Roles of serine protease inhibitor Kazal type 1 (SPINK1) in pancreatic diseases.

Serine protease inhibitor Kazal type 1 (SPINK1) was originally identified as a trypsin inhibitor by Kazal et al. in 1948. SPINK1 is strongly elevated in pancreatitis and the elevation correlates with the severity of disease. In 2000, mutations in the SPINK1 gene were shown to be associated with chronic pancreatitis. Since then, there have been many reports on association between mutations in the SPINK1 genes and patients with pancreatitis. In 1982, SPINK1 was shown to be identical to tumor associated trypsin inhibitor (TATI). In addition, sequence similarities were detected between human epidermal growth factor (EGF) and human SPINK1 in 1983. Actually, SPINK1 was shown to stimulate growth of several cell lines including cancer cells in 1985. Recent clinical studies showed that high levels of SPINK1 protein in serum or urine were associated with adverse outcome in various cancer types. However, there was little evidence that showed in vivo function of SPINK1. Surprisingly, mice deficient in Spink3 (a mouse homologue gene of human SPINK1) showed excessive autophagy, but not pancreatitis in the exocrine pancreas, leading to autophagic cell death. We also demonstrated that SPINK1 acts as a growth factor through EGFR signaling. These data indicate that the role of the SPINK1 is not just as a trypsin inhibitor, but also as a growth factor as well as a negative regulator of autophagy. In this review, we summarize the roles of SPINK1/Spink3 in pancreatic diseases based on the data obtained from analyses using mouse models.