Original Article

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PHF20 collaborates with PARP1 to promote stemness and aggressiveness of neuroblastoma cells through activation of SOX2 and OCT4 Free
Wenyong Long 1,2,† , Wei Zhao 2,3,† , Bo Ning 2,4 , Jing Huang 2 , Junjun Chu 3 , Linfeng Li 2 ,Qianquan Ma 1,2 , Changsheng Xing 2 , Helen Y. Wang 2 , Qing Liu 1 , and Rong-Fu Wang 2,5,6, *
1Department of Neurosurgery in Xiangya Hospital, Central South University, Changsha 410008, China
2Center for Inflammation and Epigenetics, Houston Methodist Research Institute, Houston, TX 77030, USA
3Key Laboratory of Stem Cells and Tissue Engineering, Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080,China
4Institute Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
5Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, New York, NY 10065, USA
6Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, TX 77030, USA
These authors contributed equally to this work.
*Correspondence to:Rong-Fu Wang, E-mail: rwang3@houstonmethodist.org
J Mol Cell Biol, Volume 10, Issue 2, April 2018, 147-160,  https://doi.org/10.1093/jmcb/mjy007
Keyword: PHF20, neuroblastoma, PARP1, cancer stem cell-like traits, epigenetic regulation

The differentiation status of neuroblastoma (NB) strongly correlates with its clinical outcomes; however, the molecular mechanisms driving maintenance of stemness and differentiation remain poorly understood. Here, we show that plant homeodomain finger-containing protein 20 (PHF20) functions as a critical epigenetic regulator in sustaining stem cell-like phenotype of NB by using CRISPR/Cas9-based targeted knockout (KO) for high-throughput screening of gene function in NB cell differentiation. The expression of PHF20 in NB was significantly associated with high aggressiveness of the tumor and poor outcomes for NB patients. Deletion of PHF20 inhibited NB cell proliferation, invasive migration, and stem cell-like traits. Mechanistically, PHF20 interacts with poly(ADP-ribose) polymerase 1 (PARP1) and directly binds to promoter regions of octamer-binding transcription factor 4 (OCT4) and sex determining region Y-box 2 (SOX2) to modulate a histone mark associated with active transcription, trimethylation of lysine 4 on histone H3 protein subunit (H3K4me3). Overexpression of OCT4 and SOX2 restored growth and progression of PHF20 KO tumor cells. Consistently, OCT4 and SOX2 protein levels in clinical NB specimens were positively correlated with PHF20 expression. Our results establish PHF20 as a key driver of NB stem cell-like properties and aggressive behaviors, with implications for prognosis and therapy.