Purpose: Triple negative breast cancer (TNBC) is biologically characterised by heterogeneous presence of molecular pathways underlying it. Insulin-like growth factor receptor-1 (IGF-1R) expression and vascular endothelial growth factor-A (VEGF-A) have been identified as key factors in these pathways in TNBC. In this study, we aimed at in vivo PET imaging the effect of heat shock protein (Hsp) 90 inhibition by means of NVP-AUY922 on these pathways, with zirconium-89 (Zr-89) labelled antibodies targeting IGF-1R and VEGF-A.
Materials and methods: In vitro NVP-AUY922 effects on cellular IGF-1R expression and VEGF-A secretion were determined in MCF-7 and MDA-MB-231 cell lines. Moreover human TNBC bearing MDA-MB-231 mice received 50 mg/kg NVP-AUY922 or vehicle q3d intraperitoneally for 21 days. PET scans with Zr-89-MAB391 and Zr-89-bevacizumab for visualisation of IGF-1R and VEGF-A were performed before and during treatment. Ex vivo biodistribution and correlative tissue analyses were performed.
Results: NVP-AUY922 treatment reduced IGF-1R expression and VEGF-A excretion in both cell lines. Hsp90 inhibition lowered tumour uptake on Zr-89-MAB391-PET by 37.3% (P <0.01) and on Zr-89-bevacizumab-PET by 44.4% (P <0.01). This was confirmed by ex vivo biodistribution with a reduction of 41.3% injected dose (ID)/g for Zr-89-MAB391 and 37.8% ID/g for Zr-89-bevacizumab, while no differences were observed for other tissues. This coincided with reduced IGF-1R expression and mean vessel density in the NVP-AUY922 treated tumours.
Conclusion: Zr-89-MAB391 and Zr-89-bevacizumab PET reflect effect of Hsp90 inhibitors and can therefore potentially be used to monitor therapeutic effects of Hsp90 inhibitor therapy in TNBC. (C) 2014 Elsevier Ltd. All rights reserved.