DCTPP1 prevents a mutator phenotype through the modulation of dCTP, dTTP and dUTP pools

Risk assessment model based on nucleotide metabolism-related genes highlights SLC27A2 as a potential therapeutic target in breast cancer

PURPOSE

Breast cancer (BC) is the most prevalent malignant tumor worldwide among women, with the highest incidence rate. The mechanisms underlying nucleotide metabolism on biological functions in BC remain incompletely elucidated. MATERIALS AND METHODS: We harnessed differentially expressed nucleotide metabolism-related genes from The Cancer Genome Atlas-BRCA, constructing a prognostic risk model through univariate Cox regression and LASSO regression analyses. A validation set and the GSE7390 dataset were used to validate the risk model. Clinical relevance, survival and prognosis, immune infiltration, functional enrichment, and drug sensitivity analyses were conducted.

RESULTS

Our findings identified four signature genes (DCTPP1, IFNG, SLC27A2, and MYH3) as nucleotide metabolism-related prognostic genes. Subsequently, patients were stratified into high- and low-risk groups, revealing the risk model's independence as a prognostic factor. Nomogram calibration underscored superior prediction accuracy. Gene Set Variation Analysis (GSVA) uncovered activated pathways in low-risk cohorts and mobilized pathways in high-risk cohorts. Distinctions in immune cells were noted between risk cohorts. Subsequent experiments validated that reducing SLC27A2 expression in BC cell lines or using the SLC27A2 inhibitor, Lipofermata, effectively inhibited tumor growth.

CONCLUSIONS

We pinpointed four nucleotide metabolism-related prognostic genes, demonstrating promising accuracy as a risk prediction tool for patients with BC. SLC27A2 appears to be a potential therapeutic target for BC among these genes.

Expression of human dCTP pyrophosphatase 1 (DCTPP1) and its association with cisplatin resistance characteristics in ovarian cancer

Cisplatin (DDP) resistance is a major challenge in treating ovarian cancer patients. A recently discovered enzyme called dCTP pyrophosphatase 1 (DCTPP1) has been implicated in regulating cancer characteristics, including drug responses. In this study, we aimed to understand the role of DCTPP1 in cancer progression and cisplatin response. Using publicly available databases, we analysed the expression and clinical significance of DCTPP1 in ovarian cancer. Our bioinformatics analysis confirmed that DCTPP1 is significantly overexpressed in ovarian cancer and is closely associated with tumour progression and poor prognosis after cisplatin treatment. We also found that DCTPP1 located in oxidoreductase complex and may be involved in various biological processes related to cisplatin resistance, including pyrimidine nucleotide metabolism, the P53 signalling pathway and cell cycle signalling pathways. We observed higher expression of DCTPP1 in cisplatin-resistant cells (SKOV3/DDP) and samples compared to their sensitive counterparts. Additionally, we found that DCTPP1 expression was only enhanced in SKOV3/S cells when treated with cisplatin, indicating different expression patterns of DCTPP1 in cisplatin-sensitive and cisplatin-resistant cancer cells. Our study further supports the notion that cisplatin induces intracellular reactive oxygen species (ROS) and triggers cancer cell death through excessive oxidative stress. Knocking out DCTPP1 reversed the drug resistance of ovarian cancer cells by enhancing the intracellular antioxidant stress response and accumulating ROS. Based on our research findings, we conclude that DCTPP1 has prognostic value for ovarian cancer patients, and targeting DCTPP1 may be clinically significant in overcoming cisplatin resistance in ovarian cancer.

DCTPP1, a reliable Q-biomarker for comprehensive evaluation of the quality of tripterygium glycoside tablets based on chemical references

BACKGROUND

As first-line clinical drugs, tripterygium glycoside tablets (TGTs) often have inconsistent efficacy and toxic side effects, mainly due to inadequate quality control. Therefore, clinically relevant quality standards for TGTs are urgently required.

