Inhibition of mitotic cyclin B and cdc2 kinase activity by selenomethionine in synchronized colon cancer cells

Selenomethionine (SeMet), an organic selenium compound, has been demonstrat ed to have significant chemopreventive activity. However, the mechanism of action of SeMet has yet to be identified. Previously, our laboratory found that treatment of cells with SeMet induced apoptosis and altered the cell c ycle. These observations have led to further analysis of the cell cycle eff ects of SeMet in colon cancer cells. Synchronized HCT 116 colon cancer cell s treated with 100 muM SeMet for 66 h were found to have a transient delay in G(2)/M phase of the cell cycle at 18 and 24 h after treatment. With this was observed an inhibition of cell growth. Coincidentally with this delay was a decrease in mitotic cyclin a RNA expression at 18 h after treatment, In addition, the cdc2 kinase activity of HCT 116 cells was decreased at 18 h, Morphological studies indicate an increase in the number of treated cell s (45%) undergoing apoptosis at 66 h compared to control cells (27%). These studies demonstrate that modulation of mitotic cyclin expression and cdc2 kinase activity play a role in the ability of SeMet to inhibit tumor cell g rowth. A consequence of this prolonged arrest is apoptosis, [(C) 2001 Lippo ncott Williams & Wilkins.].