Dual Targeting of Integrin αvβ3 and VEGF Receptor Improves PET Imaging of Breast Cancer

Abstract Background: Neuropilin-1 (NRP-1) and integrin αvβ3 receptors are both overexpressed in breast cancer. Methods: We developed and synthesized a heterodimeric tracer consisting of Arg−Gly−Asp (RGD) and Ala-Thr-Trp-Leu-Pro-Pro-Arg (ATWLPPR) peptides that simultaneously targets integrin αvβ3 and NRP-1. We then investigated the diagnostic efficacy of RGD-ATWLPPR heterodimeric peptides in MCF-7 xenograft models in mice. DOTA-conjugated RGD-ATWLPPR peptides were then radiolabeled with 68Ga, and the receptor-binding characteristics and tumor-targeting efficacy of 68Ga-DOTA-RGD-ATWLPPR were investigated in vitro and in vivo. We also detected integrin αvβ3 and NRP-1 expression in MCF-7 cells and tumor tissues. Results: The peptide showed high stability in vitro. Static PET/CT imaging studies showed that MCF-7 tumors were clearly visible 30 min and 60 min after 68Ga-DOTA-RGD-ATWLPPR injection. Further, the heterodimer showed higher tumor uptake than 68Ga-DOTA-RGD or 68Ga-DOTA-ATWLPPR alone. High specificity was shown in blocking studies using RGD and ATWLPPR peptides. MicroPET/CT and biodistribution studies using 68Ga-DOTA-RGD-ATWLPPR showed that the tracer specifically targets NRP-1 and integrin ανβ3 receptors. Conclusions: Compared with 68Ga-DOTA-RGD and 68Ga-DOTA-ATWLPPR, 68Ga-DOTA-RGD-ATWLPPR has higher binding affinity, better targeting efficiency, and longer tumor retention time. It therefore has potential as an imaging probe for breast cancer detection.