CYTOKINE ENHANCEMENT OF PERIPHERAL-BLOOD STEM-CELLS

The use of cytokines to improve peripheral blood stem cell enhancement and recruitment has recently received close attention. Three main cyt okines have been, or are still being, investigated in this way in huma n clinical trials so far: recombinant human granulocyte-macrophage col ony stimulating factor (rhGM-CSF), granulocyte CSF (rhG-CSF) and inter leukin 3 (IL-3). While cytokines used alone appear undoubtedly capable of a marked peripheral blood stem cell (PBSC) enhancement, their comb ination with a chemotherapy priming often increases this phenomenon. T his is particularly evident with rhIL-3, which is an earlier acting cy tokine than rhGM-CSF and rhG-CSF. rhIL-3 priming alone leads to only a minor elevation of circulating progenitor cells, while its combinatio n with chemotherapy and/or a late acting cytokine may allow enhancemen t and recruitment of large amounts of PBSC. The effect of cytokines on PBSC enhancement may also be at least partially thwarted by various f actors. Additionally, their adequate dosage often remains uncertain. S o it is presently too early to determine what is actually the most app ropriate cytokine or cytokine combination to improve PBSC enhancement. Also the risk of stimulation of tumor clonogenic cells in some malign ant diseases remains, and the experimenters should be as cautious as p ossible to not jeopardize the patients' safety.