Newcastle disease virus-induced apoptosis in PC12 pheochromocytoma cells.

The avian paramyxovirus Newcastle disease virus (NDV) causes severe infections in birds. It is essentially nonpathogenic in rodents and human beings but was found to have an oncolytic potential against certain types of human malignancies. An attenuated NDV vaccine (designated MTH-68/H) was found to cause regression of various human tumors, but the mechanism of its oncolytic action and its selectivity toward malignant cells remain poorly understood. NDV was reported to cause apoptotic death in several avian cultured cell types. Programmed cell death may thus be the basis for the oncolytic effect of NDV vaccines. To test this possibility, we chose the PC12 rat pheochromocytoma cell line, a widely used model system for apoptosis. The MTH-68/H vaccine was found to cause apoptotic death of PC12 cells in a dose-dependent manner. A brief exposure of cells to the virus was found to trigger the apoptotic response. Cell death induced by the vaccine was not accompanied by significant alterations in the major mitogen-activated protein kinase pathways of these cells. Apoptotic DNA fragmentation was not affected by stimulating growth factor pathways or signaling mechanisms mediated by protein kinase C or the second messenger, calcium. In contrast, stimulation of protein kinase A by cyclic adenosine monophosphate analogs gave partial protection against the virus. PC12 cells thus provide a useful model system to study the effects of NDV on cell survival at the molecular level.