Withaferin A inhibits breast cancer invasion and metastasis at sub-cytotoxic doses by inducing vimentin disassembly and serine 56 phosphorylation

Modulating endothelial barrier function by targeting vimentin phosphorylation

Vimentin is a major intermediate filament protein in vascular endothelial cells which might be involved in their function as a barrier tissue. It is proposed to dynamically maintain integrity of the endothelium as a tightly regulated permeability barrier that is subjected to a variety of shear and contractile forces. The results described in this report demonstrate that vimentin plays that role through mechanisms that are dependent on its phosphorylation state. Withaferin A (WFA), a vimentin targeting drug is shown to disrupt endothelial barrier function through its effects on vimentin filament distribution and physical properties. These effects are related to WFA's ability to increase vimentin phosphorylation. Through overexpressing a non-phosphorylatable vimentin mutant we can block the effects of WFA on vimentin distribution and barrier permeability. The barrier augmentation effect appears to extend to endothelial cells that do not express detectable mutant vimentin which might suggest transmissible effects across cells. Blocking vimentin phosphorylation also protects the endothelial barrier against LPS endotoxin, implicating it as a target for drug development against pulmonary edema and acute respiratory distress syndrome (ARDS).

Targeting EMT in cancer: opportunities for pharmacological intervention

The spread of cancer cells to distant organs represents a major clinical challenge in the treatment of cancer. Epithelial-mesenchymal transition (EMT) has emerged as a key regulator of metastasis in some cancers by conferring an invasive phenotype. As well as facilitating metastasis, EMT is thought to generate cancer stem cells and contribute to therapy resistance. Therefore, the EMT pathway is of great therapeutic interest in the treatment of cancer and could be targeted either to prevent tumor dissemination in patients at high risk of developing metastatic lesions or to eradicate existing metastatic cancer cells in patients with more advanced disease. In this review, we discuss approaches for the design of EMT-based therapies in cancer, summarize evidence for some of the proposed EMT targets, and review the potential advantages and pitfalls of each approach.

Dissecting the contribution of actin and vimentin intermediate filaments to mechanical phenotype of suspended cells using high-throughput deformability measurements and computational modeling

Mechanical cell properties play an important role in many basic biological functions, including motility, adhesion, proliferation and differentiation. There is a growing body of evidence that the mechanical cell phenotype can be used for detection and, possibly, treatment of various diseases, including cancer. Understanding of pathological mechanisms requires investigation of the relationship between constitutive properties and major structural components of cells, i.e., the nucleus and cytoskeleton. While the contribution of actin und microtubules to cellular rheology has been extensively studied in the past, the role of intermediate filaments has been scarcely investigated up to now. Here, for the first time we compare the effects of drug-induced disruption of actin and vimentin intermediate filaments on mechanical properties of suspended NK cells using high-throughput deformability measurements and computational modeling. Although, molecular mechanisms of actin and vimentin disruption by the applied cytoskeletal drugs, Cytochalasin-D and Withaferin-A, are different, cell softening in both cases can be attributed to reduction of the effective density and stiffness of filament networks. Our experimental data suggest that actin and vimentin deficient cells exhibit, in average, 41% and 20% higher deformability in comparison to untreated control. 3D Finite Element simulation is performed to quantify the contribution of cortical actin and perinuclear vimentin to mechanical phenotype of the whole cell. Our simulation provides quantitative estimates for decreased filament stiffness in drug-treated cells and predicts more than two-fold increase of the strain magnitude in the perinuclear vimentin layer of actin deficient cells relatively to untreated control. Thus, the mechanical function of vimentin becomes particularly essential in motile and proliferating cells that have to dynamically remodel the cortical actin network. These insights add functional cues to frequently observed overexpression of vimentin in diverse types of cancer and underline the role of vimentin targeting drugs, such as Withaferin-A, as a potent cancerostatic supplement.

Mammary cancer chemoprevention by withaferin A is accompanied by in vivo suppression of self-renewal of cancer stem cells

Current dogma favors elimination of therapy-resistant cancer stem cells for chemoprevention of breast cancer. We showed recently that mammary cancer development in a transgenic mouse model (mouse mammary tumor virus-neu; MMTV-neu) was inhibited significantly upon treatment with withaferin A (WA), a steroidal lactone derived from a medicinal plant. Herein, we demonstrate that the mammary cancer prevention by WA is accompanied by in vivo suppression of breast cancer stem cells (bCSC). In vitro mammosphere formation was dose-dependently inhibited by WA treatment in MCF-7 and SUM159 human breast cancer cells. Other markers of bCSC, including aldehyde dehydrogenase 1 (ALDH1) activity and CD44(high)/CD24(low)/epithelial-specific antigen-positive (ESA+) fraction, were also decreased significantly in the presence of plasma achievable doses of WA. However, WA exposure resulted in cell line-specific changes in Oct4, SOX-2, and Nanog mRNA expression. WA administration to MMTV-neu mice (0.1 mg/mouse, 3 times/week for 28 weeks) resulted in inhibition of mammosphere number and ALDH1 activity in vivo. Mechanistic studies revealed that although urokinase-type plasminogen activator receptor overexpression conferred partial protection against bCSC inhibition by WA, Notch4 was largely dispensable for this response. WA treatment also resulted in sustained (MCF-7) or transient (SUM159) downregulation of Bmi-1 (B-cell-specific Moloney murine leukemia virus insertion region-1) protein. Ectopic expression of Bmi-1 conferred partial but significant protection against ALDH1 activity inhibition by WA. Interestingly, WA treatment caused induction of Kruppel-like factor 4 (KLF4) and its knockdown augmented bCSC inhibition by WA. In conclusion, this study shows in vivo effectiveness of WA against bCSC.

