CYP24A1 inhibition facilitates the anti-tumor effect of vitamin D3 on colorectal cancer cells

World J Gastroenterol. 2013 May 7;19(17):2621-8. doi: 10.3748/wjg.v19.i17.2621.

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

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Caco-2 Cells
  • Calcitriol / pharmacology*
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Colorectal Neoplasms / enzymology*
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / pathology
  • Dose-Response Relationship, Drug
  • Enzyme Induction
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • RNA, Messenger / biosynthesis
  • Steroid Hydroxylases / antagonists & inhibitors*
  • Steroid Hydroxylases / biosynthesis
  • Steroid Hydroxylases / genetics
  • Tetralones / pharmacology*
  • Time Factors
  • Vitamin D3 24-Hydroxylase

Substances

  • Antineoplastic Agents
  • Enzyme Inhibitors
  • RNA, Messenger
  • Tetralones
  • Steroid Hydroxylases
  • CYP24A1 protein, human
  • Vitamin D3 24-Hydroxylase
  • Calcitriol