Introduction Integrin α_vβ₃ is usually expressed at low or undetectable levels in most adult epithelia, but it is highly upregulated in tumors and correlates with disease progression. Moreover, unlike in quiescent endothelium, α_vβ₃ is highly expressed in tumor-associated vessels.

RGD (Arg-Gly-Asp) peptides carry the minimal integrin-binding sequence and are well-known to bind preferentially to α_vβ₃. Thus, RGD-based strategies have been widely adopted to design targeted molecules for cancer therapy and/or diagnosis.

We synthesized a new cyclic RGD-based peptidomimetic conjugated with a NIR fluorophore intended for intrasurgical use during tumor resection, to allow proper identification of tumor margins and sparse metastases by optical imaging. We present here the in vitro/ex vivo characterization of this molecule, meant to define its specificity for the target receptor, its ability to enter the cells and its in vivo behavior after administration to mice. Cellular models were used to preliminarily characterize the effects and the fate of the molecule as it contacts the cells. Mouse tumor models were used to investigate the distribution of the molecule in tumors after in vivo administration.

Methods Fluorescence microscopy, flow cytometry and immunofluorescence assays were used to define the features of the interaction of our molecule with cells expressing different α_vβ₃ levels.

Results The in vitro characterization of the molecule in contact with adherent cells reveals that it is internalized into the endosomal compartment and that it interferes with α_vβ₃-mediated cell adhesion. The affinity to both α_vβ₃ and HSA of our fluorescent RGD-based probe, demonstrated by flow cytometry and microscopy, is suitable for its intended use.

The ex vivo analyses of probe distribution in tumor tissues after in vivo administration highlight its ability to accumulate into the tumor mass and its specificity to delineate tumor margins.

Conclusions Our fluorescent RGD-based molecule is a promising optical imaging probe for fluorescence-guided surgical resection of tumors characterized by variable expression of α_vβ₃ integrin.

« Back to The 16th European Microscopy Congress 2016

EMC Abstracts - https://emc-proceedings.com/abstract/in-vitroex-vivo-behavior-of-a-new-optical-imaging-agent-targeting-%ce%b1v%ce%b23-integrin/