Mechanistic elucidation of the antitumor properties of withaferin a in breast cancer

Withaferin A (WFA) is a steroidal lactone with antitumor effects manifested at multiple levels that are mechanistically obscure. Using a phospho-kinase screening array, we discovered that WFA activated phosphorylation of the S6 kinase RSK (ribosomal S6 kinase) in breast cancer cells. Pursuing this observation, we defined activation of extracellular signal-regulated kinase (ERK)-RSK and ETS-like transcription factor 1 (Elk1)-CHOP (C-EBP homologous protein) kinase pathways in upregulating transcription of the death receptor 5 (DR5). Through this route, WFA acted as an effective DR5 activator capable of potentiating the biologic effects of celecoxib, etoposide, and TRAIL. Accordingly, WFA treatment inhibited breast tumor formation in xenograft and mouse mammary tumor virus (MMTV)-neu mouse models in a manner associated with activation of the ERK/RSK axis, DR5 upregulation, and elevated nuclear accumulation of Elk1 and CHOP. Together, our results offer mechanistic insight into how WFA inhibits breast tumor growth.

Autophagy fails to alter withaferin A-mediated lethality in human breast cancer cells

We have shown previously that withaferin A (WA), which is a highly promising anticancer constituent of Ayurvedic medicine plant Withania somnifera, inhibits viability of cultured breast cancer cells in association with reactive oxygen species (ROS)-dependent apoptosis induction. Because ROS production is implicated in induction of autophagy, which is an evolutionary conserved process for bulk degradation of cellular components including organelles (e.g., mitochondria) and considered a valid cancer chemotherapeutic target, we questioned whether WA treatment resulted in autophagy induction. Indeed exposure of MDA-MB-231 and MCF-7 human breast cancer cells as well as a spontaneously immortalized and non-tumorigenic normal human mammary epithelial cell line (MCF-10A) to pharmacologic concentration of WA resulted in autophagy as evidenced by transmission electron microscopy, processing of microtubuleassociated protein 1 light chain 3 isoform B, and/or acridine orange staining. Inhibition of MDA-MB-231 xenograft growth in vivo by WA administration was also associated with a significant increase in level of LC3 protein in the tumor. However, WA-mediated inhibition of MDA-MB-231 and MCF-7 cell viability was not compromised either by pharmacological suppression of autophagy using 3-methyl adenine or genetic repression of autophagy by RNA interference of Atg5, a critical component of the autophagic machinery. Finally, Beclin1 was dispensable for WA-mediated autophagy as well as inhibition of MDA-MB-231 cell viability. Based on these observations we conclude that autophagy induction fails to have any meaningful impact on WA-mediated lethality in breast cancer cells, which may be a therapeutic advantage because autophagy serves to protect against apoptosis by several anticancer agents.

Phosphoprotein secretome of tumor cells as a source of candidates for breast cancer biomarkers in plasma

Breast cancer is a heterogeneous disease whose molecular diversity is not well reflected in clinical and pathological markers used for prognosis and treatment selection. As tumor cells secrete proteins into the extracellular environment, some of these proteins reach circulation and could become suitable biomarkers for improving diagnosis or monitoring response to treatment. As many signaling pathways and interaction networks are altered in cancerous tissues by protein phosphorylation, changes in the secretory phosphoproteome of cancer tissues could reflect both disease progression and subtype. To test this hypothesis, we compared the phosphopeptide-enriched fractions obtained from proteins secreted into conditioned media (CM) derived from five luminal and five basal type breast cancer cell lines using label-free quantitative mass spectrometry. Altogether over 5000 phosphosites derived from 1756 phosphoproteins were identified, several of which have the potential to qualify as phosphopeptide plasma biomarker candidates for the more aggressive basal and also the luminal-type breast cancers. The analysis of phosphopeptides from breast cancer patient plasma and controls allowed us to construct a discovery list of phosphosites under rigorous collection conditions, and second to qualify discovery candidates generated from the CM studies. Indeed, a set of basal-specific phosphorylation CM site candidates derived from IBP3, CD44, OPN, FSTL3, LAMB1, and STC2, and luminal-specific candidates derived from CYTC and IBP5 were selected and, based on their presence in plasma, quantified across all cell line CM samples using Skyline MS1 intensity data. Together, this approach allowed us to assemble a set of novel cancer subtype specific phosphopeptide candidates for subsequent biomarker verification and clinical validation.

Pharmacological levels of Withaferin A (Withania somnifera) trigger clinically relevant anticancer effects specific to triple negative breast cancer cells

Withaferin A (WA) isolated from Withania somnifera (Ashwagandha) has recently become an attractive phytochemical under investigation in various preclinical studies for treatment of different cancer types. In the present study, a comparative pathway-based transcriptome analysis was applied in epithelial-like MCF-7 and triple negative mesenchymal MDA-MB-231 breast cancer cells exposed to different concentrations of WA which can be detected systemically in in vivo experiments. Whereas WA treatment demonstrated attenuation of multiple cancer hallmarks, the withanolide analogue Withanone (WN) did not exert any of the described effects at comparable concentrations. Pathway enrichment analysis revealed that WA targets specific cancer processes related to cell death, cell cycle and proliferation, which could be functionally validated by flow cytometry and real-time cell proliferation assays. WA also strongly decreased MDA-MB-231 invasion as determined by single-cell collagen invasion assay. This was further supported by decreased gene expression of extracellular matrix-degrading proteases (uPA, PLAT, ADAM8), cell adhesion molecules (integrins, laminins), pro-inflammatory mediators of the metastasis-promoting tumor microenvironment (TNFSF12, IL6, ANGPTL2, CSF1R) and concomitant increased expression of the validated breast cancer metastasis suppressor gene (BRMS1). In line with the transcriptional changes, nanomolar concentrations of WA significantly decreased protein levels and corresponding activity of uPA in MDA-MB-231 cell supernatant, further supporting its anti-metastatic properties. Finally, hierarchical clustering analysis of 84 chromatin writer-reader-eraser enzymes revealed that WA treatment of invasive mesenchymal MDA-MB-231 cells reprogrammed their transcription levels more similarly towards the pattern observed in non-invasive MCF-7 cells. In conclusion, taking into account that sub-cytotoxic concentrations of WA target multiple metastatic effectors in therapy-resistant triple negative breast cancer, WA-based therapeutic strategies targeting the uPA pathway hold promise for further (pre)clinical development to defeat aggressive metastatic breast cancer.

