| 1. |
- Pellegrini, Paola, 1986-, et al.
(författare)
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Induction of ER Stress in Acute Lymphoblastic Leukemia Cells by the Deubiquitinase Inhibitor VLX1570
- 2020
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 21:13
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Tidskriftsartikel (refereegranskat)abstract
- The proteasome is a validated target of cancer therapeutics. Inhibition of proteasome activity results in the activation of the unfolded protein response (UPR) characterized by phosphorylation of eukaryotic initiation factor 2 alpha (eIF2 alpha), global translational arrest, and increased expression of the proapoptotic CHOP (C/EBP homologous protein) protein. Defects in the UPR response has been reported to result in altered sensitivity of tumor cells to proteasome inhibitors. Here, we characterized the effects of the deubiquitinase (DUB) inhibitor VLX1570 on protein homeostasis, both at the level of the UPR and on protein translation, in acute lymphoblastic leukemia (ALL). Similar to the 20S inhibitor bortezomib, VLX1570 induced accumulation of polyubiquitinated proteins and increased expression of the chaperone Grp78/Bip in ALL cells. Both compounds induced cleavage of PARP (Poly (ADP-ribose) polymerase) in ALL cells, consistent with induction of apoptosis. However, and in contrast to bortezomib, VLX1570 treatment resulted in limited induction of the proapoptotic CHOP protein. Translational inhibition was observed by both bortezomib and VLX1570. We report that in distinction to bortezomib, suppression of translation by VXL1570 occurred at the level of elongation. Increased levels of Hsc70/Hsp70 proteins were observed on polysomes following exposure to VLX1570, possibly suggesting defects in nascent protein folding. Our findings demonstrate apoptosis induction in ALL cells that appears to be uncoupled from CHOP induction, and show that VLX1570 suppresses protein translation by a mechanism distinct from that of bortezomib.
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| 2. |
- Bengtsson, Sofia, et al.
(författare)
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Large-scale proteomics analysis of human ovarian cancer for biomarkers
- 2007
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Ingår i: Journal of Proteome Research. - : American Chemical Society (ACS). - 1535-3893 .- 1535-3907. ; 6:4, s. 1440-1450
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Tidskriftsartikel (refereegranskat)abstract
- Ovarian cancer is usually found at a late stage when the prognosis is often bad. Relative survival rates decrease with tumor stage or grade, and the 5-year survival rate for women with carcinoma is only 38%. Thus, there is a great need to find biomarkers that can be used to carry out routine screening, especially in high-risk patient groups. Here, we present a large-scale study of 64 tissue samples taken from patients at all stages and show that we can identify statistically valid markers using nonsupervised methods that distinguish between normal, benign, borderline, and malignant tissue. We have identified 217 of the significantly changing protein spots. We are expressing and raising antibodies to 35 of these. Currently, we have validated 5 of these antibodies for use in immunohistochemical analysis using tissue microarrays of healthy and diseased ovarian, as well as other, human tissues.
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| 3. |
- Eriksson, Ida, 1985-
(författare)
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Dealing with damaged lysosomes : Impact of lysosomal membrane stability in health and disease
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The lysosome is the main unit for degradation and plays important roles in various cellular processes, such as nutrient sensing, cholesterol regulation and cell death. Consequently, altered lysosomal function contributes to, or even causes, several diseases. Lysosomal membrane permeabilization (LMP) and release of lysosomal content to the cytosol can induce cell death, and is implicated in inflammation and neuronal decline in several neurodegenerative diseases. It has also emerged as a potential target in cancer therapy. Due to the detrimental effects of LMP, cells harbor several mechanisms to protect and prevent lysosomal membrane damage. The aim of this thesis was to elucidate how lysosomal membrane stability and repair mechanisms affect cell death and survival. We find that lysosomal cholesterol is upregulated in response to an increased load of reactive oxygen species in a Parkinson’s disease cell model, and that augmented cholesterol protects from LMP. However, cholesterol also induces accumulation of α-synuclein and inhibits lysosome-mediated degradation, which can destabilize the lysosomal membrane and accelerate the course of disease. Further, we demonstrate that lysosomal membrane damage is counteracted by a calcium-dependent repair mechanism to prevent LMP. Lysosomes damaged beyond repair are instead sequestered in an autophagosome and degraded by intact lysosomes in a process called lysophagy. As a result, small vesicles containing lysosomal membrane proteins are generated, which we believe are used to restore lysosomal function. We show that malignant cells are more sensitive to LMP, and that they differ in their activation of damage-response mechanisms compared to normal cells. Moreover, in malignant cells, the intracellular position of the lysosomes determines the susceptibility to lysosomal damage. Peripherally located lysosomes are less sensitive, and by relocating lysosomes to the perinuclear area in the cell, we can sensitize lysosomes to LMP induction. In summary, this thesis demonstrates the importance of damage-response mechanisms to protect from lysosomal membrane damage and maintain cellular function. It also indicates that targeting of lysosomal stability and repair is a potential therapeutic strategy in both neurodegenerative diseases and in cancer.
