Therapeutic value of orally administered silibinin in renal cell carcinoma: manipulation of insulin-like growth factor binding protein-3 levels

Updates on the Pivotal Roles of Mitochondria in Urothelial Carcinoma

Mitochondria are important organelles responsible for energy production, redox homeostasis, oncogenic signaling, cell death, and apoptosis. Deregulated mitochondrial metabolism and biogenesis are often observed during cancer development and progression. Reports have described the crucial roles of mitochondria in urothelial carcinoma (UC), which is a major global health challenge. This review focuses on research advances in the role of mitochondria in UC. Here, we discuss the pathogenic roles of mitochondria in UC and update the mitochondria-targeted therapies. We aim to offer a better understanding of the mitochondria-modulated pathogenesis of UC and hope that this review will allow the development of novel mitochondria-targeted therapies.

Role of Active Components of Medicinal Food in the Regulation of Angiogenesis

Angiogenesis refers to the formation of new blood vessels from the endothelial cells of existing arteries, veins, and capillaries. Angiogenesis is involved in a variety of physiological and pathological processes, such as the formation of malignant and development of atherosclerosis and other diseases. In recent years, many studies have shown that the active components of food have a certain regulatory effect on angiogenesis and negligible clinical limitations. With the increasing attention being paid to medicine and food homology, exploring the effect of active food components on angiogenesis is of great significance. In this review, we discuss the source, composition, pharmacological activity, and mechanism of action of certain active components of medicinal foods in detail. These could help prevent angiogenesis-related complications or provide a basis for healthier dietary habits. This review can provide a theoretical basis for the research and development of highly efficient anti-angiogenic drugs with low toxicity.

Targeting the pH Paradigm at the Bedside: A Practical Approach

The inversion of the pH gradient in malignant tumors, known as the pH paradigm, is increasingly becoming accepted by the scientific community as a hallmark of cancer. Accumulated evidence shows that this is not simply a metabolic consequence of a dysregulated behavior, but rather an essential process in the physiopathology of accelerated proliferation and invasion. From the over-simplification of increased lactate production as the cause of the paradigm, as initially proposed, basic science researchers have arrived at highly complex and far-reaching knowledge, that substantially modified that initial belief. These new developments show that the paradigm entails a different regulation of membrane transporters, electrolyte exchangers, cellular and membrane enzymes, water trafficking, specialized membrane structures, transcription factors, and metabolic changes that go far beyond fermentative glycolysis. This complex world of dysregulations is still shuttered behind the walls of experimental laboratories and has not yet reached bedside medicine. However, there are many known pharmaceuticals and nutraceuticals that are capable of targeting the pH paradigm. Most of these products are well known, have low toxicity, and are also inexpensive. They need to be repurposed, and this would entail shorter clinical studies and enormous cost savings if we compare them with the time and expense required for the development of a new molecule. Will targeting the pH paradigm solve the "cancer problem"? Absolutely not. However, reversing the pH inversion would strongly enhance standard treatments, rendering them more efficient, and in some cases permitting lower doses of toxic drugs. This article's goal is to describe how to reverse the pH gradient inversion with existing drugs and nutraceuticals that can easily be used in bedside medicine, without adding toxicity to established treatments. It also aims at increasing awareness among practicing physicians that targeting the pH paradigm would be able to improve the results of standard therapies. Some clinical cases will be presented as well, showing how the pH gradient inversion can be treated at the bedside in a simple manner with repurposed drugs.

Silibinin induces apoptosis through inhibition of the mTOR-GLI1-BCL2 pathway in renal cell carcinoma