Proteomic analysis of proton beam irradiated human melanoma cells

Proton beam irradiation is a form of advanced radiotherapy providing superior distributions of a low LET radiation dose relative to that of photon therapy for the treatment of cancer. Even though this clinical treatment has been developing for several decades, the proton radiobiology critical to the optimization of proton radiotherapy is far from being understood. Proteomic changes were analyzed in human melanoma cells treated with a sublethal dose (3 Gy) of proton beam irradiation. The results were compared with untreated cells. Two-dimensional electrophoresis was performed with mass spectrometry to identify the proteins. At the dose of 3 Gy a minimal slowdown in proliferation rate was seen, as well as some DNA damage. After allowing time for damage repair, the proteomic analysis was performed. In total 17 protein levels were found to significantly (more than 1.5 times) change: 4 downregulated and 13 upregulated. Functionally, they represent four categories: (i) DNA repair and RNA regulation (VCP, MVP, STRAP, FAB-2, Lamine A/C, GAPDH), (ii) cell survival and stress response (STRAP, MCM7, Annexin 7, MVP, Caprin-1, PDCD6, VCP, HSP70), (iii) cell metabolism (TIM, GAPDH, VCP), and (iv) cytoskeleton and motility (Moesin, Actinin 4, FAB-2, Vimentin, Annexin 7, Lamine A/C, Lamine B). A substantial decrease (2.3 x) was seen in the level of vimentin, a marker of epithelial to mesenchymal transition and the metastatic properties of melanoma.

Growth arrest by the antitumor steroidal lactone withaferin A in human breast cancer cells is associated with down-regulation and covalent binding at cysteine 303 of β-tubulin

Withaferin A (WA), a C5,C6-epoxy steroidal lactone derived from a medicinal plant (Withania somnifera), inhibits growth of human breast cancer cells in vitro and in vivo and prevents mammary cancer development in a transgenic mouse model. However, the mechanisms underlying the anticancer effect of WA are not fully understood. Herein, we report that tubulin is a novel target of WA-mediated growth arrest in human breast cancer cells. The G2 and mitotic arrest resulting from WA exposure in MCF-7, SUM159, and SK-BR-3 cells was associated with a marked decrease in protein levels of β-tubulin. These effects were not observed with the naturally occurring C6,C7-epoxy analogs of WA (withanone and withanolide A). A non-tumorigenic normal mammary epithelial cell line (MCF-10A) was markedly more resistant to mitotic arrest by WA compared with breast cancer cells. Vehicle-treated control cells exhibited a normal bipolar spindle with chromosomes aligned along the metaphase plate. In contrast, WA treatment led to a severe disruption of normal spindle morphology. NMR analyses revealed that the A-ring enone in WA, but not in withanone or withanolide A, was highly reactive with cysteamine and rapidly succumbed to irreversible nucleophilic addition. Mass spectrometry demonstrated direct covalent binding of WA to Cys(303) of β-tubulin in MCF-7 cells. Molecular docking indicated that the WA-binding pocket is located on the surface of β-tubulin and characterized by a hydrophobic floor, a hydrophobic wall, and a charge-balanced hydrophilic entrance. These results provide novel insights into the mechanism of growth arrest by WA in breast cancer cells.

Withaferin A inhibits experimental epithelial-mesenchymal transition in MCF-10A cells and suppresses vimentin protein level in vivo in breast tumors

We have shown previously that withaferin A (WA), a bioactive component of the medicinal plant Withania somnifera, inhibits growth of cultured and xenografted human breast cancer cells and prevents breast cancer development and pulmonary metastasis incidence in a transgenic mouse model. The present study was undertaken to determine if the anticancer effect of WA involved inhibition of epithelial-mesenchymal transition (EMT). Experimental EMT induced by exposure of MCF-10A cells to tumor necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β) was partially reversed by treatment with WA but not by its structural analogs withanone or withanolide A. Combined TNF-α and TGF-β treatments conferred partial protection against MCF-10A cell migration inhibition by WA. Inhibition of TNF-α and TGF-β-induced MCF-10A cell migration by WA exposure was modestly attenuated by knockdown of E-cadherin protein. MCF-7 and MDA-MB-231 cells exposed to WA exhibited sustained (MCF-7) or transient (MDA-MB-231) induction of E-cadherin protein. On the other hand, the level of vimentin protein was increased markedly after 24 h treatment of MDA-MB-231 cells with WA. WA-induced apoptosis was not affected by vimentin protein knockdown in MDA-MB-231 cells. Protein level of vimentin was significantly lower in the MDA-MB-231 xenografts as well as in MMTV-neu tumors from WA-treated mice compared with controls. The major conclusions of the present study are that (a) WA treatment inhibits experimental EMT in MCF-10A cells, and (b) mammary cancer growth inhibition by WA administration is associated with suppression of vimentin protein expression in vivo.

Myeloid-derived suppressor cell function is reduced by Withaferin A, a potent and abundant component of Withania somnifera root extract

Myeloid cells play a crucial role in tumor progression. The most common tumor-infiltrating myeloid cells are myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAMs). These cells promote tumor growth by their inherent immune suppressive activity which is enhanced by their cross-talk. The root extract of the plant Withania somnifera (Ashwagandha) (WRE) has been reported to reduce tumor growth. HPLC analysis identified Withaferin A (WA) as the most abundant constituent of WRE and led us to determine whether the anti-tumor effects of WRE and WA involve modulating MDSC and TAM activity. A prominent effect of MDSC is their production of IL-10 which increases upon cross-talk with macrophages, thus polarizing immunity to a pro-tumor type 2 phenotype. In vitro treatment with WA decreased MDSC production of IL-10 and prevented additional MDSC production of IL-10 generated by MDSC-macrophage cross-talk. Macrophage secretion of IL-6 and TNFα, cytokines that increase MDSC accumulation and function, was also reduced by in vitro treatment with WA. Much of the T-cell suppressive activity of MDSC is due to MDSC production of reactive oxygen species (ROS), and WA significantly reduced MDSC production of ROS through a STAT3-dependent mechanism. In vivo treatment of tumor-bearing mice with WA decreased tumor weight, reduced the quantity of granulocytic MDSC, and reduced the ability of MDSC to suppress antigen-driven activation of CD4+ and CD8+ T cells. Thus, adjunctive treatment with WA reduced myeloid cell-mediated immune suppression, polarized immunity toward a tumor-rejecting type 1 phenotype, and may facilitate the development of anti-tumor immunity.

