A neutralizing anti-TGF-beta1 antibody promotes proliferation of CD34+Thy-1+ peripheral blood progenitors and increases the number of transduced progenitors.

The subset of blood cells that expresses both CD34 and Thy1 (CD90) cell surface molecules is enriched in hematopoietic stem cell activity and can be obtained from the peripheral blood of cancer patients after mobilization by chemotherapy and granulocyte colony-stimulating factor (G-CSF). Because transforming growth factor-beta1 (TGF-beta1) is a potent inhibitor of hematopoietic progenitor proliferation and differentiation, in this study we analyzed the impact of neutralizing TGF-beta1 activity during culture and retroviral transduction of CD34+Thy1+ cells. When purified CD34+Thy1+ cells were cultured in the presence of a neutralizing antibody against TGF-beta1, the percentage of cycling cells, proliferation, and absolute number of clonogenic progenitors were increased in comparison to the cultures performed without the addition of antibody. Antibody-mediated neutralization of TGF-beta1 during retroviral transduction performed by coculture of CD34+Thy1+ cells with a MFG-S-nlsLacZ retroviral vector-producing cell line did not affect the percentage of transduced progenitors as assessed by direct X-Gal staining of colonies in clonogenic assays. However, due to the better expansion of CD34+Thy1+ cells in the presence of anti-TGF-beta1, the absolute number of transduced progenitors recovered at the end of the culture was increased.