The high expression of MTH1 and NUDT5 promotes tumor metastasis and indicates a poor prognosis in patients with non-small-cell lung cancer

Exploring MTH1 inhibitory potential of Thymoquinone and Baicalin for therapeutic targeting of breast cancer

Cancers frequently have increased ROS levels due to disrupted redox balance, leading to oxidative DNA and protein damage, mutations, and apoptosis. The MTH1 protein plays a crucial role by sanitizing the oxidized dNTP pools. Hence, cancer cells rely on MTH1 to prevent the integration of oxidized dNTPs into DNA, preventing DNA damage and allowing cancer cell proliferation. We have discovered Thymoquinone (TQ) and Baicalin (BC) as inhibitors of MTH1 using combined docking and MD simulation approaches complemented by experimental validations via assessing binding affinity and enzyme inhibition. Docking and MD simulations studies revealed an efficient binding of TQ and BC to the active site pocket of the MTH1, and the resultant complexes are appreciably stable. Fluorescence measurements estimated a strong binding affinity of TQ and BC with Ka 3.4 ×106 and 1.0 ×105, respectively. Treating breast cancer cells with TQ and BC significantly inhibited the growth and proliferation (IC50 values 28.3 µM and 34.8 µM) and induced apoptosis. TQ and BC increased the ROS production in MCF7 cells, imposing substantial oxidative stress on cancer cells and leading to cell death. Finally, TQ and BC are proven strong MTH1 inhibitors, offering promising prospects for anti-cancer therapy.

The novel phosphatase NUDT5 is a critical regulator of triple-negative breast cancer growth

BACKGROUND

The most aggressive form of breast cancer is triple-negative breast cancer (TNBC), which lacks expression of the estrogen receptor (ER) and progesterone receptor (PR), and does not have overexpression of the human epidermal growth factor receptor 2 (HER2). Treatment options for women with TNBC tumors are limited, unlike those with ER-positive tumors that can be treated with hormone therapy, or those with HER2-positive tumors that can be treated with anti-HER2 therapy. Therefore, we have sought to identify novel targeted therapies for TNBC. In this study, we investigated the potential of a novel phosphatase, NUDT5, as a potential therapeutic target for TNBC.

METHODS

The mRNA expression levels of NUDT5 in breast cancers were investigated using TCGA and METABRIC (Curtis) datasets. NUDT5 ablation was achieved through siRNA targeting and NUDT5 inhibition with the small molecule inhibitor TH5427. Xenograft TNBC animal models were employed to assess the effect of NUDT5 inhibition on in vivo tumor growth. Proliferation, death, and DNA replication assays were conducted to investigate the cellular biological effects of NUDT5 loss or inhibition. The accumulation of 8-oxo-guanine (8-oxoG) and the induction of γH2AX after NUDT5 loss was determined by immunofluorescence staining. The impact of NUDT5 loss on replication fork was assessed by measuring DNA fiber length.

RESULTS

In this study, we demonstrated the significant role of an overexpressed phosphatase, NUDT5, in regulating oxidative DNA damage in TNBCs. Our findings indicate that loss of NUDT5 results in suppressed growth of TNBC both in vitro and in vivo. This growth inhibition is not attributed to cell death, but rather to the suppression of proliferation. The loss or inhibition of NUDT5 led to an increase in the oxidative DNA lesion 8-oxoG, and triggered the DNA damage response in the nucleus. The interference with DNA replication ultimately inhibited proliferation.

CONCLUSIONS

NUDT5 plays a crucial role in preventing oxidative DNA damage in TNBC cells. The loss or inhibition of NUDT5 significantly suppresses the growth of TNBCs. These biological and mechanistic studies provide the groundwork for future research and the potential development of NUDT5 inhibitors as a promising therapeutic approach for TNBC patients.

Targeting the nucleic acid oxidative damage repair enzyme MTH1: a promising therapeutic option

The accumulation of reactive oxygen species (ROS) plays a pivotal role in the development of various diseases, including cancer. Elevated ROS levels cause oxidative stress, resulting in detrimental effects on organisms and enabling tumors to develop adaptive responses. Targeting these enhanced oxidative stress protection mechanisms could offer therapeutic benefits with high specificity, as normal cells exhibit lower dependency on these pathways. MTH1 (mutT homolog 1), a homolog of Escherichia coli's MutT, is crucial in this context. It sanitizes the nucleotide pool, preventing incorporation of oxidized nucleotides, thus safeguarding DNA integrity. This study explores MTH1's potential as a therapeutic target, particularly in cancer treatment, providing insights into its structure, function, and role in disease progression.