Molecular targets and mechanisms of cancer prevention and treatment by withaferin a, a naturally occurring steroidal lactone

The plants used in Ayurvedic medicine, which has been practiced in India for thousands of years for the treatment of a variety of disorders, are rich in chemicals potentially useful for prevention and treatment of cancer. Withania somnifera (commonly known as Ashwagandha in Ayurvedic medicine) is one such medicinal plant whose anticancer value was realized over four decades ago after isolation of a crystalline steroidal compound (withaferin A) from the leaves of this shrub. The root and leaf extracts of W. somnifera are shown to confer protection against chemically-induced cancers in experimental rodents, and retard tumor xenograft growth in athymic mice. Anticancer effect of W. somnifera is generally attributable to steroidal lactones collectively referred to as withanolides. Withaferin A (WA) appears most active against cancer among structurally divergent withanolides isolated from the root or leaf of W. somnifera. Cancer-protective role for WA has now been established using chemically-induced and oncogene-driven rodent cancer models. This review summarizes the key in vivo preclinical studies demonstrating anticancer effects of WA. Molecular targets and mechanisms likely contributing to the anticancer effects of WA are also discussed. Finally, challenges in clinical development of WA for the prevention and treatment of cancer are highlighted.

Withania somnifera root extract inhibits mammary cancer metastasis and epithelial to mesenchymal transition

Though clinicians can predict which patients are at risk for developing metastases, traditional therapies often prove ineffective and metastatic disease is the primary cause of cancer patient death; therefore, there is a need to develop anti-metastatic therapies that can be administered over long durations to specifically inhibit the motility of cancer cells. Withaniasomnifera root extracts (WRE) have anti-proliferative activity and the active component, Withaferin A, inhibits the pro-metastatic protein, vimentin. Vimentin is an intermediate filament protein and is part of the epithelial to mesenchymal transition (EMT) program to promote metastasis. Here, we determined whether WRE standardized to Withaferin A (sWRE) possesses anti-metastatic activity and whether it inhibits cancer motility via inhibition of vimentin and the EMT program. Several formulations of sWRE were created to enrich for Withaferin A and a stock solution of sWRE in EtOH could recover over 90% of the Withaferin A found in the original extract powder. This sWRE formulation inhibited breast cancer cell motility and invasion at concentrations less than 1µM while having negligible cytotoxicity at this dose. sWRE treatment disrupted vimentin morphology in cell lines, confirming its vimentin inhibitory activity. To determine if sWRE inhibited EMT, TGF-β was used to induce EMT in MCF10A human mammary epithelial cells. In this case, sWRE prevented EMT induction and inhibited 3-D spheroid invasion. These studies were taken into a human xenograft and mouse mammary carcinoma model. In both models, sWRE and Withaferin A showed dose-dependent inhibition of tumor growth and metastatic lung nodule formation with minimal systemic toxicity. Taken together, these data support the hypothesis that low concentrations of sWRE inhibit cancer metastasis potentially through EMT inhibition. Moreover, these doses of sWRE have nearly no toxicity in normal mouse organs, suggesting the potential for clinical use of orally administered WRE capsules.

Role of mitogen-activated protein kinases and Mcl-1 in apoptosis induction by withaferin A in human breast cancer cells

Withaferin A (WA), a bioactive constituent of Ayurvedic medicine plant Withania somnifera, is a potent apoptosis inducer in cancer cells but the mechanism of cell death induction is not fully characterized. The present study was undertaken to determine the role of mitogen-activated protein kinases (MAPK), including c-jun NH2 -terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and p38 MAPK, and anti-apoptotic protein myeloid cell leukemia-1 (Mcl-1) in regulation of WA-induced apoptosis using human breast cancer cells. Exposure of MCF-7 (estrogen responsive) and SUM159 (triple negative) human breast cancer cells to WA resulted in increased phosphorylation of ERK, JNK, and p38 MAPK, but these effects were relatively more pronounced in the former cell line than in SUM159. Overexpression of manganese-superoxide dismutase conferred partial protection against WA-mediated hyperphosphorylation of ERK, but not JNK or p38 MAPK. Cell death resulting from WA treatment in MCF-7 cells was significantly augmented by pharmacological inhibition of ERK and p38 MAPK. Interestingly, the WA-induced apoptosis in MCF-7 cells was partially but significantly blocked in the presence of a JNK-specific inhibitor. Pharmacological inhibition of ERK or JNK had no effect on WA-induced apoptosis in SUM159 cells. The WA-treated cells exhibited induction of long and short forms of Mcl-1. RNA interference of Mcl-1 alone triggered apoptosis. Furthermore, the WA-induced cell death in MCF-7 cells was modestly but significantly augmented by knockdown of the Mcl-1 protein. These observations indicate that: MAPK have cell line-specific role in cell death by WA, and Mcl-1 induction confers modest protection against WA-induced apoptosis.

Metabolic alterations in mammary cancer prevention by withaferin A in a clinically relevant mouse model

BACKGROUND

Efficacy of withaferin A (WA), an Ayurvedic medicine constituent, for prevention of mammary cancer and its associated mechanisms were investigated using mouse mammary tumor virus-neu (MMTV-neu) transgenic model.

METHODS

Incidence and burden of mammary cancer and pulmonary metastasis were scored in female MMTV-neu mice after 28 weeks of intraperitoneal administration with 100 µg WA (three times/week) (n = 32) or vehicle (n = 29). Mechanisms underlying mammary cancer prevention by WA were investigated by determination of tumor cell proliferation, apoptosis, metabolomics, and proteomics using plasma and/or tumor tissues. Spectrophotometric assays were performed to determine activities of complex III and complex IV. All statistical tests were two-sided.

