['Transplantation of hematopoietic progenitor stem cells (HPC) is an important treatment modality for a variety of neoplastic diseases. HPC collection for transplantation with granulocyte colony-stimulating factor may be unsuccessful in patients who have received prior chemotherapy or for other reasons. Methods to improve mobilization of HPCs are required. Disruption of the interaction between the cell surface receptor CXCR4 and its ligand stromal derived factor-1 (SDF-1) is a mechanism for HPC release from the bone marrow into the peripheral blood (PB).', 'We carried out a clinical trial to evaluate the effects of ingestion of a fucoidan, galactofucan sulfate (a putative HPC mobilizing agent) on circulating CD34(+) cells, CXCR4 expression, and levels of SDF-1, interferon gamma (IFN-gamma) and interleukin 12.', 'Following ingestion of fucoidan, CD34(+) cells increased significantly in the PB from 1.64 to 1.84 cells/microL after 4 days. The proportion of CD34(+) cells that expressed CXCR4 increased from 45 to 90% after 12 days, the plasma level of SDF-1 increased from 1978 to 2010 pg/mL, and IFN-gamma level increased from 9.04 to 9.89 pg/mL.'] Does fucoidan ingestion increase the expression of CXCR4 on human CD34+ cells?