Targeting the Hedgehog Signaling Pathway by Glasdegib Limits the Self- Renewal of MDS-Derived Induced Potent Stem Cells (iPSC)

Abstract

Objective: Myelodysplastic syndromes (MDS) are clonal hematopoietic disorders characterized by no efficient hematopoiesis and frequent progression to acute myeloid leukemia (AML). Even in low risk MDS, clonal hematopoiesis already dominates at diagnosis, and clones found in secondary AML originate from the MDS stage of disease, highlighting the need to specifically target the MDS-initiating clone. Glasdegib is a potent and selective hedgehog pathway inhibitor that acts by binding Smoothened (SMO) and blocking signal transduction. Glasdegib demonstrated preliminary antitumor activity in a phase I trial, when given as monotherapy in patients with several hematopoietic malignancies. In the present study, we investigated the molecular mechanisms by which glasdegib regulate the self-renewal of MDS-derived iPS cells (iPSCs) in vivo. Methods:We generated iPSCs from bone marrow mononuclear cells of an MDS patient with chromosome 5 deletion and complex karyotypic abnormalities. We examined the activity of glasdegib against MDS-derived iPSCs transferred NOD/SCID mice in vivo and in vitro. We performed the serial in vivo transplantation to assess the effects of hedgehog inhibition on long term self-renewal. NOD/SCID mice were injected with MDS-iPSCs then treated with glasdegib. Results:We observed that glasdegib significantly reduced the self-renewal of NOD/SCID re-populating cells from MDS-derived iPSC during serial transplantation in vivo. Further, NOD/SCID mice were injected with MDS-iPSCs, and then treated with glasdegib on day 21 for 7 days. These treatments reduced the population of CD34+CD38-cells. To investigate the entire the apoptosis-induction pathways by hedgehog inhibition, MSD-L cells were incubated with 5-azacytidine and glasdegib for 72 hrs. Glasdegib enhanced the expression of cleaved PARP, cleaved caspase-3, p21 and reduced expression of c-Myc. Conclusion:Our pre-clinical results indicate that glasdegib have potential as an important option for controlling the drug-resistant MDS-initiating cells. It is expected that the glasdegib may become extremely useful therapeutic interventions in a number of hematological neoplasms, including MDS, where the persistence of cancer stem cells.

Hedgehog Pathway Inhibitors: A New Therapeutic Class for the Treatment of Acute Myeloid Leukemia

“…These findings have been corroborated in studies from samples of patients with AML (5)(6)(7)(8)(24)(25)(26)(27)(28)(29)(30). Upregulation of PTCH1, SMO, and the GLI TFs have been reported in patients with AML (24), and were associated with reduced event-free and overall survival (OS), both in de novo and secondary AML (26).…”

“…Glasdegib led to a reduction in the self-renewal of NOD/SCID repopulating cells and a reduction in the population of CD34 + CD38 − cells. In addition, glasdegib plus 5-azacytidine increased apoptosis induction in MSD-L cells (30).…”

“…In addition, it has also been suggested that Hh plays a role in early progenitors of myelodysplastic syndromes (MDS; ref. 30). Glasdegib led to a reduction in the self-renewal of NOD/SCID repopulating cells and a reduction in the population of CD34 + CD38 − cells.…”

Glasdegib plus low-dose cytarabine for acute myeloid leukemia: Practical considerations from advanced practitioners and pharmacists

“…17 Theoretically, therefore, glasdegib acts as a chemosensitizer of leukemic stem cells. Preclinical studies for glasdegib have supported this hypothesis, 18,19 and it follows that glasdegib should be used in combination with a cytotoxic agent.…”

Evaluation of the Relationship of Glasdegib Exposure and Safety End Points in Patients With Refractory Solid Tumors and Hematologic Malignancies

“…Glasdegib is a selective, orally administered smoothened inhibitor. It has demonstrated potent and selective inhibition of hedgehog signaling in vitro and significant antitumor efficacy in vivo 1–3 . Glasdegib has been investigated in clinical trials for selected solid tumors and advanced hematologic malignancies including acute myeloid leukemia (AML), chronic myeloid leukemia, chronic myelomonocytic leukemia, myelodysplastic syndrome (MDS), or myelofibrosis 4–10 .…”