The downstream transcriptional factor of the hedgehog (Hh) pathway, GLI family zinc finger 1 (GLI1), plays a crucial role in regulating tumor progression. In the present study, we demonstrated that silibinin, a natural flavonoid antioxidant isolated from extracts of the milk thistle herb, exerts its anticancer capabilities by restraining GLI1 function in renal cell carcinoma (RCC) cells in vitro and in vivo. In the present study, we confirmed that silibinin induced growth inhibition of RCC through caspase-dependent apoptosis and downregulation of GLI1 and BCL2, which could be partially reversed by GLI1 overexpression. Moreover, we determined that the decreased GLI1 expression by silibinin was mediated by the mammalian target of rapamycin (mTOR) pathway. The in vivo mouse xenograft study also showed that silibinin significantly reduced RCC tumor growth and specifically targeted the mTOR-GLI1-BCL2 signaling pathway. In conclusion, our findings demonstrated for the first time that silibinin induces apoptosis of RCC cells through inhibition of the mTOR-GLI1‑BCL2 pathway. These findings also indicate that GLI1 is a novel regulator for the potential therapeutic application of silibinin against RCC.

Oxaliplatin-induced oxidative stress in nervous system-derived cellular models: could it correlate with in vivo neuropathy?

Oxaliplatin is a platinum-organic drug with antineoplastic properties used for colorectal cancer. With respect to the other platinum derivates oxaliplatin induces only a mild hematological and gastrointestinal toxicity. Its limiting side effect is its neurotoxicity, which results in a sensory neuropathy. Repeated oxaliplatin treatment in the rat led to a neuropathic pain characterized by a significant oxidative damage throughout the nervous system. The natural antioxidants silibinin and α-tocopherol reduce redox alteration and prevent pain. Starting from the "oxidative hypothesis" as a molecular basis of chemotherapy-induced neurotoxicity, we decided to explore deep inside the mechanisms of oxaliplatin neurotoxicity and search for a cellular system useful for screening antioxidant compounds that can reduce oxaliplatin neurotoxicity. Focusing on various constituents of the central nervous system, we used the neuronal-derived cell line SH-SY5Y and primary cultures of rat cortical astrocytes. Oxaliplatin significantly increased superoxide anion production and induced lipid peroxidation (malonyldialdehyde levels) and protein (carbonylated proteins) and DNA oxidation (8-OH-dG levels). Silibinin and α-tocopherol (10µM) were able to reduce the oxidative damage in both cell types. These antioxidants fully protected astrocytes from the caspase 3 apoptotic signaling activation induced by oxaliplatin. The damage prevention effects of silibinin and α-tocopherol on nervous system-derived cells did not interfere with the oxaliplatin antineoplastic in vitro mechanism as evaluated on a human colon adenocarcinoma cell line (HT29). Moreover, neither silibinin nor α-tocopherol modified the oxaliplatin-induced apoptosis in HT29 cells, suggesting a different antiapoptotic profile in normal vs tumoral cells for these antioxidant compounds. In conclusion, because data obtained in in vitro cellular models parallel the in vivo study we propose cell models to investigate oxaliplatin neurotoxicity and to screen possible therapeutic adjuvant agents.

Silibinin induced the apoptosis of Hep-2 cells via oxidative stress and down-regulating survivin expression

Silibinin is an anticancer and chemopreventive natural compound, which is extracted from milk thistle (Silybum marianum). It is reported that silibinin has anticancer efficacy in many malignant tumors. Laryngeal carcinoma is the second most common head and neck squamous carcinoma. In the present work, we investigated the effects of silibinin on laryngeal squamous cell carcinoma (LSCC) cell line Hep-2 cells. We found that silibinin induced the decrease of cell viability in Hep-2 cells with a concentration- and time-dependent manner. Moreover, silibinin resulted in the apoptosis of Hep-2 cells and had synergy effects with arsenic trioxide. Intracellular reactive oxygen species (ROS) accumulation increased because of silibinin exposure. ROS scavenger NAC alleviated the cytotoxicity of silibinin to Hep-2 cells. The mitochondrial membrane potential (MMP) was lost in Hep-2 cells treated with silibinin. Subsequently, silibinin induced the activation of caspase-3 in Hep-2 cells and caspase inhibitor Z-VAD-FMK inhibited the cytotoxicity of silibinin in Hep-2 cells. The survivin expression decreased after Hep-2 cells were treated with silibinin. In conclusion, silibinin induced the apoptosis of Hep-2 cells via oxidative stress and down-regulating survivin expression. Therefore, silibinin is a potential therapeutical agent against LSCC in future.

