Bani Sengupta

Prevalence of CYP1A1 and GST Polymorphisms in the Population of Northeastern India and Susceptibility of Oral Cancer

Individual cancer susceptibility is the result of several host factors, including differences in lifestyle habits and genetic susceptibility. There is a correlation between CYP1A1 polymorphism (MspI) and oral cancer susceptibility. Individuals carrying the deletions of GSTM1 and GSTT1 are at high risk of developing oral cancers. In the present study on healthy tribal and nontribal individuals of Assam, we found that the genetic variation of GSST polymorphisms is evident (p = 0.20) with differential dose of toxic exposure. Prevalence of different polymorphic alleles of CYP1A1 also proves the same result. A mini-case-control study with very small sample size showed no marked increase in the risk of developing oral cancer as the frequencies of the studied GST genotypes did not show any statistical significance. But GSTT1-null genotypes were found to have higher risk of developing leukoplakia (OR 1.94, 95% CI 2.61-18.54). CYP1A1 genotype m2 allele was also not found to be associated with the risk of developing leukoplakias in the population.

α-Thalassemia Among Tribal Populations of Eastern India

Five hundred and thirteen unrelated subjects belonging to various tribes of West Bengal, Arunachal Pradesh and Assam in Eastern India, were screened for the presence of α-thalassemia (thal) gene deletion(s) as a possible cause of unexplained anemia (Hb <11 g/dL and/or MCH <28 pg, MCV < 78 fL). As reported earlier, β-globin gene mutant alleles were found with a frequency of up to 20% in some tribes. In the present study, α-globin gene deletion alleles were found in 18% of subjects from West Bengal, 3.9% from Arunachal Pradesh and 3.84% from Assam tribesmen. Coexistence of α- and β-globin gene abnormalities was observed in up to 18% of some tribal groups. The high inbreeding rate and lack of appropriate medical care make these populations particularly vulnerable.

Cytogenetic monitoring in human oral cancers and other oral pathology: the micronucleus test in exfoliated buccal cells.

Oral cancer is a lifestyle-related cancer, with tobacco as a primary factor. Progression of oral cancer develops over several years from the stage of leukoplakia, erythroplakia, etc. A micronucleus test was applied to oral mucosal cells, considering them as the target site for carcinogens and cytogenetic damage. The test has been established as a reliable biomarker for differential prevalence of MN indices among oral cancers, pre-cancers, non-malignant oral pathologies, and healthy controls for the first time. Buccal scrapings were collected from 63 patients with cancer and pre-cancerous lesions, 42 with non-malignant oral problems, and 100 healthy controls. The analysis revealed that MN frequencies in cancer and pre-cancerous cases were 4-fold elevated (p < 0.001) and 3.87-fold (p < 0.002) elevated for other non-malignant pathologies. Significant associations between use of tobacco in various forms and development of oral pathologies are also established. The relative cancer risk for smoking healthy controls with a definite MN frequency was also found to be significant. The results indicate the validity of the MN test as a cytogenetic marker for the development of several oral pathologies.

Anemia and hemoglobinopathies in tribal population of Eastern and North-eastern India.

Abstract It is estimated that out of approximately 31.4 million people living in North-eastern India, about 8.1 million are tribal people of the hills and plains. Among four of the seven north-eastern states, tribal people are in majority. Arunachal Pradesh is made of approximately 24 major tribal groups, which constitute about 70% of the total population, Tripura 29% and in Assam constitutes 11%. A total of 1726 cases were randomly selected in this study, out of which 1263 cases were from North-east India, namely from Arunachal Pradesh, Assam, Tripura and the rest were from West Bengal. Hematological parameters were estimated and agarose gel electrophoresis for identification of the Hb variants was performed. DNA was isolated, amplified and analysed by PCR-ARMS technology. The incidence of anemia among the tribal people of Assam was 59.82%, in Arunachal Pradesh 53.77% and Tripura 57.45%. The presence of hemoglobinopathies and thalassemia account for anemia in a sizeable population of the north-eastern states in certain tribes and urgent health resources are needed to deal with this. HbE appears to be the commonest hemoglobin among the different tribes of north-east.

Interaction of different hemoglobinopathies in Eastern India with a view to establish genotype-phenotype correlation.

Analysis of the molecular basis of hemoglobinopathies provides an opportunity to define genotype–phenotype variations as well as establish the origin of mutation. The present study deals with a large cohort of 1,661 cases referred to the counseling unit and 889 individuals from random screening of the population of Tripura. Characterization of mutation in 291 cases (582 alleles) was performed by the PCR‐ARMS method using genomic DNA. The haplotype of 56 βE mutation‐bearing chromosomes were identified by the RFLP‐PCR method. Genotypes were constructed and correlated with hematological and clinical phenotypes. IVS‐1nt 5 (G→C) mutation was observed as the most frequent mutation, followed by codon 30 (G→C). Production of HbE was significantly (P < 0.001) higher in nontransfusion‐dependent Eβ‐thalassemia patients. βE mutation was observed only on four haplotypes linked to framework 2. Type 2 haplotype was observed mainly from chromosomes of Tripura origin, but none from South Bengal. Homozygous E individuals with 1//1 genotype were significantly (P < 0.01) more anemic compared to individuals with 2//2 genotype. This work creates a database of hemoglobinopathy mutations for the population of Eastern India which will facilitate prenatal diagnosis and counseling. Am. J. Hum. Biol. 12:454–459, 2000.

