Mistletoe therapy for human cancer: The role of the natural killer cells

Journal/Book: Anti-Cancer-Drugs 8 (suppl.1), 47-51. 1997;

Abstract: Extracts produced from *Viscum* album L.(mistletoe) as well as certainisolated components are able to stimulate different functions of theimmune system. The natural killer cells have been suggested as one ofthe candidates for direct tumour cell destruction. These cells aredefined by their ability to mediate non-major histocompatibility complex(MHC) restricted cytotoxicity without prior sensitization against aspecific antigen. However, their effectiveness in tumour defence in vivois unclear. In general, natural killer cells are unable to lyse freshautologous tumour cells in vitro unless activated byinterleukin-2-preincubation. The results of clinical studies arecontradictory, but there is evidence that they may contribute to theprevention of the development of recidives and metastases. In thisregard it is interesting that mistletoe extracts are able to stimulatenatural killer cell-mediated cytotoxicity in vitro directly as well asindirectly in a cytokine-like manner, with the active components beingcarbohydrates rather than lectins. Clinical application of mistletoeextracts or isolated lectins is reported to induce augmentation of bothnumber and activity of natural killer cells in peripheral blood in adose-dependent manner; however, non-responders also have been described.In future work it has to be clarified whether a mistletoe-derivedmodulation of the natural killer system is of benefit in the tumourdefence of cancer patients.COPYRIGHT BY Elsevier Science BV, Amsterdam, Netherlands END OF DOCUMENT

Keyword(s): Medical:cancer /drug therapy

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