Molecular mechanisms of deguelin-induced apoptosis in transformed human bronchial epithelial cells

Discovery of indazole inhibitors for heat shock protein 90 as anti-cancer agents

A series of indazole analogs, derived from the B,C-ring-truncated scaffold of deguelin, were designed to function as C-terminal inhibitors of heat shock protein 90 (HSP90) and investigated as novel antitumor agents against HER2-positive breast cancer. Among the synthesized compounds, compound 12d exhibited substantial inhibitory effects in trastuzumab-sensitive (BT474) and trastuzumab-resistant (JIMT-1) breast cancer cells, with IC50 values of 6.86 and 4.42 μM, respectively. Notably, compound 12d exhibited no cytotoxicity in normal cells. Compound 12d markedly downregulated the expression of the major HSP90 client proteins in both cell types, attributing its cytotoxicity to the destabilization and inactivation of HSP90 client proteins. Molecular docking studies using the homology model of an HSP90 homodimer demonstrated that inhibitor 12d fit nicely into the C-terminal domain, boasting a higher electrostatic complementary score than ATP. In vivo pharmacokinetic study indicated the high oral bioavailability of compound 12 d at F = 66.9 %, while toxicological studies indicated its negligible impact on hERG channels and CYP isozymes. Genotoxicity tests further confirmed its safety profile. The findings collectively position compound 12d as a promising candidate for further development as an antitumor agent against HER2-positive breast cancer.

Could Targeting NPM1c+ Misfolding Be a Promising Strategy for Combating Acute Myeloid Leukemia?

Acute myeloid leukemia (AML) is a heterogeneous group of diseases classified into various types on the basis of distinct features concerning the morphology, cytochemistry and cytogenesis of leukemic cells. Among the different subtypes, the group "AML with gene mutations" includes the variations of the gene of the multifunctional protein nucleophosmin 1 (NPM1). These mutations are the most frequent (~30-35% of AML adult patients and less in pediatric ones) and occur predominantly in the C-terminal domain (CTD) of NPM1. The most important mutation is the insertion at W288, which determines the frame shift W288Cfs12/Ffs12/Lfs*12 and leads to the addition of 2-12 amino acids, which hamper the correct folding of NPM1. This mutation leads to the loss of the nuclear localization signal (NoLS) and to aberrant cytoplasmic localization, denoted as NPM1c+. Many investigations demonstrated that interfering with the cellular location and oligomerization status of NPM1 can influence its biological functions, including the proper buildup of the nucleolus, and therapeutic strategies have been proposed to target NPM1c+, particularly the use of drugs able to re-direct NPM1 localization. Our studies unveiled a direct link between AML mutations and the neat amyloidogenic character of the CTDs of NPM1c+. Herein, with the aim of exploiting these conformational features, novel therapeutic strategies are proposed that rely on the induction of the selective self-cytotoxicity of leukemic blasts by focusing on agents such as peptides, peptoids or small molecules able to enhance amyloid aggregation and targeting selectively AML-NPM1c+ mutations.

Syntheses and antitumor activities of neorautenol and shinpterocarpin analogs

The natural products neorautenol and shinpterocarpin and their structural analogs were investigated as novel anticancer agents. Twenty-four analogs, including analogs containing a polar chain and simplified analogs, were synthesized efficiently by a modified method from previous reports. The antitumor screening of synthesized compounds toward six cancer cell lines indicated that compounds 37, 42 and 43 with a dialkylaminoethyl-type side chain exhibited more promising activity than neorautenol and shinpterocarpin against lung and colon cancer lines with a range of 4-9 μM. They showed selective toxicity in normal cells.

Metabolic exhaustion and casein kinase 1α drive deguelin-induced premature red blood cell death

1. Deguelin (DGN), a retinoid isolated from many plants, exhibits a potent anticancer activity against a wide spectrum of tumour cells. There is a dearth of evidence, however, regarding the toxicity of DGN to red blood cells (RBCs). This is relevant given the prevalent chemotherapy-associated anaemia observed in cancer patients.2. RBCs were exposed to 1-100 μM of DGN for 24 h at 37 °C. Haemolysis and related markers were photometrically measured while flow cytometry was employed to detect phosphatidylserine exposure through Annexin-V-FITC binding and light scatter properties. Additionally, cytosolic Ca2+ and reactive oxygen species were quantified using Fluo4/AM and H2DCFDA, respectively. DGN was also tested against specific signalling inhibitors in addition to vitamin C and ATP.3. DGN caused a significant increase in Annexin-V-positive cells which was accompanied by cell shrinkage without Ca2+ elevation or oxidative stress. DGN also elicited dose-responsive haemolysis which was ameliorated by preventing KCl efflux and in the presence of sucrose, D4476, and ATP. In whole blood, DGN significantly reduced the reticulocyte count and increased platelet distribution width and large cell count.4. DGN triggers premature RBC eryptosis and haemolysis through casein kinase 1α and ATP depletion, and exhibits a specific toxicity towards reticulocytes and platelets.

Pharmacological basis and new insights of deguelin concerning its anticancer effects

Deguelin is a rotenoid of the flavonoid family, which can be extracted from Lonchocarpus, Derris, or Tephrosia. It possesses the inhibition of cancer cell proliferation by inducing apoptosis through regulating the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling pathway, the NF-κB signaling pathway, the Wnt signaling pathway, the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway and epidermal growth factor receptor (EGFR) signaling, activating the p38 mitogen-activated protein kinase (MAPK) pathway, repression of Bmi1, targeting cyclooxygenase-2 (COX-2), targeting galectin-1, promotion of glycogen synthase kinase-3β (GSK3β)/FBW7-mediated Mcl-1 destabilization and targeting mitochondria via down-regulating Hexokinases II-mediated glycolysis, PUMA-mediation, which are some crucial molecules which modulate closely cancer cell growth and metastasis. Deguelin inhibits tumor cell propagation and malignant transformation through targeting angiogenesis, targeting lymphangiogenesis, targeting focal adhesion kinase (FAK), inhibiting the CtsZ/FAK signaling pathway, targeting epithelial-mesenchymal transition (EMT), the NF-κB signaling pathway, regulating NIMA-related kinase 2 (NEK2). In addition, deguelin possesses other biological activities, such as targeting cell cycle arrest, modulation of autophagy, inhibition of hedgehog pathway, inducing differentiation of mutated NPM1 acute myeloid leukemia etc. Therefore, deguelin is a promising chemopreventive agent for cancer therapy.

