Ribonucleotide reductase and cancer: biological mechanisms and targeted therapies

Identification of key biomarker genes in liver hepatocellular carcinoma and kidney renal clear cell carcinoma progression: A shared high-throughput screening and molecular docking method with potentials for targeted therapeutic interventions

BACKGROUND AND OBJECTIVES

Liver Hepatocellular Carcinoma (LIHC) and Kidney Renal Clear Cell Carcinoma (KIRC) are leading causes of cancer death worldwide, but their early detections remain hindered by a lack of genetic markers. Our study aims to find prospective biomarkers that could serve as prognostic indicators for efficient drug candidates for KIRC and LIHC treatment.

METHODS

To detect differentially expressed genes (DEGs), four datasets were used: GSE66271 and GSE213324 for KIRC, and GSE135631 and GSE202853 for LIHC. Visualization of DEGs was done using heatmaps, volcano plots, and Venn diagrams. Hub genes were identified via PPI analysis and the cytoHubba plugin in Cytoscape. Their expression was evaluated using box plots, stage plots, and survival plots for prognostic assessment via GEPIA2. Molecular docking with PyRx's AutoDock Vina identified optimal binding interactions between compounds and proteins. Pharmacokinetic and toxicity analyses reinforced the drug-likeness and safety of these compounds.

RESULTS

In this study, 47 DEGs were identified, with the top 10 hub genes being TOP2A, BUB1, PTTG1, CCNB2, NUSAP1, KIF20A, BIRC5, RRM2, NDC80 and CDC45, chosen for their high MCC scores. Data mining revealed a correlation between TOP2A expression and clinical survival outcomes in KIRC and LIHC patients. Docking studies of the TOP2A structure identified a promising compound from Andrographis paniculata with high binding energy and interactions with TOP2A. Pharmacokinetic and toxicity assessments support its potential as a drug candidate.

CONCLUSION

Our study emphasizes TOP2A's prognostic significance in KIRC and LIHC and recognizes Andrographis paniculata compound as potential therapeutics, offering prospective for enhanced treatment and patient outcomes in these cancers.

RRM1 O-GlcNAcylation inhibition suppresses pancreatic cancer via TK1-mediated replication stress

O-GlcNAcylation of ribonucleotide reductase large subunit M1 (RRM1) at position 734 influences high glucose-induced genomic instability and cell transformation in normal pancreatic cells. By disrupting the ribonucleotide reductase complex, it reduces dNTPs. Although the impact of RRM1 O-GlcNAcylation on pancreatic cancer progression remains unexplored, our CRISPR knock-in technology created the RRM1-T734A mutation to minimize RRM1 O-GlcNAcylation. In pancreatic cancer PANC-1 cells with this mutation, we observed heightened replication stress-induced DNA damage, S-phase delays, and diminished in vitro tumor cell growth. Mechanistically, RRM1-T734A enhanced its interaction with RRM2 while impairing binding to RRM2B, leading to decreased NTPs and disrupted dNTP equilibrium. Notably, it doubled dTTP levels via TK1 stabilization mediated by thymidine, resulting in S-phase delay. TK1 silencing restored RRM1-T734A-induced effects on S-phase retardation and decreased colony formation. Our findings highlight the pivotal role of O-GlcNAcylation of RRM1 at T734 in maintaining genomic stability and promoting pancreatic cancer malignancy. Furthermore, reducing RRM1 O-GlcNAcylation increased pancreatic cancer cell sensitivity to gemcitabine, proposing a potential therapeutic strategy.

Tumoroid Model Reveals Synergistic Impairment of Metabolism by Iron Chelators and Temozolomide in Chemo-Resistant Patient-derived Glioblastoma Cells

Chemoresistance poses a significant clinical challenge in managing glioblastoma (GBM), limiting the long-term success of traditional treatments. Here, a 3D tumoroid model is used to investigate the metabolic sensitivity of temozolomide (TMZ)-resistant GBM cells to iron chelation by deferoxamine (DFO) and deferiprone (DFP). This work shows that TMZ-resistant GBM cells acquire stem-like characteristics, higher intracellular iron levels, higher expression of aconitase, and elevated reliance on oxidative phosphorylation and proteins associated with iron metabolism. Using a microphysiological model of GBM-on-a-chip consisting of extracellular matrix (ECM)-incorporated tumoroids, this work demonstrates that the combination of iron chelators with TMZ induces a synergistic effect on an in vitro tumoroid model of newly diagnosed and recurrent chemo-resistant patient-derived GBM and reduced their size and invasion. Investigating downstream metabolic variations reveal reduced intracellular iron, increased reactive oxygen species (ROS), upregulated hypoxia-inducible factor-1α, reduced viability, increased autophagy, upregulated ribonucleotide reductase (RRM2), arrested proliferation, and induced cell death in normoxic TMZ-resistant cells. Hypoxic cells, while showing similar results, display reduced responses to iron deficiency, less blebbing, and an induced autophagic flux, suggesting an adaptive mechanism associated with hypoxia. These findings show that co-treatment with iron chelators and TMZ induces a synergistic effect, making this combination a promising GBM therapy.

Berberrubine as a novel TrxR inhibitor enhances cisplatin sensitivity in the treatment of non-small cell lung cancer

Thioredoxin reductase (TrxR, TXNRD) is an essential enzyme implicated in the processes of cancer development and progression, positioning it as a promising target for cancer therapeutics. In this study, we employed target-based structural screening to identify berberrubine (BRB), a natural product characterized by an unprecedented isoquinoline scaffold that differs from known TrxR inhibitors. Our findings demonstrate that BRB serves as an effective inhibitor of TrxR, both in the context of the purified enzyme and within cancer cells. Since TrxR is highly expressed in non-small cell lung cancer (NSCLC) and is linked to patient prognosis and drug resistance, our results demonstrate, for the first time, that BRB can enhance the sensitivity of cisplatin to impede the proliferation of A549 cells, which was further confirmed in a xenograft model. The primary reason for cisplatin resistance in NSCLC is the DNA repair mechanism of apoptotic tumor cells. Our subsequent mechanistic investigation discovered that BRB selectively inhibits TrxR and impairs the biologically functional thioredoxin, which ultimately inhibits DNA synthesis and repair in cancer cells. Inhibition of TrxR by BRB led to a significant ROS accumulation in A549 cells, which contributed to oxidative stress-mediated apoptosis when used in combination with cisplatin. Our results conclude that BRB is a novel chemical entity of TrxR inhibitor that can increase the effectiveness of cisplatin in slowing down the growth of NSCLC both in vitro and in vivo. This provides a new perspective on the potential application of the combination of the two in the treatment of NSCLC.

MTCH2 regulates NRF2-mediated RRM1 expression to promote melanoma proliferation and dacarbazine insensitivity

Melanoma is among the 10 most prevalent malignant tumors, posing a significant threat to human health. A detailed understanding of the molecular mechanisms driving its progression is crucial for advancing treatment strategies and outcomes. Based on bioinformatic analysis and experimental validation, this study identified mitochondrial carrier homolog 2 (MTCH2) as a key regulator of melanoma proliferation. Mechanistically, MTCH2 enhanced the expression and nuclear translocation of nuclear factor (erythroid-derived-2)-like 2 (NRF2), which up-regulated ribonucleotide reductase subunit M1 (RRM1) expression, thereby promoting melanoma cell proliferation. Targeting RRM1 in combination with dacarbazine significantly inhibited tumor growth in nude mouse xenograft models. These findings elucidate a mechanistic link between MTCH2 and the NRF2-RRM1 axis in melanoma proliferation and highlight potential therapeutic targets for intervention.

