Antitumor activity of a sulfated polysaccharide from Enteromorpha intestinalis targeted against hepatoma through mitochondrial pathway

A sulfated polysaccharide (EI-SP), extracted from Enteromorpha intestinalis that is a kind of algae, is found to have anticancer activity. This study was designed to investigate the anti-tumor effect of EI-SP on human hepatoma HepG2 cell line and its possible mechanisms. An MTT assay showed that EI-SP could specifically inhibit the growth of human hepatoma HepG2 cells in a dose-dependent manner. Analysis by flow cytometry indicated that the apoptosis of tumor cells increased after treatment with EI-SP in range of 100–400 μg/ml. Furthermore, Western blot analysis showed that EI-SP treatment led to decreased protein expression of Bcl-2 and an increase in Bax, cleaved caspase-3, cleaved caspase-9 and cleaved poly(ADP-ribose) polymerase (PARP). Moreover, it was found that EI-SP caused a loss of mitochondrial membrane potential (Δψ m) and the release of cytochrome c to the cytosol. Collectively, our results showed that the EI-SP induces apoptosis in HepG2 cells involving a caspases-mediated mitochondrial signalling pathway.