Magnetic resonance imaging (MRI) analysis was performed on five animals/experimental group on day 24. The picture shows representative 2D images of tumor sections from one animal treated with vehicle and one animal treated with 15.0 mg/kg ATRA. The bar graph shows the volume of the tumors calculated after 3D reconstruction of the MRI images. Each point is the mean ± SE of five tumors. The P-value of the comparisons of ATRA versus vehicle is shown. 