Induction of apoptosis signaling by glycoprotein of Capsosiphon fulvescens in human gastric cancer (AGS) cells.

Capsosiphon fulvescens is a well-known green sea algae that has been touted in recent years as a potential anticancer drug. In this study, C. fulvescens glycoprotein (Cf-GP) showed proapoptotic signaling in AGS cells. An MTS assay indicated that Cf-GP inhibited the proliferation of AGS cell lines in a dose-dependent manner. Cells were treated with Cf-GP and the expression of proteins associated with apoptosis was examined by Western blotting. Based on the Western blot, expression of Cf-GP-activated caspase-cascade and PARP, which is a substrate of caspase-3 and -8, and proteins of the Bcl-2 family was observed. Cf-GP treatment stimulated the release of cytochrome C and apoptotic protease activating factor-1 from mitochondria to the cytosol. Cf-GP inhibited the growth of AGS cells through induction of sub-G1 phase arrest. We confirmed that sub-G1-phase arrest was associated with a decrease in the expression of cyclin D, cyclin E, Cdk2, Cdk4, and Cdk6, and an increase in the protein levels of p21 and p27. As a result, the increased sub-G1 ratio appears to be inhibited by cell proliferation. Therefore, we can confirm apoptosis in the AGS cells. Our results suggest that Cf-GP could be a potential source of biofunctional material that shows anticancer effects in human gastrointestinal cancer.