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| 4. |
- Ma, Ran, et al.
(författare)
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Estrogen Receptor β as a Therapeutic Target in Breast Cancer Stem Cells.
- 2017
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Ingår i: Journal of the National Cancer Institute. - : Oxford University Press. - 0027-8874 .- 1460-2105. ; 109:3, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Background: Breast cancer cells with tumor-initiating capabilities (BSCs) are considered to maintain tumor growth and govern metastasis. Hence, targeting BSCs will be crucial to achieve successful treatment of breast cancer.Methods: We characterized mammospheres derived from more than 40 cancer patients and two breast cancer cell lines for the expression of estrogen receptors (ERs) and stem cell markers. Mammosphere formation and proliferation assays were performed on cells from 19 cancer patients and five healthy individuals after incubation with ER-subtype selective ligands. Transcriptional analysis was performed to identify pathways activated in ERβ-stimulated mammospheres and verified using in vitro experiments. Xenograft models (n = 4 or 5 per group) were used to study the role of ERs during tumorigenesis.Results: We identified an absence of ERα but upregulation of ERβ in BSCs associated with phenotypic stem cell markers and responsible for the proliferative role of estrogens. Knockdown of ERβ caused a reduction of mammosphere formation in cell lines and in patient-derived cancer cells (40.7%, 26.8%, and 39.1%, respectively). Gene set enrichment analysis identified glycolysis-related pathways (false discovery rate < 0.001) upregulated in ERβ-activated mammospheres. We observed that tamoxifen or fulvestrant alone was insufficient to block proliferation of patient-derived BSCs while this could be accomplished by a selective inhibitor of ERβ (PHTPP; 53.7% in luminal and 45.5% in triple-negative breast cancers). Furthermore, PHTPP reduced tumor initiation in two patient-derived xenografts (75.9% and 59.1% reduction in tumor volume, respectively) and potentiated tamoxifen-mediated inhibition of tumor growth in MCF7 xenografts.Conclusion: We identify ERβ as a mediator of estrogen action in BSCs and a novel target for endocrine therapy.
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| 5. |
- Mazurkiewicz, Magdalena, et al.
(författare)
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Acute lymphoblastic leukemia cells are sensitive to disturbances in protein homeostasis induced by proteasome deubiquitinase inhibition
- 2017
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Ingår i: Oncotarget. - : IMPACT JOURNALS LLC. - 1949-2553. ; 8:13, s. 21115-21127
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Tidskriftsartikel (refereegranskat)abstract
- The non-genotoxic nature of proteasome inhibition makes it an attractive therapeutic option for the treatment of pediatric malignancies. We recently described the small molecule VLX1570 as an inhibitor of proteasome deubiquitinase (DUB) activity that induces proteotoxic stress and apoptosis in cancer cells. Here we show that acute lymphoblastic leukemia (ALL) cells are highly sensitive to treatment with VLX1570, resulting in the accumulation of polyubiquitinated proteasome substrates and loss of cell viability. VLX1570 treatment increased the levels of a number of proteins, including the chaperone HSP70B , the oxidative stress marker heme oxygenase-1 (HO-1) and the cell cycle regulator p21(Cip1). Unexpectedly, polybiquitin accumulation was found to be uncoupled from ER stress in ALL cells. Thus, increased phosphorylation of eIF2a occurred only at supra-pharmacological VLX1570 concentrations and did not correlate with polybiquitin accumulation. Total cellular protein synthesis was found to decrease in the absence of eIF2a phosphorylation. Furthermore, ISRIB (Integrated Stress Response inhibitor) did not overcome the inhibition of protein synthesis. We finally show that VLX1570 can be combined with L-asparaginase for additive or synergistic antiproliferative effects on ALL cells. We conclude that ALL cells are highly sensitive to the proteasome DUB inhibitor VLX1570 suggesting a novel therapeutic option for this disease.
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| 6. |
- Ribeiro, Tiago, et al.
(författare)
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Cytotoxicity of portoamides in human cancer cells and analysis of the molecular mechanisms of action
- 2017
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- Portoamides are cyclic peptides produced and released by the cyanobacterial strain Phormidium sp. presumably to interfere with other organisms in their ecosystems (" allelopathy"). Portoamides were previously demonstrated to have an antiproliferative effect on human lung carcinoma cells, but the underlying mechanism of this activity has not been described. In the present work, the effects of portoamides on proliferation were examined in eight human cancer cell lines and two non-carcinogenic cell lines, and major differences in sensitivities were observed. To generate hypotheses with regard to molecular mechanisms of action, quantitative proteomics using 2D gel electrophoresis and MALDI-TOF/ TOF were performed on the colon carcinoma cell line HT-29. The expression of proteins involved in energy metabolism (mitochondrial respiratory chain and pentose phosphate pathway) was found to be affected. The hypothesis of altered energy metabolism was tested in further experiments. Exposure to portoamides resulted in reduced cellular ATP content, likely due to decreased mitochondrial energy production. Mitochondrial hyperpolarization and reduced mitochondrial reductive capacity was observed in treated cells. Furthermore, alterations in the expression of peroxiredoxins (PRDX4, PRDX6) and components of proteasome subunits (PSB4, PSA6) were observed in portoamide-treated cells, but these alterations were not associated with detectable increases in oxidative stress. We conclude that the cytotoxic activity of portoamides is associated with disturbance of energy metabolism, and alterations in mitochondrial structure and function.
