Therapeutic potential of curcumin in prostate cancer--V: Interference with the osteomimetic properties of hormone refractory C4-2B prostate cancer cells

Targeting the prostate tumor microenvironment by plant-derived natural products

Prostate cancer is among the most common malignancies for men, with limited therapy options for last stages of the tumor. There are some different options for treatment and control of prostate tumor growth. However, targeting some specific molecules and cells within tumors has been attracted interests in recent years. The tumor microenvironment (TME) has an important role in the initiation of various malignancies, which can also expand the progression of tumor and facilitate invasion of malignant cells. By regulating immune responses and distinct changes in the metabolism of cells in the tumor, TME has substantial effects in the resistance of cancer cells to therapy. TME in various solid cancers like prostate cancer includes various cells, including cancer cells, supportive stromal cells, immunosuppressive cells, and anticancer inflammatory cells. Natural products including herbal-derived agents and also other natural compounds have been well studied for their anti-tumor potentials. These compounds may modulate various signaling pathways involved in TME, such as immune responses, the metabolism of cells, epigenetics, angiogenesis, and extracellular matrix (ECM). This paper provides a review of the current knowledge of prostate TME and complex interactions in this environment. Additionally, the potential use of natural products and also nanoparticles loaded with natural products as therapeutic adjuvants on different cells and therapeutic targets within prostate TME will be discussed.

Effects of curcumin and ursolic acid in prostate cancer: A systematic review

The major barriers to phytonutrients in prostate cancer therapy are non-specific mechanisms and bioavailability issues. Studies have pointed to a synergistic combination of curcumin (CURC) and ursolic acid (UA). We investigate this combination using a systematic review process to assess the most likely mechanistic pathway and human testing in prostate cancer. We used the PRISMA statement to screen titles, abstracts, and the full texts of relevant articles and performed a descriptive analysis of the literature reviewed for study inclusion and consensus of the manuscript. The most common molecular and cellular pathway from articles reporting on the pathways and effects of CURC (n = 173) in prostate cancer was NF-κB (n = 25, 14.5%). The most common molecular and cellular pathway from articles reporting on the pathways and effects of UA (n = 24) in prostate cancer was caspase 3/caspase 9 (n = 10, 41.6%). The three most common molecular and cellular pathway from articles reporting on the pathways and effects of both CURC and UA (n = 193) in prostate cancer was NF-κB (n = 28, 14.2%), Akt (n = 22, 11.2%), and androgen (n = 19, 9.6%). Therefore, we have identified the potential synergistic target pathways of curcumin and ursolic acid to involve NF-κB, Akt, androgen receptors, and apoptosis pathways. Our review highlights the limited human studies and specific effects in prostate cancer.

Curcumin Upregulates miR-148a to Increase the Chemosensitivity of CD44-Positive Prostate Cancer Stem Cells to Paclitaxel Through Targeting the MSK1/IRS1 axis

BACKGROUND

In men, prostate cancer (PC) is the second most common cause of cancer-related death. However, paclitaxel resistance is a major challenge in advanced PC. Curcumin, a natural antioxidant, has been demonstrated to have cytotoxic effects on cancer stem cells (CSCs). The goal of this study is to explore if curcumin can help lower chemoresistance to paclitaxel through the regulation of miR-148a-mediated apoptosis in prostate CSCs.

METHODS

The 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay and 4',6-diamidino-2-phenylindole (DAPi) labeling were used to determine cell survival. Immunohistochemistry was used to detect the expression of P-glycoprotein protein (P-gp) and CD44 proteins. Finally, real-time PCR was used to evaluate the regulatory effects of curcumin and paclitaxel on miR-148a and its target genes.

RESULTS

Curcumin and paclitaxel co-treatment significantly reduced the IC₅₀ value in CD44⁺cells compared to paclitaxel alone. Additionally, combining these drugs considerably increased apoptosis in CD44⁺cells. We also discovered that when curcumin and paclitaxel were combined, the expression of CD44 and P-gp was significantly reduced compared to paclitaxel alone. Curcumin and paclitaxel co-treatment also increased miR-148a levels and regulated the levels of its target genes MSK1 and IRS1.

CONCLUSION

Curcumin may restore paclitaxel sensitivity by raising miR-148a expression and inhibiting its target genes.

Pharmacological Mechanisms and Clinical Applications of Curcumin: Update

Curcumin, a well-known hydrophobic polyphenol extracted from the rhizomes of turmeric (Curcuma longa L.), has attracted great interest in the last ten years due to its multiple pharmacological activities. A growing body of evidence has manifested that curcumin has extensive pharmacological activities including anti-inflammatory, anti-oxygenation, lipid regulation, antiviral, and anticancer with hypotoxicity and minor adverse reactions. However, the disadvantages of low bioavailability, short half-life in plasma, low drug concentration in blood, and poor oral absorption severely limited the clinical application of curcumin. Pharmaceutical researchers have carried out plenty of dosage form transformations to improve the druggability of curcumin and have achieved remarkable results. Therefore, the objective of this review summarizes the pharmacological research progress, problems in clinical application and the improvement methods of curcumin's druggability. By reviewing the latest research progress of curcumin, we believe that curcumin has a broad clinical application prospect for its wide range of pharmacological activities with few side effects. The deficiencies of lower bioavailability of curcumin could be improved by dosage form transformation. However, curcumin in the clinical application still requires further study regarding the underlying mechanism and clinical trial verification.

Exploring the Biological Activity and Mechanism of Xenoestrogens and Phytoestrogens in Cancers: Emerging Methods and Concepts

Xenoestrogens and phytoestrogens are referred to as "foreign estrogens" that are produced outside of the human body and have been shown to exert estrogen-like activity. Xenoestrogens are synthetic industrial chemicals, whereas phytoestrogens are chemicals present in the plant. Considering that these environmental estrogen mimics potentially promote hormone-related cancers, an understanding of how they interact with estrogenic pathways in human cells is crucial to resolve their possible impacts in cancer. Here, we conducted an extensive literature evaluation on the origins of these chemicals, emerging research techniques, updated molecular mechanisms, and ongoing clinical studies of estrogen mimics in human cancers. In this review, we describe new applications of patient-derived xenograft (PDX) models and single-cell RNA sequencing (scRNA-seq) techniques in shaping the current knowledge. At the molecular and cellular levels, we provide comprehensive and up-to-date insights into the mechanism of xenoestrogens and phytoestrogens in modulating the hallmarks of cancer. At the systemic level, we bring the emerging concept of window of susceptibility (WOS) into focus. WOS is the critical timing during the female lifespan that includes the prenatal, pubertal, pregnancy, and menopausal transition periods, during which the mammary glands are more sensitive to environmental exposures. Lastly, we reviewed 18 clinical trials on the application of phytoestrogens in the prevention or treatment of different cancers, conducted from 2002 to the present, and provide evidence-based perspectives on the clinical applications of phytoestrogens in cancers. Further research with carefully thought-through concepts and advanced methods on environmental estrogens will help to improve understanding for the identification of environmental influences, as well as provide novel mechanisms to guide the development of prevention and therapeutic approaches for human cancers.

