The intrinsic DNA damage repair response represents a major limiting factor for the therapeutic efficacy of many anticancer therapies such as chemodynamic therapy (CDT). Here, a degradable metal-small molecule drug coordination nanomedicine (siAPE1/Cu-MP@HA) is developed for DNA damage-augmented CDT treatment of lung cancers. The design is achieved by the coordination-driven self-assembly of Cu2+ and 6-mercaptopurine (6-MP) with the siAPE1 loading and hyaluronic acid (HA) modification. The siAPE1/Cu-MP@HA possesses the tumor targeting ability and is degradable in lysosomes for specific releases of Cu2+, siAPE1, and 6-MP because of the weak acidity/glutathione (GSH) dual-responsiveness. Upon the depletion of endogenous GSH, the siAPE1/Cu-MP@HA promotes the ∙OH generation from endogenous H2O2 via the Fenton-like reaction, significantly enhancing the CDT anticancer effect. It is evidenced that the siAPE1/Cu-MP@HA treatment effectively disrupts the DNA synthesis and inhibits the DNA damage repair, thereby augmenting the DNA damage. In vivo, experiments demonstrate the remarkable therapeutic efficacy against A549 lung cancer in mice with negligible systemic toxicity after intravenous administration of the siAPE1/Cu-MP@HA. This study offers an innovative approach targeting the DNA damage repair system for enhancing CDT effects in cancer treatment.

This study focuses on identifying DNA sequences capable of selectively binding 6-mercaptopurine (6MP) or its analog, azathioprine (Aza), as a potential bioreceptor for biosensing methods. The approach used in the study is based on instrumental analysis methods such as UV-Vis spectroscopy, high performance liquid chromatography (HPLC), and nuclear magnetic resonance techniques to describe the interaction, its mode, and strength as well as selectivity of selected DNA sequences toward thiopurines. Thus, of the sequences tested, dsDNA GGCAGGACGGAG poses the ability to form complexes with 6MP, with an affinity constant of 2.52·103 M-1 as determined by DOSY NMR. Studies performed by HPLC technique confirmed the selectivity of the indicated strand toward selected interferents like natural metabolites and active pharmaceutical ingredients (API) used during azathioprine treatment. Further insights into the DNA-6MP interaction were provided by TOCSY and NOESY NMR experiments, highlighting the preference for guanine-rich sequences in binding, indicating a potential 6MP binding site in the dsDNA. The results also indicate the rapid conversion of azathioprine to 6-mercaptopurine upon contact with DNA, indirectly confirming the pro-drug nature of azathioprine. This research contributes to the development of DNA-based bioreceptors for selective determination of 6-mercaptopurine, with potential implications in personalized medicine and therapeutic drug monitoring.

Thiopurines are a class of immunosuppressant and antineoplastic agents. They are widely used in the treatment of inflammatory bowel disease, haematological malignancies and autoimmune diseases, but can cause significant toxicity. Inherited gene mutations are now recognized as independent risk factors for severe adverse drug reactions to thiopurines even at 10-fold dose reductions. We present a case of thiopurine toxicity resulting in severe myelosuppression, hepatotoxicity and alopecia in an individual with homozygous *3/*3 loss-of-function alleles in the NUDT15 gene. Our case highlights important differences in gene mutation frequencies between races that can help guide pharmacogenomic testing.

Activating autophagy may be therapeutically beneficial, and we have previously shown that azathioprine (AZA), an immunomodulatory drug, induces autophagy. Here, we evaluated the induction of autophagy by the thiopurines AZA, mercaptopurine (6-MP) and thioguanine (6-TG) in THP-1 macrophages and investigated the mechanism of action in the context of this cellular process. The cytotoxicity of thiopurines was evaluated using an LDH assay. Induction of endogenous LC3 by thiopurines was evaluated using immunostaining. To confirm autophagy activation by thiopurines, a GFP-RFP-LC3 reporter plasmid was used to monitor the maturation of autophagosomes to autolysosomes. Induction of apoptosis by thiopurines was evaluated using Annexin V/PI staining, and ER stress was assessed via RT‒PCR analysis of XBP1 splicing. To gain insight into the mechanism of action of thiopurines, mTORC1 activity and eIF2α-S51 phosphorylation were evaluated by immunoblotting. Thiopurines were not cytotoxic to cells and induced strong time- and concentration-dependent autophagy. Thiopurines activate autophagy with complete progression through the pathway. Induction of autophagy by thiopurines occurred independently of apoptosis and ER stress. Immunoblotting revealed that AZA inhibited mTORC1 activity, and AZA and 6-TG increased eIF2α-S51 phosphorylation. In contrast, 6-MP had a minor effect on either signalling pathway. Thiopurines are strong inducers of autophagy, and autophagy induction should be considered among the mechanisms responsible for patient response to thiopurines.

Nudix hydrolase 15 (NUDT15) deficiency is strongly associated with thiopurine-induced myelosuppression. Currently, testing for NUDT15 deficiency is based on the genotyping of the most frequent and clinically characterized no-function variants, that is, *2, *3 and *9. The Hispanic/Latino-predominant variant NUDT15 *4 (p.R139H) is classified as "uncertain function" by the Clinical Pharmacogenetics Implementation Consortium, because of insufficient data to ascertain its clinical actionability. In this study, we evaluated the association of NUDT15 *4 with mercaptopurine (6-MP) tolerance in a retrospective cohort of 1,399 patients with acute lymphoblastic leukemia (ALL) of diverse ancestries. All patients were wildtype for thiopurine methyltransferase gene. Patients were treated with 6-MP in the context of ALL frontline clinical trials. The tolerated dose of 6-MP was used to assess drug toxicity during the maintenance phase of ALL therapy. Patients with NUDT15 *1/*4 (n = 16, all of whom self-identified as Hispanic/Latino) tolerated a significantly lower dose of 6-MP than did those with NUDT15 *1/*1: median [interquartile range] of 39.0 [21.2-52.8] mg/m2, vs. 62.2 [47.9-71.6] mg/m2, P value < 0.001. No patient homozygous for *4 was detected. In a separate retrospective validation study, six patients were identified as having NUDT15 *1/*4 by routine clinical pharmacogenetics testing and tolerated a 6-MP median dose of 38.7 mg/m2 (IQR, 33.7-54.0), confirming the need for dose reduction attributed to the NUDT15 *4 variant. These results point to the need to include NUDT15 *4 in pharmacogenetics-guided thiopurine dosing algorithms.

