Polysaccharide from Phellinus linteus induces S-phase arrest in HepG2 cells by decreasing calreticulin expression and activating the P27kip1-cyclin A/D1/E-CDK2 pathway.

Abstract

ETHNOPHARMACOLOGY RELEVANCE:

Our previous study showed that the proteoglycan P1 from Phellinus linteus (Mesima) exhibits significant anti-tumor activity against human hepatocellular carcinoma cells (HepG2); however, its molecular mechanism remains unknown. This study aims to provide insights into the mechanism of the anti-tumor activity of P1 against HepG2 cells.

METHODS:

We examined the effects of P1 on HepG2 cell proliferation in vitro and in vivo. Flow cytometry was used to analyze the cell cycle distribution and apoptosis. Proteomic analysis, real-time (RT)-PCR, and Western blot were carried out to observe the expression of several cell cycle control proteins in HepG2 cells.

RESULTS:

Both the volume and the weight of solid tumors were significantly decreased in P1-treated mice (200mg/kg) compared with the control. The HepG2 cells in the P1-treated tumors were significantly decreased, irregularly shaped, and smaller. P1 slightly increased the body weight of the tumor-bearing mice, which indicates that P1 is nontoxic to mammals at 200mg/kg. P1 also caused a significant dose-dependent increase in S phase arrest, but no apoptosis was observed in HepG2 cells. The results of the proteomic analysis, RT-PCR, and Western blot analysis showed that significantly downregulated expression of calreticulin, cyclin D1, cyclin E, and CDK2 and upregulated expression of P27 kip1 and cyclin A in the P1-treated HepG2 cells (200 μg/ml).

CONCLUSION:

These results suggest that calreticulin expression and the P27 kip1-cyclin A/D1/E-CDK2 pathway were involved in P1-induced S-phase cell cycle arrest in HepG2 cells.

• Authors: You-Gui Li, Dong-Feng Ji, Shi Zhong, Pei-Gang Liu, Zhi-Qiang Lv, Jian-Xun Zhu, Jin-E Chen, Hua-Ping Chen
• Journal: Journal of ethnopharmacology (J Ethnopharmacol) Vol. 150 Issue 1 Pg. 187-95 (Oct 28 2013) ISSN: 1872-7573 [Electronic] Ireland
• PMID: 24001891 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2013 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Antineoplastic Agents
• Calreticulin
• Cyclins
• Fungal Polysaccharides
• Cyclin-Dependent Kinase Inhibitor p27
• CDK2 protein, human
• Cyclin-Dependent Kinase 2

Topics

• Animals
• Antineoplastic Agents (pharmacology, therapeutic use)
• Basidiomycota
• Calreticulin (metabolism)
• Cell Proliferation (drug effects)
• Cyclin-Dependent Kinase 2 (metabolism)
• Cyclin-Dependent Kinase Inhibitor p27 (metabolism)
• Cyclins (metabolism)
• Female
• Fungal Polysaccharides (pharmacology, therapeutic use)
• Hep G2 Cells
• Humans
• Mice
• Mice, Nude
• Proteomics
• S Phase (drug effects)
• Xenograft Model Antitumor Assays