IN-VITRO EFFECTS OF MISTLETOE EXTRACTS AND MISTLETOE LECTINS - CYTOTOXICITY TOWARDS TUMOR-CELLS DUE TO THE INDUCTION OF PROGRAMMED CELL-DEATH (APOPTOSIS)

The in vitro effects of therapeutically administered mistletoe extracts (ABNOBAviscum(R)) and pure mistletoe lectins (mainly mistletoe lectin I) on a variety of human and murine tumor cell lines have been investigated Mistletoe extracts and purified mistletoe lectins inhibited in vitro the growth of all tumor cell lines tested including B cell hybridomas, P815, EL-4, Ke37, MOLT-4 and U937. The mechanism of growth arrest was shown to be due to the induction of programmed cell death (apoptosis). Thus, fragmentation of genomic DNA into oligonucleosomal bands of approximately 200 base pairs in length was observed within 20 h when tumor cells were incubated with mistletoe extracts or lectins. These data point to a rational basis for the direct cytotoxic effects of mistletoe extracts and lectins apart from the postulated immunostimulatory properties of these agents.