Withaferin A Induces Proteasome-Dependent Degradation of Breast Cancer Susceptibility Gene 1 and Heat Shock Factor 1 Proteins in Breast Cancer Cells

This is the publisher's version, also available electronically from "http://www.hindawi.com".The purpose of this study was to examine the regulation of prosurvival factors heat shock factor 1 (HSF1) and breast cancer susceptibility gene 1 (BRCA1) by a natural withanolide withaferin A (WA) in triple negative breast cancer cell lines MDA-MB-231 and BT20. Western analysis was used to examine alternations in HSF1 and BRCA1 protein levels following WA treatment. A protein synthesis inhibitor cycloheximide and a proteasome inhibitor MG132 were used to investigate the mechanisms of HSF1 and BRCA1 regulation by WA. It was found that WA induced a dose-dependent decrease in HSF1 and BRCA1 protein levels. Further analysis showed that levels of HSF1 and BRCA1 proteins decreased rapidly after WA treatment, and this was attributed to WA-induced denaturation of HSF1 and BRCA1 proteins and subsequent degradation via proteasome-dependent, and protein-synthesis dependent mechanism. In summary, WA induces denaturation and proteasomal degradation of HSF1 and BRCA1 proteins. Further studies are warranted to examine the contribution of HSF1 and BRCA1 depletion to the anticancer effects of WA in breast cancer

Anti-proliferative withanolides from the Solanaceae: a structure-activity study

This is the publisher's version, also available electronically from "http://www.degruyter.com".As part of our search for bioactive compounds from plant biodiversity, 29 withanolides were recently isolated from three members of the Solanaceae: Physalis longifolia, Vassobia breviflora, and Withania somnifera. Six derivatives were prepared from these naturally occurring withanolides. All compounds were evaluated for in vitro antiproliferative activity against an array of cell lines [melanoma cell lines (B16F10, SKMEL28); human head and neck squamous cell carcinomas (HNSCC) cell lines (JMAR, MDA1986, DR081-1); breast cancer cell line (Hs578T), and non-malignant human cell line (MRC5)]. This led to the discovery of 15 withanolides, with IC50 values in the range of 0.067−17.4 μM, including withaferin A, withaferin A 4,27-diacetate, 27-O-glucopyranosylwithaferin A, withalongolide H, withalongolide C, withalongolide A, withalongolide A 4,27-diacetate, withalongolide A 4,19,27-triacetate, withalongolide B, withalongolide B 4-acetate, withalongolide B 4,19-diacetate, withalongolide D, withalongolide E, withalongolide G, and 2,3-dihydrowithaferin A 3-O-sulfate. In order to update the growing literature on withanolides and their activities, we summarized the distribution, structural types, and antiproliferative activities for all published withanolides to date. The structure–activity relationship analysis (SARA) confirmed the importance of the presence of a ∆2-1-oxo-functionality in ring A, a 5β,6β-epoxy or 5α-chloro-6β-hydroxy grouping in ring B, and nine-carbon side chain with a lactone moiety for cytotoxic activity. Conversely, the SARA indicated that the –OH or –OR groups at C-4, 7, 11, 12, 14, 15, 16, 17, 18, 19, 20, 23, 24, 27, and 28 were not contributors to the observed antiproliferative activity within the systems analyzed

A novel RET inhibitor with potent efficacy against medullary thyroid cancer in vivo

Background Most medullary thyroid carcinomas (MTC) recur or progress despite optimal surgical resection. Current targeted-therapies show promise but lack durable efficacy and tolerability. The purpose of this study was to build upon previous in vitro work and evaluate Withaferin A (WA), a novel RET inhibitor, in a metastatic murine model of MTC. Methods 5 million DRO-81-1 human MTC-cells injected in the left posterior neck of Nu/Nu mice uniformly generated metastases to the liver, spleen, and/or lungs. Treatment with WA (8mg/kg/day i.p.×21 days) was started for tumors >100 mm3. Endpoints were survival, tumor>1500 mm3, decreased bodyweight, or body score (all measured thrice weekly). Results All controls (saline; n=5) died or deteriorated from metastatic disease by 7 weeks post injection. All treated animals were alive,(WA; n=5), having tumor regression and growth-delay without toxicity or weight-loss at 6 wks post treatment; p<0.01. Tumor cells treated with WA demonstrated inhibition of total and phospho-RET levels by Western-Blot analysis in a dose-dependent manner (almost complete inhibition with 5uM WA treatment) as well as potent inhibition of phospho-ERK and phospho-AKT levels. Conclusions Withaferin A is a novel natural-product RET-inhibitor with efficacy in a metastatic murine model of MTC. Further long-term efficacy/toxicity studies are warranted to evaluate this compound for clinical translation

