ERBB2 and breast cancer: To determine how best to use G28UCM either as a single agent or in combination with anti-HER drugs, we conducted a series of in vitro studies to evaluate the inhibitory effects of G28UCM in combination with trastuzumab, cetuximab, erlotinib, gefitinib and lapatinib in a pre-clinical model of HER2-overexpressing breast cancer cells.