| 1. |
- Don-Doncow, Nicholas, et al.
(författare)
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Galiellalactone is a Direct Inhibitor of STAT3 in Prostate Cancer Cells.
- 2014
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 289:23, s. 15969-15978
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Tidskriftsartikel (refereegranskat)abstract
- The transcription factor STAT3 is constitutively active in several malignancies including castration-resistant prostate cancer and has been identified as a promising therapeutic target. The fungal metabolite galiellalactone, a STAT3 signaling inhibitor, inhibits the growth, both in vitro and in vivo, of prostate cancer cells expressing active STAT3 and induces apoptosis of prostate cancer stem cell-like cells expressing pSTAT3. However, the molecular mechanism of this STAT3 inhibiting effect by galiellalactone has not been clarified. A biotinylated analogue of galiellalactone (GL-biot) was synthesized to be used for identification of galiellalactone target proteins. By adding streptavidin-sepharose beads to GL-biot treated DU145 cell lysates, STAT3 was isolated and identified as a target protein. Confocal microscopy revealed GL-biot in both the cytoplasm and nucleus of DU145 cells treated with GL-biot, appearing to co-localize with STAT3 in the nucleus. Galiellalactone inhibited STAT3 binding to DNA in DU145 cell lysates without affecting phosphorylation status of STAT3. Mass spectrometry analysis of recombinant STAT3 protein pretreated with galiellalactone revealed three modified cysteines (cys-367, cys-468 and cys-542). We here demonstrate with chemical and molecular pharmacological methods that galiellalactone is a cysteine reactive inhibitor that covalently binds to one or more cysteines in STAT3 and that this leads to inhibition of STAT3 binding to DNA and thus blocks STAT3 signaling without affecting phosphorylation. This further validates galiellalactone as a promising direct STAT3 inhibitor for treatment of castration-resistant prostate cancer.
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| 2. |
- Escobar, Zilma
(författare)
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Galiellalactone Synthetic Studies
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In search for remedies and treatments, science has recurred to Mother Nature. This is where galiellalactone was found, a fungal metabolite isolated from Galiella rufa in 1990. Since then chemists and biologists have been studying its properties and found it to be a potential candidate against castration-resistance prostate cancer (CRPC). The development of a new drug requires many studies of the compound and analogs thereof. Our contribution has been to generate new synthetic routes and to synthesize new analogs of galiellalactone with different substitutions in position C-4 and C-7. Among these, two were used as tools to confirm that galiellalactone binds directly to the STAT3 protein and that this binding event prevents the transcription by STAT3. Knowing that STAT3 is the target for galiellalactone, a new computational model revealed C-7b as an interesting position for different substituents. To investigate this, more biological studies in vivo and in vitro were needed and hence more galiellalactone analogs. In order to meet the demands of larger quantities we solved this problem by finding optimal conditions for a fermentation process in large scale. With sufficient amounts of galiellalacton in our hands, we designed semi-synthetic routes starting with two main focuses; to develop prodrugs, and to prepare new analogs focusing on substitutions at positions C-4 and C-7b for QSAR studies. We prepared a number of amine and thiol adducts as potential prodrugs, among these one thiol adduct (GPA512) showed promising results in vivo and in vitro. In parallel, a synthetic route towards desoxygaliellalactam was developed, this product will in a near future be tested for hydroxylation by the fungus. The overall objective of this work has therefore been to contribute to the probing of the potential of galiellalactone as a candidate of a drug for patients suffering from CRPC.
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| 3. |
- Escobar, Zilma, et al.
(författare)
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N-Conjugate prodrugs of galiellalactone
- 2016
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Ingår i: Tetrahedron Letters. - : Elsevier BV. - 0040-4039. ; 57:36, s. 4090-4093
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Tidskriftsartikel (refereegranskat)abstract
- A series of amine adducts of the fungal metabolite galiellalactone (1) were prepared by reacting galiellalactone with different secondary amines via a Lewis acid catalyzed Michael addition. The adducts were assayed for in vitro effects toward prostate cancer cell lines and found to possess a similar ability to inhibit cell proliferation as galiellalactone itself. It was found that the Michael addition of amines to 1 is a reversible reaction, releasing 1 at different rates depending on the conditions, and that the adducts are potential prodrugs of galiellalactone. The chemical stability of the amine adducts is especially sensitive to pH, increasing at a lower pH.
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| 4. |
- Escobar, Zilma, et al.
(författare)
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New pregaliellalactonoids from Galiella rufa
- 2015
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Ingår i: Phytochemistry Letters. - : Elsevier BV. - 1874-3900. ; 12, s. 138-141
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Tidskriftsartikel (refereegranskat)abstract
- An extract of a culture of the fungus Galiella rufa yielded several new derivatives of pregaliellalactone (1) that were characterised by NMR and MS experiments. The tetraene 4 has been reported previously, but was in this investigation isolated in sufficient amounts for the determination of the configuration of the C-4/C-5 double bond which is Z, not E. The possibility that any of the new compounds are involved in the biosynthesis of 1 is discussed. (C) 2015 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.
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| 5. |
- Escobar, Zilma, et al.
