Suppression of microtubule dynamic instability and turnover in MCF7 breast cancer cells by sulforaphane

Reviewing the Prospective Pharmacological Potential of Isothiocyanates in Fight against Female-Specific Cancers

Gynecological cancers are the most commonly diagnosed malignancies in females worldwide. Despite the advancement of diagnostic tools as well as the availability of various therapeutic interventions, the incidence and mortality of female-specific cancers is still a life-threatening issue, prevailing as one of the major health problems worldwide. Lately, alternative medicines have garnered immense attention as a therapeutic intervention against various types of cancers, seemingly because of their safety profiles and enhanced effectiveness. Isothiocyanates (ITCs), specifically sulforaphane, benzyl isothiocyanate, and phenethyl isothiocyanate, have shown an intriguing potential to actively contribute to cancer cell growth inhibition, apoptosis induction, epigenetic alterations, and modulation of autophagy and cancer stem cells in female-specific cancers. Additionally, it has been shown that ITCs plausibly enhance the chemo-sensitization of many chemotherapeutic drugs. To this end, evidence has shown enhanced efficacy in combinatorial regimens with conventional chemotherapeutic drugs and/or other phytochemicals. Reckoning with these, herein, we discuss the advances in the knowledge regarding the aspects highlighting the molecular intricacies of ITCs in female-specific cancers. In addition, we have also argued regarding the potential of ITCs either as solitary treatment or in a combinatorial therapeutic regimen for the prevention and/or treatment of female-specific cancers. Hopefully, this review will open new horizons for consideration of ITCs in therapeutic interventions that would undoubtedly improve the prognosis of the female-specific cancer clientele. Considering all these, it is reasonable to state that a better understanding of these molecular intricacies will plausibly provide a facile opportunity for treating these female-specific cancers.

Benzimidazole and its derivatives as cancer therapeutics: The potential role from traditional to precision medicine

Cancer is the second leading cause of mortality globally which remains a continuing threat to human health today. Drug insensitivity and resistance are critical hurdles in cancer treatment; therefore, the development of new entities targeting malignant cells is considered a high priority. Targeted therapy is the cornerstone of precision medicine. The synthesis of benzimidazole has garnered the attention of medicinal chemists and biologists due to its remarkable medicinal and pharmacological properties. Benzimidazole has a heterocyclic pharmacophore, which is an essential scaffold in drug and pharmaceutical development. Multiple studies have demonstrated the bioactivities of benzimidazole and its derivatives as potential anticancer therapeutics, either through targeting specific molecules or non-gene-specific strategies. This review provides an update on the mechanism of actions of various benzimidazole derivatives and the structure‒activity relationship from conventional anticancer to precision healthcare and from bench to clinics.

Fresh-Cut Eruca Sativa Treated with Plasma Activated Water (PAW): Evaluation of Antioxidant Capacity, Polyphenolic Profile and Redox Status in Caco2 Cells

Plasma Activated Water (PAW) has recently emerged as a promising non-chemical and non-thermal technology for the microbial decontamination of food. However, its use as a replacement for conventional disinfection solutions needs further investigation, as the impact of reactive species generated by PAW on nutritional food quality, toxicology, and safety is still unclear. The purpose of this study is to investigate how treatment with PAW affects the health-promoting properties of fresh-cut rocket salad (Eruca sativa). Therefore, the polyphenolic profile and antioxidant activity were evaluated by a combination of UHPLC-MS/MS and in vitro assays. Moreover, the effects of polyphenolic extracts on cell viability and oxidative status in Caco2 cells were assessed. PAW caused a slight reduction in the radical scavenging activity of the amphiphilic fraction over time but produced a positive effect on the total phenolic content, of about 70% in PAW-20, and an increase in the relative percentage (about 44-50%) of glucosinolate. Interestingly, the PAW polyphenol extract did not cause any cytotoxic effect and caused a lower imbalance in the redox status compared to an untreated sample. The obtained results support the use of PAW technology for fresh-cut vegetables to preserve their nutritional properties.

Herbal Ingredients in the Prevention of Breast Cancer: Comprehensive Review of Potential Molecular Targets and Role of Natural Products

Among various cancers, breast cancer is the most prevalent type in women throughout the world. Breast cancer treatment is challenging due to complex nature of the etiology of disease. Cell division cycle alterations are often encountered in a variety of cancer types including breast cancer. Common treatments include chemotherapy, surgery, radiotherapy, and hormonal therapy; however, adverse effects and multidrug resistance lead to complications and noncompliance. Accordingly, there is an increasing demand for natural products from medicinal plants and foods. This review summarizes molecular mechanisms of signaling pathways in breast cancer and identifies mechanisms by which natural compounds may exert their efficacy in the treatment of breast cancer.

Targeting Drug Chemo-Resistance in Cancer Using Natural Products

Cancer is one of the leading causes of death globally. The development of drug resistance is the main contributor to cancer-related mortality. Cancer cells exploit multiple mechanisms to reduce the therapeutic effects of anticancer drugs, thereby causing chemotherapy failure. Natural products are accessible, inexpensive, and less toxic sources of chemotherapeutic agents. Additionally, they have multiple mechanisms of action to inhibit various targets involved in the development of drug resistance. In this review, we have summarized the basic research and clinical applications of natural products as possible inhibitors for drug resistance in cancer. The molecular targets and the mechanisms of action of each natural product are also explained. Diverse drug resistance biomarkers were sensitive to natural products. P-glycoprotein and breast cancer resistance protein can be targeted by a large number of natural products. On the other hand, protein kinase C and topoisomerases were less sensitive to most of the studied natural products. The studies discussed in this review will provide a solid ground for scientists to explore the possible use of natural products in combination anticancer therapies to overcome drug resistance by targeting multiple drug resistance mechanisms.

Sulforaphane: A Broccoli Bioactive Phytocompound with Cancer Preventive Potential

Simple Summary

As of the past decade, phytochemicals have become a major target of interest in cancer chemopreventive and chemotherapeutic research. Sulforaphane (SFN) is a metabolite of the phytochemical glucoraphanin, which is found in high abundance in cruciferous vegetables, such as broccoli, watercress, Brussels sprouts, and cabbage. In both distant and recent research, SFN has been shown to have a multitude of anticancer effects, increasing the need for a comprehensive review of the literature. In this review, we critically evaluate SFN as an anticancer agent and its mechanisms of action based on an impressive number of in vitro, in vivo, and clinical studies.

Abstract

There is substantial and promising evidence on the health benefits of consuming broccoli and other cruciferous vegetables. The most important compound in broccoli, glucoraphanin, is metabolized to SFN by the thioglucosidase enzyme myrosinase. SFN is the major mediator of the health benefits that have been recognized for broccoli consumption. SFN represents a phytochemical of high interest as it may be useful in preventing the occurrence and/or mitigating the progression of cancer. Although several prior publications provide an excellent overview of the effect of SFN in cancer, these reports represent narrative reviews that focused mainly on SFN’s source, biosynthesis, and mechanisms of action in modulating specific pathways involved in cancer without a comprehensive review of SFN’s role or value for prevention of various human malignancies. This review evaluates the most recent state of knowledge concerning SFN’s efficacy in preventing or reversing a variety of neoplasms. In this work, we have analyzed published reports based on in vitro, in vivo, and clinical studies to determine SFN’s potential as a chemopreventive agent. Furthermore, we have discussed the current limitations and challenges associated with SFN research and suggested future research directions before broccoli-derived products, especially SFN, can be used for human cancer prevention and intervention.

