Study On The Effect Of LoVo Cell Apoptosis Induced By Laminarin Via Death Receptor-Caspase Dependent Pathway

Laminarin is a polysaccharide composition contained in the genus Laminaria and other plants. The previous studies showed that Laminarin could inhibit the growth of human colon cancer LoVo cells, and had the effect of anti-tumor in vitro.Based on the previous studies, caspase dependent pathway and the apoptosis mechanism of LoVo cells induced by Laminarin were studied, using DR4, DR5/TRAIL pathway as the starting point. And this study can provide considerable guidance and evidence for the research and development and clinical application of anti-cancer effect of Laminarin.Detected by Western Blot laminarin-induced apoptosis in LoVo cells associated protein DR4, DR5 and TRAIL expression, the results show that, dose group of 400,800,1600μ/mL of laminarin in LoVo cells after 24h LoVo cells can significantly increase DR4, DR5, and TRAIL protein expression, the relative protein expression were DR4:107.57%,115.77%,117.35%; DR5:106.31%,134.02%,142.34%; TRAIL:106.96%,124.3%,173.37%, and was a dose-dependent, with the negative control group, a statistically significant difference (P<0.05).In addition, this experiment detected the protein of Bid which was a key elements that contacted death receptor with mitochondrion, Western Blot results showed that:dose group of 400,800,1600μg/mL of laminarin in LoVo cells after 24h LoVo cells can significantly increase Bid, tBid protein expression, respectively, relative protein expression Bid:144.25%,215.01%, 307.1%; tBid:229.58%,272.48%,299.72%, and a dose-dependent, with the negative control group, a statistically significant difference (P<0.05).We used colorimetric assay with the closely related apoptosis pathway, Caspase-9, Caspase-6, Caspase-7, three enzyme activity. The results showed that concentrations of dose group of 400,800,1600μg/mL of laminarin on LoVo cells 24h after the Caspase-9, Caspase-6, Caspase-7 of the relative activity with the increase of drug concentration increased, Caspase-9 relative activity were 117.28%,276.41%,387.06%, Caspase-6 relative activity were 137.04%, 253.77%,383.49%, Caspase-7 relative activity were 150.44%,342.44%,534.44%, with the negative control group were significantly differences (P＜0.01).Therefore, the mechanism laminarin induced colon cancer LoVo cell to apoptosis is that: (1)Starting the way of death acceptor by raising DR4, DR5/TRAIL, promoting pro-Caspase-8 split to catalytic activity Caspase-8, and then activating the next effector Caspase-3, Caspase-6, Caspase-7, to lead to apoptosis. (2) Activated Caspase-8 can incise Bid whose part can promote the releasing of Cyt-c from mitochondria, activate Caspase-9, and Caspase-3,Caspase-6, Caspase-7 further to apoptosis.