Curcumin against Prostate Cancer: Current Evidence

Cancer is a condition characterized by remarkably enhanced rates of cell proliferation paired with evasion of cell death. These deregulated cellular processes take place following genetic mutations leading to the activation of oncogenes, the loss of tumor suppressor genes, and the disruption of key signaling pathways that control and promote homeostasis. Plant extracts and plant-derived compounds have historically been utilized as medicinal remedies in different cultures due to their anti-inflammatory, antioxidant, and antimicrobial properties. Many chemotherapeutic agents used in the treatment of cancer are derived from plants, and the scientific interest in discovering plant-derived chemicals with anticancer potential continues today. Curcumin, a turmeric-derived polyphenol, has been reported to possess antiproliferative and proapoptotic properties. In the present review, we summarize all the in vitro and in vivo studies examining the effects of curcumin in prostate cancer.

Formulation of More Efficacious Curcumin Delivery Systems Using Colloid Science: Enhanced Solubility, Stability, and Bioavailability

Curcumin is a bioactive constituent isolated from turmeric that has historically been used as a seasoning, pigment, and herbal medicine in food. Recently, it has become one of the most commonly studied nutraceuticals in the pharmaceutical, supplement, and food areas because of its myriad of potential health benefits. For instance, it is claimed to exhibit antioxidant, anti-inflammatory, antimicrobial, antiparasite, and anticancer activities when ingested as a drug, supplement, or food. Toxicity studies suggest that it is safe to consume, even at relatively high levels. Its broad-spectrum biological activities and low toxicity have meant that it has been widely explored as a nutraceutical ingredient for application in functional foods. However, there are several hurdles that formulators must overcome when incorporating curcumin into commercial products, such as its low water solubility (especially under acidic and neutral conditions), chemical instability (especially under neutral and alkaline conditions), rapid metabolism by enzymes in the human body, and limited bioavailability. As a result, only a small fraction of ingested curcumin is actually absorbed into the bloodstream. These hurdles can be at least partially overcome by using encapsulation technologies, which involve trapping the curcumin within small particles. Some of the most commonly used edible microparticles or nanoparticles utilized for this purpose are micelles, liposomes, emulsions, solid lipid particles, and biopolymer particles. Each of these encapsulation technologies has its own benefits and limitations for particular product applications and it is important to select the most appropriate one.

High Levels of Glutaminase II Pathway Enzymes in Normal and Cancerous Prostate Suggest a Role in 'Glutamine Addiction'

Abstract: Many tumors readily convert l-glutamine to α-ketoglutarate. This conversion is almost invariably described as involving deamidation of l-glutamine to l-glutamate followed by a transaminase (or dehydrogenase) reaction. However, mammalian tissues possess another pathway for conversion of l-glutamine to α-ketoglutarate, namely the glutaminase II pathway: l-Glutamine is transaminated to α-ketoglutaramate, which is then deamidated to α-ketoglutarate by ω-amidase. Here we show that glutamine transaminase and ω-amidase specific activities are high in normal rat prostate. Immunohistochemical analyses revealed that glutamine transaminase K (GTK) and ω-amidase are present in normal and cancerous human prostate and that expression of these enzymes increases in parallel with aggressiveness of the cancer cells. Our findings suggest that the glutaminase II pathway is important in providing anaplerotic carbon to the tricarboxylic acid (TCA) cycle, closing the methionine salvage pathway, and in the provision of citrate carbon in normal and cancerous prostate. Finally, our data also suggest that selective inhibitors of GTK and/or ω-amidase may be clinically important for treatment of prostate cancer. In conclusion, the demonstration of a prominent glutaminase II pathway in prostate cancer cells and increased expression of the pathway with increasing aggressiveness of tumor cells provides a new perspective on 'glutamine addiction' in cancers.

3D porous chitosan-alginate scaffold stiffness promotes differential responses in prostate cancer cell lines

Prostate cancer (PCa) is a leading cause of death for men worldwide. Most PCa patients die from metastasis and bone is the most common metastatic site. Three dimensional (3D) porous chitosan-alginate (CA) scaffolds were developed for bone tissue engineering and demonstrated for culture of cancer cells and enrichment of cancer stem cells. However, only a single scaffold composition was studied. Three compositions of 3D porous CA scaffolds (2, 4, and 6 wt%) were used to investigate the effect of scaffold stiffness on PCa cell response with PC-3, C4-2B, and 22Rv1 cell lines. The PC-3 cells formed cell clusters while the C4-2B and 22Rv1 cells formed multicellular spheroids. The three cell lines demonstrated stiffness independent cell growth and expressed phenotypic PCa biomarkers. The osteoblastic PCa lines C4-2B and 22Rv1 mineralized in basal media, while the osteolytic PC-3 line did not, demonstrating that CA scaffold cultures revealed differences in PCa phenotypes. The CA scaffolds are a 3D culture platform that supports PCa growth and phenotypic expression with adjustable scaffold stiffness to mimic stages of metastatic progression. Further investigation of the scaffolds for co-culture of PCa cells with fibroblasts and primary PCa cell culture should be conducted to develop a platform for screening chemotherapies.

Low-dose curcuminoid-loaded in dextran nanobubbles can prevent metastatic spreading in prostate cancer cells

Preventing recurrences and metastasis of prostate cancer after prostatectomy by administering adjuvant therapies is quite a controversial issue. In addition to effectiveness, absence of side effects and long term toxicity are mandatory. Curcuminoids (Curc) extracted with innovative techniques and effectively loaded by polymeric nanobubbles (Curc-NBs) satisfy such requirements. Curc-NBs showed stable over 30 d, were effectively internalized by tumor cells and were able to slowly release Curc in a sustained way. Significant biological effects were detected in PC-3 and DU-145 cell lines where Curc-NBs were able to inhibit adhesion and migration, to promote cell apoptosis and to affect cell viability and colony-forming capacity in a dose-dependent manner. Since the favourable effects are already detectable at very low doses, which can be reached at a clinical level, the actual drug concentration can be visualized and monitored by US or MRI, Curc-NBs can be proposed as an effective adjuvant theranostic tool.