PURPOSE

Based on chemical substances and considering pharmacological efficacy, we aimed to develop an effective quality evaluation method for TGTs.

METHODS

Representative commercial samples of TGTs were collected from different manufacturers, and qualitative UHPLC/LTQ-Orbitrap-MS and quantitative UHPLC-MS/MS analysis methods were successfully applied to evaluate their quality similarities and differences based on their chemical properties. Then the anti-immunity, anti-inflammatory and antitumor activities of TGTs and related monomers were evaluated using Jurkat, RAW264.7, MIA PaCa-2, and PANC-1 as cellular models. Subsequently, we predicted and verified small molecule-DCTPP1 interactions via molecular docking using the established DCTPP1 enzymatic activity assay. Finally, we performed a gray relational analysis to evaluate the chemical characteristics and biological effects of TGTs produced by different manufacturers.

RESULTS

We collected 24 batches of TGTs (D01-D24) from 5 manufacturers (Co. A, Co. B, Co. C, Co. D, Co. E) for quality evaluation. The chemical composition analysis revealed significant differences in the substance bases of the samples. The D02, D18-D20 samples from Co. B constituted a separate group that differed from other samples, mainly in their absence of diterpenoids and triterpenoids, including triptolide, triptophenolide, and triptonide. In vitro anti-immunity, antitumor and anti-inflammatory tests using the same TGT concentration revealed that, except for D02, D18-D20, the remaining 20 samples exhibited different degrees of anti-immunity, antitumor and anti-inflammatory activity. Our experiments verified that triptolide, triptophenolide, and triptonide were all DCTPP1 inhibitors, and that TGTs generally exhibited DCTPP1 enzyme inhibitory activity. Moreover, the inhibitory activity of D02, D18-D20 samples from Co. B was much lower than that of the other samples, with a nearly tenfold difference in IC50. Further comprehensive analysis revealed a high correlation between DCTPP1 enzyme inhibition activity and the anti-immunity and antitumor and anti-inflammatory activities of these samples.

CONCLUSION

The established DCTPP1 enzymatic activity assay proved suitable for quantitative pharmacological and pharmaceutical analysis to complement the existing quality control system for TGTs and to evaluate their effectiveness.

Sanitation enzymes: Exquisite surveillance of the noncanonical nucleotide pool to safeguard the genetic blueprint

Reactive oxygen species (ROS) are common products of normal cellular metabolism, but their elevated levels can result in nucleotide modifications. These modified or noncanonical nucleotides often integrate into nascent DNA during replication, causing lesions that trigger DNA repair mechanisms such as the mismatch repair machinery and base excision repair. Four superfamilies of sanitization enzymes can effectively hydrolyze noncanonical nucleotides from the precursor pool and eliminate their unintended incorporation into DNA. Notably, we focus on the representative MTH1 NUDIX hydrolase, whose enzymatic activity is ostensibly nonessential under normal physiological conditions. Yet, the sanitization attributes of MTH1 are more prevalent when ROS levels are abnormally high in cancer cells, rendering MTH1 an interesting target for developing anticancer treatments. We discuss multiple MTH1 inhibitory strategies that have emerged in recent years, and the potential of NUDIX hydrolases as plausible targets for the development of anticancer therapeutics.

Thymidine nucleotide metabolism controls human telomere length

Telomere length in humans is associated with lifespan and severe diseases, yet the genetic determinants of telomere length remain incompletely defined. Here we performed genome-wide CRISPR-Cas9 functional telomere length screening and identified thymidine (dT) nucleotide metabolism as a limiting factor in human telomere maintenance. Targeted genetic disruption using CRISPR-Cas9 revealed multiple telomere length control points across the thymidine nucleotide metabolism pathway: decreasing dT nucleotide salvage via deletion of the gene encoding nuclear thymidine kinase (TK1) or de novo production by knockout of the thymidylate synthase gene (TYMS) decreased telomere length, whereas inactivation of the deoxynucleoside triphosphohydrolase-encoding gene SAMHD1 lengthened telomeres. Remarkably, supplementation with dT alone drove robust telomere elongation by telomerase in cells, and thymidine triphosphate stimulated telomerase activity in a substrate-independent manner in vitro. In induced pluripotent stem cells derived from patients with genetic telomere biology disorders, dT supplementation or inhibition of SAMHD1 promoted telomere restoration. Our results demonstrate a critical role of thymidine metabolism in controlling human telomerase and telomere length, which may be therapeutically actionable in patients with fatal degenerative diseases.

