Effects of sulfated polysaccharide from Masson pine (Pinus massoniana) pollen on the proliferation and cell cycle of HepG2 cells

Aim: To explore the inhibitory effect of sulfated polysaccharide from Masson pine (Pinus massoniana) pollen (SPPM60) on G(2)/M phase of human liver cancer HepG2 cells and its mechanism. Methods: The proliferation rate of HepG2 cells was evaluated by methyl thiazolyl tetrazolium (MTT) colorimetric assay. The cycles of HepG2 cells were measured by flow cytometry when 200 mu g/ml concentration of SPPM60 was adopted, the expression of the genes related to cell cycle was detected by real-time PCR. Results: SPPM60 inhibited the proliferation of HepG2 cells and the inhibition rate was elevated with increase of SPPM60 concentration. After treatment with 200 mu g/ml of SPPM60, the percentage of S phase cells was decreased, but that of G(2)/M phase was significantly increased (72 h vs control: 32.96 +/- 0.33% vs 18.59 +/- 0.04%, 3.44 +/- 0.05% vs 18.30 +/- 0.08%, P < 0.01). The results of real-time PCR showed that SPPM60 could down-regulate the mRNA levels of CDK1 and CyclinB (P < 0.01), and up-regulate the expression of p53 and p21 (P < 0.05). Conclusion: SPPM60 causes arrest of HepG2 cells at G(2)/M phase, and the mechanism is related to the down-regulation of CDK1 and CyclinB and up-regulation of p53 and p21 expression. (C) 2012 Elsevier B.V. All rights reserved.