It was first isolated in human pancreatic tissue and fluid.[53] As a minor component of pancreatic juice, PRSS3 only accounts for ≈0.5% of the secreted proteins in a normal human pancreas, while the proportions of PRSS1 and PRSS2 are 13% and 6%, respectively.[54] Notably, mesotrypsin is resistant to almost all natural trypsin inhibitors, such as soybean trypsin inhibitor or human pancreatic secretory trypsin inhibitor (SPINK1).[55] PRSS3 has a controversial role in cancer. Here, PRSS1 is linked to cancer.