Development of a function-blocking antibody against fibulin-3 as a targeted reagent for glioblastoma
Purpose: We sought a novel approach against glioblastomas (GBM) focused on targeting signaling molecules localized in the tumor extracellular matrix (ECM). We investigated fibulin-3, a glycoprotein that forms the ECM scaffold of GBMs and promotes tumor progression by driving Notch and NFkB signaling. Experimental Design:Weused deletion constructs to identify a key signaling motif of fibulin-3. An mAb (mAb428.2) was generated against this epitope and extensively validated for specific detection of human fibulin-3. mAb428.2 was tested in cultures to measure its inhibitory effect on fibulin-3 signaling. Nude mice carrying subcutaneous and intracranial GBM xenografts were treated with the maximum achievable dose of mAb428.2 to measure target engagement and antitumor efficacy. Results: We identified a critical 23-amino acid sequence of fibulin-3 that activates its signaling mechanisms. mAb428.2 binds to that epitope with nanomolar affinity and blocks the ability of fibulin-3 to activate ADAM17, Notch, and NFkB signaling inGBM cells. mAb428.2 treatment of subcutaneous GBM xenografts inhibited fibulin-3, increased tumor cell apoptosis, and enhanced the infiltration of inflammatory macrophages. The antibody reduced tumor growth and extended survival of mice carrying GBMs as well as other fibulin-3-expressing tumors. Locally infused mAb428.2 showed efficacy against intracranial GBMs, increasing tumor apoptosis and reducing tumor invasion and vascularization, which are enhanced by fibulin-3. Conclusions: To our knowledge, this is the first rationally developed, function-blocking antibody against an ECM target in GBM. Our results offer a proof of principle for using "anti-ECM" strategies toward more efficient targeted therapies for malignant glioma. Clin Cancer Res; 24(4); 821-33.
Nandhu, Mohan S.; Behera, Prajna; Bhaskaran, Vivek; Longo, Sharon L.; Barrera-Arenas, Lina M.; Sengupta, Sadhak; Rodriguez-Gil, Diego J.; Chiocca, E. Antonio; and Viapiano, Mariano S.. 2018. Development of a function-blocking antibody against fibulin-3 as a targeted reagent for glioblastoma. Clinical Cancer Research. Vol.24(4). 821-833. https://doi.org/10.1158/1078-0432.CCR-17-1628 PMID: 29146721 ISSN: 1078-0432