Ravindran Ankathil

Possible risk modification by CYP1A1, GSTM1 and GSTT1 gene polymorphisms in lung cancer susceptibility in a South Indian population

AbstractSusceptibility to lung cancer has been shown to be modulated by inheritance of polymorphic genes encoding cytochrome P450 1A1 (CYP1A1) and glutathione S transferases (GSTM1 and GSTT1), which are involved in the bioactivation and detoxification of environmental toxins. As the incidence of lung cancer is known to differ according to ethnicity, we have conducted a case-control study of 146 South Indian lung cancer patients along with 146 healthy controls, to assess any association between CYP1A1, GSTM1 and GSTT1 polymorphisms, either separately or in combination, with the likelihood of development of lung cancer in our population. The current weight of evidence from our study indicated that the frequency of CYP1A1 MspI homozygous variant alleles was significantly higher in cases (OR=3.178). We observed a considerable difference in the GSTT1 null deletion frequency in this population when compared with other populations (OR=2.472, 95% CI: 1.191-5.094, P=0.014). There was no relative risk in GSTM1 null genotype when analysed singly (P=0.453). Considering genotype combinations, risk of lung cancer increased remarkably significantly in individuals having one variant allele of CYP1A1, GSTM1, or GSTT1, suggesting gene-gene interactions. Rare genotypic combinations (such as CYP1A1 wild GSTM1 or GSTT1 either null; CYP1A1 variant both GSTM1 and GSTT1 present; CYP1A1 variant GSTM1 or GSTT1 either null), were at higher risk compared to the reference group. Moreover, patients who had smoked <20 pack years and harboured the CYP1A1 variant allele or the GSTT1 null genotype also had a significant risk of lung cancer. Hence our study—the first to analyse a South Indian population—suggests the importance of combined CYP1A1, GSTM1 and GSTT1 polymorphisms in the development of smoking-induced lung cancer.

Germline BRCA1 mutation analysis in Indian breast/ovarian cancer families.

Most of the predisposition to hereditary breast and ovarian cancer has been attributed to inherited defects in two tumor suppressor genes BRCA1 and BRCA2. To explore the contribution of BRCA1 mutations to hereditary breast cancer among Indian women, we examined the coding sequence of the BRCA1 gene in 14 breast cancer patients with a positive family history of breast and/or ovarian cancer. Mutation analysis was carried out using conformation sensitive gel electrophoresis (CSGE) followed by sequencing. Three mutations (21%) in the BRCA1 gene were identified. Two of them are novel mutations of which one is a missense mutation in exon 7 near the RING finger domain, while the other is a one base pair deletion in exon 11 which results in protein truncation. The third mutation, 185delAG, has been previously described in Ashkenazi Jewish families. To our knowledge this is the first report of a study of germline BRCA1 mutation analysis in familial breast cancer in India. Our data from 14 different families suggests a lower prevalence but definite involvement of germline mutations in the BRCA1 gene among Indian women with breast cancer and a family history of breast cancer.

p53 Arg72Pro Polymorphism Predicts Survival Outcome in Lung Cancer Patients in Indian Population

In response to many forms of cellular stress, including DNA damage, the p53 protein functions to induce growth arrest, DNA repair, or apoptosis. Common allele variants in the TP53 gene modulate pathways of lung carcinogenesis and susceptibility to or prognosis of lung cancer. The prognostic role of the polymorphism was assessed in 422 subjects using PCR-RFLP. Logistic regression analysis showed a dominant presentation of Pro/Pro homozygotes in lung carcinoma population than in control population (OR = 2.1, P = 0.003). We further investigated the association of p53 codon 72 polymorphism with prognosis in 170 lung cancer patients. Kaplan-Meier survival analyses showed a significant difference in survival between p53 variant genotypes and overall survival (P = 0.02). Cox regression analysis showed p53 Arg72Pro heterozygous genotype was overall an independent prognostic factor (Risk ratio of death, 2.2; P = 0.02), suggesting Pro72Pro genotype to be a potential risk factor favoring the development of lung carcinoma and that Arg72Pro genotype is independently associated with a poorer prognosis of lung cancer.

