[Periplocin extracted from cortex periplocae induces apoptosis of SW480 cells through inhibiting the Wnt/beta-catenin signaling pathway]

Abstract

Background and objective: The Wnt/beta-catenin signaling pathway plays an important role in the development and progression of human cancers, especially in colorectal carcinomas. This study was to analyze the inhibition effect of periplocin extracted from cortex periplocae (CPP) on proliferation of human colon carcinoma cell line SW480 and the underlying mechanism.

Methods: Cell proliferation of SW480 cells was measured by MTT assay. Cell apoptosis and cell cycle were analyzed by flow cytometry. Protein expression of beta-catenin in total cell lysates, cytosolic extracts, and nuclear extracts were detected by Western blot. Binding activity of the T cell factor (TCF) complex in nucleus to its specific DNA binding site was measured by electrophoretic mobility shift assay (EMSA). Expressions of beta-catenin, survivin, c-myc and cyclin D1 mRNA in cells after the treatment with CPP were detected by semi-quantitative RT-PCR.

Results: CPP significantly inhibited the proliferation of SW480 cells in a time-and dose-dependent manner (P<0.01). CPP (0.5 microg/mL) also caused G0/G1 cell cycle arrest of SW480 cells and induced cell apoptosis (P<0.05). Compared to untreated control cells, after the treatment with CPP, the protein levels of beta-catenin in total cell lysates, cytosolic extracts, and nuclear extracts were reduced (P<0.01); the binding activity of the TCF complex in nucleus to its specific DNA binding site was suppressed; mRNAs of the downstream target genes survivin, c-myc and cyclin D1 were decreased (P<0.01) while beta-catenin mRNA remained unchanged.

Conclusion: CPP could significantly inhibit the proliferation of SW480 cells, which may be through down-regulating the Wnt/beta-catenin signaling pathway.