Ribonucleotide Reductase M1 Research Articles

The Role of Ribonucleotide Reductase M2 in Lung Cancer Progression and Chemotherapy Resistance: A Bioinformatics Analysis and Review.

The Role of Ribonucleotide Reductase M2 in Lung Cancer Progression and Chemotherapy Resistance: A Bioinformatics Analysis and Review.

The potential of ribonucleotide reductase M2 as a novel prognostic maker and therapeutic target to inhibit medulloblastoma proliferation, migration, and invasiveness

AbstractThe crucial role of ribonucleotide reductase M2 (RRM2) enzyme in cancer occurrence and progression has been well‐established, but its specific function and significance in medulloblastoma (MB) remains largely unknown. First, we conducted a bioinformatics analysis of public genomic databases and observed highly expressed RRM2 in MB and an association of high RRM2 expression with adverse outcomes. In addition, by collecting clinical MB specimens for polymerase chain reaction (PCR), western blotting (WB), and immunohistochemistry (IHC), RRM2 was confirmed to be highly expressed in tumor tissues. Furthermore, immunohistochemical analysis linked adverse prognosis to high RRM2 expression. Moreover, knocking down RRM2 significantly inhibited MB cell proliferation, migration, and invasion in vitro. This report is the first to demonstrate the oncogenic role of RRM2 in MB, associated with adverse patient outcomes. Knocking down RRM2 contributes to weakened proliferating, migrating, and invading potentials of MB cells. RRM2 is expected to be a novel prognostic biomarker and therapeutic target for MB.

Identification and prognostic analysis of metabolic genes associated with TP53 mutation in multiple myeloma

ABSTRACT Background TP53 gene mutation is crucial in determining the prognosis of Multiple Myeloma (MM) patients. Understanding metabolic genes linked to TP53 mutation is vital for developing targeted therapies for these patients. Method We analyzed The Cancer Genome Atlas (TCGA) dataset to identify genes related to TP53 mutation and metabolism. Using univariate Cox regression and protein–protein interaction (PPI) analysis, we identified key genes. We categorized patients into high and low metabolism groups via non-negative matrix factorization (NMF) clustering, which led to the discovery of relevant differential genes. Integrating these with genes from the Gene Expression Omnibus (GEO) datasets and PPI interactions, we pinpointed crucial metabolic genes associated with TP53 mutation in MM. Additionally, we conducted prognostic analyses involving survival curves and receiver operating characteristic (ROC) charts. Results Our study reveals that the metabolic gene ribonucleotide reductase M2 (RRM2), linked to TP53 mutation, correlates positively with the International Staging System (ISS) stage in MM patients and is an independent prognostic risk factor. In the TCGA dataset, among the 767 patients, the 35 MM patients with TP53 mutation generally had poor survival outcomes. Specifically, the patients with both TP53 mutation and high RRM2 expression had a 2-year survival rate of only 38.87%, whereas those with normal TP53 function and low RRM2 expression had a 2-year survival rate of 86.31% (p < 0.001). Conclusion RRM2 significantly impacts MM prognosis and is associated with TP53 mutation, presenting itself as a potential therapeutic target and prognostic marker for MM.

Abstract 468: Associations of circulating miRNAs with pancreatic cancer risk differ by years between blood collection &amp; and cancer diagnosis

