Phytochemicals from the genus Beta and their cytotoxic activity on Caco-2 colon cancer cells.

Introduction: Colon cancer is one of the most aggressive tumor. Caco-2 are colon cancer cells characterized by the mutated TP53 gene and over expression of Multi Drug Resistance (MDR) proteins. Beta vulgaris con-tains molecules able to inhibit the proliferation of Caco-2 [1], namely vitexin-2-O xyloside (VOX) purified from Swiss chard seeds and betalains (BLS) purified from red beetroot. The aim of this work was to study the individual and combined anticancer activity of VOX and BLS on Caco-2 cells as well as to identify their mechanisms of action.Materials and methods: Caco-2 colon cancer cells were grown in complete DMEM+NEAA and Sulforho-damine B assay was performed as described [1]; VOX was purified as described [2]; BLS were purified on DEAE FF anion exchange resin. Three fractions were obtained: R1 with 3 betaxanthins, R2 with 2 betacya-nins, R3 with 2 betaxanthins. In order to identify the involved apoptotic pathway, western blots for BAX, Bcl-2, PARP1/ARTD1 and Caspase 3 were performed as described [1].Results: Cells were incubated with phytochemicals at 24, 48 and 72 h and cytotoxicity was assessed. Indivi-dually VOX was the most cytotoxic compound (IC50: 25 μg/ml), whereas R1, R2, R3 showed a weaker, but significant cytotoxic effect. When combined in couples at concentrations: 25 μg/ml VOX plus 350 ng/ml R1, or 250 ng/ml R2 or 35 ng/ml R3, these phytochemicals showed a synergistic cytotoxic effect at 72h. Western blots showed an increase in the levels of BAX, cleaved PARP1/ARTD1, cleaved caspase 3 and a decrease of Bcl-2 levels in both individual and coupled treatments.Discussion: VOX and BLS exhibit on Caco-2 cells a significant cytotoxicity on Caco-2 cells, by means of the activation of intrinsic apoptotic pathway. When VOX and BLS were used in couples, a highest cytotoxicity was evident, probably due to remarkable cytotoxic effects of their metabolic products.