Cardiovascular diseases: Interplay of epigenetics.

Several association studies have been carried out to elucidate the role of genetic variants in cardiovascular diseases (CVDs), while studies on the epigenome regulating gene expression changes are helping to understand the development of disease and factors promoting such changes. This review summarizes the different epigenetic aspects involved in cardiac development and disease along with current therapeutic interventions.

Mitochondrial D310 instability in Asian Indian breast cancer patients.

Somatic mutations in mitochondrial DNA (mtDNA) have been demonstrated in various tumors. Mitochondrial D-loop is a non-coding region in the mitochondrial genome, which has essential transcription and replication elements, and alterations in this region may affect both these processes. The D-loop has a poly-C tract (PCT) located between 303 and 315 nucleotides known as D310, which has been identified as a frequent hot spot mutation region in human neoplasia. In the present study, 77 pairs of breast tumor and adjacent non-tumorous tissue samples were analyzed by polymerase chain reaction-single-strand conformational polymorphism, restriction fragment length polymorphism, and sequencing to evaluate the frequency of D310 (PCT) mutations and its association with clinicopathologic parameters of breast cancer. Alterations were detected in 25 of 77 (32.5 %) breast cancer samples; these included 7/25 (28 %) cases with heteroplasmy. This is the first study from Asian Indian breast cancer (BC) patients indicating a relatively high frequency of D310 mutations, suggesting that mtDNA instability at D310 may be a common characteristic of BC. However, 66.7 % of the alterations were observed in stage II BC, indicating that this may be a more important change for early progression of the disease rather than its initiation.

Evaluation of Aurora-A gene polymorphism and esophageal cancer risk in a South Indian population.

AIM: Aurora-A is a serine/threonine protein kinase that functions in centrosome maturation and spindle assembly and is involved in regulating chromosome segregation. It is amplified and overexpressed in several human cancers. The aim of the present study was to assess the role of T91A Aurora-A gene polymorphism associated with aneuploidy in human tumors. RESULT: Patients with different upper gastrointestinal tract symptoms who were referred for endoscopy were studied. They were categorized as individuals with esophageal cancer, esophagitis, and normal endoscopy based on endoscopy and histology reports. Healthy volunteers were used as controls for carrying out genomic polymerase chain reaction followed by restriction digestion. The cancer and esophagitis groups showed a higher percentage of cases with the TA genotype compared with the controls and gastrointestinal tract normal endoscopy samples. However, only esophagitis, despite a small sample size, showed a statistically significant association with the TA genotype (odds ratio=3.6082, 95% class interval=1.1276-8.8346, p=0.0411). It was also assessed if the T91A polymorphism plays a role in enhancing the effects of exogenous factors such as smoking, alcohol, tea, betel chewing, and nonvegetarian diet in esophageal pathologies. CONCLUSION: Our results indicate that the TT genotype is protective against these factors as a higher percentage of this genotype was found in individuals with normal endoscopy. This is the first study, to the best of our knowledge, carried out in an Indian population to evaluate the association of Aurora-A gene polymorphism with esophageal cancer.

Regulation of IGF2 transcript and protein expression by altered methylation in breast cancer.

PURPOSE: Breast Cancer is one of the leading causes of cancer deaths among women worldwide. The role of epigenetics as a distinct mechanism to alter gene expression in a tissue-specific manner has emerged as an important mechanism in the pathophysiology of cancer. Present study was carried out to assess the role of methylation in regulating transcription and protein expression of Insulin-like growth factor 2 (IGF2), an oncogene with parental imprinting. METHODS: Paraffin-embedded archival breast tumor and adjacent normal tissue samples were used for carrying out PCR-based methylation assay, genomic PCR, immunohistochemistry and Real-Time Reverse transcriptase PCR. RESULTS: A significant loss of methylation in exon 9 CpG cluster of IGF2 in breast tumor tissues was observed when compared to normal tissue (P < 0.0001). Expression of IGF2 by immunohistochemistry exhibited a mean twofold increase correlating with the hypomethylation of this specific CpG. Real-Time RT PCR showed increased transcripts in the tumor tissue supporting the IHC and methylation results. A total of 33% of tumor samples heterozygous for the ApaI IGF2 polymorphism exhibited biallelic IGF2 expression due to loss of imprinting; this was not seen in any of the normal breast tissues. CONCLUSIONS: Altered methylation of exonic CpG plays an important role in the enhanced transcription/expression of IGF2 in breast tumors. Methylation analysis of exon 9 CpG can be used as a biomarker for upregulation of IGF2 in breast tumor tissue and maybe developed as a diagnostic test in future.

Association of methylene tetrahydrofolate reductase C677T genotype with type 2 diabetes mellitus patients with and without renal complications.

Diabetes is gradually getting the status of a global epidemic, with India projected as the capital of type 2 diabetes mellitus (T2DM). Nephropathy is an important complication of diabetes and a major cause of end-stage renal disease. Studies from different parts of the world have given controversial results regarding the association of methylene tetrahydrofolate reductase (MTHFR) gene variation with T2DM and diabetic nephropathy (DN). This case-control study assessed the association of MTHFR C677T mutation in T2DM and DN cases. Genotyping of MTHFR was carried out for 236 T2DM cases with diabetes diagnosed for >8 years, having either normoalbuminuria (n=100) or established DN (n=136). One hundred age- and sex-matched healthy individuals with normal blood sugars and no family history of T2DM were selected as controls. This first report from India gives a highly significant odds ratio of 4.0423 (95% confidence interval=1.8753-8.7133), indicating that the MTHFR 677T allele confers a fourfold risk of developing DM in our population. The frequency of the T allele in both the DM and DN groups was similar (i.e., 0.16 and 0.11, respectively), showing no association with the initiation or progression of DN. Individuals with a family history of diabetes or with risk factors such as obesity, hypertension, and impaired glucose tolerance should be screened for MTHFR C677T mutation and may be prescribed folic acid, vitamin B6, and vitamin B12 to assess if this helps in delaying the onset of diabetes.

Assessment of genetic damage in inflammatory, precancerous, and cancerous pathologies of the esophagus using the comet assay.

The last few decades of cancer research indicate that DNA damage is a prerequisite for development of malignancies. An increase in damage points to reduced repair capacity and risk for progression. We have used the comet assay to assess DNA damage in individuals with various disorders of the upper gastrointestinal (GI) tract in a cohort of patients from South India. After thorough clinical, endoscopic, and histopathological evaluation, patients were categorized into cancers, precancers, inflammatory pathologies, and controls. Results from the comet assay performed on esophageal tissue cells and blood from the same patients showed good correlation of damage in the paired samples; subsequent assays were performed in blood. There was more DNA damage in cancers when compared with controls. A significant increase in damage in cancers (37%) and precancers (30.7%) when compared with the inflammatory pathologies (15.6%) and controls (10.03%) was noted. The interindividual variation observed was independent of confounding factors such as tobacco and alcohol. We suggest that the damage seen in the esophageal tissue is likely to be disease-related, whereas that seen in blood may be a reflection of disease. Individuals with greater damage may be prone to disease progression and the comet assay can be used as a cost-effective biomonitoring tool to assess damage and identify these individuals at risk for a progressive pathology, even to malignancy.