RESULTS

WA administration resulted in a statistically significant decrease in macroscopic mammary tumor size, microscopic mammary tumor area, and the incidence of pulmonary metastasis. For example, the mean area of invasive cancer was lower by 95.14% in the WA treatment group compared with the control group (mean = 3.10 vs 63.77 mm2, respectively; difference = -60.67 mm2; 95% confidence interval = -122.50 to 1.13 mm2; P = .0536). Mammary cancer prevention by WA treatment was associated with increased apoptosis, inhibition of complex III activity, and reduced levels of glycolysis intermediates. Proteomics confirmed downregulation of many glycolysis-related proteins in the tumor of WA-treated mice compared with control, including M2-type pyruvate kinase, phospho glycerate kinase, and fructose-bisphosphate aldolase A isoform 2.

CONCLUSIONS

This study reveals suppression of glycolysis in WA-mediated mammary cancer prevention in a clinically relevant mouse model.

Withaferin A effectively targets soluble vimentin in the glaucoma filtration surgical model of fibrosis

Withaferin A (WFA) is a natural product that binds to soluble forms of the type III intermediate filament (IF) vimentin. Currently, it is unknown under what pathophysiological contexts vimentin is druggable, as cytoskeltal vimentin-IFs are abundantly expressed. To investigate druggability of vimentin, we exploited rabbit Tenon's capsule fibroblast (RbTCF) cell cultures and the rabbit glaucoma filtration surgical (GFS) model of fibrosis. WFA potently caused G₀/G₁ cell cycle inhibition (IC₅₀ 25 nM) in RbTCFs, downregulating ubiquitin E3 ligase skp2 and inducing p27(Kip1) expression. Transforming growth factor (TGF)-ß-induced myofibroblast transformation caused development of cell spheroids with numerous elongated invadopodia, which WFA blocked potently by downregulating soluble vimentin and α-smooth muscle actin (SMA) expression. In the pilot proof-of-concept study using the GFS model, subconjunctival injections of a low WFA dose reduced skp2 expression in Tenon's capsule and increased p27(Kip1) expression without significant alteration to vimentin-IFs. This treatment maintains significant nanomolar WFA concentrations in anterior segment tissues that correspond to WFA's cell cycle targeting activity. A ten-fold higher WFA dose caused potent downregulation of soluble vimentin and skp2 expression, but as found in cell cultures, no further increase in p27(Kip1) expression was observed. Instead, this high WFA dose potently induced vimentin-IF disruption and downregulated α-SMA expression that mimicked WFA activity in TGF-ß-treated RbTCFs that blocked cell contractile activity at submicromolar concentrations. These findings illuminate that localized WFA injection to ocular tissues exerts pharmacological control over the skp2-p27(Kip1) pathway by targeting of soluble vimentin in a model of surgical fibrosis.

LKB1 represses focal adhesion kinase (FAK) signaling via a FAK-LKB1 complex to regulate FAK site maturation and directional persistence

Liver kinase β1 (LKB1, also known as STK11) is a serine/threonine kinase that has multiple cellular functions including the regulation of cell polarity and motility. Murine proteomic studies show that LKB1 loss causes aberrant adhesion signaling; however, the mechanistic underpinnings of this relationship are unknown. We show that cells stably depleted of LKB1 or its co-activator STRADα have increased phosphorylation of focal adhesion kinase (FAK) at Tyr(397)/Tyr(861) and enhanced adhesion to fibronectin. LKB1 associates in a complex with FAK and LKB1 accumulation at the cellular leading edge is mutually excluded from regions of activated Tyr(397)-FAK. LKB1-compromised cells lack directional persistence compared with wild-type cells, but this is restored through subsequent pharmacological FAK inhibition or depletion, showing that cell directionality is mediated through LKB1-FAK signaling. Live cell confocal imaging reveals that LKB1-compromised cells lack normal FAK site maturation and turnover, suggesting that defects in adhesion and directional persistence are caused by aberrant adhesion dynamics. Furthermore, re-expression of full-length wild-type or the LKB1 N-terminal domain repressed FAK activity, whereas the kinase domain or C-terminal domain alone did not, indicating that FAK suppression is potentially regulated through the LKB1 N-terminal domain. Based upon these results, we conclude that LKB1 serves as a FAK repressor to stabilize focal adhesion sites, and when LKB1 function is compromised, aberrant FAK signaling ensues, resulting in rapid FAK site maturation and poor directional persistence.

Anticancer steroids: linking natural and semi-synthetic compounds

Steroids, a widespread class of natural organic compounds occurring in animals, plants and fungi, have shown great therapeutic value for a broad array of pathologies. The present overview is focused on the anticancer activity of steroids, which is very representative of a rich structural molecular diversity and ability to interact with various biological targets and pathways. This review encompasses the most relevant discoveries on steroid anticancer drugs and leads through the last decade and comprises 668 references.

Endoplasmic spreading requires coalescence of vimentin intermediate filaments at force-bearing adhesions

Interaction of vimentin filaments (vIFs) and force-bearing adhesions is essential for endoplasm spreading. For adhesions to be connected to a contractile network involved in endoplasm spreading, vIFs are needed. Thus endoplasm spreading and microtubule stabilization in the periphery require a multicomponent actin network anchored at adhesions.