Protective Effect of Isothiocyanates from Cruciferous Vegetables on Breast Cancer: Epidemiological and Preclinical Perspectives

BACKGROUND

The effect of cruciferous vegetable intake on breast cancer survival is controversial at present. Glucosinolates are the naturally occurring constituents found across the cruciferous vegetables. Isothiocyanates are produced from the hydrolysis of glucosinolates and this reaction is catalysed by the plant-derived enzyme myrosinase. The main Isothiocyanates (ITCs) from cruciferous vegetables are sulforaphane, benzyl ITC, and phenethyl ITC, which had been intensively investigated over the last decade for their anti-breast cancer effects.

OBJECTIVE

The aim of this article is to systematically review the evidence from all types of studies, which examined the protective effect of cruciferous vegetables and/or their isothiocyanate constituents on breast cancer.

METHODS

A systematic review was conducted in Pubmed, EMBASE, and the Cochrane Library from inception to 27 April 2020. Peer-reviewed studies of all types (in vitro studies, animal studies, and human studies) were selected.

RESULTS

The systematic literature search identified 16 human studies, 4 animal studies, and 65 in vitro studies. The effect of cruciferous vegetables and/or their ITCs intake on breast cancer survival was found to be controversial and varied greatly across human studies. Most of these trials were observational studies conducted in specific regions, mainly in the US and China. Substantial evidence from in vitro and animal studies was obtained, which strongly supported the protective effect of sulforaphane and other ITCs against breast cancer. Evidence from in vitro studies showed that sulforaphane and other ITCs reduced cancer cell viability and proliferation via multiple mechanisms and pathways. Isothiocyanates inhibited cell cycle, angiogenesis and epithelial mesenchymal transition, as well as induced apoptosis and altered the expression of phase II carcinogen detoxifying enzymes. These are the essential pathways that promote the growth and metastasis of breast cancer. Noticeably, benzyl ITC showed a significant inhibitory effect on breast cancer stem cells, a new dimension of chemo-resistance in breast cancer treatment. Sulforaphane and other ITCs displayed anti-breast cancer effects at variable range of concentrations and benzyl isothiocyanate appeared to have a relatively lower inhibitory concentration IC₅₀. The mechanisms underlying the cancer protective effect of sulforaphane and other ITCs have also been highlighted in this article.

CONCLUSION

Current preclinical evidence strongly supports the role of sulforaphane and other ITCs as potential therapeutic agents for breast cancer, either as adjunct therapy or combined therapy with current anti-breast cancer drugs, with sulforaphane displaying the greatest potential.

Rapha Myr®, a Blend of Sulforaphane and Myrosinase, Exerts Antitumor and Anoikis-Sensitizing Effects on Human Astrocytoma Cells Modulating Sirtuins and DNA Methylation

Brain and other nervous system cancers are the 10th leading cause of death worldwide. Genome instability, cell cycle deregulation, epigenetic mechanisms, cytoarchitecture disassembly, redox homeostasis as well as apoptosis are involved in carcinogenesis. A diet rich in fruits and vegetables is inversely related with the risk of developing cancer. Several studies report that cruciferous vegetables exhibited antiproliferative effects due to the multi-pharmacological functions of their secondary metabolites such as isothiocyanate sulforaphane deriving from the enzymatic hydrolysis of glucosinolates. We treated human astrocytoma 1321N1 cells for 24 h with different concentrations (0.5, 1.25 and 2.5% v/v) of sulforaphane plus active myrosinase (Rapha Myr®) aqueous extract (10 mg/mL). Cell viability, DNA fragmentation, PARP-1 and γH2AX expression were examined to evaluate genotoxic effects of the treatment. Cell cycle progression, p53 and p21 expression, apoptosis, cytoskeleton morphology and cell migration were also investigated. In addition, global DNA methylation, DNMT1 mRNA levels and nuclear/mitochondrial sirtuins were studied as epigenetic biomarkers. Rapha Myr® exhibited low antioxidant capability and exerted antiproliferative and genotoxic effects on 1321N1 cells by blocking the cell cycle, disarranging cytoskeleton structure and focal adhesions, decreasing the integrin α5 expression, renewing anoikis and modulating some important epigenetic pathways independently of the cellular p53 status. In addition, Rapha Myr® suppresses the expression of the oncogenic p53 mutant protein. These findings promote Rapha Myr® as a promising chemotherapeutic agent for integrated cancer therapy of human astrocytoma.

PTPN22 interacts with EB1 to regulate T-cell receptor signaling

The PTPN22 gene encoding the Lyp/Pep protein tyrosine phosphatase is a negative regulator of T-cell receptor (TCR) signaling. Recent studies have shown that phosphorylation of end-binding protein 1 (EB1) is associated with the TCR activation. In this study, using 2-hybrid and mass spectrometry analyses, we identified EB1 as a protein associated with PTPN22. Furthermore, we discovered that EB1 specifically bound to the P1 domain of PTPN22 by competing with CSK, and the variant PTPN22-R620W does not affect the association with EB1, which is instrumental with respect to the regulation of TCR signaling. In addition, PTPN22 dephosphorylates EB1 at tyrosine-247 (Y247), which decreases the expression of the T-cell activation markers CD25 and CD69 and the phosphorylation levels of the TCR molecules ZAP-70, LAT, and Erk, leading to the eventual downregulation of the transcription factor NFAT and reduced the levels of secreted IL-2. The findings of this study provide new insights into the TCR signaling and the T-cell immune response, which are important for clarifying the mechanism of PTPN22-related autoimmune diseases.

Breast Cancer Prevention-Is there a Future for Sulforaphane and Its Analogs?

Breast cancer is the most prevalent type of cancer among women worldwide. There are several recommended methods of breast cancer prevention, including chemoprevention. There are several approved drugs used to prevent breast cancer occurrence or recurrence and metastasizing. There are also a number of new substances undergoing clinical trials and at the stage of initial study. Studies suggest that dietary factors play a crucial role in breast cancer etiology. Epidemiological studies indicate that in particular vegetables from the Brassicaceae family are a rich source of chemopreventive substances, with sulforaphane (SFN) being one of the most widely studied and characterized. This review discusses potential applicability of SFN in breast cancer chemoprevention. A comprehensive review of the literature on the impact of SFN on molecular signalling pathways in breast cancer and breast untransformed cells is presented. The presented results of in vitro and in vivo studies show that this molecule has a potential to act as a preventive molecule either to prevent disease development or recurrence and metastasizing, and as a compound protecting normal cells against the toxic effects of cytostatics. Finally, the still scanty attempts to develop an improved analog are also presented and discussed.

Chemoprevention of Breast Cancer With Vitamins and Micronutrients: A Concise Review

Numerous dietary components and vitamins have been found to inhibit the molecular events and signalling pathways associated with various stages of breast cancer development. To identify the vitamins and dietary micronutrients that exert protective effects against breast cancer and define their mechanism of action, we performed a literature review of in vitro, animal and epidemiological studies and selected the in vitro and animal studies with robust molecular evidence and the epidemiological studies reporting statistically significant inverse associations for a breast cancer-specific protective effect. There is sufficient evidence from in vitro, animal and epidemiological human studies that certain vitamins, such as vitamin D3, folate, vitamin B6, and beta carotene as well as dietary micronutrients, such as curcumin, piperine, sulforaphane, indole-3-carbinol, quercetin, epigallocatechin gallate (EGCG) and omega-3 polyunsaturated fatty acids (PUFAs), display an antitumoral activity against breast cancer and have the potential to offer a natural strategy for breast cancer chemoprevention and reduce the risk of breast cancer recurrence. Therefore, a supplement that contains these micronutrients, using the safest form and dosage should be investigated in future breast cancer chemoprevention studies and as part of standard breast cancer therapy.