Abstract Pancreatic adenocarcinoma (PDAC) is one of the most fatal cancers and currently used biomarkers for PDAC diagnosis are not adequate for early detection. Therefore, new biomarkers for PDAC early detection are urgently needed. We conducted a large-scale study to prospectively evaluate the association of circulating miRNAs with PDAC risk. Specially, we aimed to examine whether the associations of miRNAs expression levels and changes of those levels from blood collection to cancer diagnosis (BCCD) with PDAC risk. We used pre-diagnostic plasma samples of 1307 PDAC cases from 5 cohort studies (290 from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, 395 from the Shanghai Women’s and Men’s Health Studies, 154 from the Southern Community Cohort Study, and 468 from the Multiethnic Cohort). Cancer free controls (n=1307) were selected and individually matched to index cases in each cohort. All miRNAs were measured by the NanoString nCounter Analysis System using the Human v3 miRNA Expression panel (798 miRNAs total). Data were pooled and quantile normalized prior to analysis. Associations of circulating miRNAs with PDAC risk were assessed by odds ratio per decile change in miRNA levels using conditional logistic regression. Fold-change of miRNA for cases versus controls by BCCD was analyzed via linear regression. Median time of BCCD was 7.13 years (range: 0.03-19.61 years). We first conducted the association analysis stratified by BCCD: &amp;lt; 5 years, 5-10 years, and &amp;gt;10 years. We found 20 miRNAs were significantly associated with PDAC risk in the &amp;lt;5 years after FDR correction. In the analysis of regressing fold-change of these 20 miRNAs on BCCD, we found the fold change of miR-155-5p was inversely associated with BCCD (β=-0.04, P&amp;lt;0.01), i.e., the case-control difference was larger when blood was drawn closer to PDAC diagnosis, suggesting its potential utility as disease biomarkers for early detection. Conversely, the fold-change of miR-93-5p (β=0.04, P=0.01), miR-223-3p (β=0.03, P=0.02), let-7i-5p (β=0.03, P&amp;lt;0.01), and miR-191-5p (β=0.05, P&amp;lt;0.01) were positively associated with BCCD, i.e., the case-control difference increased with an increasing the time interval of BCCD, indicating they are more likely biomarkers for PDAC risk. Ingenuity pathway analyses of these five significant miRNAs revealed that they were significantly enriched in ribonucleotide reductase signaling pathways at p&amp;lt;0.05. Notably, the silencing of ribonucleotide reductase M2 subunit suppresses tumorigenesis in pancreatic cancer by deactivating the PI3K/AKT/mTOR pathway, further supporting our findings. Findings of this large-scale multiethnic study suggest that changes in circulating levels of let-7i-5p, miR-155-5p, miR-93-5p, miR-191-5p, and miR-223-3p may help identify individuals at an elevated risk of developing PDAC, allowing for screening tests and close surveillance. Citation Format: Hui Cai, Veronica Wendy Setiawan, Xingyi Guo, Jie Wu, Rachael Z Stolzenberg-Solomon, Claire Zhu, Yu-Tang Gao, Jordan Berlin, Fei Ye, Qiuyin Cai, Wei Zheng, Xiao-ou Shu. Associations of circulating miRNAs with pancreatic cancer risk differ by years between blood collection &amp; and cancer diagnosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 468.

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.

Mechanism of Astragali Radix-Curcumae Rhizoma in treating gastric cancer based on network pharmacology and experimental verification

This study aims to investigate the mechanism of Astragali Radix-Curcumae Rhizoma(HQEZ) in the treatment of gastric cancer based on network pharmacology. Further, the SGC7901 cell model of gastric cancer was employed to validate the efficacy and key targets of the herb pair. Firstly, the CCK-8 assay was employed to evaluate the direct effect of HQEZ on the proliferation of gastric cancer SGC7901 cells. Then, network pharmacology methods were employed to investigate the active ingredients, key targets, and key signaling pathways involved in the treatment of gastric cancer with HQEZ. The results showed that HQEZ contained 18 potential active ingredients, such as quercetin, naringenin, and curcumin. The results of gene ontology(GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway enrichment suggested that the main targets of HQEZ in treating gastric cancer were involved in the regulation of protein serine/threonine kinase activity, activation of mitogen-activated protein kinase(MAPK) activity, cysteine-type endopeptidase activity, and negative regulation of protein serine/threonine kinase activity. The hypoxia-inducible factor-1(HIF-1) signaling pathway, ATP-binding cassette(ABC) transporters, cytochrome P450-mediated metabolism of xenobiotics, p53 signaling pathway, and cell apoptosis were key signaling pathways of HQEZ in treating gastric cancer. The cell experiments demonstrated that HQEZ significantly downregulated the expression of ATP-binding cassette subfamily B member 1(ABCB1), epidermal growth factor receptor(EGFR), phosphorylated serine/threonine kinase(p-AKT), hypoxia inducible factor 1 subunit alpha(HIF1A), B-cell lymphoma 2(BCL2), breast cancer susceptibility protein 1(BRCA1), DNA polymerase theta(POLH), ribonucleotide reductase M1(RRM1), and excision repair cross-complementation group 1(ERCC1), and upregulated the expression of tumor protein P53(TP53) and cysteinyl aspartate-specific proteinase(CAPS3). Finally, a multivariate COX regression model was adopted to study the relationship between gene expression and clinical information data of gastric cancer patients in the TCGA database, which demonstrated that the key targets of HQEZ were associated with the poor prognosis in gastric cancer patients. Further feature selection using the LASSO algorithm showed that EGFR, HIF1A, TP53, POLH, RRM1, and ERCC1 were closely associated with the survival of gastric can-cer patients. In conclusion, HQEZ regulates the expression of genes involved in DNA repair, survival, and apoptosis in gastric cancer cells via multiple targets and pathways, assisting the treatment of gastric cancer.

