Silibinin, a natural flavonoid, modulates the early expression of chemoprevention biomarkers in a preclinical model of colon carcinogenesis

Abstract

The flavonolignan silibinin, the major biologically active compound of the milk thistle (Silybum marianum), has been shown to possess anticancer properties in a variety of epithelial cancers. The present study investigated the potential of silibinin as a chemopreventive agent in colon carcinogenesis. The rat azoxymethane (AOM)-induced colon carcinogenesis model was used because of its molecular and clinical similarities to sporadic human colorectal cancer. One week after AOM injection (post-initiation), Wistar rats received daily intragastric feeding of 300 mg silibinin/kg body weight per day until their sacrifice after 7 weeks of treatment. Silibinin-treated rats exhibited a 2-fold reduction in the number of AOM-induced hyperproliferative crypts and aberrant crypt foci in the colon compared to AOM-injected control rats receiving the vehicle. Silibinin-induced apoptosis in the colon mucosal cells was demonstrated by flow cytometry after propodium iodide staining and by colorimetric measurement of caspase-3 activity. Mechanisms involved in silibinin-induced apoptosis included the downregulation of the anti-apoptotic protein Bcl-2 and upregulation of the pro-apoptotic protein Bax, inverting the Bcl-2/Bax ratio to <1. This modulation already takes place at the mRNA expression level as shown by real-time RT-PCR. Furthermore, silibinin treatment significantly (P<0.01) decreased the genetic expression of biomarkers of the inflammatory response such as IL1β, TNFα and their downstream target MMP7, all of them shown to be upregulated during colon carcinogenesis. The downregulation of MMP7 protein was confirmed by western blot analysis. The present findings show the ability of silibinin to shift the disturbed balance between cell renewal and cell death in colon carcinogenesis in rats previously injected with the carcinogen AOM. Silibinin administered via intragastric feeding exhibited potent pro-apoptotic, anti-inflammatory and multi-targeted effects at the molecular level. The effective reduction of preneoplastic lesions by silibinin supports its use as a natural agent for colon cancer chemoprevention.

Milk Thistle (Silybum Marianum) as a Supportive Phytotherapeutic Agent in Oncology

“…In vivo studie na potkanech zkoumaly efekt podá-vání per os silymarinu po vystavení kancerogennímu azoxymethanu, který navozuje vznik adenokarcinomu v oblasti kolon. Výsledkem byl nižší výskyt prekancerotických změn ve tkáni tlustého střeva [18,19], při delším sledování i incidence a multiplicita karcinomu [19]. tkáni a v normální tkáni.…”

Dietary Non-nutritive Factors in Targeting of Regulatory Molecules in Colorectal Cancer: An Update

“…Wesolowska et al (2012) reported that multidrug resistance reversal and apoptosis induction in human colon cancer cells. Silibinin a natural flavonoid, treatment induced the upregulation of the pro-apoptotic Bax protein and gene expression and the reversal of the Bcl-2/Bax ratio (Kauntz et al, 2012). Diallyl sulfide, a garlic derived organo sulphur compound induces apoptosis mediated through the activation of caspase (Sriram et al, 2008).…”

Silibinin Induces Cell Death through Reactive Oxygen Species–Dependent Downregulation of Notch-1/ERK/Akt Signaling in Human Breast Cancer Cells

“…Many studies have shown that silibinin has anticancer activities in various cancer cells such as colon, prostate, skin, glioma, and breast cancer cells, and the effect mainly results from targeting proliferation, inflammation, apoptosis, and cancer cell metabolism (Deep et al, 2011;Jeong et al, 2011;Kim et al, 2011;Kauntz et al, 2012). However, an underlying mechanism of changes induced by silibinin has not been clearly elucidated.…”