Resveratrol impairs the formation of MDA-MB-231 multicellular tumor spheroids concomitant with ceramide accumulation

Sphingolipid Levels and Signaling via Resveratrol and Antioxidant Actions in Cardiometabolic Risk and Disease

Resveratrol (RSV) is a phenolic compound with strong antioxidant activity, which is generally associated with the beneficial effects of wine on human health. All resveratrol-mediated benefits exerted on different systems and pathophysiological conditions are possible through resveratrol's interactions with different biological targets, along with its involvement in several key cellular pathways affecting cardiometabolic (CM) health. With regard to its role in oxidative stress, RSV exerts its antioxidant activity not only as a free radical scavenger but also by increasing the activity of antioxidant enzymes and regulating redox genes, nitric oxide bioavailability and mitochondrial function. Moreover, several studies have demonstrated that some RSV effects are mediated by changes in sphingolipids, a class of biolipids involved in a number of cellular functions (e.g., apoptosis, cell proliferation, oxidative stress and inflammation) that have attracted interest as emerging critical determinants of CM risk and disease. Accordingly, this review aimed to discuss the available data regarding the effects of RSV on sphingolipid metabolism and signaling in CM risk and disease, focusing on oxidative stress/inflammatory-related aspects, and the clinical implications of this relationship.

NAD+ supplementation limits triple-negative breast cancer metastasis via SIRT1-P66Shc signaling

NAD⁺ levels decline with age and in certain disease conditions. NAD⁺ precursors have been shown to stimulate NAD⁺ biosynthesis and ameliorate various age-associated diseases in mouse models. However, NAD⁺ metabolism is complicated in cancer and its role in triple-negative breast cancer (TNBC) remains elusive. Here, we show that NAD⁺ supplement suppresses tumor metastasis in a TNBC orthotopic patient-derived xenograft (PDX) model. Sirtuin1 lysine deacetylase (SIRT1) is required for the effects since SIRT1 knockdown blocks NAD⁺-suppressed tumor metastasis. Overexpression of SIRT1 effectively impairs the metastatic potential of TNBC. Importantly, the interaction between SIRT1 and p66Shc causes the deacetylation and functional inactivation of p66Shc, which inhibits epithelial-mesenchymal transition (EMT). Overall, we demonstrate that NAD⁺ supplementation executes its anti-tumor function via activating the SIRT1-p66Shc axis, which highlights the preventive and therapeutic potential of SIRT1 activators as effective interventions for TNBC.

Resveratrol Affects Sphingolipid Metabolism in A549 Lung Adenocarcinoma Cells

Resveratrol is a naturally occurring polyphenol which has various beneficial effects, such as anti-inflammatory, anti-tumor, anti-aging, antioxidant, and neuroprotective effects, among others. The anti-cancer activity of resveratrol has been related to alterations in sphingolipid metabolism. We analyzed the effect of resveratrol on the enzymes responsible for accumulation of the two sphingolipids with highest functional activity—apoptosis promoting ceramide (CER) and proliferation-stimulating sphingosine-1-phosphate (S1P)—in human lung adenocarcinoma A549 cells. Resveratrol treatment induced an increase in CER and sphingosine (SPH) and a decrease in sphingomyelin (SM) and S1P. Our results showed that the most common mode of CER accumulation, through sphingomyelinase-induced hydrolysis of SM, was not responsible for a CER increase despite the reduction in SM in A549 plasma membranes. However, both the activity and the expression of CER synthase 6 were upregulated in resveratrol-treated cells, implying that CER was accumulated as a result of stimulated de novo synthesis. Furthermore, the enzyme responsible for CER hydrolysis, alkaline ceramidase, was not altered, suggesting that it was not related to changes in the CER level. The enzyme maintaining the balance between apoptosis and proliferation, sphingosine kinase 1 (SK1), was downregulated, and its expression was reduced, resulting in a decrease in S1P levels in resveratrol-treated lung adenocarcinoma cells. In addition, incubation of resveratrol-treated A549 cells with the SK1 inhibitors DMS and fingolimod additionally downregulated SK1 without affecting its expression. The present studies provide information concerning the biochemical processes underlying the influence of resveratrol on sphingolipid metabolism in A549 lung cancer cells and reveal possibilities for combined use of polyphenols with specific anti-proliferative agents that could serve as the basis for the development of complex therapeutic strategies.

