Chronic myelogenous leukemia in patients with MPL or JAK2 mutation-positive myeloproliferative neoplasm

Co-occurrence of JAK2-V617 F mutation and BCR::ABL1 translocation in chronic myeloproliferative neoplasms: a potentially confounding genetic combination

Myeloproliferative neoplasms (MPNs) are classified into Philadelphia (Ph) chromosome-positive chronic myeloid leukemia (CML) and Ph-negative MPNs. BCR::ABL1 translocation is the key genetic event of CML, whereas JAK2/MPL/CALR mutations are molecular aberrations of Ph-negative MPNs. Despite initially considered mutually exclusive genetic aberrations, the co-occurrence of BCR::ABL1 and JAK2 has been reported in a limited number of cases. The two genetic alterations may be identified either at the same time or JAK2 aberration may be detected in patients with a previous CML treated with tyrosine kinase inhibitors or, finally, BCR::ABL1 translocation occurs in patients with a history of JAK2-positive MPN. This combination of genomic alterations is potentially confounding with clinical manifestations often misinterpreted either as disease progression or drug resistance, therefore leading to inappropriate patient's treatment. Our systematic review aims to improve hematologist and pathologist knowledge on this rare subset of patients. Starting from the presentation of two additional cases from our routine daily practice, we focus mainly on clinical, laboratory, and bone marrow histological findings, which may represent useful clues of BCR::ABL1 and JAK2 co-occurrence. The interaction between JAK2 and BCR::ABL1 clones during the disease course as well as therapy and outcome are presented.

Chronic Myeloid Leukemia: Beyond BCR-ABL1

PURPOSE OF REVIEW

In this review, we emphasize up-to-date practical cytogenetic and molecular aspects of chronic myeloid leukemia (CML) and summarize current knowledge on tyrosine kinase inhibitor (TKI) resistance and treatment response monitoring of CML.

RECENT FINDINGS

The introduction of TKIs has changed the natural course of CML and markedly improved patient survival. Over the past decades, many research efforts were devoted to elucidating the leukemogenic mechanisms of BCR-ABL1 and developing novel TKIs. More recent studies have attempted to answer new questions that have emerged in the TKI era, such as the cytogenetic and molecular bases of treatment failure and disease progression, the clinical impact of genetic aberrations in Philadelphia chromosome (Ph)-positive and Ph-negative cells, and the biological significance of Ph secondarily acquired during therapy of other hematological neoplasms. Recent progresses in the understanding of the cytogenetic and molecular mechanisms underlying therapeutic failure and disease progression have improved the risk stratification of CML and will be helpful in the design of novel therapeutic strategies.