Cytotoxic Effects of Conjugated Linoleic Acids on Human Breast Cancer Cells (MCF7)

Conjugated linoleic acids (CLAs) comprised of geometrical and positional isomers of octadecadienoic (18:2) acid with conjugated double bond system. They are found naturally in ruminant food products such as meat and milk because of the process of bacterial biohydrogenation and hydrolysis in the rumen. Studies have shown that CLAs have many health promoting properties. This study was conducted to assess and compare the cytotoxic effects, induction of apoptosis and cell cycle arrest by CLA isomers on human breast cancer cells (MCF7). Cells were grown on RPMI 1640 media and treated with different concentrations of cis-9, trans-11 (c9, t11), trans-10, cis-12 (t10, c12) and mixed isomers of CLA for 72 hours. The results were determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) cytotoxicity assay and terminal deoxynucleotide transferase deoxyuridine triphosphate nick end labeling (TUNEL) assay. The viability of MCF7 cancer cells was reduced significantly (P<0.05) by all CLA isomers used in a dose-dependent manner. The median inhibitory concentration (IC ) value varies with type of CLA isomer. t10, c12 was significantly 50 (P<0.05) more potent than c9, t11 CLA isomer. All CLA isomers induced significantly (P<0.05) higher proportion of apoptotic cells. It was also observed that significantly (P<0.05) higher proportion of cells in G but lower 0/1 proportion in S and G /M phases of the cell cycle in treated cells. These results suggested that CLA isomers 2 reduce the viability of MCF7 cancer cells which is associated with cell cycle arrest and induction of apoptosis.