ERBB2 and ductal breast carcinoma in situ: To examine the possible clinical relevance of CDC20 in breast cancer development and drug resistance, we measured the protein expression levels of CDC20 in the normal breast epithelial (MCF-10A), the ductal carcinoma in situ (DCIS), and different breast cancer cell lines, including TNBC, HER2+, and Luminal subtypes (Figure 1a).