| 1. |
- Brnjic, Slavica, et al.
(författare)
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Induction of Tumor Cell Apoptosis by a Proteasome Deubiquitinase Inhibitor Is Associated with Oxidative Stress
- 2014
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Ingår i: Antioxidants and Redox Signaling. - : Mary Ann Liebert Inc. - 1523-0864 .- 1557-7716. ; 21:17, s. 2271-2285
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Tidskriftsartikel (refereegranskat)abstract
- Aims: b-AP15 is a recently described inhibitor of the USP14/UCHL5 deubiquitinases (DUBs) of the 19S proteasome. Exposure to b-AP15 results in blocking of proteasome function and accumulation of polyubiquitinated protein substrates in cells. This novel mechanism of proteasome inhibition may potentially be exploited for cancer therapy, in particular for treatment of malignancies resistant to currently used proteasome inhibitors. The aim of the present study was to characterize the cellular response to b-AP15-mediated proteasome DUB inhibition. Results: We report that b-AP15 elicits a similar, but yet distinct, cellular response as the clinically used proteasome inhibitor bortezomib. b-AP15 induces a rapid apoptotic response, associated with enhanced induction of oxidative stress and rapid activation of Jun-N-terminal kinase 1/2 (JNK)/activating protein-1 signaling. Scavenging of reactive oxygen species and pharmacological inhibition of JNK reduced b-AP15-induced apoptosis. We further report that endoplasmic reticulum (ER) stress is induced by b-AP15 and is involved in apoptosis induction. In contrast to bortezomib, ER stress is associated with induction of alpha-subunit of eukaryotic initiation factor 2 phosphorylation. Innovation: The findings establish that different modes of proteasome inhibition result in distinct cellular responses, a finding of potential therapeutic importance. Conclusion: Our data show that enhanced oxidative stress and ER stress are major determinants of the strong apoptotic response elicited by the 19S DUB inhibitor b-AP15. Antioxid. Redox Signal. 21, 2271-2285.
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| 2. |
- D'Arcy, Pádraig, et al.
(författare)
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Inhibition of proteasome deubiquitinating activity as a novel cancer therapy
- 2011
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Ingår i: Nature Medicine. - Stockholm : Karolinska Institutet, Dept of Oncology-Pathology. - 1546-170X .- 1078-8956.
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Tidskriftsartikel (refereegranskat)abstract
- Ubiquitin-tagged substrates are degraded by the 26S proteasome, which is a multisubunit complex comprising a proteolytic 20S core particle capped by 19S regulatory particles. The approval of bortezomib for the treatment of multiple myeloma validated the 20S core particle as an anticancer drug target. Here we describe the small molecule b-AP15 as a previously unidentified class of proteasome inhibitor that abrogates the deubiquitinating activity of the 19S regulatory particle. b-AP15 inhibited the activity of two 19S regulatory-particle-associated deubiquitinases, ubiquitin C-terminal hydrolase 5 (UCHL5) and ubiquitin-specific peptidase 14 (USP14), resulting in accumulation of polyubiquitin. b-AP15 induced tumor cell apoptosis that was insensitive to TP53 status and overexpression of the apoptosis inhibitor BCL2. We show that treatment with b-AP15 inhibited tumor progression in four different in vivo solid tumor models and inhibited organ infiltration in an acute myeloid leukemia model. Our results show that the deubiquitinating activity of the 19S regulatory particle is a new anticancer drug target.
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| 3. |
- Fayad, Walid, et al.
(författare)
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Identification of a novel topoisomerase inhibitor effective in cells overexpressing drug efflux transporters
- 2009
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 4:10, s. e7238-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Natural product structures have high chemical diversity and are attractive as lead structures for discovery of new drugs. One of the disease areas where natural products are most frequently used as therapeutics is oncology. METHOD AND FINDINGS: A library of natural products (NCI Natural Product set) was screened for compounds that induce apoptosis of HCT116 colon carcinoma cells using an assay that measures an endogenous caspase-cleavage product. One of the apoptosis-inducing compounds identified in the screen was thaspine (taspine), an alkaloid from the South American tree Croton lechleri. The cortex of this tree is used for medicinal purposes by tribes in the Amazonas basin. Thaspine was found to induce conformational activation of the pro-apoptotic proteins Bak and Bax, mitochondrial cytochrome c release and mitochondrial membrane permeabilization in HCT116 cells. Analysis of the gene expression signature of thaspine-treated cells suggested that thaspine is a topoisomerase inhibitor. Inhibition of both topoisomerase I and II was observed using in vitro assays, and thaspine was found to have a reduced cytotoxic effect on a cell line with a mutated topoisomerase II enzyme. Interestingly, in contrast to the topoisomerase II inhibitors doxorubicin, etoposide and mitoxantrone, thaspine was cytotoxic to cell lines overexpressing the PgP or MRP drug efflux transporters. We finally show that thaspine induces wide-spread apoptosis in colon carcinoma multicellular spheroids and that apoptosis is induced in two xenograft mouse models in vivo. CONCLUSIONS: The alkaloid thaspine from the cortex of Croton lechleri is a dual topoisomerase inhibitor effective in cells overexpressing drug efflux transporters and induces wide-spread apoptosis in multicellular spheroids.
