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CYP24, the enzyme that catabolizes the antiproliferative agent vitamin D, is increased in lung cancer

Authors :
Robert A. Parise
Talal El-Hefnawy
Martin Petkovich
Samuel S. Chuang
Merrill J. Egorin
Beatriz Kanterewicz
Mark Nichols
Pamela A. Hershberger
Mohammed Taimi
April M. Lew
Source :
International Journal of Cancer. 119:1819-1828
Publication Year :
2006
Publisher :
Wiley, 2006.

Abstract

1Alpha,25-dihydroxyvitamin D3 (1,25D3) displays potent antiproliferative activity in a variety of tumor model systems and is currently under investigation in clinical trials in cancer. Studies were initiated to explore its potential in nonsmall cell lung cancer (NSCLC), as effective approaches to the treatment of that disease are needed. In evaluating factors that may affect activity in NSCLC, the authors found that CYP24 (25-hydroxyvitamin D3-24-hydroxylase), the enzyme that catabolizes 1,25D3, is frequently expressed in NSCLC cell lines but not in the nontumorigenic bronchial epithelial cell line, Beas2B. CYP24 expression by RT-PCR was also detected in 10/18 primary lung tumors but in only 1/11 normal lung tissue specimens. Tumor-specific CYP24 upregulation was confirmed at the protein level via immunoblot analysis of patient-matched normal lung tissue and lung tumor extracts. Enzymatically active CYP24 is expected to desensitize NSCLC cells to 1,25D3. The authors therefore implemented a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay for 1,25D3 and its CYP24-generated metabolites to determine whether NSCLC cells express active enzyme. Analysis of NSCLC cell cultures revealed time-dependent loss of 1,25D3 coincident with the appearance of CYP24-generated metabolites. MK-24(S)-S(O)(NH)-Ph-1, a specific inhibitor of CYP24, slowed the loss of 1,25D3 and increased 1,25D3 half-life. Furthermore, combination of 1,25D3 with MK-24(S)-S(O)(NH)-Ph-1 resulted in a significant decrease in the concentration of 1,25D3 required to achieve maximum growth inhibition in NSCLC cells. These data suggest that increased CYP24 expression in lung tumors restricts 1,25D3 activity and support the preclinical evaluation of CYP24 inhibitors for lung cancer treatment.

Details

ISSN :
10970215 and 00207136
Volume :
119
Database :
OpenAIRE
Journal :
International Journal of Cancer
Accession number :
edsair.doi.dedup.....8d9da5d9540ed6f17062ab941f4b24c4
Full Text :
https://doi.org/10.1002/ijc.22058