In estrogen/progesterone receptor positive human breast cancer cell lines (MCF7) and estrogen receptor/progesterone receptor/human epidermal growth factor receptor 2 negative cell lines (MDA-MB-231), metformin has an inhibitory effect on mTORC1, which is an essential switch of tumor growth (Jahani and Davoodi, 2022). The gene discussed is ERBB2; the disease is breast cancer.