The disruption of protein-protein interactions with co-chaperones and client substrates as a strategy towards Hsp90 inhibition

The 90-kiloDalton (kD) heat shock protein (Hsp90) is a ubiquitous, ATP-dependent molecular chaperone whose primary function is to ensure the proper folding of several hundred client protein substrates. Because many of these clients are overexpressed or become mutated during cancer progression, Hsp90 inhibition has been pursued as a potential strategy for cancer as one can target multiple oncoproteins and signaling pathways simultaneously. The first discovered Hsp90 inhibitors, geldanamycin and radicicol, function by competitively binding to Hsp90's N-terminal binding site and inhibiting its ATPase activity. However, most of these N-terminal inhibitors exhibited detrimental activities during clinical evaluation due to induction of the pro-survival heat shock response as well as poor selectivity amongst the four isoforms. Consequently, alternative approaches to Hsp90 inhibition have been pursued and include C-terminal inhibition, isoform-selective inhibition, and the disruption of Hsp90 protein-protein interactions. Since the Hsp90 protein folding cycle requires the assembly of Hsp90 into a large heteroprotein complex, along with various co-chaperones and immunophilins, the development of small molecules that prevent assembly of the complex offers an alternative method of Hsp90 inhibition.

Discovery of a simplified deguelin analog as an HSP90 C-terminal inhibitor for HER2-positive breast cancer

A series of O-substituted analogs of the C-ring-truncated scaffold of deguelin designed as heat shock protein 90 (HSP90) C-terminal inhibitors were investigated as novel antitumor agents against human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Among the synthesized compounds, compound 37 displayed significant inhibition in both trastuzumab-sensitive and trastuzumab-resistant breast cancer cells with little cytotoxicity to normal cells. Mechanistic studies of compound 37 carried out by HSP90α C-terminal inhibitor screening, the induction of the heat shock response and downregulation of HSP90 client proteins indicated that the antitumor activity of 37 in breast cancer cells could be attributed to the destabilization and inactivation of HSP90 client proteins by the binding of 37 to the C-terminal domain of HSP90. A molecular docking study of compound 37 with a HSP90 homology model indicated that its S-isomer fit well in the ATP binding site of the C-terminal domain, forming key interactions.

Perspectives on natural compounds in chemoprevention and treatment of cancer: an update with new promising compounds

Cancer is the second deadliest disease worldwide. Although recent advances applying precision treatments with targeted (molecular and immune) agents are promising, the histological and molecular heterogeneity of cancer cells and huge mutational burdens (intrinsic or acquired after therapy) leading to drug resistance and treatment failure are posing continuous challenges. These recent advances do not negate the need for alternative approaches such as chemoprevention, the pharmacological approach to reverse, suppress or prevent the initial phases of carcinogenesis or the progression of premalignant cells to invasive disease by using non-toxic agents. Although data are limited, the success of several clinical trials in preventing cancer in high-risk populations suggests that chemoprevention is a rational, appealing and viable strategy to prevent carcinogenesis. Particularly among higher-risk groups, the use of safe, non-toxic agents is the utmost consideration because these individuals have not yet developed invasive disease. Natural dietary compounds present in fruits, vegetables and spices are especially attractive for chemoprevention and treatment because of their easy availability, high margin of safety, relatively low cost and widespread human consumption. Hundreds of such compounds have been widely investigated for chemoprevention and treatment in the last few decades. Previously, we reviewed the most widely studied natural compounds and their molecular mechanisms, which were highly exploited by the cancer research community. In the time since our initial review, many promising new compounds have been identified. In this review, we critically review these promising new natural compounds, their molecular targets and mechanisms of anticancer activity that may create novel opportunities for further design and conduct of preclinical and clinical studies.

Deguelin targets multiple oncogenic signaling pathways to combat human malignancies

Cancer is an anomalous growth and differentiation of cells known to be governed by oncogenic factors. Plant-based natural metabolites have been well recognized to possess chemopreventive properties. Deguelin, a natural rotenoid, is among the class of bioactive phytoconstituents from a diverse range of plants with potential antineoplastic effects in different cancer subtypes. However, the precise mechanisms of how deguelin inhibits tumor progression remains elusive. Deguelin has shown promising results in targeting the hallmarks of tumor progression via inducing tumor apoptosis, cell cycle arrest, and inhibition of angiogenesis and metastasis. Based on initial scientific excerpts, deguelin has been reported to inhibit tumor growth via different signaling pathways, including mitogen-activated protein kinase, phosphoinositide 3-kinase, serine/threonine protein kinase B (also known as Akt), mammalian target of rapamycin, nuclear factor-κB, matrix metalloproteinase (MMP)-2, MMP-9 and caspase-3, caspase-8, and caspase-9. This review summarizes the mechanistic insights of antineoplastic action of deguelin to gain a clear understanding of its therapeutic effects in cancer. The anticancer potential of deguelin with respect to its efficacy in targeting tumorigenesis via nanotechnological approaches is also investigated. The initial scientific findings have presented deguelin as a promising antitumorigenic agent which can be used for monotherapy as well as synergistically to augment efficacy of chemotherapeutic treatment regimes.

Discovery of novel anti-breast cancer agents derived from deguelin as inhibitors of heat shock protein 90 (HSP90)

A series of O-substituted analogues of the B,C-ring truncated scaffold of deguelin were designed as C-terminal inhibitors of heat shock protein 90 (HSP90) and investigated as novel antiproliferative agents against HER2-positive breast cancer. Among the synthesized compounds, compound 80 exhibited significant inhibition in both trastuzumab-sensitive and trastuzumab-resistant breast cancer cells, whereas compound 80 did not show any cytotoxicity in normal cells. Compound 80 markedly downregulated the expression of the major client proteins of HSP90 in both cell types, indicating that the cytotoxicity of 80 in breast cancer cells is attributed to the destabilization and inactivation of HSP90 client proteins and that HSP90 inhibition represents a promising strategy to overcome trastuzumab resistance. A molecular docking study of 80 with the homology model of a HSP90 homodimer showed that 80 fit nicely in the C-terminal domain with a higher electrostatic complementary score than that of ATP.