Prostate Cancer Disparity, Chemoprevention, and Treatment by Specific Medicinal Plants

Prostate cancer (PC) is one of the most common cancers in men. The global burden of this disease is rising. Its incidence and mortality rates are higher in African American (AA) men compared to white men and other ethnic groups. The treatment decisions for PC are based exclusively on histological architecture, prostate-specific antigen (PSA) levels, and local disease state. Despite advances in screening for and early detection of PC, a large percentage of men continue to be diagnosed with metastatic disease including about 20% of men affected with a high mortality rate within the African American population. As such, this population group may benefit from edible natural products that are safe with a low cost. Hence, the central goal of this article is to highlight PC disparity associated with nutritional factors and highlight chemo-preventive agents from medicinal plants that are more likely to reduce PC. To reach this central goal, we searched the PubMed Central database and the Google Scholar website for relevant papers. Our search results revealed that there are significant improvements in PC statistics among white men and other ethnic groups. However, its mortality rate remains significantly high among AA men. In addition, there are limited studies that have addressed the benefits of medicinal plants as chemo-preventive agents for PC treatment, especially among AA men. This review paper addresses this knowledge gap by discussing PC disparity associated with nutritional factors and highlighting the biomedical significance of three medicinal plants (curcumin, garlic, and Vernonia amygdalina) that show a great potential to prevent/treat PC, as well as to reduce its incidence/prevalence and mortality, improve survival rate, and reduce PC-related health disparity.

NRH:quinone oxidoreductase 2 (NQO2) and glutaminase (GLS) both play a role in large extracellular vesicles (LEV) formation in preclinical LNCaP-C4-2B prostate cancer model of progressive metastasis

In the course of studies aimed at the role of oxidative stress in the development of metastatic potential in the LNCaP-C4-2B prostate cancer progression model system, we found a relative decrease in the level of expression of the cytoplasmic nicotinamide riboside: quinone oxidoreductase (NQO2) and an increase in the oxidative stress in C4-2B cells compared to that in LNCaP or its derivatives C4 and C4-2. It was also found that C4-2B cells specifically shed large extracellular vesicles (LEVs) suggesting that these LEVs and their cargo could participate in the establishment of the osseous metastases. The level of expression of caveolin-1 increased as the system progresses from LNCaP to C4-2B. Since NQO2 RNA levels were not changed in LNCaP, C4, C4-2, and C4-2B, we tested an altered cellular distribution hypothesis of NQO2 being compartmentalized in the membrane fractions of C4-2B cells which are rich in lipid rafts and caveolae. This was confirmed when the detergent resistant membrane fractions were probed on immunoblots. Moreover, when the LEVs were analyzed for membrane associated caveolin-1 as possible cargo, we noticed that the enzyme NQO2 was also a component of the cargo along with caveolin-1 as seen in double immunofluorescence studies. Molecular modeling studies showed that a caveolin-1 accessible site is present in NQO2. Specific interaction between NQO2 and caveolin-1 was confirmed using deletion constructs of caveolin-1 fused with glutathione S-transferase (GST). Interestingly, whole cell lysate and mitochondrial preparations of LNCaP, C4, C4-2, and C4-2B showed an increasing expression of glutaminase (GLS, kidney type). The extrusion of LEVs appears to be a specific property of the bone metastatic C4-2B cells and this process could be inhibited by a GLS specific inhibitor BPTES, suggesting the critical role of a functioning glutamine metabolism. Our results indicate that a high level of expression of caveolin-1 in C4-2B cells contributes to an interaction between caveolin-1 and NQO2 and to their packaging as cargo in the shed LEVs. These results suggest an important role of membrane associated oxidoreductases in the establishment of osseous metastases in prostate cancer.

Role of Curcumin in Common Musculoskeletal Disorders: a Review of Current Laboratory, Translational, and Clinical Data

The Indian spice turmeric, in which the active and dominant biomolecule is curcumin, has been demonstrated to have significant medicinal properties, including anti-inflammatory and anti-neoplastic effects. This promise is potentially very applicable to musculoskeletal disorders, which are common causes of physician visits worldwide. Research at the laboratory, translational and clinical levels that supports the use of curcumin for various musculoskeletal disorders, such as osteoarthritis, osteoporosis, musculocartilaginous disorders, and sarcoma is here in comprehensively summarized. Though more phase I-III trials are clearly needed, thus far the existing data show that curcumin can indeed potentially be useful in treatment of the hundreds of millions worldwide who are afflicted by these musculoskeletal disorders.

Molecular mechanisms of curcumin and its semisynthetic analogues in prostate cancer prevention and treatment

Primary prostate cancer, also known as prostate adenocarcinoma (PCa), is a devastating cancer in men worldwide. Europe and developing countries of Asia have fewer reported cases of prostate cancer compared to increasing cases in the United States with higher incidence in Black men. Risk factors associated with prostate cancer are aging, genetics, lifestyle, high body mass index as well as carcinogenic exposure to carbon-containing fuels, tobacco, and charbroiled meats. Hormone therapy and radical prostatectomy are commonly implemented treatments. The >20.000 prostate cancer deaths of 2013 suggest that there exists a need for enhanced chemopreventive and therapeutic agents for prostate cancer treatment. Fruits, vegetables, and red wines contain high levels of polyphenolic levels. Consumption of these products may provide chemoprevetion of PCa. Curcumin, the major compound from the turmeric rhizome Curcuma longa has long been used for medicinal purposes as an antiseptic and wound healing. This review focuses on curcumin's therapeutic effectiveness in vitro and in vivo in prostate cancer models. The review will highlight the mechanisms of actions of curcumin in the signaling pathways of prostate cancer.

