Serine protease inhibitor Kazal type 1 (SPINK1) downregulates E-cadherin and induces EMT of hepatoma cells to promote hepatocellular carcinoma metastasis via the MEK/ERK signaling pathway

OBJECTIVE: To investigate serine protease inhibitor Kazal type 1 (SPINK1) expression and its influence on the prognosis of human hepatocellular carcinoma (HCC) and to explore the underlying molecular mechanisms involved. METHODS: Altogether 80 patients with HCC who underwent curative resection were followed up for a median of 58.6 months. SPINK1 expression was detected in the primary HCC samples by immunohistochemistry. Its role in tumor invasion and metastasis was evaluated in vitro by gene silencing using a small interfering RNA-mediated approach, recombinant SPINK1 and U0126 (an inhibitor of MEK/ERK). The proteins in the MEK/ERK signaling pathway were detected by Western blot. RESULTS: Patients with high SPINK1 expression showed poor overall survival (P = 0.0001) and recurrence-free survival (P = 0.001) compared with those with low SPINK1 expression. The suppression of SPINK1 resulted in reduced cell migration and invasion. SPINK1 overexpression was significantly associated with increased cell migration and invasion in vitro. Furthermore, SPINK1 promoted cancer cells motility and epithelial-mesenchymal transition (EMT) via the mitogen-activated protein kinase kinase (MAPK) and extracellular regulated kinase (ERK) pathway, resulting in increased vimentin expression and decreased E-cadherin expression. CONCLUSION: SPINK1 may be an oncogene that induces EMT via the MEK/ ERK pathway and is a potential target for HCC therapy.