RESUMEN
Hypoxia is a common feature of solid tumors, and the extent of tumor hypoxia correlates with advanced disease stages and treatment resistance. The transcription factor hypoxia-inducible factor-1 (HIF-1) represents an important tumor-selective molecular target for anticancer drug discovery directed at tumor hypoxia. A natural product chemistry-based approach was employed to discover small molecule inhibitors of HIF-1. Bioassay-guided isolation of an active lipid extract of the tropical legumaceous plant Lonchocarpus glabrescens and structure elucidation afforded two new HIF-1 inhibitors: alpinumisoflavone (compound 1) and 4'-O-methylalpinumisoflavone (compound 2). In human breast tumor T47D cells, compounds 1 and 2 inhibited hypoxia-induced HIF-1 activation with IC(50) values of 5 and 0.6 mum, respectively. At the concentrations that in hibited HIF-1 activation, compound 2 inhibited hypoxic induction of HIF-1 target genes (CDKN1A, GLUT-1, and VEGF), tumor angiogenesis in vitro, cell migration, and chemotaxis. Compound 2 inhibits HIF-1 activation by blocking the induction of nuclear HIF-1alpha protein, the oxygen-regulated subunit that controls HIF-1 activity. Mechanistic studies indicate that, unlike rotenone and other mitochondrial inhibitors, compound 2 represents the first small molecule that inhibits HIF-1 activation by simultaneously suppressing mitochondrial respiration and disrupting protein translation in vitro. This unique mechanism distinguishes compound 2 from other small molecule HIF-1 inhibitors that are simple mitochondrial inhibitors or flavanoid-based protein kinase inhibitors.
Asunto(s)
Movimiento Celular/efectos de los fármacos , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Transportador de Glucosa de Tipo 1/metabolismo , Subunidad alfa del Factor 1 Inducible por Hipoxia/antagonistas & inhibidores , Isoflavonas/farmacología , Factor A de Crecimiento Endotelial Vascular/metabolismo , Western Blotting , Neoplasias de la Mama/irrigación sanguínea , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/metabolismo , Hipoxia de la Célula , Proliferación Celular , Respiración de la Célula/efectos de los fármacos , Respiración de la Célula/fisiología , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Quimiotaxis , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/genética , Endotelio Vascular/citología , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/metabolismo , Ensayo de Inmunoadsorción Enzimática , Fabaceae/química , Transportador de Glucosa de Tipo 1/genética , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Masculino , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Neovascularización Patológica , Consumo de Oxígeno/efectos de los fármacos , Neoplasias de la Próstata/irrigación sanguínea , Neoplasias de la Próstata/tratamiento farmacológico , Neoplasias de la Próstata/metabolismo , Biosíntesis de Proteínas , Venas Umbilicales/citología , Venas Umbilicales/efectos de los fármacos , Venas Umbilicales/metabolismo , Factor A de Crecimiento Endotelial Vascular/genética , Cicatrización de HeridasRESUMEN
Rapidly increasing experimental and clinical data provides evidence for the role of hypoxia inducible factor-1 (HIF-1) as a crucial mediator of tumor survival and progression. In our effort to identify inhibitors of the HIF-1 activation pathway, we screened fractions from marine invertebrates. Fractions from an extract of Petrosia (Strongylophora) strongylata potently inhibited the HIF-1 activation pathway. Strongylophorines 2, 3, and 8 isolated from the active fractions were found to be responsible for the HIF-1 inhibition with EC 50 values of 8, 13, and 6 microM, respectively.
Asunto(s)
Antineoplásicos/síntesis química , Diterpenos/farmacología , Factor 1 Inducible por Hipoxia/antagonistas & inhibidores , Petrosia/química , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Hipoxia de la Célula , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Diterpenos/química , Diterpenos/aislamiento & purificación , Ensayos de Selección de Medicamentos Antitumorales , Genes Reporteros , Humanos , Factor 1 Inducible por Hipoxia/genética , Subunidad alfa del Factor 1 Inducible por Hipoxia/biosíntesis , Luciferasas/genética , Relación Estructura-Actividad , Transcripción Genética , Factor A de Crecimiento Endotelial Vascular/biosíntesisRESUMEN
This report describes the synthesis and biological activity of imidazoquinoxalines, benzimidazole-based analogues of indole-based pyrroloiminoquinone marine natural products. Our analogues consist of series 1, which possesses the ethylene tether and extended amidine feature found in the pyrroloiminoquinone natural products, and series 2, which also has the ethylene tether but with an electrostatically stabilized iminoquinone rather than a resonance stabilized iminoquinone (i.e., extended amidine). The biological properties of series 1 analogues, bearing electron-rich side chain rings (indole and phenol), display cytostatic and cytotoxic properties similar to that of the pyrroloiminoquinone natural products. In contrast, COMPARE analysis suggests that analogues bearing benzyl and phenethyl side chains possess a different cytotoxicity mechanism. Hollow fiber assays of analogs of 1 indicate promising antitumor activity and acceptable levels of toxicity. One analogue of 2 is active only against breast cancer cell lines, but the cellular target is as yet unknown.
