CXCR4 and cancer: To define the molecular mechanism by which stem cells migrate toward cancer cells, we isolated total RNA from hNSCs, HB1.F3, prostate cancer cells, and human dermal fibroblast (HDF) cells, and measured the mRNA levels of several chemoattractant ligands and receptors, including urokinase plasminogen activator and its receptor (uPA/uPAR), stem cell factor (SCF), and its receptors (c-Kit), SDF-1/CXCR4, monocyte chemotactic protein-1 (MCP-1) and its receptor (CCR2), VEGF, and VEGF-receptor 2 (VEGFR2), using quantitative real-time PCR.