Genetic variations at microRNA and processing genes and risk of oral cancer.

Genetic variations at microRNA and microRNA processing genes are known to confer risk of cancer in different populations. Here, we studied variations at eight microRNA (miRNA) and four miRNA processing genes in 452 controls and 451 oral cancer patients by TaqMan genotyping assays. Variant allele-containing genotypes at mir-196a2 and variant allele homozygous genotype at Ran increased the risk of cancer significantly [adjusted odds ratio (OR) (95% confidence interval (CI)) = 1.3 (1-1.7) and 2.3 (1.1-4.6), respectively]. Conversely, variant allele-containing genotypes at mir-34b and variant allele homozygous genotype at Gemin3 reduced the risk of cancer significantly [adjusted OR (95% CI) = 0.7 (0.5-0.9) and 0.6 (0.4-1), respectively]. Cumulative risk was also increased by three times with increase in the number of risk alleles at these four loci. In tobacco stratified analysis, variant allele homozygous genotypes at mir-29a and Ran increased [adjusted OR (95% CI) = 1.5 (1-2.3) and 3 (1.1-8.4) respectively], while variant allele-containing genotypes at mir-34b decreased [adjusted OR (95% CI) = 0.6 (0.4-0.9)] the risk of cancer significantly. Thus, genetic variation at miRNA and processing genes altered the risk of oral cancer in this population thereby corroborating studies in other populations. However, it is necessary to validate this result in different Indian sub populations with larger sample sizes and examine the effect of these variations in tumour tissues to explain the mechanism of risk alteration.