ESRP1 and breast carcinoma: Furthermore, we found that compared with si-NC, ESRP1 knockdown dramatically decreased circANKS1B production in breast cancer cells transfected with wild-type or individually mutation circANKS1B minigenes, whereas had little or no effect on circANKS1B production in cells transfected with a/b or (and) c/d mutation minigenes (Fig. 6d), suggesting that these four motifs on flanking introns are necessary for ESRP1-mediated circANKS1B biogenesis.