RRM2‑mediated Wnt/β‑catenin signaling pathway activation in lung adenocarcinoma: A potential prognostic biomarker.

The present study aimed to investigate the role and mechanism of action of ribonucleotide reductase M2 (RRM2) in lung adenocarcinoma and its potential as a therapeutic target. Data of patients with lung adenocarcinoma from The Cancer Genome Atlas database were collected and analyzed to evaluate the potential of RRM2 as a biomarker. The expression of RRM2 was evaluated in the A549 cell line and its cisplatin-resistant A549/DDP cell line derivative by western blot and reverse transcription-quantitative PCR. The study also investigated cell proliferation and the mechanism by which RRM2 controls cellular cisplatin resistance using CCK-8 and colony-formation assays. In addition, cell migration was assessed using Transwell assays, and the cell cycle and apoptosis were examined using flow cytometry. RRM2 was highly expressed in lung adenocarcinoma and was associated with the clinical TMN stage. Functional enrichment analysis showed that RRM2 was enriched in the cell cycle. Immune cell infiltration analysis identified 12 types of immune cell that exhibited differences between patients expressing different levels of RRM2. Cellular assays revealed higher levels of RRM2 expression in A549/DDP cells than A549 cells, and its expression was induced by cisplatin. RRM2 knockdown decreased cell proliferation and migration, accelerated apoptosis and caused cell cycle arrest in the S-phase, increasing the sensitivity of A549 and A549/DDP cells to cisplatin through the Wnt/β-catenin signaling pathway. Overexpression of β-catenin reduced the effects of RRM2 knockdown on A549 cells. Lung adenocarcinoma growth may be influenced by RRM2 through the Wnt/β-catenin signaling pathway, suggesting a potential pathway for cancer progression.

Dimethylarsinic acid induces bladder carcinogenesis via the amphiregulin pathway

Dimethylarsinic acid (DMA) is a major metabolite in the urine of humans and rats exposed to inorganic arsenicals, and is reported to induce rat bladder carcinogenesis. In the present study, we focused on early pathways of carcinogenesis triggered by DMA that were also active in tumors. RNA expression in the bladder urothelium of rats treated with 0 and 200 ppm DMA in the drinking water for 4 weeks and in bladder tumors of rats treated with 200 ppm DMA for 2 years was initially examined using microarray analysis and Ingenuity Pathway Analysis (IPA). Expression of 160 genes was altered in both the urothelium of rats treated for 4 weeks with DMA and in DMA-induced tumors. IPA associated 36 of these genes with liver tumor diseases. IPA identified the amphiregulin (Areg)-regulated pathway as a Top Regulator Effects Network. Therefore, we focused on Areg and 6 of its target genes: cyclin A2, centromere protein F, marker of proliferation Ki-67, protein regulator of cytokinesis 1, ribonucleotide reductase M2, and topoisomerase II alpha. We confirmed high mRNA expression of Areg and its 6 target genes in both the urothelium of rats treated for 4 weeks with DMA and in DMA-induced tumors. RNA interference of human amphiregulin (AREG) expression in human urinary bladder cell lines T24 and UMUC3 decreased expression of AREG and its 6 target genes and decreased cell proliferation. These data suggest that Areg has an important role in DMA-induced rat bladder carcinogenesis.

