Multifactorial anticancer effects of digalloyl-resveratrol encompass apoptosis, cell-cycle arrest, and inhibition of lymphendothelial gap formation in vitro

Metastatic Breast Cancer, Organotropism and Therapeutics: A Review

The final stage of breast cancer involves spreading breast cancer cells to the vital organs like the brain, liver lungs and bones in the process called metastasis. Once the target organ is overtaken by the metastatic breast cancer cells, its usual function is compromised causing organ dysfunction and death. Despite the significant research on breast cancer metastasis, it's still the main culprit of breast cancer-related deaths. Exploring the complex molecular pathways associated with the initiation and progression of breast cancer metastasis could lead to the discovery of more effective ways of treating the devastating phenomenon. The present review article highlights the recent advances to understand the complexity associated with breast cancer metastases, organotropism and therapeutic advances.

Hispidulin: A promising flavonoid with diverse anti-cancer properties

In recent years, natural products have increasingly attracted more attention because of their potential anticancer activity and low intrinsic toxicity. Hispidulin is a natural flavonoid with a wide range of biological activities, including anti-inflammatory, antifungal, antiplatelet, anticonvulsant, anti-osteoporotic, and notably anticancer activities. Numerous in vivo and in vitro studies have shown that hispidulin, as a potential anticancer drug, affects cell proliferation, apoptosis, cell cycle, angiogenesis, and metastasis. Moreover, hispidulin exhibits synergistic anti-tumor effects when combined with some common clinical anticancer drugs (e.g., gemcitabine, 5-fluoroucil, sunitinib, temozolomide, and TRAIL). The combination of hispidulin and chemotherapeutic drugs reduces the efflux of chemotherapeutic drugs, enhances the chemosensitivity of cancer cells, and reverses drug resistance. Herein, we outlined the anticancer effects of hispidulin in various cancers and its intracellular molecular targets and related mechanisms of its anticancer activity. Based on the available literature, it can be established that hispidulin has significant potential to become an important complementary medicine for cancer prevention and treatment. However, more in-depth in vitro and in vivo studies should be conducted to support its translation from bench to bedside.

Molecular Complexity of Lymphovascular Invasion: The Role of Cell Migration in Breast Cancer as a Prototype

Lymphovascular invasion (LVI) is associated with poor outcome in breast cancer (BC); however, its underlying mechanisms remain ill-defined. LVI in BC develops through complex molecular pathways involving not only the interplay with the surrounding microenvironment along with endothelial cells lining the lymphovascular spaces but also changes in the malignant epithelial cells with the acquisition of more invasive and migration abilities. In this review, we focus on the key features that enable tumour cell detachment from the primary niche, their migration and interaction with the surrounding microenvironment as well as the crosstalk with the vascular endothelial cells, which eventually lead to intravasation of tumour cells and LVI. Intravascular tumour cell survival and migration, their distant site extravasation, stromal invasion and growth are part of the metastatic cascade. Cancer cell migration commences with loss of tumour cells' cohesion initiating the invasion and migration processes which are usually accompanied by the accumulation of specific cellular and molecular changes that enable tumour cells to overcome the blockades of the extracellular matrix, spread into surrounding tissues and interact with stromal cells and immune cells. Thereafter, tumour cells migrate further via interacting with lymphovascular endothelial cells to penetrate the vessel wall leading ultimately to intravasation of cancer cells. Exploring the potential factors influencing cell migration in LVI can help in understanding the underlying mechanisms of LVI to identify targeted therapy in BC.

Flavonoids Distinctly Stabilize Lymph Endothelial- or Blood Endothelial Disintegration Induced by Colon Cancer Spheroids SW620

The health effects of plant phenolics in vegetables and other food and the increasing evidence of the preventive potential of flavonoids in “Western Diseases” such as cancer, neurodegenerative diseases and others, have gained enormous interest. This prompted us to investigate the effects of 20 different flavonoids of the groups of flavones, flavonols and flavanones in 3D in vitro systems to determine their ability to inhibit the formation of circular chemorepellent induced defects (CCIDs) in monolayers of lymph- or blood-endothelial cells (LECs, BECs; respectively) by 12(S)-HETE, which is secreted by SW620 colon cancer spheroids. Several compounds reduced the spheroid-induced defects of the endothelial barriers. In the SW620/LEC model, apigenin and luteolin were most active and acacetin, nepetin, wogonin, pinocembrin, chrysin and hispidulin showed weak effects. In the SW620/BEC model acacetin, apigenin, luteolin, wogonin, hispidulin and chrysin exhibited weak activity.

Resveratrol: a review of plant sources, synthesis, stability, modification and food application

Resveratrol, a stilbene molecule belonging to the polyphenol family, is usually extracted from a great many natural plants. The technologies of preparation and extraction methods are developing rapidly. As resveratrol has many beneficial properties, it has been widely utilized in food and medicine industry. In terms of its structure, it is susceptible to degradation and can undergo chemical changes during food processing. Different studies have therefore given more attention to various aspects of resveratrol, including anti-aging, anti-oxidant, and anti-cancer activity. This review classifies the study of resveratrol, considers plant sources, synthesis, stability, common reactions, and food applications, and provides references to boost its food and medical utilization. © 2019 Society of Chemical Industry.

Structural Insight into the In Vitro Anti-Intravasative Properties of Flavonoids

We investigated the effect of 21 flavonoids in a three-dimensional in vitro system for their ability to inhibit gap formation by MCF-7 breast cancer spheroids in monolayers of lymphendothelial cells. Different representatives of the classes of flavones, flavonols, and flavanones were tested in the circular chemorepellent-induced defects (CCID)-assay. Bay11-7082, a known inhibitor of CCID formation served as the positive control. This study provides the first comparison of the potential of flavonoids to suppress features influencing the intravasation of MCF-7 breast cancer cells aggregates through the lymph endothelial barrier. The most significant effects were seen after incubation with the flavones luteolin, chrysin, and apigenin. Additional hydroxylation or methoxylation in positions 6 or 8, as expected, resulted in decreased activity. The tested flavanones remained without or low efficacy.