The Glucosinolates: A Sulphur Glucoside Family of Mustard Anti-Tumour and Antimicrobial Phytochemicals of Potential Therapeutic Application

This study reviewed aspects of the biology of two members of the glucosinolate family, namely sinigrin and glucoraphanin and their anti-tumour and antimicrobial properties. Sinigrin and glucoraphanin are converted by the β-sulphoglucosidase myrosinase or the gut microbiota into their bioactive forms, allyl isothiocyanate (AITC) and sulphoraphanin (SFN) which constitute part of a sophisticated defence system plants developed over several hundred million years of evolution to protect them from parasitic attack from aphids, ticks, bacteria or nematodes. Delivery of these components from consumption of cruciferous vegetables rich in the glucosinolates also delivers many other members of the glucosinolate family so the dietary AITCs and SFN do not act in isolation. In vitro experiments with purified AITC and SFN have demonstrated their therapeutic utility as antimicrobials against a range of clinically important bacteria and fungi. AITC and SFN are as potent as Vancomycin in the treatment of bacteria listed by the World Health Organisation as antibiotic-resistant “priority pathogens” and also act as anti-cancer agents through the induction of phase II antioxidant enzymes which inactivate potential carcinogens. Glucosinolates may be useful in the treatment of biofilms formed on medical implants and catheters by problematic pathogenic bacteria such as Pseudomonas aeruginosa and Staphylococcus aureus and are potent antimicrobials against a range of clinically important bacteria and fungi. The glucosinolates have also been applied in the prevention of bacterial and fungal spoilage of food products in advanced atmospheric packaging technology which improves the shelf-life of these products.

Transcriptome reveals the gene expression patterns of sulforaphane metabolism in broccoli florets

Sulforaphane is a new and effective anti-cancer component that is abundant in broccoli. In the past few years, the patterns of variability in glucosinolate content and its regulation in A. thaliana have been described in detail. However, the diversity of glucosinolate and sulforaphane contents in different organs during vegetative and reproductive stages has not been clearly explained. In this paper, we firstly investigated the transcriptome profiles of the developing buds and leaves at bolting stage of broccoli (B52) to further assess the gene expression patterns involved in sulforaphane synthesis. The CYP79F1 gene, as well as nine other genes related to glucorahpanin biosynthesis, MAM1, MAM3, St5b-2, FMO GS-OX1, MY, AOP2, AOP3, ESP and ESM1 were selected by digital gene expression analysis and were validated by quantitative real-time PCR (qRT-PCR). Meanwhile, the compositions of glucosinolates and sulforaphane were detected for correlation analysis with related genes. Finally the RNA sequencing libraries generated 147 957 344 clean reads, and 8 539 unigene assemblies were produced. In digital result, only CYP79F1, in the glucoraphanin pathway, was up-regulated in young buds but absent from the other organs, which was consistent with the highest level of sulforaphane content being in this organ compared to mature buds, buds one day before flowering, flowers and leaves. The sequencing results also presented that auxin and cytokinin might affect glucoraphanin accumulation. The study revealed that up-regulated expression of CYP79F1 plays a fundamental and direct role in sulforaphane production in inflorescences. Two genes of MAM1 and St5b-2 could up-regulated glucoraphanin generation. Synergistic expression of MAM1, MAM3, St5b-2, FMO GS-OX1, MY, ESP and ESM1 was found in sulforaphane metabolism. This study will be beneficial for understanding the diversity of sulforaphane in broccoli organs.

Combating breast cancer using combination therapy with 3 phytochemicals: Piperine, sulforaphane, and thymoquinone

Despite the significant advances in screening methods for early diagnosis, breast cancer remains a global threat and continues to be the leading cancer diagnosed in women, requiring effective therapy. Currently, combination therapy has become the hallmark of breast cancer treatment due to the high incidence of tumor recurrence and disease progression after monotherapeutic treatments, including surgery, radiotherapy, endocrine therapy, and chemotherapy. Over the past decades, there has been considerable interest in studying the anticancer effect of bioactive phytochemicals from medicinal plants combined with these conventional therapies. The rationale for this type of therapy is to use combinations of drugs that work by different mechanisms, thereby decreasing the likelihood that cancer cells will develop resistance, and also reduce the therapeutic dose and toxicity of single treatments. Three agents have received great attention with regard to their anticancer properties: 1) piperine, a dietary phytochemical isolated from black pepper (Piper nigrum L.) and long pepper (Piper longum L.); 2) sulforaphane, an isothiocyanate mainly derived from cruciferous vegetables; and 3) thymoquinone, the active compound from black seed (Nigella sativa L.). This review focused on the combined effect of these 3 compounds on conventional cancer therapy with the objective of observing enhanced efficacy compared with single treatments. This review also highlights the importance of the nanoformulation of such bioactive phytochemicals that could enhance their bioavailability by providing an efficient targeted delivery system with a reduced systemic dose while resulting in a more efficient dosing at the target site.

Mechanistic three-dimensional model to study centrosome positioning in the interphase cell

During the interphase in mammalian cells, the position of the centrosome is actively maintained at a small but finite distance away from the nucleus. The perinuclear positioning of the centrosome is crucial for cellular trafficking and progression into mitosis. Although the literature suggests that the contributions of the microtubule-associated forces bring the centrosome to the center of the cell, the position of the centrosome was merely investigated in the absence of the nucleus. Upon performing a coarse-grained simulation study with mathematical analysis, we show that the combined effect of the forces due to the cell cortex and the nucleus facilitate the centrosome positioning. Our study also demonstrates that in the absence of nucleus-based forces, the centrosome collapses on the nucleus due to cortical forces. Depending upon the magnitudes of the cortical forces and the nucleus-based forces, the centrosome appears to stay at various distances away from the nucleus. Such null force regions are found to be stable as well as unstable fixed points. This study uncovers a set of redundant schemes that the cell may adopt to produce the required cortical and nucleus-based forces stabilizing the centrosome at a finite distance away from the nucleus.

Analysis of Microtubule Dynamics Heterogeneity in Cell Culture

Microtubules (MTs) are dynamic components of the cytoskeleton playing an important role in a large number of cell functions. Individual MTs in living cells undergo stochastic switching between alternate states of growth, shortening and attenuated phase, a phenomenon known as tempered dynamic instability. Dynamic instability of MTs is usually analyzed by labeling MTs with +TIPs, namely, EB proteins. Tracking of +TIP trajectories allows analyzing MT growth in cells with a different density of MTs. Numerous labs now use +TIP to track growing MTs in a variety of cell cultures. However, heterogeneity of MT dynamics is usually underestimated, and rather small sampling for the description of dynamic instability parameters is often used. The strategy described in this chapter is the method for repetitive quantitative analysis of MT growth rate within the same cell that allows minimization of the variation in MT dynamics measurement. We show that variability in MT dynamics within a cell when using repeated measurements is significantly less than between different cells in the same chamber. This approach allows better estimation of the heterogeneity of cells' responses to different treatments. To compare the effects of different MT inhibitors, the protocol using normalized values for MT dynamics and repetitive measurements for each cell is employed. This chapter provides detailed methods for analysis of MT dynamics in tissue cultures. We describe protocols for imaging MT dynamics by fluorescent microscopy, contrast enhancement technique, and MT dynamics analysis using triple color-coded display based on sequential subtraction analysis.

