| 1. |
- Gubat, Johannes, 1986-, et al.
(författare)
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Comprehensive Target Screening and Cellular Profiling of the Cancer-Active Compound b-AP15 Indicate Abrogation of Protein Homeostasis and Organelle Dysfunction as the Primary Mechanism of Action
- 2022
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Ingår i: Frontiers in Oncology. - : Frontiers Media SA. - 2234-943X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Dienone compounds have been demonstrated to display tumor-selective anti-cancer activity independently of the mutational status of TP53. Previous studies have shown that cell death elicited by this class of compounds is associated with inhibition of the ubiquitin-proteasome system (UPS). Here we extend previous findings by showing that the dienone compound b-AP15 inhibits proteasomal degradation of long-lived proteins. We show that exposure to b-AP15 results in increased association of the chaperones VCP/p97/Cdc48 and BAG6 with proteasomes. Comparisons between the gene expression profile generated by b-AP15 to those elicited by siRNA showed that knock-down of the proteasome-associated deubiquitinase (DUB) USP14 is the closest related to drug response. USP14 is a validated target for b-AP15 and we show that b-AP15 binds covalently to two cysteines, Cys203 and Cys257, in the ubiquitin-binding pocket of the enzyme. Consistent with this, deletion of USP14 resulted in decreased sensitivity to b-AP15. Targeting of USP14 was, however, found to not fully account for the observed proteasome inhibition. In search for additional targets, we utilized genome-wide CRISPR/Cas9 library screening and Proteome Integral Solubility Alteration (PISA) to identify mechanistically essential genes and b-AP15 interacting proteins respectively. Deletion of genes encoding mitochondrial proteins decreased the sensitivity to b-AP15, suggesting that mitochondrial dysfunction is coupled to cell death induced by b-AP15. Enzymes known to be involved in Phase II detoxification such as aldo-ketoreductases and glutathione-S-transferases were identified as b-AP15-targets using PISA. The finding that different exploratory approaches yielded different results may be explained in terms of a “target” not necessarily connected to the “mechanism of action” thus highlighting the importance of a holistic approach in the identification of drug targets. We conclude that b-AP15, and likely also other dienone compounds of the same class, affect protein degradation and proteasome function at more than one level.
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| 2. |
- Gubat, Johannes, 1986-
(författare)
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Identifying Essential Deubiquitinase Interactions and Targeting Protein Ubiquitination in Cancer
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cancer is the second leading cause of death globally and is one of the most pressing health issues today. While significant advances have been made in cancer treatment, drug resistance and toxicity remain formidable obstacles to successful therapy. Thus, there is a need to find novel targets that pave the way for new cancer therapeutics. Ubiquitination, the process of tagging substrate proteins with ubiquitin molecules, regulates many of the pathways that underlie cancer progression. This thesis aims to explore innovative strategies for combating cancer by focusing on crucial elements within the ubiquitination machinery, specifically the Ubiquitin-Proteasome System (UPS) and deubiquitinases (DUBs). In Paper I, we employed the Connectivity Map to discern UPS inhibitors by analyzing the gene expression patterns of various compounds in comparison to those induced by proteasome perturbation. In Paper II, we employed orthogonal methods to identify the primary mechanism for the cytotoxicity of b-AP15. Here, we showed that pharmacologic doses of b-AP15 resulted in strong proteasome inhibition and that cytotoxicity is mediated through the mitochondria and influenced by the proteasome-associated DUB, USP14. In Paper III, we explored the role of USP14 in colorectal cancer cells and evaluated its potential as a cancer target. We found that the genetic deletion of USP14 confers a quiescent phenotype to cancer cells. In Paper IV, we used CRISPR-based screens to search for new deubiquitinase targets. We identified deubiquitinase interactions essential for cancer and explored the possibility of combinatorial deubiquitinase targeting. We pinpointed highly-networked deubiquitinases (PSMD14, USP9X, USP39, and USP7) and deubiquitinase pairs represent promising drug targets. This thesis underscores the importance of the ubiquitination process in the search for novel cancer therapeutics and provides new avenues to explore in developing therapies based on the inhibition of deubiquitinases.
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| 3. |
- Min, Liu, et al.
(författare)
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Clinical efficacy of irinotecan plus raltitrexed chemotherapy in refractory esophageal squamous cell cancer
- 2020
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Ingår i: Anti-Cancer Drugs. - : LIPPINCOTT WILLIAMS & WILKINS. - 0959-4973 .- 1473-5741. ; 31:4, s. 403-410
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Tidskriftsartikel (refereegranskat)abstract
- Our retrospective study assessed the efficacy and safety of irinotecan plus raltitrexed in esophageal squamous cell cancer (ESCC) patients who were previously treated with multiple systemic therapies. Between January 2016 and December 2018, records of 38 ESCC patients who underwent irinotecan plus raltitrexed chemotherapy after at least one line of chemotherapy were reviewed. Efficacy assessment was performed every two cycles according to the RECIST version 1.1. A total of 95 cycles of chemotherapy were administered, and the median course was 3 (range 2-6). There was no treatment-related death. Nine patients had partial response, 21 had stable disease and eight had progressive disease. The overall objective response rate was 23.68% (9/38) and the disease control rate was78.94% (30/38). After a median follow-up of 18.5 months, the median progression-free survival and overall survival were 105 and 221 days, respectively. There were five patients (13.15%) with grade 3/4 leukopenia, three patients (7.89%) with grade 3/4 neutropenia and one patient (2.63%) with grade 3/4 diarrhea. The combination of irinotecan plus raltitrexed was effective for pretreated ESCC patients. Further studies are needed to determine the optimal dose of the two drugs.
