Study of Isocitrate Dehydrogenase 1and 2 Mutations in Adult Egyptian Patients with Denovo Acute Myeloblastic Leukemia, Their Relation to Clinical Characteristics, FLT3/ITD and Nucleophosmin 1 Mutations and Impact on Treatment Outcome

Background: Acute myeloid leukaemia (AML) is a malignancy that is heterogeneous in nature characterized by genetic abnormalities some of which are established in the diagnosis and prognosis of the disease. An additional role for alterations in epigenetic mechanisms has been also highlighted in the pathogenesis of the disease. This may have a role in determining the disease outcome, impact the treatment decision and provide options for targeted therapies especially in patients who lack genetic aberrations. One of the modes of epigenetic dysregulation is mutation in genes encoding isocitrate dehydrogenase 1 and 2 that has been observed in AML with a higher incidence in patients with normal karyotype (NK).

Aim of the work: The aim of this work was to study the frequency of IDH1 (R132) and IDH2 (R140Q, R172K) mutations in adult Egyptian patients with de novo acute myeloblastic leukemia (AML), their relation with clinical characteristics, other molecular markers (the internal tandem duplication (ITD)) mutation of FLT3 gene and NPM1 gene mutation) and impact on treatment outcome.

Methods: Peripheral blood samples from 50 adult patients with denovo acute myeloid leukemia, admitted to the haematology unit at Alexandria Main University Hospital from February 2015 to February 2017, were used. The polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP) was used for detection of IDH1 codon R132 and IDH2 codons (R140, R172) mutations on genomic DNA. PCR was used for detection of FLT3-ITD mutation on genomic DNA. PCR was used for detection of NPM1 mutation on RNA.

Results: IDH 1and 2 mutations occurred in 30% of newly diagnosed AML patients and 47.6% of NK patients. Both mutations did not co-occur except in one case. IDH positive patients were significantly older than IDH negative patients (p=0.003). There was no statistically significant correlation between any of the clinical parameters and the IDH mutations. FAB-M2 was the most common FAB subtype among IDH positive patients. No correlation between IDH mutations and NPM1 or FLT3 could be demonstrated. IDH positive patients had significantly lower CR rates after induction c hemotherapy than IDH negative patients (p=0.021).

Conclusion: IDH1, 2 mutations are recurring genetic alterations in AML with a higher incidence in patients with normal karyotype and they may have an unfavorable impact on clinical outcome in adult AML patients.