Dynamin impacts homology-directed repair and breast cancer response to chemotherapy

After the initial responsiveness of triple-negative breast cancers (TNBCs) to chemotherapy, they often recur as chemotherapy-resistant tumors, and this has been associated with upregulated homology-directed repair (HDR). Thus, inhibitors of HDR could be a useful adjunct to chemotherapy treatment of these cancers. We performed a high-throughput chemical screen for inhibitors of HDR from which we obtained a number of hits that disrupted microtubule dynamics. We postulated that high levels of the target molecules of our screen in tumors would correlate with poor chemotherapy response. We found that inhibition or knockdown of dynamin 2 (DNM2), known for its role in endocytic cell trafficking and microtubule dynamics, impaired HDR and improved response to chemotherapy of cells and of tumors in mice. In a retrospective analysis, levels of DNM2 at the time of treatment strongly predicted chemotherapy outcome for estrogen receptor-negative and especially for TNBC patients. We propose that DNM2-associated DNA repair enzyme trafficking is important for HDR efficiency and is a powerful predictor of sensitivity to breast cancer chemotherapy and an important target for therapy.

Sulforaphane-induced metabolomic responses with epigenetic changes in estrogen receptor positive breast cancer cells

Estrogen is a risk factor for breast cancer. The isothiocyanate sulforaphane (SFN), found in cruciferous vegetables, has been identified as an effective chemopreventive agent, and may prevent or treat breast cancer by reversing estrogen‐induced metabolic changes. Here, we investigated metabolic changes in estrogen receptor‐positive breast cancer (MCF‐7) cells treated with estradiol (E₂) and/or SFN to identify key metabolite panels that might provide new insights into the underlying mechanisms of the antitumor effects of SFN. Gas chromatography–mass spectrometry and ultra performance liquid chromatography–mass spectrometry (UPLC‐Orbitrap‐MS) were used to obtain the metabolic profiles of MCF‐7 cells. The data were analyzed using Student's t‐test and multivariate statistics, including principal component analysis and partial least squares discriminant analysis. Hydroxymethylation was detected by UPLC‐Orbitrap‐MS and verified by immunofluorescence assay. We report that significant changes in metabolites induced by E₂ and SFN were associated with differences in glycolysis and energy metabolism, and also amino acid, purine, and folic acid metabolism. E₂ may alter methylation and hydroxymethylation status via the folic acid pathway. We also identified biomarkers that may be of use in interpretation of the metabolic pathways evoked by the effects of E₂ and SFN on breast cancer cells. The identified biomarkers associated with metabolic pathways provide new insight into the chemopreventive mechanisms of SFN.

Ellagic acid, sulforaphane, and ursolic acid in the prevention and therapy of breast cancer: current evidence and future perspectives

Globally, breast cancer is the most common cancer and the second leading cause of cancer-related death among women. Surgery, chemotherapy, hormonal therapy, and radiotherapy are currently available treatment options for breast cancer therapy. However, chemotherapy, hormonal therapy, and radiotherapy are often associated with side effects and multidrug resistance, recurrence, and lack of treatment in metastasis are the major problems in the treatment of breast cancer. Recently, dietary phytochemicals have emerged as advantageous agents for the prevention and therapy of cancer due to their safe nature. Ellagic acid (EA), sulforaphane (SF), and ursolic acid (UA), which are found in widely consumed fruits and vegetables, have been shown to inhibit breast cancer cell proliferation and to induce apoptosis. This review encompasses the role of EA, SF, and UA in the fight against breast cancer. Both in vitro and in vivo effects of these agents are presented.

Sulforaphane metabolites cause apoptosis via microtubule disruption in cancer

Sulforaphane (SFN) inhibited growth in many cancers, but its half-life is 2 h in circulation. However, its metabolites, sulforaphane-cysteine (SFN-Cys) and sulforaphane-N-acetyl-cysteine (SFN-NAC) had longer half-lives and decreased the cell viability in both dose- and time-dependent manners in human prostate cancer. Flow cytometry assay revealed that these two SFN metabolites induced apoptosis with the features such as vacuolization, disappeared nuclear envelope, nuclear agglutination and fragmentation via transmission electron microscopy observation. Western blot showed that the sustained phosphorylation of ERK1/2 mediated by SFN metabolites caused activation and upregulation of cleaved Caspase 3 and downregulation of α-tubulin. High expression of α-tubulin was demonstrated to be positively correlated with cancer pathological grading. Both co-immunoprecipitation and immunofluorescence staining implicated the interaction between SFN metabolite-induced phosphorylated ERK1/2 and α-tubulin, and Caspase 3 cleavage assay showed that α-tubulin might be the substrate for cleaved Caspase 3. More, the SFN metabolite-mediated reduction of α-tubulin increased the depolymerization and instability of microtubules by microtubule polymerization assay. Reversely, microtubule-associated protein Stathmin-1 phosphorylation was increased via phosphorylated ERK1/2 and total Stathmin-1 was reduced, which might promote over-stability of microtubules. Immunofluorescence staining also showed that SFN metabolites induced the 'nest-like' structures of microtubule distribution resulting from the disrupted and aggregated microtubules, and abnormal nuclear division, suggesting that the disturbance of spindle formation and mitosis turned up. Thus, SFN-Cys and SFN-NAC triggered the dynamic imbalance of microtubules, microtubule disruption leading to cell apoptosis. These findings provided a novel insight into the chemotherapy of human prostate cancer.

Natural Compounds As Modulators of Non-apoptotic Cell Death in Cancer Cells

Cell death is an innate capability of cells to be removed from microenvironment, if and when they are damaged by multiple stresses. Cell death is often regulated by multiple molecular pathways and mechanism, including apoptosis, autophagy, and necroptosis. The molecular network underlying these processes is often intertwined and one pathway can dynamically shift to another one acquiring certain protein components, in particular upon treatment with various drugs. The strategy to treat human cancer ultimately relies on the ability of anticancer therapeutics to induce tumor-specific cell death, while leaving normal adjacent cells undamaged. However, tumor cells often develop the resistance to the drug-induced cell death, thus representing a great challenge for the anticancer approaches. Numerous compounds originated from the natural sources and biopharmaceutical industries are applied today in clinics showing advantageous results. However, some exhibit serious toxic side effects. Thus, novel effective therapeutic approaches in treating cancers are continued to be developed. Natural compounds with anticancer activity have gained a great interest among researchers and clinicians alike since they have shown more favorable safety and efficacy then the synthetic marketed drugs. Numerous studies in vitro and in vivo have found that several natural compounds display promising anticancer potentials. This review underlines certain information regarding the role of natural compounds from plants, microorganisms and sea life forms, which are able to induce non-apoptotic cell death in tumor cells, namely autophagy and necroptosis.

Nrf2 in health and disease: current and future clinical implications

The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is a major regulator of oxidative stress defence in the human body. As Nrf2 regulates the expression of a large battery of cytoprotective genes, it plays a crucial role in the prevention of degenerative disease in multiple organs. Thus it has been the focus of research as a pharmacological target that could be used for prevention and treatment of chronic diseases such as multiple sclerosis, chronic kidney disease or cardiovascular diseases. The present review summarizes promising findings from basic research and shows which Nrf2-targeting therapies are currently being investigated in clinical trials and which agents have already entered clinical practice.