Therapeutic actions of curcumin in bone disorders

Curcumin is the active component of turmeric extract derived from the Curcuma longa plant. In the last decade, curcumin has raised a considerable interest in medicine owing to its negligible toxicity and multiple therapeutic actions including anti-cancer, anti-inflammatory and anti-microbial activities. Among the various molecular targets of curcumin, some are involved in bone remodeling, which strongly suggests that curcumin can affect the skeletal system. The review sheds light on the current and potential applications of curcumin to treat bone disorders characterized by an excessive resorption activity. Within the scope of this review, the novel formulations of curcumin to overcome its physico-chemical and pharmacokinetic constraints are also discussed.

Curcumin Inhibits Prostate Cancer Bone Metastasis by Up-Regulating Bone Morphogenic Protein-7 in Vivo

A number of studies have focused on the beneficial properties of Curcumin (diferuloyl methane, used in South Asian cuisine and traditional medicine) such as the chemoprevention of cancer. Recent studies have also indicated that this material has significant benefits for the treatment of cancer and is currently undergoing several clinical trials. We have been interested in the application of this compound as a therapeutic agent for advanced prostate cancer, particularly the skeletal complications in this malignancy. Our earlier work indicated that this compound could inhibit the osteomimetic properties which occur in castration resistant prostate cancer cells, by interfering with the common denominators between these cancer cells and the bone cells in the metastatic tumor microenvironment, namely the osteoblasts and the osteoclast. We predicted that curcumin could break the vicious cycle of reciprocal stimulation that results in uncontrolled osteolysis in the bony matrix. In this work, we have evaluated the potential of this compound in inhibiting the bone metastasis of hormone refractory prostate cancer cells in an established animal model. Our results strongly suggest that curcumin modulates the TGF-β signaling that occurs due to bone matrix degradation by up-regulating the metastasis inhibitory bone morphogenic protein-7 (BMP- 7). This enhancement of BMP-7 in the context of TGF-βin the tumor microenvironment is shown to enhance the mesenchymal-to-epithelial transition. Most importantly, we show that as a result of BMP-7 up-regulation, a novel brown/beige adipogenic differentiation program is also up-regu- lated which plays a role in the inhibition of bone metastasis. Our results suggest that curcumin may subvert the TGF-βsignaling to an alternative adipogenic differentiation program in addition to the previously established interference with the osteomimetic properties, thus inhibiting the bone metastatic processes in a chemopreventive as well as therapeutic setting.

Characterization of synergistic anti-cancer effects of docosahexaenoic acid and curcumin on DMBA-induced mammary tumorigenesis in mice

BACKGROUND

The major obstacles to the successful use of individual nutritional compounds as preventive or therapeutic agents are their efficacy and bioavailability. One approach to overcoming this problem is to use combinations of nutrients to induce synergistic effects. The objective of this research was to investigate the synergistic effects of two dietary components: docosahexaenoic acid (DHA), an omega-3 fatty acid present in cold-water fish, and curcumin (CCM), an herbal nutrient present in turmeric, in an in vivo model of DMBA-induced mammary tumorigenesis in mice.

METHODS

We used the carcinogen DMBA to induce breast tumors in SENCAR mice on control, CCM, DHA, or DHA + CCM diets. Appearance and tumor progression were monitored daily. The tumors were harvested 15 days following their first appearance for morphological and immunohistological analysis. Western analysis was performed to determine expression of maspin and survivin in the tumor tissues. Characterization of tumor growth was analyzed using appropriate statistical methods. Otherwise all other results are reported as mean ± SD and analyzed with one-way ANOVA and Tukey's post hoc procedure.

RESULTS

Analysis of gene microarray data indicates that combined treatment with DHA + CCM altered the profile of "PAM50" genes in the SK-BR-3 cell line from an ER⁻/Her-2⁺ to that resembling a "normal-like" phenotype. The in vivo studies demonstrated that DHA + CCM treatment reduced the incidence of breast tumors, delayed tumor initiation, and reduced progression of tumor growth. Dietary treatment had no effect on breast size development, but tumors from mice on a control diet (untreated) were less differentiated than tumors from mice fed CCM or DHA + CCM diets. The synergistic effects also led to increased expression of the pro-apoptotic protein, maspin, but reduced expression of the anti-apoptotic protein, survivin.

CONCLUSIONS

The SK-BR-3 cells and DMBA-induced tumors, both with an ER⁻ and Her-2⁺ phenotype, were affected by the synergistic interaction of DHA and CCM. This suggests that the specific breast cancer phenotype is an important factor for predicting efficacy of these nutraceuticals. The combination of DHA and CCM is potentially a dietary supplemental treatment for some breast cancers, likely dependent upon the molecular phenotype of the cancer.

Superior anticancer efficacy of curcumin-loaded nanoparticles against lung cancer

Curcumin (CM) has anticancer potential for several cancers and blocks several steps in the carcinogenesis process. However, the clinical application of CM is greatly limited due to its low effects in vivo resulted from its poor solubility and pharmacokinetics. This raises the possibility of taking CM as a novel model drug in a new nanoparticle-based delivery system. In this study, CM-loaded nanoparticles were prepared from three kinds of amphilic methoxy poly(ethylene glycol) (mPEG)-polycaprolactone (PCL) block copolymers. It was noted that CM-loaded nanoparticles prepared from mPEG10k-PCL30k showed not only the highest loading efficiency, but also the most sustained release pattern. In vitro studies showed that CM was effectively transported into A549 cells by nanoparticles and localized around the nuclei in the cytoplasm. In addition, the cytotoxicity of CM-loaded nanoparticles with mEPG10k-PCL30k as a drug carrier was in a dose- and time-dependent manner in A549 cells. Further apoptotic staining results demonstrated the superior pro-apoptotic effect of CM-loaded nanoparticles over free drug. Data in this study not only confirmed the potential of CM in treating lung cancer, but also offered an effective way to improve the anticancer efficiency of CM through the nano-drug delivery system.

Curcumin reorganizes miRNA expression in a mouse model of liver fibrosis

Curcumin (CM), a biphenyl compound, possesses anti-inflammatory, antioxidant and antimicrobial activity. MicroRNAs (miRNAs) are small noncoding RNAs which regulate gene expression and the molecular mechanisms of several biological processes. Liver fibrosis is a major cause of hepatic dysfunction and cancer and there are few effective therapies emphasizing the need for new approaches to control. The present study was conducted to investigate the effect of curcumin (CM) on liver fibrosis through modulating the expression level of miRNAs (199 and 200), the main miRNAs associated with liver fibrosis. Induction of liver fibrosis by carbon tetrachloride (CCL4) was confirmed by histopathological examination. Mice were divided into 3 groups: group 1 were i.p injected with 10% CCL4 twice weekly for 4 weeks and then once a week for the next 4 weeks followed by 4 weeks with olive oil only. Group 2 were i.p injected with 10% CCL4 twice weekly for 4 weeks and then once a week for the next 4 weeks followed by curcumin (5 mg/mouse/day) once daily for the next 4 weeks. The third group was injected with olive oil. The expression level of miR-199 and miR-200 and some of their targeted genes were measured by real time PCR. miRNA (199 and 200) levels were significantly elevated in liver fibrotic tissues compared to control groups. Curcumin was significantly returned the expression levels of mir-199 and -200 with their associated target gene nearly to their normal levels. This is the first study that highlighted the effect of curcumin on liver fibrosis through regulation of miRNAs.

