Elevated frequencies of leukemic myeloid and plasmacytoid dendritic cells in acute myeloid leukemia with the FLT3 internal tandem duplication

Abstract

Some 30% of acute myeloid leukemia (AML) patients display an internal tandem duplication (ITD) mutation in the FMS-like tyrosine kinase 3 (FLT3) gene. FLT3-ITDs are known to drive hematopoietic stem cells towards FLT3 ligand independent growth, but the effects on dendritic cell (DC) differentiation during leukemogenesis are not clear. We compared the frequency of cells with immunophenotype of myeloid DC (mDC: Lin−, HLA-DR+, CD11c+, CD86+) and plasmacytoid DC (pDC: Lin−, HLA-DR+, CD123+, CD86+) in diagnostic samples of 47 FLT3-ITD− and 40 FLT3-ITD+ AML patients. The majority of ITD+ AML samples showed high frequencies of mDCs or pDCs, with significantly decreased HLA-DR expression compared with DCs detectable in ITD− AML samples. Interestingly, mDCs and pDCs sorted out from ITD+ AML samples contained the ITD insert revealing their leukemic origin and, upon ex vivo culture with cytokines, they acquired DC morphology. Notably, mDC/pDCs were detectable concurrently with single lineage mDCs and pDCs in all ITD+ AML (n = 11) and ITD− AML (n = 12) samples analyzed for mixed lineage DCs (Lin−, HLA-DR+, CD11c+, CD123+). ITD+ AML mDCs/pDCs could be only partially activated with CD40L and CpG for production of IFN-α, TNF-α, and IL-1α, which may affect the anti-leukemia immune surveillance in the course of disease progression.

Monitoring dendritic cell and cytokine biomarkers during remission prior to relapse in patients with FLT3-ITD acute myeloid leukemia

“…These leukemic DCs contained ITD mutations and could be driven to differentiate into mature mDCs or pDCs in vitro upon culture with cytokines, but they were not fully capable of secreting several cytokines [14]. We therefore deduced that CD11c + , CD123 + , and CD11c + /CD123 + leukemic DCs were arrested in the dendritic cell differentiation pathway and that CD11c + and CD123 + should be rather considered as DC precursor markers.…”

“…Incomplete regeneration of DC populations in leukemia patients after stem cell transplantation has also been described in the literature as a negative prognostic factor [25, 26]. We have previously demonstrated that the presence of the ITD mutation in AML was correlated with an aberrant accumulation of cells with hallmarks of arrested dendritic cells [14]. We hypothesized that constitutive signaling through FLT3-ITD could arrest MRD leukemic dendritic cell precursors in an immature stage.…”

“…The DC compartment in cancer patients is often deregulated, resulting in the accumulation of immature and/or dysfunctional DCs [13]. We have recently shown that FD samples of adult ITD + AML patients contain an aberrant accumulation of cells with immunophenotypic and functional characteristics of arrested DCs [14]. Thus, we hypothesize that residual leukemic ITD + DCs could potentially affect the differentiation of normal DCs of patients during disease recovery through paracrine mechanisms.…”

TLR9-mediated siRNA delivery for targeting of normal and malignant human hematopoietic cells in vivo

“…47 Recent studies revealed that APCs such as pDCs play a tumor-promoting role in MM patients 48 and potentially also in AML patients. 49 CpG(A)-STAT3 siRNA provides a new method for targeting abnormal human DC populations in the tumor microenvironment to restore antitumor immunity while reducing survival of TLR9 ϩ tumor cells. Our proof-of-principle studies combining CpG-Stat3 siRNA with local radiotherapy have demonstrated that targeting both tumor and the tumor microenvironment is effective against radiation-resistant mouse BCL.…”

Lentivirus-Induced Dendritic Cells for Immunization Against High-Risk WT1+ Acute Myeloid Leukemia

“…These patients are at very high risk of leukemia recurrence, and therefore the standard of care commonly includes hematopoietic stem cell transplantation (HSCT) and adoptive T-cell transfer (Schlenk et al, 2008;Bacher et al, 2009). Studies from our group with diagnostic and remission samples obtained from FLT3-ITD patients showed a deregulated dendropoiesis, accumulation of dendritic cell precursors, and aberrant expression of inflammatory cytokines (Rickmann et al, 2011). Notably, FLT3-ITD occurrence has been correlated with WT1 overexpression (Spassov et al, 2011).…”