A novel oncolytic vaccinia virus with multiple gene modifications involved in viral replication and maturation increases safety for intravenous administration while maintaining proliferative potential in cancer cells

To generate a novel oncolytic vaccinia virus with improved safety and productivity, the genome of smallpox vaccine strain LC16m8 was modified by a bacterial artificial chromosome system. By using LC16m8, a replicating virus homologous to the target virus, as a helper virus for the bacterial artificial chromosome system, we successfully recovered genome-edited infectious viruses. Oncolytic viruses with limited growth in normal cells were obtained by deleting the genes for vaccinia virus growth factor (VGF), extracellular signal-regulated kinase-activating protein (O1L), and ribonucleotide reductase (RNR) present in the viral genome. Furthermore, the amino acid residues of seven proteins involved in extracellular enveloped virus virion formation were replaced to the IHD-J strain sequence, which is known to highly express extracellular enveloped virus. In cultured cancer cells (HeLa), these modified viruses showed cytotoxicity and increased productivity, but it was confirmed that the cytotoxicity was suppressed in normal cells (normal human dermal fibroblasts). For in vivo safety evaluation, a modified virus (MD-RVV-ΔRR-EEV6) in which the VGF, O1L, and RNR genes of LC16m8 were deleted and the genes of six extracellular enveloped virus-associated proteins were replaced with sequences derived from IHD-J strain, and another modified virus (MD-RVV) lacking only the VGF and O1L were administered intravenously to severe combined immunodeficiency mice. In the MD-RVV administration, animals in all dose groups died by 40 days after virus administration. On the other hand, after MD-RVV-ΔRR-EEV6 administration, 3 out of 5 animals in the high and medium dose groups and all animals in the low dose group were still alive by day 71, the end of the observation period. These results demonstrate that genome editing of oncolytic vaccinia virus can delete genes involved in viral replication to improve safety in normal cells, while replacing genes involved in maturation improves proliferative potential in cancer cells.

FAM43A coordinates mtDNA replication and mitochondrial biogenesis in response to mtDNA depletion

Mitochondrial retrograde signaling (MRS) pathways relay the functional status of mitochondria to elicit homeostatic or adaptive changes in nuclear gene expression. Budding yeast have "intergenomic signaling" pathways that sense the amount of mitochondrial DNA (mtDNA) independently of oxidative phosphorylation (OXPHOS), the primary function of genes encoded by mtDNA. However, MRS pathways that sense the amount of mtDNA in mammalian cells remain poorly understood. We found that mtDNA-depleted IMR90 cells can sustain OXPHOS for a significant amount of time, providing a robust model system to interrogate human intergenomic signaling. We identified FAM43A, a largely uncharacterized protein, as a CHK2-dependent early responder to mtDNA depletion. Depletion of FAM43A activates a mitochondrial biogenesis program, resulting in an increase in mitochondrial mass and mtDNA copy number via CHK2-mediated upregulation of the p53R2 form of ribonucleotide reductase. We propose that FAM43A performs a checkpoint-like function to limit mitochondrial biogenesis and turnover under conditions of mtDNA depletion or replication stress.

Combined inhibition of ribonucleotide reductase and WEE1 induces synergistic anticancer activity in Ewing's sarcoma cells

BACKGROUND

Ewing's sarcoma is a childhood bone and soft tissue cancer with poor prognosis. Treatment outcomes for Ewing's sarcoma patients have improved only modestly over the past decades, making the development of new treatment strategies paramount. In this study, the combined targeting of ribonucleotide reductase (RNR) and WEE1 was explored for its effectiveness against Ewing's sarcoma cells.

METHODS

The RNR inhibitor triapine and the WEE1 inhibitors adavosertib and ZN-c3 were tested in p53 wild-type and p53 mutant Ewing's sarcoma cells. The combination of adavosertib with the PARP inhibitors olaparib and veliparib was tested for comparison. Combinatorial effects were determined by flow cytometric analyses of cell death, loss of mitochondrial membrane potential and DNA fragmentation as well as by caspase 3/7 activity assay, immunoblotting and real-time RT-PCR. The drug interactions were assessed using combination index analysis.

RESULTS

RNR and WEE1 inhibitors were weakly to moderately effective on their own, but highly effective in combination. The combination treatments were similarly effective in p53 wild-type and p53 mutant cells. They synergistically induced cell death and cooperated to elicit mitochondrial membrane potential decay, to activate caspase 3/7 and to trigger DNA fragmentation, evidencing the induction of the apoptotic cell death cascade. They also cooperated to boost CHK1 phosphorylation, indicating augmented replication stress after combination treatment. In comparison, the combination of adavosertib with PARP inhibitors produced weaker synergistic effects.

CONCLUSION

Our findings show that combined inhibition of RNR and WEE1 was effective against Ewing's sarcoma in vitro. They thus provide a rationale for the evaluation of the potential of combined targeting of RNR and WEE1 in Ewing's sarcoma in vivo.

Hydrogen Tunneling and Conformational Motions in Nonadiabatic Proton-Coupled Electron Transfer between Interfacial Tyrosines in Ribonucleotide Reductase

Ribonucleotide reductase (RNR) is essential for DNA synthesis and repair in all living organisms. The mechanism of E. coli RNR requires long-range radical transport through a proton-coupled electron transfer (PCET) pathway spanning two different protein subunits. Herein, the direct PCET reaction between the interfacial tyrosine residues, Y356 and Y731, is investigated with a vibronically nonadiabatic theory that treats the transferring proton and all electrons quantum mechanically. The input quantities to the PCET rate constant expression are computed with a combination of density functional theory and molecular dynamics simulations. The calculations highlight the importance of hydrogen tunneling in this PCET reaction. Compression of the distance between the proton donor and acceptor oxygen atoms of the interfacial tyrosine residues is essential to facilitate hydrogen tunneling by increasing the overlap between the reactant and product proton vibrational wave functions. This compression occurs by thermal conformational fluctuations of these interfacial tyrosine residues. N733 and R411 are identified as key residues that can hydrogen bond to Y731 and Y356, respectively, and thereby compete with the hydrogen-bonding interaction between Y731 and Y356 required for direct PCET. Understanding the roles of hydrogen tunneling and conformational motions in this interfacial PCET reaction, as well as identifying other residues that may impact the kinetics, is important for targeted protein engineering efforts to modulate RNR activity.

Disruption of deoxyribonucleotide triphosphate biosynthesis leads to RAS proto-oncogene activation and perturbation of mitochondrial metabolism

Perturbation of the deoxyribonucleotide triphosphate (dNTP) pool is recognized for contributing to the mutagenic processes involved in oncogenesis. The RAS gene family encodes well-characterized oncoproteins whose structure and function are among the most frequently altered in several cancers. In this work, we show that fluctuation of the dNTP pool induces CG → TA mutations across the whole genome, including RAS gene at codons for glycine 12 and 13, known hotspots in cancers. Cell culture addition of the ribonucleotide reductase inhibitor thymidine increases the mutation frequency in nuclear DNA and leads to disruption of mitochondrial metabolism. Interestingly, this effect is counteracted by the addition of deoxycytidine. Finally, screening for the loss of hydrogen bonds detecting CG → TA transition in RAS gene of 135 patients with colorectal cancer confirmed the clinical relevance of this process. All together, these data demonstrate that fluctuation of intracellular dNTP pool alters the nuclear DNA and mitochondrial metabolism.

RRM1 promotes homologous recombination and radio/chemo-sensitivity via enhancing USP11 and E2F1-mediated RAD51AP1 transcription

Ribonucleotide reductase M1 (RRM1), the catalytic subunit of ribonucleotide reductase, plays a pivotal role in converting ribonucleotides (NTP) into deoxyribonucleotides (dNTP), essential for DNA replication and repair. Elevated RRM1 expression is associated with various human cancers, correlating with poorer prognosis and reduced overall survival rates. Our previous study found that RRM1 will enter the nucleus to promote DNA damage repair. However, the underlying mechanism remains elusive. Here, we unveil a novel role of RRM1 in promoting homologous recombination (HR) by upregulating the expression of RAD51AP1, a critical HR factor, in an E2F1-dependent manner. We demonstrate that RRM1 interacts with USP11 in the cytoplasm, and the recruitment of RRM1 to LaminB1 induced by ionizing radiation (IR) facilitates the binding of USP11 to the nuclear pore complex (NPC), promoting USP11 entry into the nucleus. Upon nuclear translocation, USP11 binds to E2F1 and inhibits the ubiquitin-mediated degradation of E2F1, thereby enhancing the transcriptional expression of RAD51AP1. Moreover, a specific RRM1 mutant lacking amino acids 731-793, crucial for its interaction with USP11 and recruitment to LaminB1, exhibits a dominant-negative effect on RAD51AP1 expression and HR. Truncations of RRM1 fail to inhibit the ubiquitin-mediated degradation of E2F1 and cannot promote the E2F1-mediated transactivation of RAD51AP1. Lastly, the full length of RRM1, not truncations, enhances tumor cells' sensitivity to IR, underscoring its importance in radiotherapy resistance. Collectively, our results suggest a novel function of RRM1 in promoting HR-mediated DSB repair through positive regulation of RAD51AP1 transcription by direct interaction with USP11 and promoting subsequent USP11-mediated deubiquitination of E2F1. Our findings elucidate a previously unknown mechanism whereby RRM1 promotes HR-mediated DNA repair, presenting a potential therapeutic target for cancer treatment.

