For example, in 2012, researchers found that the expression of EpCAM, a common antigen used for CTC detection, was downregulated in CTCs from breast cancer patients who had received chemotherapy.275,276 Similarly, a study reported that CTCs from breast patients who received anti-HER-2 therapy reduced their expression of HER-2, another common antigen.277–279. This evidence concerns the gene EPCAM and breast carcinoma.