The endocrine disruptive chemicals, such as bisphenol (Figure 1) and thiodiphenol, at the environmentally relevant doses may exert effects through the GPER and estrogen-like signaling pathways, contribute to breast cancer progression, and drug resistance in both the ERα-positive and -negative breast cancer cells [41,42,43,44,45]. The gene discussed is GPER1; the disease is breast cancer.