P11.09 Radiation DNA damage repair inhibition by GSK-J4 induced chromatin compaction in DIPG
Year: 2017
Type: conference-abstract
Abstract: Introduction: Diffuse intrinsic pontine glioma (DIPG) is among the most devastating childhood cancers, and virtually all patients die within two years after diagnosis. Since these tumors occur in the brainstem, there are no surgical options for providing relief to patients. The only therapeutic modality routinely used in the treatment of DIPG is radiation. Radiation often provides transient relief from DIPG symptoms, as cancer recurrence and patient demise are inevitable. Therefore, identifying efficacious therapeutics to enhance radiation effect is desperately needed. We have recently shown that inhibition of the histone H3K27 demethylase JMJD3 acts to restore H3K27 methylation in DIPG harboring H3K27M mutation, while demonstrating potent anti-tumor activity, both in vitro and in vivo. Our gene expression profiling of K27M DIPG treated with GSK-J4, a JMJD3 demethylase inhibitor, revealed several decreases in the genes encoding proteins involved in DNA double-strand break (DSB) repair. Our aim is to investigate the hypothesis that GSK-J4 may inhibit radiation-induced DNA repair by chromatin modification, in association with analysis of therapeutic combination of GSK-J4 and radiation. METHODS: We evaluated DNA damage repair via quantitative-PCR, immunocytochemistry of DSB markers γH2AX and 53BP1, western blotting and DNA repair assay. MNase digestion and FAIRE-seq was used to analyze nucleosome assembly and transcriptional activity in cellular chromatin. Assessment of DIPG response to radiation therapy (RT) in combination with GSK-J4 was performed using clonogenic survival assays. In vivo response to radiation monotherapy and combination of RT + GSK-J4 were measured by bioluminescence imaging and animal survival studies. RESULTS: qPCR results showed that GSK-J4 significantly reduces DNA DSB repair genes such as PARP1, PARP2, SMARCB1 and BRCA1, in irradiated DIPG cells. Immunocytochemistry results support that GSK-J4 sustains high levels of γH2AX and 53BP1 in irradiated DIPG cells, thereby inhibiting DNA DSB repair. Mnase assay indicated that GSK-J4 causes chromatin compaction which prevents DNA DSB repair. We are currently conducting clonogenic assays to assess long term effect of GSK-J4 on radiated cells as well as western blotting, FAIRE-seq and in vivo studies, the results of which will be reported at the meeting. GRANTS AND FELLOWSHIPS: This work was supported by the US National Institutes of Health RO1NS093079, the Bear Necessities Pediatric Cancer Foundation and Rally Foundation.
Source: Neuro-Oncology
Institutions: Northwestern University, Lurie Children's Hospital
Language: English
Subfield: Genetics
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2607764267