Baculovirus Vector-Mediated Transfer of Sodium Iodide Symporter and Plasminogen Kringle 5 Genes for Tumor Radioiodide Therapy

BACKGROUND: Both tumor cells and their supporting endothelial cells should be considered for targeted cell killing when designing cancer treatments. Here we investigated the feasibility of combining radioiodide and antiangiogenic therapies after baculovirus-mediated transfer of genes encoding the sodium iodide symporter (NIS) and plasminogen kringle 5 (K5). METHODS: A recombinant baculovirus containing the NIS gene under control of the human telomerase reverse transcriptase (hTERT) promoter and the K5 gene driven by the early growth response 1 (Egr1) promoter was developed. Dual-luciferase reporter assay was performed to confirm the activation of hTERT transcription. NIS and K5 gene expression were identified by Western blot and Real-Time PCR. Functional NIS activity in baculovirus-infected Hela cells was confirmed by the uptake of (125)I and cytotoxicity of (131)I. The apoptotic effect of (131)I-induced K5 on baculovirus-infected human umbilical vein endothelial cells (HUVECs) was analyzed by a flow cytometry-based assay. In vivo, NIS reporter gene imaging and therapeutic experiments with (131)I were performed. Finally, the microvessel density (MVD) in tumors after treatment was determined by CD31 immunostaining. RESULTS: The activation of hTERT transcription was specifically up-regulated in tumor cells. NIS gene expression markedly increased in baculovirus-infected HeLa cells, but not in MRC5 cells. The Hela cells showed a significant increase of (125)I uptake, which was inhibited by NaClO(4), and a notably decreased cell survival rate by (131)I treatment. Expression of the K5 gene induced by (131)I was elevated in a dose- and time-dependent manner and resulted in the apoptosis of HUVECs. Furthermore, (131)I SPECT imaging clearly showed cervical tumor xenografts infected with recombinant baculovirus. Following therapy, tumor growth was significantly retarded. CD31 immunostaining confirmed a significant decrease of MVD. CONCLUSION: The recombinant baculovirus supports a promising strategy of NIS-based raidoiodide therapy combined with K5-based antiangiogenic therapy by targeting both the tumor and its supporting vessels.