Dual Inhibitors of 8-Oxoguanine Surveillance by OGG1 and NUDT1

Abstract

Oxidative damage in DNA is one of the primary sources of mutations in the cell. The activities of repair enzymes 8-oxoguanine DNA glycosylase (OGG1) and human MutT Homologue 1 (NUDT1 or MTH1), which work together to ameliorate this damage, are closely linked to mutagenesis, genotoxicity, cancer, and inflammation. Here we have undertaken the development of smallmolecule dual inhibitors of the two enzymes as tools to test the relationships between these pathways and disease. The compounds preserve key structural elements of known inhibitors of the two enzymes, and they were synthesized and assayed with recently developed luminescence assays of the enzymes. Further structural refinement of initial lead molecules yielded compound 5 (SU0383) with IC 50 (NUDT1) = 0.034 μM and IC 50 (OGG1) = 0.49 μM. The compound SU0383 displayed low toxicity in two human cell lines at 10 μM. Experiments confirm the ability of SU0383 to increase sensitivity of tumor cells to oxidative stress. Dual inhibitors of these two enzymes are expected to be useful in testing multiple hypotheses regarding the roles of 8-oxo-dG in multiple disease states.

OGG1 co-inhibition antagonizes the tumor-inhibitory effects of targeting MTH1

“…However, this difference in efflux ratio is modest, and as the cytotoxic effects do not change materially with longer treatment durations, another explanation is that the pronounced cytotoxicity at 20 μM SU0383 treatment is due to off-target effects. This is particularly likely as the reported IC50s of SU0383 for MTH1 (0.034 μM) and OGG1 (0.49 μM) as well as the prior reported cytotoxic dose (10 μM) [ 31 ] are below the 20 μM at which we see cytotoxicity in our experiments ( Fig. 5 C and D).…”

“…SU0268 [ 29 ] and SU0383 [ 31 ] were synthesized in Dr. Eric Kool's lab. Inhibitor working stock solutions were prepared in DMSO (Sigma, D2650).…”

“…Here, we investigate how OGG1 co-inhibition in cancer cell lines alters the well-characterized effects of MTH1 inhibition [ 4 ]. To this end, we utilized MTH1/OGG1 co-depletion via shRNA, co-treatment with OGG1 and MTH1 small molecule inhibitors as well as treatment with a novel OGG1/MTH1 dual inhibitor developed by members of our team [ 31 ]. Our results support that, rather than increasing cytotoxicity, OGG1 co-inhibition protects against the anti-tumor effects of targeting MTH1 by limiting the DNA strand breaks, p53 induction, and cellular senescence evoked by MTH1 inhibition.…”

Base excision repair and its implications to cancer therapy

“…Another inhibitor, SU0268, had a lower IC 50 (59 nM), good permeability and low cytotoxicity on normal cells where an increase in genomic 8-oxoG was demonstrated [ 25 ]. A dual inhibitor (SU0383) was subsequently developed that would also inhibit MutT human homolog-1 (MTH1; aka NUDT) whose major substrate is 8-oxoG nucleotides [ 26 ]. By inhibiting both enzymes that clear genomic 8-oxoG and oxidized bases from the nucleotide pool, the increased oxidation load would tip the cancer cells into apoptosis, in the same way as proposed by MTH1 inhibitor alone [ 27 , 28 ].…”

Nudix hydrolase 1 is a prognostic biomarker in hepatocellular carcinoma

“…Oxidative stress plays an important role in the pathogenesis of HBV-related chronic liver diseases including HCC [17]. NUDT1 sanitizes oxidized dNTP pools and prevents incorporation of damaged oxidized bases during DNA replication [8,18,19]. NUDT1 overexpression has been documented in several cancers [20][21][22][23], including renal-cell carcinomas [24], brain tumors [25,26], lung cancer [20,27], gastric cancer [28], and esophageal squamous cell carcinomas [29].…”