Some studies have suggested that omega-3
polyunsaturated fatty acids (PUFAs) have an inhibitory effect on the growth of
cancer cells and therefore have the potential to increase the efficacy of
cancer chemotherapeutic drugs. Considering that omega-3 PUFAs are present abundantly in harp seal oil, we investigated the effect of seal oil on the cytotoxicity and apoptosis induced by
paclitaxel in 2
breast cancer cell lines, MCF-7 and MDA-MB-231, respectively. Cytotoxicity evaluated by
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed that the concentration of
paclitaxel that is required for 50% inhibition of cell growth in the presence of seal oil was significantly lower than that of
paclitaxel alone. Apoptosis assessment based on morphological changes and DNA fragmentation results indicated that more cells treated with
paclitaxel in combination with seal oil underwent apoptosis than with
paclitaxel alone. Western blot analysis showed that the expression of B cell lymphoma-2 (Bcl-2) protein, an apoptosis inhibitory protein, in both cell lines was decreased more significant by
paclitaxel in combination with seal oil than by
paclitaxel alone. In addition, seal oil alone was found to induce apoptosis in both cell lines tested, which appeared to be due to the increased intracellular
lipid peroxides produced. It is therefore concluded that
paclitaxel in combination with seal oil demonstrated enhanced cytotoxicity and apoptosis in MCF-7 and MDA-MB-231 cells compared to
paclitaxel alone, and the use of seal oil may be beneficial in the treatment of
breast cancer.