PCNA regulates primary metabolism by scaffolding metabolic enzymes

AOH1996 targets mitochondrial dynamics and metabolism in leukemic stem cells via mitochondrial PCNA inhibition

Cytoplasmic proliferating cell nuclear antigen (PCNA) is highly expressed in acute myeloid leukemia (AML) cells, supporting oxidative metabolism and leukemia stem cell (LSC) growth. We report on AOH1996 (AOH), an oral compound targeting cancer-associated PCNA, which shows significant antileukemic activity. AOH inhibited growth in AML cell lines and primary CD34 + CD38 - blasts (LSC-enriched) in vitro while sparing normal hematopoietic stem cells (HSCs). In vivo, AOH-treated mice demonstrated prolonged survival compared to controls (50 vs. 35 days; p < 0.0001) with reduced LSC burden, as shown in secondary transplants (42 vs. 30 days, p < 0.0001). Mechanistically, AOH disrupted mitochondrial PCNA's binding to the OPA1 protein, enhancing OPA1's interaction with its E3 ligase, MARCH5, which led to OPA1 degradation. This process reduced mitochondrial length, fatty acid oxidation (FAO), and oxidative phosphorylation (OXPHOS), thereby inhibiting LSC expansion. The addition of venetoclax (VEN), an FDA-approved Bcl-2 inhibitor, further enhanced AOH's effects, reducing mitochondrial length, FAO, and OXPHOS while improving survival in AML models. While VEN is approved for AML, AOH is under clinical investigation for solid tumors, and our findings support its broader therapeutic potential.

Exploring the Impact of Apelin and Reactive Oxygen Species on Autophagy and Cell Senescence in Pre-eclampsia

This research investigates the interplay between Reactive Oxygen Species (ROS) and Apelin (APLN) in regulating autophagy, with implications for placental cell senescence and apoptosis in pre-eclampsia (PE). We manipulated APLN expression using sgRNA to study its effects on ROS levels and subsequent cellular responses. Our findings reveal that APLN overexpression elevates ROS production, accelerating cellular senescence and apoptosis. In contrast, silencing APLN enhances autophagy, thereby diminishing cellular aging and apoptosis. These outcomes were confirmed in vitro and in vivo experiments, establishing a causative relationship between ROS-mediated APLN modulation and altered placental cell dynamics in PE. The results suggest potential therapeutic targets within the ROS and APLN pathways to alleviate detrimental changes in the placenta, offering new strategies for the clinical management of PE. This study emphasizes the crucial role of autophagy in placental health and sets the stage for future investigations into therapeutic interventions for pregnancy-related complications.

Peptides as innovative strategies to combat drug resistance in cancer therapy

Drug resistance is the leading cause of treatment failure in patients with cancer. Thus, innovative therapeutic strategies are required to overcome this critical challenge and improve patient outcomes. In this review, we examine the potential of peptide-based therapies to combat drug resistance in cancer. We highlight the unique strategies and mechanisms that can be explored by using peptides, including their ability to selectively target tumours, facilitate drug delivery into cancer cells, and inhibit key intracellular proteins that drive cancer progression and resistance. Peptides offer a promising approach to overcoming both intrinsic and adaptative cancer resistance against chemotherapy, targeted therapies, and biologics.

Multiple Myeloma Cells with Increased Proteasomal and ER Stress Are Hypersensitive to ATX-101, an Experimental Peptide Drug Targeting PCNA

Objectives: To examine the regulatory role of PCNA in MM, we have targeted PCNA with the experimental drug ATX-101 in three commercial cell lines (JJN3, RPMI 1660, AMO) and seven in-house patient-derived cell lines with a more primary cell-like phenotype (TK9, 10, 12, 13, 14, 16 and 18) and measured the systemic molecular effects. Methods: We have used a multi-omics untargeted approach, measuring the gene expression (transcriptomics), a subproteomics approach measuring mainly signalling proteins and proteins in complex with these (signallomics) and quantitative metabolomics. These results are supplemented with traditional analysis, e.g., viability, Western and ELISA analysis. Results: The sensitivity of the cell lines to ATX-101 varied, including between three cell lines derived from the same patient at different times of disease. A trend towards increased sensitivity to ATX-101 during disease progression was detected. Although with different sensitivities, ATX-101 treatment resulted in numerous changes in signalling and metabolite pools in all cell lines. Transcriptomics and signallomics analysis of the TK cell lines revealed that elevated endogenous expression of ribosomal genes, elevated proteasomal and endoplasmic reticulum (ER) stress and low endogenous levels of NAD+ and NADH were associated with ATX-101 hypersensitivity. ATX-101 treatment further enhanced the ER stress, reduced primary metabolism and reduced the levels of the redox pair GSH/GSSG in sensitive cells. Signallome analysis suggested that eleven proteins (TPD52, TNFRS17/BCMA, LILRB4/ILT3, TSG101, ZNRF2, UPF3B, FADS2, C11orf38/SMAP, CGREF1, GAA, COG4) were activated only in the sensitive MM cell lines (TK13, 14 and 16 and JJN3), and not in nine other cancer cell lines or in primary monocytes. These proteins may therefore be biomarkers of cells with activated proteasomal and ER stress even though the gene expression levels of these proteins were not elevated. Interestingly, carfilzomib-resistant cells were at least as sensitive to ATX-101 as the wild-type cells, suggesting both low cross-resistance between ATX-101 and proteasome inhibitors and elevated proteasomal stress in carfilzomib-resistant cells. Conclusions: Our multi-omics approach revealed a vital role of PCNA in regulation of proteasomal and ER stress in MM.