Differential in vitro anti-leukemic activity of resveratrol combined with serine palmitoyltransferase inhibitor myriocin in FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) carrying AML cells

Treatment of FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication (ITD) AML is restricted due to toxicity, drug resistance and relapse eventhough targeted therapies are clinically available. Resveratrol with its multi-targeted nature is a promising chemopreventive remaining limitedly studied in FLT3-ITD AML regarding to ceramide metabolism. Here, its cytotoxic, cytostatic and apoptotic effects are investigated in combination with serine palmitoyltransferase (SPT), the first enzyme of de novo pathway of ceramide production, inhibitor myriocin on MOLM-13 and MV4-11 cells. We assessed dose-dependent cell viability, flow cytometric cell death and cell cycle profiles of resveratrol in combination with myriocin by MTT assay, annexin-V/PI staining and PI staining respectively. Resveratrol's dose-dependent effect on SPT protein expression was also checked by western blot. Resveratrol decreased cell viability in a dose- dependent manner whereas myriocin did not affect cell proliferation effectively in both cell lines after 48h treatments. Although resveratrol induced both apoptosis and a significant S phase arrest in MV4-11 cells, it triggered apoptosis and non-significant S phase accumulation in MOLM-13 cells. Co-administrations reduced cell viability. Increased cytotoxic effect of co-treatments was further proved mechanistically through induction of apoptosis via phosphatidylserine relocalization. The cell cycle alteration in co-treatment was significant with an S phase arrest in MV4-11 cells, however, it was not effective on cell cycle progression of MOLM-13 cells. Resveratrol also increased SPT expression. Overall, modulation of SPT together with resveratrol might be the possible explanation for resveratrol's action. It could be an integrative medicine for FLT3-ITD AML after investigating its detailed mechanism of action in relation to de novo pathway of ceramide production.

The Potential of Natural Products in the Treatment of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a subtype of breast cancer that lacks receptors for targeted therapy. Consequently, chemotherapy is currently the mainstay of systemic treatment options. However, the enrichment of cancer stem cells (CSC, a subpopulation with stem-cell characteristics and tumor-initiating propensity) promotes chemo-resistance and tumorigenesis, resulting in cancer recurrence and relapse. Furthermore, toxic side effects of chemotherapeutics reduce patient wellbeing. Natural products, specifically compounds derived from plants, have the potential to treat TNBC and target CSCs by inhibiting CSC signaling pathways. Literature evidence from six promising compounds were reviewed, including sulforaphane, curcumin, genistein, resveratrol, lycopene, and epigallocatechin-3-gallate. These compounds have been shown to promote cell cycle arrest and apoptosis in TNBC cells. They also could inhibit the epithelial-mesenchymal transition (EMT) that plays an important role in metastasis. In addition, those natural compounds have been found to inhibit pathways important for CSCs, such as NF-κB, PI3K/Akt/mTOR, Notch 1, Wnt/β-catenin, and YAP. Clinicals trials conducted on these compounds have shown varying degrees of effectiveness. Epidemiological case-control studies for the compounds commonly consumed in certain human populations have also been summarized. While in vivo and in vitro data are promising, further basic and clinical investigations are required. Likely, natural products in combination with other drugs may hold great potential to improve TNBC treatment efficacy and patient outcomes.

Cancer Prevention and Therapy with Polyphenols: Sphingolipid-Mediated Mechanisms

Polyphenols, chemically characterized by a polyhydroxylated phenolic structure, are well known for their widespread pharmacological properties: anti-inflammatory, antibiotic, antiseptic, antitumor, antiallergic, cardioprotective and others. Their distribution in food products is also extensive especially in plant foods such as vegetables, cereals, legumes, fruits, nuts and certain beverages. The latest scientific literature outlines a resilient interconnection between cancer modulation and dietary polyphenols by sphingolipid-mediated mechanisms, usually correlated with a modification of their metabolism. We aim to extensively survey this relationship to show how it could be advantageous in cancer treatment or prevention by nutrients. From this analysis it emerges that a combination of classical chemotherapy with nutrients and especially with polyphenols dietary sources may improve efficacy and decreases negative side effects of the antineoplastic drug. In this multifaceted scenario, sphingolipids play a pivotal role as bioactive molecules, emerging as the mediators of cell proliferation in cancer and modulator of chemotherapeutics.

