Figure 6

Osteogenic BMP-promoted OS tumor growth is enhanced by Id overexpression but is antagonized by Runx2 overexpression. (a) Exogenous expression of Id2 (to a lesser extent, Id3) further enhances BMP9-stimulated MG63 tumor growth. The animal experiments and procedures were carried out at the same time as described in Figure 5b. Briefly, MG63-Id or MG-63-RV cells were infected with AdBMP9, or AdGFP. At 16 h after infection, cells were collected and injected into athymic mice intratibially. Animals were subjected to Xenogen imaging at the indicated time points and tumor sizes were calculated as described in Figure 5b (i). ^*P<0.05 when compared with BMP9 only group at corresponding time points. Representative Xenogen images of the athymic mice intratibially injected with BMP9-transduced MG63-Id cells at weeks 2 and 8 are shown (ii and iv). Note that MG63-Id only, and GFP-transduced MG63-Id groups did not form any detectable masses at all time points. (b) Exogenous expression of Runx2 antagonizes BMP9-promoted MG63 tumor growth. The animal experiments and procedures were carried out at the same time as described in Figure 5b. MG63-Luc cells were infected with AdBMP9, AdGFP, AdBMP9+AdRunx2, or AdGFP+AdRunx2. At 16 h, the infected cells were collected and injected intratibially into athymic mice. Animals were subjected to Xenogen imaging at the indicated time points and tumor sizes were calculated as described in Figure 5b (i). ^*P<0.05 when compared with BMP9 only group at corresponding time points. Representative Xenogen images of the athymic mice intratibially injected with BMP9+Runx2-transduced MG63-Luc cells at weeks 2 and 8 are shown (ii). Note that animals injected with GFP+Runx2-transduced MG63-Luc cells did not form any detectable masses at the injection sites up to 10 weeks. (c) Exogenous expression of Runx2 modestly induces the expression of late osteogenic makers OPN and/or OC in OS lines. Subconfluent OS cells were infected with AdBMP9 or AdGFP. At 5 days after infection, cells were collected for RNA isolation and qPCR analysis using human OPN and OC-specific primers. Each assay condition was done in triplicate. OC, osteocalcin; OPN, osteopontin.