A Monoclonal Antibody Against β1 Integrin Inhibits Proliferation and Increases Survival in an Orthotopic Model of High-Grade Meningioma.

High-grade meningiomas (HGMs; World Health Organization [WHO] classification grade II and III) have high relapse rates and poor clinical outcomes despite surgery and radiation treatments. No effective medical therapy currently exists for HGMs, and developing novel therapeutic strategies depends on the identification of molecular drivers. In cancer, β1 integrin enhances malignant characteristics, including proliferation, invasion, and drug resistance. We conducted this study to investigate whether β1 integrin could be a therapeutic target in HGMs. Expression of β1 integrin was examined in gene array datasets, with proteomics of clinical meningioma specimens, and in patient-derived HGM xenografts. Anti-tumor activity of OS2966, a first-in-class humanized antagonizing monoclonal antibody against β1 integrin, was tested in vitro and in vivo using an orthotopic mouse model of patient-derived malignant meningioma. β1 integrin was expressed in meningiomas of all WHO grades and two xenografts tested. In vitro, OS2966 suppressed the viability of NF2-deficient MN3 sphere cells and NF2-wild-type IOMM-Lee malignant meningioma cells only when plated on laminin-coated plastic. While OS2966 decreased phosphorylation of ERK1/2 in both MN3 cells and laminin-grown IOMM-Lee cells, OS2966 only affected the phosphorylation of FAK (Tyr397) in MN3, and of Akt (Ser473) in IOMM-Lee cells, respectively, indicating differential pathway inhibition. Systemic administration of OS2966 in mice bearing orthotopic MN3 HGMs inhibited HGM cell proliferation and significantly extended overall survival of the treated mice. β1 Integrin may be a therapeutic target in HGMs, and further preclinical and clinical development of OS2966 for HGM therapy is warranted.