Whole Genome Association Study in Acute Myeloid Leukemia with a Normal Karyotype, Using a Single-Nucleotide Polymorphism (SNP) Analysis.

Abstract

As a result of numerous genetic aberrations, acute myeloid leukemia (AML) present with very heterogeneous clinical features. Moreover, structural and numerical chromosome aberrations currently comprise the most important basis for predicting these heterogeneous outcomes. However, 30 to 50 percent of AML patients have cytogenetically normal karyotypes. Though submicroscopic genetic alterations (such as NPM1, CEBPA, MLL-PTD) are increasingly being used for clinical purposes, additional markers with prognostic or predictive value are still lacking in this group. In this study, we performed a genome-wide, single-nucleotide polymorphism (SNP) study in order to identify novel genomic regions of interest in normal karyotype AML. 54 untreated AML patients with normal karyotypes were analyzed with an Illumina infinium 317K SNP chip assay. SNP genotype call rate was 99.8 percent, resulting in a resolution of 1 SNP/Mb. In a genome-wide SNP analysis, 317 SNP loci, having a significant difference between AML and normal control, were found. In addition, about 300 loci were also identified, showing a significant difference between patients who achieved CR and those who did not. Some of these were found to be related with drug metabolism and MDR family. Also we used the SNP assay to screen a loss of heterozygosity (LOH), suggesting possible involvement of tumor suppressor genes. In summary, 38 LOH regions larger than 1Mb were observed in 23 cases (43%) among 54 AML patients having normal karyotypes. Most (55%) of them were copy-neutral events and the most frequently identified alterations were located at 3p, 8p, 13q and 22q. 11 (29%) out of 38 LOH regions had overlapping parts among them. Some LOHs were correlated with response to chemotherapy. Various genetic changes were discovered by use of an SNP-based chip array in normal karyotype AML patients. Moreover, some of these were related with CR acquisition and drug metabolism. These results can be used to differentiate normal karyotype AML and warrant further study.