Combining brigatinib with mTOR inhibition to effectively treat NF2-SWN-associated and sporadic NF2-deficient meningiomas

We previously generated an orthotopic, NF2-deficient meningioma model using the luciferase-expressing Ben-Men-1 cell line established from a sporadic tumor and identified the multi-kinase inhibitor brigatinib and the mTOR kinase inhibitor INK128 to potently impede tumor growth. Here, we describe generation of the telomerase-immortalized AG-NF2-Men cell line from a grade-1 meningioma of an NF2-related schwannomatosis (NF2-SWN) patient. We showed that like Ben-Men-1 cells, AG-NF2-Men cells were NF2-null, expressed several NF2-regulated receptor tyrosine kinases, and responded to their cognate ligands. We also found that brigatinib and INK128 alone inhibited AG-NF2-Men cell proliferation at IC50 values similar to those in Ben-Men-1 cells. Combining brigatinib with INK128 exhibited growth-inhibitory synergy. Mechanistically, the combination not only completely abrogated p-AKT(S473) and its downstream signaling compared to either drug alone but also prevented INK128-mediated re-phosphorylation of AKT on T308. Also, the combination more-effectively blocked ligand-mediated phosphorylation of EGFR, ErbB3, and IGF-1R and elicited major changes in the expression of genes including the upstream regulators of several signaling networks important for meningioma growth. Further, we generated luciferase-expressing AG-NF2-Men cells that readily grew as intracranial xenografts. Importantly, combining brigatinib with INK128 enhanced tumor regression in both the orthotopic AG-NF2-Men and Ben-Men-1 xenograft models. As the first NF2-SWN-related meningioma cell line, AG-NF2-Men is a unique reagent for investigating meningioma biology and therapeutics. A clinical trial to evaluate the combination of brigatinib with an mTOR inhibitor in NF2-deficient meningiomas is warranted.