Imaging the interaction of α v integrin-GFP in osteosarcoma cells with RFP-expressing host stromal cells and tumor-scaffold collagen in the primary and metastatic tumor microenvironment.

Human osteosarcoma 143B cells were previously stably transfected with an alpha(v) integrin green flourescent protein (GFP) vector. 143B cells expressing alpha(v) integrin-GFP were transplanted orthotopically in the tibia of transgenic nude mice ubiquitously expressing red fluorescent protein (RFP). The primary tumors acquired RFP-expressing stroma and were passaged orthotopically in the tibia in noncolored nude mice, which maintained the RFP stroma. The interaction of alpha(v) integrin-GFP expression in 143B cells with RFP-expressing host stromal cells was observed by confocal microscopy using the Olympus FV1000. Collagen fibers were imaged simultaneously in reflectance mode. The RFP-expressing stroma included cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) which persisted even 3 weeks after passage to nontransgenic nude mice. CAFs expressing RFP were aligned between collagen fibers and cancer cells expressing alpha(v) integrin-GFP. Six weeks after transplantation, pulmonary metastases expressing alpha(v) integrin-GFP could be identified. TAMs expressing RFP accompanied metastasized osteosarcoma cells expressing alpha(v) integrin-GFP in the lung. The current study demonstrates the importance of alpha(v) integrin interaction with stromal elements in osteosarcoma.