Akt inhibitor deguelin aggravates inflammation and fibrosis in myocarditis

OBJECTIVES

Myocarditis is characterized by inflammatory cell infiltration in myocardial stroma. Attenuation of tumor necrosis factor (TNF)-α and interleukin (IL)-1β is a reliable mark for improving the prognosis. Protein kinase B (Akt) plays an important role in the development and progression of myocarditis. The specific role of the natural inhibitor of Akt, Deguelin, on myocarditis has not been reported. In this study, we used deguelin to investigate the effects of natural Akt inhibitor on myocarditis in experimental autoimmune myocarditis (EAM) rats.

MATERIALS AND METHODS

EAM rat models were made by using Lewis rats and Deguelin was injected intraperitoneally on day 3, 6, 9, 12 and 15 after successful modeling. On day 18, rats were sacrificed and the heart weight (HW)/ body weight (BW) ratio were measured. The pathological changes, pathological scores and fibrosis area were evaluated after H.&E. and Masson's trichrome staining. The mRNA levels of TNF-α and IL-1β were measured by RT-qPCR, while the protein expressions of TNF-α and IL-1β were detected by immunohistochemical staining and Western bolt. The protein expressions of Akt, Akt1, phosphorylated (p-) Akt and nuclear factor (NF)-κB were detected by Western bolt.

RESULTS

We found that the TNF-α and IL-1β levels, inflammatory scores and fibrosis areas were markedly increased after 18 days deguelin administration.

CONCLUSION

Akt inhibition with deguelin may aggravate myocarditis of EAM rats.

An appraisal of natural products active against parasitic nematodes of animals

Here, the scientific and patent literature on the activities of purified natural compounds has been reviewed, with the aim of assessing their suitability as anthelmintic drug discovery starting points. Only compounds described as active against parasitic nematodes of animals or against the model nematode Caenorhabditis elegans have been analysed. Scientific articles published since 2010 and patents granted from 2000, both inclusive, have been included in this analysis. The results show a scarcity of novel chemical structures, a limited follow-up of compounds disclosed before 2010 and a bias towards the screening of plant products, almost to the exclusion of other sources, when microbial extracts have, historically, provided most starting points for anti-infective drugs. All plant products published in this period were previously known, alerting to the high re-discovery rates of a limited number of chemical classes from this source. The most promising compounds described in the literature reviewed here, namely the linear nemadectin-derivatives, are novel and of bacterial origin. Patented but otherwise unpublished spiroketal structures also appear as interesting scaffolds for future development. The patent literature confirmed that it is possible to patent derivatives of previously known products, making them valid starting points for translational research.

Stereocontrolled Semisyntheses of Elliptone and 12aβ-Hydroxyelliptone

Operationally simple, stereocontrolled semisyntheses of the anticancer rotenoids elliptone and 12aβ-hydroxyelliptone, isolated from Derris elliptica and Derris trifoliata, respectively, are described. Inspired by the work of Singhal, elliptone was prepared from rotenone via a dihydroxylation-oxidative cleavage, chemoselective Baeyer-Villiger oxidation, and acid-catalyzed elimination sequence. Elaboration of elliptone to 12aβ-hydroxyelliptone was achieved via a diastereoselective chromium-mediated Étard-like hydroxylation. The semisynthesis of elliptone constitutes an improvement over previous methods in terms of safety, scalability, and yield, while the first synthesis of 12aβ-hydroxyelliptone is also described.

Stereocontrolled semi-syntheses of deguelin and tephrosin

We describe stereocontrolled semi-syntheses of deguelin and tephrosin, anti-cancer rotenoids isolated from Tephrosia vogelii. Firstly, we present a new two-step transformation of rotenone into rot-2'-enonic acid via a zinc-mediated ring opening of rotenone hydrobromide. Secondly, following conversion of rot-2'-enonic acid into deguelin, a chromium-mediated hydroxylation provides tephrosin as a single diastereoisomer. An Étard-like reaction mechanism is proposed to account for the stereochemical outcome. Our syntheses of deguelin and tephrosin are operationally simple, scalable and high yielding, offering considerable advantages over previous methods.

A novel approach for the identification of efficient combination therapies in primary human acute myeloid leukemia specimens

Appropriate culture methods for the interrogation of primary leukemic samples were hitherto lacking and current assays for compound screening are not adapted for large-scale investigation of synergistic combinations. In this study, we report a novel approach that efficiently distills synthetic lethal interactions between small molecules active on primary human acute myeloid leukemia (AML) specimens. In single-dose experiments and under culture conditions preserving leukemia stem cell activity, our strategy considerably reduces the number of tests needed for the identification of promising compound combinations. Initially conducted with a selected library of 5000 small molecules and 20 primary AML specimens, it reveals 5 broad classes of sensitized therapeutic target pathways along with their synergistic patient-specific fingerprints. This novel method opens new avenues for the development of AML personalized therapeutics and may be generalized to other tumor types, for which in vitro cancer stem cell cultures have been developed.

Synthesis and biological evaluation of C-ring truncated deguelin derivatives as heat shock protein 90 (HSP90) inhibitors

Based on the lead compound L-80 (compound 2), a potent heat shock protein 90 (HSP90) inhibitor, a series of C-ring truncated deguelin analogs were designed, synthesized and evaluated for Hypoxia Inducible Factor-1α (HIF-1α) inhibition as a primary screening method. Their structure-activity relationship was investigated in a systematic manner by varying the A/B ring, linker and D/E ring, respectively. Among the synthesized inhibitors, compound 5 exhibited potent HIF-1α inhibition in a dose-dependent manner and significant antitumor activity in human non-small cell lung carcinoma (H1299), with better activities than L-80. It also inhibited in vitro hypoxia-mediated angiogenic processes in human retinal microvascular endothelial cells (HRMEC). The docking study of 5 showed a similar binding mode as L-80: it occupied the C-terminal ATP-binding pocket of HSP90, indicating that the anticancer and antiangiogenic activities of 5 were derived from HIF-1α destabilization by inhibiting the C-terminal ATP-binding site of hHSP90.

