Real-time GFP imaging of spontaneous HT-1080 fibrosarcoma lung metastases.

Metastasis to the lung is often a lethal event in sarcoma as well as other cancers. We report here a new animal model of sarcoma enabling the external real-time fluorescence imaging of spontaneous lung metastasis. The human fibrosarcoma cell line HT-1080 was transduced with the green fluorescent protein (GFP) gene. HT-1080-GFP cells were injected into the right hind footpad of severe combined immunodeficient (SCID) mice. The lung metastases were evaluated by whole-body fluorescence imaging as well as direct-view imaging in live animals through a skin-flap window over the chest wall. Spontaneous lung metastases were observed on the lungs of 11 of 12 mice. SCID mice well tolerated the skin-flap procedure enabling real-time imaging of spontaneous lung metastases with a resolution of approximately 50-100 microm. This procedure enabled external imaging at the micrometastasis level. Real-time evaluation of spontaneous lung metastasis in the same animals should allow drug evaluation and mechanistic studies not previously possible.