Metformin and an insulin/IGF-1 receptor inhibitor are synergistic in blocking growth of triple-negative breast cancer.

We conclude that the combination of metformin and BMS-754807 is more effective than either drug alone in inhibiting cell proliferation in the majority of TNBC cell lines, and that one important mechanism may be suppression of SCFSkp2 and subsequent stabilization of the cell cycle inhibitor p27Kip1. This combination treatment may represent an effective targeted therapy for a significant subset of TNBC cases and should be further evaluated.