respectively. Conclusion: Polymorphism in CYP1A1 and GSTM1 null genotype may increase the risk of OSMF. Combined polymorphisms may be an increased risk factor than single-gene polymorphism.
Keywords: CYP1A1, genetic polymorphism, GSTM1, oral submucous fibrosis
|How to cite this article:|
Ramachandran S, Balan A, Bose C T, Balaram P, Nityasri V. Genetic polymorphism of carcinogen metabolic enzymes in oral submucous fibrosis. J Indian Acad Oral Med Radiol 2022;34:122-5
|How to cite this URL:|
Ramachandran S, Balan A, Bose C T, Balaram P, Nityasri V. Genetic polymorphism of carcinogen metabolic enzymes in oral submucous fibrosis. J Indian Acad Oral Med Radiol [serial online] 2022 [cited 2022 Dec 7];34:122-5. Available from: http://www.jiaomr.in/text.asp?2022/34/2/122/347915
| Introduction|| |
Oral cancer is one of the most prevalent cancers in India and Southeast Asia, accounting for about 40% of all malignancies., A vast majority of cancers are due to exposure to various environmental agents, which can change the structure and function of genes involved in the growth and development of cells. Most oral cancers are linked to common genetic alterations such as p53, prb, Cyclin D1, Cytochrome P 450, GST, p16 p21, etc. They identify specific biomarkers for oral cancer progression from premalignant lesions such as leukoplakia and oral submucous fibrosis (OSMF) to malignant stages.
The role of gene-environment interactions in disease pathogenesis has been often debated. Several studies indicate that polymorphisms in genes encoding enzymes involved in the metabolism of tobacco, alcohol, and other environmental factors may be linked to individual susceptibility to oral cancers.,,, The gene-environment interactions in carcinogenesis are explained by Phase I (cytochrome p450) and Phase II (Glutathione S Transferases) enzymes involved in the metabolism of carcinogens.
Genetic polymorphisms are widespread and play a major role in human diseases. The superfamilies of cytochrome p450 (phase I) enzymes catalyze the oxidative metabolism of most endogenous and exogenous chemicals. For CYP1A1 polymorphism, a T to C transition in the 30 noncoding regions (a thymine/cytosine point mutation) has been confirmed to be related to the high risk of lung and head and neck cancers. In addition, CYP1A1 polymorphism, an amino acid substitution from isoleucine to valine at codon 462, shows the effects of enhancing catalytic activity and increasing the risk for lung cancer., For glutathione-S-transferase M1(GSTM1), the polymorphism includes the present genotype and null genotype, which are associated with the abnormal function of GSTM1 enzyme, an important member in the detoxification of carcinogens in tobacco smoking.
This study aimed at determining whether the presence of genetic polymorphism of CYP1A1 genes and GSTM1 genes predisposes patients to OSMF and subsequent malignant transformation.
| Methodology|| |
The study was conducted in the Department of Oral Medicine and Radiology in collaboration with the division of cancer research, Regional Cancer Center, Thiruvananthapuram, for 2 years. The study was approved by the Hospital Ethics Committee/Institutional Review Board NO: HEC/IRB/05 dtd 28/05/2005 and by Helsinki consideration. Good clinical practice guidelines were followed. Written informed consent was obtained from every participant. The sample size was calculated using the formula 4pq/d2, where p is the proportion of patients with Cyp1A1 genetic polymorphism, q is 100-p, and d is the precision taken as 20%. Thus, the minimum sample size required was 25. The patients who reported to the outpatient clinic were screened for the features suggestive of OSMF, and their clinical data were documented. Thirty patients were selected for the study based on OSF's clinical and histopathological features, in which malignant transformation and significant polymorphism were observed in five patients; hence, they were grouped separately. Twenty patients were only selected for normal samples because obtaining consent from those groups was difficult. Hence, fifty patients selected for the study after obtaining the written consent were grouped into Normal, OSF, and OSF with malignancy. Tissue samples and 2 mL of peripheral venous blood were collected from the arm vein in a heparinized test tube for normal and OSMF patients. Genomic DNA was checked using 0.8% agarose gel electrophoresis. The genetic polymorphisms of CYP1A1 and GSTM1 were analyzed by polymerase chain reaction-restricted frequency length polymorphism using specific primers. Beta globin was used as internal control and amplified in all the samples. Bands for GSTM1 and CYP1A1 genes were observed using a gel doc system [Figure 1] and [Figure 2]. Statistical analysis was performed using SPSS. The various parameters were compared using Chi-square tests. The association of observed values and clinical parameters was assessed using a one-way analysis of variance (ANOVA).
| Results|| |
The age of the study subjects ranged from 25–75 years, with a slight female predominance. In the normal group, only two patients had habit of chewing. All patients diagnosed with OSF and OSF with malignancy had the habit of betel quid chewing and exhibited a higher frequency and longer duration of betel quid chewing, many of whom were chewers of commercial tobacco preparations. 10% of the OSF patients included in the study were also diagnosed with a leukoplakic patch on the tongue.
