Designing a broad-spectrum integrative approach for cancer prevention and treatment

Targeted therapies and the consequent adoption of "personalized" oncology have achieved notable successes in some cancers; however, significant problems remain with this approach. Many targeted therapies are highly toxic, costs are extremely high, and most patients experience relapse after a few disease-free months. Relapses arise from genetic heterogeneity in tumors, which harbor therapy-resistant immortalized cells that have adopted alternate and compensatory pathways (i.e., pathways that are not reliant upon the same mechanisms as those which have been targeted). To address these limitations, an international task force of 180 scientists was assembled to explore the concept of a low-toxicity "broad-spectrum" therapeutic approach that could simultaneously target many key pathways and mechanisms. Using cancer hallmark phenotypes and the tumor microenvironment to account for the various aspects of relevant cancer biology, interdisciplinary teams reviewed each hallmark area and nominated a wide range of high-priority targets (74 in total) that could be modified to improve patient outcomes. For these targets, corresponding low-toxicity therapeutic approaches were then suggested, many of which were phytochemicals. Proposed actions on each target and all of the approaches were further reviewed for known effects on other hallmark areas and the tumor microenvironment. Potential contrary or procarcinogenic effects were found for 3.9% of the relationships between targets and hallmarks, and mixed evidence of complementary and contrary relationships was found for 7.1%. Approximately 67% of the relationships revealed potentially complementary effects, and the remainder had no known relationship. Among the approaches, 1.1% had contrary, 2.8% had mixed and 62.1% had complementary relationships. These results suggest that a broad-spectrum approach should be feasible from a safety standpoint. This novel approach has potential to be relatively inexpensive, it should help us address stages and types of cancer that lack conventional treatment, and it may reduce relapse risks. A proposed agenda for future research is offered.

Broad targeting of resistance to apoptosis in cancer

Apoptosis or programmed cell death is natural way of removing aged cells from the body. Most of the anti-cancer therapies trigger apoptosis induction and related cell death networks to eliminate malignant cells. However, in cancer, de-regulated apoptotic signaling, particularly the activation of an anti-apoptotic systems, allows cancer cells to escape this program leading to uncontrolled proliferation resulting in tumor survival, therapeutic resistance and recurrence of cancer. This resistance is a complicated phenomenon that emanates from the interactions of various molecules and signaling pathways. In this comprehensive review we discuss the various factors contributing to apoptosis resistance in cancers. The key resistance targets that are discussed include (1) Bcl-2 and Mcl-1 proteins; (2) autophagy processes; (3) necrosis and necroptosis; (4) heat shock protein signaling; (5) the proteasome pathway; (6) epigenetic mechanisms; and (7) aberrant nuclear export signaling. The shortcomings of current therapeutic modalities are highlighted and a broad spectrum strategy using approaches including (a) gossypol; (b) epigallocatechin-3-gallate; (c) UMI-77 (d) triptolide and (e) selinexor that can be used to overcome cell death resistance is presented. This review provides a roadmap for the design of successful anti-cancer strategies that overcome resistance to apoptosis for better therapeutic outcome in patients with cancer.

A multi-targeted approach to suppress tumor-promoting inflammation

Cancers harbor significant genetic heterogeneity and patterns of relapse following many therapies are due to evolved resistance to treatment. While efforts have been made to combine targeted therapies, significant levels of toxicity have stymied efforts to effectively treat cancer with multi-drug combinations using currently approved therapeutics. We discuss the relationship between tumor-promoting inflammation and cancer as part of a larger effort to develop a broad-spectrum therapeutic approach aimed at a wide range of targets to address this heterogeneity. Specifically, macrophage migration inhibitory factor, cyclooxygenase-2, transcription factor nuclear factor-κB, tumor necrosis factor alpha, inducible nitric oxide synthase, protein kinase B, and CXC chemokines are reviewed as important antiinflammatory targets while curcumin, resveratrol, epigallocatechin gallate, genistein, lycopene, and anthocyanins are reviewed as low-cost, low toxicity means by which these targets might all be reached simultaneously. Future translational work will need to assess the resulting synergies of rationally designed antiinflammatory mixtures (employing low-toxicity constituents), and then combine this with similar approaches targeting the most important pathways across the range of cancer hallmark phenotypes.

