The endogenous cannabinoid, anandamide, induces cell death in colorectal carcinoma cells: a possible role for cyclooxygenase 2
- H A Patsos1,
- D J Hicks1,
- R R H Dobson1,
- A Greenhough1,
- N Woodman1,
- J D Lane2,
- A C Williams1,
- C Paraskeva1
- 1Cancer Research UK Colorectal Tumour Biology Group, Department of Pathology and Microbiology, School of Medical Sciences, University of Bristol, Bristol, UK
- 2Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
- Correspondence to:
Professor C Paraskeva
Cancer Research UK Colorectal Tumour Biology Group, Department of Pathology and Microbiology, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, UK;
- Accepted 5 July 2005
- Revised 24 June 2005
- Published Online First 11 August 2005
Background and aims: Cyclooxygenase 2 (COX-2) is upregulated in most colorectal cancers and is responsible for metabolism of the endogenous cannabinoid, anandamide, into prostaglandin-ethanolamides (PG-EAs). The aims of this study were to determine whether anandamide and PG-EAs induce cell death in colorectal carcinoma (CRC) cells, and whether high levels of COX-2 in CRC cells could be utilised for their specific targeting for cell death by anandamide.
Methods: We determined the effect of anandamide on human CRC cell growth by measuring cell growth and cell death, whether this was dependent on COX-2 protein expression or enzyme activity, and the potential involvement of PG-EAs in induction of cell death.
Results: Anandamide inhibited the growth of CRC cell lines HT29 and HCA7/C29 (moderate and high COX-2 expressors, respectively) but had little effect on the very low COX-2 expressing CRC cell line, SW480. Induction of cell death in HT29 and HCA7/C29 cell lines was partially rescued by the COX-2 selective inhibitor NS398. Cell death induced by anandamide was neither apoptosis nor necrosis. Furthermore, inhibition of fatty acid amide hydrolase potentiated the non-apoptotic cell death, indicating that anandamide induced cell death was mediated via metabolism of anandamide by COX-2, rather than its degradation into arachidonic acid and ethanolamine. Interestingly, both PGE2-EA and PGD2-EA induced classical apoptosis.
Conclusions: These findings suggest anandamide may be a useful chemopreventive/therapeutic agent for colorectal cancer as it targets cells that are high expressors of COX-2, and may also be used in the eradication of tumour cells that have become resistant to apoptosis.
- Δ9-THC, Δ9-tetrahydrocannabinol
- AEA, arachidonoyl ethanolamine (anandamide)
- CB, cannabinoid
- COX, cyclooxygenase
- CRC, colorectal carcinoma
- FAAH, fatty acid amide hydrolase
- FBS, fetal bovine serum
- HRP, horseradish peroxidase
- PG, prostaglandin
- PG-EA, prostaglandin-ethanolamide
- PI, propidium iodide
- RT-PCR, reverse transcriptase-polymerase chain reaction
Published online first 11 August 2005
Conflict of interest: None declared.