Cancer specific apoptosis induced by electric field: A possible key mechanism in cell-competition and photodynamic action

Apoptosis induced by nanosecond pulsed electric field (nsPEF) has been demonstrated in non-small lung cancerous cells by the observation of field-induced change in cell morphology (swelling and blebbing), phosphatidylserine externalization and change in viability, whereas such field effect was harmless in normal lung cells. Lengthening of autofluorescence lifetime of nicotinamide adenine dinucleotide, decrease of mitochondrial membrane potential, activation of caspases, and generation of reactive oxygen species such as superoxide anion and singlet oxygen were clearly observed only in cancerous cells with application of nsPEF, indicating that the field-induced apoptotic cell death is initiated intrinsically in mitochondria. The finding implicated that electric field effect may be a key mechanism in “cell-competition” between normal and cancerous cells to facilitate the elimination of transformed cancerous cells from surrounding normal cells, and a new insight in “photodynamic action” to kill cancerous cells, which is a root of photodynamic therapy, has been provided.