Cytidine deaminase (CDA) functions in the pyrimidine salvage pathway for DNA and RNA syntheses and has been shown to protect cancer cells from deoxycytidine-based chemotherapies. In this study, we observed that CDA was overexpressed in pancreatic adenocarcinoma from patients at baseline and was essential for experimental tumor growth. Mechanistic investigations revealed that CDA localized to replication forks where it increased replication speed, improved replication fork restart efficiency, reduced endogenous replication stress, minimized DNA breaks, and regulated genetic stability during DNA replication. In cellular pancreatic cancer models, high CDA expression correlated with resistance to DNA-damaging agents. Silencing CDA in patient-derived primary cultures in vitro and in orthotopic xenografts in vivo increased replication stress and sensitized pancreatic adenocarcinoma cells to oxaliplatin. This study sheds light on the role of CDA in pancreatic adenocarcinoma, offering insights into how this tumor type modulates replication stress. These findings suggest that CDA expression could potentially predict therapeutic efficacy and that targeting CDA induces intolerable levels of replication stress in cancer cells, particularly when combined with DNA-targeted therapies.
UNASSIGNED: Cytidine deaminase reduces replication stress and regulates DNA replication to confer resistance to DNA-damaging drugs in pancreatic cancer, unveiling a molecular vulnerability that could enhance treatment response.

Glioblastoma Multiforme (GBM) is the most aggressive form of malignant brain tumor. The median survival rate does not exceed two years, indicating an imminent need to develop novel therapies. The atypical adamantyl retinoid ST1926 induces apoptosis and growth inhibition in different cancer types. We have shown that ST1926 is an inhibitor of the catalytic subunit of DNA polymerase alpha (POLA1), which is involved in initiating DNA synthesis in eukaryotic cells. POLA1 levels are elevated in GBM versus normal brain tissues. Therefore, we studied the antitumor effects of ST1926 in several human GBM cell lines. We further explored the global protein expression profiles in GBM cell lines using liquid chromatography coupled with tandem mass spectrometry to identify new targets of ST1926. Low sub-micromolar concentrations of ST1926 potently decreased cell viability, induced cell damage and apoptosis, and reduced POLA1 protein levels in GBM cells. The proteomics profiles revealed 197 proteins significantly differentially altered upon ST1926 treatment of GBM cells involved in various cellular processes. We explored the differential gene and protein expression of significantly altered proteins in GBM compared to normal brain tissues.

DNA polymerase theta (Polθ)-mediated end joining (TMEJ) is, along with homologous recombination (HR) and non-homologous end-joining (NHEJ), one of the most important mechanisms repairing potentially lethal DNA double-strand breaks (DSBs). Polθ is becoming a new target in cancer research because it demonstrates numerous synthetically lethal interactions with other DNA repair mechanisms, e.g., those involving PARP1, BRCA1/2, DNA-PK, ATR. Inhibition of Polθ could be achieved with different methods, such as RNA interference (RNAi), CRISPR/Cas9 technology, or using small molecule inhibitors. In the context of this topic, RNAi and CRISPR/Cas9 are still more often applied in the research itself rather than clinical usage, different than small molecule inhibitors. Several Polθ inhibitors have been already generated, and two of them, novobiocin (NVB) and ART812 derivative, are being tested in clinical trials against HR-deficient tumors. In this review, we describe the significance of Polθ and the Polθ-mediated TMEJ pathway. In addition, we summarize the current state of knowledge about Polθ inhibitors and emphasize the promising role of Polθ as a therapeutic target.

