casein-kinase-ii and Leukemia--Lymphocytic--Chronic--B-Cell

Despite the encouraging results of the innovative therapeutic treatments, complete remission is uncommon in patients affected by chronic lymphocytic leukaemia, which remains an essentially incurable disease. Recently, clinical trials based on BH3-mimetic drugs showed positive outcomes in subjects with poor prognostic features. However, resistance to treatments occurs in a significant number of patients. We previously reported that the multi-kinase inhibitor quercetin, a natural flavonol, restores sensitivity to ABT-737, a BH3-mimetic compound, in both leukemic cell lines and B-cells isolated from patients. To identify the molecular target of quercetin, we employed a new cell line, HG3, obtained by immortalization of B-cells from a chronic lymphocytic leukaemia patient at the later stage of disease. We confirmed that quercetin in association with ABT-737 synergistically enhances apoptosis in HG3 (combination index < 1 for all fractions affected). We also reported that the cellular uptake of quercetin is extremely rapid, with an intracellular concentration of about 38.5 ng/106 cells, after treatment with 25 μM for 5 min. We demonstrated that the activity of protein kinase CK2, which positively triggers PI3K/Akt pathway by inactivating PTEN phosphatase, is inhibited by quercetin immediately after its addition to HG3 cells (0-2 min). PI3K activity was also inhibited by quercetin within 60 min from the treatment. The combined inhibition of CK2 and PI3K kinase activities by quercetin restored ABT-737 sensitivity and increased lethality in human leukemia cells.

Topics: Antineoplastic Combined Chemotherapy Protocols; Antioxidants; Apoptosis; Biphenyl Compounds; Casein Kinase II; Cell Line, Tumor; Drug Synergism; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Piperazines; Proto-Oncogene Proteins c-akt; Quercetin; Signal Transduction; Sulfonamides

In chronic lymphocytic leukemia (CLL), STAT3 is constitutively phosphorylated on serine 727 and plays a role in the pathobiology of CLL. However, what induces constitutive phosphorylation of STAT3 is currently unknown. Mass spectrometry was used to identify casein kinase 2 (CK2), a serine/threonine kinase that coimmunoprecipitated with serine phosphorylated STAT3 (pSTAT3). Furthermore, activated CK2 incubated with recombinant STAT3 induced phosphorylation of STAT3 on serine 727. Although STAT3 and CK2 are present in normal B- and T cells, STAT3 is not constitutively phosphorylated in these cells. Further study found that CD5 and BLNK coexpressed in CLL, but not in normal B- or T cells, are required for STAT3 phosphorylation. To elucidate the relationship of CD5 and BLNK to CK2 and STAT3, STAT3 was immunoprecipitated from CLL cells, and CK2, CD5, and BLNK were detected in the immunoprecipitate. Conversely, STAT3, CD5, and BLNK were in the immunoprecipitate of CLL cells immunoprecipitated with CK2 antibodies. Furthermore, siRNA knockdown of CD5 or BLNK, or treatment with CD5-neutralizing antibodies significantly reduced the levels of serine pSTAT3 in CLL cells. Finally, confocal microscopy determined that CD5 is cell membrane bound, and fractionation studies revealed that the CK2/CD5/BLNK/STAT3 complex remains in the cytoplasm, whereas serine pSTAT3 is shuttled to the nucleus.

Topics: Adaptor Proteins, Signal Transducing; Casein Kinase II; CD5 Antigens; Cell Line, Tumor; Cell Membrane; Cell Nucleus; HeLa Cells; Humans; Jurkat Cells; K562 Cells; Leukemia, Lymphocytic, Chronic, B-Cell; Mass Spectrometry; Phosphorylation; Serine; STAT3 Transcription Factor

Topics: Alleles; Casein Kinase II; Gene Expression Regulation, Leukemic; Gene Frequency; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Mutation; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Protein Kinase Inhibitors; Protein Structure, Tertiary; Proto-Oncogene Proteins c-akt; Receptor, Notch1

Chronic lymphocytic leukemia (CLL) remains an incurable malignancy, urging for the identification of new molecular targets for therapeutic intervention. CLL cells rely on overexpression and hyperactivation of the ubiquitous serine/threonine protein kinase CK2 for their viability in vitro. CIGB-300 is a cell-permeable selective CK2 inhibitor peptide undergoing clinical trials for several cancers. Here, we show that CIGB-300 promotes activation of the tumor suppressor PTEN and abrogates PI3K-mediated downstream signaling in CLL cells. In accordance, CIGB-300 decreases the viability and proliferation of CLL cell lines, promotes apoptosis of primary leukemia cells and displays antitumor efficacy in a xenograft mouse model of human CLL. Our studies provide pre-clinical support for the testing and possible inclusion of CK2 inhibitors in the clinical arsenal against CLL.

