ERBB3 and cancer: Because this Ab has the ability to inhibit both ligand-dependent and -independent activation of erbB3 [93,94], we speculate that EV20 may have a much broader effect on blocking erbB3 signaling than those Abs (like MM-121) which only prevent ligand-induced activation of erbB3, and thus exert more potent activity to overcome drug resistance in cancer therapy.