Influence of Carbohydrates on the Cytotoxicity of an Aqueous Mistletoe Drug and of Purified Mistletoe Lektins Tested on Human T-Leukemia Cells

Author(s): Doser, M., Hülsen, H., Mechelke, F.

Journal/Book: Arzneim-Forsch/Drug Res. 1989; 39: 647-651.

Abstract: Partially and highly purified lectins from Viscum album L. (mistletoe) cause a dose-dependent decrease of viability of human leukemia cell cultures, MOLT-4, after 72 h treatment. The LC50 of the partially purified lectin was 278 ng/ml, of the highly purified lectin 1.3 ng/ml. Compared to the highly purified lectin a 140-fold higher protein concentration of an aqueous mistletoe drug was required to obtain similar cytotoxic effects on MOLT-4 cells. Cytotoxicity of the highly purified lectin was preferentially inhibited by D-galactose and lactose, cytotoxicity of the mistletoe drug and the partially purified lectin were preferentially inhibited by lactose and N-acetyl-D-galactosamine (GalNAc).Two lectin fractions with almost the same cytotoxic activity on MOLT-4 cells but with different carbohydrate affinities were isolated by affinity chromatography from the mistletoe drug: mistletoe lectin I with an affinity to D-galactose and GalNAc and mistletoe lectin 11 with an affinity to GalNAc. The lectin fractions and the mistletoe drug inhibited protein synthesis of MOLT-4 cells stronger than DNA synthesis.Furthermore a subpopulation of MOLT-4, resistant to cytotoxic doses of both the mistletoe drug and the mistletoe lectins, was shown to exhibit a reduced amount of GalNAc and N-acetyl-D-glucosamine in their cellular glycoproteins which are probably responsible for the binding of the cytotoxic lectins.These results indicate that lectins are the main toxins in the mistletoe drug.

Keyword(s): Helixor

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