ERBB2 and breast cancer: As expected, compared with the human breast epithelial cells MCF10A, circ-ERBB2 expression was enhanced in the HER2-positive breast cancer cells SKBR3 and BT-474 and was lessened in the HER2-negative breast cancer cells MDA-MB-468 and the HER2-positive breast cancer cells SKBR3 and BT-474 were applied for the follow-up study (Fig. 2A).