The nucleotide metabolome of germinating Arabidopsis thaliana seeds reveals a central role for thymidine phosphorylation in chloroplast development

Thymidylates are generated by several partially overlapping metabolic pathways in different subcellular locations. This interconnectedness complicates an understanding of how thymidylates are formed in vivo. Analyzing a comprehensive collection of mutants and double mutants on the phenotypic and metabolic level, we report the effect of de novo thymidylate synthesis, salvage of thymidine, and conversion of cytidylates to thymidylates on thymidylate homeostasis during seed germination and seedling establishment in Arabidopsis (Arabidopsis thaliana). During germination, the salvage of thymidine in organelles contributes predominantly to the thymidylate pools and a mutant lacking organellar (mitochondrial and plastidic) thymidine kinase has severely altered deoxyribonucleotide levels, less chloroplast DNA, and chlorotic cotyledons. This phenotype is aggravated when mitochondrial thymidylate de novo synthesis is additionally compromised. We also discovered an organellar deoxyuridine-triphosphate pyrophosphatase and show that its main function is not thymidylate synthesis but probably the removal of noncanonical nucleotide triphosphates. Interestingly, cytosolic thymidylate synthesis can only compensate defective organellar thymidine salvage in seedlings but not during germination. This study provides a comprehensive insight into the nucleotide metabolome of germinating seeds and demonstrates the unique role of enzymes that seem redundant at first glance.

The consequences of viral infection on host DNA damage response: a focus on SARS-CoVs

DNA damage and genome instability in host cells are introduced by many viruses during their life cycles. Severe acute respiratory syndrome coronaviruses (SARS-CoVs) manipulation of DNA damage response (DDR) is an important area of research that is still understudied. Elucidation of the direct and indirect interactions between SARS-CoVs and DDR not only provides important insights into how the viruses exploit DDR pathways in host cells but also contributes to our understanding of their pathogenicity. Here, we present the known interactions of both SARS-CoV and SARS-CoV-2 with DDR pathways of the host cells, to further understand the consequences of infection on genome integrity. Since this area of research is in its early stages, we try to connect the unlinked dots to speculate and propose different consequences on DDR mechanisms. This review provides new research scopes that can be further investigated in vitro and in vivo, opening new avenues for the development of anti-SARS-CoV-2 drugs.

Transcriptomics and metabolomics analyses provide insights into the difference in toxicity of benzo[a]pyrene and 6-chlorobenzo[a]pyrene to human hepatic cells

The toxicological information of chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs), as derivatives of PAHs, is still relatively lacking. In this study, a combination of transcriptomics and metabolomics approach was adopted to explore the changes in toxicity to human L02 hepatocytes after chlorination of benzo[a]pyrene (B[a]P) at 6 position. In general, 6-Cl-B[a]P produced a stronger toxicity to human hepatic cells than did parent B[a]P. When exposure concentrations were 5 and 50 nM, 6-Cl-B[a]P caused a weaker transcriptomic perturbation relative to B[a]P, whereas a stronger metabolomic perturbation, a stronger oxidative stress and a stronger inhibition effect on cell viability were caused by 6-Cl-B[a]P than did parent B[a]P. Pathway enrichment analysis indicated that 6-Cl-B[a]P produced a more widely perturbation to metabolic pathways than did B[a]P. Although they both significantly impaired the function of mitochondrial electron transport chain (ETC), the exact mechanism is different. B[a]P suppressed the expression of 20 genes regulating mitochondrial ETC mainly via AhR activation. However, 6-Cl-B[a]P produced a stronger inhibition on the activities of complexes I and V than did B[a]P. Meanwhile, 6-Cl-B[a]P also exhibited a stronger inhibition effect on mitochondrial β oxidation of fatty acid. Furthermore, 6-Cl-B[a]P and B[a]P both significantly disturbed the nucleotide metabolism, glycerophospholipid metabolism and amino acid metabolism in L02 cells.