Most cancers upregulate the telomere lengthening enzyme telomerase to achieve unlimited cell division. How chemotherapeutic nucleoside 6-thio-2'-deoxyguanosine (6-thio-dG) targets telomerase to inhibit telomere maintenance in cancer cells and tumors was unclear. Here, we demonstrate that telomerase insertion of 6-thio-dGTP prevents synthesis of additional telomeric repeats but does not disrupt telomerase binding to telomeres. Specifically, 6-thio-dG inhibits telomere extension after telomerase translocates along its product DNA to reposition the template, inducing a non-productive complex rather than enzyme dissociation. Furthermore, we provide direct evidence that 6-thio-dG treatment inhibits telomere synthesis by telomerase in cancer cells. In agreement, telomerase-expressing cancer cells harboring critically short telomeres are more sensitive to 6-thio-dG and show a greater induction of telomere losses compared to cancer cells with long telomere reserves. Our studies reveal that telomere length and telomerase status determine 6-thio-dG sensitivity and uncover the molecular mechanism by which 6-thio-dG selectively inhibits telomerase synthesis of telomeric DNA.

Photodynamic therapy (PDT) is a medical treatment that kills target cells through reactive oxygen species (ROS) generated by photosensitizers (PS) and surrounding oxygen under the stimulus of light. Despite of its popularity in cancer treatment, PDT relys on oxygen and therefore suffers from long response time and low efficiency under low-oxygen situations such as tumor hypoxia. Herein, to improve the usage of oxygen and increase ROS yield, we synthesized six potential PSs termed DC-O, DC-S, DC-BrO, DC-BrS, DC-IO, and DC-IS, by modifying coumarins with thiocarbonyl and bromine/iodine. We found that the thiocarbonyl group induces a significant bathochromic shift of the absorption spectra. In addition, the ROS production was significantly improved, likely because these PSs can simultaneously generate singlet oxygen (1O2) and superoxide anions (O2•-) through different pathways. Among these compounds, DC-BrS produces largest amount of ROS and exhibits strongest cytotoxicity towards cells, the survival rate of B16-F10 cells incubated with DC-BrS was only 20.7 % after irradiation at 460 nm for 10 min, indicating DC-BrS as a strong candidate for photodynamic therapy. Most importantly, this work provides an important direction for the design of PSs in the future.

β-secretase (BACE1) is instrumental in amyloid-β (Aβ) production, with overexpression noted in Alzheimer's disease (AD) neuropathology. The interaction of Aβ with the receptor for advanced glycation endproducts (RAGE) facilitates cerebral uptake of Aβ and exacerbates its neurotoxicity and neuroinflammation, further augmenting BACE1 expression. Given the limitations of previous BACE1 inhibition efforts, the study explores reducing BACE1 expression to mitigate AD pathology. The research reveals that the anticancer agent 6-thioguanosine (6-TG) markedly diminishes BACE1 expression without eliciting cytotoxicity while enhancing microglial phagocytic activity, and ameliorate cognitive impairments with reducing Aβ accumulation in AD mice. Leveraging advanced deep learning-based tool for target identification, and corroborating with surface plasmon resonance assays, it is elucidated that 6-TG directly interacts with RAGE, modulating BACE1 expression through the JAK2-STAT1 pathway and elevating soluble RAGE (sRAGE) levels in the brain. The findings illuminate the therapeutic potential of 6-TG in ameliorating AD manifestations and advocate for small molecule strategies to increase brain sRAGE levels, offering a strategic alternative to the challenges posed by the complexity of AD.

Linking sequence variation to phenotypic effects is critical for efficient exploitation of large genomic datasets. Here we present a novel approach combining directed evolution with protein language modeling to characterize naturally-evolved variants of a rice immune receptor. Using high-throughput directed evolution, we engineered the rice immune receptor Pik-1 to bind and recognize the fungal proteins Avr-PikC and Avr-PikF, which evade detection by currently characterized Pik-1 alleles. A protein language model was fine-tuned on this data to correlate sequence variation with ligand binding behavior. This modeling was then used to characterize Pik-1 variants found in the 3,000 Rice Genomes Project dataset. Two variants scored highly for binding against Avr-PikC, and in vitro analyses confirmed their improved ligand binding over the wild-type Pik-1 receptor. Overall, this machine learning approach identified promising sources of disease resistance in rice and shows potential utility for exploring the phenotypic variation of other proteins of interest.