Cytotoxic Oleanane-Type Saponins from Albizia inundata

Bioassay-guided fractionation of a CH2Cl2−MeOH extract of the aerial parts of Albizia inundata resulted in the isolation of two new natural oleanane-type triterpene saponins {3-O-[α-l-arabinopyranosyl(1→6)]-2-acetamido-2-deoxy-β-d-glucopyranosyl oleanolic acid (1) and 3-O-[α-l-arabinopyranosyl(1→2)-α-l-arabinopyranosyl(1→6)]-2-acetamido-2-deoxy-β-d-glucopyranosyl acacic acid lactone (2)} along with seven known saponins {3-O-[α-l-arabinopyranosyl(1→6)]-2-acetamido-2-deoxy-β-d-glucopyranosyl echinocystic acid (3), 3-O-[β-d-xylopyranosyl (l→2)-α-l-arabinopyranosyl(l→6)]-2-acetamido-2-deoxy-β-d-glucopyranosyl acacic acid lactone (concinnoside D) (4), 3-O-[β-d-glucopyranosyl(l→2)]-β-d-glucopyranosyl oleanolic acid (5), 3-O-[α-l-arabinopyranosyl(1→2)-α-l-arabinopyranosyl(l→6)]-β-d-glucopyranosyl oleanolic acid (6), 3-O-[β-d-xylopyranosyl(1→2)-α-l-arabinopyranosyl(l→6)]-β-d-glucopyranosyl oleanolic acid (7), 3-O-[α-l-arabinopyranosyl(l→2)-α-l-arabinopyranosyl(1→6)-[β-d-glucopyranosyl(l→2)]-β-d-glucopyranoside echinocystic acid (8), and 3-O-[β-d-xylopyranosyl(l→2)-α-l-arabinopyranosyl(1→6)-[β-d-glucopyranosyl(l→2)]-β-d-glucopyranoside echinocystic acid (9)}. The structures of 1 and 2 were established on the basis of extensive 2D NMR (1H−1H COSY or DQF-COSY, HSQC, HMBC, TOCSY, and HSQC-TOCSY) spectroscopic, ESIMS, and chemical methods. Saponins 1, 3, 6, and 7 showed cytotoxicity against human head and neck squamous cells (JMAR, MDA1986) and melanoma cells (B16F10, SKMEL28) with IC50 values in the range 1.8−12.4 μM, using the MTS assay

Withaferin A, a Cytotoxic Steroid from Vassobia breWiflora, Induces Apoptosis in Human Head and Neck Squamous Cell Carcinoma

As part of a program to discover drug leads from plant biodiversity, the present investigation was undertaken to explore the anticancer potential of compounds derived from selected Latin American plants. Bioassay-guided fractionation of a crude extract of the aerial parts of Vassobia breviflora led to the isolation of the withanolide-type steroidal lactone withaferin A (1). This compound was tested for antiproliferative activity against the head and neck squamous cell carcinoma (HNSCC) cell lines, MDA1986, JMAR, UM-SCC-2, and JHU011. The inhibitory concentrations to reduce cell viability to 50% (IC50) were determined by the MTS cytotoxicity assay, and 1 reduced cell viability with IC50 values in the range 0.5−2.2 μM. A mechanistic study showed that 1 induces apoptosis and cell death in HNSCC cells as well as a cell-cycle shift from G0/G1 to G2/M. Cells treated with 1 exhibited inactivation of Akt and a reduction in total Akt concentration. This investigation constitutes the first report of the antiproliferative activity of withaferin A (1) against head and neck squamous carcinoma

Cytotoxicity of withaferin A in glioblastomas involves induction of an oxidative stress-mediated heat shock response while altering Akt/mTOR and MAPK signaling pathways

