CK2 Activity Mediates the Aggressive Molecular Signature of Glioblastoma Multiforme by Inducing Nerve/Glial Antigen (NG)2 Expression

A comprehensive review on the dynamics of protein kinase CK2 in cancer development and optimizing therapeutic strategies

Protein kinase 2 (CK2) is an enzyme ubiquitously present and exhibits extensive kinase activity. It has been strongly linked to tumor progression through the abnormal phosphorylation of key proteins. Research has consistently demonstrated that CK2 is deregulated in various cancer types, with enhanced protein expression and nuclear distribution in tumor cells. CK2 plays a crucial role in a complex network that promotes cell infiltration, migration, proliferation, apoptosis, and cancer progression through multiple pathways, including PI3K/AKT, JAK2/STAT3, ATF4/CDKN1, and HSP90/Cdc37. In addition to its role in cancer growth, there is mounting evidence that CK2 may also affect the immunological dynamics of cancer by altering immune cell functions within the tumor microenvironment, thus facilitating tumor immune evasion. Recent research has increasingly focused on CK2, recognizing it as a therapeutic objective for oncological interventions. This review will critically examine the structure and signaling pathways of CK2, highlighting the significance of further research aimed at enhancing our understanding of the CK2 machinery. Finally, we conclude by refining therapeutic options, notably transitioning from non-pharmacological techniques to strategic CK2 inhibitor use. This development shortens the path to the desired outcome, establishing a pioneering standard in cancer therapy.

Emerging Therapies for Glioblastoma

Glioblastoma is most commonly a primary brain tumor and the utmost malignant one, with a survival rate of approximately 12-18 months. Glioblastoma is highly heterogeneous, demonstrating that different types of cells from the same tumor can manifest distinct gene expression patterns and biological behaviors. Conventional therapies such as temozolomide, radiation, and surgery have limitations. As of now, there is no cure for glioblastoma. Alternative treatment methods to eradicate glioblastoma are discussed in this review, including targeted therapies to PI3K, NFKβ, JAK-STAT, CK2, WNT, NOTCH, Hedgehog, and TGFβ pathways. The highly novel application of oncolytic viruses and nanomaterials in combating glioblastoma are also discussed. Despite scores of clinical trials for glioblastoma, the prognosis remains poor. Progress in breaching the blood-brain barrier with nanomaterials and novel avenues for targeted and combination treatments hold promise for the future development of efficacious glioblastoma therapies.

C-Myc/H19/miR-29b axis downregulates nerve/glial (NG)2 expression in glioblastoma multiforme

Nerve/glial antigen (NG)2 is highly expressed in glioblastoma multiforme (GBM). However, the underlying mechanisms of its upregulated expression are largely unknown. In silico analyses reveal that the tumor-suppressive miR-29b targets NG2. We used GBM-based data from The Cancer Genome Atals databases to analyze the expression pattern of miR-29b and different target genes, including NG2. Moreover, we investigated the regulatory function of miR-29b on NG2 expression and NG2-related signaling pathways. We further studied upstream mechanisms affecting miR-29b-dependent NG2 expression. We found that miR-29b downregulates NG2 expression directly and indirectly via the transcription factor Sp1. Furthermore, we identified the NG2 coreceptor platelet-derived growth factor receptor (PDGFR)α as an additional miR-29b target. As shown by a panel of functional cell assays, a reduced miR-29b-dependent NG2 expression suppresses tumor cell proliferation and migration. Signaling pathway analyses revealed that this is associated with a decreased ERK1/2 activity. In addition, we found that the long noncoding RNA H19 and c-Myc act as upstream repressors of miR-29b in GBM cells, resulting in an increased NG2 expression. These findings indicate that the c-Myc/H19/miR-29b axis crucially regulates NG2 expression in GBM and, thus, represents a target for the development of future GBM therapies.