Photosensitizers with near-infrared (NIR) excitation, especially above 800 nm which is highly desired for phototherapy, remain rare due to the fast nonradiative relaxation process induced by exciton-vibration coupling. Here, a diketopyrrolopyrrole-derived photosensitizer (DTPA-S) is developed via thionation of carbonyl groups within the diketopyrrolopyrrole skeleton, which results in a large bathochromic shift of 81 nm, endowing the photosensitizer with strong NIR absorption at 712 nm. DTPA-S is then introduced with a functional biomolecule (N3-PEG2000-RGD) via click reaction for the construction of integrin αvβ3 receptor-targeted nano-micelles (NanoDTPA-S/RGD), which endows the photosensitizer with a further superlarge absorption redshift of 138 nm, thus extending the absorption maxima to ≈850 nm. Remarkably, thiocarbonyl substitution increases the nonbonding characters in frontier molecular orbitals, which can effectively suppress the nonradiative vibrational relaxation process via reducing the reorganization energy, enabling efficient reactive oxygen species (ROS) generation under 880 nm excitation. Screened by in vitro and in vivo assays, NanoDTPA-S/RGD with high water solubility, excellent tumor-targeting ability, and photodynamic/photothermal therapy synergistic effect exhibits satisfactory phototherapeutic performance. Overall, this study demonstrates a new design of efficient NIR-triggered diketopyrrolopyrrole photosensitizer with facile installation of functional biomolecules for potential clinical applications.

RNA-binding proteins (RBPs) are attractive targets in human pathologies. Despite a number of efforts to target RBPs with small molecules, it is still difficult to develop RBP inhibitors, asking for a deeper understanding of how to chemically perturb RNA-binding activity. In this study, we found that the thiopurine drugs (6-mercaptopurine and 6-thioguanine) effectively disrupt CELF1-RNA interaction. The disrupting activity relies on the formation of disulfide bonds between the thiopurine drugs and CELF1. Mutating the cysteine residue proximal to the RNA recognition motifs (RRMs), or adding reducing agents, abolishes the disrupting activity. Furthermore, the 1,2,4-triazole-3-thione, a thiopurine analogue, was identified with 20-fold higher disrupting activity. Based on this analogue, we found that compound 9 disrupts CELF1-RNA interaction in living cells and ameliorates CELF1-mediated myogenesis deficiency. In summary, we identified a thiol-mediated binding mechanism for thiopurine drugs and their derivatives to perturb protein-RNA interaction, which provides novel insight for developing RBP inhibitors. Additionally, this work may benefit the pharmacological and toxicity research of thiopurine drugs.

Upregulation of MYC is a hallmark of cancer, wherein MYC drives oncogenic gene expression and elevates total RNA synthesis across cancer cell transcriptomes. Although this transcriptional anabolism fuels cancer growth and survival, the consequences and metabolic stresses induced by excess cellular RNA are poorly understood. Herein, we discover that RNA degradation and downstream ribonucleotide catabolism is a novel mechanism of MYC-induced cancer cell death. Combining genetics and metabolomics, we find that MYC increases RNA decay through the cytoplasmic exosome, resulting in the accumulation of cytotoxic RNA catabolites and reactive oxygen species. Notably, tumor-derived exosome mutations abrogate MYC-induced cell death, suggesting excess RNA decay may be toxic to human cancers. In agreement, purine salvage acts as a compensatory pathway that mitigates MYC-induced ribonucleotide catabolism, and inhibitors of purine salvage impair MYC+ tumor progression. Together, these data suggest that MYC-induced RNA decay is an oncogenic stress that can be exploited therapeutically. Significance: MYC is the most common oncogenic driver of poor-prognosis cancers but has been recalcitrant to therapeutic inhibition. We discovered a new vulnerability in MYC+ cancer where MYC induces cell death through excess RNA decay. Therapeutics that exacerbate downstream ribonucleotide catabolism provide a therapeutically tractable approach to TNBC (Triple-negative Breast Cancer) and other MYC-driven cancers.

Thioguanine (TG), azathioprine (AZA), and mercaptopurine (MP) are thiopurine prodrugs commonly used to treat diseases, such as leukemia and inflammatory bowel disease (IBD). 6-thioguanine nucleotides (6-TGNs) have been commonly used for monitoring treatment. High levels of 6-TGNs in red blood cells (RBCs) have been associated with leukopenia, the cutoff levels that predict this side effect remain uncertain. Thiopurines are metabolized and incorporated into leukocyte DNA. Measuring levels of DNA-incorporated thioguanine (DNA-TG) may be a more suitable method for predicting clinical response and toxicities such as leukopenia. Unfortunately, most methodologies to assay 6-TGNs are unable to identify the impact of NUDT15 variants, effecting mostly ethnic populations (e.g., Chinese, Indian, Malay, Japanese, and Hispanics). DNA-TG tackles this problem by directly measuring thioguanine in the DNA, which can be influenced by both TPMT and NUDT15 variants. While RBC 6-TGN concentrations have traditionally been used to optimize thiopurine therapy due to their ease and affordability of measurement, recent developments in liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques have made measuring DNA-TG concentrations in lymphocytes accurate, reproducible, and affordable. The objective of this systematic review was to assess the current evidence of DNA-TG levels as marker for thiopurine therapy, especially with regards to NUDT15 variants.

A systematic review and meta-analysis were performed on the current evidence for DNA-TG as a marker for monitoring thiopurine therapy, including methods for measurement and the illustrative relationship between DNA-TG and various gene variants (such as TPMT, NUDT15, ITPA, NT5C2, and MRP4). PubMed and Embase were systematically searched up to April 2024 for published studies, using the keyword "DNA-TG" with MeSH terms and synonyms. The electronic search strategy was augmented by a manual examination of references cited in articles, recent reviews, editorials, and meta-analyses. A meta-analysis was performed using R studio 4.1.3. to investigate the difference between the coefficients (Fisher's z-transformed correlation coefficient) of DNA-TG and 6-TGNs levels. A meta-analysis was performed using RevMan version 5.4 to investigate the difference in DNA-TG levels between patients with or without leukopenia using randomized effect size model. The risk of bias was assessed using the Newcastle-Ottowa quality assessment scale.

