The immune-system -stimulating and cytotoxic properties of mistletoe have been investigated in laboratory and animal studies.
Viscotoxins and lectins have been investigated as active components in mistletoe; however, most research has focused on the lectins.[1,2,3,4,5,6,7] Reviewed in [8,9] Purified mistletoe lectins have demonstrated cytotoxic and immune-system-stimulating activities. To date, four different lectins: ML-1, ML-2, ML-3, and Viscum albumchitin -binding agglutinin have been identified in mistletoe extracts. ML-1 (or viscumin) may be responsible for many of mistletoe's biological effects. When a laboratory method was used to selectively deplete ML-1 from Viscum album extracts, their cytotoxic and immune-system-stimulating properties were markedly reduced.[10,11] It should be noted that fermentation eliminates most of the ML-1 in mistletoe extracts. Reviewed in [13,14] Polysaccharide and oligosaccharide components of mistletoe extracts with substantial immune-stimulating properties have been reviewed.[15,16]
Cartilage is a type of tough, flexible connective tissue (see Question 1).
Cartilage from cows (bovine cartilage) and sharks has been studied as a treatment for people with cancer and other medical conditions for more than 30 years (see Question 2).
Laboratory and animal studies have looked at whether bovine and shark cartilage products can kill cancer cells, make the immune system more active against cancer, and prevent the body from making the new blood vessels that a tumor needs to grow...
The molecular structure of ML-1 consists of an alpha chain and a beta chain, which can be separated from one another.[1,17,18] Reviewed in [1,6,7,8,9,13] Each chain type appears to mediate a subset of the activities described for the intact lectin. Cytotoxicity is associated mainly with the alpha chain. In laboratory studies, the ML-1 alpha chain has been coupled to monoclonal antibodies to produce immunotoxins that target and kill specific cell types.[19,20] Reviewed in 
Recombinant ML-1, rML (also known as rViscunim or aviscumin) appears to have the same efficacy as plant-based ML-1 in laboratory studies. Since this is not an extract of mistletoe, it is out of the purview of this summary.
The beta chain of ML-1 is responsible for binding to the surface of a target cell. Studies of mistletoe lectin binding to cancer cells have examined whether the extent of cell binding can predict disease outcome or survival. Studies show that the prognostic value of ML-1 binding depends on the type of cancer. For human breast cancer cells, the amount of lectin-bound cells correlates positively with disease outcome. However, for human adenocarcinoma of the lung, there is no correlation between the amount of lectin-bound cells and disease survival. Though much research has looked at this particular aspect, there have not been studies that directly link the concentration of that component to any clinical activity of mistletoe.