CX-4945 inhibits fibroblast-like synoviocytes functions through the CK2-p53 axis to reduce rheumatoid arthritis disease severity

Fibroblast-like synoviocytes (FLS) mediate many pathological processes in rheumatoid arthritis (RA), including pannus formation, bone erosion, and inflammation. RA FLS have unique aggressive phenotypes and exhibit several tumor cell-like characteristics, including hyperproliferation, excessive migration and invasion. Casein kinase 2 (CK2) is reportedly overexpressed in numerous tumor types, and targeted inhibition of CK2 has therapeutic benefits for tumors. However, the expression level of CK2 and its functions in RA FLS remain unclear. Herein, we aimed to elucidate whether CK2 is responsible for the aggressive phenotypes of RA FLS and whether targeted therapy can alleviate the severity of RA. We found that CK2 subunits were elevated in RA FLS compared with osteoarthritis FLS, and the activity of CK2 also markedly increased in RA FLS. Targeted inhibition of CK2 using CX-4945 suppressed RA FLS proliferation through cell cycle arrest. Cell migration and invasion were also inhibited by CX-4945 treatment. Moreover, CX-4945 reduced Interleukin-6 (IL-6), CC motif chemokine ligand 2 (CCL2) and Matrix metalloproteinase-3 (MMP-3) secretion in RA FLS. Further proteomic investigation revealed that p53 signaling pathway significantly changes after CX-4945 treatment in RA FLS. The siRNA-mediated p53 knockdown partly abolished the anti-proliferation and reduced IL-6, MMP-3 secretion effects of CX-4945. Furthermore, CX-4945 administration alleviates arthritis severity in CIA mice. Collectively, our results demonstrated the abnormal elevation of CK2 and its positive association with abnormal phenotypes in RA FLS. Our novel findings suggest the possible therapeutic potential of CX-4945 for RA.

Analysis of the phosphoproteome of CK2α(-/-)/Δα' C2C12 myoblasts compared to the wild-type cells

CK2 is a Ser/Thr protein kinase composed of two catalytic (α/α') subunits and a non-catalytic β-subunit dimer, whose activity is often abnormally high in cancer cells. The concept that CK2 may be dispensable for cell survival has been challenged by the finding that viable CK2α/α' knock-out myoblast clones still express small amounts of an N-terminally deleted α' subunit generated during the CRISPR/Cas9 procedure. Here we show that, although the overall CK2 activity of these CK2α^(-/-)/Δα' (KO) cells is less than 10% compared to wild-type (WT) cells, the number of phosphosites with the CK2 consensus is comparable to that of WT cells. A more in-depth analysis, however, reveals that the two phosphoproteomes are not superimposable according to a number of criteria, notably a functional analysis of the phosphoproteome found in the two types of cells, and variable sensitivity of the phosphosites to two structurally unrelated CK2 inhibitors. These data support the idea that a minimal CK2 activity, as in KO cells, is sufficient to perform basic housekeeping functions essential for cell survival, but not to accomplish several specialized tasks required upon cell differentiation and transformation. From this standpoint, a controlled downregulation of CK2 would represent a safe and valuable anti-cancer strategy.

Integrated Analysis of Multiomics Data Identified Molecular Subtypes and Oxidative Stress-Related Prognostic Biomarkers in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is a glioma in IV stage, which is one of the most common primary malignant brain tumors in adults. GBM has the characters of high invasiveness, high recurrence rate, and low survival rate and with a poor prognosis. GBM implicates various genetic changes and epigenetic and gene transcription disorders, which are crucial in developing GBM. With the progression and enhancement of high-throughput sequencing technologies, the acquirement and administering approaches of diverse biological omics data on distinctive levels are developing more advanced. However, the research of GBM with multiomics remains largely unknown. We identified GBM-related molecular subtypes by integrated multiomics data and exploring the connections of gene copy number variation (CNV) and methylation gene (MET) change data. The expression of CNV and MET genes was examined through cluster integration analysis. The present study confirmed three clusters (iC1, iC2, and iC3) with distinctive prognosis and molecule peculiarities. We also recognized three oxidative stress protecting molecules (OSMR, IGFBP6, and MYBPH) by contrasting gene expression, MET, and CNV in the three subtypes. OSMR, IGFBP6, and MYBPH were differentially expressed in the clusters, suggesting they might be recognized as characteristic markers for the three clusters in GBM. Through integrative investigation of genomics, epigenomics, and transcriptomics, we offer novel visions into the multilayered molecules of GBM and facilitate the accuracy remedy for GBM sufferers.

