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.

Sporamin suppresses growth of human esophageal squamous cell carcinoma cells by inhibition of NF­κB via an AKT­independent pathway.

The aim of the present study was to determine whether sporamin, a trypsin inhibitor, suppresses the growth of human esophageal squamous cell carcinoma (ESCC) cells in vitro. Sporamin treatment led to the suppression of viability and proliferation of human ESCC cell lines, EC9706 and EC109, as determined by MTT and [3H] thymidine incorporation assays, respectively. Flow cytometry and fluorescence microscopy demonstrated that sporamin significantly induced apoptosis in EC9706 and EC109 cells. Western blotting demonstrated that sporamin downregulated the expression of Bcl­2 and Bcl­2 like 1, and upregulated the expression of Bcl­2­associated X in EC9706 and EC109 cells. In addition, marked inhibition of nuclear factor (NF)­κB activation was observed in sporamin­treated EC9706 and EC109 cells by an electrophoretic mobility shift assay. Sporamin treatment also resulted in reduced expression levels of phosphorylated (p)­NF­κB inhibitor α and nuclear NF­κB p65. However, the expression levels of p­protein inase (AKT) and its downstream target, p­p70 S6 kinase, were not markedly altered following sporamin treatment. In conclusion, sporamin may suppress the growth of human ESCC cells via NF­κB­dependent and AKT­independent mechanisms and may act as a promising natural therapeutic agent for the treatment of human ESCC.