A triterpenoid (corosolic acid) ameliorated AOM-mediated aberrant crypt foci in rats: modulation of Bax/PCNA, antioxidant and inflammatory mechanisms

Corosolic acid (CA) is a well-known natural pentacyclic triterpene found in numerous therapeutic plants that can exhibit many bioactivities including anti-inflammatory and anti-tumor actions. The current investigation explores the chemoprotective roles of CA against azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) in rats. Thirty Sprague Dawley rats were grouped in 5 cages; Group A, normal control rats inoculated subcutaneously (sc) with two doses of normal saline and fed orally on 10% tween 20; Groups B-E received two doses (sc) of azoxymethane in two weeks and treated with either 10% tween 20 (group B) or two intraperitoneal injections of 35 mg/kg 5-fluorouracil each week for one month (group C), while group D and E treated with 30 and 60 mg/kg, respectively, for 2 months. The toxicity results showed lack of any behavioral abnormalities or mortality in rats ingested with up-to 500 mg/kg of CA. The present AOM induction caused a significant initiation of ACF characterized by an increased number, larger in size, and well-matured tissue clusters in cancer controls. AOM inoculation created a bizarrely elongated nucleus, and strained cells, and significantly lowered the submucosal glands in colon tissues of cancer controls compared to 5-FU or CA-treated rats. CA treatment led to significant suppression of ACF incidence, which could be mediated by its modulatory effects on the immunohistochemical proteins (pro-apoptotic (Bax) and reduced PCNA protein expressions in colon tissues). Moreover, CA-treated rats had improved oxidative stress-mediated cytotoxicity indicated by increased endogenous antioxidants (SOD and CAT) and reduced lipid peroxidation indicators (MDA). In addition, CA ingestion (30 and 60 mg/kg) suppressed the inflammatory cascades, indicated by decreased serum TNF-α and IL-6 cytokines and increased anti-inflammatory (IL-10) cytokines consequently preventing further tumor development. CA treatment maintained liver and kidney functions in rats exposed to AOM cytotoxicity. CA could be a viable alternative for the treatment of oxidative-related human disorders including ACF.

LncRNA MAGI2-AS3-Encoded Polypeptide Restrains the Proliferation and Migration of Breast Cancer Cells

Accumulating articles have reported the coding potential of long non-coding RNAs (lncRNAs). However, only a few lncRNAs-encoded peptides have been studied. Breast cancer (BRCA) progression-related gene modules were determined by weighted gene co-expression network analysis (WGCNA). Cell viability, proliferation, and migration capacities were assessed by Cell counting kit-8 (CCK8), 5-ethynyl-2'-deoxyuridine (EdU), and transwell assays. Immunofluorescence (IF) assay was implemented to observe protein expression. Co-immunoprecipitation (Co-IP) and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) were employed to analyze MAGI2 antisense RNA 3 (MAGI2-AS3)-ORF5-interacted proteins. WGCNA identified that MEpurple and MEblack modules were significantly negatively correlated with T stage in BRCA patients. MAGI2-AS3 was screened as one of the differentially expressed (DE) lncRNAs with translational potential in MEblack and MEpurple modules in BRCA. The data in The Cancer Genome Atlas (TCGA) uncovered that MAGI2-AS3 abundance was significantly decreased in invasive BRCA patients, and it had high diagnostic and prognostic values. MAGI2-AS3-ORF5 notably restrained BRCA cell viability, proliferation, and migration. Mechanically, MAGI2-AS3-ORF5 might affect the progression of BRCA cells by binding to extracellular matrix (ECM)-related proteins. MAGI2-AS3-ORF5 played an anti-tumor role by inhibiting BRCA cell viability, proliferation, and migration. MAGI2-AS3-ORF5 might modulate BRCA cell migration through ECM-associated proteins.