Asunto(s)
Antineoplásicos/síntesis química , Productos Biológicos/química , Imidazoles/síntesis química , Pirroles/química , Quinolonas/química , Quinoxalinas/síntesis química , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Línea Celular Tumoral , ADN-Topoisomerasas de Tipo II/química , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Imidazoles/química , Imidazoles/farmacología , Biología Marina , Ratones , Quinoxalinas/química , Quinoxalinas/farmacología , Relación Estructura-Actividad , Pruebas de Toxicidad AgudaRESUMEN
Theopapuamide (1), a new cytotoxic peptide, has been isolated from the lithistid sponge Theonella swinhoei from Papua New Guinea. The structure was established by analysis of NMR, mass spectrometry, and chemical methods. The undecapeptide (1) contains several unusual amino acid residues, of which the occurrence of beta-methoxyasparagine and 4-amino-5-methyl-2,3,5-trihydroxyhexanoic acid (Amtha) is unprecedented in natural peptides. Compound 1 also contains an amide-linked fatty acid moiety, 3-hydroxy-2,4,6-trimethyloctanoic acid (Htoa). Theopapuamide (1) was cytotoxic against CEM-TART and HCT-116 cell lines, with EC50 values of 0.5 and 0.9 microM, respectively.
Asunto(s)
Antineoplásicos/aislamiento & purificación , Depsipéptidos/aislamiento & purificación , Theonella/química , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Depsipéptidos/química , Depsipéptidos/farmacología , Ensayos de Selección de Medicamentos Antitumorales , Estructura Molecular , Resonancia Magnética Nuclear Biomolecular , Papúa Nueva GuineaRESUMEN
Hypoxia-inducible factor-1 (HIF-1) represents an important tumor-selective therapeutic target for solid tumors. In search of novel small molecule HIF-1 inhibitors, 5400 natural product-rich extracts from plants, marine organisms, and microbes were examined for HIF-1 inhibitory activities using a cell-based reporter assay. Bioassay-guided fractionation and isolation, followed by structure elucidation, yielded three potent natural product-derived HIF-1 inhibitors and two structurally related inactive compounds. In a T47D cell-based reporter assay, manassantin B1, manassantin A, and 4-O-methylsaucerneol inhibited hypoxia-induced HIF-1 activation with IC50 values of 3, 3, and 20 nM, respectively. All three compounds are relatively hypoxia-specific inhibitors of HIF-1 activation, in comparison to other stimuli. The hypoxic induction of HIF-1 target genes CDKN1A, VEGF, and GLUT-1 were also inhibited. These compounds inhibit HIF-1 by blocking hypoxia-induced nuclear HIF-1alpha protein accumulation without affecting HIF-1alpha mRNA levels. In addition, preliminary structure-activity studies suggest specific structural requirements for this class of HIF-1 inhibitors.