Molecular mechanisms of silibinin-mediated cancer chemoprevention with major emphasis on prostate cancer

Despite advances in early detection, prostate cancer remains the second highest cancer mortality in American men, and even successful interventions are associated with enormous health care costs as well as prolonged deleterious effects on quality of patient life. Prostate cancer chemoprevention is one potential avenue to alleviate these burdens. It is a regime whereby long-term treatments are intended to prevent or arrest cancer development, in contrast to more direct intervention upon disease diagnosis. Based on this intention, cancer chemoprevention generally focuses on the use of nontoxic chemical agents which are well-tolerated for prolonged usage that is necessary to address prostate cancer's multistage and lengthy period of progression. One such nontoxic natural agent is the flavonoid silibinin, derived from the milk thistle plant (Silybum marianum), which has ancient medicinal usage and potent antioxidant activity. Based on these properties, silibinin has been investigated in a host of cancer models where it exhibits broad-spectrum efficacy against cancer progression both in vitro and in vivo without noticeable toxicity. Specifically in prostate cancer models, silibinin has shown the ability to modulate cell signaling, proliferation, apoptosis, epithelial to mesenchymal transition, invasion, metastasis, and angiogenesis, which taken together provides strong support for silibinin as a candidate prostate cancer chemopreventive agent.

Antimetastatic efficacy of silibinin: molecular mechanisms and therapeutic potential against cancer

Cancer is a major health problem around the world. Research efforts in the last few decades have been successful in providing better and effective treatments against both early stage and localized cancer, but clinical options against advanced metastatic stage/s of cancer remain limited. The high morbidity and mortality in most of the cancers are attributed to their metastatic spread to distant organs. Due to its extreme clinical relevance, metastasis has been extensively studied and is now understood as a highly complex biological event that involves multiple steps including acquisition of invasiveness by cancer cells, intravasation into circulatory system, survival in the circulation, arrest in microvasculature, extravasation, and growth at distant organs. The increasing understanding of molecular underpinnings of these events has provided excellent opportunity to target metastasis especially through nontoxic and biologically effective nutraceuticals. Silibinin, a popular dietary supplement isolated from milk thistle seed extracts, is one such natural agent that has shown biological efficacy through pleiotropic mechanisms against a variety of cancers and is currently in clinical trials. Recent preclinical studies have also shown strong efficacy of silibinin to target cancer cell's migratory and invasive characteristics as well as their ability to metastasize to distant organs. Detailed mechanistic analyses revealed that silibinin targets signaling molecules involved in the regulation of epithelial-to-mesenchymal transition, proteases activation, adhesion, motility, invasiveness as well as the supportive tumor-microenvironment components, thereby inhibiting metastasis. Overall, the long history of human use, remarkable nontoxicity, and preclinical efficacy strongly favor the clinical use of silibinin against advanced metastatic cancers.

A study of high-dose oral silybin-phytosome followed by prostatectomy in patients with localized prostate cancer

BACKGROUND

Silibinin is a polyphenolic flavonolignan derived from milk thistle (Silybum marianium) with anti-oxidant properties. The purpose of the current trial was to determine the tissue and blood effects of high-dose silybin-phytosome in prostate cancer patients.

METHODS

Subjects with localized prostate cancer planning for a prostatectomy were eligible to enroll. Six patients received 13 g of silybin-phytosome daily with six additional participants serving as control subjects.

RESULTS

Patients in the treatment arm received silybin-phytosome for 14-31 days (mean was 20 days) prior to surgery. Silibinin blood levels were measured 1 hr after the first silybin-phytosome dose with a mean value of 19.7 microM. Trough silibinin levels were assessed at the end of the trial with an average concentration of 1.2 microM. In contrast to the high peak levels of silibinin observed in blood, the highest silibinin level observed in the harvested prostate tissue was 496.6 pmol/g. There were no significant differences noted in baseline and post-treatment blood levels of IGF-I and IGFBP-3. One of the treated patients developed a grade 4 post-operative thromboembolic event. The other observed toxicities in the treatment group were mild: four subjects had diarrhea and one had asymptomatic grade 2 hyperbilirubinemia which was transient.

