ESR1 and breast cancer: Also, the results appeared that the expression of circCNIH4 in estrogen receptor positive breast cancer cell lines(MCF-7, ZR-75) were significantly upregulated comparing to aggressive triple negative breast cancer cells(MDA-MB-231, SUM1315, Hs578T) and her-2 positive breast cancer cell line (SkBr-3) (Fig. 5E).