A novel combination of withaferin A and sorafenib shows synergistic efficacy against both papillary and anaplastic thyroid cancers

BACKGROUND

Sorafenib (SO), a multikinase-targeted inhibitor in clinical trials for papillary and anaplastic cancers, shows limited efficacy with moderate toxicity. Withaferin A (WA), a natural withanolide, shows potent preclinical anticancer activity in thyroid cancers through multiple cytotoxic mechanisms including heat-shock protein inhibition. We hypothesized that combination therapy (WA + SO) would have a synergistic effect against anaplastic and papillary carcinoma cells at lower sorafenib doses.

METHODS

Human papillary (BCPAP) and anaplastic (SW1736) thyroid cancer cell lines were evaluated after treatment with SO, WA, or their combination at different doses. Proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and trypan blue exclusion; apoptosis and cell-cycle arrest was measured by flow cytometry. Western analysis confirmed apoptosis (Poly ADP ribose polymerase [PARP] and caspase-3 cleavage) and Raf inhibition. Experiments were repeated in triplicate and were evaluated statistically with significance set at a P value of less than .05.

RESULTS

The concentration of drug at which 50% of the cells are inhibited (IC(50)) in BCPAP were 6.3 μmol/L (SO), .155 μmol/L (WA), and .055 μmol/L (IC(50)WA + 50% IC(50)SO), whereas in SW1736 cells the concentration was 7.6 μmol/L (SO), 2.5 μmol/L (WA), and 1.4 μmol/L (IC(50)WA + 50% IC(50)SO). Combination (WA + SO) at IC(50) decreased cell viability to 19% (from 50% individually). Apoptosis levels on flow cytometry in anaplastic cells increased significantly from 0% to 2% (SO or WA alone) to 89% (combo at IC(50), P < .001). Combination therapy apoptosis (PARP cleavage and caspase-3 inactivation) and BRAF/Raf-1 down-regulation were dose-dependent starting at 50% IC(50) levels. Cell-cycle modulation was significant with combination treatment (35% increase in G2 arrest at 50% IC(50)SO + WA and 70% increase at 75% IC(50)SO + WA; P < .01).

CONCLUSIONS

Combination therapy with sorafenib + withaferin showed synergistic efficacy in papillary and anaplastic cancers in vitro with significant induction of apoptosis. This combination achieved potent anticancer activity with lower overall doses of sorafenib, indicating a potential strategy to decrease sorafenib toxicity in future translational studies.

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 [IC(50)], 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 IC(50) 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.

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-cysteine-repressible 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.

Withaferin a induces proteasome-dependent degradation of breast cancer susceptibility gene 1 and heat shock factor 1 proteins in breast cancer cells

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

As part of our search for bioactive compounds from plant biodiversity, 29 withanolides (1, 3-6, 9, 12-18, and 20-35) were recently isolated from three members of the Solanaceae: Physalis longifolia, Vassobia breviflora, and Withania somnifera. Six derivatives (2, 7, 8, 10, 11, and 19) were prepared from these naturally occurring withanolides. All compounds (1-35) were evaluated for in vitro anti-proliferative 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 1, withaferin A 4,27-diacetate 2, 27-O-glucopyranosylwithaferin A 3, withalongolide H 4, withalongolide C 5, withalongolide A 6, withalongolide A 4,27-diacetate 7, withalongolide A 4,19,27-triacetate 8, withalongolide B 9, withalongolide B 4-acetate 10, withalongolide B 4,19-diacetate 11, withalongolide D 16, withalongolide E 17, withalongolide G 21, and 2,3-dihydrowithaferin A 3-O-sulfate 22). In order to update the growing literature on withanolides and their activities, we summarized the distribution, structural types and anti-proliferative activities for all published withanolides to date. The structure-activity relationship analysis (SARA) confirmed the importance of the presence of a Δ2-1-oxo- functionality in ring A, a 5β,6β-epoxy or 5α-chloro-6β-hydroxy groupings 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, 28 were not contributors to the observed anti-proliferative activity within the systems analyzed.

