CK2α, over-expressed in human malignant pleural mesothelioma, regulates the Hedgehog signaling pathway in mesothelioma cells

Our plain-English summary of CK2α, over-expressed in human malignant pleural mesothelioma, regulates the Hedgehog signaling pathway in mesothelioma cells, by S. Zhang, Y.L. Yang, Y. Wang, et al (Journal of Experimental & Clinical Cancer Research, 2014).

The study

• Authors: S. Zhang, Y.L. Yang, Y. Wang, B. You, Y. Dai, G. Chan, D. Hsieh, I.J. Kim, L.T. Fang, A. Au, H.J. Stoppler, Z. Xu, D.M. Jablons, L. You
• Journal: Journal of Experimental & Clinical Cancer Research
• Published: 2014;33(1):93
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

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 CK2α 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.

Results: In this study, we show that CK2α 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 CK2α 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 CK2α and Gli1 immunohistochemistry. Correlation analysis by Pearson test for CK2α 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 CK2α was silenced in two mesothelioma cell lines (H28 and H2052). CK2α siRNA also down-regulated the expression of Hh target genes in these cell lines. Moreover, treatment with a small-molecule CK2α inhibitor CX-4945 led to dose-dependent inhibition of Gli1 expression and transcriptional activity. Conversely, forced over-expression of CK2α resulted in an increase in Gli1 transcriptional activity in H28 cells.

Conclusions: Thus, we report for the first time that over-expressed CK2α positively regulate Hh/Gli1 signaling in human mesothelioma.

In plain English

This laboratory study, from the University of California San Francisco, examined a protein called CK2α and a cell-signaling pathway called Hedgehog, tracked through a protein called Gli1, in human malignant pleural mesothelioma. It did not study asbestos exposure. The authors measured CK2α and Gli1 in tumor samples removed during surgery and in mesothelioma cell lines grown in the laboratory, and compared them with a normal pleura cell line (LP9). CK2α mRNA was raised in 43 of 44 tumor samples and 7 of 8 cell lines. Protein staining was positive for CK2α in 70 of 75 tumors and, separately, for Gli1 in 70 of 75 tumors. The two proteins were mildly correlated (r = 0.554, P less than 0.01, across 82 tumors and cell lines). In cell-line experiments, reducing CK2α with siRNA or blocking it with the drug CX-4945 reduced Gli1 activity, and adding extra CK2α increased it more than 10-fold. CX-4945 also slowed the growth of normal LP9 cells. The authors concluded that CK2α is over-expressed in mesothelioma and positively regulates Hedgehog/Gli1 signaling. They added that the precise mechanism still needs to be worked out.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study: measurement of CK2α and Gli1 in human tumor tissue and cell lines, plus experiments on cultured mesothelioma cell lines
• Who was studied: Tumor tissue from patients having surgery for mesothelioma at the University of California San Francisco: 44 primary samples for mRNA testing and 75 primary samples for protein staining. Also 6 normal pleura samples, mesothelioma cell lines (8 for mRNA, 7 for staining), and a normal pleura cell line (LP9) for comparison.
• Exposure: No asbestos or fiber exposure was studied. The article examined the protein kinase CK2α, which the authors reduced with siRNA, blocked with the inhibitors CX-4945 and TBB, or over-expressed in cell lines. Asbestos is mentioned only in the background.
• Main results:
  • CK2α mRNA was elevated, compared with the normal LP9 cell line, in 97.7% (43/44) of primary mesothelioma samples and 87.5% (7/8) of mesothelioma cell lines
  • All primary samples and cell lines tested showed elevated Gli1 mRNA compared with LP9
  • In the 75 primary mesothelioma samples, protein staining was positive for CK2α in 93.3% (70/75) and, separately, for Gli1 in 93.3% (70/75). These are two separate counts, not the number of tumors positive for both.
  • CK2α and Gli1 were mildly correlated at the protein level (n = 82 tumors and cell lines, r = 0.554, P less than 0.01) and correlated at the mRNA level (n = 52, r = 0.401, P less than 0.05)
  • CK2α siRNA reduced CK2α mRNA and protein levels in H28 and H2052 mesothelioma cells
  • Reducing CK2α with siRNA in H28 mesothelioma cells lowered Gli reporter activity by 48% (P less than 0.01) compared with control siRNA
  • In H28 cells, the CK2α inhibitor CX-4945 reduced Gli reporter activity by 47% at 3 μM (P less than 0.05) and by 70% at 10 μM (P less than 0.01)
  • Forced over-expression of CK2α in H28 cells increased Gli1 transcriptional activity more than 10-fold (P less than 0.01)
  • CX-4945 also inhibited the growth of normal mesothelial LP9 cells in a dose-dependent way (IC50 3.3 μM)
• The authors' conclusion: The authors concluded that CK2 is over-expressed in mesothelioma and positively regulates Hh/Gli1 signaling, and suggested that CK2 inhibitors such as CX-4945 may potentially benefit patients
• Limitations the authors state:
  • The authors state that the precise mechanism still needs to be worked out
  • The authors state that further studies are needed to identify patients who might benefit from CK2 inhibitors

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Mesothelioma, STEM, Immunohistochemistry, Mesothelial Cells.

Related studies

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• Mutational analysis of hedgehog signaling pathway genes in human malignant mesothelioma — C.B. Lim, C.M. Prêle, et al. (2013)
• Inhibition of hedgehog signaling reduces the side population in human malignant mesothelioma cell lines — H.A. Kim, M.C. Kim, et al. (2015)
• Discussion — (2014)
• Antagonizing the Hedgehog Pathway with Vismodegib Impairs Malignant Pleural Mesothelioma Growth In Vivo by Affecting Stroma — M. Meerang, K. Bérard, et al. (2016)
• Cul4A overexpression associated with Gli1 expression in malignant pleural mesothelioma — Y.L. Yang, J. Ni, et al. (2015)

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