Imaging Bone Morphogenetic Protein 7 Induced Cell Cycle Arrest in Experimental Gliomas

Bone morphogenetic protein 7 (BMP-7) belongs to the superfamily of transforming growth factor beta-like cytokines, which can act either as tumor suppressors or as tumor promoters depending on cell type and differentiation. Our investigations focused on analyzing the effects of BMP-7 during glioma cell proliferation in vitro and in vivo. BMP-7 treatment decreased the proliferation of Gli36 Delta EGFR-LITG glioma cells up to 50% through a cell cycle arrest in the G(1) phase but not by induction of apoptosis. This effect was mediated by the modulation of the expression and phosphorylation of cyclin-dependent kinase 2, cyclin-dependent kinase inhibitor p21, and downstream retinoblastoma protein. Furthermore, in vivo optical imaging of luciferase activity of Gli36 Delta EGFR-LITG cells implanted intracranially into nude mice in the presence or absence of BMP-7 treatment corroborated the antiproliferative effects of this cytokine. This report clearly underlines the tumor-suppressive role of BMP-7 in glioma-derived cells. Taken together, our results indicate that manipulating the BMP/transforming growth factor beta signaling cascade may serve as a new strategy for imaging-guided molecular-targeted therapy of malignant gliomas.