High Ribonucleotide Reductase M2 Expression as an Independent Prognostic Biomarker and Correlated with Immune Infiltrates in Live Hepatocellular Carcinoma

Hepatocellular carcinoma (LIHC) is a prevalent cancer worldwide. High expression of Ribonucleotide reductase M2 (RRM2), a gene expressed in various tumors including LIHC, has been associated with poor prognosis, yet its correlation with immune cell infiltration in LIHC remains unclear. We aimed to develop a prognosis model for patient prognosis analysis and immunotherapy using RRM2 expression data and corresponding clinical data collected from The Cancer Genome Atlas (TCGA) database. Patients were divided into high- and low-risk groups based on their median risk score. Our analysis revealed that high expression of RRM2 was associated with T-stage, pathological stage, histologic grade, AFP levels, and age. Further analysis showed that cell cycle checkpoints, B cell receptor, cell cycle, MHC class II antigen, cancer pathway, and TP53 were differentially enriched in the RRM2 high expression phenotype. Additionally, RRM2 correlated with the majority of immune cell infiltration levels and was positively correlated with Th2 cells and negatively correlated with neutrophil cells, DC, CD8 T cells, and NK cells. The levels of these immune cells were significantly different between the RRM2 high and low expression groups. Our study suggests that overexpression of RRM2 is associated with poor prognosis in LIHC and may represent a valuable prognostic biomarker for this cancer.

Hepatitis C Virus Down-Regulates the Expression of Ribonucleotide Reductases to Promote Its Replication.

Ribonucleotide reductases (RRs or RNRs) catalyze the reduction of the OH group on the 2nd carbon of ribose, reducing four ribonucleotides (NTPs) to the corresponding deoxyribonucleotides (dNTPs) to promote DNA synthesis. Large DNA viruses, such as herpesviruses and poxviruses, could benefit their replication through increasing dNTPs via expression of viral RRs. Little is known regarding the relationship between cellular RRs and RNA viruses. Mammalian RRs contain two subunits of ribonucleotide reductase M1 polypeptide (RRM1) and two subunits of ribonucleotide reductase M2 polypeptide (RRM2). In this study, expression of cellular RRMs, including RRM1 and RRM2, is found to be down-regulated in hepatitis C virus (HCV)-infected Huh7.5 cells and Huh7 cells with HCV subgenomic RNAs (HCVr). As expected, the NTP/dNTP ratio is elevated in HCVr cells. Compared with that of the control Huh7 cells with sh-scramble, the NTP/dNTP ratio of the RRM-knockdown cells is elevated. Knockdown of RRM1 or RRM2 increases HCV replication in HCV replicon cells. Moreover, inhibitors to RRMs, including Didox, Trimidox and hydroxyurea, enhance HCV replication. Among various HCV viral proteins, the NS5A and/or NS3/4A proteins suppress the expression of RRMs. When these are taken together, the results suggest that HCV down-regulates the expression of RRMs in cultured cells to promote its replication.

Ribonucleotide reductase subunit switching in hepatoblastoma drug response and relapse

Prognosis of children with high-risk hepatoblastoma (HB), the most common pediatric liver cancer, remains poor. In this study, we found ribonucleotide reductase (RNR) subunit M2 (RRM2) was one of the key genes supporting cell proliferation in high-risk HB. While standard chemotherapies could effectively suppress RRM2 in HB cells, they induced a significant upregulation of the other RNR M2 subunit, RRM2B. Computational analysis revealed distinct signaling networks RRM2 and RRM2B were involved in HB patient tumors, with RRM2 supporting cell proliferation and RRM2B participating heavily in stress response pathways. Indeed, RRM2B upregulation in chemotherapy-treated HB cells promoted cell survival and subsequent relapse, during which RRM2B was gradually replaced back by RRM2. Combining an RRM2 inhibitor with chemotherapy showed an effective delaying of HB tumor relapse in vivo. Overall, our study revealed the distinct roles of the two RNR M2 subunits and their dynamic switching during HB cell proliferation and stress response.