RRM2 inhibition alters cell cycle through ATM/Rb/E2F1 pathway in atypical teratoid rhabdoid tumor

BACKGROUND

Atypical teratoid rhabdoid tumor (ATRT) is an aggressive brain tumor that mainly affects young children. Our recent study reported a promising therapeutic strategy to trigger DNA damage, impede homologous recombination repair, and induce apoptosis in ATRT cells by targeting ribonucleotide reductase regulatory subunit M2 (RRM2). COH29, an inhibitor of RRM2, effectively reduced tumor growth and prolonged survival in vivo. Herein, we explored the underlying mechanisms controlling these functions to improve the clinical applicability of COH29 in ATRT.

METHODS

Molecular profiling of ATRT patients and COH29-treated cells was analyzed to identify the specific signaling pathways, followed by validation using a knockdown system, flow cytometry, q-PCR, and western blot.

RESULTS

Elevated E2F1 and its signaling pathway were correlated with poor prognosis. RRM2 inhibition induced DNA damage and activated ATM, which reduced Rb phosphorylation to promote Rb-E2F1 interaction and hindered E2F1 functions. E2F1 activity suppression led to decreased E2F1-dependent target expressions, causing cell cycle arrest in the G1 phase, decreased S phase cells, and blocked DNA damage repair.

CONCLUSION

Our study highlights the role of ATM/Rb/E2F1 pathway in controlling cell cycle arrest and apoptosis in response to RRM2 inhibition-induced DNA damage. This provides insight into the therapeutic benefits of COH29 and suggests targeting this pathway as a potential treatment for ATRT.

An Integrated Framework to Identify Prognostic Biomarkers and Novel Therapeutic Targets in Hepatocellular Carcinoma-Based Disabilities

Hepatocellular carcinoma (HCC) is one of the most prevalent malignant tumors globally, significantly affecting liver functions, thus necessitating the identification of biomarkers and effective therapeutics to improve HCC-based disabilities. This study aimed to identify prognostic biomarkers, signaling cascades, and candidate drugs for the treatment of HCC through integrated bioinformatics approaches such as functional enrichment analysis, survival analysis, molecular docking, and simulation. Differential expression and functional enrichment analyses revealed 176 common differentially expressed genes from two microarray datasets, GSE29721 and GSE49515, significantly involved in HCC development and progression. Topological analyses revealed 12 hub genes exhibiting elevated expression in patients with higher tumor stages and grades. Survival analyses indicated that 11 hub genes (CCNB1, AURKA, RACGAP1, CEP55, SMC4, RRM2, PRC1, CKAP2, SMC2, UHRF1, and FANCI) and three transcription factors (E2F1, CREB1, and NFYA) are strongly linked to poor patient survival. Finally, molecular docking and simulation identified seven candidate drugs with stable complexes to their target proteins: tozasertib (-9.8 kcal/mol), tamatinib (-9.6 kcal/mol), ilorasertib (-9.5 kcal/mol), hesperidin (-9.5 kcal/mol), PF-562271 (-9.3 kcal/mol), coumestrol (-8.4 kcal/mol), and clofarabine (-7.7 kcal/mol). These findings suggest that the identified hub genes and TFs could serve as valuable prognostic biomarkers and therapeutic targets for HCC-based disabilities.

Identification and Analysis of Anticancer Therapeutic Targets from the Polysaccharide Krestin (PSK) and Polysaccharopeptide (PSP) Using Inverse Docking

The natural compounds PSK and PSP have antitumor and immunostimulant properties. These pharmacological benefits have been documented in vitro and in vivo, although there is no information in silico which describes the action mechanisms at the molecular level. In this study, the inverse docking method was used to identify the interactions of PSK and PSP with two local databases: BPAT with 66 antitumor proteins, and BPSIC with 138 surfaces and intracellular proteins. This led to the identification interactions and similarities of PSK and the AB680 inhibitor in the active site of CD73. It was also found that PSK binds to CD59, interacting with the amino acids APS22 and PHE23, which coincide with the rlLYd4 internalization inhibitor. With the isoform of the K-RAS protein, PSK bonded to the TYR32 amino acid at switch 1, while with BAK it bonded to the region of the α1 helix, while PSP bonded to the activation site and the C-terminal and N-terminal ends of that helix. In Bcl-2, PSK interacted at the binding site of the Venetoclax inhibitor, showing similarities with the amino acids ASP111, VAL133, LEU137, MET115, PHE112, and TYR108, while PSP had similarities with THR132, VAL133, LEU137, GLN118, MET115, APS111, PHE112, and PHE104.

R-loop formation contributes to mTORC1 activation-dependent DNA replication stress induced by p53 deficiency

DNA replication stress is a significant contributor to spontaneous DNA damage and genome instability. While the impact of p53 deficiency on increasing DNA replication stress is known, the specific molecular mechanism underlying this phenomenon remains poorly understood. This study explores how p53 deficiency induces DNA replication stress by activating mTORC1 through R-loop formation, which is facilitated by the upregulation of RNR. Research has shown that p53 deficiency results in increased γH2AX expression and a higher mutation rate in the HPRT gene. Interestingly, these effects can be alleviated by rapamycin, an mTORC1 inhibitor. Additionally, rapamycin reduces the abundance of R-loop structures in p53KO cells, which is linked to mTORC1's regulation of ribonucleotide reductase (RNR) level. These findings suggest that p53 deficiency-induced DNA replication stress relies on mTORC1 activation, with the upregulation of RNR expression and R-loop formation. Overall, this study underscores the importance of R-loops in mTORC1 activation-dependent DNA replication stress triggered by p53 deficiency.

Loss of Diphthamide Increases DNA Replication Stress in Mammalian Cells by Modulating the Translation of RRM1

Diphthamide (DPH) is a highly conserved post-translational modification exclusively present in eukaryotic translation elongation factor 2 (eEF2), with its loss leading to embryonic lethality in mice and developmental disorders in humans. In this study, we unveil the role of diphthamide in mammalian cell DNA damage stress, with a particular emphasis on DNA replication stress. We developed a systematic strategy to identify human proteins affected by diphthamide with a combination of computational profiling and quantitative proteomics. Through this approach, we determine that the translation of RRM1 is modulated by diphthamide via -1 frameshifting. Importantly, our results reveal that the dysregulation of RRM1 translation in DPH-deficient cells is causally linked to elevated DNA replication stress. These findings provide a potential explanation for how diphthamide deficiency leads to cancer and developmental defects in humans.

Thioredoxin System in Insects: Uncovering the Roles of Thioredoxins and Thioredoxin Reductase beyond the Antioxidant Defences

Increased levels of reactive oxygen species (ROS) produced during aerobic metabolism in animals can negatively affect the intracellular redox status, cause oxidative stress and interfere with physiological processes in the cells. The antioxidant defence regulates ROS levels by interplaying diverse enzymes and non-enzymatic metabolites. The thioredoxin system, consisting of the enzyme thioredoxin reductase (TrxR), the redox-active protein thioredoxin (Trx) and NADPH, represent a crucial component of antioxidant defence. It is involved in the signalling and regulation of multiple developmental processes, such as cell proliferation or apoptotic death. Insects have evolved unique variations of TrxR, which resemble mammalian enzymes in overall structure and catalytic mechanisms, but the selenocysteine-cysteine pair in the active site is replaced by a cysteine-cysteine pair typical of bacteria. Moreover, the role of the thioredoxin system in insects is indispensable due to the absence of glutathione reductase, an essential enzyme of the glutathione system. However, the functions of the Trx system in insects are still poorly characterised. In the present review, we provide a critical overview of the current knowledge on the insect Trx system, focusing mainly on TrxR's role in the antioxidant and immune system of model insect species.

Growth Signaling Networks Orchestrate Cancer Metabolic Networks

Normal cells grow and divide only when instructed to by signaling pathways stimulated by exogenous growth factors. A nearly ubiquitous feature of cancer cells is their capacity to grow independent of such signals, in an uncontrolled, cell-intrinsic manner. This property arises due to the frequent oncogenic activation of core growth factor signaling pathway components, including receptor tyrosine kinases, PI3K-AKT, RAS-RAF, mTORC1, and MYC, leading to the aberrant propagation of pro-growth signals independent of exogenous growth factors. The growth of both normal and cancer cells requires the acquisition of nutrients and their anabolic conversion to the primary macromolecules underlying biomass production (protein, nucleic acids, and lipids). The core growth factor signaling pathways exert tight regulation of these metabolic processes and the oncogenic activation of these pathways drive the key metabolic properties of cancer cells and tumors. Here, we review the molecular mechanisms through which these growth signaling pathways control and coordinate cancer metabolism.