Asunto(s)
Proteínas de Unión al ADN/antagonistas & inhibidores , Lignanos/farmacología , Proteínas Nucleares/antagonistas & inhibidores , Saururaceae/química , Factores de Transcripción/antagonistas & inhibidores , Línea Celular Tumoral , Ensayo de Inmunoadsorción Enzimática , Humanos , Factor 1 Inducible por Hipoxia , Subunidad alfa del Factor 1 Inducible por Hipoxia , Lignanos/química , Lignanos/aislamiento & purificación , Resonancia Magnética Nuclear Biomolecular , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
The degree of tumor hypoxia correlates with advanced disease stages and treatment resistance. The transcription factor hypoxia-inducible factor-1 (HIF-1) promotes tumor cell adaptation and survival under hypoxic conditions. Therefore, specific HIF-1 inhibitors represent an important new class of potential tumor-selective therapeutic agents. A T47D human breast tumor cell-based reporter assay was used to examine extracts of plants and marine organisms for inhibitors of HIF-1 activation. Bioassay-guided fractionation of the lipid extract of the red alga Laurencia intricata yielded a structurally novel diterpene, laurenditerpenol (1). The structure of 1 was determined spectroscopically. The relative configurations of the substituents of each ring system were assigned on the basis of NOESY correlations. The absolute configuration of position C-1 was determined by the modified Mosher ester procedure (directly in NMR tubes). Compound 1 potently inhibited hypoxia-activated HIF-1 (IC50: 0.4 microM) and hypoxia-induced VEGF (a potent angiogenic factor) in T47D cells. Compound 1 selectively inhibits HIF-1 activation by hypoxia but not iron chelator-induced activation. Further, 1 suppresses tumor cell survival under hypoxic conditions without affecting normoxic cell growth. Compound 1 inhibits HIF-1 by blocking the induction of the oxygen-regulated HIF-1alpha protein. Mitochondrial respiration studies revealed that 1 suppresses oxygen consumption.
Asunto(s)
Antineoplásicos/aislamiento & purificación , Proteínas de Unión al ADN/antagonistas & inhibidores , Diterpenos/aislamiento & purificación , Hipoxia , Proteínas Nucleares/antagonistas & inhibidores , Rhodophyta/química , Factores de Transcripción/antagonistas & inhibidores , Antineoplásicos/química , Antineoplásicos/farmacología , Neoplasias de la Mama , Diterpenos/química , Diterpenos/farmacología , Relación Dosis-Respuesta a Droga , Humanos , Factor 1 Inducible por Hipoxia , Subunidad alfa del Factor 1 Inducible por Hipoxia , Mitocondrias/metabolismo , Estructura Molecular , Resonancia Magnética Nuclear Biomolecular , EstereoisomerismoRESUMEN
Antitumor drug discovery programs aim to identify chemical entities for use in the treatment of cancer. Many strategies have been used to achieve this objective. Natural products have always played a major role in anticancer medicine and the unique metabolites produced by marine organisms have increasingly become major players in antitumor drug discovery. Rapid advances have occurred in the understanding of tumor biology and molecular medicine. New insights into mechanisms responsible for neoplastic disease are significantly changing the general philosophical approach towards cancer treatment. Recently identified molecular targets have created exciting new means for disrupting tumor-specific cell signaling, cell division, energy metabolism, gene expression, drug resistance and blood supply. Such tumor-specific treatments could someday decrease our reliance on traditional cytotoxicity-based chemotherapy and provide new less toxic treatment options with significantly fewer side effects. Novel molecular targets and state-of-the-art, molecular mechanism-based screening methods have revitalized antitumor research and these changes are becoming an ever-increasing component of modern antitumor marine natural products research. This review describes marine natural products identified using tumor-specific mechanism-based assays for regulators of angiogenesis, apoptosis, cell cycle, macromolecule synthesis, mitochondrial respiration, mitosis, multidrug efflux and signal transduction. Special emphasis is placed on natural products directly discovered using molecular mechanism-based screening.
Asunto(s)
Antineoplásicos/química , Productos Biológicos/química , Agua de Mar , Inhibidores de la Angiogénesis/química , Inhibidores de la Angiogénesis/aislamiento & purificación , Inhibidores de la Angiogénesis/farmacología , Animales , Antineoplásicos/aislamiento & purificación , Antineoplásicos/farmacología , Productos Biológicos/aislamiento & purificación , Productos Biológicos/farmacología , Industria Farmacéutica , Resistencia a Múltiples Medicamentos , Humanos , Mitocondrias/efectos de los fármacos , Neoplasias/tratamiento farmacológico , Transducción de SeñalRESUMEN
The sponge sterol 9alpha,11alpha-epoxycholest-7-ene-3beta,5alpha,6alpha,19-tetrol 6-acetate (ECTA) (1) is the first marine natural product to reverse fluconazole resistance mediated by a Candida albicans MDR efflux pump. The IC(50) of fluconazole is decreased from 300 to 8.5 microM (35-fold enhancement) when combined with 1(3.8 microM). A revised C-6 configuration of 1 is established.