Silibinin Inhibits Established Prostate Tumor Growth, Progression, Invasion, and Metastasis and Suppresses Tumor Angiogenesis and Epithelial-Mesenchymal Transition in Transgenic Adenocarcinoma of the Mouse Prostate Model Mice
The chronic nature of prostate cancer growth and progression leading to metastasis provides a large window for intervention. Herein, for the first time, we investigated the effect and associated mechanisms of silibinin phosphatidylcholine (silybin-phytosome) on established prostate tumors in transgenic adenocarcinoma of the mouse prostate (TRAMP) model.
Twenty-week-old TRAMP male mice having palpable prostate tumor were fed with control or 0.5% and 1%, w/w, silybin-phytosome diets for 11 weeks and then sacrificed.
Dietary silibinin inhibited the growth of prostate tumors (up to 60%, P < 0.001) and suppressed tumor progression from prostatic intraepithelial neoplasia to differentiated adenocarcinoma and poorly differentiated adenocarcinoma, with a complete absence of poorly differentiated adenocarcinoma at higher doses. It also inhibited the incidence of tumor invasion of seminal vesicle (up to 81%, P < 0.001) with complete absence of distant metastasis. Silibinin moderately inhibited tumor cell proliferation and induced apoptosis, but strongly suppressed tumor microvessel density (up to 60%, P < 0.001), vascular endothelial growth factor, and vascular endothelial growth factor receptor-2 expression. Antibody array analysis of plasma showed a decrease in the circulatory levels of vascular endothelial growth factor and basic fibroblast growth factor. Decreased levels of matrix metalloproteinases (MMP), snail-1, and vimentin, and an increased level of E-cadherin were also observed, indicating the anti-epithelial-mesenchymal transition effect of silibinin in tumors.
Overall, silibinin treatment of TRAMP mice bearing prostate tumor inhibited tumor growth, progression, local invasion, and distant metastasis involving suppression of tumor angiogenesis and epithelial-mesenchymal transition. These findings would have greater relevance for the ongoing phase II clinical trial with silibinin-phytosome in prostate cancer patients.
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"Lahat and collaborator suggested that the withaferin-A induces vimentin degradation in a panel of soft tissue sarcoma xenograft experiments, leading to the inhibition of growth, local recurrence, and metastasis . In prostate tumors, both silibinin and flavonolignan inhibited invasion, motility, and migration of the cancer cells via downregulation of vimentin in cancer cell lines and mice models  . Finally, salinomycin, an antibiotic, reduced significantly vimentin level and induced increase in E-cadherin expression in CD133 + colorectal cancer cell lines HT29 and SW480 resulting in decreased malignant traits . "
[Show abstract][Hide abstract] ABSTRACT: Tumor growth and metastatic dissemination rely on cellular plasticity. Among the different phenotypes acquired by cancer cells, epithelial to mesenchymal transition (EMT) has been extensively illustrated. Indeed, this transition allows an epithelial polarized cell to acquire a more mesenchymal phenotype with increased mobility and invasiveness. The role of EMT is quite clear during developmental stage. In the neoplastic context in many tumors EMT has been associated with a more aggressive tumor phenotype including local invasion and distant metastasis. EMT allows the cell to invade surrounding tissues and survive in the general circulation and through a stem cell phenotype grown in the host organ. The molecular pathways underlying EMT have also been clearly defined and their description is beyond the scope of this review. Here we will summarize and analyze the attempts made to block EMT in the therapeutic context. Indeed, till today, most of the studies are made in animal models. Few clinical trials are ongoing with no obvious benefits of EMT inhibitors yet. We point out the limitations of EMT targeting such tumor heterogeneity or the dynamics of EMT during disease progression.
Full-text · Article · Oct 2015 · Journal of Oncology
"e l s e v i e r . c o m / l o c a t e / y b b r c VEGFR and nuclear factor-kappa B (NF-jB)  . Therefore, by targeting IR activated pro-survival pathways, silibinin may prove to be effective in countering undesirable attributes of IR in these cells and hence improve radio-therapeutic response. "
[Show abstract][Hide abstract] ABSTRACT: Radiotherapy of is well established and frequently utilized in prostate cancer (PCa) patients. However, recurrence following therapy and distant metastases are commonly encountered problems. Previous studies underline that, in addition to its therapeutic effects, ionizing radiation (IR) increases the vascularity and invasiveness of surviving radioresistant cancer cells. This invasive phenotype of radioresistant cells is an upshot of IR-induced pro-survival and mitogenic signaling in cancer as well as endothelial cells. Here, we demonstrate that a plant flavonoid, silibinin can radiosensitize endothelial cells by inhibiting expression of pro-angiogenic factors. Combining silibinin with IR not only strongly down-regulated endothelial cell proliferation, clonogenicity and tube formation ability rather it strongly (p < 0.001) reduced migratory and invasive properties of PCa cells which were otherwise marginally affected by IR treatment alone. Most of the pro-angiogenic (VEGF, iNOS), migratory (MMP-2) and EMT promoting proteins (uPA, vimentin, N-cadherin) were up-regulated by IR in PCa cells. Interestingly, all of these invasive and EMT promoting actions of IR were markedly decreased by silibinin. Further, we found that potentiated effect was an end result of attenuation of IR-activated mitogenic and pro-survival signaling, including Akt, Erk1/2 and STAT-3, by silibinin.
Full-text · Article · Nov 2014 · Biochemical and Biophysical Research Communications
"Therefore, pharmacologic inhibition of EMT may be instrumental in cancer prevention and treatment. Some flavonoids such as paeoniflorin, proanthocyanidin and silibinin have been reported to reverse EMT (Prasad & Katiyar, 2012; Singh et al., 2008; Zeng et al., 2013 "