Resveratrol for breast cancer prevention and therapy: Preclinical evidence and molecular mechanisms

Globally, breast cancer is the most frequently diagnosed cancer among women. The major unresolved problems with metastatic breast cancer is recurrence after receiving objective response to chemotherapy, drug-induced side effects of first line chemotherapy and delayed response to second line of treatment. Unfortunately, very few options are available as third line treatment. It is clear that under such circumstances there is an urgent need for new and effective drugs. Phytochemicals are among the most promising chemopreventive treatment options for the management of cancer. Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a non-flavonoid polyphenol present in several dietary sources, including grapes, berries, soy beans, pomegranate and peanuts, has been shown to possess a wide range of health benefits through its effect on a plethora of molecular targets.The present review encompasses the role of resveratrol and its natural/synthetic analogue in the light of their efficacy against tumor cell proliferation, metastasis, epigenetic alterations and for induction of apoptosis as well as sensitization toward chemotherapeutic drugs in various in vitro and in vivo models of breast cancer. The roles of resveratrol as a phytoestrogen, an aromatase inhibitor and in stem cell therapy as well as adjuvent treatment are also discussed. This review explores the full potential of resveratrol in breast cancer prevention and treatment with current limitations, challenges and future directions of research.

Resveratrol, Acetyl-Resveratrol, and Polydatin Exhibit Antigrowth Activity against 3D Cell Aggregates of the SKOV-3 and OVCAR-8 Ovarian Cancer Cell Lines

Resveratrol has aroused significant scientific interest as it has been claimed that it exhibits a spectrum of health benefits. These include effects as an anti-inflammatory and an antitumour compound. The purpose of this study was to investigate and compare any potential antigrowth effects of resveratrol and two of its derivatives, acetyl-resveratrol and polydatin, on 3D cell aggregates of the EGFR/Her-2 positive and negative ovarian cancer cell lines SKOV-3 and OVCAR-8, respectively. Results showed that resveratrol and acetyl-resveratrol reduced cell growth in the SKOV-3 and OVCAR-8 in a dose-dependant manner. The growth reduction was mediated by the induction of apoptosis via the cleavage of poly(ADP-ribose) polymerase (PARP-1). At lower concentrations, 5 and 10 µM, resveratrol, acetyl-resveratrol, and polydatin were less effective than higher concentrations, 50 and 100 µM. In SKOV-3 line, at higher concentrations, resveratrol and polydatin significantly reduced the phosphorylation of Her-2 and EGFR and the expression of Erk. Acetyl-resveratrol, on the other hand, did not change the activation of Her-2 and EGFR. Resveratrol, acetyl-resveratrol, and polydatin suppressed the secretion of VEGF in a dose-dependant fashion. In the OVCAR-8 cell line, resveratrol and acetyl-resveratrol at 5 and 10 µM increased the activation of Erk. Above these concentrations they decreased activation. Polydatin did not produce this effect. This study demonstrates that resveratrol and its derivatives may inhibit growth of 3D cell aggregates of ovarian cancer cell lines via different signalling molecules. Resveratrol and its derivatives, therefore, warrant further in vivo evaluation to assess their potential clinical utility.

Inhibitors of dihydroceramide desaturase 1: Therapeutic agents and pharmacological tools to decipher the role of dihydroceramides in cell biology

Dihydroceramide desaturase (Des1) is the last enzyme in the de novo synthesis of ceramides (Cer). It catalyzes the insertion of a double bond into dihydroceramides (dhCer) to convert them to Cer, both of which are further metabolized to more complex (dihydro) sphingolipids. For many years dhCer have received poor attention, mainly due to their supposed lack of biological activity. It was not until about ten years ago that the concept that dhCer might have regulatory roles in biology emerged for the first time. Since then, multiple publications have established that dhCer are implicated in a wide spectrum of biological processes. Physiological and pathophysiological functions of dhCer have been recently reviewed. In this review we will focus on the biochemical features of Des1 and on its inhibition by different compounds with presumably different modes of action.

