Purpose Gliomas are the most frequently occurring primary malignancies in the brain, and glioblastoma (GBM) is the most aggressive of these tumors. Protein kinase CK2 is composed of two catalytic subunits (α and/or α’) and two β regulatory subunits. CK2 suppresses apoptosis, promotes neo-angiogenesis, and enhances activation of the JAK/STAT, NF-κB, PI3K/AKT, Hsp90, Wnt and Hedgehog pathways. Aberrant activation of the NF-κB, PI3K/AKT and JAK/STAT-3 pathways is implicated in GBM progression. Since CK2 is involved in their activation, the expression and function of CK2 in GBM was evaluated. Experimental Design and Results Analysis of 537 GBMs from The Cancer Genome Atlas Project demonstrates the CSNK2A1 gene, encoding CK2α, has gene dosage gains in GBM (33.7%), and is significantly associated with the classical GBM subtype. Inhibition of CK2 activity by CX-4945, a selective CK2 inhibitor, or CK2 knockdown by siRNA suppresses activation of the JAK/STAT, NF-κB and AKT pathways and downstream gene expression in human GBM xenografts. On a functional level, CX-4945 treatment decreases the adhesion and migration of GBM cells, in part through inhibition of integrin β1 and α4 expression. In vivo, CX-4945 inhibits activation of STAT-3, NF-κB p65 and AKT, and promotes survival of mice with intracranial human GBM xenografts. Conclusions CK2 inhibitors may be considered for treatment of patients with GBM.

JAK-STAT signaling is involved in the regulation of cell survival, proliferation, and differentiation. JAK tyrosine kinases can be transiently activated by cytokines or growth factors in normal cells, whereas they become constitutively activated as a result of mutations that affect their function in tumors. Specifically, the JAK2V617F mutation is present in the majority of patients with myeloproliferative disorders (MPDs) and is implicated in the pathogenesis of these diseases. In the present study, we report that the kinase CK2 is a novel interaction partner of JAKs and is essential for JAK-STAT activation. We demonstrate that cytokineinduced activation of JAKs and STATs and the expression of suppressor of cytokine signaling 3 (SOCS-3), a downstream target, are inhibited by CK2 small interfering RNAs or pharmacologic inhibitors. Endogenous CK2 is associated with JAK2 and JAK1 and phosphorylates JAK2 in vitro. To extend these findings, we demonstrate that CK2 interacts with JAK2V617F and that CK2 inhibitors suppress IntroductionThe JAK-STAT pathway is crucial in transmitting signals from many cytokines and growth factors into the nucleus, regulating gene expression. Cytokines of the IL-6 family, type I and II IFNs, and growth factors such as growth hormone (GH) activate the JAK-STAT signaling pathway. Oncostatin M (OSM), a cytokine belonging to the IL-6 family, is a potent activator of the JAK-STAT signaling pathway. 1 Binding of OSM induces heterodimerization of its receptors, gp130 and OSMR␤, and the receptor-associated JAKs, JAK1 and JAK2, become activated, leading to phosphorylation of gp130 tyrosine residues. The phosphorylated residues direct the recruitment of STAT proteins, including STAT-3, STAT-1, and STAT-5, which in turn become JAK substrates. Activated tyrosinephosphorylated STATs form homodimers or heterodimers, translocate to the nucleus, and bind to consensus sequences in the promoters of OSM-responsive genes, inducing transcription. 2 The JAK tyrosine kinase family comprises 4 mammalian members: JAK1, JAK2, JAK3, and TYK2. JAK2 is essential in erythropoiesis, 3 and its dysfunction has been implicated in myeloproliferative disorders (MPDs) and leukemias. 4 MPDs are a group of clonal hematopoietic disorders including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). 4 Recent studies have revealed that JAK2V617F, a somatic, activating point mutation, occurs in most PV patients and in Ͼ 50% of ET and PMF patients, and is involved in the pathogenesis of MPDs. [5][6][7][8] Overexpression of JAK2V617F in murine Ba/F3 cells leads to cytokine-independent growth, 5 and expression of JAK2V617F in mice recapitulates many pathologic characteristics observed in PV, ET, Among the signaling pathways activated by JAK2V617F are the STATs, predominantly Therefore, JAK2V617F represents an ideal target for therapeutic intervention, especially in JAK2V617F-positive MPDs.Protein kinase CK2 (formerly known as casein kinase 2 or II) is a ubiquitous, highly conserved serine/threon...