In this systematic review, 21 studies were included that measured DNA-TG levels in white blood cells for either patients with ALL (n = 16) or IBD (n = 5). In our meta-analysis, the overall mean difference between patients with leukopenia (ALL + IBD) versus no leukopenia was 134.15 fmol TG/µg DNA [95% confidence interval (CI) (83.78-184.35), P < 0.00001; heterogeneity chi squared of 5.62, I2 of 47%]. There was a significant difference in DNA-TG levels for patients with IBD with and without leukopenia [161.76 fmol TG/µg DNA; 95% CI (126.23-197.29), P < 0.00001; heterogeneity chi squared of 0.20, I2 of 0%]. No significant difference was found in DNA-TG level between patients with ALL with or without leukopenia (57.71 fmol TG/µg DNA [95% CI (- 22.93 to 138.35), P < 0.80]). DNA-TG monitoring was found to be a promising method for predicting relapse rates in patients with ALL, and DNA-TG levels are likely a better predictor for leukopenia in patients with IBD than RBC 6-TGNs levels. DNA-TG levels have been shown to correlate with various gene variants (TPMT, NUDT15, ITPA, and MRP4) in various studies, points to its potential as a more informative marker for guiding thiopurine therapy across diverse genetic backgrounds.

This systematic review strongly supports the further investigation of DNA-TG as a marker for monitoring thiopurine therapy. Its correlation with treatment outcomes, such as relapse-free survival in ALL and the risk of leukopenia in IBD, underscores its role in enhancing personalized treatment approaches. DNA-TG effectively identifies NUDT15 variants and predicts late leukopenia in patients with IBD, regardless of their NUDT15 variant status. The recommended threshold for late leukopenia prediction in patients with IBD with DNA-TG is suggested to be between 320 and 340 fmol/µg DNA. More clinical research on DNA-TG implementation is mandatory to improve patient care and to improve inclusivity in thiopurine treatment.

Thiopurines such as mercaptopurine (MP) are widely used to treat acute lymphoblastic leukemia (ALL). Thiopurine-S-methyltransferase (TPMT) and Nudix hydrolase 15 (NUDT15) inactivate thiopurines, and no-function variants are associated with drug-induced myelosuppression. Dose adjustment of MP is strongly recommended in patients with intermediate or complete loss of activity of TPMT and NUDT15. However, the extent of dosage reduction recommended for patients with intermediate activity in both enzymes is currently not clear.

MP dosages during maintenance were collected from 1768 patients with ALL in Singapore, Guatemala, India, and North America. Patients were genotyped for TPMT and NUDT15, and actionable variants defined by the Clinical Pharmacogenetics Implementation Consortium were used to classify patients as TPMT and NUDT15 normal metabolizers (TPMT/NUDT15 NM), TPMT or NUDT15 intermediate metabolizers (TPMT IM or NUDT15 IM), or TPMT and NUDT15 compound intermediate metabolizers (TPMT/NUDT15 IM/IM). In parallel, we evaluated MP toxicity, metabolism, and dose adjustment using a Tpmt/Nudt15 combined heterozygous mouse model (Tpmt+/-/Nudt15+/-).

Twenty-two patients (1.2%) were TPMT/NUDT15 IM/IM in the cohort, with the majority self-reported as Hispanics (68.2%, 15/22). TPMT/NUDT15 IM/IM patients tolerated a median daily MP dose of 25.7 mg/m2 (interquartile range = 19.0-31.1 mg/m2), significantly lower than TPMT IM and NUDT15 IM dosage (P < .001). Similarly, Tpmt+/-/Nudt15+/- mice displayed excessive hematopoietic toxicity and accumulated more metabolite (DNA-TG) than wild-type or single heterozygous mice, which was effectively mitigated by a genotype-guided dose titration of MP.

We recommend more substantial dose reductions to individualize MP therapy and mitigate toxicity in TPMT/NUDT15 IM/IM patients.

In photodynamic therapy (PDT) treatment, heavy-atom-free photosensitizers (PSs) are a great source of singlet oxygen photosensitizer. Reactive oxygen species (ROS) are produced by an energy transfer from the lowest energy triplet excited state to the molecular oxygen of cancer cells. To clarify the photophysical characteristics in the excited states of a few experimentally identified thionated (>C=S) molecules and their oxygenated congeners (>C=O), a quantum chemical study is conducted. This study illustrates the properties of the excited states in oxygen congeners that render them unsuitable for PDT treatment. Concurrently, a hierarchy is presented based on the utility of the lowest-energy triplet excitons of thionated compounds. Their non-radiative decay rates are calculated for reverse-ISC and inter-system crossover (ISC) processes. In addition, the vibronic importance of C=O and C=S bonds is clarified by the computation of the Huang-Rhys factor, effective vibrational mode, and reorganization energy inside the Marcus-Levich-Jörtner system. ROS generation in thionated PSs exceeds their oxygen congeners as kf ≪ kISC, where radiative decay rate is designated as kf. As a result, the current work offers a calculated strategy for analyzing the effectiveness of thionated photosensitizers in PDT.

