Significance of ATM Gene Polymorphisms in Chronic Myeloid Leukemia - a Case Control Study from India.

BACKGROUND: Development of chronic myeloid leukemia (CML) involves formation of double strand breaks (DSBs) which are initially sensed by the ataxia telangiectasia mutated (ATM) signal kinase to induce a DNA damage response (DDR). Mutations or single nucleotide polymorphisms in ATM gene are known to influence the signaling capacity resulting in susceptibility to certain genetic diseases such as cancers. MATERIALS AND METHODS: In the present study, we have analyzed -5144A>T (rs228589) and C4138T (rs3092856) polymorphisms of theATM gene through polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) in 925 subjects (476 CML cases and 449 controls). RESULTS: The A allele of -5144A>T polymorphism and T allele of C4138T polymorphism which were known to be influencing ATM signaling capacity are significantly associated with enhanced risk for CML independently and also in combination (evident from the haplotype and diplotype analyses). Significant elevation in the frequencies of both the risk alleles among high risk groups under European Treatment and Outcome Study (EUTOS) score suggests the possible role of these polymorphisms in predicting the prognosis of CML patients. CONCLUSIONS: This study provides the first evidence of association of functional ATM gene polymorphisms with the increased risk of CML development as well as progression.

Association of promoter polymorphisms of Fas -FasL genes with development of Chronic Myeloid Leukemia.

Chronic myeloid leukemia (CML) is a monoclonal myeloproliferative disorder of hematopoietic stem cells (HSCs), characterized by reciprocal translocation, leading to the formation of BCR-ABL oncogene with constitutive tyrosine kinase (TK) activity. This oncogene is known to deregulate different downstream pathways which ultimately lead to cell proliferation, defective DNA repair, and inhibition of apoptosis. Fas (Fas cell surface death receptor) is a member of tumor necrosis factor (TNF) superfamily which interacts with its ligand, FasL, to initiate apoptosis. Promoter polymorphisms in Fas-FasL genes are known to influence the apoptotic signaling. Hence, the present study has been aimed to find out the association of the promoter polymorphisms in Fas and FasL genes with the development and progression of CML. Blood samples from 772 subjects (386 controls and 386 cases) were collected and genotyped for Fas-FasL gene polymorphisms through PCR-RFLP method. The association between SNPs and clinical outcome was analyzed using statistical softwares like SPSS version 20, SNPSTATs, and Haploview 2.1. The study revealed a significant association of Fas -670 G>A and FasL -844 T>C polymorphisms with the development of CML while Fas -670 AG was associated with accelerated phase. Combined risk analysis by taking the risk genotypes in cases and controls revealed a significant increase in CML risk with increase in number of risk genotypes (one risk genotype-OR 1.99 (1.44-2.76), p < 0.0001; two risk genotypes-OR 3.33 (1.91-5.81), p < 0.0001). Kaplan-Meier survival analysis of Fas -670 A>G and FasL -844 T>C showed reduced event-free survival in patients carrying the variant genotypes, Fas -670 GG, 32.363 ± 6.33, and FasL -844 CC, 33.489 ± 5.83, respectively. Our findings revealed a significant association of Fas -670 GG, FasL -844 TC, and CC genotypes with increased risk of CML.

LCN2 Promoter Methylation Status as Novel Predictive Marker for Microvessel Density and Aggressive Tumor Phenotype in Breast Cancer Patients.

LCN2 (Lipocalin 2) is a 25 KD secreted acute phase protein, reported to be a novel regulator of angiogenesis in breast cancer. Up regulation of LCN2 had been observed in multiple cancers including breast cancer, pancreatic cancer and ovarian cancer. However, the role of LCN2 promoter methylation in the formation of microvessels is poorly understood. The aim of this study was to analyze the association of LCN 2 promoter methylation with microvessel formation and tumor cell proliferation in breast cancer patients. The LCN2 promoter methylation status was studied in 64 breast cancer tumors by methylation specific PCR (MSP). Evaluation of microvessel density (MVD) and Ki67 cell proliferation index was achieved by immunohistochemical staining using CD34 and MIB-1 antibodies, respectively. LCN2 promoter unmethylation status was observed in 43 (67.2%) of breast cancer patients whereas LCN2 methylation status was seen in 21 (32.8%). Further, LCN2 promoter unmethylation status was associated with aggressive tumor phenotype and elevated mean MVD in breast cancer patients.

Role of the MDM2 promoter polymorphism (-309T>G) in acute myeloid leukemia development.

BACKGROUND: The human homologue of the mouse double minute 2 (MDM2) gene is a negative regulator of Tp53. MDM2-309T>G a functional promoter polymorphism was found to be associated with overexpression thereby attenuation of Tp53 stress response and increased cancer susceptibility. We have planned to evaluate the possible role of MDM2-309T>G polymorphism with risk and response to chemotherapy in AML. MATERIALS AND METHODS: A total of 223 de novo AML cases and 304 age and sex matched healthy controls were genotyped for the MDM2-309T>G polymorphism through the tetra-primer amplification refractory mutation system (ARMS)-PCR method. In order to assess the functional relationship of -309T>G SNP with MDM2 expression level, we quantified MDM2 mRNA in 30 primary AML blood samples through quantitative RT-PCR. Both the (-309T>G) genotypes and the MDM2 expression were correlated with disease free survival (DFS) rates among patients who have achieved complete remission (CR) after first induction chemotherapy. RESULTS: MDM2-309T>G polymorphism was significantly associated with AML development (p<0.0001). The presence of either GG genotype or G allele at MDM2-309 confered 1.79 (95% CI: 1.12-2.86; p<0.001) and 1.46 fold (95%CI: 1.14-1.86; p=0.003) increased AML risk. Survival analysis revealed that CR+ve cases with GG genotype had significantly increased DFS rates (16months, p=0.05) compared to CR+ve TT (11 months) and TG (9 months) genotype groups. Further, MDM2 expression was also found to be significantly elevated in GG genotype patients (p=0.0039) and among CR+ve cases (p=0.0036). CONCLUSIONS: The MDM2-309T>G polymorphism might be involved in AML development and also serve as a good prognostic indicator.

HIF-1α (1772C>T) polymorphism as marker for breast cancer development.

Hypoxia-inducible factor 1α (HIF-1α) is an important transcription factor that regulates different cellular responses to hypoxia. HIF-1α is rapidly degraded by von Hippel-Lindau (VHL) protein under normoxic conditions and stabilized under hypoxia. A common variant of HIF-1α (1772C>T) (rs 11549465) polymorphism, corresponding to an amino acid change from proline to serine at 582 position within the oxygen-dependent degradation domain, results in increased stability of the protein and altered transactivation of its target genes. The present study was aimed to find the association between HIF-1α (1772C>T) (rs 11549465) polymorphism and breast cancer development. For this purpose, 348 primary breast cancer patients and 320 healthy and age-matched controls were genotyped through PCR-RFLP method. The genotype frequencies were compared between patients and controls, and their influence on clinical characteristics of breast cancer patients was analyzed. Our study revealed a significant increase of TT genotype in breast cancer patients compared to controls (p = 0.038). Further, TT genotype and T allele were found to be associated with progesterone receptor (PR)-negative status (p < 0.09). None of the clinical variables revealed significant association with HIF-1α (1772C>T) (rs 11549465) polymorphism.