Glioblastoma cancer-stem like cells (GSCs) display marked resistance to ionizing radiation (IR), a standard of care for glioblastoma patients. Mechanisms underpinning radio-resistance of GSCs remain largely unknown. Chromatin state and the accessibility of DNA lesions to DNA repair machineries are crucial for the maintenance of genomic stability. Understanding the functional impact of chromatin remodeling on DNA repair in GSCs may lay the foundation for advancing the efficacy of radio-sensitizing therapies. Here, we present the results of a high-content siRNA microscopy screen, revealing the transcriptional elongation factor SPT6 to be critical for the genomic stability and self-renewal of GSCs. Mechanistically, SPT6 transcriptionally up-regulates BRCA1 and thereby drives an error-free DNA repair in GSCs. SPT6 loss impairs the self-renewal, genomic stability and tumor initiating capacity of GSCs. Collectively, our results provide mechanistic insights into how SPT6 regulates DNA repair and identify SPT6 as a putative therapeutic target in glioblastoma.

• MeSH
• Apoptosis MeSH
• Gene Knockdown Techniques MeSH
• Glioblastoma genetics   pathology   MeSH
• HEK293 Cells MeSH
• Heterografts MeSH
• Radiation, Ionizing MeSH
• Cell Cycle Checkpoints MeSH
• Humans MeSH
• RNA, Small Interfering genetics   MeSH
• Mice, Inbred BALB C MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Neoplastic Stem Cells * pathology   MeSH
• Brain Neoplasms genetics   MeSH
• Genomic Instability * MeSH
• DNA Repair * MeSH
• BRCA1 Protein MeSH
• Gene Expression Regulation, Neoplastic MeSH
• Radiation Tolerance MeSH
• Transcription Factors genetics   metabolism   MeSH
• Transcriptome MeSH
• Gene Silencing MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• BRCA1 protein, human MeSH Browser
• RNA, Small Interfering MeSH
• BRCA1 Protein MeSH
• SUPT6H protein, human MeSH Browser
• Transcription Factors MeSH

Inflammatory and oncogenic signaling converge in disease evolution of BCR-ABL-negative myeloproliferative neoplasms, clonal hematopoietic stem cell disorders characterized by gain-of-function mutation in JAK2 kinase (JAK2V617F), with highest prevalence in patients with polycythemia vera (PV). Despite the high risk, DNA-damaging inflammatory microenvironment, PV progenitors tend to preserve their genomic stability over decades until their progression to post-PV myelofibrosis/acute myeloid leukemia. Using induced pluripotent stem cells-derived CD34+ progenitor-enriched cultures from JAK2V617F+ PV patient and from JAK2 wild-type healthy control, CRISPR-modified HEL cells and patients' bone marrow sections from different disease stages, we demonstrate that JAK2V617F induces an intrinsic IFNγ- and NF-κB-associated inflammatory program, while suppressing inflammation-evoked DNA damage both in vitro and in vivo. We show that cells with JAK2V617F tightly regulate levels of inflammatory cytokines-induced reactive oxygen species, do not fully activate the ATM/p53/p21waf1 checkpoint and p38/JNK MAPK stress pathway signaling when exposed to inflammatory cytokines, suppress DNA single-strand break repair genes' expression yet overexpress the dual-specificity phosphatase (DUSP) 1. RNAi-mediated knock-down and pharmacological inhibition of DUSP1, involved in p38/JNK deactivation, in HEL cells reveals growth addiction to DUSP1, consistent with enhanced DNA damage response and apoptosis in DUSP1-inhibited parental JAK2V617F+ cells, but not in CRISPR-modified JAK2 wild-type cells. Our results indicate that the JAK2V617F+ PV progenitors utilize DUSP1 activity as a protection mechanism against DNA damage accumulation, promoting their proliferation and survival in the inflammatory microenvironment, identifying DUSP1 as a potential therapeutic target in PV.

• MeSH
• Cytokines genetics   metabolism   MeSH
• Dual Specificity Phosphatase 1 genetics   MeSH
• Hematopoietic Stem Cells pathology   MeSH
• Induced Pluripotent Stem Cells pathology   MeSH
• Janus Kinase 2 genetics   MeSH
• Humans MeSH
• Mutation MeSH
• Cell Line, Tumor MeSH
• Tumor Microenvironment MeSH
• Oxidative Stress * MeSH
• Polycythemia Vera genetics   MeSH
• DNA Damage * MeSH
• Cell Proliferation * MeSH
• Reproducibility of Results MeSH
• STAT1 Transcription Factor metabolism   MeSH
• Inflammation metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cytokines MeSH
• DUSP1 protein, human MeSH Browser
• Dual Specificity Phosphatase 1 MeSH
• JAK2 protein, human MeSH Browser
• Janus Kinase 2 MeSH
• STAT1 protein, human MeSH Browser
• STAT1 Transcription Factor MeSH