An immunocompetent, multifluorescent resource for real-time analysis of osteosarcoma progression, metastasis, and response to therapy.

The ROCCIA mouse, a quintuple-mutant immunocompetent model, develops multifluorescent osteosarcoma tumors that allow labeled cell populations to be traced in tumors and in circulation, with postnatal inactivation of p53 and Rb1 resembling human OS development. Using it, Osx-expressing fluorescent tumor cells were shown to appear in circulation upon OS development and to predominate in lung metastases, marking a potential therapy target. The model's immune microenvironment mimics the human OS microenvironment.