ANTITUMOUR ACTIVITY OF MESO-ZEAXANTHINE AND ITS MECHANISM OF ACTION

Objective: To evaluate the antitumour activity of meso-zeaxanthin and enumerate the mechanism of action. Methods : In vitro cytotoxicity was determined using transformed cells such as Dalton’s lymphoma ascites tumour cells, Ehrlich ascites tumour cells, L929 cells as well as using normal cells. Tumour reduction was determined by ascites tumour formation and solid tumour reduction. Mechanism of tumour reduction was determined by inhibition of apoptosis as seen by morphology, DNA ladder fraction and induction of P53 and caspase gene and inhibition of BCl 2 gene. Results : Carotenoid meso-zeaxanthin was found to be toxic to Dalton’s Lymphoma ascites cells, Ehrlich ascites tumour cells and L929 cells (IC 50 , 46, 51 and 37 μg/ml respectively) and was not cytotoxic to normal cells. Meso-zeaxanthin increased the lifespan of animals bearing Ehrlich ascites tumour (69.9%) and decreased the solid tumour induced by Dalton’s Lymphoma ascites tumour. Meso-zeaxanthin was found to induce apoptosis to DLA cells as seen from DNA Lymphoma ascites tumour. Meso-zeaxanthin was found to induce apoptosis to DLA cells as seen from DNA fragmentation, and DNA laddering and up regulation of P [53] and caspase 3 and 9 down regulation of BCl 2 gene expression. Conclusion : Meso-zeaxanthin which is non-toxic was found to reduce animal tumours. Keywords : Meso-zeaxanthin, Antitumour activity, Apoptosis, P[53] gene-BCl 2 gene