(författare)
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Preclinical Characterization of 3β-(N-Acetyl l -cysteine methyl ester)-2aβ,3-dihydrogaliellalactone (GPA512), a Prodrug of a Direct STAT3 Inhibitor for the Treatment of Prostate Cancer
- 2016
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 59:10, s. 4551-4562
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Tidskriftsartikel (refereegranskat)abstract
- The transcription factor STAT3 is a potential target for the treatment of castration-resistant prostate cancer. Galiellalactone (1), a direct inhibitor of STAT3, prevents the transcription of STAT3 regulated genes. In this study we characterized 6 (GPA512, Johansson, M.; Sterner, O. Patent WO 2015/132396 A1, 2015), a prodrug of 1. In vitro studies showed that 6 is rapidly converted to 1 in plasma and is stable in a buffer solution. The pharmacokinetics of 6 following a single oral dose indicated that the prodrug was rapidly absorbed and converted to 1 with a tmax of 15 min. Oral administration of 6 in mice increased the plasma exposure of the active parent compound 20-fold compared to when 1 was dosed orally. 6 treated mice bearing DU145 xenograft tumors had significantly reduced tumor growth compared to untreated mice. The favorable druglike properties and safety profile of 6 warrant further studies of 6 for the treatment of castration-resistant prostate cancer.
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| 6. |
- Escobar, Zilma, et al.
(författare)
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Stereoretentive Nucleophilic Substitution at the Tetrasubstituted Carbon of Galiellalactone
- 2020
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:12, s. 7704-7710
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Tidskriftsartikel (refereegranskat)abstract
- The fungal metabolite galiellalactone (1) was, as its acetate 4, discovered to undergo a substitution reaction with cysteine derivatives. By studying the reaction mechanism and the intermediates formed, and in an effort to expand the chemical diversity of the galiellalactonoids, a mild and general method of preparing ether, thioether, and amine analogues of galiellalactone was developed. The reaction is a formal stereoretentive nucleophilic substitution at an oxygenated tertiary carbon. NMR analysis of the progressing reaction shows that it involves an initial allylic substitution to form a new Michael acceptor, followed by the addition of a second equivalent of the nucleophile to this and, finally, a retro Michael reaction. This restores the original galiellalactone system with a double bond between C-2a and C-3, but with a new substituent at C-7b. As galiellalactone is a promising STAT3 inhibitor, this novel transformation facilitates the semisynthesis of a wide variety of new analogues for structure-activity relationship studies.
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| 7. |
- Escobar, Zilma, et al.
(författare)
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Synthesis of poinsettifolin A
- 2014
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Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020. ; 70:47, s. 9052-9056
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Tidskriftsartikel (refereegranskat)abstract
- A synthesis of poinsettifolin A (1), a prenylated flavonol isolated from Dorstenia poinsettifolia, is described. Two routes starting from quercetin were explored, and 1 could be prepared if a prenyl group first was incorporated at C-6 of the protected quercetin followed by a condensation with citral at C-8. The key synthetic steps are a Mitsunobu reaction, an europium (III)-catalysed Claisen rearrangement coupled with cross-metathesis, and a benzopyran-forming geranylation. The two geranylated 3,5,3',4'-tetrahydroxyflavonols prepared, 1 and 3, were assayed for antileishmanial activity against Leishmania amazonensis and Leishmania braziliensis, and found to be active. Compound 3 showed cytotoxic activity against leukaemia and lung cancer cells while 1 lacked cytotoxicity. (C) 2014 Elsevier Ltd. All rights reserved.
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| 8. |
- Tuasha, Nigatu, et al.
(författare)
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Cytotoxic and other bioactivities of a novel and known sesquiterpene lactones isolated from Vernonia leopoldi (Sch. Bip. ex Walp.) Vatke in breast cancer cell lines
- 2022
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Ingår i: Toxicology Reports. - : Elsevier BV. - 2214-7500. ; 9, s. 382-392
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Tidskriftsartikel (refereegranskat)abstract
- Vernonia leopoldi (Sch. Bip. ex Walp.) Vatke (Asteraceae) is one of the widely used anti-cancer traditional medicinal plants in Ethiopia, despite the lack of data to support its therapeutic efficacy. Here we describe the isolation of compounds from the plant and the investigation of their cytotoxicity and other bioactivities. We identified the novel sesquiterpene lactone (SL) 11ß,13-dihydrovernodalol along with the three other SLs (vernomenin, vernolepin, and 11ß,13-dihydrovernodalin) and three flavonoids (apigenin, eriodyctiol, and luteolin) isolated from this plant for the first time. The structures of all the compounds were established based on extensive analysis of nuclear magnetic resonance spectroscopic data and confirmed by high-resolution electrospray ionization mass spectrometry. We then studied the biological activities of the SLs and found that all were cytotoxic at low μM ranges against MCF-7 and JIMT-1 breast cancer cells as well as against the normal-like MCF-10A breast epithelial cells evaluated in a spectrophotometric assay. All the SLs significantly reduced JIMT-1 cell migration after 72 h of treatment with 2 μM concentrations in a wound healing assay. Treatment with all SLs reduced the aldehyde dehydrogenase expressing cancer stem cell sub-population of the JIMT-1 cells significantly, evaluated by flow cytometry. Only 11ß,13-dihydrovernodalin resulted in a significant inhibition of tumor necrosis factor-α-induced translocation of nuclear factor κB to the cell nucleus. In addition, we show that the reporter fluorophore nitrobenzoxadiazole (NBD) can successfully be conjugated with an SL and that this SL-NBD conjugate is taken up efficiently in JIMT-1 cells. Therefore, the overall bioactivities of the SL compounds and specifically their effects against the stemness of breast cancer cells make them prime candidates for further in-depth investigation.
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