Radiolabeled RGD Tracer Kinetics Annotates Differential [alpha]^sub v^[beta]^sub 3^ Integrin Expression Linked to Cell Intrinsic and Vessel Expression

The purpose of this paper is to study the association between RGD binding kinetics and [alpha]^sub v^[beta]^sub 3^ integrin receptor density in the complex tumor milieu. We assessed [alpha]^sub v^[beta]^sub 3^ in vitro and by ^sup 68^Ga-DOTA-[c(RGDfK)]^sub 2^ positron emission tomography (PET) in tumors with varying [alpha]^sub v^[beta]^sub 3^. Intrinsic [alpha]^sub v^[beta]^sub 3^ expression decreased in the order of M21>>>MDA-MB-231>M21L in cells. Tumor volume of distribution by PET, V ^sub T^, was significantly higher in M21 compared to isogenic M21L tumors (0.40±0.01 versus 0.25±0.02; p