Loss of Dnajc21 leads to cytopenia and altered nucleotide metabolism in zebrafish

Mutations in the DNAJC21 gene were recently described in Shwachman-Diamond syndrome (SDS), a bone marrow failure syndrome with high predisposition for myeloid malignancies. To study the underlying biology in hematopoiesis regulation and disease, we generated the first in vivo model of Dnajc21 deficiency using the zebrafish. Zebrafish dnajc21 mutants phenocopy key SDS patient phenotypes such as cytopenia, reduced growth, and defective protein synthesis. We show that cytopenia results from impaired hematopoietic differentiation, accumulation of DNA damage, and reduced cell proliferation. The introduction of a biallelic tp53 mutation in the dnajc21 mutants leads to the development of myelodysplastic neoplasia-like features defined by abnormal erythroid morphology and expansion of hematopoietic progenitors. Using transcriptomic and metabolomic analyses, we uncover a novel role for Dnajc21 in nucleotide metabolism. Exogenous nucleoside supplementation restores neutrophil counts, revealing an association between nucleotide imbalance and neutrophil differentiation, suggesting a novel mechanism in dnajc21-mutant SDS biology.

How ATP and dATP Act as Molecular Switches to Regulate Enzymatic Activity in the Prototypical Bacterial Class Ia Ribonucleotide Reductase

Class Ia ribonucleotide reductases (RNRs) are allosterically regulated by ATP and dATP to maintain the appropriate deoxyribonucleotide levels inside the cell for DNA biosynthesis and repair. RNR activity requires precise positioning of the β2 and α2 subunits for the transfer of a catalytically essential radical species. Excess dATP inhibits RNR through the creation of an α-β interface that restricts the ability of β2 to obtain a position that is capable of radical transfer. ATP breaks the α-β interface, freeing β2 and restoring enzyme activity. Here, we investigate the molecular basis for allosteric activity regulation in the well-studied Escherichia coli class Ia RNR through the determination of six crystal structures and accompanying biochemical and mutagenesis studies. We find that when dATP is bound to the N-terminal regulatory cone domain in α, a helix unwinds, creating a binding surface for β. When ATP displaces dATP, the helix rewinds, dismantling the α-β interface. This reversal of enzyme inhibition requires that two ATP molecules are bound in the cone domain: one in the canonical nucleotide-binding site (site 1) and one in a site (site 2) that is blocked by phenylalanine-87 and tryptophan-28 unless ATP is bound in site 1. When ATP binds to site 1, histidine-59 rearranges, prompting the movement of phenylalanine-87 and trytophan-28, and creating site 2. dATP hydrogen bonds to histidine-59, preventing its movement. The importance of site 2 in the restoration of RNR activity by ATP is confirmed by mutagenesis. These findings have implications for the design of bacterial RNR inhibitors.

Ribonucleotide reductase small subunit M2 promotes the proliferation of esophageal squamous cell carcinoma cells via HuR-mediated mRNA stabilization

Esophageal squamous cell carcinoma (ESCC), a malignancy of the digestive system, is highly prevalent and the primary cause of cancer-related deaths worldwide due to the lack of early diagnostic biomarkers and effective therapeutic targets. Dysregulated ribonucleotide reductase (RNR) expression has been confirmed to be causally linked to tumorigenesis. This study demonstrated that ribonucleotide reductase small subunit M2 (RRM2) is significantly upregulated in ESCC tissue and that its expression is negatively correlated with clinical outcomes. Mechanistically, HuR promotes RRM2 mRNA stabilization by binding to the adenine/uridine (AU)-rich elements (AREs) within the 3'UTR, resulting in persistent overexpression of RRM2. Furthermore, bifonazole is identified as an inhibitor of HuR via computational screening and molecular docking analysis. Bifonazole disrupts HuR-ARE interactions by competitively binding to HuR at F65, R97, I103, and R153 residues, resulting in reduced RRM2 expression. Furthermore, bifonazole exhibited antitumor effects on ESCC patient-derived xenograft (PDX) models by decreasing RRM2 expression and the dNTP pool. In summary, this study reveals the interaction network among HuR, RRM2, and bifonazole and demonstrated that bifonazole is a potential therapeutic compound for ESCC through inhibition of the HuR/RRM2 axis.

KAT7 suppresses tumorigenesis in clear cell renal cell carcinoma (ccRCC) by regulating cell cycle and ferroptosis sensitivity

Clear cell renal cell carcinoma (ccRCC) is one of the most aggressive malignancies in the urological system, known for its high immunogenicity. However, its pathogenesis remains unclear. This study utilized bioinformatics algorithms and in vitro experiments to investigate the role of KAT7 in ccRCC. The results indicate that KAT7 is significantly downregulated in ccRCC tissues and cell lines, which is linked to distant metastasis and unfavorable outcomes in ccRCC patients. Overexpression of KAT7 in vitro notably decreased the proliferation, migration, and invasion of renal cancer cells and inhibited Epithelial-Mesenchymal Transition (EMT). Additionally, Gene Set Enrichment Analysis (GSEA) demonstrated that KAT7-related gene functions are associated with cell cycle and ferroptosis transcription factors. Treatment with a KAT7 acetylation inhibitor in ccRCC cell lines reversed the S phase arrest caused by KAT7 overexpression. Similarly, ferroptosis inhibitors alleviated ferroptosis induced by overexpressed KAT7. In conclusion, the findings suggest that KAT7 acts as a tumor suppressor in ccRCC by modulating the cell cycle and ferroptosis sensitivity, underscoring its potential as a therapeutic target and prognostic biomarker for renal cell carcinoma patients.

EWS-FLI1 and Activator Protein-1 (AP-1) Reciprocally Regulate Extracellular-Matrix Proteins in Ewing sarcoma Cells

Ribonucleotide reductase (RNR) is the rate-limiting enzyme in the synthesis of deoxyribonucleotides and the target of multiple chemotherapy drugs, including gemcitabine. We previously identified that inhibition of RNR in Ewing sarcoma tumors upregulates the expression levels of multiple members of the activator protein-1 (AP-1) transcription factor family, including c-Jun and c-Fos, and downregulates the expression of c-Myc. However, the broader functions and downstream targets of AP-1, which are highly context- and cell-dependent, are unknown in Ewing sarcoma tumors. Consequently, in this work, we used genetically defined models, transcriptome profiling, and gene-set -enrichment analysis to identify that AP-1 and EWS-FLI1, the driver oncogene in most Ewing sarcoma tumors, reciprocally regulate the expression of multiple extracellular-matrix proteins, including fibronectins, integrins, and collagens. AP-1 expression in Ewing sarcoma cells also drives, concurrent with these perturbations in gene and protein expression, changes in cell morphology and phenotype. We also identified that EWS-FLI1 dysregulates the expression of multiple AP-1 proteins, aligning with previous reports demonstrating genetic and physical interactions between EWS-FLI1 and AP-1. Overall, these results provide novel insights into the distinct, EWS-FLI1-dependent features of Ewing sarcoma tumors and identify a novel, reciprocal regulation of extracellular-matrix components by EWS-FLI1 and AP-1.

Inhibition of ribonucleotide reductase subunit M2 enhances the radiosensitivity of metastatic pancreatic neuroendocrine tumor

Ribonucleotide Reductase (RNR) is a rate-limiting enzyme in the production of deoxyribonucleoside triphosphates (dNTPs), which are essential substrates for DNA repair after radiation damage. We explored the radiosensitization property of RNR and investigated a selective RRM2 inhibitor, 3-AP, as a radiosensitizer in the treatment of metastatic pNETs. We investigated the role of RNR subunit, RRM2, in pancreatic neuroendocrine (pNET) cells and responses to radiation in vitro. We also evaluated the selective RRM2 subunit inhibitor, 3-AP, as a radiosensitizer to treat pNET metastases in vivo. Knockdown of RNR subunits demonstrated that RRM1 and RRM2 subunits, but not p53R3, play significant roles in cell proliferation. RRM2 inhibition activated DDR pathways through phosphorylation of ATM and DNA-PK protein kinases but not ATR. RRM2 inhibition also induced Chk1 and Chk2 phosphorylation, resulting in G1/S phase cell cycle arrest. RRM2 inhibition sensitized pNET cells to radiotherapy and induced apoptosis in vitro. In vivo, we utilized pNET subcutaneous and lung metastasis models to examine the rationale for RNR-targeted therapy and 3-AP as a radiosensitizer in treating pNETs. Combination treatment significantly increased apoptosis of BON (human pNET) xenografts and significantly reduced the burden of lung metastases. Together, our results demonstrate that selective RRM2 inhibition induced radiosensitivity of metastatic pNETs both in vitro and in vivo. Therefore, treatment with the selective RRM2 inhibitor, 3-AP, is a promising radiosensitizer in the therapeutic armamentarium for metastatic pNETs.

