A pectin-like polysaccharide from Polygala tenuifolia inhibits pancreatic cancer cell growth in vitro and in vivo by inducing apoptosis and suppressing autophagy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant carcinomas, which is characterized by apoptosis- and autophagy-dependent tumorigenic growth. Autophagy constitutes a stress adaptation that suppresses apoptosis. To explore new leading compound against PDAC, a pectin-like polysaccharide named RP02-1, was purified from roots of Polygala tenuifolia. Bioactivity test showed that RP02-1 might inhibit pancreatic cancer cells growth in vitro and in vivo. RP02-1 could inhibit pancreatic cancer cell (AsPC-1 and BxPC-3) proliferation, migration and colony formation. Mechanism study suggested that RP02-1 induced pancreatic cancer cells apoptosis, which was detected by Bcl-2 down-regulation, Bax up-regulation and conversion from Caspase 3 to Cleaved Caspase 3. Interestingly, autophagy was suppressed by RP02-1 treatment concentration-dependently through affenuatingBeclin-1, ATG5 and LC3B expression in BxPC-3 cells. In addition, RP02-1 could inhibit autophagy induced by Pennogenin 3-O-beta-chacotrioside. However, RP02-1 had almost no toxicity both in vitro and in vivo. The above results suggested that RP02-1 might be a potential leading compound for new drug candidate development for human PDAC treatment via inducing apoptosis and against autophagy.

Keywords: Apoptosis; Autophagy; Pancreatic cancer; Pectin; Polygala tenuifolia.