Targeting UBE2T Potentiates Gemcitabine Efficacy in Pancreatic Cancer by Regulating Pyrimidine Metabolism and Replication Stress

Although small patient subsets benefit from current targeted strategies or immunotherapy, gemcitabine remains the first-line drug for pancreatic cancer (PC) treatment. However, gemcitabine resistance is widespread and compromises long-term survival. Here, we identified ubiquitin-conjugating enzyme E2T (UBE2T) as a potential therapeutic target to combat gemcitabine resistance in PC. Proteomics and metabolomics were combined to examine the effect of UBE2T on pyrimidine metabolism remodeling. Spontaneous PC mice (LSL-KrasG12D/+, LSL-Trp53R172H/+, Pdx1-Cre; KPC) with Ube2t-conditional knockout, organoids, and large-scale clinical samples were used to determine the effect of UBE2T on gemcitabine efficacy. Organoids, patient-derived xenografts (PDX), and KPC mice were used to examine the efficacy of the combination of a UBE2T inhibitor and gemcitabine. Spontaneous PC mice with Ube2t deletion had a marked survival advantage after gemcitabine treatment, and UBE2T levels were positively correlated with gemcitabine resistance in clinical patients. Mechanistically, UBE2T catalyzes really interesting new gene 1 (RING1)-mediated ubiquitination of p53 and relieves the transcriptional repression of ribonucleotide reductase subunits M1 and M2, resulting in unrestrained pyrimidine biosynthesis and alleviation of replication stress. Additionally, high-throughput compound library screening using organoids identified pentagalloylglucose (PGG) as a potent UBE2T inhibitor and gemcitabine sensitizer. The combination of gemcitabine and PGG diminished tumor growth in PDX models and prolonged long-term survival in spontaneous PC mice. Collectively, UBE2T-mediated p53 degradation confers PC gemcitabine resistance by promoting pyrimidine biosynthesis and alleviating replication stress. This study offers an opportunity to improve PC survival by targeting UBE2T and develop a promising gemcitabine sensitizer in clinical translation setting.

Morphological predictors of the efficacy of mitotane therapy in adrenocortical cancer

Adrenocortical cancer (ACC) is an orphan malignant tumor of the adrenal cortex with a predominantly poor prognosis and an aggressive clinical course. Nowadays, mitotane is a non-alternative drug in the treatment of ACC. The search for prognostic parameters that determine the sensitivity of ACC to ongoing treatment is currently an urgent task. Expression levels of the large subunit of ribonucleotide reductase M1 (RRM1), cytochrome P450 2W1 (CYP2W1), and sterol- O-acyltransferase-1 (SOAT1) are considered as potential predictors of response to mitotane therapy. To assess the immunohistochemical expression of RRM1, CYP2W1 and SOAT1 in ACC as markers of clinical outcomes and response to the therapy with mitotane. The study included 62 patients older than 17 years of age with a diagnosis of ACC confirmed histologically and immunohistochemically. Mitotane therapy was initiated in 29 patients in the postoperative period, 33 patients were under dynamic observation without concomitant drug treatment. Antibodies to RRM1, CYP2W1, SOAT1 were used diluted in accordance with recommendations of firms-manufacturers for immunohistochemical detection. In the group of patients with low and moderate RRM1, CYP2W1 and SOAT1 immunoreactivity in the tumor and no antitumor therapy, a better DFS was noted (p=0.037, p=0.020 and p=0.001, respectively) compared to the group of patients receiving mitotane therapy at this level of marker expression. With high immunoreactivity of the markers, no statistically significant differences in DFS were found. Consistent with the findings in our study, low expression of RRM1, CYP2W1 and SOAT1 was associated with worse DFS with antitumor therapy. The results of the work indicate the need to assess the levels of immunoreactivity of these markers in patients with ACC before starting treatment with mitotane in order to predict the efficiency of therapy.

Screening of traditional Chinese medicine monomers as ribonucleotide reductase M2 inhibitors for tumor treatment.