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| 7. |
- Selvaraj, Karthik, et al.
(författare)
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Cytotoxic unsaturated electrophilic compounds commonly target the ubiquitin proteasome system
- 2019
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- A large number of natural products have been advocated as anticancer agents. Many of these compounds contain functional groups characterized by chemical reactivity. It is not clear whether distinct mechanisms of action can be attributed to such compounds. We used a chemical library screening approach to demonstrate that a substantial fraction (similar to 20%) of cytotoxic synthetic compounds containing Michael acceptor groups inhibit proteasome substrate processing and induce a cellular response characteristic of proteasome inhibition. Biochemical and structural analyses showed binding to and inhibition of proteasome-associated cysteine deubiquitinases, in particular ubiquitin specific peptidase 14 (USP14). The results suggested that compounds bind to a crevice close to the USP14 active site with modest affinity, followed by covalent binding. A subset of compounds was identified where cell death induction was closely associated with proteasome inhibition and that showed significant antineoplastic activity in a zebrafish embryo model. These findings suggest that proteasome inhibition is a relatively common mode of action by cytotoxic compounds containing Michael acceptor groups and help to explain previous reports on the antineoplastic effects of natural products containing such functional groups.
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| 8. |
- Zhang, Xiaonan, et al.
(författare)
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Drug Development Targeting the Ubiquitin-Proteasome System (UPS) for the Treatment of Human Cancers
- 2020
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Ingår i: Cancers. - : MDPI AG. - 2072-6694. ; 12:4
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Forskningsöversikt (refereegranskat)abstract
- Cancer cells are characterized by a higher rate of protein turnover and greater demand for protein homeostasis compared to normal cells. In this scenario, the ubiquitin-proteasome system (UPS), which is responsible for the degradation of over 80% of cellular proteins within mammalian cells, becomes vital to cancer cells, making the UPS a critical target for the discovery of novel cancer therapeutics. This review systematically categorizes all current reported small molecule inhibitors of the various essential components of the UPS, including ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), ubiquitin ligases (E3s), the 20S proteasome catalytic core particle (20S CP) and the 19S proteasome regulatory particles (19S RP), as well as their mechanism/s of action and limitations. We also discuss the immunoproteasome which is considered as a prospective therapeutic target of the next generation of proteasome inhibitors in cancer therapies.
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| 9. |
- Zhang, Xiaonan, et al.
(författare)
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Eradicating Quiescent Tumor Cells by Targeting Mitochondrial Bioenergetics
- 2016
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Ingår i: Trends in Cancer. - : Elsevier BV. - 2405-8025 .- 2405-8033. ; 2:11, s. 657-663
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Forskningsöversikt (refereegranskat)abstract
- The presence of quiescent cell populations in solid tumors represents a major challenge for disease eradication. Such cells are generally present in poorly vascularized tumor areas, show limited sensitivity to traditional chemotherapeutical drugs, and tend to resume proliferation, resulting in tumor reseeding and growth. There is growing recognition of the importance of developing therapies that target these quiescent cell populations to achieve long-lasting remission. Recent studies have shown that the combination of hypoxia and reduced nutrient availability in poorly vascularized areas results in limited tumor metabolic plasticity coupled with an increased sensitivity to perturbations in mitochondrial flux. Targeting of mitochondrial bioenergetics in these quiescent cell tumor populations may enable tumor eradication and improve the prognosis of patients with cancer.
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| 10. |
- Zhang, Xiaonan, et al.
(författare)
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MYC is downregulated by a mitochondrial checkpoint mechanism
- 2017
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Ingår i: Oncotarget. - : IMPACT JOURNALS LLC. - 1949-2553. ; 8:52, s. 90225-90237
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Tidskriftsartikel (refereegranskat)abstract
- The MYC proto-oncogene serves as a rheostat coupling mitogenic signaling with the activation of genes regulating growth, metabolism and mitochondrial biogenesis. Here we describe a novel link between mitochondria and MYC levels. Perturbation of mitochondrial function using a number of conventional and novel inhibitors resulted in the decreased expression of MYC mRNA. This decrease in MYC mRNA occurred concomitantly with an increase in the levels of tumor-suppressive miRNAs such as members of the let-7 family and miR-34a-5p. Knockdown of let-7 family or miR-34a-5p could partially restore MYC levels following mitochondria damage. We also identified let-7-dependent downregulation of the MYC mRNA chaperone, CRD-BP (coding region determinant-binding protein) as an additional control following mitochondria damage. Our data demonstrates the existence of a homeostasis mechanism whereby mitochondrial function controls MYC expression.
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