CONCLUSIONS

High-dose oral silybin-phytosome achieves high blood concentrations transiently, but low levels of silibinin are seen in prostate tissue. Silibinin's lack of tissue penetration may be explained by its short half-life, the brief duration of therapy in this study or an active process removing silibinin from the prostate.

Targeting silibinin in the antiproliferative pathway

IMPORTANCE OF THE FIELD

Due to the failure and severe toxicity of cancer chemotherapy, silibinin, a natural flavonoid from the seeds of milk thistle, has recently received more attention for its potential anticancer and nontoxic roles in animals and humans. Silibinin has clearly demonstrated inhibition of multiple cancer cell signaling pathways, including growth inhibition, inhibition of angiogenesis, chemosensitization, and inhibition of invasion and metastasis. Cumulative evidence implicates that silibinin is a potential agent for cancer chemoprevention and chemotherapy.

AREAS COVERED IN THIS REVIEW

Our aim is to discuss the recent progress of silibinin in regulating multiple anticancer proliferative signaling pathways; the review covers literature mainly from the past 3 - 5 years.

WHAT THE READER WILL GAIN

One of the strategies for tumor therapy is eradication of cancer cells through targeting specific cell-proliferative pathways. This review highlights the current knowledge of silibinin in regulating multiple cellular proliferative pathways in cancer cells, including receptor tyrosine kinases, androgen receptor, STATs, NF-kappaB, cell cycle regulatory and apoptotic signaling pathways.

TAKE HOME MESSAGE

The molecular mechanisms of silibinin-mediated antiproliferative effects are mainly via receptor tyrosine kinases, androgen receptor, STATs, NF-kappaB, cell cycle regulatory and apoptotic signaling pathways in various cancer cells. Targeting inhibition of proliferative pathways through silibinin treatment may provide a new approach for improving chemopreventive and chemotherapeutic effects.

Inhibition of nuclear factor kappa B attenuates tumour progression in an animal model of renal cell carcinoma

BACKGROUND

Renal cell carcinoma (RCC) is a highly metastatic and lethal disease with few efficacious treatments. Many studies have shown that the ubiquitous transcription factor nuclear factor kappa B (NF-kappaB) plays a key role in the development and progression of many cancers including RCC. The aim of this investigation was to evaluate the anti-cancer effect of pyrrolidine dithiocarbamate (PDTC), a NF-kappaB inhibitor, in a murine xenograft model of RCC.

METHODS

The metastatic human RCC cell line, SN12K1, was inoculated into the left kidneys of severe combined immunodeficiency mice and the effect of semi-continuous PDTC treatment (50 mg/kg) on RCC growth analysed 5 weeks later. The analyses carried out in three groups (no treatment, RCC alone and RCC + PDTC) at 5 weeks were: renal weight, protein expression by immunohistochemistry and Western immunoblot, apoptosis (TdT-mediated nick end labelling and morphology) and mitosis (morphology).

RESULTS

PDTC significantly decreased RCC growth and the expression of NF-kappaB subunits (p50, p52, c-Rel and RelB), upstream IKK-beta and IKK-gamma, but did not induce any changes in the expression of IkappaB-alpha and IkappaB-beta. RCC growth was associated with a significant decrease in the expression of the anti-apoptotic proteins Bcl-2 and Bcl-(XL) and increase in pro-apoptotic Bax, all of which were reversed by PDTC. Cell proliferation was significantly reduced by PDTC.

CONCLUSION

The results demonstrate the potential anti-cancer benefits of treating NF-kappaB positive RCCs with NF-kappaB inhibitors like PDTC.

