| 1. |
- Eshtad, Saeed
(författare)
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Targeting DNA repair pathways for cancer therapy
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Accumulation of genomic mutations is the consequence of failure in DNA repair as well as increased exposure to endogenous/environmental mutagens. DNA repair pathways safeguard the human genome from such mutagens, and thereby suppress the multi-step process of carcinogenesis. DNA repair pathways that protect the genome from ROS (reactive oxygen species)-induced lesions are attractive anti-cancer targets, as their inhibition may render combinatorial sensitization of tumor cells to both DNA damage and oxidative stresses, known as non-oncogenic addictions of cancer. The aim of this thesis was to validate such DNA repair factors as anti-cancer targets and to develop their inhibitors for potential therapeutic applications. In paper I, we assessed the addiction of cancer cells to MTH1, a nudix hydrolase eliminating oxidized purine nucleotides from the dNTP pool. MTH1 depletion resulted in exclusive accumulation of 8-oxo-dG lesions and cellular toxicity in transformed cells. MTH1 suppression, impaired tumor growth in the xenografts of SW480 cells. We developed potent MTH1 inhibitors (TH278 and TH588), which exhibited target engagement and selective toxicity in transformed cells. Treatment with MTH1 inhibitors caused increased 8-oxo-dG levels in cancer cells, and inhibited the growth of xenografts in vivo. Taken together, our findings revealed the dependency of tumors to MTH1 that can be targeted for cancer therapy. The study in paper II aimed to explore functional cooperation between MTH1 and MUTYH, a DNA glycosylase that removes deoxyadenines paired with 8-oxo-dG. Using stable cell lines expressing inducible shRNA constructs, we showed that combined depletion of MTH1 and MUTYH was more toxic to cells compared to individual knock-downs. In addition, overexpression of nuclear MUTYH could attenuate cell death induced by loss of MTH1. Collectively, this study provided supportive evidence for a protective role of MUTYH. In paper III, we described TH5487 as a novel selective inhibitor of OGG1, a DNA glycosylase that excises 8-oxo-dG opposite deoxycytidine. TH5487 inhibited binding of OGG1 to its substrate and increased thermal stability of the purified protein through interactions with residues in the active site. Moreover, TH5487 engaged with its intended target, increased 8-oxo-dG level, and impaired recruitment of OGG1 to the damage site in cells. Treatment with TH5487 resulted in prolonged S phase, which was similar to the effect of OGG1 depletion using shRNAs. In addition, non-transformed cells could tolerate TH5487 treatment while cancer cells were more sensitive. In sum, this study highlighted the phenotypic lethality of OGG1 inhibition with tumors, by introducing TH5487 as a cell-active OGG1 inhibitor. Overall, our results increased the knowledge about dependency of cancer cells to DNA repair pathways of ROS-induced lesions that can be employed for the development of promising anti-tumor therapies.
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| 2. |
- Gad, Helge, et al.
(författare)
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MTH1 inhibition eradicates cancer by preventing sanitation of the dNTP pool
- 2014
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 508:7495, s. 215-221
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Tidskriftsartikel (refereegranskat)abstract
- Cancers have dysfunctional redox regulation resulting in reactive oxygen species production, damaging both DNA and free dNTPs. The MTH1 protein sanitizes oxidized dNTP pools to prevent incorporation of damaged bases during DNA replication. Although MTH1 is non-essential in normal cells, we show that cancer cells require MTH1 activity to avoid incorporation of oxidized dNTPs, resulting in DNA damage and cell death. We validate MTH1 as an anticancer target in vivo and describe small molecules TH287 and TH588 as first-in-class nudix hydrolase family inhibitors that potently and selectively engage and inhibit the MTH1 protein in cells. Protein co-crystal structures demonstrate that the inhibitors bindin the active site of MTH1. The inhibitors cause incorporation of oxidized dNTPs in cancer cells, leading to DNA damage, cytotoxicity and therapeutic responses in patient-derived mouse xenografts. This study exemplifies the non-oncogene addiction concept for anticancer treatment and validates MTH1 as being cancer phenotypic lethal.
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| 3. |
- Visnes, Torkild, et al.
(författare)
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Targeting OGG1 arrests cancer cell proliferation by inducing replication stress
- 2020
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 48:21, s. 12234-12251
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Tidskriftsartikel (refereegranskat)abstract
- Altered oncogene expression in cancer cells causes loss of redox homeostasis resulting in oxidative DNA damage, e.g. 8-oxoguanine (8-oxoG), repaired by base excision repair (BER). PARP1 coordinates BER and relies on the upstream 8-oxoguanine-DNA glycosylase (OGG1) to recognise and excise 8-oxoG. Here we hypothesize that OGG1 may represent an attractive target to exploit reactive oxygen species (ROS) elevation in cancer. Although OGG1 depletion is well tolerated in non-transformed cells, we report here that OGG1 depletion obstructs A3 T-cell lymphoblastic acute leukemia growth in vitro and in vivo, validating OGG1 as a potential anti-cancer target. In line with this hypothesis, we show that OGG1 inhibitors (OGG1i) target a wide range of cancer cells, with a favourable therapeutic index compared to non-transformed cells. Mechanistically, OGG1i and shRNA depletion cause S-phase DNA damage, replication stress and proliferation arrest or cell death, representing a novel mechanistic approach to target cancer. This study adds OGG1 to the list of BER factors, e.g. PARP1, as potential targets for cancer treatment.
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| 4. |
- Zhang, Si Min, et al.
(författare)
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Development of a chemical probe against NUDT15
- 2020
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Ingår i: Nature Chemical Biology. - : Springer Science and Business Media LLC. - 1552-4450 .- 1552-4469. ; 16:10, s. 1120-1128
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Tidskriftsartikel (refereegranskat)abstract
- The NUDIX hydrolase NUDT15 was originally implicated in sanitizing oxidized nucleotides, but was later shown to hydrolyze the active thiopurine metabolites, 6-thio-(d)GTP, thereby dictating the clinical response of this standard-of-care treatment for leukemia and inflammatory diseases. Nonetheless, its physiological roles remain elusive. Here, we sought to develop small-molecule NUDT15 inhibitors to elucidate its biological functions and potentially to improve NUDT15-dependent chemotherapeutics. Lead compound TH1760 demonstrated low-nanomolar biochemical potency through direct and specific binding into the NUDT15 catalytic pocket and engaged cellular NUDT15 in the low-micromolar range. We also employed thiopurine potentiation as a proxy functional readout and demonstrated that TH1760 sensitized cells to 6-thioguanine through enhanced accumulation of 6-thio-(d)GTP in nucleic acids. A biochemically validated, inactive structural analog, TH7285, confirmed that increased thiopurine toxicity takes place via direct NUDT15 inhibition. In conclusion, TH1760 represents the first chemical probe for interrogating NUDT15 biology and potential therapeutic avenues.
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