For cells to develop long-range forces and carry materials to the periphery, the microtubule and organelle-rich region at the center of the cell—the endoplasm—needs to extend to near the cell edge. Depletion of the actin cross-linking protein filamin A (FlnA) causes a collapse of the endoplasm into a sphere around the nucleus of fibroblasts and disruption of matrix adhesions, indicating that FlnA is involved in endoplasmic spreading and adhesion growth. Here, we report that treatment with the calpain inhibitor N-[N-(N-acetyl-l-leucyl)-l-leucyl]-l-norleucine (ALLN) restores endoplasmic spreading as well as focal adhesion (FA) growth on fibronectin-coated surfaces in a Fln-depleted background. Addback of calpain-uncleavable talin, not full-length talin, achieves a similar effect in Fln-depleted cells and indicates a crucial role for talin in endoplasmic spreading. Because FA maturation involves the vimentin intermediate filament (vIF) network, we also examined the role of vIFs in endoplasmic spreading. Wild-type cells expressing a vimentin variant incapable of polymerization exhibit deficient endoplasmic spreading as well as defects in FA growth. ALLN treatment restores FA growth despite the lack of vIFs but does not restore endoplasmic spreading, implying that vIFs are essential for endoplasm spreading. Consistent with that hypothesis, vIFs are always displaced from adhesions when the endoplasm does not spread. In Fln-depleted cells, vIFs extend beyond adhesions, nearly to the cell edge. Finally, inhibiting myosin II–mediated contraction blocks endoplasmic spreading and adhesion growth. Thus we propose a model in which myosin II–mediated forces and coalescence of vIFs at mature FAs are required for endoplasmic spreading.

Withaferin A-stimulated Ca2+ entry, ceramide formation and suicidal death of erythrocytes

Withaferin A, a triterpenoid component from Withania somnifera, counteracts malignancy, an effect attributed to stimulation of apoptosis. Withaferin A is partially effective through induction of oxidative stress, altered gene expression and mitochondrial depolarization. Erythrocytes lack mitochondria and nuclei but may enter apoptosis-like eryptosis, a suicidal cell death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Triggers of eryptosis include increase of cytosolic Ca(2+)-activity [Ca(2+)](i) following activation of oxidant-sensitive Ca(2+)-permeable cation channels, ceramide formation and/or ATP-depletion. The present study explored, whether withaferin A triggers eryptosis. To this end, [Ca(2+)](i) was estimated from Fluo3-fluorescence, cell volume from forward scatter, phosphatidylserine exposure from annexin-V-binding, hemolysis from hemoglobin release, oxidative stress from DCFDA-fluorescence and ceramide abundance utilizing antibodies. A 48 h exposure to withaferin A significantly decreased forward scatter (at ≥ 10 μM withaferin concentration) and increased [Ca(2+)](i) (≥ 5 μM), ROS-formation (≥ 10 μM) ceramide-formation ( ≥ 10 μM) as well as annexin-V-binding ( ≥ 5 μM). Withaferin A treatment was followed by slight but significant increase of hemolysis. Extracellular Ca(2+) removal, amiloride, and the antioxidant N-acetyl-l-cysteine significantly blunted withaferin A-triggered annexin-V-binding. The present observations reveal that withaferin A triggers suicidal erythrocyte death despite the absence of gene expression and key elements of apoptosis such as mitochondria.

Withaferin A causes activation of Notch2 and Notch4 in human breast cancer cells

Ayurvedic medicine plants continue to draw attention for the discovery of novel anticancer agents. Withaferin A (WA) is one such small-molecule constituent of the ayurvedic medicine plant Withania somnifera with efficacy against cultured and xenografted human breast cancer cells. However, the mechanism underlying anticancer effect of WA is not fully understood. This study was undertaken to determine the role of Notch signaling in anticancer effects of WA using human breast cancer cells as a model. Notably, Notch signaling is often hyperactive in human breast cancers. Exposure of MDA-MB-231 and MCF-7 human breast cancer cells to pharmacological concentrations of WA resulted in cleavage (activation) of Notch2 as well as Notch4, which was accompanied by transcriptional activation of Notch as evidenced by RBP-Jk, HES-1A/B, and HEY-1 luciferase reporter assays. On the other hand, WA treatment caused a decrease in levels of both transmembrane and cleaved Notch1. The WA-mediated activation of Notch was associated with induction of γ-secretase complex components presenilin1 and/or nicastrin. Inhibition of MDA-MB-231 and MDA-MB-468 cell migration resulting from WA exposure was significantly augmented by knockdown of Notch2 as well as Notch4 protein. Activation of Notch2 was not observed in cells treated with withanone or withanolide A, which are structural analogs of WA. The results of this study indicate that WA treatment activates Notch2 and Notch4, which impede inhibitory effect of WA on breast cancer cell migration.

Molecular insight in the multifunctional activities of Withaferin A

Herbal medicine which involves the use of plants for their medicinal value, dates as far back as the origin of mankind and demonstrates an array of applications including cardiovascular protection and anti-cancer activities, via antioxidant, anti-inflammatory and metabolic activities. Even today the popularity of medicinal herbs is still growing like in traditional medicines such as the Indian medicine, Ayurveda. One of the Ayurvedic medicinal plants is Withania somnifera Dunal, of which the important constituents are the withanolides. Among them, Withaferin A is one of the most bioactive compounds, exerting anti-inflammatory, pro-apoptotic but also anti-invasive and anti-angiogenic effects. In the context of modern pharmacology, a better insight in the underlying mechanism of the broad range of bioactivities exerted by Withaferin A is compulsory. Therefore, a lot of effort was made to explore the intracellular effects of Withaferin A and to characterize its target proteins. This review provides a decisive insight on the molecular basis of the health-promoting potential of Withaferin A.

Withaferin A-induced apoptosis in human breast cancer cells is associated with suppression of inhibitor of apoptosis family protein expression

The present study provides novel insight into the mechanism of apoptosis induction by withaferin A (WA), which is a bioactive constituent of an Ayurvedic medicine plant (Withania somnifera). Exposure of MDA-MB-231 and MCF-7 human breast cancer cells to WA resulted in suppression of XIAP, cIAP-2, and Survivin protein levels. The WA-induced apoptosis was significantly attenuated by ectopic expression of XIAP, Survivin, and cIAP-2 in both cells. However, the WA-mediated inhibition of MDA-MB-231 xenograft growth in vivo was associated with suppression of Survivin protein level only. These results indicate important contribution of Survivin suppression in WA-induced apoptosis.

