ESR1 and ductal breast carcinoma in situ: To assess EREG expression in additional breast cancer cell lines, EREG expression levels were examined in additional cell lines including MCF10AT, an HRAS-transformed derivative of the MCF10A cell line, MCF7, an estrogen receptor positive cell line, SUM225, another cell line capable of forming DCIS-like lesions in vivo and MDA-MB-231, a triple negative invasive cell line.