Curcumin effect on MMPs and TIMPs genes in a breast cancer cell line

Curcumin (CM) possesses anti-cancer activity against a variety of tumors. Matrix metalloproteinases (MMPs) play an important role in remodeling the extracellular matrix and their activities are regulated by tissue inhibitor of metalloproteinases (TIMPs) family. Control of MMP and TIMP activity are now of great significance. In this study, the effect of CM is investigated on metastatic MMPs and anti-metastatic TIMPs genes on MDA breast cancer cells cultured in a mixture of DMEM and Ham's F12 medium and treated with different concentrations of CM (10, 20 and 40 μM for various lengths of time. Reverse transcription followed by quantitative real time PCR was used to detect the gene expression levels of MMPs and TIMPs in CM-treated versus untreated cases and the data were analyzed by one-way ANOVA. At high concentrations of curcumin, TIMP-1, -2, -3 and -4 genes were up-regulated after 48 hours of treatment, their over-expression being accompanied by down-regulation of MMP-2 and MMP-9 gene expression levels in a concentration- and time-dependent manner. These results suggest that curcumin plays a role in regulating cell metastasis by inhibiting MMP-2 and MMP-9 and up-regulating TIMP1 and TIMP4 gene expression in breast cancer cells.

Recreating the tumor microenvironment in a bilayer, hyaluronic acid hydrogel construct for the growth of prostate cancer spheroids

Cancer cells cultured in physiologically relevant, three-dimensional (3D) matrices can recapture many essential features of native tumor tissues. In this study, a hyaluronic acid (HA)-based bilayer hydrogel system that not only supports the tumoroid formation from LNCaP prostate cancer (PCa) cells, but also simulates their reciprocal interactions with the tumor-associated stroma was developed and characterized. HA hydrogels were prepared by mixing solutions of HA precursors functionalized with acrylate groups (HA-AC) and reactive thiols (HA-SH) under physiological conditions. The resultant viscoelastic gels have an average elastic modulus of 234 ± 30 Pa and can be degraded readily by hyaluronidase. The orthogonal and cytocompatible nature of the crosslinking chemistry permits facile incorporation of cytokine-releasing particles and PCa cells. In our bilayer hydrogel construct, the top layer contains heparin (HP)-decorated, HA-based hydrogel particles (HGPs) capable of releasing heparin-binding epidermal growth factor-like growth factor (HB-EGF) in a sustained manner at a rate of 2.5 wt%/day cumulatively. LNCaP cells embedded in the bottom layer receive the growth factor signals from the top, and in response form enlarging tumoroids with an average diameter of 85 μm by day 7. Cells in 3D hydrogels assemble into spherical tumoroids, form close cellular contacts through E-cadherin, and show cortical organization of F-actin, whereas those plated as 2D monolayers adopt a spread-out morphology. Compared to cells cultured on 2D, the engineered tumoroids significantly increased the expression of two pro-angiogenic factors, vascular endothelial growth factor-165 (VEGF(165)) and interleukin-8 (IL-8), both at mRNA and protein levels. Overall, the HA model system provides a useful platform for the study of tumor cell responses to growth factors and for screening of anticancer drugs targeting these pathways.

Chemoprevention of prostate cancer: soy isoflavones and curcumin

The burden of increasing morbidity and mortality due to prostate cancer imposes a need for new, effective measures of prevention in daily life. The influence of lifestyle on carcinogenesis in Asian men who migrate to Western cultures supports a causal role for dietary, environmental, and genetic factors in the epidemiology of prostate cancer. Chemoprevention, a prophylactic approach that uses nontoxic natural or synthetic compounds to reverse, inhibit, or prevent cancer by targeting specific steps in the carcinogenic pathway, is gaining traction among health care practitioners. Soy isoflavones and curcumin, staples of the Asian diet, have shown promise as functional factors for the chemoprevention of prostate cancer because of their ability to modulate multiple intracellular signaling pathways, including cellular proliferation, apoptosis, inflammation, and androgen receptor signaling. Recent evidence has revealed the DNA damage response (DDR) to be one of the earliest events in the multistep progression of human epithelial carcinomas to invasive malignancy. Soy isoflavones and curcumin activate the DDR, providing an opportunity and rationale for the clinical application of these nutraceuticals in the chemoprevention of prostate cancer.

A synergistic antiproliferation effect of curcumin and docosahexaenoic acid in SK-BR-3 breast cancer cells: unique signaling not explained by the effects of either compound alone

Background

Breast cancer is a collection of diseases in which molecular phenotypes can act as both indicators and mediators of therapeutic strategy. Therefore, candidate therapeutics must be assessed in the context of multiple cell lines with known molecular phenotypes. Docosahexaenoic acid (DHA) and curcumin (CCM) are dietary compounds known to antagonize breast cancer cell proliferation. We report that these compounds in combination exert a variable antiproliferative effect across multiple breast cell lines, which is synergistic in SK-BR-3 cells and triggers cell signaling events not predicted by the activity of either compound alone.

Methods

Dose response curves for CCM and DHA were generated for five breast cell lines. Effects of the DHA+ CCM combination on cell proliferation were evaluated using varying concentrations, at a fixed ratio, of CCM and DHA based on their individual ED₅₀. Detection of synergy was performed using nonlinear regression of a sigmoid dose response model and Combination Index approaches. Cell molecular network responses were investigated through whole genome microarray analysis of transcript level changes. Gene expression results were validated by RT-PCR, and western blot analysis was performed for potential signaling mediators. Cellular curcumin uptake, with and without DHA, was analyzed via flow cytometry and HPLC.

