Dataset Information

HDAC inhibition induces expression of scaffolding proteins critical for tumor progression in pediatric glioma: focus on EBP50 and IRSp53.

ABSTRACT:

Background

Diffuse midline glioma (DMG) is a pediatric malignancy with poor prognosis. Most children die less than one year after diagnosis. Recently, mutations in histone H3 have been identified and are believed to be oncogenic drivers. Targeting this epigenetic abnormality using histone deacetylase (HDAC) inhibitors such as panobinostat (PS) is therefore a novel therapeutic option currently evaluated in clinical trials.

Methods

BH3 profiling revealed engagement in an irreversible apoptotic process of glioma cells exposed to PS confirmed by annexin-V/propidium iodide staining. Using proteomic analysis of 3 DMG cell lines, we identified 2 proteins deregulated after PS treatment. We investigated biological effects of their downregulation by silencing RNA but also combinatory effects with PS treatment in vitro and in vivo using a chick embryo DMG model. Electron microscopy was used to validate protein localization.

Results

Scaffolding proteins EBP50 and IRSp53 were upregulated by PS treatment. Reduction of these proteins in DMG cell lines leads to blockade of proliferation and migration, invasion, and an increase of apoptosis. EBP50 was found to be expressed in cytoplasm and nucleus in DMG cells, confirming known oncogenic locations of the protein. Treatment of glioma cells with PS together with genetic or chemical inhibition of EBP50 leads to more effective reduction of cell growth in vitro and in vivo.

Conclusion

Our data reveal a specific relation between HDAC inhibitors and scaffolding protein deregulation which might have a potential for therapeutic intervention for cancer treatment.

SUBMITTER: Capdevielle C

PROVIDER: S-EPMC7158654 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Diffuse midline glioma (DMG) is an aggressive pediatric tumor localized in the brainstem. The median survival after diagnosis is less than one year. Surgical resection is not possible due to the critical localization of the tumor and radiation therapy alone or in combination with chemotherapy show only minimal benefit. In 80% of cases, DIPGs are harbor genetic abnormalities such as a K27M mutation in histone H3, suggesting drugs targeting epigenetic anomalies might be efficient. Indeed, Grasso et al. (Nature Medicine, 2015) have shown that the histone deacetylase inhibitor panobinostat (PS) affects glioma cell growth in vitro and in vivo. PS is currently undergoing phase 1 clinical trials. To better understand the mechanism of action of PS on tumor cells, we performed a proteomic analysis by comparing DMG cells treated with panobinostat to control cells. We identified 2 proteins in PS-treated cells: EBP50 (or NHERF-1) and IRSp53 (or BAIAP2). EBP50 protein is implicated in invasion (Kislin et al. Neoplasia, 2009) but it can also act like a tumor suppressor on glioblastoma (Molina et al. Cancer Research, 2010). There is a dual role of the protein which depends on its localization in the cell: when localized at the cell membrane, EBP50 acts as a tumor suppressor, but has oncogenic properties when present in the cytoplasm or nucleus. Using electron microscopy combined with immunofluorescence, we could validate expression of EBP50 in all cellular compartments. IRSp53 is implicated in proliferation of tumor cells (Liu P.S. Oncogene, 2010) and may have an important role during migration and invasion (Funato et al., Cancer Research 2004). To elucidate the role of the two proteins in DIPG, we investigated effects of gene knockdown by siRNA and stable overexpression using lentiviruses. For each protein, we found a significant diminution of proliferation, migration and invasion and an increase in apoptosis cells were transfected with siRNAs. In contrast, overexpression of EBP50 did not have any effect on cells. Our results suggest that the two proteins induced by PS treatment are implicated in tumor progression and might constitute novel additional therapeutic targets, especially as adjuvant treatment together with PS.