Resveratrol and its oligomers: modulation of sphingolipid metabolism and signaling in disease

Resveratrol, a natural compound endowed with multiple health-promoting effects, has received much attention given its potential for the treatment of cardiovascular, inflammatory, neurodegenerative, metabolic and age-related diseases. However, the translational potential of resveratrol has been limited by its specificity, poor bioavailability and uncertain toxicity. In recent years, there has been an accumulation of evidence demonstrating that resveratrol modulates sphingolipid metabolism. Moreover, resveratrol forms higher order oligomers that exhibit better selectivity and potency in modulating sphingolipid metabolism. This review evaluates the evidence supporting the modulation of sphingolipid metabolism and signaling as a mechanism of action underlying the therapeutic efficacy of resveratrol and oligomers in diseases, such as cancer.

Resveratrol stimulates sphingosine-1-phosphate signaling of cathelicidin production

We recently discovered a regulatory mechanism that stimulates production of the multifunctional antimicrobial peptide, cathelicidin antimicrobial peptide (CAMP). In response to subtoxic levels of ER stress, increased sphingosine-1-phosphate (S1P) production activates an NFκB→C/EBPα dependent pathway that enhances CAMP production in cultured human keratinocytes. Since the multifunctional stilbenoid compound, resveratrol (RESV), increases ceramide (Cer) levels, a precursor of S1P, we hypothesized and assessed whether RESV could exploit the same pathway to regulate CAMP production. Accordingly, RESV significantly increased Cer and S1P levels in cultured keratinocytes, paralleled by increased CAMP mRNA/protein expression. Furthermore, topical RESV also increased murine CAMP mRNA/protein expression in mouse skin. Conversely, blockade of Cer→sphingosine→S1P metabolic conversion, with specific inhibitors of ceramidase or sphingosine kinase, attenuated the expected RESV-mediated increase in CAMP expression. The RESV-induced increase in CAMP expression required both NF-κB and C/EBPα transactivation. Moreover, conditioned media from keratinocyte treated with RESV significantly suppressed Staphylococcus aureus growth. Finally, topical RESV, if not coapplied with a specific inhibitor of sphingosine kinase, blocked Staphylococcus aureus invasion into murine skin. These results demonstrate that the dietary stilbenoid, RESV, stimulates S1P signaling of CAMP production through an NF-κB→C/EBPα-dependent mechanism, leading to enhanced antimicrobial defense against exogenous microbial pathogens.

Dihydroceramide desaturase and dihydrosphingolipids: debutant players in the sphingolipid arena

Sphingolipids are a wide family of lipids that share common sphingoid backbones, including (2S,3R)-2-amino-4-octadecane-1,3-diol (dihydrosphingosine) and (2S,3R,4E)-2-amino-4-octadecene-1,3-diol (sphingosine). The metabolism and biological functions of sphingolipids derived from sphingosine have been the subject of many reviews. In contrast, dihydrosphingolipids have received poor attention, mainly due to their supposed lack of biological activity. However, the reported biological effects of active site directed dihydroceramide desaturase inhibitors and the involvement of dihydrosphingolipids in the response of cells to known therapeutic agents support that dihydrosphingolipids are not inert but are in fact biologically active and underscore the importance of elucidating further the metabolic pathways and cell signaling networks involved in the biological activities of dihydrosphingolipids. Dihydroceramide desaturase is the enzyme involved in the conversion of dihydroceramide into ceramide and it is crucial in the regulation of the balance between sphingolipids and dihydrosphingolipids. Furthermore, given the enzyme requirement for O₂ and the NAD(P)H cofactor, the cellular redox balance and dihydroceramide desaturase activity may reciprocally influence each other. In this review both dihydroceramide desaturase and the biological functions of dihydrosphingolipids are addressed and perspectives on this field are discussed.

Resveratrol triggers apoptosis through regulating ceramide metabolizing genes in human K562 chronic myeloid leukemia cells