Results

CCM+DHA had an antiproliferative effect in SK-BR-3, MDA-MB-231, MDA-MB-361, MCF7 and MCF10AT cells. The effect was synergistic for SK-BR-3 (ER^- PR^- Her2⁺) relative to the two compounds individually. A whole genome microarray approach was used to investigate changes in gene expression for the synergistic effects of CCM+DHA in SK-BR-3 cells lines. CCM+DHA triggered transcript-level responses, in disease-relevant functional categories, that were largely non-overlapping with changes caused by CCM or DHA individually. Genes involved in cell cycle arrest, apoptosis, inhibition of metastasis, and cell adhesion were upregulated, whereas genes involved in cancer development and progression, metastasis, and cell cycle progression were downregulated. Cellular pools of PPARγ and phospho-p53 were increased by CCM+DHA relative to either compound alone. DHA enhanced cellular uptake of CCM in SK-BR-3 cells without significantly enhancing CCM uptake in other cell lines.

Conclusions

The combination of DHA and CCM is potentially a dietary supplemental treatment for some breast cancers, likely dependent upon molecular phenotype. DHA enhancement of cellular curcumin uptake is one potential mechanism for observed synergy in SK-BR-3 cells; however, transcriptomic data show that the antiproliferation synergy accompanies many signaling events unique to the combined presence of the two compounds.

Protein kinase C: an attractive target for cancer therapy

Apoptosis plays an important role during all stages of carcinogenesis and the development of chemoresistance in tumor cells may be due to their selective defects in the intracellular signaling proteins, central to apoptotic pathways. Consequently, many studies have focused on rendering the chemotherapy more effective in order to prevent chemoresistance and pre-clinical and clinical data has suggested that protein kinase C (PKC) may represent an attractive target for cancer therapy. Therefore, a complete understanding of how PKC regulates apoptosis and chemoresistance may lead to obtaining a PKC-based therapy that is able to reduce drug dosages and to prevent the development of chemoresistance.

Curcumin inhibits cellular condensation and alters microfilament organization during chondrogenic differentiation of limb bud mesenchymal cells

Curcumin is a well known natural polyphenol product isolated from the rhizome of the plant Curcuma longa, anti-inflammatory agent for arthritis by inhibiting synthesis of inflammatory prostaglandins. However, the mechanisms by which curcumin regulates the functions of chondroprogenitor, such as proliferation, precartilage condensation, cytoskeletal organization or overall chondrogenic behavior, are largely unknown. In the present report, we investigated the effects and signaling mechanism of curcumin on the regulation of chondrogenesis. Treating chick limb bud mesenchymal cells with curcumin suppressed chondrogenesis by stimulating apoptotic cell death. It also inhibited reorganization of the actin cytoskeleton into a cortical pattern concomitant with rounding of chondrogenic competent cells and down-regulation of integrin beta1 and focal adhesion kinase (FAK) phosphorylation. Curcumin suppressed the phosphorylation of Akt leading to Akt inactivation. Activation of Akt by introducing a myristoylated, constitutively active form of Akt reversed the inhibitory actions of curcumin during chondrogenesis. In summary, for the first time, we describe biological properties of curcumin during chondrogenic differentiation of chick limb bud mesenchymal cells. Curcumin suppressed chondrogenesis by stimulating apoptotic cell death and down-regulating integrin-mediated reorganization of actin cytoskeleton via modulation of Akt signaling.

Chemopreventive potential of curcumin in prostate cancer

The long latency and high incidence of prostate carcinogenesis provides the opportunity to intervene with chemoprevention in order to prevent or eradicate prostate malignancies. We present here an overview of the chemopreventive potential of curcumin (diferuloylmethane), a well-known natural compound that exhibits therapeutic promise for prostate cancer. In fact, it interferes with prostate cancer proliferation and metastasis development through the down-regulation of androgen receptor and epidermal growth factor receptor, but also through the induction of cell cycle arrest. It regulates the inflammatory response through the inhibition of pro-inflammatory mediators and the NF-kappaB signaling pathway. These results are consistent with this compound's ability to up-induce pro-apoptotic proteins and to down-regulate the anti-apoptotic counterparts. Alone or in combination with TRAIL-mediated immunotherapy or radiotherapy, curcumin is also reported to be a good inducer of prostate cancer cell death by apoptosis. Curcumin appears thus as a non-toxic alternative for prostate cancer prevention, treatment or co-treatment.

[A critical assessment of phytotherapy for prostate cancer]

Prostate cancer patients increasingly use complementary and alternative medicines to support the body's immune system in addition to conventional treatment to minimize morbidity associated with conventional treatment, to enhance the quality of life, and ultimately in the hope to cure cancer when conventional treatment fails. As there is a large variety of phytomedicines promoted as potential treatment for prostate cancer, the aim of this review was to differentiate between preventive and therapeutic approaches and evaluate which phytochemicals might be suited for therapy of prostate cancer. Therefore, preclinical in vitro and in vivo data as well as clinical trials with phytosubstances such as genistein, lycopene, epigallocatechin gallate, resveratrol, and mistletoe were assessed. The presented data show that at present there is no clinical evidence that phytochemicals might have a therapeutic use in prostate cancer in relation to reduction of tumor progression or improved survival. The question about an improved immune function or quality of life remains open. Potentially the use of phytochemicals could play a role in a preventive setting.

Penta-O-galloyl-beta-D-glucose suppresses prostate cancer bone metastasis by transcriptionally repressing EGF-induced MMP-9 expression

Prostate carcinoma is the most frequently diagnosed malignancy and the second leading cause of cancer-related death of men in the United States. Epidermal growth factor (EGF) generated from bone tissue contributes to prostate cancer metastasis through stimulating matrix metalloproteinase (MMP) secretions from prostate cancer cells. In this study, in vitro invasion assay was performed by incubating penta-O-galloyl-beta-D-glucose (5GG) at various concentrations with 2 x 10(4) PC-3 cells for 48 h. The anti-invasive and cytotoxic effects of 5GG were found and evaluated on the human androgen-independent prostate cancer PC-3 cell line by MTT assays and Western blot analyses. 5GG inhibited the EGF-induced cell invasiveness and MMP-9 expression in a dose- and time-dependent manner by reducing the MMP-9 transcriptional activity. To explore the mechanisms for the 5GG-mediated regulation of MMP-9, we further examined the effects of 5GG on transcription factors, including NF-kappaB, AP-1, and mitogen-activated protein kinase (MAPK) activities. The results showed that 5GG suppressed the EGF-induced NF-kappaB nuclear translocation and also abrogated the EGF-induced activation of c-jun N-terminal kinase (JNK), an upstream modulator of NF-kappaB. Moreover, we showed that 5GG reduced EGFR expression through the proteasome pathway. These results suggest that 5GG may exert at least part of its anti-invasive effect in androgen-independent prostate cancer by controlling MMP-9 expression through the suppression of the EGFR/JNK pathway. Finally, 5GG suppresses invasion and tumorigenesis in nude mice treatment with intratibia injection of PC-3 cells. These in vitro and in vivo results suggest that 5GG may be a therapeutic candidate for the treatment of advanced prostate cancer.