Chemical Composition of Scrophularia lucida and the Effects on Tumor Invasiveness in Vitro

A detannified methanolic extract of Scrophularia lucida L. attenuated the formation of cancer cell-induced circular chemorepellent induced defects (CCIDs) in the lymph endothelial cell barrier, which resemble entry ports for the intravasating tumor into the vasculature as a prerequisite for lymph node metastasis. Therefore, the composition of this extract was studied in an activity-guided approach. Since no data on the secondary metabolites of this plant were available, first phytochemical data were collected in the course of the fractionation of the extract. The study resulted in the identification of 14 substances, among them very rare iridoids, such as scrovalentinoside or koelzioside, and several flavonoids (e.g., nepitrin and homoplantaginin). One of the latter group, 2″-O-acetyl-homoplantaginin, is a new natural compound. In the most active fraction, the flavonoid hispidulin was identified as major component and the assay of the pure compound confirmed a contribution of hispidulin to the CCID-inhibitory effects of S. lucida. The activity of the two major iridoids in this assay was less compared to hispidulin.

Intravasation of SW620 colon cancer cell spheroids through the blood endothelial barrier is inhibited by clinical drugs and flavonoids in vitro

Mechanisms how colorectal cancer (CRC) cells penetrate blood micro-vessel endothelia and metastasise is poorly understood. To study blood endothelial cell (BEC) barrier breaching by CRC emboli, an in vitro assay measuring BEC-free areas underneath SW620 cell spheroids, so called "circular chemorepellent induced defects" (CCIDs, appearing in consequence of endothelial retraction), was adapted and supported by Western blotting, EIA-, EROD- and luciferase reporter assays. Inhibition of ALOX12 or NF-κB in SW620 cells or BECs, respectively, caused attenuation of CCIDs. The FDA approved drugs vinpocetine [inhibiting ALOX12-dependent 12(S)-HETE synthesis], ketotifen [inhibiting NF-κB], carbamazepine and fenofibrate [inhibiting 12(S)-HETE and NF-κB] significantly attenuated CCID formation at low μM concentrations. In the 5-FU-resistant SW620-R/BEC model guanfacine, nifedipine and proadifen inhibited CCIDs stronger than in the naïve SW620/BEC model. This indicated that in SW620-R cells formerly silent (yet unidentified) genes became expressed and targetable by these drugs in course of resistance acquisition. Fenofibrate, and the flavonoids hispidulin and apigenin, which are present in medicinal plants, spices, herbs and fruits, attenuated CCID formation in both, naïve- and resistant models. As FDA-approved drugs and food-flavonoids inhibited established and acquired intravasative pathways and attenuated BEC barrier-breaching in vitro, this warrants testing of these compounds in CRC models in vivo.

A robust in vitro model for trans-lymphatic endothelial migration

Trans-endothelial migration (TEM) is essential for leukocyte circulation. While much is known about trans-blood endothelial migration, far less is known about trans-lymphatic endothelial migration. We established an in vitro system to evaluate lymphatic TEM for various cell types across primary mouse and human lymphatic endothelial cells (LEC), and validated the model for the murine LEC cell line SVEC4-10. T cells exhibited enhanced unidirectional migration from the basal (abluminal) to the apical (luminal) surface across LEC, whereas for blood endothelial cells (BEC) they migrated similarly in both directions. This preferential, vectorial migration was chemotactic toward many different chemoattractants and dose-dependent. Stromal protein fibers, interstitial type fluid flow, distribution of chemokines in the stromal layer, and inflammatory cytokines influenced LEC phenotype and leukocyte TEM. Activated and memory CD4 T cells, macrophages, and dendritic cell (DC) showed chemoattractantΔdriven vectorial migration, while CD8 T cell migration across LEC was not. The system was further validated for studying cancer cell transmigration across lymphatic endothelium. This model for lymphatic TEM for various migrating and endothelial cell types possesses the capacity to be high-throughput, highly reproducible and integrate the complexities of lymphatic biology, stromal variability, chemoattractant distribution, and fluid flow.

Fenofibrate inhibits tumour intravasation by several independent mechanisms in a 3-dimensional co-culture model

Lymph node metastasis of breast cancer is a clinical marker of poor prognosis. Yet, there exist no therapies targeting mechanisms of intravasation into lymphatics. Herein we report on an effect of the antidyslipidemic drug fenofibrate with vasoprotective activity, which attenuates breast cancer intravasation in vitro, and describe the potential mechanisms. To measure intravasation in a 3-dimensional co-culture model MDA-MB231 and MCF-7 breast cancer spheroids were placed on immortalised lymphendothelial cell (LEC) monolayers. This provokes the formation of circular chemorepellent induced defects (CCIDs) in the LEC barrier resembling entry ports for the intravasating tumour. Furthermore, the expression of adhesion molecules ICAM-1, CD31 and FAK was investigated in LECs by western blotting as well as cell-cell adhesion and NF-κB activity by respective assays. In MDA-MB231 cells the activity of CYP1A1 was measured by EROD assay. Fenofibrate inhibited CCID formation in the MDA-MB231/LEC- and MCF-7/LEC models and the activity of NF-κB, which in turn downregulated ICAM-1 in LECs and the adhesion of cancer cells to LECs. Furthermore, CD31 and the activity of FAK were inhibited. In MDA-MB231 cells, fenofibrate attenuated CYP1A1 activity. Combinations with other FDA-approved drugs, which reportedly inhibit different ion channels, attenuated CCID formation additively or synergistically. In summary, fenofibrate inhibited NF-κB and ICAM-1, and inactivated FAK, thereby attenuating tumour intravasation in vitro. A combination with other FDA-approved drugs further improved this effect. Our new concept may lead to a novel therapy for cancer patients.

