Original Article
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World J Gastroenterol. May 7, 2013; 19(17): 2621-2628
Published online May 7, 2013. doi: 10.3748/wjg.v19.i17.2621
CYP24A1 inhibition facilitates the anti-tumor effect of vitamin D3 on colorectal cancer cells
János P Kósa, Péter Horváth, János Wölfling, Dóra Kovács, Bernadett Balla, Péter Mátyus, Evelin Horváth, Gábor Speer, István Takács, Zsolt Nagy, Henrik Horváth, Péter Lakatos
János P Kósa, Péter Horváth, Bernadett Balla, Evelin Horváth, Gábor Speer, István Takács, Zsolt Nagy, Henrik Horváth, Péter Lakatos, 1st Department of Internal Medicine, Semmelweis University, H-1083 Budapest, Hungary
János Wölfling, Dóra Kovács, Department of Organic Chemistry, University of Szeged, H-6720 Szeged, Hungary
Péter Mátyus, Department of Organic Chemistry, Semmelweis University, H-1092 Budapest, Hungary
Author contributions: Kósa JP and Lakatos P designed and coordinated the study; Kósa JP, Horváth P, Balla B and Horváth E carried out the cell culture and mRNA experiments; Wölfling J, Kovács D and Mátyus P designed and synthesized the compounds used; Speer G, Takács I, Nagy Z and Horvath H contributed to the data analysis; Kósa JP and Horváth P wrote the paper.
Supported by Research Grants ETT 022/2006 and ETT 151/2009 from the Ministry of Health, Hungary; TÁMOP-4.2.1/B-09/1/KONV-2010-0005 from Creating the Center of Excellence at the University of Szeged, supported by the European Union and co-financed by the European Regional Fund
Correspondence to: János P Kósa, PhD, 1st Department of Internal Medicine, Semmelweis University, Koranyi 2/a, H-1083 Budapest, Hungary. jkosa@bel1.sote.hu
Telephone: +36-1-2100278 Fax: +36-1-2104874
Received: May 23, 2012
Revised: August 21, 2012
Accepted: August 25, 2012
Published online: May 7, 2013
Abstract

AIM: The effects of vitamin D3 have been investigated on various tumors, including colorectal cancer (CRC). 25-hydroxyvitamin-D3-24-hydroxylase (CYP24A1), the enzyme that inactivates the active vitamin D3 metabolite 1,25-dihydroxyvitamin D3 (1,25-D3), is considered to be the main enzyme determining the biological half-life of 1,25-D3. During colorectal carcinogenesis, the expression and concentration of CYP24A1 increases significantly, suggesting that this phenomenon could be responsible for the proposed efficacy of 1,25-D3 in the treatment of CRC. The aim of this study was to investigate the anti-tumor effects of vitamin D3 on the human CRC cell line Caco-2 after inhibition of the cytochrome P450 component of CYP24A1 activity.

METHODS: We examined the expression of CYP24A1 mRNA and the effects of 1,25-D3 on the cell line Caco-2 after inhibition of CYP24A1. Cell viability and proliferation were determined by means of sulforhodamine-B staining and bromodeoxyuridine incorporation, respectively, while cytotoxicity was estimated via the lactate dehydrogenase content of the cell culture supernatant. CYP24A1 expression was measured by real-time reverse transcription polymerase chain reaction. A number of tetralone compounds were synthesized to investigate their CP24A1 inhibitory activity.

RESULTS: In response to 1,25-D3, CYP24A1 mRNA expression was enhanced significantly, in a time- and dose-dependent manner. Caco-2 cell viability and proliferation were not influenced by the administration of 1,25-D3 alone, but were markedly reduced by co-administration of 1,25-D3 and KD-35, a CYP24A1-inhibiting tetralone. Our data suggest that the mechanism of action of co-administered KD-35 and 1,25-D3 does not involve a direct cytotoxic effect, but rather the inhibition of cell proliferation.

CONCLUSION: These findings demonstrate that the selective inhibition of CYP24A1 by compounds such as KD-35 may be a new approach for enhancement of the anti-tumor effect of 1,25-D3 on CRC.

Keywords: Colorectal cancer; CYP24A1 inhibition; Vitamin D3; Tetralone derivatives; Caco-2 cell culture