Curcuminoid-phospholipid complex induces apoptosis in mammary epithelial cells by STAT-3 signaling

Curcumin (from the rhizome of Curcuma longa) is well documented for its medicinal properties in Indian and Chinese systems of medicine where it is widely used for the treatment of several diseases. Epidemiological observations are suggestive that curcumin consumption may reduce the risk of some form of cancers and provide other protective biological effects in humans. These biological properties have been attributed to curcuminoids that have been widely studied for their anti-inflammatory, anti-angiogenic, antioxidant, wound healing and anti-cancer effects. In this study we have investigated on the effect of a curcumin phospholipid complex on mammary epithelial cell viability. HC11 and BME-UV cell lines, validated models to study biology of normal, not tumoral, mammary epithelial cells, were used to analyse these effects. We report that curcumin acts on STAT-3 signal pathway to reduce cell viability and increase apoptosis evaluated by the the amount of activated caspase 3. Further it reduces MAPK and AKT activations. JSI-124, a STAT-3 inhibitor (100 nM) was able to block the negative effect of curcumin on cell viability and caspase 3 activation. Finally the negative effect of cucumin on cell viability has been impaired in STAT-3i HC11, where STAT-3 protein was greatly reduced by shRNA-interference. These results indicate that curcumin presents a potential adverse effect to normal mammary epithelial cells and that it has a specific effect on signal trasduction in mammary epithelium.

Anticancer and carcinogenic properties of curcumin: considerations for its clinical development as a cancer chemopreventive and chemotherapeutic agent

A growing body of research suggests that curcumin, the major active constituent of the dietary spice turmeric, has potential for the prevention and therapy of cancer. Preclinical data have shown that curcumin can both inhibit the formation of tumors in animal models of carcinogenesis and act on a variety of molecular targets involved in cancer development. In vitro studies have demonstrated that curcumin is an efficient inducer of apoptosis and some degree of selectivity for cancer cells has been observed. Clinical trials have revealed that curcumin is well tolerated and may produce antitumor effects in people with precancerous lesions or who are at a high risk for developing cancer. This seems to indicate that curcumin is a pharmacologically safe agent that may be used in cancer chemoprevention and therapy. Both in vitro and in vivo studies have shown, however, that curcumin may produce toxic and carcinogenic effects under specific conditions. Curcumin may also alter the effectiveness of radiotherapy and chemotherapy. This review article analyzes the in vitro and in vivo cancer-related activities of curcumin and discusses that they are linked to its known antioxidant and pro-oxidant properties. Several considerations that may help develop curcumin as an anticancer agent are also discussed.

TWIST modulates prostate cancer cell-mediated bone cell activity and is upregulated by osteogenic induction

TWIST, a helix-loop-helix transcription factor, is highly expressed in many types of human cancer. We have previously found that TWIST confers prostate cancer cells with an enhanced metastatic potential through promoting epithelial-mesenchymal transition (EMT) and a high TWIST expression in human prostate cancer is associated with an increased metastatic potential. The predilection of prostate cancer cells to metastasize to bone may be due to two interplaying mechanisms (i) by increasing the rate of bone remodeling and (ii) by undergoing osteomimicry. We further studied the role of TWIST in promoting prostate cancer to bone metastasis. TWIST expression in PC3, a metastatic prostate cancer cell line, was silenced by small interfering RNA and we found that conditioned medium from PC3 with lower TWIST expression had a lower activity on stimulating osteoclast differentiation and higher activity on stimulating osteoblast mineralization. In addition, we found that these effects were, at least partly, associated with TWIST-induced expression of dickkopf homolog 1 (DKK-1), a factor that promotes osteolytic metastasis. We also examined TWIST and RUNX2 expressions during osteogenic induction of an organ-confined prostate cancer cell, 22Rv1. We observed increased TWIST and RUNX2 expressions upon osteogenic induction and downregulation of TWIST through short hairpin RNA reduced the induction level of RUNX2. In summary, our results suggest that, in addition to EMT, TWIST may also promote prostate cancer to bone metastasis by modulating prostate cancer cell-mediated bone remodeling via regulating the expression of a secretory factor, DKK-1, and enhancing osteomimicry of prostate cancer cells, probably, via RUNX2.

Serum level of macrophage colony-stimulating factor is increased in prostate cancer patients with bone metastasis

Recent evaluation of human prostate tissues has shown predominantly high expression of the macrophage colony-stimulating factor receptor in prostatic intra-epithelial neoplasia or prostate cancer. However, the expression of its ligand, the macrophage colony-stimulating factor (M-CSF), and the biological role of this signaling in prostate cancer has not been analyzed. In this research we determined the relationship of serum M-CSF level to clinical parameters of prostate cancer progression. We measured the serum level of M-CSF in 170 patients with histologically confirmed prostatic adenocarcinoma and in 54 patients in whom prostate cancer was not detected. We also investigated the M-CSF expression in prostate cancer tissues by immunohistochemistry. The serum levels of M-CSF in bone metastatic prostate cancer patients was significantly higher than those in non-metastatic patients, while M-CSF did not differ with regards to histological grade, Gleason score or local tumor progression. M-CSF expression was detected in prostate cancer cells themselves by immunohistochemistry. These results suggest that M-CSF may have a functional role in prostate cancer progression.

CURCUMIN: THE INDIAN SOLID GOLD

Turmeric, derived from the plant Curcuma longa, is a gold-colored spice commonly used in the Indian subcontinent, not only for health care but also for the preservation of food and as a yellow dye for textiles. Curcumin, which gives the yellow color to turmeric, was first isolated almost two centuries ago, and its structure as diferuloylmethane was determined in 1910. Since the time of Ayurveda (1900 Bc) numerous therapeutic activities have been assigned to turmeric for a wide variety of diseases and conditions, including those of the skin, pulmonary, and gastrointestinal systems, aches, pains, wounds, sprains, and liver disorders. Extensive research within the last half century has proven that most of these activities, once associated with turmeric, are due to curcumin. Curcumin has been shown to exhibit antioxidant, anti-inflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer's disease, and other chronic illnesses. These effects are mediated through the regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other enzymes. Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal "Spice for Life".