Silibinin suppresses growth and induces apoptotic death of human colorectal carcinoma LoVo cells in culture and tumor xenograft

Colorectal cancer is one of the leading causes of cancer-related morbidity and mortality. The use of nontoxic phytochemicals in the prevention and intervention of colorectal cancer has been suggested as an alternative to chemotherapy. Here we assessed the anticancer efficacy of silibinin against advanced colorectal cancer LoVo cells both in vitro and in vivo. Our results showed that silibinin treatment strongly inhibits the growth of LoVo cells (P < 0.05-0.001) and induces apoptotic death (P < 0.01-0.001), which was associated with increased levels of cleaved caspases (3 and 9) and cleaved poly(ADP-ribose) polymerase. Additionally, silibinin caused a strong cell cycle arrest at G(1) phase and a slight but significant G(2)-M-phase arrest at highest concentration (P < 0.01-0.001). Molecular analyses for cell cycle regulators showed that silibinin decreases the level of cyclins (D1, D3, A and B1) and cyclin-dependent kinases (1, 2, 4, and 6) and increases the level of cyclin-dependent kinase inhibitors (p21 and p27). Consistent with these results, silibinin treatment also decreased the phosphorylation of retinoblastoma protein at Ser(780), Ser(795), and Ser(807)/Ser(811) sites without significantly affecting its total level. In animal studies, oral administration of silibinin for 6 weeks (at 100 and 200 mg/kg/d for 5 days/wk) significantly inhibited the growth of LoVo xenograft (P < 0.001) in athymic nude mice without any apparent toxicity. Analyses of xenograft tissue showed that silibinin treatment inhibits proliferation and increases apoptosis along with a strong increase in p27 levels but a decrease in retinoblastoma phosphorylation. Together, these results suggest the potential use of silibinin against advanced human colorectal cancer.

Dietary supplementation of silymarin protects against chemically induced nephrotoxicity, inflammation and renal tumor promotion response

Ferric nitrilotriacetate (Fe-NTA) is a potent nephrotoxicant and a renal carcinogen that induces its effect by causing oxidative stress. The present study was undertaken to explore protective effect of silymarin, a flavonolignan from milk thistle (Silybum marianum), against Fe-NTA mediated renal oxidative stress, inflammation and tumor promotion response along with elucidation of the implicated mechanism(s). Administration of Fe-NTA (10 mg/kg bd wt, i.p.) to Swiss albino mice induced marked oxidative stress in kidney, evident from augmentation in renal metallothionein (MT) expression, depletion of glutathione content and activities of antioxidant and phase II metabolizing enzymes, and enhancement in production of aldehyde products such as 4-hydroxy-2-nonenal. Fe-NTA also significantly activated nuclear factor kappa B (NFkappaB) and upregulated the expression of downstream genes: cyclooxygenase 2 and inducible nitric oxide synthase and enhancing the production of proinflammatory cytokines: tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6). However, feeding of 0.5% and 1% silymarin diet conferred a significant protection against Fe-NTA induced oxidative stress and inflammation. It further augmented MT expression, restored the antioxidant armory, ameliorated NFkappaB activation and decreased the expression of proinflammatory mediators. Silymarin also suppressed Fe-NTA induced hyperproliferation in kidney, ameliorating renal ornithine decarboxylase activity and DNA synthesis. From these results, it could be concluded that silymarin markedly protects against chemically induced renal cancer and acts plausibly by virtue of its antioxidant, anti-inflammatory and antiproliferative activities.

Multitargeted therapy of cancer by silymarin

Silymarin, a flavonolignan from milk thistle (Silybum marianum) plant, is used for the protection against various liver conditions in both clinical settings and experimental models. In this review, we summarize the recent investigations and mechanistic studies regarding possible molecular targets of silymarin for cancer prevention. Number of studies has established the cancer chemopreventive role of silymarin in both in vivo and in vitro models. Silymarin modulates imbalance between cell survival and apoptosis through interference with the expressions of cell cycle regulators and proteins involved in apoptosis. In addition, silymarin also showed anti-inflammatory as well as anti-metastatic activity. Further, the protective effects of silymarin and its major active constituent, silibinin, studied in various tissues, suggest a clinical application in cancer patients as an adjunct to established therapies, to prevent or reduce chemotherapy as well as radiotherapy-induced toxicity. This review focuses on the chemistry and analogues of silymarin, multiple possible molecular mechanisms, in vitro as well as in vivo anti-cancer activities, and studies on human clinical trials.