title: Circulation of CD34+ hematopoietic stem cells in the peripheral blood of high-dose cyclophosphamide-treated patients: enhancement by intravenous recombinant human granulocyte-macrophage colony-stimulating factor.
abstract: We report that hematopoietic progenitor cells expressing the CD34 antigen (CD34+ cells) transiently circulate in the peripheral blood (PB) of cancer patients treated with 7 g/m2 cyclophosphamide (HD-CTX) with or without recombinant human granulocyte macrophage-colony stimulating factor (rHuGM-CSF). In adult humans, CD34+ cells represent a minor fraction (1% to 4%) of bone marrow (BM) cells, comprising virtually all hematopoietic colony-forming progenitors in vitro and probably also stem cells capable of restoring hematopoiesis of lethally irradiated hosts. We show that CD34+ cell circulation is fivefold enhanced by rHuGM-CSF 5.5 protein micrograms/kg/day by continuous intravenous infusion for 14 days after HD-CTX. During the third week after HD-CTX (ie, when CD34+ cells peak in the circulation), large-scale collection of PB leukocytes by three to four continuous-flow leukaphereses allows the yield of 2.19 to 2.73 x 10(9) or 0.45 to 0.56 x 10(9) CD34+ cells depending on whether or not patients receive rHuGM-CSF. The number of CD34+ cells retrieved from the circulation by leukaphereses exceeds the number that can be harvested by multiple BM aspirations under general anesthesia. Thus, after therapy with HD-CTX and rHuGM-CSF, PB represents a rich source of hematopoietic progenitors possibly usable for restoring hematopoiesis after myeloablative chemoradiotherapy. To determine whether CD34+ cells found in the PB are equivalent to their marrow counterpart, we evaluated their in vitro growth characteristics and immunological phenotype by colony assays and dual-color immunofluorescence, respectively. We show that PB CD34+ cells possess qualitatively normal hematopoietic colony growth and high cloning efficiency comparable to that observed with BM CD34+ cells. In addition, PB CD34+ cells display heterogeneous surface membrane differentiation antigens analogous to BM CD34+ cells. The availability of large quantities of CD34+ cells by leukapheresis is relevant to the field of stem cell transplantation and possibly to genetic manipulations of the hematopoietic system in humans.
authors: Cristina Gandini Transplantation Unit, Istituto Nazionale Tumori, Milan, Italy.
authors: S
authors: S
authors: Siena
authors: M
authors: M
authors: Bregni
authors: B
authors: B
authors: Brando
authors: F
authors: F
authors: Ravagnani
authors: G
authors: G
authors: Bonadonna
authors: A M
authors: AM
authors: Gianni
mesh_terms: D018952:Antigens, CD34; D000943:Antigens, Differentiation; D015214:Antigens, Differentiation, Myelomonocytic; D001773:Blood Cells; D001854:Bone Marrow Cells; D018826:CD13 Antigens; D002455:Cell Division; D003114:Colony-Forming Units Assay; D003115:Colony-Stimulating Factors / Q000627:therapeutic use*; D003520:Cyclophosphamide / Q000008:administration & dosage*; D005434:Flow Cytometry; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006133:Growth Substances / Q000627:therapeutic use*; D006684:HLA-DR Antigens / Q000032:analysis; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007937:Leukapheresis; D011994:Recombinant Proteins; D013997:Time Factors
chemical_list: D018952:Antigens, CD34; D000943:Antigens, Differentiation; D015214:Antigens, Differentiation, Myelomonocytic; D003115:Colony-Stimulating Factors; D006133:Growth Substances; D006684:HLA-DR Antigens; D011994:Recombinant Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D003520:Cyclophosphamide; D018826:CD13 Antigens