CK2Â¿, over-expressed in human malignant pleural mesothelioma, regulates the Hedgehog signaling pathway in mesothelioma cell
Journal of Experimental and Clinical Cancer Research 2014 November 25 [Epub ahead of print] [Link]
Zhang S, Yang YL, Wang Y, You B, Dai Y, Chan G, Hsieh D, Kim IJ, Fang L, Au A, Stoppler HJ, Xu Z, Jablons DM, You L.
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.
Protein and mRNA levels of CK2Â¿ 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.
In this study, we show that CK2Â¿ 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 CK2Â¿ and Gli1 were broadly elevated and correlated (nÂ¿=Â¿52, rÂ¿=Â¿0.401, PÂ¿<Â¿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 CK2Â¿ and Gli1 immunohistochemistry. Correlation analysis by Pearson test for CK2Â¿ and Gli1 expression in the 75 mesothelioma tumors and the 7 mesothelioma cell lines showed that the two protein expression was significantly correlated (nÂ¿=Â¿82, rÂ¿=Â¿0.554, PÂ¿<Â¿0.01). Furthermore, we demonstrated that Gli1 expression and transcriptional activity were down-regulated after CK2Â¿ was silenced in two mesothelioma cell lines (H28 and H2052). CK2Â¿ siRNA also down-regulated the expression of Hh target genes in these cell lines. Moreover, treatment with a small-molecule CK2Â¿ inhibitor CX-4945 led to dose-dependent inhibition of Gli1 expression and transcriptional activity. Conversely, forced over-expression of CK2Â¿ resulted in an increase in Gli1 transcriptional activity in H28 cells.
Thus, we report for the first time that over-expressed CK2Â¿ positively regulate Hh/Gli1 signaling in human mesothelioma.