Caspase 8 gene variants in healthy North Indian population and comparison with worldwide ethnic group variations

BACKGROUND: Many strategies are being used for the quest for the disease causing genes. Inter-individual variations in several genes exist. Thus, even if they share the same disease-associated allele, the genomic backgrounds – and hence potential interacting alleles at other loci – of people with different regional ancestries may differ, with a consequent variation in the severity of their disease. MATERIALS AND METHOD: The present study was conducted to determine the distribution of Caspase 8 IVS12-19G/A, Caspase 8D302H, Caspase 8 -652del and Caspase 8 -678del polymorphisms (as frequency distribution of caspases in Indians generally is not yet known), which was then compared with different populations globally. Polymerase chain reaction (PCR)-based analysis was conducted in 205 normal healthy individuals of similar ethnicity. RESULTS: The variant allele frequencies were 17.6% (A) in Caspase 8 IVS12-19G/A, 13.2% (H) in Caspase 8D302H, 23.2% (Del) in Caspase 8 -652del and 24.6% (Del) in Caspase 8 -678del. Further, comparison of frequency distribution of these genes was done with various published studies of different ethnic groups globally. CONCLUSION: It is anticipated from our results that the frequency of these caspase genes exhibits distinctive patterns in India, which could perhaps be attributed to ethnic variation. This study is important as it can form a baseline for screening individuals who are at high risk due to exposure to environmental carcinogens and cancer predisposition, and therefore, might help in investigating linked polymorphisms in a way that will not obscure potential associations between genotype and phenotype.


Introduction
In the past decade, the number of publications on Resistance to apoptosis or reduced cellular apoptotic capacity provides a survival advantage of the cells that may develop into cancer cells, commonly seen in almost all types of malignant diseases, and mutations in the genes involved in apoptotic pathways are one of the molecular mechanisms underlying carcinogenesis and cancer therapy. [3][4][5] It is likely that the efficiency of these apoptotic pathways is genetically determined because functional polymorphisms in genes involved in these apoptotic pathways may modulate the phenotype, thus contributing to individual variation. In recent years, genetic variants in caspase mediated apoptosis and their role in human cancer susceptibility have been getting more and more attention, especially the apoptosis initiator caspase 8. [6] Therefore, this study was undertaken to test Caspase 8 IVS12- 19

Subjects
Healthy and genetically unrelated individuals either visiting the hospital or health awareness camps for a routine checkup, or healthy hospital employees were recruited as the controls (n = 205). All the controls were age-and sex-matched with similar ethnicity and had no evidence of malignancy or chronic disease.

DNA extraction
Five milliliters of blood was collected in ethylenediamine tetraacetic acid (EDTA) vials and DNA was extracted from blood lymphocytes using "salting out" method. [7] Genotyping All the study samples were genotyped for four SNPs in caspase genes that included  were excluded. When more than one article was identified for the same study population, we included the most recent publication. We identified two publications reporting on the prevalence of Caspase 8 IVS12-19G>A polymorphism, [6,8] four publications on Caspase 8D302H G>C, [2,9,10] three studies on Caspase 8 -652 6Ndel [11][12][13] and only one publication for Caspase 8 -678_-673del, [8] which were subsequently used for comparing with our study.

Statistical analysis
The genotype and allelic frequencies of different populations were compared by Pearson's χ 2 test, using the computer software SPSS for windows (version 11.5).
Court-Lab (web-based software) was used to examine Hardy-Weinberg equilibrium (www.tufts.edu). P value <0.05 was considered statistically significant. Table 1    The variation in our Indian population from other world population signifies the impact of ethnicity. It is well recognized that ethnic background may influence the susceptibility to certain diseases. [14] Due to the different socio-cultural traditions, Indian population is populations. [15,16] In  Son et al. (2006)

in Korean population
This suggested that gene variants were unaffected based on geographic location. Unlinked genes undergo more or less independent changes in allele frequency; this produces geographically cross-cutting allele frequency clines found among genes. [14] One way to determine what is driving health disparities is to have more focused genetic research within specific identifiable populations whose unusually high (or low) risk or population history makes them advantageous for finding susceptibility genes. [17] But this raises the potential danger that the disease might be racialized using the new genetic information. [18][19][20]  clearly that this is the typical case. [14] George and Mittal: Ethnic variations in Caspase 8 gene Son et al. [8] Therefore, our observation suggests that CASP 8 polymorphisms with their variants could be used as biomarkers for disease susceptibility and may be used for assessing the risk of cancer development. A single larger study with thousands of subjects and tissue-specific biochemical and biological characterization is warranted to further evaluate potential gene-to-gene and gene-toenvironment interactions on CASP gene polymorphisms and cancer risk. The differences in the distribution of these genes between North Indian healthy population and other ethnic groups may help in building a silhouette that would help in assessing the disease predisposition and prevalence. More emphasis is needed on evaluating polymorphisms, alone or in combinations, as modifiers of risk from relevant environmental/lifestyle exposures.