Colon cancer cell-derived 12(S)-HETE induces the retraction of cancer-associated fibroblast via MLC2, RHO/ROCK and Ca2+ signalling

Retraction of mesenchymal stromal cells supports the invasion of colorectal cancer cells (CRC) into the adjacent compartment. CRC-secreted 12(S)-HETE enhances the retraction of cancer-associated fibroblasts (CAFs) and therefore, 12(S)-HETE may enforce invasivity of CRC. Understanding the mechanisms of metastatic CRC is crucial for successful intervention. Therefore, we studied pro-invasive contributions of stromal cells in physiologically relevant three-dimensional in vitro assays consisting of CRC spheroids, CAFs, extracellular matrix and endothelial cells, as well as in reductionist models. In order to elucidate how CAFs support CRC invasion, tumour spheroid-induced CAF retraction and free intracellular Ca²⁺ levels were measured and pharmacological- or siRNA-based inhibition of selected signalling cascades was performed. CRC spheroids caused the retraction of CAFs, generating entry gates in the adjacent surrogate stroma. The responsible trigger factor 12(S)-HETE provoked a signal, which was transduced by PLC, IP3, free intracellular Ca²⁺, Ca²⁺-calmodulin-kinase-II, RHO/ROCK and MYLK which led to the activation of myosin light chain 2, and subsequent CAF mobility. RHO activity was observed downstream as well as upstream of Ca²⁺ release. Thus, Ca²⁺ signalling served as central signal amplifier. Treatment with the FDA-approved drugs carbamazepine, cinnarizine, nifedipine and bepridil HCl, which reportedly interfere with cellular calcium availability, inhibited CAF-retraction. The elucidation of signalling pathways and identification of approved inhibitory drugs warrant development of intervention strategies targeting tumour–stroma interaction.

NF-κB contributes to MMP1 expression in breast cancer spheroids causing paracrine PAR1 activation and disintegrations in the lymph endothelial barrier in vitro

RELA, RELB, CREL, NFKB1 and NFKB2, and the upstream regulators NEMO and NIK were knocked-down in lymph endothelial cells (LECs) and in MDA-MB231 breast cancer spheroids to study the contribution of NF-κB in vascular barrier breaching. Suppression of RELA, NFKB1 and NEMO inhibited “circular chemo-repellent induced defects” (CCIDs), which form when cancer cells cross the lymphatic vasculature, by ~20–30%. Suppression of RELB, NFKB2 and NIK inhibited CCIDs by only ~10–15%. In MDA-MB231 cells RELA and NFKB1 constituted MMP1 expression, which caused the activation of PAR1 in adjacent LECs. The knock-down of MMP1 in MDA-MB231 spheroids and pharmacological inhibition of PAR1 in LECs inhibited CCID formation by ~30%. Intracellular Ca²⁺ release in LECs, which was induced by recombinant MMP1, was suppressed by the PAR1 inhibitor SCH79797, thereby confirming a functional intercellular axis: RELA/NFKB1 – MMP1 (MDA-MB231) – PAR1 (LEC). Recombinant MMP1 induced PAR1-dependent phosphorylation of MLC2 and FAK in LECs, which is indicative for their activity and for directional cell migration such as observed during CCID formation. The combined knock-down of the NF-κB pathways in LECs and MDA-MB231 spheroids inhibited CCIDs significantly stronger than knock-down in either cell type alone. Also the knock-down of ICAM-1 in LECs (a NF-κB endpoint with relevance for CCID formation) and knock-down of MMP1 in MDA-MB231 augmented CCID inhibition. This evidences that in both cell types NF-κB significantly and independently contributes to tumour-mediated breaching of the lymphatic barrier. Hence, inflamed tumour tissue and/or vasculature pose an additional threat to cancer progression.

Colorectal cancer cell-derived microRNA200 modulates the resistance of adjacent blood endothelial barriers in vitro

Since cancer cells, when grown as spheroids, display drug sensitivity and radiation resistance patterns such as seen in vivo we recently established a three‑dimensional (3D) in vitro model recapitulating colorectal cancer (CRC)-triggered lymphatic endothelial cell (LEC)‑barrier breaching to study mechanisms of intra‑/extravasation. CRC metastasizes not only through lymphatics but also through blood vessels and here we extend the 3D model to the interaction of blood endothelial cells (BECs) with naïve and 5‑fluorouracil (5‑FU)‑resistant CRC CCL227 cells. The 3D model enabled quantifying effects of tumour‑derived microRNA200 (miR200) miR200a, miR200b, miR200c, miR141 and miR429 regarding the induction of so-called 'circular chemorepellent‑induced defects' (CCIDs) within the BEC‑barrier, which resemble gates for tumour transmigration. For this, miR200 precursors were individually transfected and furthermore, the modulation of ZEB family expression was analysed by western blotting. miR200c, miR141 and miR429, which are contained in exosomes from naïve CCL227 cells, downregulated the expression of ZEB2, SNAI and TWIST in BECs. The exosomes of 5‑FU‑resistant CCL227‑RH cells, which are devoid of miR200, accelerated CCID formation in BEC monolayers as compared to exosomes from naïve CCL227 cells. This confirmed the reported role of ZEB2 and SNAI in CRC metastasis and highlighted the active contribution of the stroma in the metastatic process. CCL227 spheroids affected the integrity of BEC and LEC barriers alike, which was in agreement with the observation that CRC metastasizes via blood stream (into the liver) as well as via lymphatics (into lymph nodes and lungs). This further validated the CRC/LEC and CRC/BEC in vitro model to study mechanisms of CRC spreading through vascular systems. Treatment of CCL227‑RH cells with the HDAC inhibitors mocetinostat and sulforaphane reduced CCID formation to the level triggered by naïve CCL227 spheroids, however, without significantly influencing miR200 expression in CCL227-RH cells.

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.

