High Frequency of Concurrent JAK2 V617F Mutation and BCR/ABL Fussion Gene in a Cohort (18/142) of Mexican Patients with MPD

Abstract

1766 The MPD are characterized by clonal neoplastic proliferation of one or more of the myeloid lineage in the bone marrow. The BCR/ABL fusion gene is a key genetic marker for CML an the mutation JAK2 V617F is present by over 95% of patients with PV and more than 50% of patients with ET and IMF. Both JAK2 V617F and BCR/ABL result in perturbation of tyrosine kinases and their downstream signaling pathway. The coexistence of BCR/ABL fusion gene and JAK2 V617F mutation have been described in some cases. In the differential diagnosis of MPD vs CML we performed both determinations BCR/ABL fusion gene and JAK2 V617F mutation and observed high frequency of the coexistence. Material and Methods: We performed 350 JAK2V617F and 1500 BCR-ABL PCR assays in LAOH, between January 2011 and July 2012, for the patients with suspected MPD vs CML that were sent from diferents hospitals. This cases without definitive diagnosis were maked both test and the cohort was of 142 patients. Peripheral blood or bone marrow samples were included of 56 cases with CML, 48 cases of isolated thrombocytosis, 34 cases in which total blood count disclosed elevation of ≥2 myeloid cell types and 4 cases with PV diagnosis. RNA and DNA were extracted using Trizol® reagent and Quiagen® commercial kit, the RT-PCR from b3a2/b2a2 BCR-ABL transcript was performed according to protocols standarized. For JAK2 V617F we using the allele-specific PCR method and the restiction enzyme method with BsaXI enzyme wich restriction site is present in exon 14 of JAK2. To validate the specificity of our result we sequenced the PCR products in 10 cases and two normal controls. Results. Of the 142 patients evaluated for both JAK2 V617F and BCR-ABL fusion gene, 18 patients were positive for both (12.7%). Ten with CML de novo, seven cases with ET, and one case in follow-up with imatinib. The average age of these JAK2 V617F mutation and BCR-ABL positive patients (n=18) was 63.5 (ranging from 45–82) and in patients JAK2 V617F mutation and BCR-ABL negative (n=124) were 58 years old (rank 18–85). The patient with CML in therapy with imatinib by one year, was present increase WBC; and his molecular analysis for JAK2 V617F was positive and also BCR/ABL+. The patient′s treatment regimen was modified, with initiation of hydroxyurea and imatinib; the patient achieved complete hematological response. Discussion. The others cases reports in the literature are most often a JAK2 V617F+ MPN developed in the setting of a previously diagnosed CML undergoing treatment with a tyrosine kinase inhibitor, or alternately, CML developed months to years after patients had been diagnosed with a JAK2 V617F+ MPN. In this report the most of our cases the BCR-ABL and JAK2 V617F positive cells were detected before the treatment. This studies have suggested two possibilities to account for expression of BCR-ABL and JAK2 V617F anomalies concomitant in a single patient. The first is that there are two clones each having BCR-ABL and JAK2 V617F mutation and another possibility is a single clone concurrently possesses both BCR-ABL and JAK2 V617F. It remains to be seen whether or not this patients would benefit from combined treatment with tyrosine kinase inhibitor and interferon or hydroxyurea. The clinical following up of this patients help us to response this questions. We have the highest frequency of concurrent JAK2 V617F mutation and BCR-ABL fusion gene reported, but is neccessary determined the true incidence in a greater number of patients with CML and MPD. Disclosures: No relevant conflicts of interest to declare.