Withaferin-A reduces type I collagen expression in vitro and inhibits development of myocardial fibrosis in vivo

Type I collagen is the most abundant protein in the human body. Its excessive synthesis results in fibrosis of various organs. Fibrosis is a major medical problem without an existing cure. Excessive synthesis of type I collagen in fibrosis is primarily due to stabilization of collagen mRNAs. We recently reported that intermediate filaments composed of vimentin regulate collagen synthesis by stabilizing collagen mRNAs. Vimentin is a primary target of Withaferin-A (WF-A). Therefore, we hypothesized that WF-A may reduce type I collagen production by disrupting vimentin filaments and decreasing the stability of collagen mRNAs. This study is to determine if WF-A exhibits anti-fibrotic properties in vitro and in vivo and to elucidate the molecular mechanisms of its action. In lung, skin and heart fibroblasts WF-A disrupted vimentin filaments at concentrations of 0.5-1.5 µM and reduced 3 fold the half-lives of collagen α1(I) and α2(I) mRNAs and protein expression. In addition, WF-A inhibited TGF-β1 induced phosphorylation of TGF-β1 receptor I, Smad3 phosphorylation and transcription of collagen genes. WF-A also inhibited in vitro activation of primary hepatic stellate cells and decreased their type I collagen expression. In mice, administration of 4 mg/kg WF-A daily for 2 weeks reduced isoproterenol-induced myocardial fibrosis by 50%. Our findings provide strong evidence that Withaferin-A could act as an anti-fibrotic compound against fibroproliferative diseases, including, but not limited to, cardiac interstitial fibrosis.

Withaferin A synergizes the therapeutic effect of doxorubicin through ROS-mediated autophagy in ovarian cancer

Application of doxorubicin (Dox) for the treatment of cancer is restricted due to its severe side effects. We used combination strategy by combining doxorubicin (Dox) with withaferin A (WFA) to minimize the ill effects of Dox. Treatment of various epithelial ovarian cancer cell lines (A2780, A2780/CP70 and CaOV3) with combination of WFA and Dox (WFA/DOX) showed a time- and dose-dependent synergistic effect on inhibition of cell proliferation and induction of cell death, thus reducing the dosage requirement of Dox. Combination treatment resulted in a significant enhancement of ROS production resulting in immense DNA damage, induction of autophagy analyzed by transmission electron microscope and increase in expression of autophagy marker LC3B, and culminated in cell death analyzed by cleaved caspase 3. We validated combination therapy on tumor growth using an in vitro 3Dimension (3D) tumor model and the more classic in vivo xenograft model of ovarian cancer. Both tumor models showed a 70 to 80% reduction in tumor growth compared to control or animals treated with WFA or Dox alone. Immunohistochemical analysis of the tumor tissues from animals treated with WFA/Dox combination showed a significant reduction in cell proliferation and formation of microvessels accompanied by increased in LC3B level, cleaved caspase 3, and DNA damage. Taken together, our data suggest that combining WFA with Dox decreases the dosage requirement of Dox, therefore, minimizing/eliminating the severe side effects associated with high doses of DOX, suggesting the application of this combination strategy for the treatment of ovarian and other cancers with no or minimum side effects.

Multi-layer polymeric implants for sustained release of chemopreventives

Poor oral bioavailability limits the use of many chemopreventives in the prevention and treatment of cancer. To overcome this limitation, we report an improvised implant formulation ("coated" implants) using curcumin, individual curcuminoids, withaferin A and oltipraz. This method involves the coating of blank polycaprolactone implants with 20-30 layers of 10-20% polycaprolactone solution in dichloromethane containing 0.5-2% of the test agent. The in vitro release showed that while oltipraz was released with almost zero-order kinetics over 8 weeks, curcumin, individual curcuminoids and withaferin A were released with some initial burst. The in vivo release was determined by grafting implants subcutaneously in A/J mice. When delivered by coated implants, oltipraz significantly diminished lung DNA adducts in mice treated with dibenzo[a,l]pyrene compared with sham treatment (28 ± 7 versus 54 ± 17 adducts/10(9) nucleotides). Withaferin A also diminished DNA adducts, but it was insignificant. Curcumin and individual curcuminoids were ineffective. Analysis of lung, liver and brain by UPLC-fluorescence showed the presence of the three test curcuminoids indicating effectiveness of the implant delivery system. Further, based on its known antitumor activity in vivo, withaferin A given via the implants significantly inhibited human lung cancer A549 xenograft in athymic nude mice, while it was ineffective when the same total dose was administered i.p. and required over 2-fold higher dose to elicit effectiveness. Together, our data suggest that coated polymeric implants can accommodate heat-labile compounds, can furnish sustained release for long duration, and elicit DNA damage-inhibiting and anti-tumor activities.

Withaferin a alters intermediate filament organization, cell shape and behavior

Withaferin A (WFA) is a steroidal lactone present in Withania somnifera which has been shown in vitro to bind to the intermediate filament protein, vimentin. Based upon its affinity for vimentin, it has been proposed that WFA can be used as an anti-tumor agent to target metastatic cells which up-regulate vimentin expression. We show that WFA treatment of human fibroblasts rapidly reorganizes vimentin intermediate filaments (VIF) into a perinuclear aggregate. This reorganization is dose dependent and is accompanied by a change in cell shape, decreased motility and an increase in vimentin phosphorylation at serine-38. Furthermore, vimentin lacking cysteine-328, the proposed WFA binding site, remains sensitive to WFA demonstrating that this site is not required for its cellular effects. Using analytical ultracentrifugation, viscometry, electron microscopy and sedimentation assays we show that WFA has no effect on VIF assembly in vitro. Furthermore, WFA is not specific for vimentin as it disrupts the cellular organization and induces perinuclear aggregates of several other IF networks comprised of peripherin, neurofilament-triplet protein, and keratin. In cells co-expressing keratin IF and VIF, the former are significantly less sensitive to WFA with respect to inducing perinuclear aggregates. The organization of microtubules and actin/microfilaments is also affected by WFA. Microtubules become wavier and sparser and the number of stress fibers appears to increase. Following 24 hrs of exposure to doses of WFA that alter VIF organization and motility, cells undergo apoptosis. Lower doses of the drug do not kill cells but cause them to senesce. In light of our findings that WFA affects multiple IF systems, which are expressed in many tissues of the body, caution is warranted in its use as an anti-cancer agent, since it may have debilitating organism-wide effects.

