In the presented study we analysed the effect of histone deacetylase inhibitors (HDACi) suberoylanilide hydroxamic acid (SAHA) and valproic acid (VPA) on human plasma cell leukemia (PCL) cell line UHKT-944 in the presence of bone marrow microenvironment (BMM). For the analysis, the cells were cultured alone, with bone marrow stromal cells (BMSCs), with extracellular matrix (ECM) components or with interleukin-6, and treated with varied concentrations of SAHA and VPA for 24/48 hours. To study the effect of HDACi, we investigated cell proliferation, apoptosis, cell cycle and changes in selected signalling pathways. We found that both SAHA and VPA induced apoptosis, but had no effect on the cell cycle distribution of UHKT-944 cells. Investigation of the antiproliferative effect of SAHA and VPA revealed that BMSCs and high concentration of interleukin-6 had partial protective effect against SAHA or both inhibitors, respectively. No effect of ECM components on the efficiency of HDACi was observed. We further revealed that VPA down-regulated STAT3 phosphorylation while both inhibitors decreased Akt phosphorylation. In conclusion, VPA and SAHA might represent an additional therapeutic strategy in the PCL treatment. Protective effect of BMM should be taken into account when investigating prospective therapeutic agents against plasma cell disorders.

Chronic myelogenous leukemia (CML) is a myeloproliferative disease characterized by the BCR-ABL oncogene. Despite the high performance of treatment with tyrosine kinase inhibitors (TKI), about 30% of patients develop resistance to the therapy. To improve the outcomes, identification of new targets of treatment is needed. Here, we explored the Casein Kinase 2 (CK2) as a potential target for CML therapy. Previously, we detected increased phosphorylation of HSP90β Serine 226 in patients non-responding to TKIs imatinib and dasatinib. This site is known to be phosphorylated by CK2, which was also linked to CML resistance to imatinib. In the present work, we established six novel imatinib- and dasatinib-resistant CML cell lines, all of which had increased CK2 activation. A CK2 inhibitor, CX-4945, induced cell death of CML cells in both parental and resistant cell lines. In some cases, CK2 inhibition also potentiated the effects of TKI on the cell metabolic activity. No effects of CK2 inhibition were observed in normal mononuclear blood cells from healthy donors and BCR-ABL negative HL60 cell line. Our data indicate that CK2 kinase supports CML cell viability even in cells with different mechanisms of resistance to TKI, and thus represents a potential target for treatment.

0.0002), suggesting that telomeres are not age-dependent in CML at diagnosis. Analysing the clinical data, no significant correlation between ∆TL and clinical prognostic scores (Sokal and ELTS, with p = 0.816 and p = 0.314, respectively) was observed, nor between ∆TL and p210 BCR-ABL1 onco-protein isoforms (e13a2 and e14a2, p = 0.981). Finally, focusing on the ∆TL representing the difference between TL expected by age and TL determined in the CML cells, patients with lower ∆TL at diagnosis were significant associated with achievement of MR4.0 and MR4.

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