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| 4. |
- Hernlund, Emma, et al.
(författare)
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The phosphoinositide 3-kinase/mammalian target of rapamycin inhibitor NVP-BEZ235 is effective in inhibiting regrowth of tumour cells after cytotoxic therapy
- 2012
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Ingår i: European Journal of Cancer. - : Elsevier BV. - 0959-8049 .- 1879-0852. ; 48:3, s. 396-406
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE:Regrowth of tumour cells between cycles of chemotherapy is a significant clinical problem. Treatment strategies where antiproliferative agents are used to inhibit tumour regrowth between chemotherapy cycles are attractive, but such strategies are difficult to test using conventional monolayer culture systems.METHODS:We used the in vitro tumour spheroid model to study regrowth of 3-D colon carcinoma tissue after cytotoxic therapy. Colon carcinoma cells with wild-type or mutant phosphatidyl inositol 3-kinase catalytic subunit (PI3KCA) or KRAS alleles were allowed to form multicellular spheroids and the effects of different pharmacological compounds were studied after sectioning and staining for relevant markers of cell proliferation and apoptosis.RESULTS:Studies using colon cancer cells with gene disruptions suggested that the phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) pathway was essential for proliferation in 3-D culture. The dual PI3K-mTOR inhibitor NVP-BEZ235, currently in clinical trials, was found to inhibit phosphorylation of the mTOR target 4EBP1 in 3-D cultured cells. The ability of NVP-BEZ235 to inhibit tumour cell proliferation and to induce apoptosis was markedly more pronounced in 3-D cultures compared to monolayer cultures. It was subsequently found that NVP-BEZ235 was effective in inhibiting regrowth of 3-D cultured cells after treatment with two cytotoxic inhibitors of the ubiquitin-proteasome system (UPS), methyl-13-hydroxy-15-oxokaurenoate (MHOK) and bortezomib (Velcade®).CONCLUSIONS:The dual PI3K-mTOR inhibitor NVP-BEZ235 was found to reduce cell proliferation and to induce apoptosis in 3-D cultured colon carcinoma cells, NVP-BEZ235 is a promising candidate for use in sequential treatment modalities together with cytotoxic drugs to reduce the cell mass of solid tumours.
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| 5. |
- Hillert, Ellin-Kristina, et al.
(författare)
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Proteasome inhibitor b-AP15 induces enhanced proteotoxicity by inhibiting cytoprotective aggresome formation
- 2019
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Ingår i: Cancer Letters. - : ELSEVIER IRELAND LTD. - 0304-3835 .- 1872-7980. ; 448, s. 70-83
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Tidskriftsartikel (refereegranskat)abstract
- Proteasome inhibitors have been shown to induce cell death in cancer cells by triggering an acute proteotoxic stress response characterized by accumulation of poly-ubiquitinated proteins, ER stress and the production of reactive oxygen species. The aggresome pathway has been described as an escape mechanism from proteotoxicity by sequestering toxic cellular aggregates. Here we show that b-AP15, a small-molecule inhibitor of proteasomal deubiquitinase activity, induces poly-ubiquitin accumulation in absence of aggresome formation. b-AP15 was found to affect organelle transport in treated cells, raising the possibility that microtubule-transport of toxic protein aggregates is inhibited, leading to enhanced cytotoxicity. In contrast to the antiproliferative effects of the clinically used proteasome inhibitor bortezomib, the effects of b-AP15 are not further enhanced by the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA). Our results suggest an inhibitory effect of b-AP15 on the transport of misfolded proteins, resulting in a lack of aggresome formation, and a strong proteotoxic stress response.
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| 6. |
- Kolosenko, Iryna, et al.
(författare)
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Cell crowding induces interferon regulatory factor 9, which confers resistance to chemotherapeutic drugs
- 2015
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Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 136:4, s. E51-E61
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of multicellular drug resistance, defined as the reduced efficacy of chemotherapeutic drugs in solid tumors is incompletely understood. Here we report that colon carcinoma cells cultured as 3D microtissues (spheroids) display dramatic increases in the expression of a subset of type I interferon-(IFN)-stimulated genes (ISGs). A similar gene signature was associated previously with resistance to radiation and chemotherapy, prompting us to examine the underlying biological mechanisms. Analysis of spheroids formed by different tumor cell lines and studies using knock-down of gene expression showed that cell crowding leads to the induction of IFN regulatory factor-9 (IRF9) which together with STAT2 and independently of IFNs, is necessary for ISG upregulation. Increased expression of IRF9 alone was sufficient to induce the ISG subset in monolayer cells and to confer increased resistance to clinically used cytotoxic drugs. Our data reveal a novel mechanism of regulation of a subset of ISGs, leading to drug resistance in solid tumors. What's new? Drug resistance remains a major challenge in the management of cancer patients. Using a 3D model of tumor cells the authors identify cell crowding and the interferon response as important mediators of drug resistance. They demonstrate that interferon regulatory factor 9 (IRF9) and a panel of interferon-stimulated genes are induced by cell crowding in this model. These results link unexpected new molecular mechanisms with the therapy resistance of solid tumors.
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