Understanding the interplay between dNTP metabolism and genome stability in cancer

The size and composition of the intracellular DNA precursor pool is integral to the maintenance of genome stability, and this relationship is fundamental to our understanding of cancer. Key aspects of carcinogenesis, including elevated mutation rates and induction of certain types of DNA damage in cancer cells, can be linked to disturbances in deoxynucleoside triphosphate (dNTP) pools. Furthermore, our approaches to treat cancer heavily exploit the metabolic interplay between the DNA and the dNTP pool, with a long-standing example being the use of antimetabolite-based cancer therapies, and this strategy continues to show promise with the development of new targeted therapies. In this Review, we compile the current knowledge on both the causes and consequences of dNTP pool perturbations in cancer cells, together with their impact on genome stability. We outline several outstanding questions remaining in the field, such as the role of dNTP catabolism in genome stability and the consequences of dNTP pool expansion. Importantly, we detail how our mechanistic understanding of these processes can be utilised with the aim of providing better informed treatment options to patients with cancer.

Gemcitabine as chemotherapy of head and neck cancer in Fanconi anemia patients

Fanconi anemia (FA) is a rare hereditary disease resulting from an inactivating mutation in the FA/BRCA pathway, critical for the effective repair of DNA interstrand crosslinks (ICLs). The disease is characterized by congenital abnormalities, progressing bone marrow failure, and an increased risk of developing malignancies early in life, in particular head and neck squamous cell carcinoma (HNSCC). While ICL-inducing cisplatin combined with radiotherapy is a mainstay of HNSCC treatment, cisplatin is contra-indicated for FA-HNSCC patients. This dilemma necessitates the identification of novel treatment modalities tolerated by FA-HNSCC patients. To identify druggable targets, an siRNA-based genetic screen was previously performed in HNSCC-derived cell lines from FA and non-FA tumor origin. Here, we report that the Ribonucleotide Reductase (RNR) complex, consisting of the RRM1 and RRM2 subunits, was identified as a therapeutic target for both, FA and non-FA HNSCC. While non-FA HNSCC cells responded differentially to RNR depletion, FA-HNSCC cells were consistently found hypersensitive. This insight was confirmed pharmacologically using 2', 2'-difluoro 2'deoxycytidine (dFdC), also known as gemcitabine, a clinically used nucleotide analog that is a potent inhibitor of the RNR complex. Importantly, while cisplatin exposure displayed severe, long-lasting toxicity on the hematopoietic stem and progenitor compartments in Fancg-/- mice, gemcitabine was well tolerated and had only a mild, transient impact. Taken together, our data implicate that gemcitabine-based chemoradiotherapy could serve as an alternative HNSCC treatment in Fanconi patients, and deserves clinical testing.

POLM variant G312R promotes ovarian tumorigenesis through genomic instability and COL11A1-NF-κB axis

In ovarian cancer (OC), identifying key molecular players in disease escalation and chemoresistance remains critical. Our investigation elucidates the role of the DNA polymerase mu (POLM), especially G312R mutation, in propelling oncogenesis through dual pathways. POLMG312R markedly augments the ribonucleotide insertion capability of POLM, precipitating genomic instability. In addition, our research reveals that POLMG312R perturbs collagen alpha-1 (XI) chain (COL11A1) expression-a gene that plays a key role in oncogenesis-and modulates the NF-κB signaling pathway, alters the secretion of downstream inflammatory cytokines, and promotes tumor-macrophage interactions. We illustrate a bidirectional regulatory interaction between POLM, particularly its G312R variant, and COL11A1. This interaction regulates NF-κB signaling, culminating in heightened malignancy and resistance to chemotherapy in OC cells. These insights position the POLM as a potential molecular target for OC therapy, shedding light on the intricate pathways underpinning POLM variant disease progression.NEW & NOTEWORTHY Our research reveals that POLM plays an important role in ovarian cancer development, especially the mutation G312R. We uncover the POLMG312R mutation as a driver of genomic instability in ovarian cancer via aberrant ribonucleotide incorporation. We reveal that POLMG312R upregulates COL11A1 and activates NF-κB signaling, contributing to tumor progression and chemoresistance. This study identifies the POLM-COL11A1-NF-κB axis as a novel oncogenic pathway.

The thioredoxin system determines CHK1 inhibitor sensitivity via redox-mediated regulation of ribonucleotide reductase activity

Checkpoint kinase 1 (CHK1) is critical for cell survival under replication stress (RS). CHK1 inhibitors (CHK1i's) in combination with chemotherapy have shown promising results in preclinical studies but have displayed minimal efficacy with substantial toxicity in clinical trials. To explore combinatorial strategies that can overcome these limitations, we perform an unbiased high-throughput screen in a non-small cell lung cancer (NSCLC) cell line and identify thioredoxin1 (Trx1), a major component of the mammalian antioxidant-system, as a determinant of CHK1i sensitivity. We establish a role for redox recycling of RRM1, the larger subunit of ribonucleotide reductase (RNR), and a depletion of the deoxynucleotide pool in this Trx1-mediated CHK1i sensitivity. Further, the TrxR inhibitor auranofin, an approved anti-rheumatoid arthritis drug, shows a synergistic interaction with CHK1i via interruption of the deoxynucleotide pool. Together, we show a pharmacological combination to treat NSCLC that relies on a redox regulatory link between the Trx system and mammalian RNR activity.

Iron, Copper, and Selenium: Cancer's Thing for Redox Bling

Cells require micronutrients for numerous basic functions. Among these, iron, copper, and selenium are particularly critical for redox metabolism, and their importance is heightened during oncogene-driven perturbations in cancer. In this review, which particularly focuses on iron, we describe how these micronutrients are carefully chaperoned about the body and made available to tissues, a process that is designed to limit the toxicity of free iron and copper or by-products of selenium metabolism. We delineate perturbations in iron metabolism and iron-dependent proteins that are observed in cancer, and describe the current approaches being used to target iron metabolism and iron-dependent processes.

Probing Nonadiabaticity of Proton-Coupled Electron Transfer in Ribonucleotide Reductase

The enzyme ribonucleotide reductase, which is essential for DNA synthesis, initiates the conversion of ribonucleotides to deoxyribonucleotides via radical transfer over a 32 Å pathway composed of proton-coupled electron transfer (PCET) reactions. Previously, the first three PCET reactions in the α subunit were investigated with hybrid quantum mechanical/molecular mechanical (QM/MM) free energy simulations. Herein, the fourth PCET reaction in this subunit between C439 and guanosine diphosphate (GDP) is simulated and found to be slightly exoergic with a relatively high free energy barrier. To further elucidate the mechanisms of all four PCET reactions, we analyzed the vibronic and electron-proton nonadiabaticities. This analysis suggests that interfacial PCET between Y356 and Y731 is vibronically and electronically nonadiabatic, whereas PCET between Y731 and Y730 and between C439 and GDP is fully adiabatic and PCET between Y730 and C439 is in the intermediate regime. These insights provide guidance for selecting suitable rate constant expressions for these PCET reactions.

miRNAs as predictive biomarkers of response to treatment in pediatric patients with acute lymphoblastic leukemia

MicroRNAs (miRNAs/miRs) are promising prognostic biomarkers in pediatric acute lymphoblastic leukemia (ALL). The present study aimed to identify miRNAs that could serve as prognostic biomarkers or as novel therapeutic targets in ALL. The expression levels of 84 miRNAs were assessed in the bone marrow aspirates of 10 pediatric patients with newly diagnosed ALL at diagnosis and on day 33 of induction of the ALL Intercontinental Berlin-Frankfurt-Münster 2009 protocol, and associations with established prognostic factors were evaluated. The levels at diagnosis of 25 miRNAs were associated with ≥2 prognostic factors. Higher expression levels of let-7c-5p, miR-106b-5p, miR-26a-5p, miR-155-5p, miR-191-5p, miR-30b-5p and miR-31-5p were significantly associated with a good prednisone response. The expression levels of miR-125b-5p, miR-150-5p and miR-99a-5p were significantly higher in standard- or intermediate-risk patients compared with those in high-risk patients (P=0.017, P=0.033 and P=0.017, respectively), as well as in those with a complete response at the end of induction (P=0.044 for all three miRNAs). The change in expression levels between diagnosis and the end of induction differed significantly between risk groups for three miRNAs: miR-206, miR-210 and miR-99a (P=0.033, P=0.047 and P=0.008, respectively), with the post induction levels of miR-206 increased in high-risk patients, whilst miR-210 and miR-99a levels were increased in intermediate/standard risk patients. Therefore, miRNAs that could be integrated into the risk stratification of pediatric ALL after further evaluation in larger patient cohorts were identified.