Topics: Aged; Aged, 80 and over; Animals; Apoptosis; Casein Kinase II; Cell Growth Processes; Cell Line, Tumor; Cell Survival; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Male; Mice; Mice, Nude; Middle Aged; Peptides, Cyclic; Phosphatidylinositol 3-Kinases; Protein Kinase Inhibitors; PTEN Phosphohydrolase; Random Allocation; Signal Transduction; Xenograft Model Antitumor Assays

Topics: Adenine; Antineoplastic Agents; Casein Kinase II; Drug Synergism; Hematologic Neoplasms; Humans; Immunoglobulin G; Leukemia, Lymphocytic, Chronic, B-Cell; Naphthyridines; Phenazines; Piperidines; Prognosis; Purines; Pyrazoles; Pyrimidines; Quinazolinones; Receptors, Antigen, B-Cell; Signal Transduction; Vidarabine

Specific inhibition of signaling elements essential for the viability of B-cell chronic lymphocytic leukemia (CLL) cells offers great promise for the design of more efficient therapies. The protein serine/threonine kinase CK2 is frequently upregulated in cancer, and it is overexpressed and hyperactivated in primary CLL cells from untreated patients. We have shown that inhibition of CK2 induces apoptosis of CLL cells, whereas it does not significantly impact normal lymphocytes, demonstrating the selectivity of the CK2 inhibitors toward leukemia cells. Notably, although co-culture with OP9 stromal cells and BCR stimulation both promote leukemia cell survival in vitro, they do not prevent apoptosis of CLL cells treated with CK2 inhibitors. PI3K signaling pathway was previously shown to be essential for CLL cell viability, an observation we confirmed in all patient samples analyzed. Further, we observed that CK2 blockade decreases PTEN phosphorylation, leading to PTEN activation, and that apoptosis of CLL cells upon CK2 inhibition is mediated by PKC inactivation. This suggests that activation of PI3K/PKC signaling pathway is involved in the pro-survival effects of CK2 in CLL cells. Sensitivity to CK2 inhibition does not correlate with expression of ZAP-70 or CD38, or with IGVH mutation status. However, it positively correlates with the percentage of CLL cells in the peripheral blood, β2 microglobulin levels, and Binet clinical stage. CK2 appears to play an important role in the biology of CLL and constitutes a promising target for the development of leukemia-specific therapies.

Topics: Animals; Casein Kinase II; Cell Separation; Cell Survival; Cells, Cultured; Coculture Techniques; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Leukocytes, Mononuclear; Mice; Protein Kinase Inhibitors

Evidence suggests that tumor microenvironment is critically involved in supporting survival of chronic lymphocytic leukemia (CLL) cells. However, the molecular mechanisms of this effect and the clinical significance are not fully understood. We applied a microenvironment model to explore the interaction between CLL cells and stromal cells and to elucidate the role of phosphatidylinositol 3 kinase (PI3-K)/Akt/phosphatase and tensin homolog detected on chromosome 10 (PTEN) cascade in this process and its in vivo relevance. Primary human stromal cells from bone marrow, lymph nodes, and spleen significantly inhibited spontaneous apoptosis of CLL cells. Pan-PI3-K inhibitors (LY294002, wortmannin, PI-103), isotype-specific inhibitors of p110α, p110β, p110γ, and small interfering RNA against PI3-K and Akt1 counteracted the antiapoptotic effect of the stromal cells. Induction of apoptosis was associated with a decrease in phosphatidylinositol-3,4,5-triphosphate, PI3-K-p85, and dephosphorylation of phosphatidylinositol-dependent kinase-1 (PDK-1), Akt1, and PTEN. Freshly isolated peripheral blood mononuclear cells from patients with CLL (n = 44) showed significantly higher levels of phosphorylated Akt1, PDK-1, PTEN, and CK2 than healthy persons (n = 8). CK2 inhibitors (4,5,6,7-tetrabromo-1H-benzotriazole, apigenin, and 5,6-dichloro-1-β-D-ribofuranosylbenzimidazol) decreased phosphorylation of PTEN and Akt, induced apoptosis in CLL cells, and enhanced the response to fludarabine. In conclusion, bone marrow microenvironment modulates the PI3-K/Akt/PTEN cascade and prevents apoptosis of CLL cells. Combined inhibition of PI3-K/Akt and recovery of PTEN activity may represent a novel therapeutic concept for CLL.

Topics: Apoptosis; Bone Marrow Cells; Casein Kinase II; Cells, Cultured; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Phosphatidylinositol 3-Kinase; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Stromal Cells

Expression of protein kinase CK2 is frequently deregulated in cancer and mounting evidence implicates CK2 in tumorigenesis. Here, we show that CK2 is overexpressed and hyperactivated in chronic lymphocytic leukemia (CLL). Inhibition of CK2 induces apoptosis of CLL cells without significantly affecting normal B and T lymphocytes. Importantly, this effect is not reversed by coculture with OP9 stromal cells, which are otherwise capable of rescuing CLL cells from in vitro spontaneous apoptosis. CLL cell death upon CK2 inhibition is mediated by inactivation of PKC, a PI3K downstream target, and correlates with increased PTEN activity, indicating that CK2 promotes CLL cell survival at least in part via PI3K-dependent signaling. Although CK2 antagonists induce significant apoptosis of CLL cells in all patient samples analyzed, sensitivity to CK2 blockade positively correlates with the percentage of CLL cells in the peripheral blood, β2 microglobulin serum levels and clinical stage. These data suggest that subsets of patients with aggressive and advanced stage disease may especially benefit from therapeutic strategies targeting CK2 function. Overall, our study indicates that CK2 plays a critical role in CLL cell survival, laying the groundwork for the inclusion of CK2 inhibitors into future therapeutic strategies.

Topics: Adult; Aged; Aged, 80 and over; Apoptosis; B-Lymphocytes; Case-Control Studies; Casein Kinase II; Cell Survival; Enzyme Activation; Female; Gene Expression; Humans; In Vitro Techniques; Leukemia, Lymphocytic, Chronic, B-Cell; Male; Middle Aged; Protein Kinase Inhibitors; PTEN Phosphohydrolase; RNA, Small Interfering; T-Lymphocytes