Phytonutrients Differentially Stimulate NAD(P)H:Quinone Oxidoreductase, Inhibit Proliferation, and Trigger Mitotic Catastrophe in Hepa1c1c7 Cells

Phytonutrients have rapidly emerged as natural food chemicals possessing multifaceted biological actions that may support beneficial health outcomes. Among the vast array of phytonutrients currently being studied, sulforaphane, curcumin, quercetin, and resveratrol have been frequently reported to stimulate the expression of endogenous detoxification enzymes and may thereby facilitate the neutralization of otherwise harmful environmental agents. Some of these same phytonutrients, however, have also been implicated in disrupting normal cell proliferation and hence may possess toxic properties in and of themselves. In this study, we characterize the respective minimum threshold concentrations of the aforementioned phytonutrients in Hepa1c1c7 cells that stimulate

NAD(P)H

quinone oxidoreductase (NQO1), a key enzyme in the hepatic neutralization of menadione, other biological oxidants, and some environmental carcinogens. Moreover, our findings demonstrate that relatively low concentrations of either sulforaphane or curcumin significantly (P < .05) increase NQO1 protein expression and activity without triggering G2/M cell cycle arrest or mitotic catastrophe. The minimal quercetin concentration inducing NQO1, however, was 100-fold higher than that which disrupted mitosis. Also, while resveratrol modestly stimulated NQO1, the minimally effective resveratrol concentration concomitantly induced evidence of cellular apoptosis. Taken together, these findings indicate that only particular phytonutrients are likely efficacious in upregulating NQO1 activity without also leading to hepatic cytotoxicity.

Mechanical aspects of microtubule bundling in taxane-treated circulating tumor cells

Microtubules play an important role in many cellular processes, including mitotic spindle formation and cell division. Taxane-based anticancer treatments lead to the stabilization of microtubules, thus preventing the uncontrolled proliferation of tumor cells. One of the striking physical features of taxane-treated cells is the localization of their microtubules, which can be observed via fluorescent microscopy as an intense fluorescent band and are referred to as a microtubule bundle. With the recent advances in capturing and analyzing tumor cells circulating in a patient's blood system, there is increasing interest in using these cells to examine a patient's response to treatment. This includes taxanes that are used routinely in clinics to treat prostate, breast, lung, and other cancers. Here, we have used a computational model of microtubule mechanics to investigate self-arrangement patterns of stabilized microtubules, which allowed for the identification of specific combinations of three physical parameters: microtubule stiffness, intracellular viscosity, and cell shape, that can prevent the formation of microtubule bundles in cells with stabilized microtubules, such as taxane-treated cells. We also developed a method to quantify bundling in the whole microtubule aster structure and a way to compare the simulated results to fluorescent images from experimental data. Moreover, we investigated microtubule rearrangement in both suspended and attached cells and showed that the observed final microtubule patterns depend on the experimental protocol. The results from our computational studies can explain the heterogeneous bundling phenomena observed via fluorescent immunostaining from a mechanical point of view without relying on heterogeneous cellular responses to the microtubule-stabilizing drug.

α- and β-Santalols Directly Interact with Tubulin and Cause Mitotic Arrest and Cytotoxicity in Oral Cancer Cells

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide, with no major advancements in treatment over the past 40 years. The current study explores the biological effects of East Indian sandalwood oil (EISO) and its two major constituents, α- and β-santalol, against a variety of HNSCC lines. All three agents exhibited cytotoxic effects and caused accumulation of cells in the G2/M phases of the cell cycle. Additionally, treatment with these agents caused formation of multipolar mitotic spindles similar to those observed upon treatment of cells with compounds that affect microtubule polymerization. Indeed, the santalols, as well as EISO, inhibited the polymerization of purified tubulin, indicating for the first time that these compounds have the ability to directly bind to tubulin and affect microtubule formation. Modeling studies suggest that the santalols can weakly bind to the colchicine site on tubulin, and topical administration of EISO to a HNSCC xenograft inhibited tumor growth with no observed toxicities. Therefore, santalols can directly interact with tubulin to inhibit the polymerization of microtubules, similarly to established classes of chemotherapeutic agents, albeit with greatly reduced potency that is not associated with the classic toxicity associated with most other compounds that interact directly with tubulin.

Disintegration of microtubules in Arabidopsis thaliana and bladder cancer cells by isothiocyanates

Isothiocyanates (ITCs) from biodegradation of glucosinolates comprise a group of electrophiles associated with growth-inhibitory effects in plant- and mammalian cells. The underlying modes of action of this feature are not fully understood. Clarifying this has involved mammalian cancer cells due to ITCs' chemopreventive potential. The binding of ITCs to tubulins has been reported as a mechanism by which ITCs induce cell cycle arrest and apoptosis. In the present study we demonstrate that ITCs disrupt microtubules in Arabidopsis thaliana contributing to the observed inhibited growth phenotype. We also confirmed this in rat bladder cancer cells (AY-27) suggesting that cells from plant and animals share mechanisms by which ITCs affect growth. Exposure of A. thaliana to vapor-phase of allyl ITC (AITC) inhibited growth and induced a concurrent bleaching of leaves in a dose-dependent manner. Transcriptional analysis was used to show an upregulation of heat shock-genes upon AITC-treatment. Transgenic A. thaliana expressing GFP-marked α-tubulin was employed to show a time- and dose-dependent disintegration of microtubules by AITC. Treatment of AY-27 with ITCs resulted in a time- and dose-dependent decrease of cell proliferation and G2/M-arrest. AY-27 transiently transfected to express GFP-tagged α-tubulin were treated with ITCs resulting in a loss of microtubular filaments and the subsequent formation of apoptotic bodies. In conclusion, our data demonstrate an ITC-induced mechanism leading to growth inhibition in A. thaliana and rat bladder cancer cells, and expose clues to the mechanisms underlying the physiological role of glucosinolates in vivo.

Naturally occurring phenethyl isothiocyanate-induced inhibition of gastric cancer cell growth by disruption of microtubules

BACKGROUND AND AIM

Phenethyl isothiocyanate (PEITC) derives from vegetables commonly consumed by man and has been demonstrated as a promising chemopreventive agent against several types of cancer. However, the potential in preventing gastric cancer as well as the underlying mechanisms are to date not fully understood. The present study aimed at elucidating the cellular effects induced by PEITC in gastric cancer cells leading to apoptosis.

METHODS

The human gastric cancer cell lines Kato-III and MKN74 were employed. Cell proliferation was assayed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Morphology and migration were investigated through a contrast microscope. Cell cycle distribution was analyzed using flow cytometry of PI-stained cells. Microtubules were studied by confocal detection of Kato-III cells transfected to express GFP-tagged microtubules. Commercial kits were employed to study the effect of PEITC on apoptosis, caspase-3 activity, and glutathione content in MKN74 cells.

RESULTS

Kato-III and MKN74 cells responded, with different sensitivity, dose- and time-dependently in inhibition of cell proliferation to PEITC treatment. Further, PEITC induced aberrated cell morphologies and inhibited migration of MKN74 cells. Kato-III cells treated with PEITC accumulated in G2 /M phase and displayed a loss of microtubuli with the subsequent formation of apoptotic bodies. Although weak responses, MKN74 cells also accumulated in G2 /M phase, became apoptotic, increased caspase-3 activity, and suffered a reduction of glutathione pool.

CONCLUSION

Our findings demonstrate that PEITC induces disintegration of microtubules in human gastric cancer cells contributing to cell cycle arrest and ultimately apoptosis, contributing to an increased understanding of PEITC-induced inhibition of gastric cancer cell growth.

Systematic analysis of new drug indications by drug-gene-disease coherent subnetworks

Drug targets and disease genes may work as driver factors at the transcriptional level, which propagate signals through gene regulatory network and cause the downstream genes' differential expression. How to analyze transcriptional response data to identify meaningful gene modules shared by both drugs and diseases is still a critical issue for drug-disease associations and molecular mechanism. In this article, we propose the drug-gene-disease coherent subnetwork concept to group the biological function related drugs, diseases, and genes. It was defined as the subnetwork with drug, gene, and disease as nodes and their interactions coherently crossing three data layers as edges. Integrating differential expression profiles of 418 drugs and 84 diseases, we develop a computational framework and identify 13 coherent subnetworks such as inflammatory bowel disease and melanoma relevant subnetwork. The results demonstrate that our coherent subnetwork approach is able to identify novel drug indications and highlight their molecular basis.

