CST6 and breast cancer: Zhang et al. (2004) found that CST6 was consistently expressed in normal human breast epithelial cells, while it was decreased in breast invasive carcinoma samples, and the expression of CST6 was associated with cell proliferation, migration, and invasion. The CST6 promoter was found highly methylated in cfDNA of breast cancer plasma cells but not in healthy samples (Chimonidou et al., 2013). Moreover, IL-17A, an immunotherapy targeting, could affect keratinocyte differentiation by regulating the expression of CST6 (Sato et al., 2020).