In this regard, it is possible that kallikreins may have a function in chemotherapy-resistant tumours, as it has already been proposed for kallikreins 3 (Foekens et al, 1999) and 10 (Luo et al, 2002) in breast cancer and kallikrein 4 in ovarian cancer (Xi et al, 2004). Here, KLK4 is linked to breast cancer.