The histopathology of MT (+) group showed cell migration into lung and lymph nodes.

<p>After MT (+) or MT (−) treatment for 15 wk, the mice were sacrificed and the lung tissues were examined by histopathology with H&E stain. The tumor nodules were noticed in lung lobes in MT (+) group (A) and the alveoli were filled with tumor cells in MT (+) group, but not in MT (−) group (B). To provide direct evidence that MT induces metastasis in primary OS model, we labeled MG63 with GFP reporter gene and traced the GFP (+) tumor cells by immunohistochemistry. The GFP (+) cells were detected in lung nodules in MT (+) group while was undetectable in MT (−) group (C). In the lymph nodes, the GFP (+) cells were detected in right side where the tumor cells were injected in both MT (+) and MT (−), while in MT (+) group, the GFP (+) tumor cells were detected in bilateral lymph nodes (D).