Non-thermal nanoelectroablation of UV-induced murine melanomas stimulates an immune response

Non-thermal nanoelectroablation therapy completely ablates UV-induced murine melanomas. C57/BL6-HGF/SF transgenic mice were exposed to UV radiation as pups and began to develop visible melanomas 5-6 months later. We have treated 27 of these melanomas in 14 mice with nanosecond pulsed electric field (nsPEF) therapy delivering 2000 electric pulses each 100 ns long and 30 kV/cm at a rate of 5-7 pulses per second. All nanoelectroablated melanoma tumors began to shrink within a day after treatment and gradually disappeared over a period of 12-29 days. Pyknosis of nuclei was evident within 1 h of nsPEF treatment, and DNA fragmentation as detected by TUNEL staining was evident by 6 h after nsPEF treatment. In a melanoma allograft system, nsPEF treatment was superior to tumor excision at accelerating secondary tumor rejection in immune-competent mice, suggesting enhanced stimulation of a protective immune response by nsPEF-treated melanomas. This is supported by the presence of CD4(+) -T cells within treated tumors as well as within untreated tumors located in mice with other melanomas that had been treated with nanoelectroablation at least 19 days earlier.