CK2β Is a Gatekeeper of Focal Adhesions Regulating Cell Spreading

CK2 is a hetero-tetrameric serine/threonine protein kinase made up of two CK2α/αʹ catalytic subunits and two CK2β regulatory subunits. The free CK2α subunit and the tetrameric holoenzyme have distinct substrate specificity profiles, suggesting that the spatiotemporal organization of the individual CK2 subunits observed in living cells is crucial in the control of the many cellular processes that are governed by this pleiotropic kinase. Indeed, previous studies reported that the unbalanced expression of CK2 subunits is sufficient to drive epithelial to mesenchymal transition (EMT), a process involved in cancer invasion and metastasis. Moreover, sub-stoichiometric expression of CK2β compared to CK2α in a subset of breast cancer tumors was correlated with the induction of EMT markers and increased epithelial cell plasticity in breast carcinoma progression. Phenotypic changes of epithelial cells are often associated with the activation of phosphotyrosine signaling. Herein, using phosphotyrosine enrichment coupled with affinity capture and proteomic analysis, we show that decreased expression of CK2β in MCF10A mammary epithelial cells triggers the phosphorylation of a number of proteins on tyrosine residues and promotes the striking activation of the FAK1-Src-PAX1 signaling pathway. Moreover, morphometric analyses also reveal that CK2β loss increases the number and the spatial distribution of focal adhesion signaling complexes that coordinate the adhesive and migratory processes. Together, our findings allow positioning CK2β as a gatekeeper for cell spreading by restraining focal adhesion formation and invasion of mammary epithelial cells.

Inhibition of CK2 Reduces NG2 Expression in Juvenile Angiofibroma

Juvenile angiofibroma (JA) is a rare fibrovascular neoplasm predominately found within the posterior nasal cavity of adolescent males. JA expresses the proteoglycan nerve–glial antigen (NG)2, which crucially determines the migratory capacity of distinct cancer cells. Moreover, it is known that the protein kinase CK2 regulates NG2 gene expression. Therefore, in the present study, we analyzed whether the inhibition of CK2 suppresses NG2-dependent JA cell proliferation and migration. For this purpose, we assessed the expression of NG2 and CK2 in patient-derived JA tissue samples, as well as in patient-derived JA cell cultures by Western blot, immunohistochemistry, flow cytometry and quantitative real-time PCR. The mitochondrial activity, proliferation and migratory capacity of the JA cells were determined by water-soluble tetrazolium (WST)-1, 5-bromo-2′-deoxyuridine (BrdU) and collagen sprouting assays. We found that NG2 and CK2 were expressed in both the JA tissue samples and cell cultures. The treatment of the JA cells with the two CK2 inhibitors, CX-4945 and SGC-CK2-1, significantly reduced NG2 gene and protein expression when compared to the vehicle-treated cells. In addition, the loss of CK2 activity suppressed the JA cell proliferation and migration. These findings indicate that the inhibition of CK2 may represent a promising therapeutic approach for the treatment of NG2-expressing JA.

