Molecular nuclear imaging of tumoral angio genesis using a rgd-containing tracer, Raft-RGD, targeted at the neo vessel-specific integrin αvβ3

Tumoral neo-angio genesis targeting is currently a major field of research for the diagnostic and treatment of solid tumors. Endothelial cells from neo vessels over express several specific markers such as the αvβ3 integrin, which binds RGD (-Arg-Gly-Asp-)- containing peptides. We evaluated the potential of a novel radiotracer - RAFT-RGD - for the molecular nuclear imaging of neo vessels. In vitro, the coupling of 4 c(RGDfK) to the RAFT platform resulted in an increased cellular uptake of the tracer by αvβ3 positive cells when compared to c(RGDfK). Furthermore, RAFTRGD has a higher affinity than c(RGDfK) and similar properties for angio genesis inhibition. In vivo, both αvβ3 positive and negative tumors were visible by non invasive whole body planar and tomographic imaging from 30 min to 24 h post-injection, using a gamma camera dedicated to small animal imaging. Despite a lack of significant contrast improvement compare with c(RGDfK), RAFT-RGD could represent a promising tracer for tumoral angio genesis since it could provide invaluable information about tumor development and treatment efficacy in Nuclear Medicine departments. Furthermore, thanks to its chemical structure, RAFT-RGD can be labelled with a variety of radioisotopes including γ and β- emitters, allowing interesting therapeutical applications such as internal targeted radiotherapy. (author)