Mitogen-activated protein kinase inhibition enhances the antitumor effects of sporamin in human pancreatic cancer cells

Sporamin, a sweet potato tuber storage protein, is a Kunitz-type trypsin inhibitor (TI) that has exhibited antitumor activity through poorly defined mechanisms in a number of types of tumor cells. The present study aimed to analyze the combined effects of sporamin and three mitogen-activated protein kinase (MAPK) inhibitors, PD98059, SP600125 and SB203580, on the pancreatic cancer cell line, PANC-1. Cell proliferation activity was assessed using a ³H-thymidine incorporation assay, and cell viability was analyzed using an MTT assay. Apoptosis was assayed by flow cytometry and fluorescence microscopy. Protein expression levels in PANC-1 cells were determined by western blotting. The results of this analysis demonstrated that sporamin induced a temporary increase in the phosphorylation of MAPKs, including phosphorylated extracellular signal regulated-kinase 1/2, phosphorylated c-Jun amino-terminal protein kinase 1/2 and phosphorylated p38-MAPK, in a concentration-dependent manner. However, treatment with MAPK inhibitors promoted the inhibition of cell proliferation and viability, and the induction of apoptosis in sporamin-treated PANC-1 cells. In conclusion, the present study demonstrated that MAPK inhibition enhanced the antitumor activity of sporamin in PANC-1 cells.