Interestingly, we show that progesterone opposes the DSCAM-AS-1–ESR1 feedback loop, and thus essentially the ER signaling pathway, by employing two synergistic mechanisms—it decreases the expression of DSCAM-AS1 and increases the expression of miR-130a that binds to both DSCAM-AS1 and 3’UTR of ESR1 in breast cancer cells. This evidence concerns the gene DSCAM and breast cancer.