Antiproliferative mechanism of action of the novel taxane cabazitaxel as compared with the parent compound docetaxel in MCF7 breast cancer cells

Cabazitaxel, a novel chemotherapeutic taxane, is effective against docetaxel-resistant cells and tumors. It is approved for treatment of metastatic hormone-refractory prostate cancer in patients pretreated with docetaxel. Objective responses have been observed in many other cancers, including pretreated metastatic breast cancer. Cabazitaxel and docetaxel share a high degree of structural similarity. The basis for cabazitaxel's efficacy is unclear, and its mechanism has not been described. We compared the effects of cabazitaxel and docetaxel on MCF7 human breast cancer cells expressing fluorescent tubulin. Both drugs inhibited cell proliferation (IC50s, cabazitaxel, 0.4 ± 0.1 nmol/L, docetaxel, 2.5 ± 0.5 nmol/L) and arrested cells in metaphase by inducing mitotic spindle abnormalities. Drug concentrations required for half-maximal mitotic arrest at 24 hours were similar (1.9 nmol/L cabazitaxel and 2.2 nmol/L docetaxel). Cabazitaxel suppressed microtubule dynamic instability significantly more potently than docetaxel. In particular, cabazitaxel (2 nmol/L) suppressed the microtubule shortening rate by 59% (compared with 49% for 2 nmol/L docetaxel), the growing rate by 33% (vs. 19%), and overall dynamicity by 83% (vs. 64%). Cabazitaxel was taken up into cells significantly faster than docetaxel, attaining an intracellular concentration of 25 μmol/L within 1 hour, compared with 10 hours for docetaxel. Importantly, after washing, the intracellular cabazitaxel concentration remained high, whereas the docetaxel concentration was significantly reduced. The data indicate that the potency of cabazitaxel in docetaxel-resistant tumors is due to stronger suppression of microtubule dynamics, faster drug uptake, and better intracellular retention than occurs with docetaxel.

Erucin, the major isothiocyanate in arugula (Eruca sativa), inhibits proliferation of MCF7 tumor cells by suppressing microtubule dynamics

Consumption of cruciferous vegetables is associated with reduced risk of various types of cancer. Isothiocyanates including sulforaphane and erucin are believed to be responsible for this activity. Erucin [1-isothiocyanato-4-(methylthio)butane], which is metabolically and structurally related to sulforaphane, is present in large quantities in arugula (Eruca sativa, Mill.), kohlrabi and Chinese cabbage. However, its cancer preventive mechanisms remain poorly understood. We found that erucin inhibits proliferation of MCF7 breast cancer cells (IC50 = 28 µM) in parallel with cell cycle arrest at mitosis (IC50 = 13 µM) and apoptosis, by a mechanism consistent with impairment of microtubule dynamics. Concentrations of 5-15 µM erucin suppressed the dynamic instability of microtubules during interphase in the cells. Most dynamic instability parameters were inhibited, including the rates and extents of growing and shortening, the switching frequencies between growing and shortening, and the overall dynamicity. Much higher erucin concentrations were required to reduce the microtubule polymer mass. In addition, erucin suppressed dynamic instability of microtubules reassembled from purified tubulin in similar fashion. The effects of erucin on microtubule dynamics, like those of sulforaphane, are similar qualitatively to those of much more powerful clinically-used microtubule-targeting anticancer drugs, including taxanes and the vinca alkaloids. The results suggest that suppression of microtubule dynamics by erucin and the resulting impairment of critically important microtubule-dependent cell functions such as mitosis, cell migration and microtubule-based transport may be important in its cancer preventive activities.

Exposure time independent summary statistics for assessment of drug dependent cell line growth inhibition

Background

In vitro generated dose-response curves of human cancer cell lines are widely used to develop new therapeutics. The curves are summarised by simplified statistics that ignore the conventionally used dose-response curves’ dependency on drug exposure time and growth kinetics. This may lead to suboptimal exploitation of data and biased conclusions on the potential of the drug in question. Therefore we set out to improve the dose-response assessments by eliminating the impact of time dependency.

Results

First, a mathematical model for drug induced cell growth inhibition was formulated and used to derive novel dose-response curves and improved summary statistics that are independent of time under the proposed model. Next, a statistical analysis workflow for estimating the improved statistics was suggested consisting of 1) nonlinear regression models for estimation of cell counts and doubling times, 2) isotonic regression for modelling the suggested dose-response curves, and 3) resampling based method for assessing variation of the novel summary statistics. We document that conventionally used summary statistics for dose-response experiments depend on time so that fast growing cell lines compared to slowly growing ones are considered overly sensitive. The adequacy of the mathematical model is tested for doxorubicin and found to fit real data to an acceptable degree. Dose-response data from the NCI60 drug screen were used to illustrate the time dependency and demonstrate an adjustment correcting for it. The applicability of the workflow was illustrated by simulation and application on a doxorubicin growth inhibition screen. The simulations show that under the proposed mathematical model the suggested statistical workflow results in unbiased estimates of the time independent summary statistics. Variance estimates of the novel summary statistics are used to conclude that the doxorubicin screen covers a significant diverse range of responses ensuring it is useful for biological interpretations.

Conclusion

Time independent summary statistics may aid the understanding of drugs’ action mechanism on tumour cells and potentially renew previous drug sensitivity evaluation studies.

Phytochemicals from cruciferous vegetables, epigenetics, and prostate cancer prevention

Epidemiological evidence has demonstrated a reduced risk of prostate cancer associated with cruciferous vegetable intake. Follow-up studies have attributed this protective activity to the metabolic products of glucosinolates, a class of secondary metabolites produced by crucifers. The metabolic products of glucoraphanin and glucobrassicin, sulforaphane, and indole-3-carbinol respectively, have been the subject of intense investigation by cancer researchers. Sulforaphane and indole-3-carbinol inhibit prostate cancer by both blocking initiation and suppressing prostate cancer progression in vitro and in vivo. Research has largely focused on the anti-initiation and cytoprotective effects of sulforaphane and indole-3-carbinol through induction of phases I and II detoxification pathways. With regards to suppressive activity, research has focused on the ability of sulforaphane and indole-3-carbinol to antagonize cell signaling pathways known to be dysregulated in prostate cancer. Recent investigations have characterized the ability of sulforaphane and indole-3-carbinol derivatives to modulate the activity of enzymes controlling the epigenetic status of prostate cancer cells. In this review, we will summarize the well-established, "classic" non-epigenetic targets of sulforaphane and indole-3-carbinol, and highlight more recent evidence supporting these phytochemicals as epigenetic modulators for prostate cancer chemoprevention.

Rearrangement of microtubule network under biochemical and mechanical stimulations

Cells are constantly under the influence of various external forces in their physiological environment. These forces are countered by the viscoelastic properties of the cytoskeleton. To understand the response of the cytoskeleton to biochemical and mechanical stimuli, GFP-tubulin expressing CHO cells were investigated using scanning laser confocal microscopy. Cells treated with nocodazole revealed disruption in the microtubule network within minutes of treatment while keeping the cell shape intact. By contrast, trypsin, a proteolytic agent, altered the shape of CHO cells by breaking the peptide bonds at adhesion sites. CHO cells were also stimulated mechanically by applying an indentation force with an atomic force microscope (AFM) and by shear stress in a parallel plate flow chamber. Mechanical stimulation applied using AFM showed two distinct cytoskeletal responses to the applied force: an immediate response that resulted in the depolymerization and displacement of the microtubules out of the contact zone, and a slower response characterized by tubulin polymerization at the periphery of the indented area. Flow chamber experiments revealed that shear force did not induce formation of new microtubules in CHO cells and that detachment of adherent cells from the substrate occurred independent from the flow direction. Overall, the experimental system described here allows real-time characterization of dynamic changes in cell cytoskeleton in response to the mechano-chemical stimuli and, therefore, provides better understanding of the biophysical and functional properties of cells.

