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Targeted inhibition of Bcl-xL following radiation reduces tumourigenesis in preclinical models of H3K27M-altered diffuse midline glioma

ABSTRACT: Abstract Background: Diffuse midline gliomas (DMGs) with histone H3K27M mutations represent a devastating paediatric brain cancer characterized by abysmal prognosis and limited treatment options. The only approved treatment is radiotherapy (RT), but most of the tumours relapse with fatal consequences. In this study, we sought to investigate whether irradiation leads to senescence induction and explore the efficacy of senolytics against DMG. Methods: We have characterised the senescent phenotype of five genetically heterogeneous H3K27M-altered human DMG cell lines, combining cellular and/or molecular approaches. The sensitivity of senescent cells to Bcl-xL inhibition has been demonstrated in dose/response curves in vitro and in a PDX model of DMG. Results: Here, we show that ionizing radiation induces senescence and SASP responses in both TP53 mutant and wild-type H3K27M-altered human DMG cell lines. We identify Navitoclax as a potent senolytic agent that selectively targets senescent DMG cells into apoptosis by inhibiting Bcl-xL. Related compounds, such as a proteolysis-targeting chimera (PROTAC)-mediated Bcl-xL degradation and a galacto-conjugated form of Navitoclax also show an effective senolytic activity in senescent cancer cells. Finally, we show that a combination therapy of irradiation and Navitoclax results in reduced tumor burden and increased mouse survival in an orthotopic xenograft DMG model. Conclusion: These results offer a rationale for further clinical development of senolytic therapies as part of multimodal treatment approaches for DMG patients/

ORGANISM(S): Homo sapiens

PROVIDER: GSE291046 | GEO | 2025/07/03

REPOSITORIES: GEO

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Project description:Cellular senescence contributes to a variety of pathologies associated with aging and is implicated as a cellular state in which cancer cells can survive treatment. Reported senolytic drug treatments act through varying molecular mechanisms, but heterogeneous efficacy across the diverse contexts of cellular senescence indicates a need for predictive biomarkers of senolytic activity. Using multi-parametric analyses of commonly reported molecular features of the senescent phenotype, we assayed a variety of models, including malignant and nonmalignant cells, using several triggers of senescence induction and found no predictive power of these traditional senescence markers to identify senolytic drug sensitivity. We sought to identify novel drug targets in senescent cells that were insensitive to frequently implemented senolytic therapies, such as Navitoclax (ABT263), using quantitative mass spectrometry to measure changes in the senescent proteome, compared to cells which acquire an acute sensitivity to ABT263 with senescence induction. Inhibition of the antioxidant GPX4 or the Bcl-2 family member MCL-1 using small molecule compounds in combination with ABT263 significantly increased the induction of apoptosis in some, but not all, previously insensitive senescent cells. We then asked if we could use BH3 profiling to measure differences in mitochondrial apoptotic priming in these models of cellular senescence and predict sensitivity to the ABT263 or the combination of dasatinib and quercetin (D+Q). We found, despite being significantly less primed for apoptosis overall, the dependence of senescent mitochondria on BCL-xL was significantly correlated to senescent cell killing by both ABT263 and D+Q, despite no significant changes in the gene or protein expression of BCL-xL. However, our data caution against broad classification of drugs as globally senolytic and instead provide impetus for context-specific senolytic targets and propose BH3 profiling as an effective predictive biomarker.

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Targeted inhibition of Bcl-xL following radiation reduces tumourigenesis in preclinical models of H3K27M-altered diffuse midline glioma

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