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Figure 2 from Coordinated Targeting of S6K1/2 and AXL Disrupts Pyrimidine Biosynthesis in PTEN-Deficient Glioblastoma

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posted on 2024-08-23, 10:20 authored by Catherine A. Behrmann, Kelli N. Ennis, Pranjal Sarma, Collin Wetzel, Nicholas A. Clark, Kate M. Von Handorf, Subrahmanya Vallabhapurapu, Cristina Andreani, James Reigle, Pier Paolo Scaglioni, Jarek Meller, Maria F. Czyzyk-Krzeska, Ady Kendler, Xiaoyang Qi, Jann N. Sarkaria, Mario Medvedovic, Soma Sengupta, Biplab Dasgupta, David R. Plas

PTEN-deficient patient-derived sphere growth is inhibited by combination S6K1 and AXL inhibition. A, JHH136 patient-derived GBM were treated for 72 hours with 10 μmol/L LY-2584702 and/ or 10 μmol/L BMS-777607. Phase contrast images show reduced sphere size with inhibitor combination compared with single inhibitor treatment and vehicle control (n = 3). Scale bar, 100 μm. B, Quantification of spheres in three independent cultures as in A are shown. P values from t tests indicate combination efficacy compared with single agent controls. C, Mayo59 treated with 10 μmol/L LY-2584702 and/or 10 μmol/L BMS-777607 for 7 days. Combination treatment reduced sphere size and induced an altered morphology (n = 3). Scale bar, 200 μm. D, Quantification of images in C shows significant reduction in sphere size in combination-treated spheres. E, Symptom-free survival of mice bearing intracranial tumors of Mayo59 PDX treated with vehicle or a combination of LY-2584702 and BMS-777607 together. Survival curve shows that animals gained a sustained delay in disease from combination treatment (n = 10 per group). F, Cox proportional hazard ratio analysis for mice in E. Log-rank score for combination treatment is below 0.002.

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ARTICLE ABSTRACT

Intrinsic resistance to targeted therapeutics in PTEN-deficient glioblastoma (GBM) is mediated by redundant signaling networks that sustain critical metabolic functions. Here, we demonstrate that coordinated inhibition of the ribosomal protein S6 kinase 1 (S6K1) and the receptor tyrosine kinase AXL using LY-2584702 and BMS-777607 can overcome network redundancy to reduce GBM tumor growth. This combination of S6K1 and AXL inhibition suppressed glucose flux to pyrimidine biosynthesis. Genetic inactivation studies to map the signaling network indicated that both S6K1 and S6K2 transmit growth signals in PTEN-deficient GBM. Kinome-wide ATP binding analysis in inhibitor-treated cells revealed that LY-2584702 directly inhibited S6K1, and substrate phosphorylation studies showed that BMS-777607 inactivation of upstream AXL collaborated to reduce S6K2-mediated signal transduction. Thus, combination targeting of S6K1 and AXL provides a kinase-directed therapeutic approach that circumvents signal transduction redundancy to interrupt metabolic function and reduce growth of PTEN-deficient GBM. Therapy for glioblastoma would be advanced by incorporating molecularly targeted kinase-directed agents, similar to standard of care strategies in other tumor types. Here, we identify a kinase targeting approach to inhibit the metabolism and growth of glioblastoma.