PDTM-18. COMBINED SUPPRESSION OF THE mTOR AND MAPK PATHWAYS INHIBITS GROWTH, DECREASES VASCULARITY AND INDUCES APOPTOSIS OR SENESCENCE IN PEDIATRIC LOW GRADE GLIOMA
Year: 2019
Type: conference-abstract
Abstract: Pediatric low-grade glioma (pLGG) is the most common brain tumor in children. We and others have identified constitutive activation of the mTOR and MEK-pathway in pLGG. This led us to investigate TAK228, a mTORC1/2-inhibitor, and the FDA approved MEK-inhibitor, trametinib, in mono- and combination therapy in pLGG. We examined antitumor activity in four patient-derived pLGG cell models treated with TAK228, trametinib, and combination: JHH_NF1_PA1(NF1mut), BT40(BRAFV600E), Res186(PTEN-/-) and Res259(CDKN2A-/-). Treatment with TAK228 or trametinib reduced cell proliferation in a dose and time dependent manner (MTS-assay). The combination treatment exerted a synergistic effect at 5-20nM in JHH_NF1_PA1, Res186, and Res259 cells (Chou-Talay method). The combination of TAK228 and trametinib increased apoptosis by up to 127% (p< 0.001 by 1-way ANOVA) in Res186 and Res259 cells as measured by cleaved caspase 3 immunocytochemistry. Trametinib and combination treatment induces senescence in JHH_NF1_PA1 cell line verified through increase in p27 protein expression (Western Blot) and positive b-galactosidase staining. Mono-treatment with TAK228 or vehicle showed no signs of senescence. We tested trametinib and TAK228 against the mutant BT40BRAFV600E patient-derived cell line in immunodeficient mice. The combination treatment showed greater antitumor activity than that of either mono-treatment in vivo. BT40 tumor growth was significantly decreased in combination compared to vehicle or either agent alone (p< 0.01). Combination treatment strikingly reduced the vascularization in the tumor tissue after combination treatment analyzed by CD31 and CD34 protein expression (Western Blot), compared to vehicle and mono-treatment. Our study provides evidence that pLGG-derived cell lines in vitro and in vivo are sensitive to mTORC1/2 kinase inhibition and MEK inhibition. Combination treatment with TAK228 and trametinib had a significant anti-tumor activity in vivo shown in survival rate, decreased tumor size, and reduced vascularity. These results provide the first strong rationale for combination therapy with TAK228 and trametinib for clinical consideration in pLGG.
Source: Neuro-Oncology
Language: English
Subfield: Oncology
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2987238344