Protein Kinase CK2 Inhibition Down Modulates the NF-κB and STAT3 Survival Pathways, Enhances the Cellular Proteotoxic Stress and Synergistically Boosts the Cytotoxic Effect of Bortezomib on Multiple Myeloma and Mantle Cell Lymphoma Cells

Abstract

CK2 is a pivotal pro-survival protein kinase in multiple myeloma that may likely impinge on bortezomib-regulated cellular pathways. In the present study, we investigated CK2 expression in multiple myeloma and mantle cell lymphoma, two bortezomib-responsive B cell tumors, as well as its involvement in bortezomib-induced cytotoxicity and signaling cascades potentially mediating bortezomib resistance. In both tumors, CK2 expression correlated with that of its activated targets NF-κB and STAT3 transcription factors. Bortezomib-induced proliferation arrest and apoptosis were significantly amplified by the simultaneous inhibition of CK2 with two inhibitors (CX-4945 and K27) in multiple myeloma and mantle cell lymphoma cell lines, in a model of multiple myeloma bone marrow microenvironment and in cells isolated from patients. CK2 inhibition empowered bortezomib-triggered mitochondrial-dependent cell death. Phosphorylation of NF-κB p65 on Ser529 (a CK2 target site) and rise of the levels of the endoplasmic reticulum stress kinase/endoribonuclease Ire1α were markedly reduced upon CK2 inhibition, as were STAT3 phospho Ser727 levels. On the contrary, CK2 inhibition increased phospho Ser51 eIF2α levels and enhanced the bortezomib-dependent accumulation of poly-ubiquitylated proteins and of the proteotoxic stress-associated chaperone Hsp70. Our data suggest that CK2 over expression in multiple myeloma and mantle cell lymphoma cells might sustain survival signaling cascades and can antagonize bortezomib-induced apoptosis at different levels. CK2 inhibitors could be useful in bortezomib-based combination therapies.

Protein kinase CK2 is widely expressed in follicular, Burkitt and diffuse large B-cell lymphomas and propels malignant B-cell growth

“…Immunohistochemical analysis confirmed that in normal lymphoid tissue (tonsil) a moderate expression of CK2α and CK2β is confined to the follicular area whereas only faint reactivity could be detected in the mantle zone (Figure S1 and 18]). Overall, 98.4% (125/127) of the NHL cases analyzed disclosed some degree of CK2 expression (Figure 1, Table 1).…”

“…Despite the pathobiological and clinical features of such lymphomas have been thoroughly investigated, prognosis and therapeutic outcomes remain highly variable and the search for novel therapeutic targets is still eagerly ongoing [29-31]. The recent development of protein kinase CK2 inhibitors as anti-cancer agents [15, 32, 33] and the evidence of CK2-expression in lymphocytes of reactive germinal centers (this paper and [18]) prompted us to investigate CK2 in a large series of FLs, DLBCLs and BLs.…”

“…Heat/EDTA-based antigen retrieval methods were applied, as previously described [18, 36]. Antigen detection was performed with the Bond Polymer Refine Detection kit in an automated immunostainer (Bond maX, Menarini, Italy) [18]. …”

“…The latter encompass B-Chronic Lymphocytic Leukemia (B-CLL) [16, 17], Mantle Cell Lymphoma (MCL) [18] and Plasma Cell Myeloma (PCM) [18, 19]. As for carcinoma cell-lines, in vitro and in vivo pre-clinical studies from our and other groups have indicated that first generation CK2 inhibitors as well as the newer CX-4945 have the potential to be novel therapeutic tools for the treatment of high CK2-expressing B cell tumors [16, 17, 20].…”

Molecular Pathways: Emergence of Protein Kinase CK2 (CSNK2) as a Potential Target to Inhibit Survival and DNA Damage Response and Repair Pathways in Cancer Cells

“…When CX-4945 was combined with GS-1101 (PI3KD inhibitor), ibrutinib (BTK inhibitor), or fludarabine, synergistic responses were observed in CLL cell lines that were not observed in the unpaired treatments with combination indices (using the Chou-Talalay method) of 0.46, 0.56, and 0.30 for CX-4945 and GS-1101, ibrutinib and fludarabine, respectively. Combinations of CX-4945 and bortezomib in in vitro assays using patient-derived cells from multiple myeloma and mantle cell lymphoma also enhanced mitochondria-dependent apoptosis associated with suppression of NFKB1 and STAT3 target genes leading to 50% reduction of NOS2 and BCL2 gene expression (42). In other in vitro cell models of cancer such as A431 epidermal carcinoma cells and H2170 lung cancer cells, combining erlotinib and CX-4945 resulted in suppression of AKT1 phosphorylation in addition to downregulation of phosphorylation sites on AKT1 and MTOR substrates (43).…”