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| 4. |
- Mofers, Arjan, et al.
(författare)
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Identification of proteasome inhibitors using analysis of gene expression profiles
- 2020
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Ingår i: European Journal of Pharmacology. - : ELSEVIER. - 0014-2999 .- 1879-0712. ; 889
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Tidskriftsartikel (refereegranskat)abstract
- Inhibitors of the 20S proteasome such as bortezomib (Velcade((R))) and carfilzomib (Kypriolis((R))) are in clinical use for the treatment of patients with multiple myeloma and mantle cell lymphoma. In an attempt to identify novel inhibitors of the ubiquitin-proteasome system (UPS) we used the connectivity map (CMap) resource, based on alterations of gene expression profiles by perturbagens, and performed COMPARE analyses of drug sensitivity patterns in the NCI60 panel. Cmap analysis identified a large number of small molecules with strong connectivity to proteasome inhibition, including both well characterized inhibitors of the 20S proteasome and molecules previously not described to inhibit the UPS. A number of these compounds have been reported to be cytotoxic to tumor cells and were tested for their ability to decrease processing of proteasome substrates. The antibiotic thiostrepton and the natural products celastrol and curcumin induced strong accumulation of polyubiquitinated proteasome substrates in exposed cells. Other compounds elicited modest increases of proteasome substrates, including the protein phosphatase inhibitor BCI-Cl and the farnesyltransferase inhibitor manumycin A, suggesting that these compounds inhibit proteasome function. Induction of chaperone expression in the absence of proteasome inhibition was observed by a number of compounds, suggesting other effects on the UPS. We conclude that the combination of bioinformatic analyses and cellular assays resulted in the identification of compounds with potential to inhibit the UPS.
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| 5. |
- Selvaraju, Karthik, et al.
(författare)
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Sensitivity of Acute Myelocytic Leukemia Cells to the Dienone Compound VLX1570 Is Associated with Inhibition of the Ubiquitin-Proteasome System
- 2021
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Ingår i: Biomolecules. - : MDPI. - 2218-273X. ; 11:9
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Tidskriftsartikel (refereegranskat)abstract
- Dienone compounds with a 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore have been widely reported to show tumor cell selectivity. These compounds target the ubiquitin-proteasome system (UPS), known to be essential for the viability of tumor cells. The induction of oxidative stress, depletion of glutathione, and induction of high-molecular-weight (HMW) complexes have also been reported. We here examined the response of acute myeloid leukemia (AML) cells to the dienone compound VLX1570. AML cells have relatively high protein turnover rates and have also been reported to be sensitive to depletion of reduced glutathione. We found AML cells of diverse cytogenetic backgrounds to be sensitive to VLX1570, with drug exposure resulting in an accumulation of ubiquitin complexes, induction of ER stress, and the loss of cell viability in a dose-dependent manner. Caspase activation was observed but was not required for the loss of cell viability. Glutathione depletion was also observed but did not correlate to VLX1570 sensitivity. Formation of HMW complexes occurred at higher concentrations of VLX1570 than those required for the loss of cell viability and was not enhanced by glutathione depletion. To study the effect of VLX1570 we developed a zebrafish PDX model of AML and confirmed antigrowth activity in vivo. Our results show that VLX1570 induces UPS inhibition in AML cells and encourage further work in developing compounds useful for cancer therapeutics.
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| 6. |
- Wang, Tao, et al.
(författare)
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The benefit of taxane-based therapies over fluoropyrimidine plus platinum (FP) in the treatment of esophageal cancer : a meta-analysis of clinical studies
- 2019
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Ingår i: Drug Design, Development and Therapy. - 1177-8881. ; 13, s. 539-553
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Fluoropyrimidine plus platinum (FP) is currently the standard treatment for esophageal cancer (EC). In recent years, taxane-based chemotherapy has also been used and has shown good efficacy in EC. This study aims to investigate the advantages of taxane-based over FP chemotherapy, as well as discuss its drawbacks, in the treatment of EC. Patients and methods: A literature search was done for studies comparing clinical outcomes between taxane-based and FP chemotherapy in EC. Pooled analyses were performed to compare the efficacy and grade 3/4 adverse events in patients who received neoadjuvant chemotherapy (NACT), neoadjuvant chemoradiotherapy (NACRT), or definitive chemoradiotherapy (dCRT). Subgroup analyses were also conducted in esophageal squamous cell carcinoma (ESCC). Results: Thirty-one studies with a total of 3,912 patients were included in the analysis. Better long-term survival was found in patients who received taxane-based NACT (progression-free survival (PFS): pooled HR=0.58, P=0.0008; and overall survival (OS): pooled HR=0.50, P<0.00001) and dCRT (PFS: pooled HR=0.75, P<0.0001). In NACRT, taxane-based treatment and FP showed similar efficacy. In ESCC patients, taxane-based treatment showed better OS (NACT: pooled HR=0.57, P=0.02; NACRT: pooled HR=0.51, P=0.03; and dCRT: pooled HR=0.73, P<0.0001) than FP chemotherapy. Furthermore, taxane-based therapy also showed a better short-term response (complete response (CR), objective response rate (ORR), disease control rate (DCR), or pathologic complete response (pCR). However, taxane-based therapy was significantly correlated with a higher incidence of grade 3/4 leukopenia, neutropenia, and diarrhea. Conclusion: Compared to FP, taxane-based therapy produced better clinical response and outcomes in EC patients receiving NACT or dCRT, and in all types of therapy in patients with ESCC. Taxane-based treatment is associated with more frequent toxicity.
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