Regarding breast cancer subclasses, the AhR/GPR30 gene expression signature was more informative in the ER-negative (p = 0.001) than in the ER-positive (p = 0.41) (Table 1, Figures 7D,E) or luminal subclasses and (p = 0.50) (Table 1). This evidence concerns the gene GPER1 and breast cancer.