Cytostatic and cytocidal effects of mistletoe (Viscum album L.) quercus extract Iscador

Mistletoe (Viscum album) extract (Iscador) is used either alone or in combination with chemotherapy or radiotherapy in the treatment of tumor patients. In this study the effects of Viscum album Quercus (VA Qu) extract (1000 ng lectin and 6 microg viscotoxin/ml) in various doses were investigated in an in vitro model with tumor cells: three multiple myeloma (MM) cell lines (OPM-2, RPMI-8226, U-266) and three B cell lymphoma cell lines (U-698, DOHH-2, WSU-1). None of the three B lymphoma cell lines and none of the three multiple myeloma cell lines produced interleukin (IL)-6 spontaneously or after treatment with VA Qu extract. All three multiple myeloma cell lines expressed surface IL-6R and gp130, the B cell lymphomas expressed only gp130. Viscum album/Qu extract markedly downregulated the membrane expression of IL-6R and gp130 in RPMI-8226 (down to 29% and 32%) and the expression of gp130 in WSU-1 (down to 22%). There was a marked reduction of viable cells of RPMI-8226 (down to 28%) and WSU-1 (down to 8 %) at 100 microg/10(6) cells /ml. There was a clear relationship between the inhibition of proliferation and viability: the percentage reductions of the viable cells at 48 and 72 h were similar to those of proliferation at 24 and 48 h, respectively. This means that firstly the proliferation of the tumor cell is inhibited and then afterwards these cells die by apoptosis or necrosis. The inhibitory effect of VA Qu on the proliferation can be termed cytostatic, on the survival cytocidal. VA Qu was more effective in cells having a high proliferation rate than in those with a low proliferation rate. The effective dose range lay between 25 and 100 microg/10(6) cells/ml (5-20 ng lectin/10(6) cells/ml) for all parameters.