Cytotoxic withanolide constituents of Physalis longifolia

Fourteen new withanolides, 1-14, named withalongolides A-N, respectively, were isolated from the aerial parts of Physalis longifolia together with eight known compounds (15-22). The structures of compounds 1-14 were elucidated through spectroscopic techniques and chemical methods. In addition, the structures of withanolides 1, 2, 3, and 6 were confirmed by X-ray crystallographic analysis. Using a MTS viability assay, eight withanolides (1, 2, 3, 7, 8, 15, 16, and 19) and four acetylated derivatives (1a, 1b, 2a, and 2b) showed potent cytotoxicity against human head and neck squamous cell carcinoma (JMAR and MDA-1986), melanoma (B16F10 and SKMEL-28), and normal fetal fibroblast (MRC-5) cells with IC₅₀ values in the range between 0.067 and 9.3 μM.

Inhibition of cell growth and induction of apoptosis in ovarian carcinoma cell lines CaOV3 and SKOV3 by natural withanolide Withaferin A

OBJECTIVE

Withaferin A, a natural withanolide, has shown anti-cancer properties in various cancers including breast cancer, but its effects in ovarian cancer remain unexplored. Notch 1 and Notch3 are critically involved in ovarian cancer progression. We decided to examine the effects of Withaferin A in ovarian carcinoma cell lines and its molecular mechanism of action including its regulation of Notch.

METHODS

The effects of Withaferin A were examined in CaOV3 and SKOV3 ovarian carcinoma cell lines using MTS assay, clonogenic assay, annexin V/propidium iodide flow cytometry, and cell cycle analysis. Western analysis was conducted to examine the molecular mechanisms of action.

RESULTS

Withaferin A inhibited the growth and colony formation of CaOV3 and SKOV3 cells by inducing apoptosis and cell cycle arrest. These changes correlated with down-regulation of Notch1, Notch3, cdc25C, total and phosphorylated Akt, and bcl-2 proteins.

CONCLUSIONS

Withaferin A inhibits CaOV3 and SKOV3 ovarian carcinoma cell growth, at least in part by targeting Notch1 and Notch3.

Down-regulation of estrogen receptor-alpha and rearranged during transfection tyrosine kinase is associated with withaferin a-induced apoptosis in MCF-7 breast cancer cells

BACKGROUND

Withaferin A (WA), a naturally occurring withanolide, induces apoptosis in both estrogen-responsive MCF-7 and estrogen-independent MDA-MB-231 breast cancer cell lines with higher sensitivity in MCF-7 cells, but the underlying mechanisms are not well defined. The purpose of this study was to determine the anti-cancer effects of WA in MCF-7 breast cancer cells and explore alterations in estrogen receptor alpha (ERα) and its associated molecules in vitro as novel mechanisms of WA action.

METHODS

The effects of WA on MCF-7 viability and proliferation were evaluated by 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and trypan blue exclusion assays. Apoptosis was evaluated by Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) flow cytometry and Western blot analysis of poly (ADP-ribose) polymerase (PARP) cleavage. Cell cycle effects were analyzed by PI flow cytometry. Western blotting was also conducted to examine alterations in the expression of ERα and pathways that are associated with ERα function.

RESULTS

WA resulted in growth inhibition and decreased viability in MCF-7 cells with an IC50 of 576 nM for 72 h. It also caused a dose- and time-dependent apoptosis and G2/M cell cycle arrest. WA-induced apoptosis was associated with down-regulation of ERα, REarranged during Transfection (RET) tyrosine kinase, and heat shock factor-1 (HSF1), as well as up-regulation of phosphorylated p38 mitogen-activated protein kinase (phospho-p38 MAPK), p53 and p21 protein expression. Co-treatment with protein synthesis inhibitor cycloheximide or proteasome inhibitor MG132 revealed that depletion of ERα by WA is post-translational, due to proteasome-dependent ERα degradation.

CONCLUSIONS

Taken together, down-regulation of ERα, RET, HSF1 and up-regulation of phospho-p38 MAPK, p53, p21 are involved in the pro-apoptotic and growth-inhibitory effects of WA in MCF-7 breast cancer cells in vitro. Down-regulation of ERα protein levels by WA is caused by proteasome-dependent ERα degradation.

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 IC(50) values for A735(DRO), M14(NPA), B16F10 and SKMEL28 cells were 0.82, 0.92, 1.33 and 1.30μM 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. Additionally, levels of Hsp90 and Hsp70 did not increase, while the levels of phosphorylated HSF1 levels decreased. 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 C-terminal Hsp90 inhibitor for head and neck squamous cell cancer (HNSCC) with in vivo efficacy and improved toxicity profiles compared with standard agents

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 IC(50) 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.

