Association of cis-Acting rs530 of the ETS2 Transcriptional Factor Gene with High-Risk Acute Myelogenous Leukemia (AML) and Allelic Expression Imbalance Assessment.

We have previously implicated ETS2 in the etiopathogenesis of acute myeloid leukemia through case-control study by revealing that polymorphisms of ETS2, a hematopoietic transcription factor gene is associated with increased risk to acute myelogenous leukemia (AML). Two SNPs out of 7 genotyped sites, rs711 and rs530 were shown to be associated with increased risk to AML with the odds ratio (OR) of 1.76 (95% C.I. 1.2–2.5, p=0.0019) for rs711 and 1.67 (95% C.I. 1.3–2.2, p=0.0003) for rs530 relative to wild type genotypes respectively. Haplotype and linkage disequilibrium (LD) map was estimated, but haplotype association was not found with statistical significance. Korean LD structure was similar to Japanese LD, but least similarity was shown with LDs from African (Yoruba in Ibadan, Nigeria). Since these two SNPs are located in the 3′ UTR region we simulated the change in secondary structure in silico of the 3′ UTR region with two variants introduced in the sequence. Most dramatic change in the secondary structure was observed in the rs530 containing domain suggesting this variant of being cis-acting genetic variant. Real time Q-PCR and western blot analysis showed that expression of ETS2 decreased in individuals with heterozygous or mutant homozygous genotypes, showing most abundant expression with two wild type copies of rs530, less expression with the rare homozygous or heterozygous genotype. Sequencing cDNA of 55 heterozygous AML patients revealed mRNA expression imbalance in 13 cases (24%) effectively reverting heterozygous genotype to homozygous wild type mRNA species. The detection of a discrepancy between the mRNA alleles of rs530 clearly proves cis-acting effect of rs530. However there was not a case in 51 healthy control samples suggesting differing transcript levels derived from the two alleles of an autosomal gene is disease-specific phenomena. Taken together, our results suggest that two polymorphic variants in the 3′ UTR region predispose individual to high-risk AML by inducing change in mRNA expression as a cis-acting variant.