A eudesmane-type sesquiterpene isolated from Pluchea odorata (L.) Cass. combats three hallmarks of cancer cells: Unrestricted proliferation, escape from apoptosis and early metastatic outgrowth in vitro

Pluchea odorata is ethno pharmaceutically used to treat inflammation-associated disorders. The dichloromethane extract (DME) was tested in the carrageenan-induced rat paw oedema assay investigating its effect on inflammation that was inhibited by 37%. Also an in vitro anti-neoplastic potential was reported. However, rather limited information about the bio-activity of purified compounds and their cellular mechanisms are available. Therefore, two of the most abundant eudesmanes in P. odorata were isolated and their anti-neoplastic and anti-intravasative activities were studied. HL-60 cells were treated with P. odorata compounds and metabolic activity, cell number reduction, cell cycle progression and apoptosis induction were correlated with relevant protein expression. Tumour cell intravasation through lymph endothelial monolayers was measured and potential causal mechanisms were analyzed by Western blotting. Compound PO-1 decreased the metabolic activity of HL-60 cells (IC50 = 8.9 μM after 72 h) and 10 μM PO-1 induced apoptosis, while PO-2 showed just weak anti-neoplastic activities at concentrations beyond 100 μM. PO-1 arrested the cell cycle in G1 and this correlated with induction of JunB expression. Independent of this mechanism 25 μM PO-1 decreased MCF-7 spheroid intravasation through the lymph endothelial barrier. Hence, PO-1 inhibits an early step of metastasis, impairs unrestricted proliferation and induces apoptosis at low micromolar concentrations. These results warrant further testing in vivo to challenge the potential of PO-1 as novel lead compound.

Loss of miR-200 family in 5-fluorouracil resistant colon cancer drives lymphendothelial invasiveness in vitro

Invasive colorectal cancer is associated with poor prognosis requiring treatment with systemic chemotherapies usually including 5-fluorouracil. A consequence of prolonged treatment is the acquisition of resistance eventually resulting in the recurrence of highly metastatic cancer cells. To address the relationship between drug resistance and increased lymphatic metastatic potential, we used a 3D co-culture model of colon tumour cell spheroids of parent CCL227 cells and subclones with gradually increasing resistance against 5-fluorouracil. From each investigated cell line, homogeneous tumour spheroids were generated in the presence of methylcellulose yielding emboli of ∼700 µm diameter. When invasive, tumour spheroids disrupt the continuous lymphendothelial cell (LEC) layer and generate a 'circular chemorepellent-induced defect' (CCID), reminiscent of the entry gates through which tumour emboli intravasate lymphatic vasculature. Here we provide evidence that increasingly chemoresistant colon cancer spheroids were strongly associated with enhanced intravasative properties. In naïve CCL227 spheroids, miR-200 family members were released into exosomes thereby repressing the epithelial to mesenchymal transition-regulating transcription factors ZEB1 and SLUG in LEC. As a consequence of attenuated plasticity and migration of LEC, CCID formation was impaired. Loss of exosomal transferred miR-200c in resistant colon cells rendered LEC more susceptible to pro-migratory signals that were generated and directly transmitted by colon cancer spheroids. This observation indicates a common molecular axis in colon cancer and LEC where miR-200 family members act as regulators of ZEB proteins. The data support the notion that horizontal miR-200 signalling prevents the permeation of cells into adjacent epithelia and contributes to organ integrity.

Phthalocyanine derivatives possessing 2-(morpholin-4-yl)ethoxy groups as potential agents for photodynamic therapy

Three 2-(morpholin-4-yl)ethoxy substituted phthalocyanines were synthesized and characterized. Phthalocyanine derivatives revealed moderate to high quantum yields of singlet oxygen production depending on the solvent applied (e.g., in DMF ranging from 0.25 to 0.53). Their photosensitizing potential for photodynamic therapy was investigated in an in vitro model using cancer cell lines. Biological test results were found particularly encouraging for the zinc(II) phthalocyanine derivative possessing two 2-(morpholin-4-yl)ethoxy substituents in nonperipheral positions. Cells irradiated for 20 min at 2 mW/cm(2) revealed the lowest IC50 value at 0.25 μM for prostate cell line (PC3), whereas 1.47 μM was observed for human malignant melanoma (A375) cells. The cytotoxic activity in nonirradiated cells of novel phthalocyanine was found to be very low. Moreover, the cellular uptake, localization, cell cycle, apoptosis through an ELISA assay, and immunochemistry method were investigated in LNCaP cells. Our results showed that the tested photosensitizer possesses very interesting biological activity, depending on experimental conditions.

Anti-tumor properties of cis-resveratrol methylated analogs in metastatic mouse melanoma cells

Resveratrol (E-3,5,4'-trihydroxystilbene) is a polyphenol found in red wine that has been shown to have multiple anti-cancer properties. Although cis-(Z)- and trans-(E)-isomers of resveratrol occur in nature, the cis form is not biologically active. However, methylation at key positions of the cis form results in more potent anti-cancer properties. This study determined that synthetic cis-polymethoxystilbenes (methylated analogs of cis-resveratrol) inhibited cancer-related phenotypes of metastatic B16 F10 and non-metastatic B16 F1 mouse melanoma cells. In contrast with cis- or trans-resveratrol and trans-polymethoxystilbene which were ineffective at 10 μM, cis-polymethoxystilbenes inhibited motility and proliferation of melanoma cells with low micromolar specificity (IC50 < 10 μM). Inhibitory effects by cis-polymethoxystilbenes were significantly stronger with B16 F10 cells and were accompanied by decreased expression of β-tubulin and pleckstrin homology domain-interacting protein, a marker of metastatic B16 cells. Thus, cis-polymethoxystilbenes have potential as chemotherapeutic agents for metastatic melanoma.