The functional −94 insertion/deletion ATTG polymorphism in the promoter region of NFKB1 gene increases the risk of sporadic colorectal cancer

OBJECTIVE To investigate the allele and genotype frequencies of NFKB1 -94 ins/del ATTG (rs28720239) polymorphism and to evaluate the association between the polymorphism and colorectal cancer (CRC) risk in Malaysian population. METHODS Genomic DNA was extracted from the peripheral blood samples of 474 study subjects, which consisted of 237 histopathologically confirmed CRC patients and an equal number of cancer-free controls. The NFKB1 -94 ins/del ATTG (rs28720239) polymorphism was genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method and confirmed by DNA sequencing. The association between the polymorphic genotypes and CRC risk was evaluated by deriving odds ratios (ORs) and 95% confidence intervals (CIs) using unconditional logistic regression analysis. RESULTS The frequencies of wildtype (del/del), heterozygous (del/ins) and variant (ins/ins) genotypes in CRC patients were 31.7%, 53.6% and 14.8%, respectively, while those in cancer-free controls were 35.0%, 58.2% and 6.8%, respectively. The frequency of the variant genotype was significantly higher in cases compared to controls (P<0.01). Evaluation of the risk association of the polymorphic genotypes revealed that the variant genotype could contribute to a significantly increased risk of CRC (OR=2.42, 95% CI=1.24-4.73, P<0.01). CONCLUSIONS The variant allele of NFKB1 -94 ins/del ATTG (rs28362491) polymorphism is associated with higher risk of sporadic CRC in Malaysian population.

DNA repair proficiency : a potential marker for identification of high risk members in breast cancer families

Breast cancer is the single largest cancer and causes the high rate of cancer mortality among women. A positive family history of breast cancer is recognized as one of the major risk factors for this disease. The present study evaluates bleomycin (BLM)-induced chromosome sensitivity analysis in breast cancer families which provides indirectly a measure of the DNA repair defect of each person. BLM sensitivity assay on cultured lymphocytes of 36 familial breast cancer patients, their 85 first or second degree female relatives, 36 sporadic breast cancer patients and 40 age- and sex-matched controls (without any family history of cancer) were carried out to measure interindividual variation in their DNA repair capacity through mutagen-induced chromosome sensitivity analysis. Fifty percent of familial breast cancer patients and seven unaffected relatives showed hypersensitivity. Compared to hyposensitive relatives these seven subjects may be considered as high risk individuals.

Association of genotypes and haplotypes of multi-drug transporter genes ABCB1 and ABCG2 with clinical response to imatinib mesylate in chronic myeloid leukemia patients

The introduction and success of imatinib mesylate (IM) has become a paradigm shift in chronic myeloid leukemia (CML) treatment. However, the high efficacy of IM has been hampered by the issue of clinical resistance that might due to pharmacogenetic variability. In the current study, the contribution of three common single nucleotide polymorphisms (SNPs) of ABCB1 (T1236C, G2677T/A and C3435T) and two SNPs of ABCG2 (G34A and C421A) genes in mediating resistance and/or good response among 215 CML patients on IM therapy were investigated. Among these patients, the frequency distribution of ABCG2 421 CC, CA and AA genotypes were significantly different between IM good response and resistant groups (P=0.01). Resistance was significantly associated with patients who had homozygous ABCB1 1236 CC genotype with OR 2.79 (95%CI: 1.217-6.374, P=0.01). For ABCB1 G2677T/A polymorphism, a better complete cytogenetic remission was observed for patients with variant TT/AT/AA genotype, compared to other genotype groups (OR=0.48, 95%CI: 0.239-0.957, P=0.03). Haplotype analysis revealed that ABCB1 haplotypes (C1236G2677C3435) was statistically linked to higher risk to IM resistance (25.8% vs. 17.4%, P=0.04), while ABCG2 diplotype A34A421 was significantly correlated with IM good response (9.1% vs. 3.9%, P=0.03). In addition, genotypic variant in ABCG2 421C>A was associated with a major molecular response (MMR) (OR=2.20, 95%CI: 1.273-3.811, P=0.004), whereas ABCB1 2677G>T/A variant was associated with a significantly lower molecular response (OR=0.49, 95%CI: 0.248-0.974, P=0.04). However, there was no significant correlation of these SNPs with IM intolerance and IM induced hepatotoxicity. Our results suggest the usefulness of genotyping of these single nucleotide polymorphisms in predicting IM response among CML patients.

BCR-ABL kinase domain mutations, including 2 novel mutations in imatinib resistant Malaysian chronic myeloid leukemia patients—Frequency and clinical outcome