In Silico Analysis of Microarray-Based Gene Expression Profiles Predicts Tumor Cell Response to Withanolides

Withania somnifera (L.) Dunal (Indian ginseng, winter cherry, Solanaceae) is widely used in traditional medicine. Roots are either chewed or used to prepare beverages (aqueous decocts). The major secondary metabolites of Withania somnifera are the withanolides, which are C-28-steroidal lactone triterpenoids. Withania somnifera extracts exert chemopreventive and anticancer activities in vitro and in vivo. The aims of the present in silico study were, firstly, to investigate whether tumor cells develop cross-resistance between standard anticancer drugs and withanolides and, secondly, to elucidate the molecular determinants of sensitivity and resistance of tumor cells towards withanolides. Using IC₅₀ concentrations of eight different withanolides (withaferin A, withaferin A diacetate, 3-azerininylwithaferin A, withafastuosin D diacetate, 4-B-hydroxy-withanolide E, isowithanololide E, withafastuosin E, and withaperuvin) and 19 established anticancer drugs, we analyzed the cross-resistance profile of 60 tumor cell lines. The cell lines revealed cross-resistance between the eight withanolides. Consistent cross-resistance between withanolides and nitrosoureas (carmustin, lomustin, and semimustin) was also observed. Then, we performed transcriptomic microarray-based COMPARE and hierarchical cluster analyses of mRNA expression to identify mRNA expression profiles predicting sensitivity or resistance towards withanolides. Genes from diverse functional groups were significantly associated with response of tumor cells to withaferin A diacetate, e.g. genes functioning in DNA damage and repair, stress response, cell growth regulation, extracellular matrix components, cell adhesion and cell migration, constituents of the ribosome, cytoskeletal organization and regulation, signal transduction, transcription factors, and others.

Corneal antifibrotic switch identified in genetic and pharmacological deficiency of vimentin

The type III intermediate filaments (IFs) are essential cytoskeletal elements of mechanosignal transduction and serve critical roles in tissue repair. Mice genetically deficient for the IF protein vimentin (Vim(-/-)) have impaired wound healing from deficits in myofibroblast development. We report a surprising finding made in Vim(-/-) mice that corneas are protected from fibrosis and instead promote regenerative healing after traumatic alkali injury. This reparative phenotype in Vim(-/-) corneas is strikingly recapitulated by the pharmacological agent withaferin A (WFA), a small molecule that binds to vimentin and down-regulates its injury-induced expression. Attenuation of corneal fibrosis by WFA is mediated by down-regulation of ubiquitin-conjugating E3 ligase Skp2 and up-regulation of cyclin-dependent kinase inhibitors p27(Kip1) and p21(Cip1). In cell culture models, WFA exerts G(2)/M cell cycle arrest in a p27(Kip1)- and Skp2-dependent manner. Finally, by developing a highly sensitive imaging method to measure corneal opacity, we identify a novel role for desmin overexpression in corneal haze. We demonstrate that desmin down-regulation by WFA via targeting the conserved WFA-ligand binding site shared among type III IFs promotes further improvement of corneal transparency without affecting cyclin-dependent kinase inhibitor levels in Vim(-/-) mice. This dissociates a direct role for desmin in corneal cell proliferation. Taken together, our findings illuminate a previously unappreciated pathogenic role for type III IF overexpression in corneal fibrotic conditions and also validate WFA as a powerful drug lead toward anti-fibrosis therapeutic development.

Deregulation of TDP-43 in amyotrophic lateral sclerosis triggers nuclear factor κB-mediated pathogenic pathways

TDP-43 (TAR DNA-binding protein 43) inclusions are a hallmark of amyotrophic lateral sclerosis (ALS). In this study, we report that TDP-43 and nuclear factor κB (NF-κB) p65 messenger RNA and protein expression is higher in spinal cords in ALS patients than healthy individuals. TDP-43 interacts with and colocalizes with p65 in glial and neuronal cells from ALS patients and mice expressing wild-type and mutant TDP-43 transgenes but not in cells from healthy individuals or nontransgenic mice. TDP-43 acted as a co-activator of p65, and glial cells expressing higher amounts of TDP-43 produced more proinflammatory cytokines and neurotoxic mediators after stimulation with lipopolysaccharide or reactive oxygen species. TDP-43 overexpression in neurons also increased their vulnerability to toxic mediators. Treatment of TDP-43 mice with Withaferin A, an inhibitor of NF-κB activity, reduced denervation in the neuromuscular junction and ALS disease symptoms. We propose that TDP-43 deregulation contributes to ALS pathogenesis in part by enhancing NF-κB activation and that NF-κB may constitute a therapeutic target for the disease.

Vimentin is sufficient and required for wound repair and remodeling in alveolar epithelial cells

The physiological and pathophysiological implications of the expression of vimentin, a type III intermediate filament protein, in alveolar epithelial cells (AECs) are unknown. We provide data demonstrating that vimentin is regulated by TGFβ1, a major cytokine released in response to acute lung injury and that vimentin is required for wound repair and remodeling of the alveolar epithelium. Quantitative real-time PCR shows a 16-fold induction of vimentin mRNA in TGFβ1-treated transformed AECs. Luciferase assays identify a Smad-binding element in the 5' promoter of vimentin responsible for TGFβ1-induced transcription. Notably, TGFβ1 induces vimentin protein expression in AECs, which is associated with a 2.5-fold increase in cell motility, resulting in increased rates of migration and wound closure. These effects are independent of cell proliferation. TGFβ1-mediated vimentin protein expression, cell migration, and wound closure are prevented by a pharmacological inhibitor of the Smad pathway and by expression of Ad-shRNA against vimentin. Conversely, overexpression of mEmerald-vimentin is sufficient for increased cell-migration and wound-closure rates. These results demonstrate that vimentin is required and sufficient for increased wound repair in an in vitro model of lung injury.