ESR1 and breast cancer: To examine whether paclitaxel and eribulin induce mitotic arrest in breast cancer cell lines, we selected typical subtypes of breast cancer cell lines, such as T47D (ER and PgR positive), SK-BR-3 (Her2 positive), and MDA-MB-231 (triple negative), and confirmed that both paclitaxel and eribulin induced mitotic arrest in all the breast cancer cell lines used, regardless of subtypes (Fig. 1B,C).