KLK4 and inflammatory bowel disease: Kallikreins are expressed by goblet cells in rat, cat, and mouse intestines (Schachter et al., 1986; Grün et al., 2016), and have been implicated in inflammatory bowel disease and gastrointestinal cancers (Stadnicki, 2011; Kontos et al., 2013), suggesting additional conservation of planarian goblet cell physiology.