Genome instability is a hallmark of cancer and are driven by mutations in oncogenes and tumor suppressor genes. Despite successes seen with select targeted therapeutics, this type of personalized medicine is only beneficial for a small subpopulation of cancer patients who have one of a few actionable genetic changes. Most tumors also contain hundreds of passenger mutations that offered no fitness advantage or disadvantage during tumor evolution. Mutations in known pharmacogenetic (PGx) loci for which germline variants encode variability in drug response can cause somatically acquired drug sensitivity. The NUDT15 gene is a known PGx locus that participates in the rate-limiting metabolism of thiopurines. People with two defective germline alleles of NUDT15 are hypersensitive to the toxic effects of thiopurines. NUDT15 is located adjacent to the Retinoblastoma ( RB1 ) tumor suppressor gene, which often undergoes homozygous deletion in retinoblastomas and other epithelial cancers. We observed that RB1 undergoes homozygous deletions in 9.4% of prostate adenocarcinomas and 2.5% of ovarian cancers, and in nearly all of these cases NUDT15 is also lost. Moreover, 44% of prostate adenocarcinomas and over 60% of ovarian cancers have lost one allele of NUDT15, which predicts that a majority of all prostate and ovarian cancers have somatically acquired hypersensitivity to thiopurine treatment. We performed a retrospective analysis of >16,000 patients in the US Veterans Administration health care system and found concurrent xanthine oxidase inhibition (XOi) and thiopurine usage for non-cancer indications is significantly associated with reduced incidence of prostate cancer. The hazard ratio for the development of prostate cancer in patients treated with thiopurines and XOi was 0.562 (0.301-1.051) for the unmatched cohort and 0.389 (0.185-0.819) for the propensity score matched cohort. We experimentally depleted NUDT15 from ovarian and prostate cancer cell lines and observed a dramatic sensitization to thiopurine-induced and DNA damage-dependent toxicity. These results indicate that somatic loss of NUDT15 predicts therapeutic sensitivity to a low cost and well tolerated drug with a broad therapeutic window.

Lifelong immunosuppression, cytotoxic effects of some immunosuppressive drugs, and opportunistic oncogenic viruses increase malignancy risks in solid organ recipients. The risk of myeloid neoplasms including chronic myeloid leukemia (CML) is also increased in this patient population. Tyrosine kinase inhibitors (TKIs), the key element of CML therapy, should be used cautiously in transplantation patients as they may interact with calcineurin inhibitors. With this report, a 63-year-old female kidney transplant recipient who developed CML 9 years after kidney transplantation is presented. CML in this patient was treated with a slightly reduced dose of imatinib (300 mg) due to concerns of adverse events including its interaction with tacrolimus. Deep molecular response (DMR) was achieved at 12 months under imatinib treatment. The patient is still in DMR after 30 months of follow-up, and she did not experience any adverse events or acute rejection episodes. CML and the use of TKIs in kidney transplant patients have been discussed with an extensive literature review. In this patient population, TKIs are generally well tolerated with achievement of treatment responses and good prognosis. Graft functions are also well maintained as long as drug interactions are monitored.

Intrahepatic cholestasis of pregnancy is an intrahepatic etiology of acute cholestasis commonly defined by pruritus and increased bile acids, liver transaminases, and, occasionally, bilirubin. Azathioprine is an immunosuppressive agent associated with various forms of hepatoxicity, ranging from transient rises in serum aminotransferase levels, acute cholestatic injury, and chronic hepatic injury. In this report, we present a 20-year-old pregnant woman who presented with cholestatic liver injury due to intrahepatic cholestasis of pregnancy with a clinical picture complicated by increased levels of azathioprine metabolites.

The excited state properties of thionated 5-fluorouridine (2',3',5'-tri-O-acetyl-5-fluoro-4-thiouridine; ta5F4TUrd), synthesized with Lawesson's reagent, have been intensively investigated with nanosecond transient absorption spectroscopy, time-resolved thermal lensing, near-infrared emission, and quantum chemical calculation. The intrinsic triplet lifetime of ta5F4TUrd was determined to be4.2 ± 0.7 μs in acetonitrile, and the formation quantum yield of the excited triplet state was as large as0.79 ± 0.01 . The quenching rate constants of the triplet ta5F4TUrd by the dissolved oxygen molecule and by the self-quenching process were found to be nearly equal to the diffusion-controlled rate of acetonitrile. The quantum yield of the singlet molecular oxygen produced through energy transfer between the triplet ta5F4TUrd and the dissolved oxygen,Φ Δ , was successfully determined to be0.61 ± 0.02 under the oxygen-saturated condition. From the oxygen concentration dependence of theΦ Δ value, the fraction of triplet ta5F4TUrd quenched by dissolved oxygen which gives rise to the 1 O2 * formation,S Δ , was successfully obtained to be0.78 ± 0.01 , which was the largest among the thionucleobases and the thionucleosides reported so far. This could be due to the lower energy and/or the ππ* character of the triplet state.

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract that encompasses two major conditions: Crohn's disease (CD) and ulcerative colitis (UC). Historically, IBD has been primarily reported in western countries, but over the past decades, its prevalence is rapidly increasing, especially in lower and middle-income countries (LMICs) such as India and China and also in Sub-Saharan Africa. The prevalence of IBD in LMICs has been the subject of growing concern due to the impact of access to public healthcare and the burden it places on healthcare resources. The classical thiopurines face significant challenges due to cessation of therapy in approximately half of patients within one year due to side effects or ineffectiveness. In this article, we highlight innovating thiopurine treatment for IBD patients in downregulating side effects and improving efficacy.

The use of azathioprine (AZA) in human medicine dates back to research conducted in 1975 that led to the development of several drugs, including 6-mercaptopurine. In 1958, it was shown that 6-mercaptopurine decreased the production of antibodies against earlier administered antigens, raising the hypothesis of an immunomodulatory effect. AZA is a prodrug that belongs to the thiopurine group of drugs that behave as purine analogs. After absorption, it is converted into 6-mercaptopurine. Subsequently, it can be degraded through various enzymatic pathways into inactive compounds and biologically active compounds related to the mechanism of action, which has been the subject of study to evaluate a possible antiviral effect. This study aims to examine the metabolism, mechanism of action, and antiviral potential of AZA and its derivatives, exploring AZA impact on antiviral targets and adverse effects through a narrative literature review. Ultimately, the review will provide insights into the antiviral mechanism, present evidence of its in vitro effectiveness against various DNA and RNA viruses, and suggest in vivo studies to further demonstrate its antiviral effects.

