SIRPA and breast carcinoma: To determine whether BC31M4 binds to the cell-surface CD47 and blocks the CD47-SIRPα interaction in a pH-dependent manner, a flow cytometry-based binding and blocking assay was performed to evaluate the binding and blocking activity of antibodies to different cells, including a CHO cell line stably expressing full-length human CD47 (CHO-hCD47), Raji (B lymphoma), Jurkat (T lymphoma) and MDA-231 (breast cancer) cells, at pH 6.8 and pH 7.4 conditions separately.