KLK6 and breast cancer: KLK6 displays aberrant expression in various types of cancer, including breast cancer (Anisowicz et al., 1996; Haritos et al., 2018; Wang et al., 2008), head and neck squamous cell cancer (Schrader et al., 2015), renal cancer (Tailor et al., 2018), and colon cancer (Kim et al., 2011; Petrak et al., 2012).