Deguelin-induced blockade of PI3K/protein kinase B/MAP kinase signaling in zebrafish and breast cancer cell lines is mediated by down-regulation of fibroblast growth factor receptor 4 activity

Deguelin, a natural component derived from leguminous plants, has been used as pesticide in some regions. Accumulating evidence show that deguelin has promising chemopreventive and therapeutic activities against cancer cells. This study shows that low concentrations of deguelin can lead to significant delay in zebrafish embryonic development through growth inhibition and induction of apoptosis. Furthermore, we identified fibroblast growth factor receptor 4 (FGFR4) as the putative target of deguelin. The candidate was initially identified by a microarray approach and then validated through in vitro experiments using hormone‐responsive (MCF‐7) and nonresponsive (MDA‐MB‐231) human breast cancer cell lines. The results show that deguelin suppressed cell proliferation and induced apoptosis in both cancer cell lines, but not in Hs 578Bst cells, by blocking PI3K/AKT and mitogen‐activated protein kinases (MAPK) signaling. The FGFR4 mRNA and protein level also diminished in a dose‐dependent manner. Interestingly, we found that forced FGFR4 overexpression attenuated deguelin‐induced proliferative suppression and apoptotic cell death in both zebrafish and MCF‐7 cell lines, p‐AKT and p‐ERK levels were restored upon FGFR4 overexpression. Taken together, our results strongly suggest that deguelin inhibition of PI3K/AKT and MAPK signaling in zebrafish and breast cancer cell lines is partially mediated through down‐regulation of FGFR4 activity.

Amelioration of an undesired action of deguelin

The pharmaceutical world has greatly benefited from the well-characterized structure-function relationships of toxins with endogenous biomolecules, such as ion-channels, receptors, and signaling molecules. Thus, therapeutics derived from toxins have been aggressively pursued. However, the multifunctional role of various toxins may lead to undesirable off-target effects, hindering their use as therapeutic agents. In this paper, we suggest that previously unsuccessful toxins (due to off-target effects) may be revisited with mixtures by utilizing the pharmacodynamic response to the potential primary therapeutic as a starting point for finding new targets to ameliorate the unintended responses. In this proof of principle study, the pharmacodynamic response of HepG2 cells to a potential primary therapeutic (deguelin, a plant-derived chemopreventive agent) was monitored, and a possible secondary target (p38MAPK) was identified. As a single agent, deguelin decreased cellular viability at higher doses (>10 μM), but inhibited oxygen consumption over a wide dosing range (1.0-100 μM). Our results demonstrate that inhibition of oxygen consumption is related to an increase in p38MAPK phosphorylation, and may only be an undesired side effect of deguelin (i.e., one that does not contribute to the decrease in HepG2 viability). We further show that deguelin's negative effect on oxygen consumption can be diminished while maintaining efficacy when used as a therapeutic mixture with the judiciously selected secondary inhibitor (SB202190, p38MAPK inhibitor). These preliminary findings suggest that an endogenous response-directed mixtures approach, which uses a pharmacodynamic response to a primary therapeutic to determine a secondary target, allows previously unsuccessful toxins to be revisited as therapeutic mixtures.

A novel antitumor activity of deguelin targeting the insulin-like growth factor (IGF) receptor pathway via up-regulation of IGF-binding protein-3 expression in breast cancer

In this study, we investigated the antitumor effects of deguelin in several human breast cancer cells in vitro and in vivo. Deguelin inhibited cell viability and the anchorage-dependent and anchorage-independent colony formation of triple-negative (MDA-MB-231 and MDA-MB-468) and triple-positive (MCF-7) breast cancer cells, and it significantly reduced the growth of MCF-7 cell xenograft tumors. The induction of apoptosis, inhibition of insulin-like growth factor-1 receptor (IGF-1R) signaling activation, and up-regulation of IGF-binding protein-3 (IGFBP-3) expression may be associated with deguelin-mediated antitumor effects. Our findings suggest a potential therapeutic use for deguelin in patients with triple-negative breast cancer and for those with breast cancers who are sensitive to endocrine- and HER2-targeted therapies.

Deguelin, a novel anti-tumorigenic agent targeting apoptosis, cell cycle arrest and anti-angiogenesis for cancer chemoprevention

Deguelin is a natural compound of the flavonoid family products isolated from Derris trifoliata Lour. or Mundulea sericea (Leguminosae). It exhibited significant anti-tumorigenesis and anti-proliferative activity in various types of cancer both in vitro and in vivo. Deguelin induced cell apoptosis by blocking anti-apoptotic pathways, such as PI3K-Akt, IKK-IκBα-NF-κB and AMPK-mTOR-survivin, while inhibiting tumor cell propagation and malignant transformation through p27-cyclinE-pRb-E2F1 cell cycle control and HIF-1α-VEGF anti-angiogenic pathways. In pre-clinical trials, deguelin markedly decreased the tumor incidence. These biological findings identified deguelin as a novel anti-tumorigenic agent targeting apoptosis, cell cycle arrest and anti-angiogenesis for cancer chemoprevention and chemotherapy.

Multi-level targeting of the phosphatidylinositol-3-kinase pathway in non-small cell lung cancer cells

Introduction

We assessed expression of p85 and p110α PI3K subunits in non-small cell lung cancer (NSCLC) specimens and the association with mTOR expression, and studied effects of targeting the PI3K/AKT/mTOR pathway in NSCLC cell lines.

Methods

Using Automated Quantitative Analysis we quantified expression of PI3K subunits in two cohorts of 190 and 168 NSCLC specimens and correlated it with mTOR expression. We studied effects of two PI3K inhibitors, LY294002 and NVP-BKM120, alone and in combination with rapamycin in 6 NSCLC cell lines. We assessed activity of a dual PI3K/mTOR inhibitor, NVP-BEZ235 alone and with an EGFR inhibitor.

Results

p85 and p110α tend to be co-expressed (p<0.001); p85 expression was higher in adenocarcinomas than squamous cell carcinomas. High p85 expression was associated with advanced stage and poor survival. p110α expression correlated with mTOR (ρ = 0.276). In six NSCLC cell lines, addition of rapamycin to LY294002 or NVP-BKM120 was synergistic. Even very low rapamycin concentrations (1 nM) resulted in sensitization to PI3K inhibitors. NVP-BEZ235 was highly active in NSCLC cell lines with IC₅₀s in the nanomolar range and resultant down-regulation of pAKT and pP70S6K. Adding Erlotinib to NVP-BEZ235 resulted in synergistic growth inhibition.

