Article

Inhibition of CK2α down-regulates Hedgehog/Gli signaling leading to a reduction of a stem-like side population in human lung cancer cells.

Thoracic Oncology Laboratory, Department of Surgery, Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, California, United States of America.
PLoS ONE (Impact Factor: 3.53). 06/2012; 7(6):e38996. DOI: 10.1371/journal.pone.0038996
Source: PubMed

ABSTRACT Protein kinase CK2 is frequently elevated in a variety of human cancers. The Hedgehog (Hh) signaling pathway has been implicated in stem cell maintenance, and its aberrant activation has been indicated in several types of cancer, including lung cancer. In this study, we show that CK2 is positively involved in Hh/Gli signaling in lung cancer cell lines A549 and H1299. First, we found a correlation between CK2α and Gli1 mRNA levels in 100 primary lung cancer tissues. Down-regulation of Gli1 expression and transcriptional activity were demonstrated after the silencing of CK2α in lung cancer cells. In addition, CK2α siRNA down-regulated the expression of Hh target genes. Furthermore, two small-molecule CK2α inhibitors led to a dose-dependent inhibition of Gli1 expression and transcriptional activity in lung cancer cells. Reversely, forced over-expression of CK2α resulted in an increase both in Gli1 expression and transcriptional activity in A549 cells. Finally, the inhibition of Hh/Gli by CK2α siRNA led to a reduction of a cancer stem cell-like side population that shows higher ABCG2 expression level. Thus, we report that the inhibition of CK2α down-regulates Hh/Gli signaling and subsequently reduces stem-like side population in human lung cancer cells.

1 Bookmark
 · 
216 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Casein kinase 2 (CK2) is an oncogenic protein kinase which contributes to tumor development, proliferation, and suppression of apoptosis in multiple cancer types. The mechanism by which CK2 expression and activity leads to tumorigenesis in glioblastoma (GBM), a stage IV primary brain tumor, is being studied. Recent studies demonstrate that CK2 plays an important role in GBM formation and growth through the inhibition of tumor suppressors and activation of oncogenes. In addition, intriguing new reports indicate that CK2 may regulate GBM formation in a novel manner; CK2 may play a critical role in cancer stem cell (CSC) maintenance. Since glial CSCs have the ability to self-renew and initiate tumor growth, new treatments which target these CSCs are needed to treat this fatal disease. Inhibition of CK2 is potentially a novel method to inhibit GBM growth and reoccurrence by targeting the glial CSCs. A new, orally available, selective CK2 inhibitor, CX-4945 has had promising results when tested in cancer cell lines, in vivo xenograft models, and human clinical trials. The development of CK2 targeted inhibitors, starting with CX-4945, may lead to a new class of more effective cancer therapies.
    Journal of molecular and genetic medicine: an international journal of biomedical research 12/2013; 8(1).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background The Hedgehog (Hh) signaling pathway has been implicated in stem cell maintenance and its activation is aberrant in several types of cancer including mesothelioma. Protein kinase CK2 affects several cell signaling pathways through the mechanism of phosphorylation.Methods Protein and mRNA levels of CK2¿ and Gli1 were tested by quantitative RT-PCR and immunohistochemistry staining in mesothelioma samples and cell lines. Down-regulated Gli1 expression and transcriptional activity were demonstrated by RT-PCR, Western blot and luciferase reporter assay.ResultsIn this study, we show that CK2¿ is over-expressed and a positive regulator of Hegdehog/Gli1 signaling in human malignant pleural mesothelioma. First of all, we found that the mRNA levels of CK2¿ and Gli1 were broadly elevated and correlated (n¿=¿52, r¿=¿0.401, P¿<¿0.05), compared with LP9 (a normal mesothelial cell line). We then investigated their expression at the protein level, and found that all the 7 mesothelioma cell lines tested showed positive staining in CK2¿ and Gli1 immunohistochemistry. Correlation analysis by Pearson test for CK2¿ and Gli1 expression in the 75 mesothelioma tumors and the 7 mesothelioma cell lines showed that the two protein expression was significantly correlated (n¿=¿82, r¿=¿0.554, P¿<¿0.01). Furthermore, we demonstrated that Gli1 expression and transcriptional activity were down-regulated after CK2¿ was silenced in two mesothelioma cell lines (H28 and H2052). CK2¿ siRNA also down-regulated the expression of Hh target genes in these cell lines. Moreover, treatment with a small-molecule CK2¿ inhibitor CX-4945 led to dose-dependent inhibition of Gli1 expression and transcriptional activity. Conversely, forced over-expression of CK2¿ resulted in an increase in Gli1 transcriptional activity in H28 cells.Conclusions Thus, we report for the first time that over-expressed CK2¿ positively regulate Hh/Gli1 signaling in human mesothelioma.
    Journal of Experimental & Clinical Cancer Research 11/2014; 33(1):93. · 3.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cancer stem cells (CSC) and genes have been linked to cancer development and therapeutic resistance, but the signaling mechanisms regulating CSC genes and phenotype are incompletely understood. CK2 has emerged as a key signal serine/threonine kinase that modulates diverse signal cascades regulating cell fate and growth. We previously showed that CK2 is often aberrantly expressed and activated in head and neck squamous cell carcinomas (HNSCC), concomitantly with mutant (mt) tumor suppressor TP53, and inactivation of its family member, TAp73. Unexpectedly, we observed that classical stem cell genes Nanog, Sox2, and Oct4, are overexpressed in HNSCC with inactivated TAp73 and mtTP53. However, the potential relationship between CK2, TAp73 inactivation, and CSC phenotype is unknown. We reveal that inhibition of CK2 by pharmacologic inhibitors or siRNA inhibits the expression of CSC genes and side population (SP), while enhancing TAp73 mRNA and protein expression. Conversely, CK2 inhibitor attenuation of CSC protein expression and the SP by was abrogated by TAp73 siRNA. Bioinformatic analysis uncovered a single predicted CK2 threonine phosphorylation site (T27) within the N-terminal transactivation domain of TAp73. Nuclear CK2 and TAp73 interaction, confirmed by co-immunoprecipitation, was attenuated by CK2 inhibitor, or a T27A point-mutation of this predicted CK2 threonine phospho-acceptor site of TAp73. Further, T27A mutation attenuated phosphorylation, while enhancing TAp73 function in repressing CSC gene expression and SP cells. A new CK2 inhibitor, CX-4945, inhibited CSC related SP cells, clonogenic survival, and spheroid formation. Our study unveils a novel regulatory mechanism whereby aberrant CK2 signaling inhibits TAp73 to promote the expression of CSC genes and phenotype.
    Neoplasia (New York, N.Y.) 10/2014; 16(10):789–800. · 5.40 Impact Factor

Full-text (3 Sources)

Download
19 Downloads
Available from
Aug 28, 2014