Class Ib Ribonucleotide Reductases: Activation of a Peroxido-MnIIMnIII to Generate a Reactive Oxo-MnIIIMnIV Oxidant

In the postulated catalytic cycle of class Ib Mn2 ribonucleotide reductases (RNRs), a MnII2 core is suggested to react with superoxide (O2·-) to generate peroxido-MnIIMnIII and oxo-MnIIIMnIV entities prior to proton-coupled electron transfer (PCET) oxidation of tyrosine. There is limited experimental support for this mechanism. We demonstrate that [MnII2(BPMP)(OAc)2](ClO4) (1, HBPMP = 2,6-bis[(bis(2 pyridylmethyl)amino)methyl]-4-methylphenol) was converted to peroxido-MnIIMnIII (2) in the presence of superoxide anion that converted to (μ-O)(μ-OH)MnIIIMnIV (3) via the addition of an H+-donor (p-TsOH) or (μ-O)2MnIIIMnIV (4) upon warming to room temperature. The physical properties of 3 and 4 were probed using UV-vis, EPR, X-ray absorption, and IR spectroscopies and mass spectrometry. Compounds 3 and 4 were capable of phenol oxidation to yield a phenoxyl radical via a concerted PCET oxidation, supporting the proposed mechanism of tyrosyl radical cofactor generation in RNRs. The synthetic models demonstrate that the postulated O2/Mn2/tyrosine activation mechanism in class Ib Mn2 RNRs is plausible and provides spectral insights into intermediates currently elusive in the native enzyme.

Oncolytic vaccinia virus and cancer immunotherapy

Oncolytic virotherapy (OVT) is a promising form of cancer treatment that uses genetically engineered viruses to replicate within cancer cells and trigger anti-tumor immune response. In addition to killing cancer cells, oncolytic viruses can also remodel the tumor microenvironment and stimulate a long-term anti-tumor immune response. Despite achieving positive results in cellular and organismal studies, there are currently only a few approved oncolytic viruses for clinical use. Vaccinia virus (VACV) has emerged as a potential candidate due to its ability to infect a wide range of cancer cells. This review discusses the mechanisms, benefits, and clinical trials of oncolytic VACVs. The safety and efficacy of different viral backbones are explored, as well as the effects of oncolytic VACVs on the tumor microenvironment. The potential combination of oncolytic VACVs with immunotherapy or traditional therapies is also highlighted. The review concludes by addressing prospects and challenges in the field of oncolytic VACVs, with the aim of promoting further research and application in cancer therapy.

Lysine demethylase 5B (KDM5B): A key regulator of cancer drug resistance

Chemoresistance, a roadblock in the chemotherapy process, has been impeding its effective treatment. KDM5B, a member of the histone demethylase family, has been crucial in the emergence and growth of malignancies. More significantly, KDM5B has recently been linked closely to cancer's resistance to chemotherapy. In this review, we explain the biological properties of KDM5B, its function in the emergence and evolution of cancer treatment resistance, and our hopes for future drug resistance-busting combinations involving KDM5B and related targets or medications.

Inflammation-Associated Cytotoxic Agents in Tumorigenesis

Chronic inflammatory processes are related to all stages of tumorigenesis. As inflammation is closely associated with the activation and release of different cytotoxic agents, the interplay between cytotoxic agents and antagonizing principles is highlighted in this review to address the question of how tumor cells overcome the enhanced values of cytotoxic agents in tumors. In tumor cells, the enhanced formation of mitochondrial-derived reactive species and elevated values of iron ions and free heme are antagonized by an overexpression of enzymes and proteins, contributing to the antioxidative defense and maintenance of redox homeostasis. Through these mechanisms, tumor cells can even survive additional stress caused by radio- and chemotherapy. Through the secretion of active agents from tumor cells, immune cells are suppressed in the tumor microenvironment and an enhanced formation of extracellular matrix components is induced. Different oxidant- and protease-based cytotoxic agents are involved in tumor-mediated immunosuppression, tumor growth, tumor cell invasion, and metastasis. Considering the special metabolic conditions in tumors, the main focus here was directed on the disturbed balance between the cytotoxic agents and protective mechanisms in late-stage tumors. This knowledge is mandatory for the implementation of novel anti-cancerous therapeutic approaches.

Targeting of RRM2 suppresses DNA damage response and activates apoptosis in atypical teratoid rhabdoid tumor

BACKGROUND

Atypical teratoid rhabdoid tumors (ATRT) is a rare but aggressive malignancy in the central nervous system, predominantly occurring in early childhood. Despite aggressive treatment, the prognosis of ATRT patients remains poor. RRM2, a subunit of ribonucleotide reductase, has been reported as a biomarker for aggressiveness and poor prognostic conditions in several cancers. However, little is known about the role of RRM2 in ATRT. Uncovering the role of RRM2 in ATRT will further promote the development of feasible strategies and effective drugs to treat ATRT.

METHODS

Expression of RRM2 was evaluated by molecular profiling analysis and was confirmed by IHC in both ATRT patients and PDX tissues. Follow-up in vitro studies used shRNA knockdown RRM2 in three different ATRT cells to elucidate the oncogenic role of RRM2. The efficacy of COH29, an RRM2 inhibitor, was assessed in vitro and in vivo. Western blot and RNA-sequencing were used to determine the mechanisms of RRM2 transcriptional activation in ATRT.

RESULTS

RRM2 was found to be significantly overexpressed in multiple independent ATRT clinical cohorts through comprehensive bioinformatics and clinical data analysis in this study. The expression level of RRM2 was strongly correlated with poor survival rates in patients. In addition, we employed shRNAs to silence RRM2, which led to significantly decrease in ATRT colony formation, cell proliferation, and migration. In vitro experiments showed that treatment with COH29 resulted in similar but more pronounced inhibitory effect. Therefore, ATRT orthotopic mouse model was utilized to validate this finding, and COH29 treatment showed significant tumor growth suppression and prolong overall survival. Moreover, we provide evidence that COH29 treatment led to genomic instability, suppressed homologous recombinant DNA damage repair, and subsequently induced ATRT cell death through apoptosis in ATRT cells.

CONCLUSIONS

Collectively, our study uncovers the oncogenic functions of RRM2 in ATRT cell lines, and highlights the therapeutic potential of targeting RRM2 in ATRT. The promising effect of COH29 on ATRT suggests its potential suitability for clinical trials as a novel therapeutic approach for ATRT.

A missense mutation in the suc22 gene encoding the small subunit of ribonucleotide reductase significantly sensitizes fission yeast to chronic treatment with hydroxyurea

Ribonucleotide reductase (RNR) is essential for the biosynthesis of dNTPs and a therapeutic target. We have identified a missense mutation in suc22 , which encodes the small subunit of RNR in fission yeast. The suc22-S239F mutation significantly sensitizes the cells to chronic but not acute treatment with the RNR inhibitor hydroxyurea. Preliminary data indicate that the drug sensitivity is likely due to decreased RNR activity. Since S239F is the first missense mutation reported for suc22 and the mutated residue is highly conserved, the results will be useful for future yeast genetic studies and potentially, the development of new therapeutics targeting RNR.

A Phase I Expansion Cohort Study Evaluating the Safety and Efficacy of the CHK1 Inhibitor LY2880070 with Low-dose Gemcitabine in Patients with Metastatic Pancreatic Adenocarcinoma

PURPOSE

Combining gemcitabine with CHK1 inhibition has shown promise in preclinical models of pancreatic ductal adenocarcinoma (PDAC). Here, we report the findings from a phase I expansion cohort study (NCT02632448) investigating low-dose gemcitabine combined with the CHK1 inhibitor LY2880070 in patients with previously treated advanced PDAC.