Sulforaphane inhibits growth of phenotypically different breast cancer cells

Purpose

Cancer development and resistance to chemotherapy correlates with aberrant activity of mitogenic pathways. In breast cancers, pro-survival PI3K-AktmTOR-S6K1 signaling pathway is often hyperactive due to overexpression of genes coding for growth factors or estrogen receptors, constitutive activation of PI3K or Akt and loss of PTEN, a negative regulator of the pathway. Since epidemiologic as well as rodent tumor studies indicate that sulforaphane (SFN), a constituent of many edible cruciferous vegetables, might be a potent inhibitor of mammary carcinogenesis, we analyzed the response of four breast cancer cell lines representing different abnormalities in ErbB2/ER-PI3K-AktmTOR-S6K1 signaling pathway to this compound.

Methods

Four different breast cancer cell lines were used: MDA MB 231, MCF-7, SKBR-3 and MDA MB 468. Cell viability and ultrastructure, protein synthesis, autophagy induction and phosphorylation status of Akt and S6K1 kinases upon SFN treatment were determined.

Results

We observed that all four cell lines are similarly sensitive to SFN. SFN decreased phosphorylation of Akt and S6K1 kinases and at higher concentrations induced autophagy in all studied cell lines. Moreover, global protein synthesis was inhibited by SFN in investigated cell lines in a dose-dependent manner.

Conclusion

These results indicate that SFN is a potent inhibitor of the viability of breast cancer cells representing different activity of the ErbB2/ER-PI3K-AktmTOR-S6K1 pro-survival pathway and suggest that it targets downstream elements of the pathway.

Formation of new high density glycogen-microtubule structures is induced by cardiac steroids

Cardiac steroids (CS), an important class of naturally occurring compounds, are synthesized in plants and animals. The only established receptor for CS is the ubiquitous Na(+),K(+)-ATPase, a major plasma membrane transporter. The binding of CS to Na(+),K(+)-ATPase causes the inhibition of Na(+) and K(+) transport and elicits cell-specific activation of several intracellular signaling mechanisms. It is well documented that the interaction of CS with Na(+),K(+)-ATPase is responsible for numerous changes in basic cellular physiological properties, such as electrical plasma membrane potential, cell volume, intracellular [Ca(2+)] and pH, endocytosed membrane traffic, and the transport of other solutes. In the present study we show that CS induces the formation of dark structures adjacent to the nucleus in human NT2 and ACHN cells. These structures, which are not surrounded by membranes, are clusters of glycogen and a distorted microtubule network. Formation of these clusters results from a relocation of glycogen and microtubules in the cells, two processes that are independent of one another. The molecular mechanisms underlying the formation of the clusters are mediated by the Na(+),K(+)-ATPase, ERK1/2 signaling pathway, and an additional unknown factor. Similar glycogen clusters are induced by hypoxia, suggesting that the CS-induced structural change, described in this study, may be part of a new type of cellular stress response.

Natural isothiocyanates: genotoxic potential versus chemoprevention

Isothiocyanates, occurring in many dietary cruciferous vegetables, show interesting chemopreventive activities against several chronic-degenerative diseases, including cancer, cardiovascular diseases, neurodegeneration, diabetes. The electrophilic carbon residue in the isothiocyanate moiety reacts with biological nucleophiles and modification of proteins is recognized as a key mechanism underlying the biological activity of isothiocyanates. The nuclear factor-erythroid-2-related factor 2 system, which orchestrates the expression of a wide array of antioxidant genes, plays a role in the protective effect of isothiocyanates against almost all the pathological conditions reported above. Recent emerging findings suggest a further common mechanism. Chronic inflammation plays a central role in many human diseases and isothiocyanates inhibit the activity of many inflammation components, suppress cyclooxygenase 2, and irreversibly inactivate the macrophage migration inhibitory factor. Due to their electrophilic reactivity, some isothiocyanates are able to form adducts with DNA and induce gene mutations and chromosomal aberrations. DNA damage has been demonstrated to be involved in the pathogenesis of various chronic-degenerative diseases of epidemiological relevance. Thus, the genotoxicity of the isothiocyanates should be carefully considered. In addition, the dose-response relationship for genotoxic compounds does not suggest evidence of a threshold. Thus, chemicals that are genotoxic pose a greater potential risk to humans than non-genotoxic compounds. Dietary consumption levels of isothiocyanates appear to be several orders of magnitude lower than the doses used in the genotoxicity studies and thus it is highly unlikely that such toxicities would occur in humans. However, the beneficial properties of isothiocyanates stimulated an increase of dietary supplements and functional foods with highly enriched isothiocyanate concentrations on the market. Whether such concentrations may exert a potential health risk cannot be excluded with certainty and an accurate evaluation of the toxicological profile of isothiocyanates should be prompted before any major increase in their consumption be recommended or their clinical use suggested.

Phytochemicals of Brassicaceae in plant protection and human health--influences of climate, environment and agronomic practice

In this review, we provide an overview of the role of glucosinolates and other phytochemical compounds present in the Brassicaceae in relation to plant protection and human health. Current knowledge of the factors that influence phytochemical content and profile in the Brassicaceae is also summarized and multi-factorial approaches are briefly discussed. Variation in agronomic conditions (plant species, cultivar, developmental stage, plant organ, plant competition, fertilization, pH), season, climatic factors, water availability, light (intensity, quality, duration) and CO(2) are known to significantly affect content and profile of phytochemicals. Phytochemicals such as the glucosinolates and leaf surface waxes play an important role in interactions with pests and pathogens. Factors that affect production of phytochemicals are important when designing plant protection strategies that exploit these compounds to minimize crop damage caused by plant pests and pathogens. Brassicaceous plants are consumed increasingly for possible health benefits, for example, glucosinolate-derived effects on degenerative diseases such as cancer, cardiovascular and neurodegenerative diseases. Thus, factors influencing phytochemical content and profile in the production of brassicaceous plants are worth considering both for plant and human health. Even though it is known that factors that influence phytochemical content and profile may interact, studies of plant compounds were, until recently, restricted by methods allowing only a reductionistic approach. It is now possible to design multi-factorial experiments that simulate their combined effects. This will provide important information to ecologists, plant breeders and agronomists.

Differential effects of sulforaphane on histone deacetylases, cell cycle arrest and apoptosis in normal prostate cells versus hyperplastic and cancerous prostate cells

SCOPE

Sulforaphane (SFN) is an isothiocyanate derived from cruciferous vegetables such as broccoli. The ability of SFN to inhibit histone deacetylase (HDAC) enzymes may be one mechanism by which it acts as a chemoprevention agent. The ability of a chemopreventive agent to specifically cause cytotoxicity in cancer and not normal cells is an important factor in determining its safety and clinical relevance.

