IN-VIVO TRANSFECTION OF MELANOMA-CELLS BY LITHOTRIPTER SHOCK-WAVES

The potential for gene transfection during shock wave tumor therapy wa s evaluated by searching for shock wave-induced DNA transfer in mouse tumor cells. B16 mouse melanoma cells were cultured by standard method s and implanted s.c. in female C57BL/6 mice 10-14 days before treatmen t. A luciferase reporter vector was used as the DNA plasmid for intrat umoral injection at 0.2 mg/ml tumor, Air at 10% of tumor volume was in jected after the DNA in some tumors to enhance acoustic cavitation act ivity. The shock wave generation system was similar to a Dornier HM-3 lithotripter with pressure amplitudes of 24.4 MPa peak positive and 5. 2 MPa peak negative. Luciferase production in isolated tumor cells was measured with a luminometer 1 day after treatment to assess gene tran sfer and expression. Exposure to 800 shock waves, followed by immediat e isolation and culture of tumor cells for 1 day, yielded 1.1 (0.43 SE ) pg/10(6) cells for plasmid injection only and 7.5 (2.5 SE) pg/10(6) cells for plasmid plus air injection, Significantly increased lucifera se production, relative to shams, occurred for 200-, 400-, 800-, and 1 200-shock wave treatments with plasmid and air injection. Exposure wit h the isolation of tumor cells delayed for a day to allow gene express ion within the growing tumors gave increased luciferase production for 100- and 400-shock wave exposures without and with air injection. Gen e transfer therefore can be induced during lithotripter shock wave tre atment in vivo, particularly with enhanced acoustic cavitation, which supports the concept that gene and shock wave therapy might be advanta geously merged.