Lobatin B inhibits NPM/ALK and NF-κB attenuating anaplastic-large-cell-lymphomagenesis and lymphendothelial tumour intravasation

An apolar extract of the traditional medicinal plant Neurolaena lobata inhibited the expression of the NPM/ALK chimera, which is causal for the majority of anaplastic large cell lymphomas (ALCLs). Therefore, an active principle of the extract, the furanoheliangolide sesquiterpene lactone lobatin B, was isolated and tested regarding the inhibition of ALCL expansion and tumour cell intravasation through the lymphendothelium. ALCL cell lines, HL-60 cells and PBMCs were treated with plant compounds and the ALK inhibitor TAE-684 to measure mitochondrial activity, proliferation and cell cycle progression and to correlate the results with protein- and mRNA-expression of selected gene products. Several endpoints indicative for cell death were analysed after lobatin B treatment. Tumour cell intravasation through lymphendothelial monolayers was measured and potential causal mechanisms were investigated analysing NF-κB- and cytochrome P450 activity, and 12(S)-HETE production. Lobatin B inhibited the expression of NPM/ALK, JunB and PDGF-Rβ, and attenuated proliferation of ALCL cells by arresting them in late M phase. Mitochondrial activity remained largely unaffected upon lobatin B treatment. Nevertheless, caspase 3 became activated in ALCL cells. Also HL-60 cell proliferation was attenuated whereas PBMCs of healthy donors were not affected by lobatin B. Additionally, tumour cell intravasation, which partly depends on NF-κB, was significantly suppressed by lobatin B most likely due to its NF-κB-inhibitory property. Lobatin B, which was isolated from a plant used in ethnomedicine, targets malignant cells by at least two properties: I) inhibition of NPM/ALK, thereby providing high specificity in combating this most prevalent fusion protein occurring in ALCL; II) inhibition of NF-κB, thereby not affecting normal cells with low constitutive NF-κB activity. This property also inhibits tumour cell intravasation into the lymphatic system and may provide an option to manage this early step of metastatic progression.

Antiproliferative and uncoupling effects of delocalized, lipophilic, cationic gallic acid derivatives on cancer cell lines. Validation in vivo in singenic mice

Tumor cells principally exhibit increased mitochondrial transmembrane potential (ΔΨ(m)) and altered metabolic pathways. The therapeutic targeting and delivery of anticancer drugs to the mitochondria might improve treatment efficacy. Gallic acid exhibits a variety of biological activities, and its ester derivatives can induce mitochondrial dysfunction. Four alkyl gallate triphenylphosphonium lipophilic cations were synthesized, each differing in the size of the linker chain at the cationic moiety. These derivatives were selectively cytotoxic toward tumor cells. The better compound (TPP(+)C10) contained 10 carbon atoms within the linker chain and exhibited an IC50 value of approximately 0.4-1.6 μM for tumor cells and a selectivity index of approximately 17-fold for tumor compared with normal cells. Consequently, its antiproliferative effect was also assessed in vivo. The oxygen consumption rate and NAD(P)H oxidation levels increased in the tumor cell lines (uncoupling effect), resulting in a ΔΨ(m) decrease and a consequent decrease in intracellular ATP levels. Moreover, TPP(+)C10 significantly inhibited the growth of TA3/Ha tumors in mice. According to these results, the antineoplastic activity and safety of TPP(+)C10 warrant further comprehensive evaluation.

Inhibition of tumour spheroid-induced prometastatic intravasation gates in the lymph endothelial cell barrier by carbamazepine: drug testing in a 3D model

Metastatic breast cancer is linked to an undesired prognosis. One early and crucial metastatic step is the interaction of cancer emboli with adjacent stroma or endothelial cells, and understanding the mechanisms of this interaction provides the basis to define new targets as well as drugs for therapy and disease management. A three-dimensional (3D) co-culture model allowing the examination of lymphogenic dissemination of breast cancer cells was recently developed which facilitates not only the study of metastatic processes but also the testing of therapeutic concepts. This 3D setting consists of MCF-7 breast cancer cell spheroids (representing a ductal and hormone-dependent subtype) and of hTERT-immortalised lymph endothelial cell (LEC; derived from foreskin) monolayers. Tumour spheroids repel the continuous LEC layer, thereby generating "circular chemorepellent-induced defects" (CCIDs) that are reminiscent to the entry gates through which tumour emboli intravasate lymphatics. We found that the ion channel blocker carbamazepine (which is clinically used to treat epilepsy, schizophrenia and other neurological disorders) inhibited CCID formation significantly. This effect correlated with the inhibition of the activities of NF-κB, which contributes to cell motility, and with the inactivation of the mobility proteins MLC2, MYPT1 and FAK which are necessary for LEC migration. NF-κB activity and cell movement are prerequisites of CCID formation. On the other hand, the expression of the motility protein paxillin and of the NF-κB-dependent adhesion mediator ICAM-1 was unchanged. Also the activity of ALOX12 was unaffected. ALOX12 is the main enzyme synthesising 12(S)-HETE, which then triggers CCID formation. The relevance of the inhibition of CYP1A1, which is also involved in the generation of mid-chain HETEs such as 12(S)-HETE, by carbamazepine remains to be established, because the constitutive level of 12(S)-HETE did not change upon carbamazepine treatment. Nevertheless, the effect of carbamazepine on the inhibition of CCID formation as an early step of breast cancer metastasis was significant and substantial (~30 %) and achieved at concentrations that are found in the plasma of carbamazepine-treated adults (40-60 μM). The fact that carbamazepine is a drug approved by the US Food and Drug Administration facilitates a "from-bench-to-bedside" perspective. Therefore, the here presented data should undergo scrutiny in vivo.

Digalloylresveratrol, a novel resveratrol analog inhibits the growth of human pancreatic cancer cells

Digalloylresveratrol (DIG) is a recently synthesized substance aimed to combine the effects of the natural polyphenolic compounds gallic acid and resveratrol, which both are excellent free radical scavengers with anticancer activity. In this study, we investigated the effects of DIG in the human AsPC-1 and BxPC-3 pancreatic adenocarcinoma cell lines. Treatment with DIG dose-dependently attenuated cells in the S phase of the cell cycle and led to a significant depletion of the dATP pool in AsPC-1 cells. The incorporation of (14)C-cytidine into nascent DNA of tumor cells was significantly inhibited at all DIG concentrations due to inhibition of ribonucleotide reductase, a key enzyme of DNA synthesis in tumor cells. Furthermore, Erk1/2 became inactivated and moderated p38 phosphorylation reflecting increased replication stress. DIG also activated ATM and Chk2, and induced the phosphorylation and proteasomal degradation of the proto-oncogene Cdc25A, which contributed to cell cycle attenuation. Taken together, DIG is an excellent free radical scavenger, strongly inhibits RR in situ activity, cell cycle progression, and colony formation in AsPC-1 and BxPC-3 cells thus warranting further investigations.