8-oxo-dGTP curbs tumor development via S phase arrest and AIF-mediated apoptosis

Oxidative stress can attack precursor nucleotides, resulting in nucleic acid damage in cells. It remains unclear how 8-oxo-dGTP and 8-oxoGTP, oxidized forms of dGTP and GTP, respectively, could affect DNA or RNA oxidation levels and tumor development. To address this, we intravenously administered 8-oxo-dGTP and 8-oxoGTP to wild-type and MTH1-knockout mice. 8-oxoGTP administration increased frequency of tumor incidence, which is more prominent in MTH1-knockout mice. However, 8-oxo-dGTP treatment rather reduced tumor development regardless of the mouse genotype. The tumor suppressive effects of 8-oxo-dGTP were further confirmed using xenograft and C57/6J-Apc^Min/Nju mouse models. Mechanistically, 8-oxo-dGTP increased the 8-oxo-dG contents in DNA and DNA strand breakage, induced cell cycle arrest in S phase and apoptosis mediated by AIF, eventually leading to reduced tumor incidence. These results suggest distinct roles of 8-oxo-dGTP and 8-oxoGTP in tumor development.

Mitotic MTH1 Inhibitors in Treatment of Cancer

The DNA damage response (DDR) protein MTH1 is sanitising the oxidized dNTP pool and preventing incorporation of oxidative damage into DNA and has an emerging role in mitosis. It is a stress-induced protein and often found to be overexpressed in cancer. Mitotic MTH1 inhibitors arrest cells in mitosis and result in incorporation of oxidative damage into DNA and selective killing of cancer cells. Here, I discuss the leading mitotic MTH1 inhibitor TH1579 (OXC-101, karonudib), now being evaluated in clinical trials, and describe its dual effect on mitosis and incorporation of oxidative DNA damage in cancer cells. I describe why MTH1 inhibitors that solely inhibits the enzyme activity fail to kill cancer cells and discuss if MTH1 is a valid target for cancer treatment. I discuss emerging roles of MTH1 in regulating tubulin polymerisation and mitosis and the necessity of developing the basic science insights along with translational efforts. I also give a perspective on how edgetic perturbation is making target validation difficult in the DDR field.

A novel prognostic 7-methylguanosine signature reflects immune microenvironment and alternative splicing in glioma based on multi-omics analysis

Glioma is the most common type of central nervous system tumor with increasing incidence. 7-methylguanosine (m7G) is one of the diverse RNA modifications that is known to regulate RNA metabolism and its dysregulation was associated with various cancers. However, the expression pattern of m7G regulators and their roles in regulating tumor immune microenvironments (TIMEs) as well as alternative splicing events (ASEs) in glioma has not been reported. In this study, we showed that m7G regulators displayed a close correlation with each other and most of them were differentially expressed between normal and glioma tissues. Two m7G signatures were then constructed to predict the overall survival of both GBM and LGG patients with moderate predictive performance. The risk score calculated from the regression coefficient and expression level of signature genes was proved to be an independent prognostic factor for patients with LGG, thus, a nomogram was established on the risk score and other independent clinical parameters to predict the survival probability of LGG patients. We also investigated the correlation of m7G signatures with TIMEs in terms of immune scores, expression levels of HLA and immune checkpoint genes, immune cell composition, and immune-related functions. While exploring the correlation between signature genes and the ASEs in glioma, we found that EIF4E1B was a key regulator and might play dual roles depending on glioma grade. By incorporating spatial transcriptomic data, we found a cluster of cells featured by high expression of PTN exhibited the highest m7G score and may communicate with adjacent cancer cells via SPP1 and PTN signaling pathways. In conclusion, our work brought novel insights into the roles of m7G modification in TIMEs and ASEs in glioma, suggesting that evaluation of m7G in glioma could predict prognosis. Moreover, our data suggested that blocking SPP1 and PTN pathways might be a strategy for combating glioma.

Specific 8-oxo-dGTPase activity of MTH1 (NUDT1) protein as a quantitative marker and prognostic factor in human colorectal cancer

The MTH1 (NUDT1) gene, because it is frequently upregulated in many types of human cancers, has been considered a general marker of carcinogenesis for over two decades. The MTH1 protein hydrolyzes the oxidized mutagenic DNA precursor, 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP), to the corresponding 5'-monophosphate and inorganic pyrophosphate. This prevents its incorporation into DNA by DNA polymerases and protects cells from the accumulation of 8-oxo-dGTP-induced point mutations. Elevated MTH1 mRNA and protein in many types of human cancer indicate a worse prognosis. However, the enzymatic activity of MTH1 has remained largely uninvestigated in this context. Therefore, we have set out to determine the specific 8-oxo-dGTPase activity of MTH1 in 57 pairs of human colorectal cancers (CRC) and adjacent cancer-free tissues (CFCF). The goal was to ascertain the potential for measuring this enzymatic activity as a way to differentiate cancerous from non-cancerous specimens of the intestine, as well as defining its capabilities as a prognostic value for disease-free survival. We found that 79% of CRC tumors exhibited a higher MTH1 activity than did CFCF, with a significant 1.6-fold increase in overall median value (p < 1E-6). The 8-oxo-dGTPase in both tissues was proportional to the corresponding levels of MTH1 protein, as assayed by Western blotting. Activity higher than the ROC-optimized threshold (AUC = 0.71) indicated cancerous tissue, with a 54% sensitivity and an 83% specificity. Postoperative fate followed for up to 100 months showed that higher 8-oxo-dGTPase, in either the CFCF or the CRC tumor, clearly lowered the probability of a relapse-free survival, although borderline statistical significance (p < 0.05) was crossed only for the CFCF.