Conclusions

The association between PI3K expression, advanced stage and survival in NSCLC suggests that it might be a valuable drug target. Concurrent inhibition of PI3K and mTOR is synergistic in vitro, and a dual PI3K/mTOR inhibitor was highly active. Adding EGFR inhibition resulted in further growth inhibition. Targeting the PI3K/AKT/mTOR pathway at multiple levels should be tested in clinical trials for NSCLC.

Induction of DNA damage by deguelin is mediated through reducing DNA repair genes in human non-small cell lung cancer NCI-H460 cells

It has been shown that deguelin, one of the compounds of rotenoids from flavonoid family, induced cytotoxic effects through induction of cell cycle arrest and apoptosis in many types of human cancer cell lines, but deguelin-affected DNA damage and repair gene expression (mRNA) are not clarified yet. We investigated the effects of deguelin on DNA damage and associated gene expression in human lung cancer NCI-H460 cells in vitro. DNA damage was assayed by using the comet assay and DNA gel electrophoresis and the results indicated that NCI-H460 cells treated with 0, 50, 250 and 500 nM deguelin led to a longer DNA migration smear based on the single cell electrophoresis and DNA fragmentation occurred based on the examination of DNA gel electrophoresis. DNA damage and repair gene expression (mRNA) were evaluated by using real-time PCR assay and the results indicated that 50 and 250 nM deguelin for a 24-h exposure in NCI-H460 cells, decreased the gene levels of breast cancer 1, early onset (BRCA1), DNA-dependent serine/threonine protein kinase (DNA-PK), O⁶-methylguanine-DNA methyltransferase (MGMT), p53, ataxia telangiectasia mutated (ATM) and ataxia-telangiectasia and Rad3-related (ATR) mRNA expressions. Collectively, the present study showed that deguelin caused DNA damage and inhibited DNA damage and repair gene expressions, which might be due to deguelin-inhibited cell growth in vitro.

Deguelin--an inhibitor to tumor lymphangiogenesis and lymphatic metastasis by downregulation of vascular endothelial cell growth factor-D in lung tumor model

Deguelin, a rotenoid of the flavonoid family, has been reported to possess antiproliferative and anticarcinogenic activities in several cell lines and tumor models. However, it is still unclear whether deguelin effectively inhibits tumor-associated lymphangiogenesis and lymphatic metastasis. Since tumor production of vascular endothelial cell growth factor (VEGF)-D was associated with tumor lymphangiogenesis and lymphatic metastasis, we established the mouse lymphatic metastasis model by transfecting high expression VEGF-D into LL/2 Lewis lung cells (VEGF-D-LL/2) and explored the effects of deguelin on lymphatic metastasis in the immunocompetent C57BL/6 mice. Our results indicated that deguelin inhibited proliferation, migration of VEGF-D-LL/2 cells via downregulating AKT and mitogen-activated protein kinase pathway and interfered tube formation of lymphatic vascular endothelial cells on matrigel at nanomolar concentrations. Deguelin significantly downregulated the expression of VEGF-D both at mRNA and protein levels in VEGF-D-LL/2 cells in a dose-dependent manner. In the in vivo study, intraperitoneal administration of deguelin (4 mg/kg) remarkably inhibited the tumor-associated lymphangiogenesis and lymphatic metastasis. The rates of lymph node and lung metastasis in deguelin-treated mice were 0 and 16.7% compared with 58.3 and 83.3% in control group mice, respectively. Deguelin also resulted in a remarkable delay of tumor growth and prolongation of life span. Immunohistochemical staining with antibodies against VEGF-D, LYVE-1 and VEGFR-3 revealed fewer positive vessel-like structures in deguelin-treated mice compared with control group mice. Taken together, we demonstrate for the first time that deguelin suppresses tumor-associated lymphangiogenesis and lymphatic metastasis by downregulation of VEGF-D both in vitro and in vivo.

Simultaneous quantitative monitoring of drug-induced caspase cascade pathways in carcinoma cells

Caspases are the key mediators of apoptosis. The caspase cascade includes a series of events leading to the activation of initiator and downstream caspases in a cell. Analysis of the caspase cascade in intact cells, however, has generally been limited as the simultaneous monitoring of upstream and downstream caspases is not well executed. In an effort to monitor the activation of caspase cascades in an intact cell, high-content cellular imaging that allows simultaneous quantitative monitoring of caspase activation has been developed. This has great significance for the exploration of various cellular caspases involved in apoptotic pathways as possible therapeutic targets in the process of drug discovery. To explore the potential of simultaneous monitoring of caspase-mediated apoptotic pathways, human myeloid leukemia HL-60 cells were treated with SH-03 {(7S,7aR,13aS)-9,10-dimethoxy-3,3-dimethyl-7,7a,13,13a-tetrahydro-3H-chromeno [3,4-b]pyrano[2,3-h]chromen-7-ol} (a newly synthesized candidate), camptothecin or naringenin (agents known to induce apoptosis) with or without caspase inhibitors. SH-03 or naringenin treatment initiated the caspase cascade through an intrinsic apoptotic pathway, whereas camptothecin treatment triggered both intrinsic and extrinsic caspase cascades. We now report a new approach based on uniform threshold intensity distribution that facilitates rapid, quantitative monitoring of drug-induced caspase cascades through multi-spectral and multicolor imaging cytometry.

