ERBB2 and breast carcinoma: MFB also exerted more potent cytotoxic effects against MDA-MB-453 Her2-positive breast cancer cells (IC50, 3.4 mM) and MDA-MB-231 TNBC (IC50, 9.2 mM) compared to metformin (IC50, 51.3 mM and 51.4 mM, respectively) (Table 1 and Figure 1C).