Recombinant human NRG1 was purchased from Cell Signaling Technology (Danvers, MA). Pertuzumab was obtained from the Thomas Jefferson University Pharmacy. huHER3-8, an ErbB3 antagonistic humanized antibody (22 (link)), was produced and purified at ImmunoGen, Inc. The monoclonal antibody, NG33, blocks NRG1 binding to the ErbB3 (25 (link)). Trametinib/GSK’212 and PD0325901 were purchased from Selleck Chemicals LLC (Houston, TX).