LGG-13. SYNERGISTIC TREATMENT FOR PEDIATRIC LOW GRADE GLIOMA WITH THE DUAL MTORC1/2 INHIBITOR TAK-228 AND MEK INHIBITOR TRAMETINIB

Abstract

AbstractPediatric low-grade glioma (PLGG) is one of the most common childhood tumors. If the tumor is located in a brain region that is not accessible for surgical resection, additional therapies are needed. Recent studies highlighted the important role of mTORC and MEK-activation in PLGG. The dual mTORC1/2-inhibitor, TAK-228, and MEK-inhibitor, trametinib, are promising candidates for targeted therapy. We hypothesized that TAK-228 and trametinib would show synergistic effects in vitro and in vivo in PLGG models. We treated the PLGG-derived cell lines Res186 and Res259 and our human MAP-kinase-driven glioma model with TAK-228 and trametinib. Cell growth was investigated using MTT-assay, DNA replication with bromodeoxyuridine (BrdU) assay, and apoptosis through cleaved-caspase-3 (CC-3) staining. Activation of MAPK pathway was detected via Western Blot by pERK and mTOR pathway by pAKT, pS6, and p4E-BP1 to total protein amount, and β-actin. Synergy was calculated with the Chou-Talalay method. Treatment of Res186 and Res259 with TAK-228 or trametinib reduced cell growth and proliferation in a dose- and time-depended manner. The combination of TAK-228 (20nM) and trametinib (100nM) resulted in a synergistic effect in Res259. No synergy was detected for Res186. Staining for CC-3 showed a significant increase for apoptosis in Res259 after treatment with TAK-228 or trametinib (**p<0.01). No positive CC-3 staining was detected in Res186 after drug treatment. MAPK pathway was inactivated in a dose-depend manner after trametinib and mTOR pathway was inactivated after treatment with TAK-228 in both cell lines. Our human neural stem cells similarly showed similar reductions in BrdU incorporation (**p<0.01) and CC-3 (*p<0.05). Our preliminary results show that our used PLGG-models are sensitive to TAK-228 and trametinib treatment. All cell lines showed decreased proliferation at various doses of either inhibitor. Synergy was seen for Res259 cells. We will now investigate both drugs in vivo using a BRAFV600E mutation glioma xenograft.