An endothelial cell competition assay for determinants of the response to targeted anti-angiogenics

ABSTRACT/SUMMARYAnti-angiogenics, inhibitors of pathological blood vessel growth, are an important class of targeted agent for the treatment of common cancers and ocular conditions. However, efficacy is compromised by the absence of biomarkers to guide patient selection or inform the management of resistance. We describe an assay for modified endothelial cell (EC) responses to the VEGF-A-neutralizing monoclonal antibody bevacizumab as part of a biomarker discovery program. ECs are transduced by lentivector expressing an experimental or non-silencing shRNA, each co-expressed with a different fluorescent protein. A 1:1 mixed cell population is then cultured with bevacizumab or control antibody under VEGF-A-dependent conditions. A normalized ratio of surviving cells, obtained by flow cytometry analysis, reflects EC resistance or sensitization to bevacizumab mediated by the experimental shRNA. With reagents prepared, the protocol takes 10 days and rigorously quantifies the impact of gene perturbation on the EC response to bevacizumab or other targeted anti-angiogenics.