Vitamin D has broad range of physiological functions and antitumor effects.
24-Hydroxylase, encoded by the CYP24A1 gene, is the key enzyme for degrading many forms of vitamin D including the most active form, 1,25D3. Inhibition of CYP24A1 enhances 1,25D3 antitumor activity. To isolate regulators of CYP24A1 expression in prostate cancer cells, we established a stable prostate cancer cell line PC3 with CYP24A1 promoter driving luciferase expression to screen a small molecular library for compounds that inhibit CYP24A1 promoter activity. From this screening, we identified, 4,5,6,7-tetrabromobenzimidazole (TBBz), a protein kinase CK2 selective inhibitor as a disruptor of CYP24A1 promoter activity. We show that TBBz inhibits CYP24A1 promoter activity induced by 1,25D3 in prostate cancer cells. In addition, TBBz downregulates endogenous CYP24A1 mRNA level in TBBz-treated PC3 cells. Furthermore, siRNA-mediated CK2 knockdown reduces 1,25D3-induced CYP24A1 mRNA expression in PC3 cells. These results suggest that CK2 contributes to 1,25D3-mediated target gene expression. Finally, inhibition of CK2 by TBBz or CK2 siRNA significantly enhances 1,25D3-mediated antiproliferative effect in vitro and in vivo in a xenograft model. In summary, our findings reveal that protein kinase CK2 is involved in the regulation of CYP24A1 expression by 1,25D3 and CK2 inhibitor enhances 1,25D3-mediated antitumor effect.
Written by:
Luo W, Yu WD, Ma Y, Chernov M, Trump DL, Johnson CS. Are you the author?
Departments of Pharmacology and Therapeutics, Small Molecule Screening Core, and Medicine, Roswell Park Cancer Institute, Buffalo, New York.
Reference: Cancer Res. 2013 Apr 1;73(7):2289-97.
doi: 10.1158/0008-5472.CAN-12-4119
PubMed Abstract
PMID: 23358686
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