PI3K/mTOR is a therapeutically targetable genetic dependency in diffuse intrinsic pontine glioma
Ryan J. Duchatel, … , Jason E. Cain, Matthew D. Dun
Ryan J. Duchatel, … , Jason E. Cain, Matthew D. Dun
Published February 6, 2024
Citation Information: J Clin Invest. 2024;134(6):e170329. https://doi.org/10.1172/JCI170329.
View: Text | PDF
Research Article Oncology

PI3K/mTOR is a therapeutically targetable genetic dependency in diffuse intrinsic pontine glioma

Abstract

Diffuse midline glioma (DMG), including tumors diagnosed in the brainstem (diffuse intrinsic pontine glioma; DIPG), are uniformly fatal brain tumors that lack effective treatment. Analysis of CRISPR/Cas9 loss-of-function gene deletion screens identified PIK3CA and MTOR as targetable molecular dependencies across patient derived models of DIPG, highlighting the therapeutic potential of the blood-brain barrier–penetrant PI3K/Akt/mTOR inhibitor, paxalisib. At the human-equivalent maximum tolerated dose, mice treated with paxalisib experienced systemic glucose feedback and increased insulin levels commensurate with patients using PI3K inhibitors. To exploit genetic dependence and overcome resistance while maintaining compliance and therapeutic benefit, we combined paxalisib with the antihyperglycemic drug metformin. Metformin restored glucose homeostasis and decreased phosphorylation of the insulin receptor in vivo, a common mechanism of PI3K-inhibitor resistance, extending survival of orthotopic models. DIPG models treated with paxalisib increased calcium-activated PKC signaling. The brain penetrant PKC inhibitor enzastaurin, in combination with paxalisib, synergistically extended the survival of multiple orthotopic patient-derived and immunocompetent syngeneic allograft models; benefits potentiated in combination with metformin and standard-of-care radiotherapy. Therapeutic adaptation was assessed using spatial transcriptomics and ATAC-Seq, identifying changes in myelination and tumor immune microenvironment crosstalk. Collectively, this study has identified what we believe to be a clinically relevant DIPG therapeutic combinational strategy.

Authors

Ryan J. Duchatel, Evangeline R. Jackson, Sarah G. Parackal, Dylan Kiltschewskij, Izac J. Findlay, Abdul Mannan, Dilana E. Staudt, Bryce C. Thomas, Zacary P. Germon, Sandra Laternser, Padraic S. Kearney, M. Fairuz B. Jamaluddin, Alicia M. Douglas, Tyrone Beitaki, Holly P. McEwen, Mika L. Persson, Emily A. Hocke, Vaibhav Jain, Michael Aksu, Elizabeth E. Manning, Heather C. Murray, Nicole M. Verrills, Claire Xin Sun, Paul Daniel, Ricardo E. Vilain, David A. Skerrett-Byrne, Brett Nixon, Susan Hua, Charles E. de Bock, Yolanda Colino-Sanguino, Fatima Valdes-Mora, Maria Tsoli, David S. Ziegler, Murray J. Cairns, Eric H. Raabe, Nicholas A. Vitanza, Esther Hulleman, Timothy N. Phoenix, Carl Koschmann, Frank Alvaro, Christopher V. Dayas, Christopher L. Tinkle, Helen Wheeler, James R. Whittle, David D. Eisenstat, Ron Firestein, Sabine Mueller, Santosh Valvi, Jordan R. Hansford, David M. Ashley, Simon G. Gregory, Lindsay B. Kilburn, Javad Nazarian, Jason E. Cain, Matthew D. Dun

×

Figure 8

Combining paxalisib and enzastaurin with RT using an immunocompetent syngeneic DIPG mouse model.

Options: View larger image (or click on image) Download as PowerPoint
Combining paxalisib and enzastaurin with RT using an immunocompetent syn...
(A) In utero electroporation syngeneic allograft model of DIPG serially transplanted into C57BL/6J mice, (B) treated with optimized paxalisib (5 mg/kg/b.i.d. paxalisib + 175 mg/kg/day metformin) and enzastaurin (100mg/kg/day), alone and in combination with RT (1.8 Gy/day), for 4 weeks. (C) Monitoring of tumor burden using BLI over time (representative BLI images presented, shaded area indicates treatment time), (D) of mice treated with optimized paxalisib, enzastaurin, or the combination without RT. (E) Kaplan Meier survival analysis of mice treated with optimized paxalisib, enzastaurin, or the combination (shaded area indicates treatment time, log-rank test, treated versus untreated; *P < 0.05, ***P < 0.001, ****P < 0.0001, synergistic comparisons; $P < 0.01, $$P < 0.01). (F) Monitoring of tumor burden using BLI over time (representative images presented) (G) of mice treated with optimized paxalisib, enzastaurin ± RT. (H) Kaplan Meier survival analysis of mice treated with optimized paxalisib, enzastaurin, or the combination, with upfront RT (shaded area indicates treatment time, log-rank test, *P < 0.05, ***P < 0.001, ****P < 0.0001, synergistic comparisons; $P < 0.01, $$P < 0.01). Vehicle Kaplan-Meier curve is duplicated from (E) for visual reference. (I) IHC analysis of tumors resected 2 weeks after treatment and (J) quantified using ImageJ (measured in technical triplicate, across biological replicates, n = 3, 1-way ANOVA, *P < 0.05, **P < 0.01, ***P < 0.001, treated versus untreated; #P < 0.05, ##P < 0.01, ###P < 0.001, ####P < 0.0001).