The bacterial DNA sliding clamp, β-clamp: structure, interactions, dynamics and drug discovery

DNA replication is a tightly coordinated event carried out by a multiprotein replication complex. An essential factor in the bacterial replication complex is the ring-shaped DNA sliding clamp, β-clamp, ensuring processive DNA replication and DNA repair through tethering of polymerases and DNA repair proteins to DNA. β -clamp is a hub protein with multiple interaction partners all binding through a conserved clamp binding sequence motif. Due to its central role as a DNA scaffold protein, β-clamp is an interesting target for antimicrobial drugs, yet little effort has been put into understanding the functional interactions of β-clamp. In this review, we scrutinize the β-clamp structure and dynamics, examine how its interactions with a plethora of binding partners are regulated through short linear binding motifs and discuss how contexts play into selection. We describe the dynamic process of clamp loading onto DNA and cover the recent advances in drug development targeting β-clamp. Despite decades of research in β-clamps and recent landmark structural insight, much remains undisclosed fostering an increased focus on this very central protein.

Excessive proliferating cell nuclear antigen attenuates endometrial adhesive capacity and decidualization in patients with recurrent implantation failure

STUDY QUESTION

Does the expression of proliferating cell nuclear antigen (PCNA) in the endometrium regulate endometrial receptivity in patients with recurrent implantation failure (RIF)?

SUMMARY ANSWER

A high abundance of PCNA attenuates endometrial adhesive capacity and decidualization in patients with RIF.

WHAT IS KNOWN ALREADY

Aberrant expression of PCNA has been discovered in multiple infertility-related disorders. However, the expression pattern and role of PCNA in the establishment of endometrial receptivity and endometrial decidualization in patients with RIF remain unclear.

STUDY DESIGN, SIZE, DURATION

We analysed the expression of PCNA in mid-secretory endometrial tissues from 24 patients with RIF and 24 healthy women. Additionally, PCNA expression levels were measured in proliferative and mid-secretory phase endometrial tissue samples from women with regular menstrual cycles and in decidual tissue samples taken from ten women during normal early pregnancy (n = 10 per phase for each group). The function and regulatory mechanisms of PCNA in endometrial adhesive capacity and endometrial decidualization were investigated using BeWo spheroids, Ishikawa cells, and human endometrial stromal cells (HESCs).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The expression of PCNA in mid-secretory endometrial tissues of patients with RIF and women with normal endometrium and in endometrial tissue at different stages of the menstrual cycle and in decidualized tissues was analysed by RT-qPCR, western blot, and immunohistochemistry staining (IHC). Furthermore, the number of BeWo spheroids directly attached to the Ishikawa cell monolayers, and the potential molecular mechanisms involved, were compared between cells overexpressing PCNA and a control group. Additionally, the effect and regulatory mechanisms of PCNA on the decidualization of HESCs in vitro were investigated.

MAIN RESULTS AND THE ROLE OF CHANCE

Our findings indicated that the abundance of PCNA was dramatically greater in mid-secretory endometrial tissues from patients with RIF than in those from women with healthy endometrium. The expression of PCNA increased in the proliferative phase of the menstrual cycle but decreased gradually in the mid-secretory phase and in decidual tissues. Interestingly, PCNA was expressed in both human endometrial epithelial cells (HEECs) and HESCs. In Ishikawa cells, PCNA overexpression dramatically reduced the endometrial adhesive capacity by inhibiting the expression of adhesion molecules (E-cadherin and integrin β3) and activating the FAK/paxillin signalling pathway. Furthermore, in HESCs, PCNA overexpression attenuated endometrial decidualization by activating the AKT/β-catenin signalling pathway and increasing tight junctions between cells by upregulating ZO-1 and occludin expression. In addition, PCNA-ELAVL1 interactions were confirmed by coimmunoprecipitation in decidualized HESCs.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The functional analysis of PCNA was limited by the number of human endometrial tissues. A larger sample size is required to further explore the potential roles of PCNA during embryo implantation. Moreover, the present results should be taken with caution, as only a few of the embryos that were transferred in RIF patients population underwent preimplantation genetic testing for embryonic chromosome aneuploidies (PGT-A), despite embryo ploidy testing being significant in the diagnosis of unexplained RIF.

WIDER IMPLICATIONS OF THESE FINDINGS

High PCNA expression attenuates endometrial adhesive capacity and decidualization in patients with RIF. These findings provide new insights into the potential mechanisms underlying the occurrence of implantation failure.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Natural Science Foundation of China (82101698), Shandong Provincial Natural Science Foundation (ZR2021MH012), and the Science and Technology Plan of Yantai (2023YD021 and 2022YD031). The authors have no conflicts of interest to disclose.

TRIAL REGISTRATION NUMBER

N/A.