Ribonucleotide reductase (RR) is a key enzyme in tumor proliferation, especially its subunit-RRM2. Although there are multiple therapeutics for tumors, they all have certain limitations. Given their advantages, traditional Chinese medicine (TCM) monomers have become an important source of anti-tumor drugs. Therefore, screening and analysis of TCM monomers with RRM2 inhibition can provide a reference for further anti-tumor drug development. To screen and analyze potential anti-tumor TCM monomers with a good binding capacity to RRM2. The Gene Expression Profiling Interactive Analysis database was used to analyze the level of RRM2 gene expression in normal and tumor tissues as well as RRM2's effect on the overall survival rate of tumor patients. TCM monomers that potentially act on RRM2 were screened via literature mining. Using AutoDock software, the screened monomers were docked with the RRM2 protein. The expression of RRM2 mRNA in multiple tumor tissues was significantly higher than that in normal tissues, and it was negatively correlated with the overall survival rate of patients with the majority of tumor types. Through literature mining, we discovered that berberine, ursolic acid, gambogic acid, cinobufagin, quercetin, daphnetin, and osalmide have inhibitory effects on RRM2. The results of molecular docking identified that the above TCM monomers have a strong binding capacity with RRM2 protein, which mainly interacted through hydrogen bonds and hydrophobic force. The main binding sites were Arg330, Tyr323, Ser263, and Met350. RRM2 is an important tumor therapeutic target. The TCM monomers screened have a good binding capacity with the RRM2 protein.

Identification of Novel Ribonucleotide Reductase Inhibitors for Therapeutic Application in Bile Tract Cancer: An Advanced Pharmacoinformatics Study

Biliary tract cancer (BTC) is constituted by a heterogeneous group of malignant tumors that may develop in the biliary tract, and it is the second most common liver cancer. Human ribonucleotide reductase M1 (hRRM1) has already been proven to be a potential BTC target. In the current study, a de novo design approach was used to generate novel and effective chemical therapeutics for BTC. A set of comprehensive pharmacoinformatics approaches was implemented and, finally, seventeen potential molecules were found to be effective for the modulation of hRRM1 activity. Molecular docking, negative image-based ShaEP scoring, absolute binding free energy, in silico pharmacokinetics, and toxicity assessments corroborated the potentiality of the selected molecules. Almost all molecules showed higher affinity in comparison to gemcitabine and naphthyl salicylic acyl hydrazone (NSAH). On binding interaction analysis, a number of critical amino acids was found to hold the molecules at the active site cavity. The molecular dynamics (MD) simulation study also indicated the stability between protein and ligands. High negative MM-GBSA (molecular mechanics generalized Born and surface area) binding free energy indicated the potentiality of the molecules. Therefore, the proposed molecules might have the potential to be effective therapeutics for the management of BTC.

Platycodon D-induced A549 Cell Apoptosis through RRM1-Regulated p53/VEGF/ MMP2 Pathway.

Lung cancer is one of the leading causes of cancer-related deaths worldwide. Platycodin D (PD), a major pharmacological constituent from the Chinese medicinal herb named Platycodonis Radix, has shown potent anti-tumor activity. Also, it is reported that PD could inhibit cellular growth in the non-small-cell lung carcinoma (NSCLC) A549 cell line. However, the underlying mechanism is not fully clarified. Cell proliferation was measured by MTT assay. Annexin V and propidium iodide (PI) assay were employed to study the apoptosis effects of PD on A549 cells. Western blot analysis was used to evaluate protein expression. Also, we used a siRNA against p53, as well as a plasmid-based RRM1 over-expression to investigate their functions. It is demonstrated that PD inhibited A549 cell proliferation in a dose- and time-dependent manner. Further investigations showed that PD induced cell apoptosis, which was supported by dose-dependent and time-dependent caspase-3 activation and p53/VEGF/MMP2 pathway regulation. Also, PD demonstrated the inhibition effect of ribonucleotide reductase M1 (RRM1), whose role in various tumors is contradictory. Remarkably, in this work, RRM1 overexpression in A549 cells could have a negative impact on the regulation of the p53/VEGF/MMP2 pathway induced by PD treatment. Note that RRM1 overexpression also attenuated cell apoptosis and inhibition of cell proliferation of A549 treated with PD. The results suggested that PD could inhibit A549 cell proliferation and induce cell apoptosis by regulating p53/VEGF/MMP2 pathway, in which RRM1 plays an important role directly.

RRM2 regulates osteogenesis of mouse embryo fibroblasts via the Wnt/β‑catenin signaling pathway.

