Glycerol modulation of the osteopontin-c effect in cancer cells.
A) Inductions of aquaporins by osteopontin or hydrogen peroxide. Microarray analysis was performed after extracting the RNA of either MCF-7 vector, MCF-7 OPNa, and MCF-7 OPNc cells or untreated and hydrogen peroxide-treated MCF-7 cells from soft agar on day 7 after plating. The results were examined for changes in the expression of aquaporins. B) Soft agar clone formation by MCF-7 transfectants (left panel) or ZR-75 transfectants  (right panel) in the presence or absence of glycerol. The soft agar assays were performed with the addition of 0.1% (v/v) autoclaved glycerol (20 µl at plating for MCF-7 cells, 5 µl at plating for ZR-75 cells) with a maintenance dose of 0.2 µl in 400 µl medium every other day. Glycerol induced the clone size by MCF-7 OPNc cells, but not MCF-7 vector cells in 3 additional experiments (the numbers indicate relative clone sizes). The glycerol-induced increase in clone size for OPNc cells is significant (over untreated OPNc cells) at p<0.05. Each symbol represents the average of 12–23 data points for MCF-7 cells and 11–25 data points for ZR-75 cells. gly = glycerol.