Chemokines and their receptors as therapeutic targets: the role of the SDF-1/CXCR4 axis.

SDF-1 and CXCR4 are an important chemokine ligand/receptor pair, which play a crucial role in numerous biological processes including hematopoiesis, cardiogenesis, vasculogenesis, neuronal development and immune cell trafficking. They have also been implicated in various pathological conditions such as cancer, infection with the human immunodeficiency virus (HIV) and various inflammatory conditions. Numerous pharmacological agents exist that can modulate SDF-1/CXCR4-induced responses both in vitro and in vivo. The usefulness of these agents in affecting the outcome of pathological conditions influenced by the SDF-1/CXCR4 axis is currently being investigated. Whilst some of these compounds have been shown to be safe and well tolerated in phase 1 clinical trials, the full repercussions of SDF-1/CXCR4 inhibition or stimulation on normal physiological functions are yet to be appreciated. Inhibition of the SDF-1/CXCR4 axis may have positive effects in regulating tumour metastasis and growth, however, this may also negate immunological responses through dysregulated lymphocyte trafficking and contribute to disruption of hematopoiesis. As with any therapy, the usefulness of this type of intervention will require a balance between its positive effect on the disease outcome and deleterious effects on normal physiological functions. A greater understanding of the role of SDF-1 and CXCR4 in the body will allow greater manipulation of this important biological axis to affect disease outcome. Greater knowledge of the SDF-1 interaction with its receptor and the structural elements within CXCR4 mediating the different signalling events, resulting in SDF-1-induced responses, will also enhance future drug design.