Ezh2 loss propagates hypermethylation at T cell differentiation–regulating genes to promote leukemic transformation
Changshan Wang, … , Atsushi Iwama, Goro Sashida
Changshan Wang, … , Atsushi Iwama, Goro Sashida
Published August 6, 2018
Citation Information: J Clin Invest. 2018;128(9):3872-3886. https://doi.org/10.1172/JCI94645.
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Research Article Hematology Oncology

Ezh2 loss propagates hypermethylation at T cell differentiation–regulating genes to promote leukemic transformation

Abstract

Early T cell precursor acute lymphoblastic leukemia (ETP-ALL) is a new pathological entity with poor outcomes in T cell ALL (T-ALL) that is characterized by a high incidence of loss-of-function mutations in polycomb repressive complex 2 (PRC2) genes. We generated a mouse model of ETP-ALL by deleting Ezh2, one of the PRC2 genes, in p53-null hematopoietic cells. The loss of Ezh2 in p53-null hematopoietic cells impeded the differentiation of ETPs and eventually induced ETP-ALL–like disease in mice, indicating that PRC2 functions as a bona fide tumor suppressor in ETPs. A large portion of PRC2 target genes acquired DNA hypermethylation of their promoters following reductions in H3K27me3 levels upon the loss of Ezh2, which included pivotal T cell differentiation–regulating genes. The reactivation of a set of regulators by a DNA-demethylating agent, but not the transduction of single regulator genes, effectively induced the differentiation of ETP-ALL cells. Thus, PRC2 protects key T cell developmental regulators from DNA hypermethylation in order to keep them primed for activation upon subsequent differentiation phases, while its insufficiency predisposes ETPs to leukemic transformation. These results revealed a previously unrecognized epigenetic switch in response to PRC2 dysfunction and provide the basis for specific rational epigenetic therapy for ETP-ALL with PRC2 insufficiency.

Authors

Changshan Wang, Motohiko Oshima, Daisuke Sato, Hirotaka Matsui, Sho Kubota, Kazumasa Aoyama, Yaeko Nakajima-Takagi, Shuhei Koide, Jun Matsubayashi, Makiko Mochizuki-Kashio, Takako Nakano-Yokomizo, Jie Bai, Toshitaka Nagao, Akinori Kanai, Atsushi Iwama, Goro Sashida

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Figure 7

Aberrant DNA hypermethylation sensitized ETP-ALL cells to a DNA hypomethylating agent.

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Aberrant DNA hypermethylation sensitized ETP-ALL cells to a DNA hypometh...
(A) Total cell counts of control (black line) and DAC-treated (25 nM, blue broken line; 50 nM, blue line) Ezh2Δ/Δp53Δ/Δ ETP-ALL cells monitored for 6 days in the culture (n = 3). Data are representative of 3 independent experiments. (B) Representative flow cytometric profiles of CD4 and CD8 expression (top) and CD44 and CD25 expression in CD4–CD8– DN cells (bottom) on day 6 of the culture in A. (C) Proportions of CD4+CD8+ DP cells, CD4 SP cells, CD8 SP cells, and CD4–CD8– DN cells in control and DAC-treated (50 nM) cultures on day 6 (n = 4–5). (D) Quantitative RT-PCR analysis of the expression of Runx1, Bcl11b, and Nr4a3 in purified DN2 cells harvested from control and ETP-ALL cells treated with 50 nM DAC on day 3 of the culture (n = 6–9). (E) Numbers of hypo- and hyper-DMRs at CGIs and promoters in DAC-induced Ezh2Δ/Δp53Δ/Δ leukemic DN4 cells relative to DMSO-induced Ezh2Δ/Δp53Δ/Δ leukemic DN2 cells. (F) ChIP-seq view of H3K27me3 levels at the Nr4a3 locus in WT and Ezh2Δ/Δp53Δ/Δ leukemic DN1 cells and RRBS data of DNA methylation at the Nr4a3 locus in Ezh2Δ/Δp53Δ/Δ leukemic DN2 cells and DAC-induced Ezh2Δ/Δp53Δ/Δ leukemic DN4 cells. ***P < 0.001, Student’s t test. (G) GO biological process gene sets enriched in hyper-DMRs (red bars) and hypo-DMRs (blue bars). (H) Chimerism of CD45.2+ cells in the PB cells of DMSO-treated and DAC-treated (0.2 mg/kg, 3 times a week) Ezh2Δ/Δp53Δ/Δ leukemic mice 3 weeks after the completion of the treatment (n = 4–5). (I) Longer median survival of DAC-treated Ezh2Δ/Δp53Δ/Δ leukemic mice compared with DMSO-treated mice (n = 6). Representative data of the 2 independent experiments are shown. P value is by log-rank test.