PATIENTS AND METHODS

Patients with metastatic PDAC were treated with gemcitabine intravenously at 100 mg/m2 on days 1, 8, and 15, and LY2880070 50 mg orally twice daily on days 2-6, 9-13, and 16-20 of each 21-day cycle. Pretreatment tumor biopsies were obtained from each patient for correlative studies and generation of organoid cultures for drug sensitivity testing and biomarker analyses.

RESULTS

Eleven patients with PDAC were enrolled in the expansion cohort between August 27, 2020 and July 30, 2021. Four patients (36%) experienced drug-related grade 3 adverse events. No objective radiologic responses were observed, and all patients discontinued the trial by 3.2 months. In contrast to the lack of efficacy observed in patients, organoid cultures derived from biopsies procured from two patients demonstrated strong sensitivity to the gemcitabine/LY2880070 combination and showed treatment-induced upregulation of replication stress and DNA damage biomarkers, including pKAP1, pRPA32, and γH2AX, as well as induction of replication fork instability.

CONCLUSIONS

No evidence of clinical activity was observed for combined low-dose gemcitabine and LY2880070 in this treatment-refractory PDAC cohort. However, the gemcitabine/LY2880070 combination showed in vitro efficacy, suggesting that drug sensitivity for this combination in organoid cultures may not predict clinical benefit in patients.

Identifying genes associated with resistance to KRAS G12C inhibitors via machine learning methods

BACKGROUND

Targeted therapy has revolutionized cancer treatment, greatly improving patient outcomes and quality of life. Lung cancer, specifically non-small cell lung cancer, is frequently driven by the G12C mutation at the KRAS locus. The development of KRAS inhibitors has been a breakthrough in the field of cancer research, given the crucial role of KRAS mutations in driving tumor growth and progression. However, over half of patients with cancer bypass inhibition show limited response to treatment. The mechanisms underlying tumor cell resistance to this treatment remain poorly understood.

METHODS

To address above gap in knowledge, we conducted a study aimed to elucidate the differences between tumor cells that respond positively to KRAS (G12C) inhibitor therapy and those that do not. Specifically, we analyzed single-cell gene expression profiles from KRAS G12C-mutant tumor cell models (H358, H2122, and SW1573) treated with KRAS G12C (ARS-1620) inhibitor, which contained 4297 cells that continued to proliferate under treatment and 3315 cells that became quiescent. Each cell was represented by the expression levels on 8687 genes. We then designed an innovative machine learning based framework, incorporating seven feature ranking algorithms and four classification algorithms to identify essential genes and establish quantitative rules.

RESULTS

Our analysis identified some top-ranked genes, including H2AFZ, CKS1B, TUBA1B, RRM2, and BIRC5, that are known to be associated with the progression of multiple cancers.

CONCLUSION

Above genes were relevant to tumor cell resistance to targeted therapy. This study provides important insights into the molecular mechanisms underlying tumor cell resistance to KRAS inhibitor treatment.

E2F8 exerts cancer-promoting effects by transcriptionally activating RRM2 and E2F8 knockdown synergizes with WEE1 inhibition in suppressing lung adenocarcinoma

Ribonucleotide reductase (RR) is a rate-limiting enzyme that facilitates DNA replication and repair by reducing nucleotide diphosphates (NDPs) to deoxyribonucleotide diphosphates (dNDPs) and is thereby crucial for cell proliferation and cancer development. The E2F family of transcription factors includes key regulators of gene expression involved in cell cycle control. In this study, E2F8 expression was significantly increased in most cancer tissues of lung adenocarcinoma (LUAD) patients and was correlated with the expression of RRM2 through database and clinical samples analysis. The protein expression of E2F8 and RRM2 were positively correlated with tumor-node-metastasis (TNM) pathological stage, and high expression of E2F8 and RRM2 predicted a low 5-year overall survival rate in LUAD patients. Overexpression and knockdown experiments showed that E2F8 was essential for LUAD cell proliferation, DNA synthesis, and cell cycle progression, which were RRM2-dependent. Reporter gene, ChIP-qPCR, and DNA pulldown-Western blot assays indicated that E2F8 activated the transcription of the RRM2 gene by directly binding with the RRM2 promoter in LUAD cells. Previous studies indicated that inhibition of WEE1 kinase can suppress the phosphorylation of CDK1/2 and promote the degradation of RRM2. We further showed here that the combination of E2F8 knockdown with MK-1775, an inhibitor of WEE1 being evaluated in clinical trials, synergistically suppressed proliferation and promoted apoptosis of LUAD cells in vitro and in vivo. Thus, this study reveals a novel role of E2F8 as a proto-oncogenic transcription activator by activating RRM2 expression in LUAD, and targeting both the transcription and degradation mechanisms of RRM2 could produce a synergistic inhibitory effect for LUAD treatment in addition to conventional inhibition of RR enzyme activity.

Ribonucleotide reductase as a therapeutic target for drug repurposing as anthelmintics

Visceral cestodiases, like echinococcoses and cysticercoses, are zoonoses of worldwide distribution and are responsible for public health problems in many countries, especially in underdeveloped regions. Current treatments have low efficiency and there are few drugs currently in use for chemotherapy, making the development of new anthelmintics an urgent matter. The nucleotide salvage pathways are the only ones available for nucleotide synthesis in cestodes and other parasitic helminths, and, here, we used in silico approaches to assess the potential of the enzymes in these pathways as targets for drug repurposing as anthelminthics. First, a genomic survey allowed to identify a repertoire of 28 enzymes of the purine and pyrimidine salvage pathways from the cestode Echinococcus granulosus sensu stricto. Regarding purines, the parasite relies on salvaging free bases rather than salvaging nucleosides. Pyrimidines, on the other hand, can be salvaged from both bases and nucleosides. Druggability of the parasite enzymes was assessed, as well as the availability of commercial inhibitors for them. Druggable enzymes were then ranked according to their potential for drug repurposing and the 17 most promising enzymes were selected for evolutionary analyses. The constructed phylogenetic trees allowed to assess the degree of conservation among ortholog enzymes from parasitic helminths and their mammalian hosts. Positive selection is absent in all assessed flatworm enzymes. A potential target enzyme for drug repurposing, ribonucleotide reductase (RNR), was selected for further assessment. RNR 3D-modelling showed structural similarities between the E. granulosus and the human orthologs suggesting that inhibitors of the human RNR should be effective against the E. granulosus enzyme. In line with that, E. granulosus protoscolices treated in vitro with the inhibitor hydroxyurea had their viability and DNA synthesis reduced. These results are consistent with nucleotide synthesis inhibition and confirm the potential of a nucleotide salvage inhibitors for repurposing as an anthelmintic.

Innovative lanthanide complexes: Shaping the future of cancer/ tumor chemotherapy

Developing new therapeutic and diagnostic metals and metal complexes is a stunning example of how inorganic chemistry is rapidly becoming an essential part of modern medicine. More study of bio-coordination chemistry is needed to improve the design of compounds with fewer harmful side effects. Metal-containing drugs are widely utilized in the treatment of cancer. Platinum complexes are effective against some cancers, but new coordination compounds are being created with improved pharmacological properties and a broader spectrum of anticancer action. The coordination complexes of the 15 lanthanides or rare earth elements in the periodic table are crucial for diagnosing and treating cancer. Understanding and treating cancer requires the detection of binding lanthanide (III) ions or complexes to DNA and breaking DNA by these complexes. Current advances in lanthanide-based coordination complexes as anticancer treatments over the past five years are discussed in this study.

RRM2 as a novel prognostic and therapeutic target of NF1-associated MPNST

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas that typically develop in the setting of neurofibromatosis type 1 (NF1) and cause significant morbidity. Conventional therapies are often ineffective for MPNSTs. Ribonucleotide reductase subunit M2 (RRM2) is involved in DNA synthesis and repair, and is overexpressed in multiple cancers. However, its role in NF1-associated MPNSTs remains unknown. Our objective was to determine the therapeutic and prognostic potential of RRM2 in NF1-associated MPNSTs.

METHODS

Identification of hub genes was performed by using NF1-associated MPNST microarray datasets. We detected RRM2 expression by immunochemical staining in an MPNST tissue microarray, and assessed the clinical and prognostic significance of RRM2 in an MPNST cohort. RRM2 knockdown and the RRM2 inhibitor Triapine were used to assess cell proliferation and apoptosis in NF1-associated MPNST cells in vitro and in vivo. The underlying mechanism of RRM2 in NF1-associated MPNST was revealed by transcriptome analysis.