In vitro inhibition of breast cancer spheroid-induced lymphendothelial defects resembling intravasation into the lymphatic vasculature by acetohexamide, isoxsuprine, nifedipin and proadifen

Background:

As metastasis is the prime cause of death from malignancies, there is vibrant interest to discover options for the management of the different mechanistic steps of tumour spreading. Some approved pharmaceuticals exhibit activities against diseases they have not been developed for. In order to discover such activities that might attenuate lymph node metastasis, we investigated 225 drugs, which are approved by the US Food and Drug Administration.

Methods:

A three-dimensional cell co-culture assay was utilised measuring tumour cell-induced disintegrations of the lymphendothelial wall through which tumour emboli can intravasate as a limiting step in lymph node metastasis of ductal breast cancer. The disintegrated areas in the lymphendothelial cell (LEC) monolayers were induced by 12(S)-HETE, which is secreted by MCF-7 tumour cell spheroids, and are called ‘circular chemorepellent induced defects' (CCIDs). The putative mechanisms by which active drugs prevented the formation of entry gates were investigated by western blotting, NF-κB activity assay and by the determination of 12(S)-HETE synthesis.

Results:

Acetohexamide, nifedipin, isoxsuprine and proadifen dose dependently inhibited the formation of CCIDs in LEC monolayers and inhibited markers of epithelial-to-mesenchymal-transition and migration. The migration of LECs is a prerequisite of CCID formation, and these drugs either repressed paxillin levels or the activities of myosin light chain 2, or myosin-binding subunit of myosin phosphatase. Isoxsuprine inhibited all three migration markers, and isoxsuprine and acetohexamide suppressed the synthesis of 12(S)-HETE, whereas proadifen and nifedipin inhibited NF-κB activation. Both the signalling pathways independently cause CCID formation.

Conclusion:

The targeting of different mechanisms was most likely the reason for synergistic effects of different drug combinations on the inhibition of CCID formation. Furthermore, the treatment with drug combinations allowed also a several-fold reduction in drug concentrations. These results encourage further screening of approved drugs and their in vivo testing.

The dichloromethane extract of the ethnomedicinal plant Neurolaena lobata inhibits NPM/ALK expression which is causal for anaplastic large cell lymphomagenesis

The present study investigates extracts of Neuolaena lobata, an anti-protozoan ethnomedicinal plant of the Maya, regarding its anti-neoplastic properties. Firstly, extracts of increasing polarity were tested in HL-60 cells analyzing inhibition of cell proliferation and apoptosis induction. Secondly, the most active extract was further tested in anaplastic large cell lymphoma (ALCL) cell lines of human and mouse origin. The dichloromethane extract inhibited proliferation of HL-60, human and mouse ALCL cells with an IC50 of ~2.5, 3.7 and 2.4 µg/ml, respectively and arrested cells in the G2/M phase. The extract induced the checkpoint kinases Chk1 and Chk2 and perturbed the orchestrated expression of the Cdc25 family of cell cycle phosphatases which was paralleled by the activation of p53, p21 and downregulation of c-Myc. Importantly, the expression of NPM/ALK and its effector JunB were drastically decreased, which correlated with the activation of caspase 3. Subsequently also platelet derived growth factor receptor β was downregulated, which was recently shown to be transcriptionally controlled by JunB synergizing with ALK in ALCL development. We show that a traditional healing plant extract downregulates various oncogenes, induces tumor suppressors, inhibits cell proliferation and triggers apoptosis of malignant cells. The discovery of the 'Active Principle(s)' is warranted.

Jolkinolide B induces apoptosis in MCF-7 cells through inhibition of the PI3K/Akt/mTOR signaling pathway

The aim of this study was to explore the molecular mechanisms of jolkinolide B (JB), which is extracted from the root of Euphorbia fischeriana Steud. In this study, we found that JB, a diterpenoid from the traditional Chinese medicinal herb, strongly inhibited the PI3K/Akt/mTOR signaling pathway. Furthermore, we evaluated the effects of JB on the proliferation and apoptosis of MCF-7 human breast cancer cells. Our results showed significant induction of apoptosis in MCF-7 cells incubated with JB. The viability of the MCF-7 cells was assessed by MTT assay. Flow cytometry was used to detect apoptosis and cell cycle analysis. Transmission electron microscopy (TEM) analysis was used to observe cell morphology. MCF-7 cells were subcutaneously inoculated into nude mice to study the in vivo antitumor effects of JB. The growth of MCF-7 cells was inhibited and arrested in the S phase by JB. The data showed significantly decreased tumor volume and weight in nude mice inoculated with MCF-7 cells. In addition, treatment with JB was able to induce downregulation of cyclinD1, cyclinE, mTOR, p-PI3K and p-Akt, and upregulation of PTEN and p-eIF4E. Collectively, JB-induced apoptosis of MCF-7 cells occurs through the PI3K/Akt/mTOR signaling pathway. Furthermore, the PI3K/Akt signaling cascade plays a role in the induction of apoptosis in JB-treated cells. These observations suggest that JB may have therapeutic applications in the treatment of cancer.

Bay11-7082 inhibits the disintegration of the lymphendothelial barrier triggered by MCF-7 breast cancer spheroids; the role of ICAM-1 and adhesion

Background:

Many cancers spread through lymphatic routes, and mechanistic insights of tumour intravasation into the lymphatic vasculature and targets for intervention are limited. The major emphasis of research focuses currently on the molecular biology of tumour cells, while still little is known regarding the contribution of lymphatics.