Deguelin inhibits growth of breast cancer cells by modulating the expression of key members of the Wnt signaling pathway

An emphasis in early detection and more effective treatments has decreased the mortality rate of breast cancer. Despite this decrease, breast cancer continues to be the leading cause of death among women between 40 and 55 years of age and is the second overall cause of death among women. Hence, the aim of the present study was to assess the therapeutic efficacy of deguelin, a rotenoid isolated from several plant species, which has been reported to have chemopreventive and/or chemotherapeutic effects in skin, mammary, colon, and lung cancers. The effect of deguelin on cell proliferation was evaluated using four human breast carcinoma cell lines (MCF-7, BT474, T47D, and MDA-MB-231) by cell count and MTT. Moreover, apoptosis was evaluated by acridine/ethidium staining and DNA laddering. Gene expression changes following deguelin treatment in MDA-MB-231 cells was assessed through microarray analysis. Deguelin at 1 mumol/L was found to inhibit the growth of the breast cancer cell lines tested with a range of 37% to 87%. The highest inhibition was noted for the MDA-MB-231 cell line (MDA-MB-231>BT474>MCF7>T47D>MCF12F). An arrest at the S phase of the cell cycle and apoptosis were shown in the MDA-MB-231 cells treated with deguelin. The microarray profile indicated differential expression of two independent pathways, including clusters of apoptosis and Wnt/beta-catenin signaling genes in cells as a result of deguelin treatment. These studies support the antiproliferative effects of deguelin in human breast cancer cells and, perhaps more importantly, illustrate novel actions by deguelin in the Wnt signaling pathway.

A novel look into estrogen receptor-negative breast cancer prevention with the natural, multifunctional signal transduction inhibitor deguelin

This perspective on Murillo et al. (beginning on page 942 in this issue of the journal) examines the potential of the naturally derived agent deguelin to prevent mammary tumorigenesis. These investigators showed that deguelin inhibits wnt/beta-catenin signaling in breast cancer cell lines, in addition to inhibiting other previously reported signaling pathways. Our growing understanding of deguelin mechanisms could lead to important advances in the prevention of estrogen receptor-negative breast and other cancers.

Synergistic effect of ERK inhibition on tetrandrine-induced apoptosis in A549 human lung carcinoma cells

Tetrandrine (TET), a bis-benzylisoquinoline alkaloid from the root of Stephania tetrandra, is known to have anti-tumor activity in various malignant neoplasms. However, the precise mechanism by which TET inhibits tumor cell growth remains to be elucidated. The present studies were performed to characterize the potential effects of TET on phosphoinositide 3-kinase/Akt and extracellular signal-regulated kinase (ERK) pathways since these signaling pathways are known to be responsible for cell growth and survival. TET suppressed cell proliferation and induced apoptosis in A549 human lung carcinoma cells. TET treatment resulted in a down-regulation of Akt and ERK phosphorylation in both time-/concentration-dependent manners. The inhibition of ERK using PD98059 synergistically enhanced the TET-induced apoptosis of A549 cells whereas the inhibition of Akt using LY294002 had a less significant effect. Taken together, our results suggest that TET: i) selectively inhibits the proliferation of lung cancer cells by blocking Akt activation and ii) increases apoptosis by inhibiting ERK. The treatment of lung cancers with TET may enhance the efficacy of chemotherapy and radiotherapy and increase the apoptotic potential of lung cancer cells.

Deguelin inhibits retinal neovascularization by down-regulation of HIF-1alpha in oxygen-induced retinopathy

Retinal neovascularization is the most common cause of blindness; Retinopathy of pre-maturity (ROP) for children and diabetic retinopathy for young age group. ROP still remains as the most serious cause of vision loss in children. We provided that deguelin significantly reduces retinal neovascularization in a mouse model of ROP. Deguelin never affected the transcriptional activity of hypoxia inducible factor (HIF)-1, however, reduced HIF-1 expression, which led to the decrease of vascular endothelial growth factor expression. Deguelin effectively suppressed endothelial cell proliferation without cytotoxic effect under therapeutic concentration range. In addition, deguelin demonstrated no reduction or retardation in normal retinal development and no retinal toxicity. These data suggest deguelin is a potent inhibitor of retinal neovascularization and may be applied in the treatment of other vasoproliferative retinopathies.

A novel derivative of the natural agent deguelin for cancer chemoprevention and therapy

The natural compound deguelin has promising preventive and therapeutic activity against diverse cancers by directly binding to heat shock protein-90 and thus suppressing its function. Potential side effects of deguelin over a certain dose, however, could be a substantial obstacle to its clinical use. To develop a derivative(s) of deguelin with reduced potential side effects, we synthesized five deguelin analogues (SH-02, SH-03, SH-09, SH-14, and SH-15) and compared them with the parent compound and each other for structural and biochemical features; solubility; and antiproliferative effects on normal, premalignant, and malignant human bronchial epithelial (HBE) and non-small-cell lung cancer (NSCLC) cell lines. Four derivatives destabilized hypoxia-inducible factor-1alpha as potently as did deguelin. Reverse-phase protein array (RPPA) analysis in H460 NSCLC cells revealed that deguelin and the derivatives suppressed expression of a number of proteins including heat shock protein-90 clients and proteins involved in the phosphoinositide 3-kinase/Akt pathway. One derivative, SH-14, showed several features of potential superiority for clinical use: the highest apoptotic activity; no detectable influence on Src/signal transducer and activator of transcription signaling, which can promote cancer progression and is closely related to pathogenesis of Parkinson's disease (deguelin, SH-02 and SH-03 strongly activated this signaling); better aqueous solubility; and less cytotoxicity to immortalized HBE cells (versus deguelin) at a dose (1 micromol/L) that induced apoptotic activity in most premalignant and malignant HBE and NSCLC cell lines. These collective results suggest that the novel derivative SH-14 has strong potential for cancer chemoprevention and therapy, with equivalent efficacy and lesser toxicity (versus deguelin).

Identification of novel antiangiogenic anticancer activities of deguelin targeting hypoxia-inducible factor-1 alpha

Hypoxia-inducible factor 1 (HIF-1) plays an essential role in tumor angiogenesis and growth by regulating the transcription of several genes in response to hypoxic stress and changes in growth factors. This study was designed to investigate the effects of deguelin on tumor growth and angiogenesis, and the mechanisms underlying the antitumor activities of deguelin. We show here that orally administered deguelin inhibits tumor growth and blocks tumor angiogenesis in mice. Deguelin decreased expression of HIF-1alpha protein and its target genes, such as VEGF, in a subset of cancer cell lines, including H1299 lung cancer cells, and vascular endothelial cells in normoxic and hypoxic conditions. Overexpression of vascular endothelial growth factor by adenoviral vector infection abolished the antiangiogenic effects of deguelin on H1299 nonsmall cell lung cancer cells. Deguelin inhibited de novo synthesis of HIF-1alpha protein and reduced the half-life of the synthesized protein. MG132, a proteasome inhibitor, protected the hypoxia- or IGF-induced HIF-1alpha protein from deguelin-mediated degradation. Our findings suggest that deguelin is a promising antiangiogenic therapeutic agent in cancer targeting HIF-1alpha. Considering that HIF-1alpha is overexpressed in a majority of human cancers, deguelin could offer a potent therapeutic agent for cancer.

