While these studies were done using the MCF7 cell line, a metastatic cell line originating from pleural effusion [105], the work is highly correlative with other studies that reported a higher T2D incidence, metastasis, and mortality rates of invasive estrogen receptor–positive breast cancer in post-menopausal women when the diabetes is untreated by metformin [35,106]. The gene discussed is ESR1; the disease is type 2 diabetes mellitus.