OBJECTIVE: To evaluate clinical efficacy of nucleoside analogues in therapy of moderate COVID-19 in in-patients.
METHODS: Retrospective processing of 108 completed clinical cases with moderate novel coronavirus disease was carried out for the period 2020-2021. The duration of the disease at the time of admission did not exceed three days. Experimental group consisted of 53 patients who, in addition to standard therapy, were prescribed \"off-label\" riamilovir at a daily dosage of 1250 mg for 5 days by the decision of the medical commission. Comparison group included 55 patients who received a combination of umifenovir and ribavirin as antiviral therapy for 5 days. The duration of the main clinical manifestations of the disease, the indicators of clinical and biochemical blood tests, results of the SARS-CoV-2 virus RNA study using the nucleic acid amplification method (NAAT diagnostics).
RESULTS: Significantly faster achievement of clinical improvement in the group of patients treated with riamilovir was shown, as well as faster sanitation from SARS-CoV-2 virus based on the results of etiological testing.
CONCLUSIONS: The use of riamilovir for the treatment of patients with moderate novel coronavirus infection (COVID-19) resulted in a significant reduction of general infectious syndromes and respiratory symptoms. Patients from the experimental group significantly faster achieved clinical recovery and sanitation from the pathogen according to the results of NAAT diagnostics.
Цель. Оценить клиническую эффективность нуклеозидных аналогов для лечения пациентов с COVID-19 средней степени тяжести в условиях инфекционного стационара. Материалы и методы. Проведена ретроспективная обработка 108 законченных клинических случаев новой коронавирусной инфекции средней степени тяжести за период 2020–2021 гг. Длительность заболевания на момент поступления не превышала 3 сут. Опытная группа состояла из 53 пациентов, которым дополнительно к стандартной терапии по решению врачебной комиссии назначен риамиловир в режиме off-label в суточной дозировке 1250 мг в течение 5 дней. В группу сравнения вошли 55 пациентов, получавших в качестве противовирусной терапии комбинацию умифеновира с рибавирином в течение 5 дней. Оценивали длительность основных клинических проявлений заболевания, показатели клинического и биохимического анализов крови, результаты исследования РНК вируса SARS-CoV-2 с помощью метода амплификации нуклеиновых кислот (МАНК-диагностика). Результаты. Показано статистически значимо более быстрое достижение клинического улучшения в группе пациентов, принимавших риамиловир, а также более быстрая санация от вируса SARS-CoV-2 по результатам этиологической диагностики. Заключение. Применение нуклеозидного аналога риамиловира для лечения пациентов с новой коронавирусной инфекцией (COVID-19) средней степени тяжести приводило к статистически значимому снижению длительности общеинфекционных синдромов, симптомов поражения респираторного тракта. Пациенты из опытной группы статистически значимо быстрее достигали клинического выздоровления и санации от возбудителя по результатам МАНК-диагностики.

BACKGROUND: Listeriosis is an orphan disease, which is nevertheless fatal in immunocompromised people. CRS0540 is a novel PolC DNA polymerase inhibitor that has demonstrated good in vitro and in vivo activity against Listeria monocytogenes.
METHODS: Rodent-to-human allometry projection-based human population pharmacokinetics of CRS0540 were used for all studies. CRS0540 pharmacokinetics/pharmacodynamics studies in an intracellular hollow-fibre system model of disseminated listeriosis (HFS-Lister) examined the effect of eight treatment doses, administered daily over 7 days, in duplicate units. Total bacterial burden versus AUC/MIC exposures on each day were modelled using the inhibitory sigmoid Emax model, while CRS0540-resistant bacterial burden was modelled using a quadratic function. Ten thousand-subject Monte Carlo simulations were used to predict an optimal clinical dose for treatment.
RESULTS: The mean CRS0540 intracellular/extracellular AUC0-24 ratio was 34.07 (standard error: 15.70) as measured in the HFS-Lister. CRS0540 demonstrated exposure-dependent bactericidal activity in the HFS-Lister, with the highest exposure killing approximately 5.0 log10 cfu/mL. The free drug AUC0-24/MIC associated with 80% of maximal kill (EC80) was 36.4. Resistance emergence versus AUC/MIC was described by a quadratic function, with resistance amplification at an AUC/MIC of 54.8 and resistance suppression at an AUC/MIC of 119. Monte Carlo simulations demonstrated that for the EC80 target, IV CRS0540 doses of 100 mg/kg achieved PTAs of >90% at MICs up to 1.0 mg/L.
CONCLUSIONS: CRS0540 is a promising orphan drug candidate for listeriosis. Future PK/PD studies comparing it with penicillin, the standard of care, could lead to this drug as a new treatment in immunocompromised patients.

Cytomegalovirus (CMV) is considered one of the most notable pathogens that affect patients after solid organ transplantation (SOT), especially small bowel transplant patients with a risk of high mortality rate. Its management relies historically on the use of CMV DNA polymerase inhibitors (namely, ganciclovir and valganciclovir). Second-line options include foscarnet and cidofovir, which are highly nephrotoxic and thus less preferred and only used in ganciclovir intolerance or resistance cases. Letermovir is a novel antiviral agent approved for CMV prophylaxis in hematopoietic stem cell transplant, but not for SOT (neither for prophylaxis nor for treatment). We report the first case on the successful use of letermovir in treating CMV disease in a small bowel transplant patient who failed to achieve viral clearance due to ganciclovir resistance and severe intolerance to foscarnet.

