Global gene expression analysis identified gene expression patterns associated with the response of ERβ1- or ERβ2-expressing MCF7 cells to the combination of OHT with ATRA, which suggest that ERβ1 and ERβ2 could function as predictors of therapeutic and adverse responses, respectively, of early-stage ERα-positive BC to antiestrogens alone or in combination with ATRA. Here, ESR1 is linked to breast cancer.