Purpose: The purpose of this paper is to study the association between RGD binding kinetics and αvβ3 integrin receptor density in the complex tumor milieu.
Procedures: We assessed αvβ3 in vitro and by (68)Ga-DOTA-[c(RGDfK)]2 positron emission tomography (PET) in tumors with varying αvβ3.
Results: Intrinsic αvβ3 expression decreased in the order of M21 >>> MDA-MB-231 > M21L in cells. Tumor volume of distribution by PET, V T, was significantly higher in M21 compared to isogenic M21L tumors (0.40 ± 0.01 versus 0.25 ± 0.02; p < 0.01) despite similar microvessel density (MVD) likely due to higher αvβ3. V T for MDA-MB-231 (0.40 ± 0.04) was comparable to M21 despite lower αvβ3 but in keeping with the higher MVD, suggesting superior tracer distribution.
Conclusions: This study demonstrates that radioligand binding kinetics of PET data can be used to discriminate tumors with different αvβ3 integrin expression-a key component of the angiogenesis phenotype-in vivo.