Mouse tumour models are extensively used as a pre-clinical research tool in the field of oncology, playing an important role in anticancer drugs discovery. Accordingly, in cancer genomics research, the demand for next-generation sequencing (NGS) is increasing, and consequently, the need for data analysis pipelines is likewise growing. Most NGS data analysis solutions to date do not support mouse data or require highly specific configuration for their use. Here, we present a genome analysis pipeline for mouse tumour NGS data including the whole-genome sequence (WGS) data analysis flow for somatic variant discovery, and the RNA-seq data flow for differential expression, functional analysis and neoantigen prediction. The pipeline is based on standards and best practices and integrates mouse genome references and annotations. In a recent study, the pipeline was applied to demonstrate the efficacy of low dose 6-thioguanine (6TG) treatment on low-mutation melanoma in a pre-clinical mouse model. Here, we further this study and describe in detail the pipeline and the results obtained in terms of tumour mutational burden (TMB) and number of predicted neoantigens, and correlate these with 6TG effects on tumour volume. Our pipeline was expanded to include a neoantigen analysis, resulting in neopeptide prediction and MHC class I antigen presentation evaluation. We observed that the number of predicted neoepitopes were more accurate indicators of tumour immune control than TMB. In conclusion, this study demonstrates the usability of the proposed pipeline, and suggests it could be an essential robust genome analysis platform for future mouse genomic analysis.

Sulfanylbenzamide thioesters are molecules with anti-HIV activity that disrupt zinc coordination in the viral protein NCp7. These molecules are useful as topical microbicides; however, they are too unstable to be used systemically. In this article, a nitroimidazole prodrug was used to protect the sulfanylbenzamide to convey blood stability and oral bioavailability to the molecule. Studies on the molecule called nipamovir were performed to assess the rate of prodrug cleavage, antiviral activity, mechanism of metabolism, and in vivo pharmacokinetics in several different species. An efficient and inexpensive synthesis of nipamovir is also described. The results indicate that nipamovir could be further developed as a new type of drug to treat HIV infection.

Numerous purine-containing compounds have undergone extensive investigation for their medical efficacy across various diseases. The swift progress in purine-based medicinal chemistry has brought to light the therapeutic capabilities of purine-derived compounds in addressing challenging medical conditions. Defined by a heterocyclic ring comprising a pyrimidine ring linked with an imidazole ring, purine exhibits a diverse array of therapeutic attributes. This review systematically addresses the multifaceted potential of purine derivatives in combating various diseases, including their roles as anticancer agents, antiviral compounds (anti-herpes, anti-HIV, and anti-influenzae), autoimmune and anti-inflammatory agents, antihyperuricemic and anti-gout solutions, antimicrobial agents, antitubercular compounds, anti-leishmanial agents, and anticonvulsants. Emphasis is placed on the remarkable progress made in developing purine-based compounds, elucidating their significant target sites. The article provides a comprehensive exploration of developments in both natural and synthetic purines, offering insights into their role in managing a diverse range of illnesses. Additionally, the discussion delves into the structure-activity relationships and biological activities of the most promising purine molecules. The intriguing capabilities revealed by these purine-based scaffolds unequivocally position them at the forefront of drug candidate development. As such, this review holds potential significance for researchers actively involved in synthesizing purine-based drug candidates, providing a roadmap for the continued advancement of this promising field.

Leukemia is a group of malignant disorders which affect the blood and blood-forming tissues in the bone marrow, lymphatic system, and spleen. Many types of leukemia exist; thus, their diagnosis and treatment are somewhat complicated. The use of conventional strategies for treatment such as chemotherapy and radiotherapy may develop many side effects and toxicity. Hence, modern research is concerned with the development of specific nano-formulations for targeted delivery of anti-leukemic drugs avoiding toxic effects on normal cells. Nanostructures can be applied not only in treatment but also in diagnosis. In this article, types of leukemia, its causes, diagnosis as well as conventional treatment of leukemia shall be reviewed. Then, the use of nanoparticles in diagnosis of leukemia and synthesis of nanocarriers for efficient delivery of anti-leukemia drugs being investigated in in vivo and clinical studies. Therefore, it may contribute to the discovery of novel and emerging nanoparticles for targeted treatment of leukemia with less side effects and toxicities.

Malignant peripheral nerve sheath tumors (MPNST) are highly aggressive soft-tissue sarcomas that arise from neural tissues and carry a poor prognosis. Previously, we found that the glutamine amidotransferase inhibitor JHU395 partially impeded tumor growth in preclinical models of MPNST. JHU395 inhibits de novo purine synthesis in human MPNST cells and murine tumors with partial decreases in purine monophosphates. On the basis of prior studies showing enhanced efficacy when glutamine amidotransferase inhibition was combined with the antimetabolite 6-mercaptopurine (6-MP), we hypothesized that such a combination would be efficacious in MPNST. Given the known toxicity associated with 6-MP, we set out to develop a more efficient and well-tolerated drug that targets the purine salvage pathway. Here, we report the discovery of Pro-905, a phosphoramidate protide that delivered the active nucleotide antimetabolite thioguanosine monophosphate (TGMP) to tumors over 2.5 times better than equimolar 6-MP. Pro-905 effectively prevented the incorporation of purine salvage substrates into nucleic acids and inhibited colony formation of human MPNST cells in a dose-dependent manner. In addition, Pro-905 inhibited MPNST growth and was well-tolerated in both human patient-derived xenograft (PDX) and murine flank MPNST models. When combined with JHU395, Pro-905 enhanced the colony formation inhibitory potency of JHU395 in human MPNST cells and augmented the antitumor efficacy of JHU395 in mice. In summary, the dual inhibition of the de novo and purine salvage pathways in preclinical models may safely be used to enhance therapeutic efficacy against MPNST.

