Contemporary insights into the pathogenesis and treatment of chronic myeloproliferative neoplasms

Diagnostic and Therapeutic Implications of Long Non-Coding RNAs in Leukemia

Leukemia is a heterogenous group of hematological malignancies categorized in four main types (acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL). Several cytogenetic and molecular markers have become a part of routine analysis for leukemia patients. These markers have been used in diagnosis, risk-stratification and targeted therapy application. Recent studies have indicated that numerous regulatory RNAs, such as long non-coding RNAs (lncRNAs), have a role in tumor initiation and progression. When it comes to leukemia, data for lncRNA involvement in its etiology, progression, diagnosis, treatment and prognosis is limited. The aim of this review is to summarize research data on lncRNAs in different types of leukemia, on their expression pattern, their role in leukemic transformation and disease progression. The usefulness of this information in the clinical setting, i.e., for diagnostic and prognostic purposes, will be emphasized. Finally, how particular lncRNAs could be used as potential targets for the application of targeted therapy will be considered.

The Classification of Myeloproliferative Neoplasms: Rationale, Historical Background and Future Perspectives with Focus on Unclassifiable Cases

Myeloproliferative neoplasms (MPNs) are a heterogeneous group of clonal hematopoietic stem cell disorders, characterized by increased proliferation of one or more myeloid lineages in the bone marrow. The classification and diagnostic criteria of MPNs have undergone relevant changes over the years, reflecting the increased awareness on these conditions and a better understanding of their biological and clinical-pathological features. The current World Health Organization (WHO) Classification acknowledges four main sub-groups of MPNs: (i) Chronic Myeloid Leukemia; (ii) classical Philadelphia-negative MPNs (Polycythemia Vera; Essential Thrombocythemia; Primary Myelofibrosis); (iii) non-classical Philadelphia-negative MPNs (Chronic Neutrophilic Leukemia; Chronic Eosinophilic Leukemia); and (iv) MPNs, unclassifiable (MPN-U). The latter are currently defined as MPNs with clinical-pathological findings not fulfilling the diagnostic criteria for any other entity. The MPN-U spectrum traditionally encompasses early phase MPNs, terminal (i.e., advanced fibrotic) MPNs, and cases associated with inflammatory or neoplastic disorders that obscure the clinical-histological picture. Several lines of evidence and clinical practice suggest the existence of additional myeloid neoplasms that may expand the spectrum of MPN-U. To gain insight into such disorders, this review addresses the history of MPN classification, the evolution of their diagnostic criteria and the complex clinical-pathological and biological features of MPN-U.

Hydroxyurea-induced senescent peripheral blood mesenchymal stromal cells inhibit bystander cell proliferation of JAK2V617F-positive human erythroleukemia cells

Hydroxyurea (HU) is a nonalkylating antineoplastic agent used in the treatment of hematological malignancies. HU is a DNA replication stress inducer, and as such, it may induce a premature senescence-like cell phenotype; however, its repercussion on bystander cell proliferation has not been revealed so far. Our results indicate that HU strongly inhibited peripheral blood mesenchymal stromal cells (PBMSC) proliferation by cell cycle arrest in S phase, and that, consequently, PBMSC acquire senescence-related phenotypical changes. HU-treated PBMSC display increased senescence-associated β-galactosidase levels and p16^INK4 expression, as well as DNA damage response and genotoxic effects, evidenced by expression of γH2A.X and micronuclei. Moreover, HU-induced PBMSC senescence is mediated by increased reactive oxygen species (ROS) levels, as demonstrated by the inhibition of senescence markers in the presence of ROS scavenger N-acetylcysteine and NADPH oxidase inhibitor Apocynin. To determine the HU-induced bystander effect, we used the JAK2V617F-positive human erythroleukemia 92.1.7 (HEL) cells. Co-culture with HU-induced senescent PBMSC (HU-S-PBMSC) strongly inhibited bystander HEL cell proliferation, and this effect is mediated by both ROS and transforming growth factor (TGF)-β expression. Besides induction of premature senescence, HU educates PBMSC toward an inhibitory phenotype of HEL cell proliferation. Finally, our study contributes to the understanding of the role of HU-induced PBMSC senescence as a potential adjuvant in hematological malignancy therapies.

Proteomic analysis of JAK2V617F-induced changes identifies potential new combinatorial therapeutic approaches

In excess of 90% of patients with polycythaemia vera (PV) express a mutated form of Janus kinase 2 (JAK2), JAK2V617F. Such aberrant proteins offer great potential for the treatment of these diseases; however, inhibitors to JAK2 have had limited success in the clinic in terms of curing the disease. To understand the effects of this oncogene in haematopoietic cells with the aim of improving treatment strategies, we undertook a systematic evaluation of the effects of JAK2V617F expression using proteomics. The effects of JAK2V617F on over 5000 proteins and 2000 nuclear phosphopeptide sites were relatively quantified using either SILAC or eight-channel iTRAQ mass spectrometry. Pathway analysis of the proteins identified as changing indicated disruption to the p53 and MYC signalling pathways. These changes were confirmed using orthogonal approaches. The insight gained from this proteomic analysis led to the formation of hypothesis-driven analysis on inhibitor-mediated effects on primary cells from patients with a JAK2V617F mutation. Simultaneous inhibition of MYC and upregulation of p53 led to the preferential extinction of JAK2V617F-positive CD34+ cells, illustrating a potential therapeutic benefit from combined targeting of p53 and MYC.