Boult, J. | bioRxiv Science

bioRxiv2024

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

BackgroundDiffuse 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. MethodsWe 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. ResultsHere, 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. ConclusionThese results offer a rationale for further clinical development of senolytic therapies as part of multimodal treatment approaches for DMG patients/ Key PointsO_LIIonising irradiation induces senescence in human DMG cells independently of the p53 status. C_LIO_LIBcl-xL inhibition results in apoptosis of human DMG senescent cells in synergy with irradiation. C_LIO_LICombination of irradiation and BcL-xL inhibition reduces tumourigenesis in a PDX model of DMG. C_LI Importance of the StudyH3K27M-altered DMG are devastating paediatric tumours with an abysmal prognosis. The only approved treatment is radiotherapy but this is palliative and tumours almost always relapse with fatal consequences for the patients. In this study, we show that radiotherapy results in senescence induction in five genomically heterogeneous human DMG cell lines. We identify that drugs targeting the anti-apoptotic protein Bcl-xL show a strong senolytic activity in conjunction with radiotherapy both in vitro in DMG cells and in vivo in a PDX model of H3K27M-altered DMG. Treatment with Bcl-xL inhibitor Navitoclax, or related compounds targeting Bcl-xL protein degradation or containing a galactose conjugated form of Navitoclax results in DMG cancer cell apoptosis. As several of these inhibitors are currently being tested in ongoing clinical trials against other diseases, our data support the use of Bcl-xL inhibition mediated senolytics as an adjuvant therapy to radiotherapy to potentially improve outcomes in this challenging disease setting.

cancer biology↗

bioRxiv2020

Drug screening linked to molecular profiling identifies novel dependencies in patient-derived primary cultures of paediatric high grade glioma and DIPG

Paediatric high grade glioma and diffuse midline glioma (including DIPG) are comprised of multiple biological and clinical subgroups, the majority of which urgently require novel therapies. Patient-derived in vitro primary cell cultures represent potentially useful tools for mechanistic and preclinical investigation based upon their retention of key features of tumour subgroups under experimental conditions amenable to high-throughput approaches. We present 17 novel primary cultures derived from patients in London, Dublin and Belfast, and together with cultures established or shared from Barcelona, Brisbane, Rome and Stanford, assembled a panel of 52 models under 2D (laminin matrix) and/or 3D (neurospheres) conditions, fully credentialed by phenotypic and molecular comparison to the original tumour sample (methylation BeadArray, panel/exome sequencing, RNAseq). In screening a subset of these against a panel of ~400 approved chemotherapeutics and small molecules, we identified specific dependencies associated with tumour subgroups and/or specific molecular markers. These included MYCN-amplified cells and ATM/DNA-PK inhibitors, and DIPGs with PPM1D activating truncating mutations and inhibitors of MDM2 or PARP1. Specific mutations in PDGFRA were found to confer sensitivity to a range of RTK inhibitors, though not all such mutations conferred sensitivity to targeted agents. Notably, dual PDGFRA/FGFR and downstream pathway MEK inhibitors showed profound effects against both PDGFRA-sensitising mutant and FGFR1-dependent non-brainstem pHGG and DIPG. In total, 85% cells were found to have at least one drug screening hit in short term assays linked to the underlying biology of the patients tumour, providing a rational approach for individualised clinical translation.

cancer biology↗