Methods:

Breast cancer cell spheroids attached to lymphendothelial cell (LEC) monolayers were used to investigate the process of intravasation by measuring the areas of ‘circular chemorepellent-induced defects' (CCID), which can be considered as entry gates for bulky tumour intravasation. Aspects of tumour cell intravasation were furthermore studied by adhesion assay, and siRNA-mediated knockdown of intracellular adhesion molecule-1 (ICAM-1). Replacing cancer spheroids with the CCID-triggering compound 12(S)-hydroxyeicosatetraenoic acid (HETE) facilitated western blot analyses of Bay11-7082- and baicalein-treated LECs.

Results:

Binding of LECs to MCF-7 spheroids, which is a prerequisite for CCID formation, was mediated by ICAM-1 expression, and this depended on NF-κB and correlated with the expression of the prometastatic factor S100A4. Simultaneous inhibition of NF-κB with Bay11-7082 and of arachidonate lipoxygenase (ALOX)-15 with baicalein prevented CCID formation additively.

Conclusion:

Two mechanisms contribute to CCID formation: ALOX15 via the generation of 12(S)-HETE by MCF-7 cells, which induces directional migration of LECs, and ICAM-1 in LECs under control of NF-κB, which facilitates adhesion of MCF-7 cells to LECs.

Molecular networks that regulate cancer metastasis

Tumor metastases are responsible for approximately 90% of all cancer-related deaths. Although many patients can be cured, in the US and UK, cancer still causes 730,000 deaths every year, and it is second only to cardiovascular disease as a cause of death. The functional roles of many critical players involved in metastasis have been delineated in great detail in recent years, due to the draft of the human genome and to many associated discoveries. Here, we address several genetic events and critical factors that define the metastatic phenotype acquired during tumorigenesis. This involves molecular networks that promote local cancer-cell invasion, single-cell invasion, formation of the metastatic microenvironment of primary tumors, intravasation, lymphogenic metastasis, extravasation, and metastatic outgrowth. Altogether, these functional networks of molecules contribute to the development of a selective environment that promotes the seeding and malignant progression of tumorigenic cells in distant organs. We include here candidate target proteins and signaling pathways that are now under clinical investigation. Although many of these trials are still ongoing, they provide the basis for the development of new aspects in the treatment of metastatic cancers, which involves inhibition of these proteins and their molecular networks.

Combination effects of digalloylresveratrol with arabinofuranosylcytosine and difluorodeoxycytidine in human leukemia and pancreatic cancer cells

Digalloylresveratrol (DIG) is a newly synthesized agent aimed to combine the biological effects of the natural compounds, gallic acid and resveratrol, which both are free radical scavengers exhibiting anticancer activity. In this study, we investigated the effects of DIG on the growth of human HL-60 leukemia cells and on the colony formation of human BxPC-3 and PANC-1 pancreatic cancer cells. DIG was applied alone and in combination with arabinofuranosylcytosine (Ara-C) or difluorodeoxycytidine (dFdC), depending on the cell line employed. All IC(50) values observed were in the low micromolar range rendering DIG a promising antitumor compound in vitro. Considering the combination experiments, DIG yielded additive effects with Ara-C in HL-60 cells and-to a lesser extent-with dFdC in BxPC-3 and PANC-1 cells. Owing to our results, DIG may be further investigated in vitro and in animals.

Gallic acid inhibits migration and invasion in human osteosarcoma U-2 OS cells through suppressing the matrix metalloproteinase-2/-9, protein kinase B (PKB) and PKC signaling pathways

Advanced cancer is a multifactorial disease which complicates treatment if the cancer cells have metastasized calling for the targeting of multiple cellular pathways. Gallic acid (GA) is known to possess multiple pharmacological activity including antitumor effects. This study investigated the mechanisms for the anticancer properties of GA on migration and invasion of human osteosarcoma U-2 OS cells. The migration and invasion in U-2 OS cells were determined by a Boyden chamber transwell assay. The expression levels and activities of MMP-2 and MMP-9 were measured by Western blotting, real-time PCR and gelatin zymography assays. All examined proteins levels from Western blotting indicated that GA decreased the protein levels of GRB2, PI3K, AKT/PKB, PKC, p38, ERK1/2, JNK, NF-κB p65 in U-2 OS cells. GA also inhibited the activities of AKT, IKK and PKC by in vitro kinase assay. GA suppressed the migration and invasive ability of U-2 OS cells, and it decreased MMP-2 and MMP-9 protein and mRNA levels and secreted enzyme activities in vitro. These results suggest that potential signaling pathways of GA-inhibited migration and invasion in U-2 OS cells may be due to down-regulation of PKC, inhibition of mitogen-activated protein kinase (MAPK) and PI3K/AKT, resulting in inhibition of MMP-2 and MMP-9 expressions.

Mitochondrial effects of plant-made compounds

SIGNIFICANCE

Plants produce many small molecules with biomedical potential. Their absorption from foods, metabolism, their effects on physiological and pathological processes, and the mechanisms of action are intensely investigated. Many are known to affect multiple cellular functions. Mitochondria are coming to be recognized as a major target for these compounds, especially redox-active ones, but the mechanisms involved still need clarification. At the same time, frontline research is uncovering the importance of processes involving these organelles for the cell and for an array of physiological and pathological processes. We review the major functions and possible dysfunctions of mitochondria, identify signaling pathways through which plant-derived molecules have an impact, and show how this may be relevant for major pathologies.

RECENT ADVANCES

Antioxidant, protective effects may arise as a reaction to a low-level pro-oxidant activity, largely taking place at mitochondria. Some plant-derived molecules can activate AMP-dependent kinase, with a consequent upregulation of mitochondrial biogenesis and a potential favorable impact on aging, pathologies like diabetes and neurodegeneration, and on ischemic damage.

CRITICAL ISSUES

The extrapolation of in vitro results and the verification of paradigms in vivo is a key issue for current research on both plant-derived compounds and mitochondria. The low bioavailability of many of these molecules poses a problem for both the study of their activities and their utilization.

FUTURE DIRECTIONS

The further clarification of the role of mitochondria in the activities of plant dietary compounds and their metabolites, mitochondrial targeting, the development of analogs and pro-drugs are all topics for promising research.

