Differences in the in vitro effectiveness of preparations produced from mistletoes of various host trees.

The in vitro effectiveness of three Helixor preparations produced from mistletoes of different host trees on suspension cell cultures of the human leukemia cell line Molt 4 has been compared by means of dose-response investigations. After 72 h treatment the preparation produced from mistletoes of the appletree (Malus) shows the strongest effect on the growth and viability of the cell cultures. The preparation produced from mistletoes of the fir (Abies) shows also an evident but much weaker effect, whereas the preparation produced from mistletoes of the pine (Pinus) causes a weak effect only at a very high dosage. As shown in 24-h incorporation experiments with 3H-labelled DNA-, RNA- and protein precursors the preparation produced from mistletoes of the apple-tree reduces the protein synthesis of the cells to a greater extent than the DNA-and RNA-synthesis.