ERBB2 and breast cancer: In addition, the expression of circCDYL was detected by qRT-PCR in normal mammary epithelial cells (MCF-10A), HER2– BC cell lines (MCF-7, MDA-MB-231, and ZR75-1) and HER2+ BC cell lines (AU565, MDA-MB-361, SK-BR-3, BT474).