NF-κB mediates the 12(S)-HETE-induced endothelial to mesenchymal transition of lymphendothelial cells during the intravasation of breast carcinoma cells

Background:

The intravasation of breast cancer into the lymphendothelium is an early step of metastasis. Little is known about the mechanisms of bulky cancer invasion into lymph ducts.

Methods:

To particularly address this issue, we developed a 3-dimensional co-culture model involving MCF-7 breast cancer cell spheroids and telomerase-immortalised human lymphendothelial cell (LEC) monolayers, which resembles intravasation in vivo and correlated the malignant phenotype with specific protein expression of LECs.

Results:

We show that tumour spheroids generate ‘circular chemorepellent-induced defects’ (CCID) in LEC monolayers through retraction of LECs, which was induced by 12(S)-hydroxyeicosatetraenoic acid (HETE) secreted by MCF-7 spheroids. This 12(S)-HETE-regulated retraction of LECs during intravasation particularly allowed us to investigate the key regulators involved in the motility and plasticity of LECs. In all, 12(S)-HETE induced pro-metastatic protein expression patterns and showed NF-κB-dependent up-regulation of the mesenchymal marker protein S100A4 and of transcriptional repressor ZEB1 concomittant with down-regulation of the endothelial adherence junction component VE-cadherin. This was in accordance with ∼50% attenuation of CCID formation by treatment of cells with 10 μM Bay11-7082. Notably, 12(S)-HETE-induced VE-cadherin repression was regulated by either NF-κB or by ZEB1 since ZEB1 siRNA knockdown abrogated not only 12(S)-HETE-mediated VE-cadherin repression but inhibited VE-cadherin expression in general.

Interpretation:

These data suggest an endothelial to mesenchymal transition-like process of LECs, which induces single cell motility during endothelial transmigration of breast carcinoma cells. In conclusion, this study demonstrates that the 12(S)-HETE-induced intravasation of MCF-7 spheroids through LECs require an NF-κB-dependent process of LECs triggering the disintegration of cell–cell contacts, migration, and the generation of CCID.

Finding more active antioxidants and cancer chemoprevention agents by elongating the conjugated links of resveratrol

Resveratrol is the subject of intense research as a natural antioxidant and cancer chemopreventive agent. There has been a great deal of interest and excitement in understanding its action mechanism and developing analogs with antioxidant and cancer chemoprevention activities superior to that of the parent compound in the past decade. This work delineates that elongation of the conjugated links is an important strategy to improve the antioxidant activity of resveratrol analogs, including hydrogen atom- or electron-donating ability in homogeneous solutions and antihemolysis activity in heterogeneous media. More importantly, C3, a triene bearing 4,4'-dihydroxy groups, surfaced as an important lead compound displaying remarkably increased antioxidant, cytotoxic, and apoptosis-inducing activities compared with resveratrol.

Initial steps of metastasis: cell invasion and endothelial transmigration

Metastasis is the leading cause of cancer mortality. The metastatic cascade represents a multi-step process which includes local tumor cell invasion, entry into the vasculature followed by the exit of carcinoma cells from the circulation and colonization at the distal sites. At the earliest stage of successful cancer cell dissemination, the primary cancer adapts the secondary site of tumor colonization involving the tumor–stroma crosstalk. The migration and plasticity of cancer cells as well as the surrounding environment such as stromal and endothelial cells are mandatory. Consequently, the mechanisms of cell movement are of utmost relevance for targeted intervention of which three different types have been reported. Tumor cells can migrate either collectively, in a mesenchymal or in an amoeboid type of movement and intravasate the blood or lymph vasculature. Intravasation by the interaction of tumor cells with the vascular endothelium is mechanistically poorly understood. Changes in the epithelial plasticity enable carcinoma cells to switch between these types of motility. The types of migration may change depending on the intervention thereby increasing the velocity and aggressiveness of invading cancer cells. Interference with collective or mesenchymal cell invasion by targeting integrin expression or metalloproteinase activity, respectively, resulted in an amoeboid cell phenotype as the ultimate exit strategy of cancer cells. There are little mechanistic details reported in vivo showing that the amoeboid behavior can be either reversed or efficiently inhibited. Future concepts of metastasis intervention must simultaneously address the collective, mesenchymal and amoeboid mechanisms of cell invasion in order to advance in anti-metastatic strategies as these different types of movement can coexist and cooperate. Beyond the targeting of cell movements, the adhesion of cancer cells to the stroma in heterotypic circulating tumor cell emboli is of paramount relevance for anti-metastatic therapy.

Lipoxygenase mediates invasion of intrametastatic lymphatic vessels and propagates lymph node metastasis of human mammary carcinoma xenografts in mouse

In individuals with mammary carcinoma, the most relevant prognostic predictor of distant organ metastasis and clinical outcome is the status of axillary lymph node metastasis. Metastases form initially in axillary sentinel lymph nodes and progress via connecting lymphatic vessels into postsentinel lymph nodes. However, the mechanisms of consecutive lymph node colonization are unknown. Through the analysis of human mammary carcinomas and their matching axillary lymph nodes, we show here that intrametastatic lymphatic vessels and bulk tumor cell invasion into these vessels highly correlate with formation of postsentinel metastasis. In an in vitro model of tumor bulk invasion, human mammary carcinoma cells caused circular defects in lymphatic endothelial monolayers. These circular defects were highly reminiscent of defects of the lymphovascular walls at sites of tumor invasion in vivo and were primarily generated by the tumor-derived arachidonic acid metabolite 12S-HETE following 15-lipoxygenase-1 (ALOX15) catalysis. Accordingly, pharmacological inhibition and shRNA knockdown of ALOX15 each repressed formation of circular defects in vitro. Importantly, ALOX15 knockdown antagonized formation of lymph node metastasis in xenografted tumors. Furthermore, expression of lipoxygenase in human sentinel lymph node metastases correlated inversely with metastasis-free survival. These results provide evidence that lipoxygenase serves as a mediator of tumor cell invasion into lymphatic vessels and formation of lymph node metastasis in ductal mammary carcinomas.