Suppression of murine mammary carcinoma growth and metastasis by HSVtk/GCV gene therapy using in vivo electroporation

Abstract

The effectiveness of electroporation as a means of gene transfection, both in vitro and in vivo, was tested using the herpes simplex virus 1 thymidine kinase (HSVtk) gene in combination with ganciclovir (GCV) administration as therapy against murine mammary cancer. Approximately 80% of BJMC3879 metastatic mammary carcinoma cells, derived from MMTV-infected BALB/c mice, died as a result of HSVtk/GCV treatment 72 hours after the transfection; decreased DNA synthesis was also seen. Mammary tumors induced by inoculation of syngeneic mice with BJMC3879 cells were subsequently treated by direct injection of vector containing HSVtk (pHSVtk) alone, empty vector or saline alone twice a week. After each injection, the tumors were subjected to in vivo electroporation. Mice treated with pHSVtk or saline were intraperitoneally injected with GCV at 40 mg/kg five times a week. Significantly reduced tumor volumes were observed for the pHSVtk+GCV group in experimental week 2 and thereafter throughout the 2-month study. DNA synthesis was significantly decreased as well in the pHSVtk+GCV group compared with all other groups. Furthermore, metastasis to lymph nodes and lungs was significantly suppressed by HSVtk/GCV treatment. Expression of HSVtk in the tumors was confirmed by RT-PCR. Macrophage accumulations were frequently observed in the peripheries of necrotic regions in HSVtk/GCV-treated tumors, where levels of apoptosis were significantly higher than those observed in other groups. We therefore conclude that in vivo electroporation can result in efficient gene transfer and that the HSVtk/GCV prodrug system strongly suppresses tumor growth and metastases in this model.

Electrogene therapy using endostatin, with or without suicide gene therapy, suppresses murine mammary tumor growth and metastasis

“…11 We have further shown that HSVtk/GCV therapy strongly suppresses metastasis in a murine metastatic mammary cancer model. 13 Gene transfer by in vivo electroporation (electrogene transfer) has recently been found to be an effective method for introducing DNA into various tissues. [14][15][16][17] Although previously believed to have a very low transfection efficiency, it was recently reported that, under suitable conditions, transduction is approximately equivalent to that using an adenoviral vector concentration of 10 6 transduction U/ml.…”

“…Experimental gene therapy using in vivo electroporation has, in fact, recently been demonstrated to effective in several animal tumor models, for colon adenocarcinomas, 19 melanomas, 20 hepatocellular carcinomas, 21 urinary bladder carcinomas 22 and mammary adenocarcinomas. 13,23,24 Here, we conducted an antiangiogenic gene therapy trial using electrogene transfer of endostatin in a mouse metastatic mammary cancer model having a metastatic spectrum similar to that seen in human breast cancers. As a paramount challenge for antiangiogenic therapy is to design combination protocols that counteract angiogenic stimuli produced by the tumor cells and induce direct/indirect cytotoxicity, we also tried combination gene therapy of endostatin and HSVtk/GCV using electrogene transfer.…”

Electroporation-mediated and EBV LMP1-regulated gene therapy in a syngenic mouse tumor model

“…On the other hand, gene transfer by in vivo electroporation, a procedure that involves DNA injection followed by application of electric fields, is effective for introducing DNA into mouse muscle, 26 skin, 27 rat liver, 28 and tumors. 19,29 Earlier data show that use of in vivo electroporation enhances plasmid DNA uptake in tumor tissue, resulting in expression within the tumor. [30][31][32][33] Furthermore, in vivo electroporation is a safe and nontoxic delivery system.…”

Development of a gene therapy based bone marrow purging system for leukemias

“…Ganciclovir was added at a concentration of 50 mmol and cells were exposed for 72 hours. [22][23][24] Construction of EGFP expressing leukemia cell lines Construction, expansion and purification of the EGFP expressing retrovirus has been described previously. 25 Amphotropic retrovirus was harvested from the supernatant of the packaging cell line RetroPack PT67 (Clontech).…”