title: Macromolecular dynamic contrast-enhanced (DCE)-MRI detects reduced vascular permeability in a prostate cancer bone metastasis model following anti-platelet-derived growth factor receptor (PDGFR) therapy, indicating a drop in vascular endothelial growth factor receptor (VEGFR) activation.
abstract: The antivascular function of the platelet-derived growth factor receptor (PDGFR) inhibitor imatinib combined with paclitaxel has been demonstrated by invasive immunohistochemistry. The purpose of this study was to 1) noninvasively monitor the response to anti-PDGFR treatment, and 2) understand the underlying mechanism of this response. Thus, response to treatment was studied in a prostate cancer bone metastasis model using macromolecular (biotin-bovine serum albumin [BSA]-Gd-diethylene triamine pentaacetic acid [GdDTPA]) dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Human prostate cancer (PC-3MM2) bone metastases that caused osteolysis and grew in neighboring muscle showed a high blood-volume fraction (fBV) and vascular permeability (PS) at the tumor periphery compared to muscle tissue and intraosseous tumor. Imatinib alone or with paclitaxel significantly reduced PS by 35% (one-tailed paired t-test, P = 0.045) and 40% (P = 0.0003), respectively, whereas paclitaxel alone or no treatment had no effect. Based on changes in PS, we hypothesized that imatinib interferes with the signaling pathway of vascular endothelial growth factor (VEGF). This mechanism was verified by immunohistochemistry. It demonstrated reduced activation of both PDGFR-beta and VEGF receptor 2 (VEGFR2) in imatinib-treated mice. Our study therefore demonstrates that macromolecular DCE-MRI can be used to detect early vascular effects associated with response to therapy targeted to PDGFR, and provides insight into the role played by VEGF in anti-PDGFR therapy.
authors.affiliation: Department of Experimental Diagnostic Imaging, University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA. Hagit.Dafni@radiology.ucsf.edu
authors.forename: Hagit
authors.initials: H
authors.lastname: Dafni
authors.forename: Sun-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: James A
authors.initials: JA
authors.lastname: Bankson
authors.forename: Madhuri
authors.initials: M
authors.lastname: Sankaranarayanapillai
authors.forename: Sabrina M
authors.initials: SM
authors.lastname: Ronen
mesh_terms: D000818:Animals; D001859:Bone Neoplasms / Q000175:diagnosis / Q000188:drug therapy / Q000556:secondary; D002199:Capillary Permeability / Q000187:drug effects*; D045744:Cell Line, Tumor; D003287:Contrast Media; D015536:Down-Regulation / Q000187:drug effects; D019786:Gadolinium DTPA; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000188:drug therapy; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000627:therapeutic use*; D040262:Receptors, Vascular Endothelial Growth Factor / Q000378:metabolism*; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media; D020797:Receptor, Platelet-Derived Growth Factor beta; D040262:Receptors, Vascular Endothelial Growth Factor; D019786:Gadolinium DTPA