Delivery of short duration electric pulses, known as nanoelectropulse therapy, is being developed as a potential local cancer therapy. In this modality, electric pulses with nanosecond scale duration and high field (MV/m) are applied to cells. Because the pulses are shorter than the charging time constant of the external plasma membrane (30-100 ns), voltage across the cell membrane is limited. Intracellular membranes are smaller, therefore having a shorter charging time constant. As a result, pulses disproportionately affect intracellular membranes. We extended study of these pulses to a range of malignant cells. By assessing viable cells by an MTT assay 96 hours after delivery of pulses, we have characterized elements of the pulse that lead to more effective killing of malignant cells. In the Jurkat T cell leukemia/lymphoma cell line, we show that at equivalent energy, 200 pulses of 20 ns duration lead to more effective cell killing than 570 pulses of 7 ns duration. We also show that increasing the voltage leads to increased cell killing. We demonstrate that many hematologic cell lines are extremely susceptible to nanoelectropulse therapy in vitro, including follicular lymphoma (SUDHL-6), diffuse large B cell lymphoma (SUDHL-16) and multiple myeloma (RPM8226) cell lines. The effects of pulsation on solid tumor cell lines varied more. Of the solid tumor cell lines tested, AsPC-1 pancreatic cancer cells were the most effectively killed. Based on these data, we extended our findings to in vivo work. We injected AsPC-1 cells into both flanks of eight athymic nude mice. We designed a catheter capable of delivering 6kV pulses, and pulsed one of the resultant tumors in each mouse, leaving the other tumor as a control. Effective killing occurred when 200 pulses of 20 ns duration were delivered at 20 Hz. Complete clinical responses were found in two of the tumors. One tumor recurred and the other was confirmed to be a pathologic complete response. In summary, we have demonstrated the ability of nanoelectropulse therapy to kill tumor cells both in vitro and in vivo. This technology may allow a unique approach to killing of cancer cells.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]