Evaluation of copy number variations by array comparative genomic hybridization in patients with aml

Array based comparative genomic hybridization is a high resolution method which allows to detect unbalanced chromosomal alterations throughout the genome. We have performed an aCGH analysis for 18 patients with AML by using Nimblegen 6x630K array platform to determine advantages and disadvantages of aCGH in routine diagnostic pipeline and detect copy number alterations related to disease pathogenesis and prognosis. Patients were evaluated in 3 groups according to their karyotype results. Copy number alterations were determined in all AML patients. Although copy number gains were observed more frequently than losses, frequency of copy number losses were higher in complex karyotype group among other groups in accordance with the literature. We have observed recurrent copy gains at USP18 (n=4), AATF (n=2), CTF1 (n=2) genes in the normal karyotype group which made us think that these genes might have significant effects in the pathogenesis of AML. aCGH method was able to detect mosaicism in the abnormal karyotype group, but the sensitivity was not as high as FISH. aCGH did not detect any cryptic copy number alteration in a translocation carier patient. This may be due to the balanced rearrengement translocation or the probes may not cover the translocation region in the patient. Cyogenetic and aCGH results were not concordant in patients with complex karyotype. It might be related to the low number of subclones in composite karyotype patients. It was thought that copy losses of the NF1 (n=2) and the TP53 (n=2) genes might be responsible for the genomic instability in complex karyotype group. Several copy number alterations were detected by aCGH analysis in a patient whose karyotpe analysis revealed no metaphase spread. As a conclusion, aCGH can be utilized to detect the genes and microRNAs which affect the pathogenesis and prognosis of AML, and can also be used to evaluate patients with normal karyotype or patients without karyotype analysis