Flow Electroporation with Pulsed Electric Fields for Purging Tumor Cells

Electroporation has been used in biological laboratories for many years to transiently porate cell membranes and permit plasmid or protein transfection. It has been shown that the application of pulsed electric fields (PEFs) of defined strength will kill off larger cells and select for viable small cells, in samples containing heterogeneous cells. This permits the selective killing of several blood and bone marrow–resident tumor cells. PEF technology is being applied to tumor purging of progenitor-cell transfusions, in support of high-dose chemotherapy, for the treatment of cancers such as lymphoma and multiple myeloma. Autologous stem-cell transplantation, in the setting of hematologic malignancies such as lymphoma, improves disease-free survival if the graft has undergone tumor purging. Progenitor cells are preserved or enriched. To overcome issues of electrical resistance, purging fidelity, and large sample volume, a flowing chamber PEF apparatus was designed and constructed for large-scale purging of clinical quantities of progenitor-cell transfusions. The specifics of this technique are described here. Treatment of greater than 10⁹ cells is achieved in 30 min, under optimized flow conditions designed to overcome surface area or resistance issues and to optimize exposure of cells to electric fields. Efficient, large volume tumor purging of greater than 3 logs, for mixtures of tumor cells and mononuclear cells, is routinely achieved under defined conditions.