IFNG and breast cancer: IFNγ and phenformin also cooperatively elicit antitumorigenic responses in murine ErbB2+ (NOP6, NOP23, and NIC) (Fig. 1b) and human breast cancer cell lines representative of ER+/HER2− (MCF7), HER2+ (HCC1954, BT474), and triple-negative (MDA-MB-231, BT20, MDA-MB-436, Hs578T, and BT549) disease (Fig. 1c).