ESR1 and breast cancer: As oestrogen is a stimulant for the initiation and promotion of breast cancer, and ERα can be expressed in gastric cancer cells, it has been suggested that the ERα pathway may have a role in the progression of gastric cancer (Harrison et al, 1989b; Wu et al, 1994; Karat et al, 1999; Takano et al, 2002; Chandanos et al, 2008).