Elevated transforming growth factor beta levels in the plasma of cytokine-treated cancer patients and normal allogeneic stem cell donors

Background: Allogeneic blood stem-cell donors demonstrate more vigorous mobilization of CD34⁺ cells to the circulation in response to cytokine administration than do autologous donors. Transforming growth factor (TGF-β1) has been implicated as a mobilization inhibitor. A study was designed to determine whether plasma TGF-β1 levels are elevated in cytokine-mobilized autologous cancer donors compared with cytokine-mobilized normal donors. Methods: Plasma collected from 29 autologous and cancer donors and 33 normal allogeneic stem-cell donors following administration of mobilizing cytokines just prior to the first collection was assayed for TGF-β1 using a sandwich-type ELISA. Plasma from three volunteers not treated with cytokine was also analyzed. Comparisons were made using the Student's t test on log-transformed data. Results: Average TGF-β1 levels in the plasma of cancer patients were significantly higher than in allogeneic stem-cell donors (4.4 ng/mL versus 7.2 ng/mL; p = 0.038). The allogeneic donors required fewer collections to harvest greater numbers of CD34⁺ cells and colony-forming unit granulocyte-macrophage (CFU-GM) than autologous donors. Plasma from three untreated volunteers had mean TGF-β1 levels of 0.36 ng/mL, with all three levels below the 25th percentile for allogeneic donors and the 5th percentile for cancer patients. Discussion: Cytokine administration was associated with increased plasma TGF-β1 levels. The levels were higher in cancer patients being mobilized for stem-cell collection than in allogeneic blood stem-cell donors. These differences could underlie the increased number of apheresis procedures required to harvest autologous graft products from cancer patients.