The Structure-Activity Relationship and Molecular Mechanism of Anti-tumor Polysaccharide Isolated from Dendrobium nobile Lindl.

In this study, structure-activity relationship and molecular mechanism of anti-tumor polysaccharide isolated from the stems of Dendrobium nobile Lindl. were investigated. The sulfate and enzymatic analysis were employed to modify polysaccharide DNP-W1A, a fraction of polysaccharide isolated from D. nobile. Nine sulfated derivative fragments (S1–S9) and three fragments after enzymatic digestion (PE1, PE2 and PE3) were obtained using chloro-sulfonic acid and enzymatic methods, respectively. The activities experiment demonstrated that S1–S9, PE1, PE2 and PE3 showed significant anti-tumor activities in a dose-dependent manner (P < 0.05) in vitro. Annexin-FITC/PI results indicated that PE2 promoted the apoptosis of HepG2 cells at the highest rate of 19.3% compared with other fragments. Also, PE2 significantly increased the gene expression levels of Bax, Caspase-3 and Caspase-9 and suppressed the gene expression of Bcl-2 (P < 0.01). Meanwhile, HepG2 cells treated with polysaccharide resulted in suppressed P-AKT expression, and PE2 induced the lowest protein level of P-AKT compared with other fragments. The results concluded that polysaccharide DNP-W1A and its derivatives induced HepG2 cells apoptosis by up-regulating the gene expressions of Bax, Bcl-2, Caspase-3 and Caspase-9 and inhibiting the PI3K/AKT signaling pathway.