Inhibition of smooth muscle cell proliferation by a chemically modified tetracycline

INTRODUCTION

Chemically modified tetracyclines (CMTs) are a group of nonantimicrobial derivatives of tetracycline, which exert antiproliferative and anticollagenolytic properties. The molecular mechanisms, however, are poorly understood.

MATERIALS AND METHODS

The effect of CMT-3 on cultured, subconfluent rat aortic smooth muscle cells (SMCs) was analyzed by [(3)H]-thymidine incorporation, counting cell numbers, and flow cytometry analysis.

RESULTS

CMT-3 inhibited the incorporation of [(3)H]-thymidine and reduced the cell number dose-dependently, with approximately 60% inhibition at the maximal CMT-3 concentration used (20 mumol/l). CMT-3 decreased the SMC proportion in S-phase and gradually increased the proportion at G2/M. Initially, the proportion of cells in G1-phase increased and then gradually decreased back to baseline as the CMT-3 concentration increased. CMT-3 treatment of confluent SMCs for 24 h did not induce apoptosis.

CONCLUSIONS

CMT-3 inhibited SMC proliferation by inducing cell cycle arrest at the G2/M restriction point. Nonetheless, CMT-3 did not induce SMC apoptosis.

Antiangiogenic effect of deguelin on choroidal neovascularization

Age-related macular degeneration is the leading cause of blindness in the elderly. Choroidal neovascularization (CNV) leads to severe vision loss in patients of age-related macular degeneration. Previously, we have demonstrated that deguelin, isolated from plants in the Mundulea sericea family, is a chemopreventive agent. This study evaluates the antiangiogenic effect of deguelin on CNV. The toxicity of deguelin was evaluated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay in human umbilical vein endothelial cells (HUVECs) as well as histological examination and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining in the deguelin-injected retina. Antiangiogenic activity of deguelin was evaluated by in vitro tube formation assay of HUVECs and in vivo angiogenesis of chick chorioallantoic membrane (CAM). In C57BL/6 mice with laser-induced CNV, deguelin or phosphate-buffered saline was injected intravitreously. CNV lesions were examined by fluorescence angiography and vessel counting in cross-sections. Deguelin showed no effect on cell viability of HUVECs and no retinal toxicity in a concentration range of 0.01 to 1 microM. Deguelin effectively inhibited in vitro tube formation of HUVECs and in vivo angiogenesis of CAM. Interestingly, deguelin significantly reduced CNV and its leakage in mouse model of laser photocoagulation-induced CNV. Our data suggests that deguelin is a potent inhibitor of CNV and may be applied in the treatment of other vasoproliferative retinopathies such as retinopathy of prematurity and diabetic retinopathy.

Targeting the AKT protein kinase for cancer chemoprevention

The AKT protein kinase transduces signals from growth factors and oncogenes to downstream targets that control crucial elements in tumor development. The AKT pathway is one of the most frequently hyperactivated signaling pathways in human cancers. Available data are reviewed herein to support targeting the AKT kinase for cancer prevention. This review will present data to show that AKT is up-regulated in preneoplastic lesions across a broad range of target tissues, briefly describe drug development efforts in this area, and present evidence that down-regulation of AKT signaling may be a viable strategy to prevent cancer.

Deguelin inhibits expression of IκBα protein and induces apoptosis of B-CLL cells in vitro

We investigated if deguelin, a naturally occurring rotenoid, was able to inhibit nuclear factor kappa B (NF-kappaB)-binding protein (IkappaBalpha) expression and to induce apoptosis in B-cell chronic lymphocytic leukemia (B-CLL) cells in vitro. Deguelin-induced cell death in the majority of B-CLL cells and was found to be more toxic toward B-CLL cells than to the normal mononuclear or B-cells, suggesting selectivity towards the malignant cells. Deguelin was found to reduce IkappaBalpha protein expression, and thus interacts with the NFkappaB pathway. The induced apoptosis was characterized by processing of caspase-9 and -3 and poly-(ADP)-ribose-polymerase cleavage. Exposure of B-CLL cells to deguelin resulted in Bcl2-associated protein (Bax) conformational changes and downregulation of the key survival protein myeloid cell leukemia sequence 1 (Mcl-1), which is associated with response to treatment in B-CLL patients. Deguelin retained its ability to induce apoptosis in B-CLL cells in the presence of interleukin-4, a pro-survival cytokine in B-CLL, and when cultured with 50% human serum. These data indicate that deguelin is able to induce apoptosis in B-CLL cells in the presence of pro-survival signals and thus merits further investigation for clinical application either as a single agent or in combination with other anticancer agents.

Structural basis for depletion of heat shock protein 90 client proteins by deguelin

BACKGROUND

The molecular chaperone heat shock protein 90 (Hsp90) participates in preserving the expression and activity of various oncoproteins, including hypoxia-inducible factor 1alpha (HIF-1alpha) and Akt. Deguelin is a rotenoid with antitumor activities. We investigated whether the antitumor activities of deguelin involve the functional inhibition of Hsp90.

METHOD

Human xenograft tumors were generated in mice from H1299 (n = 6 per group) and A549 (n = 4 per group) non-small-cell lung cancer cells, UMSCC38 (n = 5 per group) head and neck cancer cells, MKN45 (n = 5 per group) stomach cancer cells, and PC-3 (n = 3 per group) prostate cancer cells. Tumor-bearing mice were treated with deguelin at 4 or 8 mg/kg or with vehicle (as a control) twice a day by oral gavage for 15-28 days. Protein expression was assessed by western blot analysis. Akt and Hsp90 were assessed by use of adenoviral vectors expressing constitutively active Akt or Hsp90. Binding of deguelin to Hsp90 was examined by docking analysis and by competition binding experiments with ATP-Sepharose beads. The proteasome inhibitor MG132 was used to investigate deguelin's effect on the induction of ubiquitin-mediated proteasomal degradation of HIF-1alpha. All statistical tests were two-sided.