RESULTS

RRM2 is a key hub gene and its expression is significantly elevated in NF1-associated MPNST. We revealed that high RRM2 expression accounted for a larger proportion of NF1-associated MPNSTs and confirmed the correlation of high RRM2 expression with poor overall survival. Knockdown of RRM2 inhibited NF1-associated MPNST cell proliferation and promoted apoptosis and S-phase arrest. The RRM2 inhibitor Triapine displayed dose-dependent inhibitory effects in vitro and induced significant tumor growth reduction in vivo in NF1-associated MPNST. Analysis of transcriptomic changes induced by RRM2 knockdown revealed suppression of the AKT-mTOR signaling pathway. Overexpression of RRM2 activates the AKT pathway to promote NF1-associated MPNST cell proliferation.

CONCLUSIONS

RRM2 expression is significantly elevated in NF1-associated MPNST and that high RRM2 expression correlates with poorer outcomes. RRM2 acts as an integral part in the promotion of NF1-associated MPNST cell proliferation via the AKT-mTOR signaling pathway. Inhibition of RRM2 may be a promising therapeutic strategy for NF1-associated MPNST.

USP12 promotes nonsmall cell lung cancer progression through deubiquitinating and stabilizing RRM2

RRM2 is the catalytic subunit of ribonucleotide reductase (RNR), which catalyzes de novo synthesis of deoxyribonucleotide triphosphates (dNTPs) and plays critical roles in cancer cell proliferation. RRM2 protein level is controlled by ubiquitination mediated protein degradation system; however, its deubiquitinase has not been identified yet. Here we showed that ubiquitin-specific peptidase 12 (USP12) directly interacts with and deubiquitinates RRM2 in non-small cell lung cancer (NSCLC) cells. Knockdown of USP12 causes DNA replication stress and retards tumor growth in vivo and in vitro. Meanwhile, USP12 protein levels were positively correlated to RRM2 protein levels in human NSCLC tissues. In addition, high expression of USP12 was associated with poor prognosis in NSCLC patients. Therefore, our study reveals that USP12 is a RRM2 regulator and targeting USP12 could be considered as a potential therapeutical strategy for NSCLC treatment.

Serum ribonucleotide reductase M2 is a potential biomarker for diagnosing and monitoring liver fibrosis in chronic hepatitis B patients

It is known that ribonucleotide reductase M2 (RRM2) could be induced by hepatitis B virus (HBV) via DNA damage response. However, whether RRM2 is a potential biomarker for diagnosing and monitoring liver fibrosis in chronic hepatitis B (CHB) patients is still unclear. In this study, CHB patients from GSE84044 (a transcriptome data from GEO data set) were downloaded and RRM2 was selected as a hub gene. Interestingly, a positive correlation was found between serum RRM2 and liver fibrosis stage. The similar results were found in CHB patients with normal alanine aminotransferase (ALT). Notably, RRM2 could effectively differentiate preliminary fibrosis from advanced fibrosis in CHB patients with/without normal ALT. In addition, RRM2 had a better performance in diagnosing liver fibrosis than two commonly used noninvasive methods (aspartate aminotransferase-to-platelet ratio index and fibrosis index based on the four factors), two classic fibrotic biomarkers (hyaluronic acid and type IV collagen) as well as Mac-2 binding protein glycosylation isomer, a known serum fibrosis marker. Moreover, CHB patients with high RRM2, who were associated with advanced fibrosis, had higher expressions of immune checkpoints. Overall, serum RRM2 may be a promising biomarker for diagnosing and monitoring liver fibrosis in CHB patients.

Hypoxanthine phosphoribosyl transferase 1 metabolizes temozolomide to activate AMPK for driving chemoresistance of glioblastomas

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.

Theoretical, in Vitro Antiproliferative, and in Silico Molecular Docking and Pharmacokinetics Studies of Heteroleptic Nickel(II) and Copper(II) Complexes of Thiosemicarbazone-Based Ligands and Pefloxacin

Twelve new heteroleptic nickel(II) and copper(II) complexes of the type [M(L1-6 )(Pfx)2 ] (1-12), where L1-6 =2-benzylidenehydrazinecarbothioamide (L1 ), 2-benzylidene-N-methylhydrazinecarbothioamide (L2 ), 2-benzylidene-N-phenylhydrazinecarbothioamide (L3 ), 2-(4-methylbenzylidene)hydrazinecarbothioamide (L4 ), 2-(4-methylbenzylidene)-N-methylhydrazinecarbothioamide (L5 ) and 2-(4-methylbenzylidene)-N-phenylhydrazinecarbothioamide (L6 ), Pfx=pefloxacin and M=Ni(II) or Cu(II) have been synthesised, and their structures were confirmed by different spectral techniques. The spectral data and density functional theory (DFT) calculations supported the bonding of pefloxacin drug molecule via one of the carboxylate oxygen atoms and the pyridone oxygen atom, and the thiosemicarbazone ligand via the imine nitrogen and the thione sulfur atoms with the metal(II) ion, forming distorted octahedral geometry. In vitro antiproliferative activity of the synthesized complexes was evaluated against three human breast cancer (T47D, estrogen negative (MDA-MB-231) and estrogen positive (MCF-7)) as well as non-tumorigenic human breast epithelial (MCF-10a) cell lines, which showed the higher activity for the copper(II) complexes. The interaction of the synthesized complexes with an oncogenic protein H-ras (121 p) was explored by in silico molecular docking studies. Further, in silico pharmacokinetics and ADMET parameters were also analysed to predict the drug-likeness as well as non-toxic and non-carcinogenic behavior, and safe oral administration of the complexes.

Patent highlights February-March 2023

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

Synergistic anticancer activity of combined ATR and ribonucleotide reductase inhibition in Ewing's sarcoma cells

PURPOSE

Ewing's sarcoma is a highly malignant childhood tumour whose outcome has hardly changed over the past two decades despite numerous attempts at chemotherapy intensification. It is therefore essential to identify new treatment options. The present study was conducted to explore the effectiveness of combined inhibition of two promising targets, ATR and ribonucleotide reductase (RNR), in Ewing's sarcoma cells.

METHODS

Effects of the ATR inhibitor VE821 in combination with the RNR inhibitors triapine and didox were assessed in three Ewing's sarcoma cell lines with different TP53 status (WE-68, SK-ES-1, A673) by flow cytometric analysis of cell death, mitochondrial depolarisation and cell cycle distribution as well as by caspase 3/7 activity determination, by immunoblotting and by real-time RT-PCR. Interactions between inhibitors were evaluated by combination index analysis.

RESULTS

Single ATR or RNR inhibitor treatment produced small to moderate effects, while their combined treatment produced strong synergistic ones. ATR and RNR inhibitors elicited synergistic cell death and cooperated in inducing mitochondrial depolarisation, caspase 3/7 activity and DNA fragmentation, evidencing an apoptotic form of cell death. All effects were independent of functional p53. In addition, VE821 in combination with triapine increased p53 level and induced p53 target gene expression (CDKN1A, BBC3) in p53 wild-type Ewing's sarcoma cells.

CONCLUSION

Our study reveals that combined targeting of ATR and RNR was effective against Ewing's sarcoma in vitro and thus rationalises an in vivo exploration into the potential of combining ATR and RNR inhibitors as a new strategy for the treatment of this challenging disease.

Inhibition of RRM2 radiosensitizes glioblastoma and uncovers synthetic lethality in combination with targeting CHK1

Glioblastoma (GBM) is an aggressive malignant primary brain tumor. Radioresistance largely contributes to poor clinical outcomes in GBM patients. We targeted ribonucleotide reductase subunit 2 (RRM2) with triapine to radiosensitize GBM. We found RRM2 is associated with increasing tumor grade, is overexpressed in GBM over lower grade gliomas and normal tissue, and is associated with worse survival. We found silencing or inhibition of RRM2 by siRNA or triapine sensitized GBM cells to ionizing radiation (IR) and delayed resolution of IR-induced γ-H2AX nuclear foci. In vivo, triapine and IR reduced tumor growth and increased mouse survival. Intriguingly, triapine led to RRM2 upregulation and CHK1 activation, suggesting a CHK1-dependent RRM2 upregulation following RRM2 inhibition. Consistently, silencing or inhibition of CHK1 with rabusertib abolished the triapine-induced RRM2 upregulation. Accordingly, combining rabusertib and triapine resulted in synthetic lethality in GBM cells. Collectively, our results suggest RRM2 is a promising therapeutic target for GBM, and targeting RRM2 with triapine sensitizes GBM cells to radiation and independently induces synthetic lethality of GBM cells with CHK1 inhibition. Our findings suggest combining triapine with radiation or rabusertib may improve therapeutic outcomes in GBM.