The sesquiterpene lactone parthenolide induces apoptosis of human acute myelogenous leukemia stem and progenitor cells - PubMed (original) (raw)

The sesquiterpene lactone parthenolide induces apoptosis of human acute myelogenous leukemia stem and progenitor cells

Monica L Guzman et al. Blood. 2005.

Abstract

Recent studies have described malignant stem cells as central to the initiation, growth, and potential relapse of acute and chronic myelogenous leukemia (AML and CML). Because of their important role in pathogenesis, rare and biologically distinct leukemia stem cells (LSCs) represent a critical target for therapeutic intervention. However, to date, very few agents have been shown to directly target the LSC population. The present studies demonstrate that parthenolide (PTL), a naturally occurring small molecule, induces robust apoptosis in primary human AML cells and blast crisis CML (bcCML) cells while sparing normal hematopoietic cells. Furthermore, analysis of progenitor cells using in vitro colony assays, as well as stem cells using the nonobese diabetic/severe combined immunodeficient (NOD/SCID) xenograft model, show that PTL also preferentially targets AML progenitor and stem cell populations. Notably, in comparison to the standard chemotherapy drug cytosine arabinoside (Ara-C), PTL is much more specific to leukemia cells. The molecular mechanism of PTL-mediated apoptosis is strongly associated with inhibition of nuclear factor kappa B (NF-kappaB), proapoptotic activation of p53, and increased reactive oxygen species (ROS). On the basis of these findings, we propose that the activity of PTL triggers LSC-specific apoptosis and as such represents a potentially important new class of drugs for LSC-targeted therapy.

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Figures

Figure 1.

Figure 1.

PTL induces apoptosis in CD34+CD38- AML cells but not in normal cells in a dose-dependent manner. In vitro cultures were maintained for 18 hours followed by analysis of viability using annexin-V labeling. Each plot shows the average percent cell viability for CD34+CD38- AML (A,C) and normal (N) cells (B,D) treated with increasing concentrations of PTL (A-B) or Ara-C (C-D). Each error bar represents the SD. All assays were performed in triplicate.

Figure 2.

Figure 2.

In vitro colony assays for AML and normal cells treated with PTL and Ara-C. AML versus normal cells in panels A and B were treated with 5 μM (formula image) or 7.5 μM PTL (formula image). AML versus normal cells in panels C and D were treated with 5 μM Ara-C (▪). All treatments were performed for 18 hours in suspension culture, followed by plating in methylcellulose culture. Error bars represent the SD. Average percent of colony-forming units (CFU) are normalized to untreated control (horizontal bar). All assays were performed in triplicate. Mye represents myeloid; Ery, erythroid.

Figure 3.

Figure 3.

PTL inhibits NOD/SCID repopulating ability for AML but not normal cells. Percentage of engraftment for NOD/SCID mice that received a transplant with AML (A) or normal CB (B) cells after 18 hours of culture with or without 7.5 μM PTL. Each • or ▴ represents a single animal analyzed at 6 to 8 weeks after transplantation. Each plot represents an AML/CB specimen. Mean engraftment is indicated by the horizontal bars.

Figure 4.

Figure 4.

NAC treatment abolishes PTL apoptosis induction in AML cells. Percent viability of CD34+ cells from 3 different AML specimens treated with increasing concentrations of PTL. Cells were precultured with 800 μM NAC (- - -) versus untreated controls (—) for 1 hour and immediately washed and treated with PTL for 18 hours. Specimens shown correspond to AML5 (□), AML10 (⋄) and AML15 (▵).

Figure 5.

Figure 5.

PGJ2 increases the sensitivity of leukemia cells to PTL. Average percent viability for CD34+CD38- cells normalized to untreated controls. Three AML, 3 bcCML, and 3 normal specimens were treated for 18 hours with 0.5 μM PGJ2 (formula image), 2.5 μM PTL (□), or both (formula image). Each error bar represents the SD. All assays were performed in triplicate.

Figure 6.

Figure 6.

Apoptosis induction by PTL or PTL/PGJ2 correlates to inhibition of NF-κB and increased phosphorylation of p53(ser15). (A) Percent viability and NF-κB electrophoretic mobility shift assay (EMSA) of a representative AML specimen treated with increasing concentrations of PTL alone (•) or in combination with 0.5 μM PGJ2 (▪). The viability is compared with and Ara-C (5μM; ♦) treatments. (B) Immunoblot analysis of phospho-p53(ser15) and actin for the same representative AML specimen treated with increasing dose of PTL 0.5 μM PGJ2.

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