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 6

FTY720 suppresses mouse BCR-ABL1+ LT-HSC and human CML stem and progenitor cell survival in vivo.

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FTY720 suppresses mouse BCR-ABL1+ LT-HSC and human CML stem and progenit...
(A) Transplantation of BCR-ABL1/GFP+ cells derived from transgenic BCR-ABL1-tg/GFP mice into primary and secondary recipients. (B) Effect of FTY720 (4 weeks) on the absolute numbers of GFP+(leukemic) LSK cells and LT-HSCs in mice transplanted with leukemic BM cells. (C) Xenotransplantation of human CML-BC and UCB CD34+ cells into NSG mice. (D) Percent hCD45+ cells, hCD34+ progenitors, and hCD34+CD38– HSC-enriched cell fraction in a representative CML xenotransplanted NSG mouse before and after 4 weeks of FTY720 treatment. Also shown are levels of hCD45+, hCD34+, and hCD34+CD38– cells in BM aspirated at time of engraftment (time 0) and after 8 weeks in untreated and FTY720-treated NSG mice (8–10 per group) intrafemorally transplanted with CD34+ cells from CML-BC patients (n = 3). (E) Frequency of cells as in D, but with CD34+ cells transplanted from UCB donors (n = 3). (F) qRT-PCR–mediated analysis of BCR-ABL1 transcripts in BM aspirates of CML-engrafted mice left untreated or treated with FTY720. Also shown is a representative cell of BCR-ABL1 interphase FISH on FACS-sorted hCD45+ cells from BM aspirates of untreated and 4-week FTY720-treated mice. Original magnification, ×1,000. *P < 0.05, **P < 0.01, ***P < 0.001, Student’s t test.