Abstract
BackgroundPreparations of mistletoe (Viscum album) are the form of cancer treatment that is most frequently used in the complementary medicine. Previous work has shown that these preparations are able to exert cytotoxic effects on carcinoma cells, the extent of which might be influenced by the host tree species and by the content of mistletoe lectin.MethodsUsing colorimetric assays, we have now compared the cytotoxic effects of Viscum album preparations (VAPs) obtained from mistletoe growing on oak (Quercus robur and Q. petraea, VAP-Qu), apple tree (Malus domestica,, VAP-M), pine (Pinus sylvestris, VAP-P) or white fir (Abies pectinata, VAP-A), on the in vitro growth of breast and bladder carcinoma cell lines. While MFM-223, KPL-1, MCF-7 and HCC-1937 were the breast carcinoma cell lines chosen, the panel of tested bladder carcinoma cells comprised the T-24, TCC-SUP, UM-UC-3 and J-82 cell lines.ResultsEach of the VAPs inhibited cell growth, but the extent of this inhibition differed with the preparation and with the cell line. The concentrations of VAP-Qu, VAP-M and VAP-A which led to a 50 % reduction of cell growth (IC50) varied between 0.6 and 0.03 mg/ml. Higher concentrations of VAP-P were required to obtain a comparable effect. Purified mistletoe lectin I (MLI) led to an inhibition of breast carcinoma cell growth at concentrations lower than those of VAPs, but the sensitivity towards purified MLI did not parallel that towards VAPs. Bladder carcinoma cells were in most cases more sensitive to VAPs treatment than breast carcinoma cells. The total mistletoe lectin content was very high in VAP-Qu (54 ng/mg extract), intermediate in VAP-M (25 ng/mg extract), and very low in VAP-P (1.3 ng/mg extract) and in VAP-A (1 ng/mg extract). As to be expected from the low content of mistletoe lectin, VAP-P led to relatively weak cytotoxic effects. Most remarkably, however, the lectin-poor VAP-A revealed a cytotoxic effect comparable to, or even stronger than, that of the lectin-rich VAP-Qu, on all tested bladder and breast carcinoma cell lines.ConclusionThe results suggest the existence of cytotoxic components other than mistletoe lectin in VAP-A and reveal an unexpected potential of this preparation for the treatment of breast and bladder cancer.
Highlights
Preparations of mistletoe (Viscum album) are the form of cancer treatment that is most frequently used in the complementary medicine
Materials Viscum album preparations (VAPs)-Qu (Charge Nr. 41011), VAP-M (Charge Nr. 30611), VAP-P (Charge Nr. 40511) and VAP-A (Charge Nr. 41111), as well as the isolated mistletoe lectin I (MLI) were provided by Hiscia AG (Arlesheim, CH); total mistletoe lectin concentrations of the preparations were determined by the manufacturer
Confirming previous observations [17], VAP-P exhibited the weakest effect on all breast carcinoma cells
Summary
Preparations of mistletoe (Viscum album) are the form of cancer treatment that is most frequently used in the complementary medicine. Previous work has shown that these preparations are able to exert cytotoxic effects on carcinoma cells, the extent of which might be influenced by the host tree species and by the content of mistletoe lectin. The progression of breast cancer can vary considerably since this disease comprises a wide range of malignancies that differ in invasiveness, in prognosis and in the molecular characteristics of the tumor cells. The cytotoxic effect of VAPs is likely to be at least partially caused by mistletoe lectin I (MLI), and the recombinant counterpart of this protein has been shown to be a powerful agent that is able to reduce cell proliferation and to induce apoptosis in the 0.1–1 ng/ml concentration range [18,19]. The in vitro toxicity of VAPs does not always correlate with their lectin content, suggesting that other components [20] might play a role [10,17]
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