Resveratrol, an important phytoalexin in many plants, has been reported to have cytotoxic effects on various types of cancer. Ceramide is a bioactive sphingolipid that regulates many signaling pathways, including cell growth and proliferation, senescence and quiescence, apoptosis, and cell cycle. Ceramides are generated by longevity assurance genes (LASS). Glucosylceramide synthase (GCS) and sphingosine kinase-1 (SK-1) enzymes can convert ceramides to antiapoptotic molecules, glucosylceramide, and sphingosine-1-phosphate, respectively. C8:ceramide, an important cell-permeable analogue of natural ceramides, increases intracellular ceramide levels significantly, while 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) and SK-1 inhibitor increase accumulation of ceramides by inhibiting GCS and SK-1, respectively. Chronic myelogenous leukemia (CML) is a hematological disorder resulting from generation of BCR/ABL oncogene. In this study, we examined the roles of ceramide metabolizing genes in resveratrol-induced apoptosis in K562 CML cells. There were synergistic cytotoxic and apoptotic effects of resveratrol with coadministration of C8:ceramide, PDMP, and SK-1 inhibitor. Interestingly, there were also significant increases in expression levels of LASS genes and decreases in expression levels of GCS and SK-1 in K562 cells in response to resveratrol. Our data, in total, showed for the first time that resveratrol might kill CML cells through increasing intracellular generation and accumulation of apoptotic ceramides.

A potential estrogen mimetic effect of a bis(ethyl)polyamine analogue on estrogen receptor positive MCF-7 breast cancer cells

BE-3-3-3-3 (1,15-(ethylamino)4,8,12-triazapentadecane) is a bis(ethyl)polyamine analogue under investigation as a therapeutic agent for breast cancer. Since estradiol (E(2)) is a critical regulatory molecule in the growth of breast cancer, we examined the effect of BE-3-3-3-3 on estrogen receptor α (ERα) positive MCF-7 cells in the presence and absence of E(2). In the presence of E(2), a concentration-dependent decrease in DNA synthesis was observed using [(3)H]-thymidine incorporation assay. In the absence of E(2), low concentrations (2.5-10 μM) of BE-3-3-3-3 increased [(3)H]-thymidine incorporation at 24 and 48 h. BE-3-3-3-3 induced the expression of early response genes, c-myc and c-fos, in the absence of E(2), but not in its presence, as determined by real-time quantitative polymerase chain reaction (qPCR). BE-3-3-3-3 had no significant effect on these genes in an ERα-negative cell line, MDA-MB-231. Chromatin immunoprecipitation assay demonstrated enhanced promoter occupation by either E(2) or BE-3-3-3-3 of an estrogen-responsive gene pS2/Tff1 by ERα and its co-activator, steroid receptor co-activator 3 (SRC-3). Confocal microscopy of BE-3-3-3-3-treated cells revealed membrane localization of ERα, similar to that induced by E(2). The failure of BE-3-3-3-3 to inhibit cell proliferation was associated with autophagic vacuole formation, and the induction of Beclin 1 and MAP LC3 II. These results indicate a differential effect of BE-3-3-3-3 on MCF-7 cells in the absence and presence of E(2), and suggest that pre-clinical and clinical development of polyamine analogues might require special precautions and selection of sensitive subpopulation of patients.

The anti-tumor effect of resveratrol alone or in combination with immunotherapy in a neuroblastoma model

We investigated the anti-tumor effect of peritumoral resveratrol in combination with immunotherapy in vivo in neuroblastoma-bearing mice. Subcutaneous NXS2 tumors were induced in A/J mice. On day 10, some mice received 15 mcg of intravenous immunocytokine for 5 days, mice received 20 mg of peritumoral resveratrol twice a week (starting on day 12) for a total of 5 injections, and a separate group received a combination of both regimens. Tumor progression and survival were assessed every 3-4 days. Blood and primary tumor tissue samples were collected on day 20 for Complete Blood Count and CD45 immunohistochemistry and histology, respectively. The primary tumor regressed in all mice receiving peritumoral resveratrol. Most of these mice receiving peritumoral resveratrol alone developed metastatic tumors and recurrence of the primary tumor after cessation of therapy. When resveratrol and immunocytokine regimens were combined, 61% of the mice receiving this combination therapy resolved their primary tumors and survived without developing metastatic tumors, compared to 15 and 13% receiving resveratrol or immunocytokine alone, respectively. None of the therapeutic regimes prevented lymphocyte infiltration or affected the complete blood count. Greater necrosis was observed microscopically in tumors from mice receiving the combination therapy. These results demonstrate that the combination therapy of peritumoral resveratrol plus intravenous immunocytokine provides better anti-tumor effects in this model than either therapy alone.

Resveratrol increases iodide trapping in the rat thyroid cell line FRTL-5

BACKGROUND

Resveratrol, a polyphenol found in grapes, exhibits several beneficial health effects by its antioxidant, antiinflammatory, and chemopreventive properties. The aim of the present study was to determine the effect of resveratrol on iodide trapping and efflux as well as its mode of action using FRTL-5 cells, having in mind the pivotal role of the natrium iodide symporter (NIS) in the treatment of differentiated thyroid cancers.

