Carcinogenesis Advance Access originally published online on November 21, 2007
Carcinogenesis 2008 29(2):371-380; doi:10.1093/carcin/bgm265
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Licofelone, a dual COX/5-LOX inhibitor, induces apoptosis in HCA-7 colon cancer cells through the mitochondrial pathway independently from its ability to affect the arachidonic acid cascade
Department of Experimental Evolutionary Biology, University of Bologna, via F. Selmi 3, Bologna 40126, Italy
1 Center for Applied Biomedical Research, Sant'Orsola University Hospital, Bologna 40126, Italy
2 Department of Histology, Embryology and Applied Biology, University of Bologna, Bologna 40126, Italy
3 Institute for the Organic Synthesis and Photoreactivity, Consiglio Nazionale delle Ricerche, Bologna 40129, Italy
4 Department of Pharmaceutical-Medicinal Chemistry, Eberhard Karls Universität Tübingen, Tübingen 72076, Germany
* To whom correspondence should be addressed. Tel: +39 051 2094253; Fax: +39 051 2094286; Email: tiziana.guarnieri{at}unibo.it
Nowadays, no data are available concerning the potential use of dual cyclooxygenase (COX)/5-lipoxygenase (LOX) inhibitors as anticancer agents in colon cancer treatment. Here, we report, for the first time, that the dual COX/5-LOX inhibitor licofelone triggers apoptosis in a dose- and time-dependent manner in HCA-7 colon cancer cells. Induction of apoptosis was related to the recruitment of the intrinsic mitochondrial apoptotic pathway, as shown by loss in mitochondrial membrane potential, cytochrome c release, caspase-9 and 3 activation and poly-(ADP-ribose)polymerase-1 cleavage. Moreover, licofelone induced the cleavage of the full-length p21Bax into p18Bax, a more potent inducer of the apoptotic process than the uncleaved form. Pre-treatment of HCA-7 cells with the pan-caspase inhibitor z-VAD-fmk significantly blocked licofelone-induced apoptosis, confirming that this process occurred primarily in a caspase-dependent pathway. We also present evidences that licofelone was able to affect the arachidonic acid (AA) cascade, as it blocked the activity of 5-LOX and COX enzymes, and it induced, through the phosphorylation of cytoplasmic phospholipase A2 (cPLA2), the release of unesterified AA from HCA-7 membrane phospholipids. However, apoptosis induction was not related to the ability of licofelone to affect the AA cascade, since neither exogenous prostaglandin E2 and leukotriene B4 addition, nor pharmacological inhibition of cPLA2, was able to rescue HCA-7 cells from apoptosis. Even if further studies are needed to clarify the mechanism of licofelone-induced apoptosis, this study suggests that this drug, as well as similar dual COX/5-LOX inhibitors, may represent a novel and promising approach in colon cancer treatment.
Abbreviations: AA, arachidonic acid; COX, cyclooxygenase; cPLA2, cytoplasmic phospholipase A2; FFA, free fatty acid; GC, gas chromatography; JNK, c-jun N-terminal kinase; LOX, lipoxygenase; LTB4, leukotriene B4; MAFP, methyl arachidonyl fluorophosphate; MAPK, mitogen-activated protein kinase; NSAID, non-steroidal anti-inflammatory drug; PARP-1, poly-(ADP-ribose)polymerase-1; PBS, phosphate-buffered saline; PGE2, prostaglandin E2; PLA2, phospholipase A2
Received July 23, 2007; revised October 26, 2007; accepted November 12, 2007.