The mechanisms by which tobacco promotes lung cancer remain incompletely understood. Herein, we report that nicotine, a major component of tobacco, promotes the proliferation of cultured non-small cell lung carcinoma (NSCLC) cells; this effect was most noticeable at 5 days. However, nicotine had no effect on apoptosis of NSCLC cells. In experiments designed to unveil the mechanisms for this effect, we found that nicotine also stimulated mRNA and protein expression of fibronectin. Fibronectin is a matrix glycoprotein that regulates important cellular processes (e.g., adhesion, proliferation, and differentiation) and is highly expressed in tobacco-related lung disorders. Of note, reagents against the integrin alpha5beta1 (antibodies, RGD peptides, alpha5 shRNA) blocked the mitogenic effects of nicotine. Thus, nicotine stimulated NSCLC cell proliferation indirectly via fibronectin induction. We then focused on the mechanisms responsible for nicotine-induced fibronectin expression in NSCLC cells and found that nicotine stimulated the surface expression of alpha7 nicotinic acetylcholine receptor (alpha7 nAChR), and that alpha-bungarotoxin, an inhibitor of alpha7 nAChR, abolished the nicotine-induced fibronectin response. The fibronectin-inducing effects of nicotine were associated with activation of extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3-K)/mammalian target of rapamycin (mTOR) signaling pathways, and were abrogated by inhibitors of ERK (PD98059), PI3-K (LY294002), and mTOR (rapamycin), but not by inhibitors of protein kinase (PK)C (calphostin C) and PKA (H89). These observations suggest that nicotine stimulates NSCLC proliferation through induction of fibronectin, and that these events are mediated through nAChR-mediated signals that include ERK and PI3-K/mTOR pathways. This work highlights the role of fibronectin and alpha5beta1 integrins as potential targets for anti-lung cancer therapies.

Aberrant activation of the Janus Kinase (JAK)/Signal Activator of Transcription (STAT) pathway has been implicated in glioblastoma (GBM) progression. To develop a therapeutic strategy to inhibit STAT-3 signaling, we have evaluated the effects of AZD1480, a pharmacological inhibitor of JAK1 and JAK2. In this study, the in vitro efficacy of AZD1480 was tested in human and murine glioma cell lines. AZD1480 treatment effectively blocks constitutive and stimulus-induced JAK1, JAK2 and STAT-3 phosphorylation in both human and murine glioma cells, and leads to a decrease in cell proliferation and induction of apoptosis. Furthermore, we utilized human xenograft GBM samples as models for the study of JAK/STAT-3 signaling in vivo, since human GBM samples propagated as xenografts in nude mice retain both the hallmark genetic alterations and the invasive phenotype seen in vivo. In these xenograft tumors, JAK2 and STAT-3 are constitutively active, but levels vary among tumors, which is consistent with the heterogeneity of GBMs. AZD1480 inhibits constitutive and stimulus-induced phosphorylation of JAK2 and STAT-3 in these GBM xenograft tumors in vitro, downstream gene expression and inhibits cell proliferation. Furthermore, AZD1480 suppresses STAT-3 activation in the glioma-initiating cell population in GBM tumors. In vivo, AZD1480 inhibits the growth of subcutaneous tumors and increases survival of mice bearing intracranial GBM tumors by inhibiting STAT-3 activity, indicating that pharmacological inhibition of the JAK/STAT-3 pathway by AZD1480 should be considered for study in the treatment of patients with GBM tumors.