Discovery of imatinib mesylate (IM) as the targeted BCR-ABL protein tyrosine kinase inhibitor (TKI) has resulted in its use as the frontline therapy for chronic myeloid leukemia (CML) across the world. Although high response rates are observed in CML patients who receive IM treatment, a significant number of patients develop resistance to IM. Resistance to IM in patients has been associated with a heterogeneous array of mechanisms of which point mutations within the ABL tyrosine kinase domain (TKD) are the frequently documented. The types and frequencies of mutations reported in different population studies have shown wide variability. We screened 125 Malaysian CML patients on IM therapy who showed either TKI refractory or resistance to IM to investigate the frequency and pattern of BCR-ABL kinase domain mutations among Malaysian CML patients undergoing IM therapy and to determine the clinical significance. Mutational screening using denaturing high performance liquid chromatography (dHPLC) followed by DNA sequencing was performed on 125 IM resistant Malaysian CML patients. Mutations were detected in 28 patients (22.4%). Fifteen different types of mutations (T315I, E255K, G250E, M351T, F359C, G251E, Y253H, V289F, E355G, N368S, L387M, H369R, A397P, E355A, D276G), including 2 novel mutations were identified, with T315I as the predominant type of mutation. The data generated from clinical and molecular parameters studied were correlated with the survival of CML patients. Patients with Y253H, M351T and E355G TKD mutations showed poorer prognosis compared to those without mutation. Interestingly, when the prognostic impact of the observed mutations was compared inter-individually, E355G and Y253H mutations were associated with more adverse prognosis and shorter survival (P=0.025 and 0.005 respectively) than T315I mutation. Results suggest that apart from those mutations occurring in the three crucial regions (catalytic domain, P-loop and activation-loop), other rare mutations also may have high impact in the development of resistance and adverse prognosis. Presence of mutations in different regions of BCR-ABL TKD leads to different levels of resistance and early detection of emerging mutant clones may help in decision making for alternative treatment. Serial monitoring of BCR-ABL1 transcripts in CML patients allows appropriate selection of CML patients for BCR-ABL1 KD mutation analysis associated with acquired TKI resistance. Identification of these KD mutations is essential in order to direct alternative treatments in such CML patients.

Possible risk modification by polymorphisms of estrogen metabolizing genes in familial breast cancer susceptibility in an Indian population.

ABSTRACT This case control study investigated whether polymorphisms of estrogen metabolizing genes CYP1A1 MspI, CYP17 MspAI, COMT Val158 Met, and SULT1A1 Arg213 His have any role in familial breast cancer susceptibility risk. Logistic regression analysis adjusted to age was used to calculate odds ratios (ORs) and 95% confidence intervals (95%CIs). Familial breast cancer risk due to CYP1A1 wt/m1 and m1/m1 genotypes was 2.3 (1.51–3.61)-fold and 7.1 (3.69–13.7)-fold, respectively. In addition to the main effects, certain first-order interactions were also significantly associated with familial breast cancer. Our results favor a possible risk modification by estrogen metabolizing gene polymorphisms in familial breast cancer susceptibility.

Contribution of XPD (Lys751Gln) and XRCC1 (Arg399Gln) Polymorphisms in Familial and Sporadic Breast Cancer Predisposition and Survival: An Indian Report

The etiology of a significant proportion of familial breast cancers is still poorly understood, with known high penetrance gene mutations accounting for only a small proportion of the cases. The increased risk of breast cancer for the majority of women with a family history likely reflects shared minor low penetrant genetic factors. In the present case-control study undertaken to examine the influence of DNA damage repair gene polymorphisms in familial and sporadic breast cancer susceptibility, 219 Sporadic and 140 familial breast cancer patients and 367 controls were genotyped using PCRRFLP. Odds Ratios (ORs) and 95% Confidence Intervals (95%CIs) were calculated by unconditional logistic regression adjusted to age. Variant genotypes XRCC1 Arg/Gln or Gln/Gln and XPD Lys/Gln or Gln/Gln increased both familial and sporadic breast cancer susceptibility. However, when the intra group risk was compared, the risk due to the XPD polymorphic genotypes Lys/Gln or Gln/Gln was significantly lower among familial breast cancer patients compared to sporadic breast cancer patients [OR = 0.61; 95%CI = 0.39–0.94; p value = 0.024) whereas the risk implied by XRCC1 variant genotype was not significantly different between the familial and nonfamilial groups of breast cancer patients [OR = 0.97; 95%CI = 0.63–1.49; p value = 0.882]. Both these variant genotypes were not associated with the disease characteristics or survival of either familial or sporadic breast cancer patients. This study represents an addition to previous published work on GSTs from the same study population and substantiates the hypothesis that the impact of the low penetrance gene polymorphisms differ by family history of the disease.

Cell mediated and humoral immune responses in oral submucous fibrosis.

Cell‐mediated and humoral immune responses were assessed in 50 patients with oral submucous fibrosis (OSMF) and the results were compared with those of 50 patients with oral‐leukoplakia, 50 oral cancer patients, and 50 normal healthy adult controls. The number of high‐affinity rosette‐forming cells (HARFC) was found to be significantly decreased in OSMF and oral cancer, whereas the number of total rosette‐forming cells (TRFC) remained unaltered. Levels of serum IgA, IgD, and IgE were found to be elevated both in OSMF and oral cancer. Immunologic derangements were found to be more pronounced in oral cancer than in OSMF. The enumeration of HARFC along with the estimation of serum levels of IgA, IgD, and IgE indicates that OSMF can be an intermediary stage in the malignant transformation of a normal cell, and that these parameters may serve as markers for the early detection of oral cancer.