Background & objective: Dendritic cells (DCs) or DC-like cells had been successfully induced in vitro from leukemia cells, which may provide a promising immunotherapeutic protocol for leukemia. This study was designed to investigate the efficiency of in vitro generation of dendritic cells from CD14+ acute myelomonocytic (M4) or monocytic (M5) leukemia cells and their ability of stimulating specific antileukemia T-cell response.
Methods: Bone marrow mononuclear cells (BMMNCs) were isolated from 5 M4/M5 leukemia patients with high CD14 expression, and then divided into 3 groups: adherent leukemia cells, nonadherent blasts, and total unfractioned blasts. CD14 expression of the 3 groups was evaluated by flow cytometry (FCM). When cultured with or without granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-4 (IL-4) and tumor necrosis factor alpha (TNF-alpha) for 7-10 days, monocytic leukemia cell-derived dendritic cells (Mo-LDCs) were identified through morphologic observation and immunophenotype analysis using FCM. The immune function of Mo-LDCs was detected through allogeneic mixed lymphocyte reaction (Allo-MLR) and cytotoxicity assay of antileukemia cytotoxic T lymphocytes (CTLs). The leukemic origin of Mo-LDCs was confirmed by chromosomal karyotype analysis combined with the aberrant expression of myeloid antigens.
Results: The amount of CD14+ cells, which could differentiate into CD83+ mature DCs under induction of the cytokine combination, was higher in adherent leukemia cells than in nonadherent blasts and total unfractioned blasts. Regarding each 3 cell groups of the same patient or the unfractioned blasts of various patients, initial CD14 expression was positively related to the yield of CD83+ DCs after induction (r = 0.967, P = 0.007). Mo-LDCs exhibited typical morphology and phenotype as mature DCs, induced potent proliferation of homogeneous T cells in Allo-MLR, stimulated the expansion of leukemia-specific CTLs, and continued to possess the cytogenetic abnormalities of the original leukemia, as well as the aberrant expression of myeloid antigens.
Conclusions: In M4/M5 subtype of AML, CD14+ cells could differentiate into immune-competent Mo-LDCs under the induction of the cytokine combination. CD14 expression level may predict the DCs differentiation ability of monocytic leukemia. Mo-LDCs, which possess the classical phenotype and function of DCs, as well as the abnormal leukemic antigens, may be useful for the immunotherapy of M4/M5 AML.