Cytotoxic oleanane-type saponins from Albizia inundata

Bioassay-guided fractionation of a CH(2)Cl(2)-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 ((1)H-(1)H 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 IC(50) values in the range 1.8-12.4 μM, using the MTS assay.

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

BACKGROUND

Most medullary thyroid carcinomas (MTC) recur or progress despite curative resection. Current targeted therapies show promise but lack durable efficacy and tolerability. The purpose of this study was to build on previous in vitro work and evaluate withaferin A (WA), a novel RET inhibitor, in a metastatic murine model of MTC.

METHODS

A total of 5 million DRO-81-1 human MTC cells injected in the left posterior neck of nu/nu mice generated metastases uniformly to the liver, spleen, and/or lungs. Treatment with WA (8 mg/kg/day, intraperitoneally, for 21 days) was started for neoplasms > 100 mm(3). Endpoints were survival, neoplasm > 15,00 mm(3), decreased body weight, or body score (all measured three times/wk).

RESULTS

All controls (saline; n = 5) died or deteriorated from metastatic disease by 7 weeks postinjection. All treated animals were alive (WA; n = 5), having tumor regression and growth delay without toxicity or weight loss at 6 weeks posttreatment (P < .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 treatment of 5 μM WA) as well as potent inhibition of phospho-ERK and phospho-Akt levels.

CONCLUSION

WA 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.

Withaferin A, a cytotoxic steroid from Vassobia breviflora, 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% (IC(50)) were determined by the MTS cytotoxicity assay, and 1 reduced cell viability with IC(50) 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 G(0)/G(1) to G(2)/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.

Growth of melanoma brain tumors monitored by photoacoustic microscopy

Melanoma is a primary malignancy that is known to metastasize to the brain and often causes death. The ability to image the growth of brain melanoma in vivo can provide new insights into its evolution and response to therapies. In our study, we use a reflection mode photoacoustic microscopy (PAM) system to detect the growth of melanoma brain tumor in a small animal model. The melanoma tumor cells are implanted in the brain of a mouse at the beginning of the test. Then, PAM is used to scan the region of implantation in the mouse brain, and the growth of the melanoma is monitored until the death of the animal. It is demonstrated that PAM is capable of detecting and monitoring the brain melanoma growth noninvasively in vivo.

Abstract A214: A novobiocin analogue HSP90 inhibitor induces apoptosis and has potent antitumor effects in head and neck squamous cell cancer in vivo

Introduction: Small molecule n-terminal inhibitors of heat shock protein 90 (HSP90i) have been evaluated as anticancer agents in various stages of human clinical trials. This study evaluates a novel C-terminal HSP90 inhibitor derived as an analogue of novobiocin for its anti-tumor activity against head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo.

Methods: Head and neck squamous cell carcinoma cells MDA1986 and JMAR were used to examine the efficacy of KU174 as an anti-cancer agent. Cell viability assay MTS and cell proliferation analysis were used to examine the concentration-dependent effect of KU174 on HNSCC cells. Cells were stained with propidium iodide and evaluated on flow cytometry (FC) to study the effects on cell cycle progression. Analysis of KU174 - induced apoptosis of HNSCC was evaluated first by annexin V/PI staining on FC after treatment with drug and confirmed by Western blot analysis for caspase activation and PARP cleavage. KU174 - induced modulation of kinases Akt and ERK1/2 was studied using Western blot analysis for levels of protein expression following treatment. Finally in vivo efficacy of KU174 was evaluated in an orthotopic mouse model of HNSCC following 3 weeks of daily i.p. injection with 5 mg/kg/d of drug.

Results: KU174 inhibited cell viability in both MDA1986 and JMAR cells (IC50 = 7.5 and 4.3 M respectively; novobiocin IC50&gt;700 M for each; p&lt;0.01). In addition, treatment of JMAR and MDA1986 cells by KU174 induced a 30% shift from G0/G1 arrest to G2/M cell cycle arrest. Cells treated with KU174 strongly stained with annexin V/PI indicating induction of apoptosis in these cells, quantitatively measured on FC at 80% with &lt;3% necrosis. Apoptosis was confirmed by Western blot analysis demonstrating induced activation of caspase 3 and cleavage of PARP substrate in MDA1986 cells treated with KU174. HSP90 levels are reduced with drug treatment and both cell lines demonstrated downregulation of Akt activation without significant activation of ERK1/2. In vivo efficacy analysis demonstrates an 80% response rate with a 60% sustained complete response with treatment. Ex vivo immunohistochemistry staining indicate caspase 3 cleavage in animal tumor cells validating the role of apoptosis induction by this inhibitor.

