RESUMO
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. SIGNIFICANCE: 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.
Assuntos
Receptor Tirosina Quinase Axl , Glioblastoma , PTEN Fosfo-Hidrolase , Proteínas Proto-Oncogênicas , Pirimidinas , Receptores Proteína Tirosina Quinases , Glioblastoma/tratamento farmacológico , Glioblastoma/metabolismo , Glioblastoma/patologia , Glioblastoma/genética , Humanos , Receptores Proteína Tirosina Quinases/metabolismo , Receptores Proteína Tirosina Quinases/genética , Receptores Proteína Tirosina Quinases/antagonistas & inibidores , PTEN Fosfo-Hidrolase/metabolismo , PTEN Fosfo-Hidrolase/deficiência , PTEN Fosfo-Hidrolase/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas/antagonistas & inibidores , Proteínas Proto-Oncogênicas/genética , Pirimidinas/farmacologia , Linhagem Celular Tumoral , Animais , Transdução de Sinais/efeitos dos fármacos , Camundongos , Proteínas Quinases S6 Ribossômicas 70-kDa/metabolismo , Proteínas Quinases S6 Ribossômicas 70-kDa/genética , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/genética , Ensaios Antitumorais Modelo de Xenoenxerto , Inibidores de Proteínas Quinases/farmacologia , Proliferação de Células/efeitos dos fármacos , Aminopiridinas , PiridonasRESUMO
Genetic S6K1 inactivation can induce apoptosis in PTEN-deficient cells. We analyzed the therapeutic potential of S6K1 inhibitors in PTEN-deficient T cell leukemia and glioblastoma. Results revealed that the S6K1 inhibitor LY-2779964 was relatively ineffective as a single agent, while S6K1-targeting AD80 induced cytotoxicity selectively in PTEN-deficient cells. In vivo, AD80 rescued 50% of mice transplanted with PTEN-deficient leukemia cells. Cells surviving LY-2779964 treatment exhibited inhibitor-induced S6K1 phosphorylation due to increased mTOR-S6K1 co-association, which primed the rapid recovery of S6K1 signaling. In contrast, AD80 avoided S6K1 phosphorylation and mTOR co-association, resulting in durable suppression of S6K1-induced signaling and protein synthesis. Kinome analysis revealed that AD80 coordinately inhibits S6K1 together with the TAM family tyrosine kinase AXL. TAM suppression by BMS-777607 or genetic knockdown potentiated cytotoxic responses to LY-2779964 in PTEN-deficient glioblastoma cells. These results reveal that combination targeting of S6K1 and TAMs is a potential strategy for treatment of PTEN-deficient malignancy.