VHL and neoplasm: Diverse external factors, such as hypoxia (hif-1-pathway) and the activation of adenosine receptors, as well as internal cellular alterations like the inactivation of tumour-suppressor genes pVHL, p53 or the overexpression of NFkB have been defined as important molecular regulators of the CXCR4 expression (Helbig et al, 2003; Staller et al, 2003; Mehata et al, 2004).