Thiopurine S-methyltransferase (TPMT) is an enzyme that metabolizes purine analogs, agents used in the treatment of acute lymphoblastic leukemia. Improper drug metabolism leads to toxicity in chemotherapy patients and reduces treatment effectiveness. TPMT variants associated with reduced enzymatic activity vary across populations. Therefore, studying these variants in heterogeneous populations, such as Ecuadorians, can help identify molecular causes of deficiency for this enzyme.

We sequenced the entire TPMT coding region in 550 Ecuadorian individuals from Afro-Ecuadorian, Indigenous, Mestizo, and Montubio ethnicities. Moreover, we conducted an ancestry analysis using 46 informative ancestry markers.

We identified 8 single nucleotide variants in the coding region of TPMT. The most prevalent alleles were TPMT*3A, TPMT*3B, and TPMT*3C, with frequencies of 0.055, 0.012, and 0.015, respectively. Additionally, we found rare alleles TPMT*4 and TPMT*8 with frequencies of 0.005 and 0.003. Correlating the ancestry proportions with TPMT-deficient genotypes, we observed that the Native American ancestry proportion influenced the distribution of the TPMT*1/TPMT*3A genotype (OR = 5.977, p = 0.002), while the contribution of African ancestral populations was associated with the TPMT*1/TPMT*3C genotype (OR = 9.769, p = 0.003). The rates of TPMT-deficient genotypes observed in Mestizo (f = 0.121) and Indigenous (f = 0.273) groups provide evidence for the influence of Native American ancestry and the prevalence of the TPMT*3A allele. In contrast, although Afro-Ecuadorian groups demonstrate similar deficiency rates (f = 0.160), the genetic factors involved are associated with contributions from African ancestral populations, specifically the prevalent TPMT*3C allele.

The distribution of TPMT-deficient variants offers valuable insights into the populations under study, underscoring the necessity for genetic screening strategies to prevent thiopurine toxicity events among Latin American minority groups.

The integration of artificial intelligence (AI) into drug discovery has markedly advanced the search for effective therapeutics. In our study, we employed a comprehensive computational-experimental approach to identify potential anti-SARS-CoV-2 compounds. We developed a predictive model to assess the activities of compounds based on their structural features. This model screened a library of approximately 700,000 compounds, culminating in the selection of the top 100 candidates for experimental validation. In vitro assays on human intestinal epithelial cells (Caco-2) revealed that 19 of these compounds exhibited inhibitory activity. Notably, eight compounds demonstrated dose-dependent activity in Vero cell lines, with half-maximal effective concentration (EC50) values ranging from 1 μM to 7 μM. Furthermore, we utilized a clustering approach to pinpoint potential nucleoside analog inhibitors, leading to the discovery of two promising candidates: azathioprine and its metabolite, thioinosinic acid. Both compounds showed in vitro activity against SARS-CoV-2, with thioinosinic acid also significantly reducing viral loads in mouse lungs. These findings underscore the utility of AI in accelerating drug discovery processes.

The clinical effects of tacrolimus (TAC) exposure on hepatocellular carcinoma (HCC) recurrence after liver transplantation (LT) remain unclear. In this retrospective single centric study, 512 patients who underwent LT for HCC were divided into four groups according to cumulative exposure to tacrolimus (CET) during 3 months after LT: conventional (n = 218), aggressive minimization (n = 32), minimization (n = 161), and high exposure (n = 101). Impact of CET on HCC recurrence and death were analyzed. Compared with the conventional group, the other three CET groups showed a similar risk of HCC recurrence. The aggressive minimization group showed a higher risk [hazard ratio (HR) 5.64, P < 0.001] and the high exposure group showed a marginal risk (HR 1.67, P = 0.081) of overall death compared to the conventional group. CET during 3 months was not associated with HCC recurrence in the matched cohort and various subgroups. TAC minimization is not effective to prevent HCC recurrence but could result in higher mortality in LT recipients.

Nuclear deformability plays a critical role in cell migration. During this process, the remodeling of internal components of the nucleus has a direct impact on DNA damage and cell behavior; however, how persistent migration promotes nuclear changes leading to phenotypical and functional consequences remains poorly understood. Here, we described that the persistent migration through physical barriers was sufficient to promote permanent modifications in migratory-altered cells. We found that derived cells from confined migration showed changes in lamin B1 localization, cell morphology and transcription. Further analysis confirmed that migratory-altered cells showed functional differences in DNA repair, cell response to chemotherapy and cell migration in vivo homing experiments. Experimental modulation of actin polymerization affected the redistribution of lamin B1, and the basal levels of DNA damage in migratory-altered cells. Finally, since major nuclear changes were present in migratory-altered cells, we applied a multidisciplinary biochemical and biophysical approach to identify that confined conditions promoted a different biomechanical response of the nucleus in migratory-altered cells. Our observations suggest that mechanical compression during persistent cell migration has a role in stable nuclear and genomic alterations that might handle the genetic instability and cellular heterogeneity in aging diseases and cancer.

