Differentiation of acute and chronic myeloid leukemic blasts into the dendritic cell lineage: analysis of various differentiation-inducing signals.
OBJECTIVE
Ex vivo differentiation of myeloid leukemic blasts into dendritic cells (DCs) holds significant promise for use as cellular vaccines, as they may present a constellation of endogenously expressed known and unknown leukemia antigens to the immune system. Although variety of stimuli can drive leukemia --> DC differentiation in vitro, these blast-derived DCs typically have aberrant characteristics compared with DCs generated from normal progenitors by the same stimuli. It is not clear whether this is due to underlying leukemogenic mechanisms (e.g., specific oncogenes), genetic defects, stage of maturation arrest, defects in cytokine receptor expression or signal transduction pathways, or whether different stimuli themselves induce qualitatively dissimilar DC differentiation.


METHODS
To assess what factors may contribute to aberrant leukemic blast --> DC differentiation, we have examined how the same leukemic blasts (AML and CML) respond to different DC differentiation signals--including extracellular (the cytokine combination GM-CSF + TNF-alpha + IL-4) and intracellular (the protein kinase C agonist PMA, the calcium ionophore A23187, and the combination of PMA plus A23187) stimuli.


RESULTS
We have found that the same leukemic blasts will develop qualitatively different sets of DC characteristics in response to differing stimuli, although no stimuli consistently induced all of the characteristic DC features. There were no clear differences in the responses relative to specific oncogene expression or stage of maturation arrest (AML vs CML). Signal transduction agonists that bypassed membrane receptors/proximal signaling (in particular, the combination of PMA and A23187) consistently induced the greatest capability to activate T cells. Interestingly, this ability did not clearly correlate with expression of MHC/costimulatory ligands.


CONCLUSIONS
Our findings suggest that signal transduction may play an important role in the aberrant DC differentiation of leukemic blasts, and demonstrate that direct activation of PKC together with intracellular calcium signaling may be an effective method for generating immunostimulatory leukemia-derived DCs.
Kharfan-Dabaja
Mohamed
M
Division of Hematology/Oncology, Department of Medicine, University of Miami, Miami, FL 33136, USA.
Ayala
Ernesto
E
Lindner
Inna
I
Cejas
Pedro J
PJ
Bahlis
Nizar J
NJ
Kolonias
Despina
D
Carlson
Louise M
LM
Lee
Kelvin P
KP
D000954:Antigens, Surface / Q000235:genetics; D001752:Blast Crisis / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D019070:Cell Lineage / Q000235:genetics / Q000276:immunology; D049109:Cell Proliferation; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D010641:Phenotype; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology / Q000502:physiology
D000954:Antigens, Surface