Figure 2. Inhibition of Rb phosphorylation by compound 4 and SU9516 in MDA-MB231 cells. Proteins were separated on SDS page, electroblotted to nitrocellulose, and hybridized with antibodies against phoshorylated Rb (T821, left panel and S780, right panel). Blots were subsequently hybridized with antibodies against total Rb and actin (used as loading control). C, control, untreated cells; SU, cells treated with SU9516 (10 μM); 4, cells treated with compound 4 (4 μM).