ABSTRACT
Based on the Wnt inhibitors as potential targets in the development of anticancer agents, natural compounds were evaluated for ß-catenin-mediated transcriptional activity. A natural lignan hydnocarpin isolated from Lonicera japonica was considered a potential inhibitor for Wnt/ß-catenin signalings. The anti-proliferative activity of hydnocarpin was also found to be associated with the suppression of Wnt/ß-catenin-mediated signaling pathway in human colon cancer cells. These data suggest that hydnocarpin might be a novel Wnt inhibitor and has a potential of signaling regulator in ß-catenin-mediated signaling pathways.
Subject(s)
Antineoplastic Agents, Phytogenic/chemistry , Flavonolignans/chemistry , Lignans/chemistry , Wnt Proteins/metabolism , beta Catenin/metabolism , Antineoplastic Agents, Phytogenic/isolation & purification , Antineoplastic Agents, Phytogenic/toxicity , Axin Protein/antagonists & inhibitors , Axin Protein/genetics , Axin Protein/metabolism , Cell Line, Tumor , Cell Proliferation/drug effects , Colonic Neoplasms/metabolism , Colonic Neoplasms/pathology , Flavonolignans/isolation & purification , Flavonolignans/toxicity , Humans , Lonicera/chemistry , Lonicera/metabolism , RNA Interference , RNA, Small Interfering/metabolism , Wnt Signaling Pathway/drug effectsABSTRACT
The antiproliferative and antitumor activities of 2-hydroxycinnamaldehyde (1), a phenylpropanoid isolated from the bark of Cinnamomum cassia, were investigated using human colorectal cancer cells. Compound 1 exhibited antiproliferative effects in HCT116 colon cancer cells, accompanied by modulation of the Wnt/ß-catenin cell signaling pathway. This substance was found also to inhibit ß-catenin/T-cell factor (TCF) transcriptional activity in HEK293 cells and HCT116 colon cancer cells. Further mechanistic investigations in human colon cancer cells with aberrantly activated Wnt/ß-catenin signaling showed that 1 significantly suppressed the binding of ß-catenin/TCF complexes to their specific genomic targets in the nucleus and led to the down-regulation of Wnt target genes such as c-myc and cyclin D1. In an in vivo xenograft model, the intraperitoneal administration of 1 (10 or 20 mg/kg body weight, three times/week) for four weeks suppressed tumor growth in athymic nude mice implanted with HCT116 colon cancer cells significantly, without any apparent toxicity. In an ex vivo biochemical analysis of the tumors, compound 1 was also found to suppress Wnt target genes associated with tumor growth including ß-catenin, c-myc, cyclin D1, and survivin. The suppression of the Wnt/ß-catenin signaling pathway is a plausible mechanism of action underlying the antiproliferative and antitumor activity of 1 in human colorectal cancer cells.
Subject(s)
Antineoplastic Agents/pharmacology , Cinnamates/pharmacology , Animals , Antineoplastic Agents/chemistry , Apoptosis/drug effects , Cell Proliferation/drug effects , Cinnamates/chemistry , Cinnamomum aromaticum/chemistry , Colonic Neoplasms/genetics , Colonic Neoplasms/metabolism , Colonic Neoplasms/pathology , Cyclin D1/metabolism , HCT116 Cells , Humans , Mice , Molecular Structure , Plant Bark/chemistry , Signal Transduction/drug effects , TCF Transcription Factors/metabolism , Wnt Signaling Pathway/drug effects , beta Catenin/genetics , beta Catenin/physiologyABSTRACT
Abnormal activation of the canonical Wnt/ß-catenin pathway and up-regulation of the ß-catenin/T-cell factor (TCF) response to transcriptional signaling play a critical role early in colorectal carcinogenesis. Therefore, Wnt/ß-catenin signaling is considered an attractive target for cancer chemotherapeutic or chemopreventive agents. Small molecules derived from the natural products were used in our cell-based reporter gene assay to identify potential inhibitors of Wnt/ß-catenin signaling. Magnolol, a neolignan from the cortex of Magnolia obovata, was identified as a promising candidate because it effectively inhibited ß-catenin/TCF reporter gene (TOPflash) activity. Magnolol also suppressed Wnt3a-induced ß-catenin translocation and subsequent target gene expression in human embryonic kidney 293 cells. To further investigate the precise mechanisms of action in the regulation of Wnt/ß-catenin signaling by magnolol, we performed Western blot analysis, real-time reverse transcriptase-polymerase chain reactions, and an electrophoretic mobility shift assay in human colon cancer cells with aberrantly activated Wnt/ß-catenin signaling. Magnolol inhibited the nuclear translocation of ß-catenin and significantly suppressed the binding of ß-catenin/TCF complexes onto their specific DNA-binding sites in the nucleus. These events led to the down-regulation of ß-catenin/TCF-targeted downstream genes such as c-myc, matrix metalloproteinase-7, and urokinase-type plasminogen activator in SW480 and HCT116 human colon cancer cells. In addition, magnolol inhibited the invasion and motility of tumor cells and exhibited antitumor activity in a xenograft nude mouse model bearing HCT116 cells. These findings suggest that the growth inhibition of magnolol against human colon cancer cells can be partly attributed to the regulation of the Wnt/ß-catenin signaling pathway.
