Heritable Polymorphism Predisposes To High Expression Of Baalc In Cytogenetically Normal Acute Myeloid Leukemia (Cn-Aml)

Introduction: Risk-adapted therapy of AML patients (pts) is presently based on cytogenetic and molecular findings. However, the outcome remains poor for the majority of pts. Overexpression of BAALC is implicated in leukemogenesis and poor survival of CN-AML pts, but the underlying mechanisms are unknown. We hypothesized that the elevated expression of BAALC might result from a genetic variant in or close to the gene (in cis). Methods and Results: BAALC and RUNX1 expression were measured in pre-therapy samples from a test set of 253 CN-AML pts (Cancer And Leukemia Group B) using Affymetrix U133 plus 2.0 arrays. Pts were grouped as high or low BAALC and high or low RUNX1 expressers using the median expression value as the cut-off and screened for single nucleotide polymorphisms (SNPs) by direct sequencing of the BAALC gene. Nine informative SNPs were identified. By genotyping, marker rs62527607, a non-coding SNP in the promoter region correlated with high BAALC expression (rs62527607G>T: genotypes TT/GT vs. GG: P=2.01E-04). Luciferase reporter constructs (pGL4.11) spanning the respective alleles demonstrated that the T allele (“risk allele”) of rs62527607 increased luciferase activity compared to the G allele (P=1.0E-02). The T allele of rs62527607 is predicted to create a binding site for the transcription factor RUNX1. Indeed, RUNX1-cotransfection showed an increase in luciferase activity for the T allele of rs62527607 (P=2.0E-02) but not for the G allele (P=2.7E-01). An Electrophoretic Mobility Shift Assay comparing the binding activity of the two alleles showed highly increased binding activity of RUNX1 to the T allele vs. the G allele. Testing of the pt samples for a potential correlation of RUNX1 and BAALC expression levels revealed a positive correlation in pts with genotypes TT/GT but not GG when restricting the analysis to the high RUNX1 expressing group (P=1.18E-04). For validation of our findings, a set of 105 CN-AML pts comprising 52 high and 53 low BAALC expressers (AML Study Group [AMLSG], quantitative Real-Time PCR [qPCR]) was genotyped for rs62527607, determined for RUNX1 expresser status (qPCR) and analyzed alone and in combination with the test set. A non-significant association of TT/GT vs. GG with high BAALC expression (31% vs. 19%; P=1.6E-01) was seen. Analyzing both sets combined resulted in a P-value of 9.3E-05 (Odds Ratio [OR]=2.59 [1.62, 4.22; 95%CI]). Combining the results of the CALGB & AMLSG series showed a highly significant association between RUNX1 and BAALC expression in pts with genotypes TT/GT belonging to the high RUNX1 expressing group (P=7.97E-05, OR=4.02 [2.05, 8.21; 95%CI]). Conclusion: We show that the risk allele of rs62527607 creates a RUNX1 binding site, thereby leading to increased transcription of BAALC. The observation that a heritable trait is involved in the leukemogenesis process might initiate a new era of personalized medicine in AML. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1307. doi:1538-7445.AM2012-1307