Withaferin A (WA), a steroidal lactone derived from the plant Vassobia breviflora, has been reported to have anti-proliferative, pro-apoptotic, and anti-angiogenic properties against cancer growth. In this study, we identified several key underlying mechanisms of anticancer action of WA in glioblastoma cells. WA was found to inhibit proliferation by inducing a dose-dependent G2/M cell cycle arrest and promoting cell death through both intrinsic and extrinsic apoptotic pathways. This was accompanied by an inhibitory shift in the Akt/mTOR signaling pathway which included diminished expression and/or phosphorylation of Akt, mTOR, p70 S6K, and p85 S6K with increased activation of AMPKα and the tumor suppressor tuberin/TSC2. Alterations in proteins of the MAPK pathway and cell surface receptors like EGFR, Her2/ErbB2, and c-Met were also observed. WA induced an N-acetyl-L-cysteinerepressible enhancement in cellular oxidative potential/stress with subsequent induction of a heat shock stress response primarily through HSP70, HSP32, and HSP27 upregulation and HSF1 downregulation. Taken together, we suggest that WA may represent a promising chemotherapeutic candidate in glioblastoma therapy warranting further translational evaluation

A novel HSP-90 inhibitor with highly selective activity against papillary and anaplastic thyroid cancers

Background HSP90 is a chaperone protein regulating several client proteins involved in thyroid cancer development. The purpose of this study is to mechanisticially evaluate a novel natural-product HSP90 inhibitor in thyroid cancer cell lines for future translational applications. Methods 285 plant-extracts/compounds were evaluated for anti-cancer activity by MTS assay. Apoptosis and cell-cycle-arrest were characterized by annexinV-PI flow cytometry. HSP90 and client-protein inhibition along with apoptosis confirmation was demonstrated by Western blot analysis. Results 45 of 285extracts/compounds demonstrated anti-proliferative activity in thyroid cancers by MTS assay. BTIMNP_D004 demonstrated the highest inhibition [IC50(NPA)=0.19±0.02mM, IC50(DRO)=0.26±0.03mM]vs. 17-AAG [IC50(NPA)=0.51±0.02mM; IC50(DRO)=0.75±0.04mM;p<0.001]. D004 induced cell-cycle-arrest after 18hours (G1/G0→S and G2/M) with 26%DRO cells shifted and 23%NPA cells shifted vs. controls (p<0.001 and <0.01 respectively). 1mM D004 induced significant apoptosis with 76%DRO cells gated after 18hrs. (Annexin V/PI staining) vs <2% in controls;p<0.001 and 80%NPA cells vs. 4%controls(p<0.001). Western analysis demonstrated inhibition of HSP90, HSF-1, AKT, and cleavage of procaspase3 and PARP in both NPA and DRO cells. Conclusion BTIMNP_D004 is a potent, novel HSP90inhibitor with selective activity against papillary and anaplastic thyroid cancers through modulation of client proteins, induction of apoptosis and cell cycle arrest. These data support future pre-clinical studies for translational applications

Novel C-Terminal Hsp90 Inhibitor for Head and Neck Squamous Cell Cancer (HNSCC) with in vivo Efficacy and Improved Toxicity Profiles Compared with Standard Agents

