Lectinology Meets Mythology: Oncological Future for the Mistletoe Lectin?

Abstract

On the basis of Celtic habits Plinius has referred to the mistletoe as “omnia sanatem”. Another mythological source (the Baldur legend) describes the mistletoe as a deadly weapon. These roots, but not scientific reasoning have contributed to the introduction of mistletoe extracts to cancer treatment by R. Steiner in this century. Various products presently enjoy considerable popularity in Western Europe as an unconventional treatment modality. A scientific proof for the claimed clinical efficiency, however, has not been presented, justifying the sceptical judgement of the medical community. Explicit drawbacks to perform standard evaluation are the lack of precise definition of the concentrations of the various compounds in the commercially available extracts as well as of supposedly active substances and their doses to elicit potentially beneficial effects in patients. Prospective randomized trials with a well-characterized test substance that would separate wishful thinking from reality and facts can thus not be conducted. To establish the essential prerequisites for clinical studies, stepwise biochemical, cell biological and experimental animal studies have recently enabled to focus ensuing efforts on a mistletoe lectin. Based on in vitro and on in vivo experiments with animal tumor models the galactoside-specific lectin has been shown to be a biological response modifier. Although it should definitely not be overlooked that the lectin's immunomodulatory capacity has still to prove its clinical efficiency, this example shows that mythology can well prompt lectinological research with testable clinical impact.