| 1. |
- Bräutigam, Lars, et al.
(författare)
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Hypoxic Signaling and the Cellular Redox Tumor Environment Determine Sensitivity to MTH1 Inhibition
- 2016
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Ingår i: Cancer Research. - 0008-5472 .- 1538-7445. ; 76:8, s. 2366-2375
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Tidskriftsartikel (refereegranskat)abstract
- Cancer cells are commonly in a state of redox imbalance that drives their growth and survival. To compensate for oxidative stress induced by the tumor redox environment, cancer cells upregulate specific nononcogenic addiction enzymes, such as MTH1 (NUDT1), which detoxifies oxidized nucleotides. Here, we show that increasing oxidative stress in nonmalignant cells induced their sensitization to the effects of MTH1 inhibition, whereas decreasing oxidative pressure in cancer cells protected against inhibition. Furthermore, we purified zebrafish MTH1 and solved the crystal structure of MTH1 bound to its inhibitor, highlighting the zebrafish as a relevant tool to study MTH1 biology. Delivery of 8-oxo-dGTP and 2-OH-dATP to zebrafish embryos was highly toxic in the absence of MTH1 activity. Moreover, chemically or genetically mimicking activated hypoxia signaling in zebrafish revealed that pathologic upregulation of the HIF1 alpha response, often observed in cancer and linked to poor prognosis, sensitized embryos to MTH1 inhibition. Using a transgenic zebrafish line, in which the cellular redox status can be monitored in vivo, we detected an increase in oxidative pressure upon activation of hypoxic signaling. Pretreatment with the antioxidant N-acetyl-L-cysteine protected embryos with activated hypoxia signaling against MTH1 inhibition, suggesting that the aberrant redox environment likely causes sensitization. In summary, MTH1 inhibition may offer a general approach to treat cancers characterized by deregulated hypoxia signaling or redox imbalance.
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| 2. |
- Narwal, Mohit, et al.
(författare)
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Crystal Structures and Inhibitor Interactions of Mouse and Dog MTH1 Reveal Species-Specific Differences in Affinity
- 2018
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 57:5, s. 593-603
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Tidskriftsartikel (refereegranskat)abstract
- MTH1 hydrolyzes oxidized nucleoside triphosphates, thereby sanitizing the nucleotide pool from oxidative damage. This prevents incorporation of damaged nucleotides into DNA, which otherwise would lead to mutations and cell death. The high level of reactive oxygen species in cancer cells leads to a higher level of oxidized nucleotides in cancer cells compared to non-malignant cells making cancer cells more dependent on MTH1 for survival. The possibility to specifically target cancer cells by inhibiting MTH1 has highlighted MTH1 as a promising cancer target. Progression of MTH1 inhibitors into the clinic requires animal studies and knowledge about species differences in potency of inhibitors are of vital importance. We here show that the human MTH1 inhibitor TH588 is approximately twenty fold less potent for inhibition of mouse MTH1 compared to human, rat, pig, and dog MTH1. We present the crystal structures of mouse MTH1 in complex with TH588 and dog MTH1and elucidate the structural and sequence basis for the observed difference in affinity for TH588. We identify amino acid residue 116 in MTH1 as an important determinant for TH588 affinity. Furthermore, we present the structure of mouse MTH1 in complex with the substrate 8-oxo-dGTP. The crystal structures provide insight into the high degree of structural conservation between MTH1 from different organisms and provide a detailed view of interactions between MTH1 and the inhibitor, revealing that minute structural differences can have a large impact on affinity and specificity.
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