Targeting proliferating cell nuclear antigen (PCNA) for cancer therapy

Proliferating cell nuclear antigen (PCNA) is an essential scaffold protein in many cellular processes. It is best known for its role as a DNA sliding clamp and processivity factor during DNA replication, which has been extensively reviewed by others. However, the importance of PCNA extends beyond its DNA-associated functions in DNA replication, chromatin remodelling, DNA repair and DNA damage tolerance (DDT), as new non-canonical roles of PCNA in the cytosol have recently been identified. These include roles in the regulation of immune evasion, apoptosis, metabolism, and cellular signalling. The diverse roles of PCNA are largely mediated by its myriad protein interactions, and its centrality to cellular processes makes PCNA a valid therapeutic anticancer target. PCNA is expressed in all cells and plays an essential role in normal cellular homeostasis; therefore, the main challenge in targeting PCNA is to selectively kill cancer cells while avoiding unacceptable toxicity to healthy cells. This chapter focuses on the stress-related roles of PCNA, and how targeting these PCNA roles can be exploited in cancer therapy.

G-CSF reshapes the cytosolic PCNA scaffold and modulates glycolysis in neutrophils

Cytosolic proliferating cell nuclear antigen (PCNA) is involved in neutrophil survival and function, in which it acts as a scaffold and associates with proteins involved in apoptosis, NADPH oxidase activation, cytoskeletal dynamics, and metabolism. While the PCNA interactome has been characterized in neutrophils under homeostatic conditions, less is known about neutrophil PCNA in pathophysiological contexts. Granulocyte colony-stimulating factor (G-CSF) is a cytokine produced in response to inflammatory stimuli that regulates many aspects of neutrophil biology. Here, we used isolated normal-density neutrophils from G-CSF-treated haemopoietic stem cell donors (GDs) as a model to understand the role of PCNA during inflammation. Proteomic analysis of the neutrophil cytosol revealed significant differences between GDs and healthy donors (HDs). PCNA was one of the most upregulated proteins in GDs, and the PCNA interactome was significantly different in GDs compared with HDs. Importantly, while PCNA associated with almost all enzymes involved in glycolysis in HDs, these associations were decreased in GDs. Functionally, neutrophils from GDs had a significant increase in glycolysis compared with HDs. Using p21 competitor peptides, we showed that PCNA negatively regulates neutrophil glycolysis in HDs but had no effect on GD neutrophils. These data demonstrate that G-CSF alters the PCNA scaffold, affecting interactions with key glycolytic enzymes, and thus regulates glycolysis, the main energy pathway utilized by neutrophils. By this selective control of glycolysis, PCNA can organize neutrophils functionality in parallel with other PCNA mechanisms of prolonged survival. PCNA may therefore be instrumental in the reprogramming that neutrophils undergo in inflammatory or tumoral settings.

Biological function, regulatory mechanism, and clinical application of mannose in cancer

Studies examining the regulatory roles and clinical applications of monosaccharides other than glucose in cancer have been neglected. Mannose, a common type of monosaccharide found in human body fluids and tissues, primarily functions in protein glycosylation rather than carbohydrate metabolism. Recent research has demonstrated direct anticancer effects of mannose in vitro and in vivo. Simply supplementing cell culture medium or drinking water with mannose achieved these effects. Moreover, mannose enhances the effectiveness of current cancer treatments including chemotherapy, radiotherapy, targeted therapy, and immune therapy. Besides the advancements in basic research on the anticancer effects of mannose, recent studies have reported its application as a biomarker for cancer or in the delivery of anticancer drugs using mannose-modified drug delivery systems. This review discusses the progress made in understanding the regulatory roles of mannose in cancer progression, the mechanisms underlying its anticancer effects, and its current application in cancer diagnosis and treatment.

Activation of multiple stress responses in Staphylococcus aureus substantially lowers the minimal inhibitory concentration when combining two novel antibiotic drug candidates

The past few decades have been plagued by an increasing number of infections caused by antibiotic resistant bacteria. To mitigate the rise in untreatable infections, we need new antibiotics with novel targets and drug combinations that reduce resistance development. The novel β-clamp targeting antimicrobial peptide BTP-001 was recently shown to have a strong additive effect in combination with the halogenated pyrrolopyrimidine JK-274. In this study, the molecular basis for this effect was examined by a comprehensive proteomic and metabolomic study of the individual and combined effects on Staphylococcus aureus. We found that JK-274 reduced activation of several TCA cycle enzymes, likely via increasing the cellular nitric oxide stress, and BTP-001 induced oxidative stress in addition to inhibiting replication, translation, and DNA repair processes. Analysis indicated that several proteins linked to stress were only activated in the combination and not in the single treatments. These results suggest that the strong additive effect is due to the activation of multiple stress responses that can only be triggered by the combined effect of the individual mechanisms. Importantly, the combination dose required to eradicate S. aureus was well tolerated and did not affect cell viability of immortalized human keratinocyte cells, suggesting a species-specific response. Our findings demonstrate the potential of JK-274 and BTP-001 as antibiotic drug candidates and warrant further studies.