Increased presence of CD34+ cells in the peripheral blood of head and neck cancer patients and their differentiation into dendritic cells.

Patients with head and neck squamous cell carcinoma (HNSCC) have profound immune deficiencies. In 65% of these patients, there is an increased intra-tumoral presence of immune-suppressive CD34+ progenitor cells. The goal of the present study was to determine whether CD34+ cell levels were also increased in the peripheral blood of HNSCC patients and if these immune-suppressive cells could be differentiated into dendritic cells. Our results showed that CD34+ cell levels are increased in the peripheral blood of HNSCC patients. To assess if these CD34+ cells could differentiate into dendritic cells, they were isolated from the blood of HNSCC patients and cultured for 12 days with various cytokine combinations. Culturing CD34+ cells with stem cell factor (c-kit ligand) plus granulocyte-macrophage colony-stimulating factor resulted in the appearance of a significant proportion of cells expressing phenotypic markers characteristic of dendritic cells. Also, including tumor necrosis factor-alpha yielded a significant proportion of cells resembling the bipotential precursor cells for dendritic cells and monocytes (CD14+CD1a+), in addition to the dendritic-like cells. When the differentiation inducer 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] was added along with the cytokine combinations, the yield of cells having characteristics of dendritic cells was further increased. Cells that were derived from CD34+ cell cultures containing 1,25(OH)2D3 had a more potent capacity to present the recall antigen tetanus toxoid to autologous peripheral blood leukocytes and to stimulate a mixed leukocyte response compared to cultures to which 1,25(OH)2D3 had not been added. Our results show that CD34+ cells, whose frequency is increased in HNSCC patients, can be differentiated into cells that phenotypically and functionally resemble dendritic cells and that 1,25(OH)2D3 accentuates this differentiation.