Dipeptide γ-d-Glu-d-Trp (thymodepressin) inhibits migration of Cd34⁺ cells from the bone marrow into peripheral blood during tumor growth

We studied the effect of dipeptide γ-d-Glu-d-Trp (thymodepressin) on migration of CD34⁺ hemopoietic precursors and their direct adhesion to fibronectin in tumor-bearing mice on days 8, 11, 15, and 17 of tumor growth and on expression of CXCR-4 (CD184⁺) to SDF-1 and integrin β₁ (CD29⁺) by bone marrow cells. In tumor-bearing mice treated with γ-d-Glu-d-Trp, the percent of CD34⁺ hemopoietic precursors in the peripheral blood considerably decreased throughout the observation period; the content of CD34⁺ hemopoietic precursors in the tumor tissue was 2-3-fold below the control against the background of increased content of CD34⁺ cells in the bone marrow. In animals treated with the peptide, the content of cells expressing CXCR-4 in the peripheral blood, bone marrow, and tumor tissue significantly decreased, while the percent of cells expressing integrin β₁ receptor (CD29⁺) in the bone marrow increased 2-fold, which was paralleled by an almost 2-fold increase in the percent of cells binding to fibronectin. We hypothesized that dipeptide γ-d-Glu-d-Trp suppressed mobilization/migration of CD34⁺ hemopoietic precursor cells from the bone marrow to the peripheral blood of tumor-bearing mice.