Interactions of monocyte subpopulations generated from cord blood CD34(+) hematopoietic progenitors with tumor cells: assessment of antitumor potential

The monoculture of cord-blood-derived CD34+ cells by an automated, membrane-based dynamic perfusion system with a novel cytokine cocktail

Human leukocyte antigen (HLA)-matched cord blood (CB) transplantation is a procedure for the treatment of certain hematological malignancies, hemoglobinopathies, and autoimmune disorders. However, one of the challenges is to provide a sufficient number of T cell-depleted hematopoietic stem and progenitor cells. Currently, only 4%-5% of the CB units stored in CB banks contain enough CD34⁺ cells for engrafting 70-kg patients. To support this clinical need, we have developed an automated expansion protocol for CB-derived CD34⁺ cells in the Quantum system's dynamic perfusion bioreactor using a novel cytokine cocktail comprised of stem cell factor (SCF), thrombopoietin (TPO), fms-like tyrosine kinase 3 ligand (Flt-3L), interleukin-3 (IL-3), IL-6, glial cell line-derived neurotrophic factor (GDNF), StemRegenin 1 (SR-1), and a fibronectin-stromal-cell-derived factor-1 (SDF-1)-coated membrane. In an 8-day expansion of a 2 × 10⁶ positively selected CD34⁺ cell inoculum from 3 donor lineages, the mean cell harvest and cell viability were 1.02 × 10⁸ cells and 95.5%, respectively, and the mean frequency of the CD45⁺CD34⁺ immunophenotype was 54.3%. The mean differentiated cell frequencies were 0.5% for lymphocytes, 15.8% for neutrophils, and 15.4% for platelets. These results demonstrate that the automated monoculture protocol can support the expansion of CD34⁺ cells with minimal lymphocyte residual.

Properties of monocytes generated from haematopoietic CD34(+) stem cells from bone marrow of colon cancer patients

Monocytes exhibit direct and indirect antitumour activities and may be potentially useful for various forms of adoptive cellular immunotherapy of cancer. However, blood is a limited source of them. This study explored whether monocytes can be obtained from bone marrow haematopoietic CD34(+) stem cells of colon cancer patients, using previously described protocol of expansion and differentiation to monocytes of cord blood-derived CD34(+) haematopoietic progenitors. Data show that in two-step cultures, the yield of cells was increased approximately 200-fold, and among these cells, up to 60 % of CD14(+) monocytes were found. They consisted of two subpopulations: CD14(++)CD16(+) and CD14(+)CD16(-), at approximately 1:1 ratio, that differed in HLA-DR expression, being higher on the former. No differences in expression of costimulatory molecules were observed, as CD80 was not detected, while CD86 expression was comparable. These CD14(+) monocytes showed the ability to present recall antigens (PPD, Candida albicans) and neoantigens expressed on tumour cells and tumour-derived microvesicles (TMV) to autologous CD3(+) T cells isolated from the peripheral blood. Monocytes also efficiently presented the immunodominant HER-2/neu369-377 peptide (KIFGSLAFL), resulting in the generation of specific cytotoxic CD8(+) T lymphocytes (CTL). The CD14(++)CD16(+) subset exhibited enhanced cytotoxicity, though nonsignificant, towards tumour cells in vitro. These observations indicate that generation of monocytes from CD34(+) stem cells of cancer patients is feasible. To our knowledge, it is the first demonstration of such approach that may open a way to obtain autologous monocytes for alternative forms of adaptive and adoptive cellular immunotherapy of cancer.