Systemic enzyme therapy in oncology: effect and mode of action.

Plant extracts with a high content of proteolytic enzymes have been used for a long time in traditional medicine. Besides proteolytic enzymes from plants, 'modern' enzyme therapy additionally includes pancreatic enzymes. The therapeutic use of proteolytic enzymes is partly based on scientific studies and is partly empirical. The aim of the current review is to provide an overview of clinical trials of systemic enzyme therapy in oncology, and to discuss the evidence for their possible mechanisms of action. Clinical studies of the use of proteolytic enzymes in oncology have mostly been carried out on an enzyme preparation consisting of a combination of papain, trypsin and chymotrypsin. This review of these studies showed that enzyme therapy can reduce the adverse effects caused by radiotherapy and chemotherapy. There is also evidence that, in some types of tumours, survival may be prolonged. The beneficial effect of systemic enzyme therapy seems to be based on its anti-inflammatory potential. However, the precise mechanism of action of systemic enzyme therapy remains unsolved. The ratio of proteinases to antiproteinases, which is increasingly being used as a prognostic marker in oncology, appears to be influenced by the oral administration of proteolytic enzymes, probably via an induction of the synthesis of antiproteinases. Furthermore, there are numerous alterations of cytokine composition during therapy with orally administered enzymes, which might be an indication of the efficacy of enzyme therapy. Effects on adhesion molecules and on antioxidative metabolism are also reviewed.