Moreover, the expression level of ERα-36 has been shown to correlate with a worse prognosis, the proposed mechanisms being, in spite of the LBD truncation, estrogen-dependent stimulation of mitogen signaling activity, activation by antiestrogens such as tamoxifen, and increased stemness and metastasis of breast cancer through upregulation of the aldehyde dehydrogenase 1A1 (ALDH1A1) gene [108,109]. This evidence concerns the gene ESR1 and breast cancer.