Conjugated linoleic acid (CLA) is a group of positional and geometric isomers of linoleic acid (LA) and has chemoprotective properties in a variety of experimental cancer models. Cis-9,trans-11 and trans-10,cis-12 CLA are the principal isomers found in foods. The present study was performed to determine whether a mixture of CLA isomers and the two individual CLA isomers induce apoptotic cell death in Caco-2 cells. Caco-2 cells were incubated in serum-free medium containing 100μM of the mixture of CLA isomers, 100μM linoleic acid, 10μM cis-9,trans-11 CLA, or 10μM trans-10,cis-12 CLA. The mixture of CLA isomers and trans-10,cis-12 CLA inhibited Caco-2 cell growth. By contrast cis-9,trans-11 CLA had no effect. Cells treated with the mixture of CLA isomers and trans-10,cis-12 CLA produced a distinct oligonucleosomal ladder with different sizes of DNA fragments, a typical characteristic of cells undergoing apoptosis and were stained with Annexin-V. The mixture of CLA isomers and trans-10,cis-12 CLA increased the activity of caspase-3, which is a central regulator of apoptosis. These results suggested that the growth inhibitory effect of the mixture of CLA isomers may, at least in part, be attributed to caspase-3 dependent apoptosis in Caco-2 cells.

Keywords: Conjugated linoleic acid (CLA), trans-10,cis-12 CLA, Apoptosis, Caspase-3