TUMOR REGRESSIVE EFFECTS OF VISCUM ALBUM PREPARATIONS EXPLORATION OF IMMUNOMODULATORY MECHANISMS

Abstract

Viscum album is a parasitic plant that grows on apple or pine trees. It is commonly known as Euro- pean mistletoe. Viscum album (VA) preparations are the aqueous extracts used as a complemen- tary medicine in cancer therapy. Various clinical studies have shown that VA preparations improve the quality of life in different cancer patients. Biologically active components of VA extracts include Mistletoe lectins (ML), viscotoxins, polyphenols and polysaccharides. The treatment with VA preparations or with purified ML has been shown to be associated with tumor regression in several in vivo experimental models of tumoral implantation. Various in vitro studies have shown the cytotoxic effects of VA preparations on various tumor cells. The mecha- nisms underlying the anti-tumoral activity of VA preparations or ML are complex and involve apoptosis, angio- genesis and immunomodulation. The immunomodulatory mechanisms mediated by the VA preparations can complement the anti-tumoral effects, resulting in effective tumor regression. This review provides an account of the current status of the understanding of the VA-associated immunomodulation in various cell types including lymphoblastoid, monocytic and endothelial cell lines.