The final publication is available at Springer via http://dx.doi.org/10.1245/s10434-011-1971-1.Background - Current therapies for HNSCC, especially platinum agents, are limited by their toxicities and drug resistance. This study evaluates a novel C-terminal Hsp90 inhibitor (CT-Hsp90-I) for efficacy and toxicity in vitro and in vivo in an orthotopic HNSCC model. Our hypothesis is that C-terminal inhibitors exhibit improved toxicity/efficacy profiles over standard therapies and may represent a novel group of anticancer agents. Methods - MDA-1986 HNSCC cells were treated with doses of 17-AAG or KU363 (a CT-Hsp90-I) and compared for antiproliferation by GLO-Titer and trypan blue exclusion and for apoptosis by PARP cleavage and caspase-3 inactivation by Western analysis. In vivo studies in Nu/Nu mice examined an orthotopic model of MDA-1986 cells followed by drug dosing intraperitoneally for a 21-day period (mg/kg/dose: cisplatin = 3.5, low-dose KU363 = 5, high-dose KU363 = 25, 17-AAG = 175). Tumor size, weight, and toxicity (body score) were measured 3×/week. Results - The IC50 levels for KU363 = 1.2–2 μM in MDA-1986. KU363 induces apoptosis at 1 μM with cleavage of PARP and inactivation of caspase-3 levels after 24 h. Client proteins Akt and Raf-1 were also downregulated at 1–3 μM of drug. In vivo, 100% of controls had progressive disease, while 100% of cisplatin animals showed some response, all with significant systemic toxicity. High-dose KU363 showed 88% of animals responding and low-dose KU363 showed 75% responding. KU363 animals showed significantly less toxicity (P < 0.01) than cisplatin or 17-AAG. Conclusion - This novel CT-Hsp90-I KU363 manifests potent anticancer activity against HNSCC, showing excellent in vivo efficacy and reduced toxicity compared with standard agents justifying future translational evaluation

A novel C-terminal HSP90 inhibitor KU135 induces apoptosis and cell cycle arrest in melanoma cells

Heat shock protein 90 (Hsp90) is differentially expressed in tumor cells including melanoma and involved in proper folding, stabilization and regulation of cellular proteins. We investigated a novobiocin-derived Hsp90 C-terminal inhibitor, KU135, for anti-proliferative effects in melanoma cells. The results indicate that KU135 reduced cell viability and cell proliferation in melanoma cells and IC50 values for A735(DRO), M14(NPA), B16F10 and SKMEL28 cells were 0.82, 0.92, 1.33 and 1.30 M respectively. KU135 induced a more potent anti-proliferative effect in most melanoma cells versus N-terminal Hsp90 inhibitor 17AAG. KU135 induced apoptosis in melanoma cells, as indicated by annexin V/PI staining, reduction in the mitochondrial membrane potential, mitochondrial cytochrome C release and caspase 3 activation. KU135 reduced levels of Hsp90 client proteins Akt, BRAF, RAF-1, cyclin B and cdc25 proteins. Additionally, it reduced Hsp70, Hsp90 paralog, GRP94 and HSF1 levels. KU135 induced strong G2/M cell cycle arrest, associated with decreased expression of cdc25c, cyclin B and increased phosphorylation of cdc25c. These finding show that KU135 reduced cell survival, proliferation, and induces apoptosis in melanoma cells. We suggest that KU135 may be a potential candidate for cancer therapy against melanoma

Novel withanolides target medullary thyroid cancer through inhibition of both RET phosphorylation and the mammalian target of rapamycin pathway

Background Despite development of current targeted therapies for medullary thyroid cancer (MTC), long-term survival remains unchanged. Recently isolated novel withanolide compounds from Solanaceae physalis are highly potent against MTCs. We hypothesize that these withanolides uniquely inhibit RET phosphorylation and the mammalian target of rapamycin (mTOR) pathway in MTC cells as a mechanism of antiproliferation and apoptosis. Methods MTC cells were treated with novel withanolides and MTC-targeted drugs. In vitro studies assessed cell viability and proliferation (MTS; trypan blue assays), apoptosis (flow cytometry with Annexin V/PI staining; confirmed by Western blot analysis), long-term cytotoxic effects (clonogenic assay), and suppression of key regulatory proteins such as RET, Akt, and mTOR (by Western blot analysis). Results The novel withanolides potently reduced MTC cell viability (half maximal inhibitory concentration [IC50], 270–2,850 nmol/L; 250–1,380 nmol/L for vandetanib; 360–1,640 nmol/L for cabozantinib) with induction of apoptosis at <1,000 nmol/L of drug. Unique from other targeted therapies, withanolides suppressed RET and Akt phosphorylation and protein expression (in a concentration- and time-dependent manner) as well as mTOR activity and translational activity of 4E-BP1 and protein synthesis mediated by p70S6kinase activation at IC50 concentrations. Conclusion Novel withanolides from Physalis selectively and potently inhibit MTC cells in vitro. Unlike other MTC-targeted therapies, these compounds uniquely inhibit both RET kinase activity and the Akt/mTOR prosurvival pathway. Further translational studies are warranted to evaluate their clinical potential