RT Journal Article SR Electronic T1 89Zr-Bevacizumab PET of Early Antiangiogenic Tumor Response to Treatment with HSP90 Inhibitor NVP-AUY922 JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 761 OP 767 DO 10.2967/jnumed.109.071043 VO 51 IS 5 A1 Wouter B. Nagengast A1 Maarten A. de Korte A1 Thijs H. Oude Munnink A1 Hetty Timmer-Bosscha A1 Wifred F. den Dunnen A1 Harry Hollema A1 Johan R. de Jong A1 Michael R. Jensen A1 Cornelia Quadt A1 Carlos Garcia-Echeverria A1 Guus A.M.S. van Dongen A1 Marjolijn N. Lub-de Hooge A1 Carolien P. Schröder A1 Elisabeth G.E. de Vries YR 2010 UL http://jnm.snmjournals.org/content/51/5/761.abstract AB Angiogenesis is a critical step in tumor development, in which vascular endothelial growth factor (VEGF) is a key growth aspect. Heat shock protein 90 (HSP90), a molecular chaperone, is essential for the activity of key proteins involved in VEGF transcription. Currently, no biomarkers to predict the effect of, or monitor, HSP90 inhibition therapy in individual patients exist. 89Zr-bevacizumab PET provides a noninvasive tool to monitor tumor VEGF levels. The aim of this study was to investigate 89Zr-bevacizumab PET for early antiangiogenic tumor response evaluation of treatment with the new HSP90 inhibitor NVP-AUY922. In xenografts of A2780 and its cisplatin-resistant CP70 human ovarian cancer subline, 89Zr-bevacizumab small-animal PET was performed before and after NVP-AUY922 treatment and verified with histologic response and ex vivo tumor VEGF levels. Compared with pretreatment values, 2 wk of NVP-AUY922 treatment decreased 89Zr-bevacizumab uptake by 44.4% (P = 0.0003) in A2780 xenografts, whereas tumor uptake was not affected in CP70 xenografts. The same pattern was observed in A2780 and CP70 tumor VEGF levels, measured with enzyme-linked immunosorbent assay, and mean vessel density after NVP-AUY922 treatment. These findings coincided with reduction in the proliferation rate, assessed by Ki67 staining, in A2780 tumor tissue only. Conclusion: 89Zr-bevacizumab PET was in line with the antiangiogenic response and direct antitumor effects after NVP-AUY922 treatment, supporting the specificity of 89Zr-bevacizumab PET as a sensitive technique to monitor the antiangiogenic response of HSP90 inhibition in vivo.