4,5,7-Trisubstituted indeno[1,2-b]indole inhibits CK2 activity in tumor cells equivalent to CX-4945 and shows strong anti-migratory effects

Highly pleiotropic and constitutively active protein kinase CK2 is a key target in cancer therapy, but only one small-molecule inhibitor has reached clinical trials-CX-4945. In this study, we present the indeno[1,2-b]indole derivative 5-isopropyl-4-methoxy-7-methyl-5,6,7,8-tetrahydroindeno[1,2-b]indole-9,10-dione (5a-2) that decreased the intracellular CK2 activity in A431, A549, and LNCaP tumor cell lines analogous to CX-4945 (> 75% inhibition at 20 µm) and similarly blocked CK2-specific Akt phosphorylation in LNCaP cells. Cellular uptake analysis demonstrated higher intracellular concentrations of 5a-2 (408.3 nm) compared with CX-4945 (119.3 nm). This finding clarifies the comparable effects of both compounds on the intracellular CK2 activity despite their different inhibitory potency in vitro [IC₅₀  = 25 nm (5a-2) and 3.7 nm (CX-4945)]. Examination of the effects of both CK2 inhibitors on cancer cells using live-cell imaging revealed notable differences. Whereas CX-4945 showed a stronger pro-apoptotic effect on tumor cells, 5a-2 was more effective in inhibiting tumor cell migration. Our results showed that 49% of intracellular CX-4945 was localized in the nuclear fraction, whereas 71% of 5a-2 was detectable in the cytoplasm. The different subcellular distribution, and thus the site of CK2 inhibition, provides a possible explanation for the different cellular effects. Our study indicates that investigating CK2 inhibition-mediated cellular effects in relation to the subcellular sites of CK2 inhibition may help to improve our understanding of the preferential roles of CK2 within different cancer cell compartments.

Novel Treatment Strategies for Glioblastoma-A Summary

Glioblastoma (GBM) is the most common primary central nervous system tumor in adults, accounting for approximately 80% of all brain-related malignancies [...].

Targeting CK2 in cancer: a valuable strategy or a waste of time?

CK2 is a protein kinase involved in several human diseases (ranging from neurological and cardiovascular diseases to autoimmune disorders, diabetes, and infections, including COVID-19), but its best-known implications are in cancer, where it is considered a pharmacological target. Several CK2 inhibitors are available and clinical trials are underway in different cancer types. Recently, the suitability of CK2 as a broad anticancer target has been questioned by the finding that a newly developed compound, named SGC-CK2-1, which is more selective than any other known CK2 inhibitor, is poorly effective in reducing cell growth in different cancer lines, prompting the conclusion that the anticancer efficacy of CX-4945, the commonly used clinical-grade CK2 inhibitor, is to be attributed to its off-target effects. Here we perform a detailed scrutiny of published studies on CK2 targeting and a more in-depth analysis of the available data on SGC-CK2-1 vs. CX-4945 efficacy, providing a different perspective about the actual reliance of cancer cells on CK2. Collectively taken, our arguments would indicate that the pretended dispensability of CK2 in cancer is far from having been proved and warn against premature conclusions, which could discourage ongoing investigations on a potentially valuable drug target.

HMGA1, Moonlighting Protein Function, and Cellular Real Estate: Location, Location, Location!

The gene encoding the High Mobility Group A1 (HMGA1) chromatin remodeling protein is upregulated in diverse cancers where high levels portend adverse clinical outcomes. Until recently, HMGA1 was assumed to be a nuclear protein exerting its role in cancer by transcriptionally modulating gene expression and downstream signaling pathways. However, the discovery of an extracellular HMGA1-RAGE autocrine loop in invasive triple-negative breast cancer (TNBC) cell lines implicates HMGA1 as a "moonlighting protein" with different functions depending upon cellular location. Here, we review the role of HMGA1, not only as a chromatin regulator in cancer and stem cells, but also as a potential secreted factor that drives tumor progression. Prior work found that HMGA1 is secreted from TNBC cell lines where it signals through the receptor for advanced glycation end products (RAGE) to foster phenotypes involved in tumor invasion and metastatic progression. Studies in primary TNBC tumors also suggest that HMGA1 secretion associates with distant metastasis in TNBC. Given the therapeutic potential to target extracellular proteins, further work to confirm this role in other contexts is warranted. Indeed, crosstalk between nuclear and secreted HMGA1 could change our understanding of tumor development and reveal novel therapeutic opportunities relevant to diverse human cancers overexpressing HMGA1.