METHODS

Cells were treated with resveratrol for various times and doses, in the presence or absence of thyrotropin (TSH). Iodide trapping, iodide efflux, rat NIS (rNIS) protein expression, and cyclic AMP (cAMP) production were evaluated.

RESULTS

Resveratrol increased iodide trapping in a time-dependent (optimal 6 hours) and dose-dependent (100 microM) way in the presence of TSH. It showed an additive effect when concomitantly added with an optimal dose of TSH. Resveratrol (50 microM) increased (threefold) rNIS protein expression. In TSH-deprived cells, resveratrol also provoked an increase in rNIS protein (>3-fold in 6 hours) with an optimum at 40 microM. Resveratrol did not inhibit iodide efflux from FRTL-5 cells. It neither increased intracellular cAMP nor induced the arborization of living cells, two TSH-induced effects. A non-cAMP mode of action is highly suspected.

CONCLUSIONS

Resveratrol increases iodide trapping in FRTL-5 cells, increasing iodide influx and rNIS protein level even in the absence of TSH. It has an additive effect with TSH. Consequently, resveratrol could be a promising molecule for radioiodide therapy in follicular and papillary differentiated thyroid carcinoma in association with recombinant human TSH.

Resveratrol: its biologic targets and functional activity

The polyphenolic phytoalexin resveratrol (RSV) and its analogues have received tremendous attention over the past couple of decades because of a number of reports highlighting their benefits in vitro and in vivo in a variety of human disease models, including cardio- and neuroprotection, immune regulation, and cancer chemoprevention. These studies have underscored the high degree of diversity in terms of the signaling networks and cellular effector mechanisms that are affected by RSV. The activity of RSV has been linked to cell-surface receptors, membrane signaling pathways, intracellular signal-transduction machinery, nuclear receptors, gene transcription, and metabolic pathways. The promise shown by RSV has prompted heightened interest in studies aimed at translating these observations to clinical settings. In this review, we present a comprehensive account of the basic chemistry of RSV, its bioavailability, and its multiple intracellular target proteins and signaling pathways.

Resveratrol and its analogs: defense against cancer, coronary disease and neurodegenerative maladies or just a fad?

Resveratrol (3,5,4'-trihydroxy-trans-stilbene; RV), a dietary constituent found in grapes and wine, exerts a wide variety of pharmacological activities. Because the grape skins are not fermented in the production process of white wines, only red wines contain considerable amounts of this compound. RV is metabolized into sulfated and glucuronidated forms within approximately 15min of entering the bloodstream, and moderate consumption of red wine results in serum levels of RV that barely reach the micromolar concentrations. In contrast, its metabolites, which may be the active principle, circulate in serum for up to 9h. RV has been identified as an effective candidate for cancer chemoprevention due its ability to block each step in the carcinogenesis process by inhibiting several molecular targets such as kinases, cyclooxygenases, ribonucleotide reductase, and DNA polymerases. In addition, RV protects the cardiovascular system by a large number of mechanisms, including defense against ischemic-reperfusion injury, promotion of vasorelaxation, protection and maintenance of intact endothelium, anti-atherosclerotic properties, inhibition of low-density lipoprotein oxidation, and suppression of platelet aggregation, thereby strongly supporting its role in the prevention of coronary disease. Promising data within the use of RV have also been obtained regarding progressive neurodegenerative maladies such as Alzheimer's, Huntington's, and Parkinson's diseases. Because neurotoxicity is often related to mitochondrial dysfunction and may be ameliorated through the inclusion of metabolic modifiers and/or antioxidants, RV may provide an alternative (and early) intervention approach that could prevent further damage. RV induces a multitude of effects that depend on the cell type (e.g., NF-kappaB modulation in cancer cells vs. neural cells), cellular condition (normal, stressed, or malignant), and concentration (proliferative vs. growth arrest), and it can have opposing activities. RV affects whole pathways and sets of intracellular events rather than a single enzyme and, therefore, may be an effective therapy to restore homoestasis. Nonetheless, the question of whether RV or its metabolites can accumulate to bioactive levels in target organs remains to be addressed.