A new frontier in the treatment of cancer: NK-1 receptor antagonists.

The past two decades have witnessed an exponential increase in research into cancer. This effort, however, has not been translated into better perspectives as regards the problem, although several fields of research have certainly been promising (the human genome project, gene therapy, the search for new cytostatic agents and stem cell research). New pathways must be opened up to offer future hope to oncologic patients. Thus, there is a need to explore other research initiatives in cancer ways to improve this chronic global problem. Substance P (SP) has a widespread distribution in both the central and peripheral nervous systems. It is known that after binding to the specific neurokinin-1 (NK-1) receptor, SP regulates biological functions related to cancer, such as tumour cell proliferation, angiogenesis, and migration of the tumour cells for invasion and metastasis. By contrast, it is also known that after binding to NK-1 receptors, the NK-1 receptor antagonists specifically inhibit tumour cell proliferation (tumour cells die by apoptosis), angiogenesis and the migration of the tumour cells. It is also known that NK-1 receptors are overexpressed in tumours. All these observations suggest that the SP/NK-1 receptor system could play an important role in the development of cancer and metastasis; that the NK-1 receptor could be a new promising target in the treatment of cancer, and that NK-1 receptor antagonists could improve cancer treatment.