Imaging of firefly luciferase activity under antiangiogenic therapy in a heat shock protein 70-transfected melanoma tumor model.

Abstract

We investigated the effect of targeted gene therapy on heat shock protein 70 (Hsp70) expression in a melanoma tumor model (M21). M21 cells transfected with a plasmid containing the firefly luciferase reporter gene (ffluc), whose expression is driven by the hsp70 (hspa1b) or the cytomegalovirus (CMV) promoter, were grown to a size of 600 mm3. Five animals in each group were intravenously treated with an Arg-Gly-Asp peptide-nanoparticle/Raf-1 kinase inhibitor protein [RGD-NP/RAF(-)] complex. Bioluminescence imaging (BLI) (IVIS, Xenogen, Alameda, CA) was performed at set time intervals. Western blot analysis of the HSP70 protein was simultaneously performed. The size of the treated M21 tumors was nearly constant (637.8 ± 33.4 mm3 vs 674.8 ± 34.4 mm3). BLI showed that if transcription was controlled by the CMV promoter, firefly luciferase activity decreased to 51.1% ± 8.3%. When transcription was controlled by the hsp70 promoter, the highest firefly luciferase activity (4.4 ± 0.3-fold) was observed after 24 hours. In accordance with BLI, Western blot analysis showed an increase in the level of HSP70, with the maximum detection 24 hours after the injection of the RGD-NP/RAF(-) complex. Targeted antiangiogenic therapy can induce luciferase activity where transcription is controlled by an hsp70 promoter and HSP70 protein in melanoma tumors.