CST3 and neoplasm: On the other hand, one has to be aware that cysteine proteases and consequently their inhibitors are also involved in biological processes other than tissue remodelling during the progression of primary tumours, such as the regulation of inflammatory and immune responses (Chapman et al, 1997) or apoptosis (Jaattela, 1999), so that the lack of cystatin C at the systemic level may lead to a lower metastatic spread compared to wild-type animals.