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.

Cytotoxic effects induced by a combination of cyclopamine and gefitinib, the selective hedgehog and epidermal growth factor receptor signaling inhibitors, in prostate cancer cells

Although the blockade of the hedgehog cascade by using cyclopamine has been reported to inhibit the growth of some cancer cell types, few studies on the mechanism by which this drug alone or in combination with other cytotoxic agents induces its cytotoxic effect have been reported. In our study, we evaluate, for the first time, the antiproliferative and cytotoxic effects induced by a combination of selective SMO inhibitor, cyclopamine and epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, gefitinib on metastatic prostate cancer (PC) cells. The results revealed that cyclopamine, alone or at a lower concentration in combination with gefitinib, inhibited the growth of sonic hedgehog- (SHH), epidermal growth factor- (EGF) and serum-stimulated androgen-sensitive LNCaP-C33 and LNCaP-LN3 and androgen-independent LNCaP-C81, DU145 and PC3 cells. The antiproliferative effect of cyclopamine and gefitinib, alone or in combination, was mediated via a blockade of the PC3 cells in the G1 phase of the cell cycle. Importantly, the combined cyclopamine and gefitinib also caused a higher rate of apoptotic death of PC cells compared to single agents. The cytotoxic effect induced by these drugs in PC3 cells appears to be mediated at least, in part, via the mitochondrial pathway through the depolarization of the mitochondrial membrane and the release of cytochrome c and reactive oxygen species into the cytosol. This was also accompanied by the activation of caspase cascades, PARP cleavage and DNA fragmentation. Additionally, the combined cyclopamine and gefitinib were more effective at suppressing the invasiveness of PC3 cells through matrigel in vitro as the drugs alone. These findings indicate that the simultaneous blockade of SHH-GLI-1 and EGF-EGFR signaling, which results in the growth arrest and massive rate of apoptotic cell death, represents a promising strategy for a more effective treatment of metastatic PC forms.

The effects of curcumin on the invasiveness of prostate cancer in vitro and in vivo

Curcumin has become a focus of interest with regard to its antitumor effects in prostate cancer; however, the effects of this agent on invasion and metastasis remain less well understood. Matrix metalloproteinases (MMPs) are important prerequisite for tumor invasion and metastasis. In this study, we evaluated the effects of curcumin on prostate cancer cells (DU-145) invasion in both in vitro and in vivo. We utilized zymography and ELISA in order to determine the MMP-2 and MMP-9 activity. Matrigel invasion assay was performed to assess cellular invasion. We developed a xenograft model to examine tumorigenicity. Curcumin treatment resulted not only in a significant reduction in the expression of MMP-2 and MMP-9, but also effected the inhibition of invasive ability in vitro. Curcumin was shown to induce a marked reduction of tumor volume, MMP-2, and MMP-9 activity in the tumor-bearing site. The metastatic nodules in vivo were significantly fewer in the curcumin-treated group than untreated group. Curcumin appears to constitute a potential agent for the prevention of cancer progression, or at least of the initial phase of metastasis, in prostate cancer.

Inhibition of EGFR signaling in human prostate cancer PC-3 cells by combination treatment with β-phenylethyl isothiocyanate and curcumin

Many naturally occurring compounds, including beta-phenylethyl isothiocyanate (PEITC) and curcumin, exhibit significant anti-cancer chemopreventive effects. In this study, we investigated the combined effects of PEITC and curcumin in PC-3 human prostate cancer cells and in PC-3 cells that were stably transfected with an NF-kappaB luciferase plasmid (PC-3 C4). We found an additive effect of PEITC and curcumin for the induction of apoptosis. To elucidate the potential mechanisms of this effect, we studied several critical cellular signaling pathways, including the critical NF-kappaB cell survival signal that is hyper-activated in PC-3 cells and many other cancers. PEITC and curcumin additively inhibited NF-kappaB luciferase activity. Furthermore, the combined treatment significantly increased the activity of poly(ADP-Ribose) polymerase and cleavage of caspase-3 in correlation with apoptotic cell death. Studying upstream signaling events, we found that the phosphorylations of IkappaBalpha and Akt (Ser473, Thr308) were significantly attenuated by the combination of PEITC and curcumin. As these events can be downstream of the activation of epidermal growth factor receptor (EGFR), we pretreated PC-3 cells with PEITC and curcumin and then stimulated them with EGF. EGFR phosphorylations (Y845 and Y1068) were dramatically suppressed by PEITC or curcumin, and more so by the combination. Importantly, the degree of Akt and PI3K phosphorylations induced by EGF were also significantly suppressed. We conclude that the simultaneous targeting of EGFR, Akt and NF-kappaB signaling pathways by PEITC and curcumin could be the molecular targets by which PEITC and curcumin exert their additive inhibitory effects on cell proliferation and ultimately lead to programmed cell death of tumor cells.

Therapeutic targets for antimetastatic therapy

Metastases are responsible for most cancer deaths. Despite dramatic advances in cancer therapy, the presence of metastases implies a significantly shortened survival and reduced quality of remaining life. Aside from prevention of cancer altogether, or significant improvements in early detection for most cancers, effective novel therapeutic strategies targeting metastasis should provide the greatest clinical benefit. Metastasis research has shown that many of the initial steps in metastasis are completed with a high degree of efficiency and may have occurred by the time of clinical diagnosis. Therefore, targeting the later stages of metastasis may offer a more promising therapeutic approach for the development of antimetastatic therapies. Appropriate clinical strategies include targeting dormant solitary cells, active preangiogenic metastases, or vascularised metastases. Dormancy of solitary single cells, seen clinically and experimentally, may be an explanation for cancer recurrence. Eradication or inactivation of these dormant cells could provide large benefit for patients. However, little is known about what makes cancer cells dormant and, therefore, a greater knowledge of the mechanisms of dormancy is needed. This review discusses potential biological targets, as defined by the steps in the metastatic process, for antimetastatic therapies and provides examples of clinical strategies for preventing or treating successful metastasis.