ROS-Induced DCTPP1 Upregulation Contributes to Cisplatin Resistance in Ovarian Cancer

Cisplatin resistance hinders the improvement of the prognosis of patients with ovarian cancer. Cisplatin induces cancer cell apoptosis by inducing reactive oxygen species (ROS). dCTP pyrophosphatase 1 (DCTPP1) is a newly discovered dNTP pyrophosphatase. This study aimed to identify the role of DCTPP1 in oxidative stress and cisplatin response of ovarian cancer. Our results indicates cisplatin-induced ROS generation was responsible for the upregulation of DCTPP1 in ovarian cancer cells, whereas DCTPP1 knockdown significantly enhanced the sensitivity of ovarian cancer cells to cisplatin, reflect in reactive oxygen species (ROS) generation, double-strand DNA breaks, and cell apoptosis. The expression of redox-related genes and the activation of the PI3/Akt signaling pathway were also inhibited by DCTPP1 knockdown. Our data proposes that the development of therapeutic approaches targeting DCTPP1 may be useful in the treatment of ovarian cancer.

Therapy Prospects for Mitochondrial DNA Maintenance Disorders

Mitochondrial DNA depletion and multiple deletions syndromes (MDDS) constitute a group of mitochondrial diseases defined by dysfunctional mitochondrial DNA (mtDNA) replication and maintenance. As is the case for many other mitochondrial diseases, the options for the treatment of these disorders are rather limited today. Some aggressive treatments such as liver transplantation or allogeneic stem cell transplantation are among the few available options for patients with some forms of MDDS. However, in recent years, significant advances in our knowledge of the biochemical pathomechanisms accounting for dysfunctional mtDNA replication have been achieved, which has opened new prospects for the treatment of these often fatal diseases. Current strategies under investigation to treat MDDS range from small molecule substrate enhancement approaches to more complex treatments, such as lentiviral or adenoassociated vector-mediated gene therapy. Some of these experimental therapies have already reached the clinical phase with very promising results, however, they are hampered by the fact that these are all rare disorders and so the patient recruitment potential for clinical trials is very limited.

DCTPP1, an Oncogene Regulated by miR-378a-3p, Promotes Proliferation of Breast Cancer via DNA Repair Signaling Pathway

Breast cancer (BRCA) is one of the most deadly cancers worldwide, with poor survival rates that could be due to its high proliferation. Human all-alpha dCTP pyrophosphatase 1 (DCTPP1) is implicated in numerous diseases, including cancers. However, its role in BRCA is unclear. In this study, we used bioinformatic analyses of the ONCOMINE, UALCAN, and GEPIA databases to determine the expression pattern of DCTPP1 in BRCA. We found that elevated DCTPP1 levels correlate with poor BRCA prognosis. DCTPP1 silencing inhibited BRCA cell proliferation and induced apoptosis in vitro, as well as in vivo. Our data show that this tumorigenic effect depends on DNA repair signaling. Moreover, we found that DCTPP1 is directly modulated by miR-378a-3p, whose downregulation is linked to BRCA progression. Our results showed down-regulation of miR-378a-3p in BRCA. Upregulation of miR-378a-3p, on the other hand, can inhibit BRCA cell growth and proliferation. This study shows that reduced miR-378a-3p level enhances DCTPP1 expression in BRCA, which promotes proliferation by activating DNA repair signaling in BRCA.