ADAM10 is a transmembrane metalloprotease that sheds cell surface proteins, regulating key oncogenic signalling pathways, including via Notch, EGFR/erbB and Eph receptors, which are upregulated in cancers. ADAM10 itself is over-expressed in cancer, including the aggressive brain cancer glioblastoma (GBM) where it is associated with poor patient prognosis. Thus ADAM10 is an attractive target for potential anti-cancer therapies.
We have previously generated a monoclonal antibody (mAb 8C7) against the ADAM10 substrate-binding domain1. 8C7 displayed novel selectivity for an active conformation of ADAM10 preferentially found in tumours compared to normal tissues. In a mouse colon cancer model, 8C7 preferentially bound tumour cells with high notch activity which it inhibited2.
To determine the role of ADAM10 in GBM we generated ADAM10-/- U251 GBM cell lines. Analysis of conditioned medium from ADAM10-/- U251 cells via mass spectrometry showed significant reduction in proteins associated with diverse functions, most prominently cell adhesion and migration, in addition to proliferation. ADAM10-/- U251 cells also displayed reduced proliferation and invasion in vitro. In subcutaneous U251 xenograft tumours grown in NSG mice, growth of ADAM10-/- U251 lines was consistently heavily reduced, and some tumours showed evidence of differentiation, associated with less aggressive tumours.
We are also exploiting the specificity of our ADAM10 antibody 8C7 to develop antibody-drug-conjugates (ADCs), to preferentially kill tumour cells with high ADAM10 activity. 8C7 ADCs were generated with different payloads and tested in vitro against a cell line overexpressing ADAM10 with the 8C7 epitope exposed, demonstrating specific cytotoxic activity, which was most potent with a payload of the DNA-binding agent Pyrrolobenzodiazepine (PBD). Importantly, 8C7-PBD also most effectively inhibited growth of human GBM and colon xenografts in mice. Therapeutic potential of anti-ADAM10 ADCs is now being investigated.