Osteoporosis is a widespread bone metabolic disease characterized by reduced bone mass and bone microstructure deterioration. Ribonucleotide reductase M2 (RRM2) is a key enzyme in DNA synthesis and repair. The present study investigated the effect of RRM2 on osteogenesis of mouse embryo fibroblasts (MEFs) and its molecular mechanism. Bioinformatics analysis revealed that RRM2 expression was increased during osteogenesis of MEFs triggered by bone morphogenetic protein 9. Subsequently, MEFs were used as a mesenchymal stem cell model and osteogenic inducing medium was used to induce osteogenic differentiation. RRM2 protein expression was measured by western blotting during osteogenic differentiation induction of MEFs. RRM2 levels in MEFs were upregulated and downregulated by RRM2-overexpressing recombinant adenovirus and small interfering RNA-RRM2, respectively. Bone formation markers (RUNX family transcription factor 2, osterix, distal-less homeobox 5, collagen type I α1 chain, osteopontin and osteocalcin) were detected by reverse transcription-quantitative (RT-q) PCR and alkaline phosphatase (ALP) and Alizarin Red S staining were examined. The protein expression levels of β-catenin and the ratio of phosphorylated (p-)GSK-3β to GSK-3β were detected by western blotting and the RNA expression of downstream related target genes (β-catenin, axis inhibition protein 2 (AXIN2), transcription factor 7 like 2, lymphoid enhancer binding factor 1, c-MYC and Cyclin D1) in the Wnt/β-catenin signaling pathway was measured by RT-qPCR. RRM2 protein expression increased as the osteogenic differentiation induction period was extended. RRM2 overexpression increased osteogenic marker RNA expression, ALP activity, bone mineralization, the protein expression levels of β-catenin, the ratio of p-GSK-3β to GSK-3β and the RNA expression of downstream related target genes in the Wnt/β-catenin signaling pathway, whereas RRM2 knockdown had the opposite effect. The findings of the present study revealed that RRM2 overexpression enhanced osteogenic differentiation, while RRM2 knockdown reduced osteogenic differentiation. RRM2 may regulate osteogenic differentiation of MEFs via the canonical Wnt/β-catenin signaling pathway, providing a possible therapeutic target for osteoporosis.

Abstract 3963: Ribonucleotide reductase M2 subunit switching in hepatoblastoma drug resistance and relapse

Abstract Background and Rationale: Hepatoblastoma is the most common primary liver cancer in infants and young children. Despite being a very rare cancer that accounts for only 0.5-2% if all childhood cancer cases, HB has the largest increase in incidence among childhood cancers in the United States and worldwide. The five-year survival rate of children with the aggressive forms of HB, including those that have developed metastatic or recurrent diseases, is less than 40% due to the lack of effective treatment. We aim to identify targetable mechanisms underlying the progression and drug resistance of high-risk HB. Results: Our recent work on HB mouse and organoid models, patient-derived xenografts (PDX) and primary patient samples revealed a significant upregulation of ribonucleotide reductase (RNR) subunit M2 (RRM2) in high-risk HB. RNR is the sole enzymatic complex in mammal cells that converts ribonucleotides to deoxyribonucleotides and plays a critical role in regulating cell division and DNA repair. We found standard chemotherapy agents as well as two RRM2 inhibitors, triapine and MK1775, were capable of reducing RRM2 expression effectively in vitro. However, we found a significant induction of another RNR subunit M2B (RRM2B) in treated cells in corresponding to RRM2 reduction. While no changes in drug response were noticed in RRM2B knockout (KO) HB cells. RRM2B levels in HB cells showed a strong impact on cells’ ability to recover after chemotherapy. RRM2BOE HB cells showed a significant increase in their colony formation potential after chemotherapy where RRM2BKO cells formed much fewer colonies after treatment compared to the control cells. Interestingly, we noticed a reversed subunit switch from RRM2B to RRM2 during the recovery period when cell proliferation was restored. RRM2, indeed, had a much higher enzymatic activity in converting ribonucleotides to deoxyribonucleotides than RRM2B and promoted cell growth much more efficiently than RRM2B when both were overexpressed in HB cells. Finally, combining the RRM2 inhibitor MK1775 with standard chemotherapy in HB PDX models, although showing no additional benefit in reducing tumor size, significantly delayed tumor relapse after drug withdrawal. Conclusion: In this study, we demonstrated an intriguing switching between two RNR subunits, RRM2 and RRM2B in HB cells undergoing drug treatment and during their recovery afterwards. Our data suggest that RRM2 supports HB growth while its switching to RRM2B is critical to tumor cell survival under drug treatment. When tumor relapses, there is a reversed subunit switch from RRM2B to RRM2 to supports the recurrent growth of the tumor, which can serve as a potential therapeutic target in preventing HB relapse. Citation Format: Anthony Ray Brown, Emilie Indersie, Shaina Porter, Baranda Hansen, Li Fan, Liyuan Li, Cheng Tian, Haiyan Tan, Shondra Miller, Junmin Peng, Stefano Cairo, Liqin Zhu. Ribonucleotide reductase M2 subunit switching in hepatoblastoma drug resistance and relapse [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3963.

