Chromatin remodeler HELLS maintains glioma stem cells through E2F3 and MYC
Guoxin Zhang, Zhen Dong, Briana C. Prager, Leo J.K. Kim, Qiulian Wu, Ryan C. Gimple, Xiuxing Wang, Shideng Bao, Petra Hamerlik, Jeremy N. Rich
Guoxin Zhang, Zhen Dong, Briana C. Prager, Leo J.K. Kim, Qiulian Wu, Ryan C. Gimple, Xiuxing Wang, Shideng Bao, Petra Hamerlik, Jeremy N. Rich
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Research Article Oncology Stem cells

Chromatin remodeler HELLS maintains glioma stem cells through E2F3 and MYC

Abstract

Glioblastomas, which contain stem cell–like glioblastoma stem cells (GSCs), are universally lethal cancers. While neural stem cells (NSCs) are usually quiescent, single-cell studies suggest that proliferating glioblastoma cells reside in the GSC population. Interrogating in silico glioma databases for epigenetic regulators that correlate with cell cycle regulation, we identified the chromatin remodeler HELLS as a potential target in glioblastoma. GSCs preferentially expressed HELLS compared with their differentiated tumor progeny and nonmalignant brain cells. Targeting HELLS disrupted GSC proliferation, survival, and self-renewal with induction of replication stress and DNA damage. Investigating potential molecular mechanisms downstream of HELLS revealed that HELLS interacted with the core oncogenic transcription factors, E2F3 and MYC, to regulate gene expression critical to GSC proliferation and maintenance. Supporting the interaction, HELLS expression strongly correlated with targets of E2F3 and MYC transcriptional activity in glioblastoma patients. The potential clinical significance of HELLS was reinforced by improved survival of tumor-bearing mice upon targeting HELLS and poor prognosis of glioma patients with elevated HELLS expression. Collectively, targeting HELLS may permit the functional disruption of the relatively undruggable MYC and E2F3 transcription factors and serve as a novel therapeutic paradigm for glioblastoma.

Authors

Guoxin Zhang, Zhen Dong, Briana C. Prager, Leo J.K. Kim, Qiulian Wu, Ryan C. Gimple, Xiuxing Wang, Shideng Bao, Petra Hamerlik, Jeremy N. Rich

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Figure 8

HELLS interacts with E2F3 and MYC to regulate gene expression.

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HELLS interacts with E2F3 and MYC to regulate gene expression. (A) GSC 3...
(A) GSC 3565 cells were transduced with FLAG-HELLS and either HA-E2F3a or HA-E2F3b and then underwent whole cell lysis. Immunoprecipitation for HELLS was performed on the lysates with an anti-FLAG antibody, which were then resolved by SDS-PAGE, and immunoblotting was performed with an anti-HA antibody. Inputs are indicated. Results are typical of 3 independent experiments. (B) GSC 387 and 3565 underwent ChIP followed by PCR (ChIP-qPCR) using antibodies for IgG control, HELLS, or E2F3. Primers specific for previously described E2F3 targets were used (ref. 32). Data are presented as mean ± SD. Three independent experiments were performed. (C) ChIP-qPCR analysis for binding of E2F3 to its targets gene in GSC 387 and 3565 after HELLS knockdown. Data are presented as mean ± SD. **P < 0.01, ***P < 0.001, by t test. Three independent experiments were performed. (D) GSC 387 and 3565 were transduced with either FLAG-HELLS or FLAG-GFP and then lysed. An anti-FLAG antibody was used for immunoprecipitation, and immunoblotting was performed with an anti-MYC antibody. Inputs are indicated. Three independent experiments were performed. (E) Endogenous coimmunoprecipitation experiments to consider HELLS and MYC binding were performed in GSC 387 and 3565. Whole cell lysates were collected and subjected to immunoprecipitation with an anti-HELLS or IgG control antibody and then immunoblotting was performed with an anti-MYC antibody. Inputs are indicated. Three independent experiments were performed. (F) ChIP-qPCR analysis for binding of HELLS and MYC in GSC 387 and 3565. Primers specific for MYC targets were used (ref. 32). IgG was used as control. Data are presented as mean ± SD. Three independent experiments were performed. (G) ChIP-qPCR analysis for binding of MYC to its targets gene in GSC 387 and 3565 after HELLS knockdown. Data are presented as mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001, by t test. Three independent experiments were performed.