Interactions of Monocyte Subpopulations Generated from Cord Blood CD34(+) Hematopoietic Progenitors with Tumor Cells: Assessment of Antitumor Potential

Monocytes and their subsets (CD14(++)CD16(+) and CD14(+)CD16(-)) generated from cord blood CD34(+) progenitor cells were used for determination of their capacity to interact with tumor cells in vitro and in vivo. The studies in vitro included adhesion to human umbilical vein endothelial cells, cytotoxicity, production of toxic mediators: reactive oxygen and nitrogen intermediates (ROI and RNI, respectively), and finally their effect on transplantable human tumor growth in nonobese diabetic severe combined immunodeficient mice. The CD14(++)CD16(+) subset exhibited an increased adherence to human umbilical vein endothelial cells and cytotoxicity toward tumor cells in vitro. CD14(+)CD16(-) monocytes showed a higher production of reactive oxygen and nitrogen intermediates after stimulation with tumor cells, and more pronounced inhibition of tumor growth in vivo. The results revealed significant differences in the behavior of CD14(++)CD16(+) and CD14(+)CD16(-) monocyte subsets toward tumor cells, thus providing further evidence that CD34(+) cell-derived monocytes differ in this respect from blood monocytes. The protocol for generation of monocytes with antitumor reactivity described here may be useful to obtain monocytes from CD34(+) progenitor cells of cancer patients. This might offer a basis for a novel approach for various forms of cellular immunotherapy of cancer.