We present a protocol to measure the effect of pharmacological treatments on the mechanical tension experienced by nesprins at the cytoplasmic surface of the nuclear envelope of mammalian cells in culture. We apply this protocol to MDCK epithelial cells exposed to the actin depolymerization agent cytochalasin D. To do so, we perform confocal spectral imaging of transiently expressed molecular tension sensors of mini-nesprin 2G and analyze the FRET signal from the sensors with a custom-made Fiji script. For complete details on the use and execution of this protocol, please refer to Déjardin et al. (2020).

Ribosome biogenesis is an energetically expensive program that is dictated by nutrient availability. Here we report that nutrient deprivation severely impairs precursor ribosomal RNA (pre-rRNA) processing and leads to the accumulation of unprocessed rRNAs. Upon nutrient restoration, pre-rRNAs stored under starvation are processed into mature rRNAs that are utilized for ribosome biogenesis. Failure to accumulate pre-rRNAs under nutrient stress leads to perturbed ribosome assembly upon nutrient restoration and subsequent apoptosis via uL5/uL18-mediated activation of p53. Restoration of glutamine alone activates p53 by triggering uL5/uL18 translation. Induction of uL5/uL18 protein synthesis by glutamine is dependent on the translation factor eukaryotic elongation factor 2 (eEF2), which is in turn dependent on Raf/MEK/ERK signaling. Depriving cells of glutamine prevents the activation of p53 by rRNA synthesis inhibitors. Our data reveals a mechanism that tumor cells can exploit to suppress p53-mediated apoptosis during fluctuations in environmental nutrient availability.

Coronavirus disease 2019 (COVID-19) is a newly emerged infectious disease caused by a novel coronavirus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The rapid global emergence of SARS-CoV-2 highlights the importance and urgency for potential drugs to control the pandemic. The functional importance of RNA-dependent RNA polymerase (RdRp) in the viral life cycle, combined with structural conservation and absence of closely related homologs in humans, makes it an attractive target for designing antiviral drugs. Nucleos(t)ide analogs (NAs) are still the most promising broad-spectrum class of viral RdRp inhibitors. In this study, using our previously developed cell-based SARS-CoV-2 RdRp report system, we screened 134 compounds in the Selleckchemicals NAs library. Four candidate compounds, Fludarabine Phosphate, Fludarabine, 6-Thio-20-Deoxyguanosine (6-Thio-dG), and 5-Iodotubercidin, exhibit remarkable potency in inhibiting SARS-CoV-2 RdRp. Among these four compounds, 5-Iodotubercidin exhibited the strongest inhibition upon SARS-CoV-2 RdRp, and was resistant to viral exoribonuclease activity, thus presenting the best antiviral activity against coronavirus from a different genus. Further study showed that the RdRp inhibitory activity of 5-Iodotubercidin is closely related to its capacity to inhibit adenosine kinase (ADK).

OBJECTIVE: Synergistic effects of epidermal growth factor receptor tyrosine kinase inhibitors and chemotherapy have been reported. Here, we evaluated the therapeutic potential of combining osimertinib with pemetrexed and investigated the molecular mechanisms.
METHODS: We analyzed the antitumor effects of osimertinib± pemetrexed in PC-9 and H1975 cells. Gene expression on exposure to osimertinib±pemetrexed was assessed in these cultured cells. Cell lines resistant to osimertinib±pemetrexed were established to explore mechanisms of resistance.
RESULTS: Osimertinib+pemetrexed treatment delayed the emergence of resistance relative to monotherapy in vitro and in vivo. Expression of the anti-apoptotic gene PLK1 was down-regulated in PC-9 and H1975 exposed to osimertinib+ pemetrexed, whereas it was up-regulated in resistant cells. Furthermore, inhibition of PLK1 induced apoptosis and inhibited proliferation of resistant cells.
CONCLUSIONS: Blocking PLK1 contributes to mediating the synergistic anti-proliferative effect of osimertinib+pemetrexed. PLK1 over-expression may be a critical mechanism for acquired resistance to osimertinib+pemetrexed.