MEF2C opposes Notch in lymphoid lineage decision and drives leukemia in the thymus
Kirsten Canté-Barrett, Mariska T. Meijer, Valentina Cordo’, Rico Hagelaar, Wentao Yang, Jiyang Yu, Willem K. Smits, Marloes E. Nulle, Joris P. Jansen, Rob Pieters, Jun J. Yang, Jody J. Haigh, Steven Goossens, Jules P.P. Meijerink
Kirsten Canté-Barrett, Mariska T. Meijer, Valentina Cordo’, Rico Hagelaar, Wentao Yang, Jiyang Yu, Willem K. Smits, Marloes E. Nulle, Joris P. Jansen, Rob Pieters, Jun J. Yang, Jody J. Haigh, Steven Goossens, Jules P.P. Meijerink
View: Text | PDF
Research Article Hematology Oncology

MEF2C opposes Notch in lymphoid lineage decision and drives leukemia in the thymus

Abstract

Rearrangements that drive ectopic MEF2C expression have recurrently been found in patients with human early thymocyte progenitor acute lymphoblastic leukemia (ETP-ALL). Here, we show high levels of MEF2C expression in patients with ETP-ALL. Using both in vivo and in vitro models of ETP-ALL, we demonstrate that elevated MEF2C expression blocks NOTCH-induced T cell differentiation while promoting a B-lineage program. MEF2C activates a B cell transcriptional program in addition to RUNX1, GATA3, and LMO2; upregulates the IL-7R; and boosts cell survival by upregulation of BCL2. MEF2C and the Notch pathway, therefore, demarcate opposite regulators of B- or T-lineage choices, respectively. Enforced MEF2C expression in mouse or human progenitor cells effectively blocks early T cell differentiation and promotes the development of biphenotypic lymphoid tumors that coexpress CD3 and CD19, resembling human mixed phenotype acute leukemia. Salt-inducible kinase (SIK) inhibitors impair MEF2C activity and alleviate the T cell developmental block. Importantly, this sensitizes cells to prednisolone treatment. Therefore, SIK-inhibiting compounds such as dasatinib are potentially valuable additions to standard chemotherapy for human ETP-ALL.

Authors

Kirsten Canté-Barrett, Mariska T. Meijer, Valentina Cordo’, Rico Hagelaar, Wentao Yang, Jiyang Yu, Willem K. Smits, Marloes E. Nulle, Joris P. Jansen, Rob Pieters, Jun J. Yang, Jody J. Haigh, Steven Goossens, Jules P.P. Meijerink

×

Figure 8

SIK inhibitors block MEF2C function.

Options: View larger image (or click on image) Download as PowerPoint
SIK inhibitors block MEF2C function. (A) Effects of the compounds from t...
(A) Effects of the compounds from the Selleck Epigenetic Compound Library and various additional inhibitors (1 μM) were screened for their potential to induce a CD3ε+ phenotype in LOUCY cells on DLL4-coated plates. As controls, media, non-DLL4–stimulated cells or MEF2C-overexpressing (LOUCY_MEF2C-BFP) cells (+dox) have been indicated in blue. Normalized CD3ε fluorescence intensities have been plotted for duplicate experiments. (B) SIK kinase inhibitors YKL-06-062 and HG-9-91-01; dasatinib, which has SIK off-target activity (12 nM, 48 nM, and 180 nM for SIK1, SIK2, or SIK3, respectively) (MedChemExpress or Proteomicsdb.org), and imatinib were tested to induce a CD3ε+ phenotype in LOUCY_MEF2C-BFP cells when cultured on DLL4-coated plates in the absence of dox (except when indicated). (C) Western blot of MEF2C, P-MEF2C (Ser222), and BCL2 in noninduced (no dox) or MEF2C-induced (+dox) LOUCY_MEF2C-BFP cells that were incubated in the presence of increasing concentrations of inhibitors HG-9-91-01 for 4 days. Band intensity ratios for various proteins relatively to β-actin control levels is indicated, with the –dox condition set at the value = 1. (D) Cell viability of noninduced (no dox) or MEF2C-induced (+dox) LOUCY_MEF2C-BFP after a 4-day exposure to a serial dilution of prednisolone combined with a serial dilution of HG-9-91-01 at the concentrations indicated. ZIP synergy scores are calculated from an n = 3 per condition. ZIP scores < –10 are indicated with a dash-dot line and a blue color. ZIP scores > 10 are indicated by a dashed line.