GLI2 inhibition abrogates human leukemia stem cell dormancy

Anil Sadarangani, Gabriel Pineda, Kathleen M. Lennon, Hye Jung Chun, Alice Shih, Annelie E. Schairer, Angela C. Court, Daniel J. Goff, Sacha L. Prashad, Ifat Geron, Russell Wall, John D. McPherson, Richard A. Moore, Minya Pu, Lei Bao, Amy Jackson-Fisher, Michael Munchhof, Todd VanArsdale, Tannishtha Reya, Sheldon R. MorrisMark D. Minden, Karen Messer, Hanna K.A. Mikkola, Marco A. Marra, Thomas J. Hudson, Catriona H.M. Jamieson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

68 Scopus citations

Abstract

Background: Dormant leukemia stem cells (LSC) promote therapeutic resistance and leukemic progression as a result of unbridled activation of stem cell gene expression programs. Thus, we hypothesized that 1) deregulation of the hedgehog (Hh) stem cell self-renewal and cell cycle regulatory pathway would promote dormant human LSC generation and 2) that PF-04449913, a clinical antagonist of the GLI2 transcriptional activator, smoothened (SMO), would enhance dormant human LSC eradication. Methods: To test these postulates, whole transcriptome RNA sequencing (RNA-seq), microarray, qRT-PCR, stromal co-culture, confocal fluorescence microscopic, nanoproteomic, serial transplantation and cell cycle analyses were performed on FACS purified normal, chronic phase (CP) chronic myeloid leukemia (CML), blast crisis (BC) phase CML progenitors with or without PF-04449913 treatment. Results: Notably, RNA-seq analyses revealed that Hh pathway and cell cycle regulatory gene overexpression correlated with leukemic progression. While lentivirally enforced GLI2 expression enhanced leukemic progenitor dormancy in stromal co-cultures, this was not observed with a mutant GLI2 lacking a transactivation domain, suggesting that GLI2 expression prevented cell cycle transit. Selective SMO inhibition with PF-04449913 in humanized stromal co-cultures and LSC xenografts reduced downstream GLI2 protein and cell cycle regulatory gene expression. Moreover, SMO inhibition enhanced cell cycle transit and sensitized BC LSC to tyrosine kinase inhibition in vivo at doses that spare normal HSC. Conclusion: In summary, while GLI2, forms part of a core HH pathway transcriptional regulatory network that promotes human myeloid leukemic progression and dormant LSC generation, selective inhibition with PF-04449913 reduces the dormant LSC burden thereby providing a strong rationale for clinical trials predicated on SMO inhibition in combination with TKIs or chemotherapeutic agents with the ultimate aim of obviating leukemic therapeutic resistance, persistence and progression.

Original languageEnglish
Article number98
Pages (from-to)1
Number of pages1
JournalJournal of Translational Medicine
Volume13
Issue number1
DOIs
StatePublished - 12 Dec 2015
Externally publishedYes

Bibliographical note

Funding Information:
We are indebted to Dr. Dennis Carson for his indispensable advice as well as Kimberly Booth and Leisa Sutton for invaluable assistance with manuscript preparation. We would also like to thank Maria Sierra, Masaya Ueno and Yanling Wang for assistance with LSC experiments. We acknowledge expert technical assistance from the Library and Sequencing Cores at the Canada’s Michael Smith Genome Sciences Centre. PF-04449913 was provided through a MTA with Pfizer Inc. CHMJ, DJG and this research were supported by California Institute for Regenerative Medicine grants (RN2-00910-1, RS1-00228-1 DR1-01430, TG2-01154), Cancer Stem Cell Consortium funding from Genome Canada and the Ontario Genomics Institute (OGI-047); NIH NIGMS 5K12GM068524; NIH NCI 2P30CA023100-28; The Sanford Stem Cell Clinical Center; The San Diego Foundation; The Ratner Family Foundation; The Mizrahi Family Foundation; and the Canadian Institute of Health Research (CSC-105367). The authors wish to thank the Genome Sciences Centre Library Construction, Sequencing and Bioinformatics teams (BC Cancer Agency) and the UC San Diego Cancer Biology Training Grant. GP was supported by 5K12GM068524 from the NIGMS. SLP is a Howard Hughes Medical Institute Gilliam fellow. This work was also funded by the Ontario Institute for Cancer Research, through generous support from the Ontario Ministry of Research and Innovation and the Cancer Stem Cell Consortium with funding from Genome Canada, Genome British Columbia, the Ontario Genomics Institute (OGI-047), and the Canadian Institute of Health Research (CSC-105367).

Publisher Copyright:
© 2015 Sadarangani et al.; licensee BioMed Central.

Keywords

  • Cell cycle
  • GLI2
  • Leukemia stem cells
  • PF-04449913
  • Smoothened SMO
  • Sonic hedgehog

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