Development of novel 191Pt-labeled Hoechst33258: 191Pt is more suitable than 111In for targeting DNA

Abstract:This study aims to establish new labeling methods for no-carrier–added radio-Pt (191Pt) and to evaluate the in vitro properties of 191Pt-labeled agents compared with those of agents labeled with the common emitter 111In. 191Pt was complexed with the DNA-targeting dye Hoechst33258 via diethylenetriaminepentaacetic acid (DTPA) or the sulfur-containing amino acid cysteine (Cys). The intranuclear fractions of 191Pt- and 111In-labeled Hoechst33258 were comparable, indicating that the labeling for 191Pt via DTPA or Cys and the labeling for 111In via DTPA worked equally well. 191Pt showed a DNA-binding/cellular uptake ratio more than one order of magnitude greater than that of 111In. [191Pt]Pt-Hoechst33258 labeled via Cys showed a higher cellular uptake than that labeled via DTPA, resulting in a very high DNA-binding fraction of [191Pt]Pt-Cys-Hoechst33258 and extensive DNA damage. Our labeling methods of radio-Pt, especially via Cys, promote the development of radio-Pt-based agents for use in Auger electron therapy targeting DNA