Polymorphism of ACE gene as the genetic predisposition of coronary artery disease in Eastern India

AIM A case control study was designed to assess whether the prevalence of ACE gene polymorphism has any role in the development of CAD. METHODS The study included unrelated 217 cases with CAD and 255 healthy controls. PCR was done using primers followed by agarose gel electrophoresis for study of different ACE gene polymorphisms. Multiple logistic regression analysis was carried out to find association between studied genotypes and lifestyle as well as biochemical risk factors. RESULTS Both DD [OR: 2.16; 95%CI: (60.60-67.40)] and ID [OR: 1.48; 95%CI: (93.28-97.72)] genotypes of the ACE gene showed significant associations in the development of CAD. Coexistence of diabetes and hypertension found to be risk modifier of the disease. Tobacco intake in various forms elevates the risk of the disease among the cases with risk genotypes. CONCLUSION ID and DD genotypes of ACE gene came out to be predisposing factors for the CAD cases in our study population.

Polymorphisms of CYP1A1, GSTM1 and GSTT1 Loci as the Genetic Predispositions of Oral Cancers and Other Oral Pathologies: Tobacco and Alcohol as Risk Modifiers

Polycyclic aromatic hydrocarbons of tobacco require activation by phase I enzymes, such as cytochrome-P4501A1 (CYP1A1) to become an ultimate carcinogen, which are subjected to detoxification by phase II enzymes, especially glutathione S-transferases (GSTs). A study was designed to find whether genetic predisposition are risk modifiers of oral pathologies. The study included 102 cases with Oral Cancers (OCs), 68 cases with nonmalignant pathologies, 100 cases as control group. GSTM1 null genotype was associated with increased risk of OCs but not with benign pathologies. Deleted GSTT1 was associated with all pathologies. Both m1m2 and m2m2 polymorphisms of CYP1A1 were associated with oral pathologies.

Polymorphisms of methylenetetrahydrofolate reductase gene as the genetic predispositions of coronary artery diseases in eastern India

Background: Gene–environment interaction is an important aspect in the development of coronary artery disease (CAD). The mutation (677C-T) of methylenetetrahydrofolate reductase (MTHFR) gene results in a decrease of the enzyme activity that leads to mild hyperhomocysteinemia. Elevated plasma level of homocysteine has been recognized as an independent risk factor for cardiovascular disease. A case–control study was designed to assess whether the prevalence of some MTHFR gene polymorphisms have any role in the development of CAD. Materials and Methods: The study included unrelated 217 cases with CAD and 255 healthy controls. DNA was extracted from peripheral blood. MTHFR genotypes were identified by seeing the presence or absence of 677C→T mutation obtained by PCR followed by Hinf1 restriction digestion. Multiple logistic regression analysis was carried out to find association between studied genotypes and lifestyle as well as biochemical risk factors. Results: The T allele was found to be associated with the disease. Significant associations were found with smoking, hypertension, diabetes, and family history of CAD. Conclusion: The results indicate that MTHFR 677C-T polymorphism has significant association with CADs in the population of eastern India.

Prenatal Diagnosis of Thalassaemias

Abstract In an aim to reduce the birth of children with β-thalassemia and other haemoglobinopathies with immediate effect a study was undertaken to screen the thalassemia carriers from a population of pregnant women attending the antenatal clinic of Ramakrishna Mission Seva Pratisthan hospital over a period of 5 years (1995-1999). From a total of 1962 female pregnant patients 7.04 % thalassemia carriers were identified by electrophoresis and HbA2 estimation. NESTROFT test was also tried as another screening method as a simple and inexpensive method which showed comparable results. The husbands of these carrier mothers (138 in number) were offered carrier detection and 68.84% responded from which 15.8% carriers (15 in number) were identified. From these high risk couples only 6 agreed for prenatal diagnosis. 19 other couples were also identified as couples “at risk” from 133 referred antenatal cases who came for investigation of anaemia. Thus a total of 25 couples opted for prenatal diagnosis by DNA analysis. 26 pregnancies from 25 couples were investigated (one parent came twice). Prenatal diagnosis by DNA analysis showed 30.77% affected foetus having thalassemia mutations in homozygous or double heterozygous state while 69.23% were unaffected (foetus normal or having mutation in heterozygous state).

High Incidence of Haemoglobin-E in Tribal Populations of Tripura, North East India

Abstract A large cohort of 80 randomly selected individuals from 12 different tribal groups and a group of 196 tribal school children of Tripura, N.E. India was studied to analyse the incidence and origin of HbE mutation in these populations. βE allele frequency was highest among Mareks (0.5625). In three tribal groups mutant allele frequency was higher than the normal allele frequency of β -globin gene. Analysis of 30 β E mutation bearing chromosomes shows that this mutation is present only on four different haplotype back grounds, all linked to framework 2.(5’+++ β E – -3’) haplotype was most prevalent in the present study group, which indicates the origin of codon 26 (G’!A) as a single mutation in this region. Among the 104 randomly selected individuals of Debbarman tribals of mixed age group β E frequency was 0.4086, while in the 196 school children aged 12 to 14 years and belonging to same tribal group β E frequency was 0.4923. This apparent increase in β E frequency cannot be treated as clear-cut indication of selection of mutant allele.