Figure 5.

Characterization of primary and metastatic lesions. Primary tibial osteosarcoma lesions are characterized by (A) H&E and B) B7H3 immunohistochemical staining, demonstrating formation of lesions with the appearance of malignant osteoid and invasion of the cortex and marrow cavity as well as B7H3 expression. Pulmonary metastases are characterized by (C) H&E and (D) B7-H3 immunohistochemical staining, demonstrating consistency of metastatic lesions with osteosarcoma lesions and persistent B7-H3 after metastasis. For (A–D), scale indicated is 500 μm for low power images and 50 μm for high power inserts. (E) Percent of tumor cells (GFP+) and B7-H3 expression on tumor cells (B7-H3+) as assessed by flow cytometry. Primary tumor sites contained high percentages of human tumor cells as assessed by GFP fluorescence (mean 56.5%, SE 7.3%). Tumor cells were additionally detected in all right lungs of mice not achieving long-term survival (mean 6.6%, SE 1.9%). B7-H3 expression was additionally demonstrated in all primary lesions (mean 95.8%, SE 2.2%) and pulmonary metastatic lesions (mean 48.7%, SE 9.4%). (F) Percent of animals with primary site engraftment, pulmonary metastases, and other distant hematogenous metastases on post-mortem histology and/or post-mortem flow cytometry (as applicable) on recovered tissue.