PP2A-activating drugs selectively eradicate TKI-resistant chronic myeloid leukemic stem cells
Paolo Neviani, … , Guido Marcucci, Danilo Perrotti
Paolo Neviani, … , Guido Marcucci, Danilo Perrotti
Published September 3, 2013
Citation Information: J Clin Invest. 2013;123(10):4144-4157. https://doi.org/10.1172/JCI68951.
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Research Article Oncology

PP2A-activating drugs selectively eradicate TKI-resistant chronic myeloid leukemic stem cells

Abstract

The success of tyrosine kinase inhibitors (TKIs) in treating chronic myeloid leukemia (CML) depends on the requirement for BCR-ABL1 kinase activity in CML progenitors. However, CML quiescent HSCs are TKI resistant and represent a BCR-ABL1 kinase–independent disease reservoir. Here we have shown that persistence of leukemic HSCs in BM requires inhibition of the tumor suppressor protein phosphatase 2A (PP2A) and expression — but not activity — of the BCR-ABL1 oncogene. Examination of HSCs from CML patients and healthy individuals revealed that PP2A activity was suppressed in CML compared with normal HSCs. TKI-resistant CML quiescent HSCs showed increased levels of BCR-ABL1, but very low kinase activity. BCR-ABL1 expression, but not kinase function, was required for recruitment of JAK2, activation of a JAK2/β-catenin survival/self-renewal pathway, and inhibition of PP2A. PP2A-activating drugs (PADs) markedly reduced survival and self-renewal of CML quiescent HSCs, but not normal quiescent HSCs, through BCR-ABL1 kinase–independent and PP2A-mediated inhibition of JAK2 and β-catenin. This led to suppression of human leukemic, but not normal, HSC/progenitor survival in BM xenografts and interference with long-term maintenance of BCR-ABL1–positive HSCs in serial transplantation assays. Targeting the JAK2/PP2A/β-catenin network in quiescent HSCs with PADs (e.g., FTY720) has the potential to treat TKI-refractory CML and relieve lifelong patient dependence on TKIs.

Authors

Paolo Neviani, Jason G. Harb, Joshua J. Oaks, Ramasamy Santhanam, Christopher J. Walker, Justin J. Ellis, Gregory Ferenchak, Adrienne M. Dorrance, Carolyn A. Paisie, Anna M. Eiring, Yihui Ma, Hsiaoyin C. Mao, Bin Zhang, Mark Wunderlich, Philippa C. May, Chaode Sun, Sahar A. Saddoughi, Jacek Bielawski, William Blum, Rebecca B. Klisovic, Janelle A. Solt, John C. Byrd, Stefano Volinia, Jorge Cortes, Claudia S. Huettner, Steffen Koschmieder, Tessa L. Holyoake, Steven Devine, Michael A. Caligiuri, Carlo M. Croce, Ramiro Garzon, Besim Ogretmen, Ralph B. Arlinghaus, Ching-Shih Chen, Robert Bittman, Peter Hokland, Denis-Claude Roy, Dragana Milojkovic, Jane Apperley, John M. Goldman, Alistair Reid, James C. Mulloy, Ravi Bhatia, Guido Marcucci, Danilo Perrotti

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Figure 3

BCR-ABL1 activity, but not its expression, is low in CML quiescent stem cells.

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BCR-ABL1 activity, but not its expression, is low in CML quiescent stem ...
(A) Annexin-V/7-AAD staining shows percent apoptotic CD34+ CML progenitors and CFSEmaxCD34+ TKI-resistant quiescent CML cells upon exposure to FTY720 and imatinib, alone or in combination. (B) Active BCR-ABL1 (pABLY245) levels in CFSEmaxCD34+ and CD34+ cells from untreated and FTY720- or imatinib-treated CML samples. A representative flow cytometry histogram overlay is also shown. (C) Left: Gating strategy to isolate quiescent CFSEmaxCD34+ cells versus dividing CD34+ cells and their CD34-CD38 flow profile. Middle and right: BCR-ABL1 activity (α-pY) and protein (α-Abl). mRNA levels (relative to K562 cells) in FACS-sorted quiescent (CFSEmax) cells were compared with dividing (Div1 and Div2) CD34+ CML cells. Actin levels were detected as a control. *P < 0.05, **P < 0.01, Student’s t test.