RESULTS

Deguelin bound to the ATP-binding pocket of Hsp90 and disrupted Hsp90 function, leading to ubiquitin-mediated degradation of HIF-1alpha. Administration of deguelin to xenograft-bearing mice statistically significantly decreased tumor growth by inducing apoptosis and decreasing the expression of Hsp90 client proteins, without detectable toxic effects. For example, at 15 days after the start of deguelin treatment, the volume of untreated control H1299 xenograft tumors was 798 mm3 and that of xenograft tumors treated with deguelin at 4 mg/kg was 115.9 mm3 (difference = 682.1 mm3, 95% confidence interval = 480.4 to 883.9 mm3; P<.001).

CONCLUSIONS

The antitumor activities of deguelin appear to involve its binding to the ATP-binding pocket of Hsp90, which suppresses Hsp90 function.

Down-regulation of inhibitor of apoptosis proteins by deguelin selectively induces apoptosis in breast cancer cells

The identification of differentially regulated apoptotic signals in normal and tumor cells allows the development of cancer cell-selective therapies. Increasing evidence shows that the inhibitor of apoptosis (IAP) proteins survivin and XIAP are highly expressed in tumor cells but are absent or have very low levels of expression in normal adult tissues. We found that inhibiting AKT activity with 10 to 100 nM deguelin, a small molecule derived from natural products, markedly reduced the levels of both survivin and XIAP, inducing apoptosis in human breast cancer cells but not in normal cells. It is noteworthy that we detected an elevated level of cleaved poly(ADP-ribose) polymerase, a signature of caspase activation, without a significant increase in caspase activity in deguelin-treated cancer cells. Our results suggest that severe down-regulation of the IAPs by deguelin releases their inhibitory activity over pre-existing active caspases present in cancer cells, inducing apoptosis without the need for further caspase activation. Because normal cells have very low levels of p-AKT, XIAP, survivin, and pre-existing caspase activity, deguelin had little effect on those cells. In addition, we found that combining deguelin with chemotherapy drugs enhanced drug-induced apoptosis selectively in human tumor cells, which suggests that deguelin has great potential for chemosensitization and could represent a new therapeutic agent for treatment of breast cancer.

Efficacy of deguelin and silibinin on benzo(a)pyrene-induced lung tumorigenesis in A/J mice

We evaluated deguelin and silibinin in A/J mice treated with the tobacco-specific carcinogen benzo(a)pyrene (BP) for their ability to inhibit pulmonary adenoma formation and growth. Animals were treated with either deguelin (5.0 or 10.0 mg/kg body weight, by gavage) or silibinin at doses of 0.05% and 0.1% in the diet, approximately 10 days before a single intraperitoneal dose of BP. We found that oral administration of deguelin reduced tumor multiplicity by 56% and tumor load by 78%, whereas silibinin treatment at doses of 0.05% and 0.1% in the diet did not show any significant efficacy on either tumor multiplicity or tumor load. The result indicates that deguelin significantly inhibits pulmonary adenoma formation and growth in A/J mice. Finding new and effective agents that can prevent lung cancer is urgently needed because cancer of the lungs remains the principal cause of cancer deaths in the United States and because effective chemoprevention of this cancer type remains elusive. Thus, deguelin appears to be a promising new preventive agent for lung cancer and may be considered for further studies in other animal models and in clinical trials.

Chemopreventive Effects of Deguelin, a Novel Akt Inhibitor, on Tobacco-Induced Lung Tumorigenesis

Tobacco carcinogens induce Akt activation and lung carcinogenesis. We previously demonstrated that deguelin, a natural plant product, specifically inhibits the proliferation of premalignant and malignant human bronchial epithelial cells by blocking Akt activation. To evaluate the ability of deguelin to block tobacco carcinogen-induced lung tumorigenesis, we evaluated the in vivo effects of deguelin on Akt activation and lung tumorigenesis in transgenic mice in which Akt expression was induced by tamoxifen and in 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK)/benzo(a)pyrene (BaP)-treated A/J mice. Deguelin suppressed Akt activation in vivo, as measured by immunohistochemistry and immunoblotting, and statistically significantly reduced NNK/BaP-induced lung tumor multiplicity, volume, and load in A/J mice, as monitored by microcomputed tomography image analysis, with no detectable toxicity. These results indicate that deguelin warrants consideration as a chemopreventive agent for early-stage lung carcinogenesis in a clinical lung cancer chemoprevention trial.

Phospho-akt expression is associated with a favorable outcome in non-small cell lung cancer

Akt, a Serine/Threonine protein kinase, mediates growth factor-associated cell survival. Constitutive activation of Akt (phosphorylated Akt, P-Akt) has been observed in several human cancers, including lung cancer and may be associated with poor prognosis and chemotherapy and radiotherapy resistance. The clinical relevance of P-Akt in non-small cell lung cancer (NSCLC) is not well described. In the present study, we examined 82 surgically resected snap-frozen and paraffin-embedded stage I to IIIA NSCLC samples for P-Akt and Akt by Western blotting and for P-Akt by immunohistochemistry. P-Akt protein levels above the median, measured using reproducible semiquantitative band densitometry, correlated with a favorable outcome (P = 0.007). Multivariate analysis identified P-Akt as a significant independent favorable prognostic factor (P = 0.004). Although associated with a favorable prognosis, high P-Akt levels correlated with high tumor grade (P = 0.02). Adenocarcinomas were associated with low P-Akt levels (P = 0.039). Akt was not associated with either outcome or clinicopathologic variables. Cytoplasmic (CP-Akt) and nuclear (NP-Akt) P-Akt tumor cell staining was detected in 96% and 42% of cases, respectively. Both CP-Akt and NP-Akt correlated with well-differentiated tumors (P = 0.008 and 0.017, respectively). NP-Akt also correlated with nodal metastases (P = 0.022) and squamous histology (P = 0.037).These results suggest P-Akt expression is a favorable prognostic factor in NSCLC. Immunolocalization of P-Akt, however, may be relevant as NP-Akt was associated with nodal metastases, a known poor prognostic feature in this disease. P-Akt may be a potential novel therapeutic target for the management of NSCLC.