Mistletoe, a semiparasitic plant, holds interest as a potential anticancer agent because extracts derived from it have been shown to kill cancer cells in vitro[1,2,3,4,5,6,7,8,9,10] and to stimulate immune system cells both in vitro and in vivo.[10,11,12,13,14,15,16,17,18,19,20,21,22,23,24] Two components of mistletoe, namely viscotoxins, polysaccharides and lectins, may be responsible for these effects.[10,11,12,13,17,18,19,21,22,23,25,26,27,28,29,30,31,32] Viscotoxins are small proteins that exhibit cell-killing activity and possible immune-system-stimulating activity.[1,6,18,19,33,34] Lectins are complex molecules made of both protein and carbohydrates that are capable of binding to the outside of cells (e.g., immune system cells) and inducing biochemical changes in them.[10,35,36,37,38] In view of mistletoe's ability to stimulate the immune system, it has been classified as a type of biological response modifier. Biological response modifiers constitute a diverse group of biological molecules that have been used individually, or in combination with other agents, to treat cancer or to lessen the side effects of anticancer drugs. Mistletoe extracts have been demonstrated in preclinical settings to have other mechanisms of action, such as antiangiogenesis.
Preparations from mistletoe extracts are most frequently used in the treatment of cancer patients in German-speaking countries. Commercially available extracts are marketed under a variety of brand names, including Iscador (see explanation of suffixes below), Eurixor, Helixor, Isorel, Iscucin, Plenosol, and abnobaVISCUM. Some extracts are marketed under more than one name. Iscador, Isorel, and Plenosol are also sold as Iscar, Vysorel, and Lektinol, respectively. All of these products are prepared from Viscum album (Loranthaceae) (Viscum album L. or European mistletoe). They are not sold as a drug in the United States.
Mistletoe is a semiparasitic plant that grows on several types of common trees such as apple, oak, pine, and elm. Mistletoe extract has been used since ancient times to treat many ailments (see Question 1).
Mistletoe is one of the most widely studied complementary and alternative medicine therapies in people with cancer. In certain European countries, preparations made from European mistletoe are among the most prescribed drugs for patients with cancer (see Question 1).
In addition to European mistletoe, extracts from a type of Korean mistletoe (Viscum album var. coloratum [Kom.] Ohwi) have demonstrated in vitro and in vivo cytoxocity in laboratory studies.[41,42,43,44,45]