Synthesis and characterization of radioiodinated 3-phenethyl-2-indolinone
derivatives for SPECT imaging of survivin in tumors.
ABSTRACT
Survivin, overexpressed in most cancers, is associated with poor prognosis
and resistance to radiation therapy and chemotherapy. Herein, we report
the synthesis of three 3-phenethyl-2-indolinone derivatives and their application
as in vivo imaging agents for survivin. Of these, 3-(2-(benzo[d][1,3]dioxol-5-yl)-2-oxoethyl)-3-hydroxy-5-
iodoindolin-2-one (IPI-1) showed the highest binding affinity (Kd = 68.3nM) to recombinant human survivin, as determined by quartz crystal
microbalance (QCM). In vitro studies demonstrated that the [125I]IPI-1 binding in survivin-positive MDA-MB-231 cells was significantly
higher than that in survivin-negative MCF-10A cells. In addition, uptake
of [125I]IPI-1 by MDA-MB-231 cells decreased in a dose-dependent manner in the presence of the high-affinity survivin ligand S12; this is indicative of specific binding of [125I]IPI-1 to cellular survivin protein in vitro. Biodistribution studies
in MDA-MB-231 tumor-bearing mice demonstrated the moderate uptake of [125I]IPI-1 in the tumor tissue (1.37% ID/g) at 30 min that decreased to 0.32%
ID/g at 180 min. Co-injection of S12 (2.5 mg/kg) slightly reduced tumor
uptake and the tumor/muscle ratio of [125I]IPI-1. Although further structural modifications are necessary to improve
pharmacokinetic properties, our results indicate that PI derivatives may
be useful as tumor-imaging probes targeting survivin.