Fig. 1.

ST-mediated cell cycle arrest coincides with, but is not dependent on, decreased CDK4 levels. 76NE6 cells were treated with 4nM ST and harvested every 3h for (A) western blot analysis of CDK4, pRb, phospho-Rb (S780, CDK4/cyclin D dependent), Chk1 and Chk2. Blots representative of the two trials are shown. (B) Densitometry was performed on the western blot and the values were normalized to the zero time point and graphed. Bars represent the standard error. Adenovirus was used to overexpress CDK4 or an LUC control in 76NE6 cells. Cells were treated with 4nM ST and lysates were collected for (C) western blots, which were then analyzed by (D) densitometry. Each experiment was performed twice (*P < 0.05). (E) The cell cycle distribution of the infected cells was assessed by PI staining and flow cytometry of three independent experiments.