METHODS AND RESULTS

We characterized the effects of SFN in normal (PrEC), benign hyperplasia (BPH1) and cancerous (LnCap and PC3) prostate epithelial cells. We observed that 15 μM SFN selectively induced cell cycle arrest and apoptosis in BPH1, LnCap and PC3 cells but not PrEC cells. SFN treatment also selectively decreased HDAC activity, and Class I and II HDAC proteins, increased acetylated histone H3 at the promoter for P21, induced p21 expression and increased tubulin acetylation in prostate cancer cells. HDAC6 over-expression was able to reverse SFN-induced cyotoxicity. In PrEC cells, SFN caused only a transient reduction in HDAC activity with no change in any other endpoints tested. The differences in sensitivity to SFN in PrEC and PC3 are likely not due to differences in SFN metabolism or differences in phase 2 enzyme induction.

CONCLUSION

SFN exerts differential effects on cell proliferation, HDAC activity and downstream targets in normal and cancer cells.

Microtubule-binding agents: a dynamic field of cancer therapeutics

Microtubules are dynamic filamentous cytoskeletal proteins composed of tubulin and are an important therapeutic target in tumour cells. Agents that bind to microtubules have been part of the pharmacopoeia of anticancer therapy for decades and until the advent of targeted therapy, microtubules were the only alternative to DNA as a therapeutic target in cancer. The screening of a range of botanical species and marine organisms has yielded promising new antitubulin agents with novel properties. In the current search for novel microtubule-binding agents, enhanced tumour specificity, reduced neurotoxicity and insensitivity to chemoresistance mechanisms are the three main objectives.

Maytansinoid-antibody conjugates induce mitotic arrest by suppressing microtubule dynamic instability

Maytansine and its analogues (maytansinoids) are potent microtubule-targeted compounds that inhibit proliferation of cells at mitosis. Antibody-maytansinoid conjugates consisting of maytansinoids (DM1 and DM4) attached to tumor-specific antibodies have shown promising clinical results. To determine the mechanism by which the antibody-DM1 conjugates inhibit cell proliferation, we examined the effects of the cleavable anti-EpCAM-SPP-DM1 and uncleavable anti-EpCAM-SMCC-DM1 conjugates on MCF7 human breast tumor cells. We also examined the effects of the free maytansinoids, maytansine and S-methyl DM1 (a version of DM1 that is stable in cell culture medium), for comparison. Both the conjugates and free maytansinoids potently inhibited MCF7 cell proliferation at nanomolar and subnanomolar concentrations, respectively, by arresting the cells in mitotic prometaphase/metaphase. Arrest occurred in concert with the internalization and intracellular processing of both conjugates under conditions that induced abnormal spindle organization and suppressed microtubule dynamic instability. Microtubule depolymerization occurred only at significantly higher drug concentrations. The results indicate that free maytansinoids, antibody-maytansinoid conjugates, and their metabolites exert their potent antimitotic effects through a common mechanism involving suppression of microtubule dynamic instability.

The neuroprotective peptide NAP does not directly affect polymerization or dynamics of reconstituted neural microtubules

NAP (Asn-Ala-Pro-Val-Ser-Ile-Pro-Gln) is a neuroprotective peptide that shows cognitive protection in patients with amnestic mild cognitive impairment, a precursor to Alzheimer's disease. NAP exhibits potent neuroprotective properties in several in vivo and cellular models of neural injury. While NAP has been found in many studies to affect microtubule assembly and/or stability in neuronal and glial cells at fM concentrations, it has remained unclear whether NAP acts directly or indirectly on tubulin or microtubules. We analyzed the effects of NAP (1 fM-1 microM) on the assembly of reconstituted bovine brain microtubules in vitro and found that it did not significantly (p< 0.05) alter polymerization of either purified tubulin or of a mixture of tubulin and unfractionated microtubule-associated proteins. NAP also had no significant effect (p < 0.05) on the growing and shortening dynamics of steady-state microtubules at their plus ends, nor did it alter the polymerization or dynamics of microtubules assembled in the presence of 3-repeat or 4-repeat tau. Thus, the neuroprotective activity of NAP does not appear to involve a direct action on the polymerization or dynamics of purified tubulin or microtubules.

Sulforaphane, a dietary component of broccoli/broccoli sprouts, inhibits breast cancer stem cells

PURPOSE

The existence of cancer stem cells (CSCs) in breast cancer has profound implications for cancer prevention. In this study, we evaluated sulforaphane, a natural compound derived from broccoli/broccoli sprouts, for its efficacy to inhibit breast CSCs and its potential mechanism.

EXPERIMENTAL DESIGN

Aldefluor assay and mammosphere formation assay were used to evaluate the effect of sulforaphane on breast CSCs in vitro. A nonobese diabetic/severe combined immunodeficient xenograft model was used to determine whether sulforaphane could target breast CSCs in vivo, as assessed by Aldefluor assay, and tumor growth upon cell reimplantation in secondary mice. The potential mechanism was investigated using Western blotting analysis and beta-catenin reporter assay.

RESULTS

Sulforaphane (1-5 micromol/L) decreased aldehyde dehydrogenase-positive cell population by 65% to 80% in human breast cancer cells (P < 0.01) and reduced the size and number of primary mammospheres by 8- to 125-fold and 45% to 75% (P < 0.01), respectively. Daily injection with 50 mg/kg sulforaphane for 2 weeks reduced aldehyde dehydrogenase-positive cells by >50% in nonobese diabetic/severe combined immunodeficient xenograft tumors (P = 0.003). Sulforaphane eliminated breast CSCs in vivo, thereby abrogating tumor growth after the reimplantation of primary tumor cells into the secondary mice (P < 0.01). Western blotting analysis and beta-catenin reporter assay showed that sulforaphane downregulated the Wnt/beta-catenin self-renewal pathway.

CONCLUSIONS

Sulforaphane inhibits breast CSCs and downregulates the Wnt/beta-catenin self-renewal pathway. These findings support the use of sulforaphane for the chemoprevention of breast cancer stem cells and warrant further clinical evaluation.

Natural product derivative Bis(4-fluorobenzyl)trisulfide inhibits tumor growth by modification of beta-tubulin at Cys 12 and suppression of microtubule dynamics

Bis(4-fluorobenzyl)trisulfide (BFBTS) is a synthetic molecule derived from a bioactive natural product, dibenzyltrisulfide, found in a subtropical shrub, Petiveria allieacea. BFBTS has potent anticancer activities to a broad spectrum of tumor cell lines with IC50 values from high nanomolar to low micromolar and showed equal anticancer potency between tumor cell lines overexpressing multidrug-resistant gene, MDR1 (MCF7/adr line and KBv200 line), and their parental MCF7 line and KB lines. BFBTS inhibited microtubule polymerization dynamics in MCF7 cells, at a low nanomolar concentration of 54 nmol/L, while disrupting microtubule filaments in cells at low micromolar concentration of 1 micromol/L. Tumor cells treated with BFBTS were arrested at G2-M phase, conceivably resulting from BFBTS-mediated antimicrotubule activities. Mass spectrometry studies revealed that BFBTS bound and modified beta-tubulin at residue Cys12, forming beta-tubulin-SS-fluorobenzyl. The binding site differs from known antimicrotubule agents, suggesting that BFBTS functions as a novel antimicrotubule agent. BFBTS at a dose of 25 mg/kg inhibited tumor growth with relative tumor growth rates of 19.91%, 18.5%, and 23.42% in A549 lung cancer, Bcap-37 breast cancer, and SKOV3 ovarian cancer xenografts, respectively. Notably, BFBTS was more potent against MDR1-overexpressing MCF7/adr breast cancer xenografts with a relative tumor growth rate of 12.3% than paclitaxel with a rate of 43.0%. BFBTS displays a novel antimicrotubule agent with potentials for cancer therapeutics.