Observation by small-animal in vivo imaging showed that inhibition of PTEN in vivo increased the growth of mouse breast tumors in situ, with increased mean length×width from 0.82×1.01 cm2 of control group to 1.41×1.63 cm2 (10 μg/kg) and 1.89×1.97 cm2 (20 μg/kg), respectively (Figures 4B–D), and increased tumor metastasis in distant organs. This evidence concerns the gene PTEN and breast neoplasm.