The Nudt15 enzyme of the NUDIX protein family is the subject of extensive study due to its action on thiopurine drugs used in the treatment of cancer and inflammatory diseases. In addition to thiopurines, Nudt15 is enzymatically active in vitro on several nucleotide substrates. It has also been suggested that this enzyme may play a role in 5'RNA turnover by hydrolyzing m7GDP, a product of mRNA decapping. However, no detailed studies on this substrate with Nudt15 are available. Here, we analyzed the enzymatic activity of Nudt15 with m7GDP, its triphosphate form m7GTP, and the trimethylated counterparts (m32,2,7GDP and m32,2,7GTP). Kinetic data revealed a moderate activity of Nudt15 toward these methylated mononucleotides compared to the dGTP substrate. However m7GDP and m32,2,7GDP showed a distinct stabilization of Nudt15 upon ligand binding, in the same range as dGTP, and thus these two mononucleotides may be used as leading structures in the design of small molecule binders of Nudt15.

Temozolomide (TMZ) is a standard treatment for glioblastoma (GBM) patients. However, TMZ has moderate therapeutic effects due to chemoresistance of GBM cells through less clarified mechanisms. Here, we demonstrate that TMZ-derived 5-aminoimidazole-4-carboxamide (AICA) is converted to AICA ribosyl-5-phosphate (AICAR) in GBM cells. This conversion is catalyzed by hypoxanthine phosphoribosyl transferase 1 (HPRT1), which is highly expressed in human GBMs. As the bona fide activator of AMP-activated protein kinase (AMPK), TMZ-derived AICAR activates AMPK to phosphorylate threonine 52 (T52) of RRM1, the catalytic subunit of ribonucleotide reductase (RNR), leading to RNR activation and increased production of dNTPs to fuel the repairment of TMZ-induced-DNA damage. RRM1 T52A expression, genetic interruption of HPRT1-mediated AICAR production, or administration of 6-mercaptopurine (6-MP), a clinically approved inhibitor of HPRT1, blocks TMZ-induced AMPK activation and sensitizes brain tumor cells to TMZ treatment in mice. In addition, HPRT1 expression levels are positively correlated with poor prognosis in GBM patients who received TMZ treatment. These results uncover a critical bifunctional role of TMZ in GBM treatment that leads to chemoresistance. Our findings underscore the potential of combined administration of clinically available 6-MP to overcome TMZ chemoresistance and improve GBM treatment.

Small cell lung cancer (SCLC) is one of the deadliest human cancers, with a 5-year survival rate of ∼7%. Here, we performed a targeted proteomics analysis of human SCLC samples and thereby identified hypoxanthine phosphoribosyltransferase 1 (HPRT1) in the salvage purine synthesis pathway as a factor that contributes to SCLC malignancy by promoting cell survival in a glutamine-starved environment. Inhibition of HPRT1 by 6-mercaptopurine (6-MP) in combination with methotrexate (MTX), which blocks the de novo purine synthesis pathway, attenuated the growth of SCLC in mouse xenograft models. Moreover, modulation of host glutamine anabolism with the glutamine synthetase inhibitor methionine sulfoximine (MSO) in combination with 6-MP and MTX treatment resulted in marked tumor suppression and prolongation of host survival. Our results thus suggest that modulation of host glutamine anabolism combined with simultaneous inhibition of the de novo and salvage purine synthesis pathways may be of therapeutic benefit for SCLC.

Ethnicity is known to have an impact on drug responses. This is particularly important for drugs that have a narrow therapeutic window, nonlinearity in pharmacokinetics and are metabolized by enzymes that demonstrate genetic polymorphisms. However, most clinical trials are conducted among Caucasians, which might limit the usefulness of the findings of such studies for other ethnicities. The representation of participants from Saudi Arabia in global clinical trials is low. Therefore, there is a paucity of evidence to assess the impact of ethnic variability in the Saudi population on drug response. In this article, the authors assess the projected impact of genetic polymorphisms in drug-metabolizing enzymes and drug targets on drug response in the Saudi population.

Thiopurines, such as 6-mercaptopurine (6-MP), are widely used as cytotoxic agents and immunosuppressants for leukemia and autoimmune or inflammatory diseases. A nonsynonymous single nucleotide polymorphism (p.Arg139Cys; R139C) of the nucleoside diphosphate-linked moiety X-type motif 15 (NUDT15) gene causes the loss of thiopurine detoxification, inducing myelosuppression. To understand such hematotoxicity, we investigate the effects of NUDT15 R139C on hematopoietic stem cells (HSCs) upon thiopurine administration. Using previously established Nudt15^R138C knock-in mice, which mimic myelosuppression in NUDT15^R139C homozygous or heterozygous patients following thiopurine administration, we investigated the numerical changes of HSCs and hematopoietic progenitor cells following 6-MP administration using in vivo flowcytometry and ex vivo HSC expansion. Genes differentially expressed between Nudt15^+/+ HSCs and Nudt15^R138C/R138C HSCs were identified using RNA-sequencing before the emergence of 6-MP-induced HSC-damage. Gene Ontology (GO) and Transcriptional Regulatory Relationships Unraveled by Sentence-based Text Mining (TRRUST) analyses were performed to elucidate the molecular effects of 6-MP on HSCs. In Nudt15^R138C/R138C mice, 6-MP induced exhaustion of HSCs faster than that of multipotent progenitors and as fast as that of myeloid-committed progenitors. Ex vivo-expanded Nudt15^R138C/R138C HSCs were dose- and time-dependently damaged by 6-MP. GO analysis identified the DNA damage response and cell cycle process as the most strongly influenced processes in Nudt15^R138C/R138C HSCs. TRRUST analysis revealed that the Trp53-regulated transcriptional regulatory network is influenced prior to HSC exhaustion in Nudt15^R138C/R138C HSCs. The loss of NUDT15 thiopurine detoxification enhances thiopurine-mediated DNA damage via the Trp53 networks in HSCs. Therefore, caution is required in long-term thiopurine use in patients with NUDT15 R139C in view of its adverse effects on HSCs in the form of DNA damage.