Analysis of cell proliferation and apoptosis in tumor xenografts.

<p>(A) Cell apoptosis was evaluated using the TUNEL assay. Apoptotic cells (green) were counted from fluorescence images taken from 10 random fields at 200× magnification. Treatment with the combination of VPA and ATRA significantly increased apoptosis compared to the vehicle or single-drug treatment. (B) Cell proliferation was evaluated using Ki67 staining. The distribution of Ki67-positive cells was scored by two researchers. A significant decrease in the number of Ki67-positive cells was observed in tumors treated with the combination of drugs compared to VPA treatment alone. There was only slightly decrease in the number of Ki67-positive cells in ATRA treated group compared with the control group. *<i>P</i><0.05, **<i>P</i><0.01, versus the control group.