The axis of evil in the fight against cancer

Over the past years medicine has undergone intensive changes, evolving from classical semiology and internal medicine to individualized treatments, based on recent breakthroughs in immunology and genetics. This concept has had a profound impact in all medical specialties and as a consequence pharmacology and various treatment plans will be based on monoclonal antibodies and targeted cell therapies. One such target is the SDF-1-CXCR4 axis bacause it plays a critical role in many physiological processes that involve cell migration and cell fate decisions, ranging from stem cell homing, angiogenesis and neuronal development to immune cell trafficking. The chemokine receptor CXCR4 and its ligand stromal cell-derived factor 1alpha are also implicated in various pathological conditions, including metastatic spread and HIV infection. In this review, we present the concept that the SDF-1-CXCR4 axis is a master regulator of trafficking of both normal and cancer stem cells, based on the growing evidence that it plays a pivotal role in the regulation of trafficking of normal hematopoietic stem cells and their homing to the bone marrow. Because most malignancies originate in the progenitor cell compartment, cancer stem cells also express CXCR4 on their surface and migrate to organs that highly express SDF-1. Hence, we postulate that the metastasis of cancer stem cells and trafficking of normal stem cells involve similar mechanisms, which may be regulated by several small molecules related to inflammation. Consequently, strategies aimed at modulating the SDF-1-CXCR4 axis could have important clinical applications in both tissue engineering and in clinical hematology and oncology to inhibit metastasis of cancer stem cells.