RRM2 Alleviates Doxorubicin-Induced Cardiotoxicity through the AKT/mTOR Signaling Pathway.

Doxorubicin (DOX) is an effective chemotherapeutic agent that plays an unparalleled role in cancer treatment. However, its serious dose-dependent cardiotoxicity, which eventually contributes to irreversible heart failure, has greatly limited the widespread clinical application of DOX. A previous study has demonstrated that the ribonucleotide reductase M2 subunit (RRM2) exerts salutary effects on promoting proliferation and inhibiting apoptosis and autophagy. However, the specific function of RRM2 in DOX-induced cardiotoxicity is yet to be determined. This study aimed to elucidate the role and potential mechanism of RRM2 on DOX-induced cardiotoxicity by investigating neonatal primary cardiomyocytes and mice treated with DOX. Subsequently, the results indicated that RRM2 expression was significantly reduced in mice hearts and primary cardiomyocytes. Apoptosis and autophagy-related proteins, such as cleaved-Caspase3 (C-Caspase3), LC3B, and beclin1, were distinctly upregulated. Additionally, RRM2 deficiency led to increased autophagy and apoptosis in cells. RRM2 overexpression, on the contrary, alleviated DOX-induced cardiotoxicity in vivo and in vitro. Consistently, DIDOX, an inhibitor of RRM2, attenuated the protective effect of RRM2. Mechanistically, we found that AKT/mTOR inhibitors could reverse the function of RRM2 overexpression on DOX-induced autophagy and apoptosis, which means that RRM2 could have regulated DOX-induced cardiotoxicity through the AKT/mTOR signaling pathway. In conclusion, our experiment established that RRM2 could be a potential treatment in reversing DOX-induced cardiac dysfunction.

RRM2 Improves Cardiomyocyte Proliferation after Myocardial Ischemia Reperfusion Injury through the Hippo-YAP Pathway.

Objective Ribonucleotide reductase M2 (RRM2) as an enzyme that catalyzes the deoxyreduction of nucleosides to deoxyribonucleoside triphosphate (dNTP) has been extensively studied, and it plays a crucial role in regulating cell proliferation. However, its role in ischemia-reperfusion injury (I/RI) is still unclear. Methods SD rats were used as the research object to detect the expression of RRM2 in the myocardium by constructing an I/RI model. At the same time, primary SD neonatal rat cardiomyocytes were extracted, and hypoxia/reoxygenation (H/R) treatment simulated the I/RI model. Using transfection technology to overexpress RRM2 in cardiomyocytes, quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) was used to detect the expression of RRM2, Cell Counting Kit-8 (CCK-8) assay was used to detect cell viability, and immunofluorescence staining was used to detect Ki67 and EdU-positive cells. Western blot (WB) technology was used to detect YAP and its phosphorylation expression. Results qRT-PCR results indicated that the expression of RRM2 was inhibited in the model group, and cardiomyocytes overexpressing RRM2 can obviously promote the proliferation of primary cardiomyocytes and improve the damage of cardiac structure and function caused by I/R. At the same time, RRM2 can promote the increase of YAP protein expression and the increase of Cyclin D1 mRNA expression. Conclusion RRM2 expression was downregulated in myocardial tissue with I/R. After overexpression of RRM2, cardiomyocyte proliferation was upregulated and the Hippo-YAP signaling pathway was activated.