In this study, GSTM1 polymorphism was observed in normal subjects, OSF patients, and OSF patients at 10%, 44%, and 60%, respectively [Table 1] and [Figure 3]. Using Chi-square analysis, it was noted that genetic polymorphism was higher in the subjects diagnosed with OSF when compared to normal groups and the difference was statistically significant (P-value - 0.013). Among subjects of both OSF and OSF with malignant transformation groups, many females showed genetic polymorphism. Significantly, it was also observed that all subjects with GSTM1 polymorphism were habitual chewers of tobacco preparation. Among the 30 OSF subjects, including those with malignancy, it was observed that three had oral leukoplakia. Among the three patients, polymorphism was observed in two patients, and both of them were only GSTM1 polymorphic.
With the help of a gel doc system, the study observed 15% CYP1A1 polymorphism in normal samples, 48% polymorphism in OSF samples, and 40% polymorphism in OSF with Ca samples [Table 2] and [Figure 4]. Compared to the frequency of genetic polymorphism between OSF and normal cases, the genetic polymorphism was significantly higher in OSF than in controls (P-value 0.02). It was observed that none of the three patients with leukoplakia showed CYP1A1 polymorphism, contrary to the observations of the presence of GSTM1 polymorphism. The twenty-five OSF patients were divided into early, moderate, and advanced grades according to the histopathologic grading criteria of Sirsat and Pindborg. The study noted an increased expression of polymorphism in moderate cases. Among the twenty five patients, eight showed only GSTM1 deletion, nine were only CYPA1 polymorphic, and three showed combined polymorphism.
| Discussion|| |
Epidemiological studies have demonstrated a remarkable influence of various harmful habits in developing oral cancer. OSMF is one of the most common oral premalignant conditions. The role of gene-environment interaction in carcinogenesis has recently gained much interest. Several studies indicate that polymorphisms in genes encoding enzymes that are involved in the metabolism of carcinogens present in tobacco smoke, alcohol, and other environmental factors may be linked to individual susceptibility to oral cancer. Carcinogen-metabolizing enzymes are expressed in oral mucosa, suggesting that carcinogen metabolism could occur at this site. Differences in enzyme activity in the oral cavity could represent one mechanism by which oral cancers and precancers occur.
Polymorphism in CYP1A1 and GSTM1 null genotypes may increase the risk of OSMF. Sreelekha et al., who conducted a similar study, suggested that polymorphism of CYP1A1 and GSTM1 null genotype in Indian subjects may confer an increased risk of cancers of the oral cavity. Genetic polymorphism and increased lifetime exposure to various environmental factors may pose a greater threat to OSF. An extensive review did not show any association between genotypes and sex. GSTM1 null genotype may increase the risk of developing leukoplakia more than CYP1A1 polymorphism. It was observed in the present study that of the 29 habitués with genetic polymorphism, 24 persons had developed OSF, of whom four had malignancy also. Notably, 82.7% of persons with genetic polymorphism exposed to carcinogens had developed OSF [Table 3] and [Table 4]. Thus, it may be proposed that genetic factors and the betel quid's carcinogenic potential may increase the risk of developing oral cancers and precancers. Seedat and Van Wyk, in their series on OSF in Durban Indians with and without the habit of chewing pan, suggested genetic predisposition for the occurrence of OSF., CYP1A1 polymorphism results in increased metabolic activity, whereas the null genotype of GSTM1 has decreased capability to detoxify some carcinogens. As a result of polymorphisms, the number of carcinogens present in the body increases, leading to the development of cancers and precancers. Therefore, it may be suggested that the balance between CYP and GST enzymes may substantially influence cancer risk. A longer duration of deleterious oral habits in polymorphic patients contributes to oral carcinogenesis. Little et al. had advocated that the occurrence of oral premalignant lesions and malignancies depends on the amount, frequency, and duration of betel quid chewing.
Subjects with combined polymorphism are probably at an increased risk. Sato et al. indicated that combined genotyping of CYP1A1 and GSTM1 genes revealed higher relative risk than that ascribed to a single gene, particularly those at low cigarette dose levels. In conclusion, our results revealed that the null genotype of GSTM1 influences the risk of developing OSF. It has been reported that GSTM1 is involved in detoxifying polycyclic aromatic hydrocarbons and other mutagens. Cells from GSTM1 null individuals are more susceptible to DNA damage caused by these agents. At the same time, Chaudhuri et al. showed an increased risk for OSMF in CYP1A1 in Eastern India.
The limitation of our study was we had only five patients with OSMF with malignancy. OSF development is multifactorial; additional environmental and genetic parameters could also be risk factors. Thus, further studies on larger sample sizes and different populations need to be carried out to assess the accurate role of the carcinogen-metabolizing enzyme, especially Cyp1A1, as a risk factor for developing OSF and malignancy.
| Conclusion|| |
This study showed that the polymorphism of CYP1A1 and GSTM1 null genotype might increase the risk of developing OSMF. Accumulation of such information on individual susceptibility to certain types of cancers will be valuable for identifying high-risk individuals and preventing the possible development of cancer by reducing the intake of carcinogenic substances and introducing chemo-preventive measures.
Declaration of patient
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
We want to thank all the study participants for taking part in the study. We express our gratitude to Mrs. Sreelekha, the Research Scientist, and other staff and students in the division of cancer research, RCC, Trivandrum, for their support and contribution in conducting this study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]