Flt3 ligand and thrombopoietin serum levels during peripheral blood stem cell mobilization with chemotherapy and recombinant human glycosylated granulocyte colony-stimulating factor (rhu-G-CSF, lenograstim) and after high-dose chemotherapy.

The purpose of this investigation was to study thrombopoietin (TPO) and Flt3 ligand (FL) serum levels in the course of peripheral blood stem cell (PBSC) mobilization and high-dose chemotherapy (HDC) and to correlate the values with stem cell yield and engraftment. Thirty-nine patients were included. PBSC were mobilized by chemotherapy followed by two body surface area-dependent doses of glycosylated recombinant human granulocyte colony-stimulating factor (rhu-G-CSF, lenograstim). PBSC could be harvested in 35 patients and 30 received a total of 62 courses of HDC (1-3 per patient). Fifty-six were analyzed and TPO and FL serum levels were measured at the start of PBSC mobilization, at the first PBSC collection, on the day of PBSC infusion, and until engraftment. Mean baseline TPO and FL serum levels were 173 pg/ml and 192 pg/ml and increased to 493 and 323 pg/ml at the start of PBSC collection. Maximum values were 2279 pg/ml TPO after HDC 1 and 2375 pg/ml after HDC 2, while the mean maximum serum levels for FL were 1181 and 1236 pg/ml after HDC 1 and 2 and PBSC transfusion, respectively. FL serum levels at the start of PBSC mobilization correlated with the total yield of CD34+ cells (17.61+/-18.8x10(6)/kg body weight, r=0.81), while TPO serum levels on days 11-13 after PBSC infusion were inversely correlated with the amount of transfused CD34+61+62+ cells (r=-0.88 and -0.79 for HDC 1 and 2). There was no strong correlation between TPO or FL serum levels and WBC and platelet engraftment. In conclusion, chemotherapy followed by glycosylated rhu-G-CSF induced elevated serum levels of TPO and to a lower degree of FL at the start of PBSC collection. The maximum increase was 13.7-fold for TPO and 6.4-fold for FL after PBSC infusion indicating endogenous release which should be considered if the clinical use of these cytokines is intended in this setting.