Conclusion: These results show that the c-terminal HSP90 inhibitor KU174 is significantly more potent in antiproliferative activity in HNSCC cells than its parent compound novobiocin. Mechanistic studies suggest that the HNSCC cells treated with KU174 are likely dying by a combination of apoptosis, cell cycle arrest and modulation of proteins such as prosurvival kinases chaperoned by HSP90. Additionally this compound has potent antitumor efficacy in an orthotopic mouse model of HNSCC in vivo lending support for future preclinical proof-of-concept studies to translate its application as a potential human therapy in HNSCC.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A214.

Abstract B84: Withaferin-A is a novel HSF-1 inhibitor with potent antitumor effects in melanoma in vivo

Introduction: Withaferin A (WA) is a natural product withanolide compound with historical anti-inflammatory activity and recent anticancer activity in vitro. The purpose of this study was to evaluate the mechanism of action of withaferin A in melanoma cancer cells and test its efficacy in a murine orthotopic model of metastatic melanoma.

Methods: Human melanoma cells lines SKMEL28, NPA, DRO and the murine B16F10 cell line were used for in vitro analysis. MTS cell viability assay and cell proliferation analysis was performed to determine the concentration-dependent effect of withaferin A on melanoma cells. Effects on cell cycle arrest and apoptosis were evaluated by PI/Annexin V staining with flow cytometry and confirmed through Western analysis. MAPkinase and heat shock protein expression after WA treatment was evaluated by Western analysis. Inhibitors of MEK1/2, JNK and p38 MAP kinase were used to examine the relationship between WA-mediated MAPkinase protein expression and modulation of heat shock proteins. In vivo analysis was performed on BalbC mice injected s.c. with 5 million B16F10 melanoma cells, allowing tumors to grow and metastasize. Treatment was with 5mg/kg/d WA i.p. for 3 weeks. Tumor growth and survival was followed prospectively. In vitro and in vivo variables were statistically evaluated using SPSS 17.0 software and significance was defined for p&lt;0.05.

Results: Withaferin A induces reduction of cell viability and cell proliferation in all melanoma cell lines tested [Range of IC50(B16F10 =209.7±16nM); (SKMEL-28=650.1 ±25nM)]. Mechanistic studies demonstrate that WA induced a cell cycle shift from G0/G1 arrest to G2/M arrest in all melanoma cells lines tested. Annexin V /PI staining on FC as well as caspase activation and PARP cleavage on Western studies confirm that WA induces apoptosis in melanoma cells. WA reduced p-Akt levels and total Akt levels in all cell lines tested in a concentration and time-dependent manner. Withaferin A modulates MAP kinase proteins, inducing activation of p-ERK1/2 , p38 MAPkinase and SAPK/JNK in all melanoma cell lines. HSP expression analysis yielded strong induction of HSP72 expression in all cell lines, reduction of HSP90 in SKMEL28 cells, and strong reduction of HSF1 cellular levels in a dose dependant manner with almost complete reduction at IC50 concentrations. Confocal microscopy analysis showed that withaferin A-induced expression of HSP72 was increased in the cytoplasm and that HSP72 was transported to the nucleus upon withaferin A stimulation. In vivo studies demonstrate almost complete tumor regression with CR in 80% of animals treated with 5 mg/kg/day WA compared to controls (p&lt;0.01). Additionally at 5/mg/kg dosing, there was complete reversal of organ and lymphatic metastatic disease by inspection after 3 weeks treatment in the 80% of animals responding without progression once the treatment was discontinued.

Conclusion: Our present results show that withaferin A is a potent therapy against melanoma cells in vitro and in vivo through induction of cell cycle arrest, apoptosis, and modulation of MAPkinase and HSP expression. This is the first report of inhibition of HSF1 expression in cancer cells induced by withaferin A treatment. These results support future proof of concept studies for translation to potential therapies for melanoma patients.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B84.