BI 2536, a potent and selective inhibitor of polo-like kinase 1, inhibits tumor growth in vivo

Balancing Plk1 activity levels: The secret of synchrony between the cell and the centrosome cycle

The accuracy of cell division requires precise regulation of the cellular machinery governing DNA/genome duplication, ensuring its equal distribution among the daughter cells. The control of the centrosome cycle is crucial for the formation of a bipolar spindle, ensuring error-free segregation of the genome. The cell and centrosome cycles operate in close synchrony along similar principles. Both require a single duplication round in every cell cycle, and both are controlled by the activity of key protein kinases. Nevertheless, our comprehension of the precise cellular mechanisms and critical regulators synchronizing these two cycles remains poorly defined. Here, we present our hypothesis that the spatiotemporal regulation of a dynamic equilibrium of mitotic kinases activities forms a molecular clock that governs the synchronous progression of both the cell and the centrosome cycles.

Progress with polo-like kinase (PLK) inhibitors: a patent review (2018-present)

INTRODUCTION

Polo-like kinases (PLKs) have five isoforms, all of which play crucial roles in cell cycle and cell proliferation, offering opportunities for drug design and treatment of cancers and other related diseases. Notably, PLK1 and PLK4 have been extensively investigated as cancer drug targets. One distinctive feature of PLKs is the presence of a unique polo-box domain (PBD), which regulates kinase activity and subcellular localization. This provides possibilities for specifically targeting PLKs.

AREA COVERED

This article provides an overview of the roles of PLKs in various cancers and related diseases, as well as the drug development involving PLKs, with a particular focus on PLK1 and PLK4. It summarizes the PLK1 and PLK4 inhibitors that have been disclosed in patents or literature (from 2018 - present), which were sourced from SciFinder and WIPO database.

EXPERT OPINION

After two decades of drug development on PLKs, several drugs progressed into clinical trials for the treatment of many cancers; however, none of them has been approved yet. Further elucidating the mechanisms of PLKs and identifying and developing highly selective ATP-competitive inhibitors, highly potent drug-like PBD inhibitors, degraders, etc. may provide new opportunities for cancer therapy and the treatment for several nononcologic diseases. PLKs inhibition-based combination therapies can be another helpful strategy.

Affinity enhancement of polo-like kinase 1 polo box domain-binding ligands by a bivalent approach using a covalent kinase-binding component

The polo-like kinase 1 (Plk1) is an important cell cycle regulator that is recognized as a target molecule for development of anti-cancer agents. Plk1 consists of a catalytic kinase domain (KD) and a polo-box domain (PBD), which engages in protein-protein interactions (PPIs) essential to proper Plk1 function. Recently, we developed extremely high-affinity PBD-binding inhibitors based on a bivalent approach using the Plk1 KD-binding inhibitor, BI2536, and a PBD-binding peptide. Certain of the resulting bivalent constructs exhibited more than 100-fold Plk1 affinity enhancement relative to the best monovalent PBD-binding ligands. Herein, we report an extensive investigation of bivalent ligands that utilize the non-selective kinase inhibitor Wortmannin as a Plk1 KD-binding component. We found that bivalent ligands incorporating Wortmannin demonstrated affinity enhancements that could be similar to what we had obtained with BI2536 and that they could tightly bind to the protein. This suggests that these tight binding ligands might be useful for structural analysis of full-length Plk1.

PLK-1 regulates MEX-1 polarization in the C. elegans zygote

The one-cell C. elegans embryo undergoes an asymmetric cell division during which germline factors such as the RNA-binding proteins POS-1 and MEX-1 segregate to the posterior cytoplasm, leading to their asymmetric inheritance to the posterior germline daughter cell. Previous studies found that the RNA-binding protein MEX-5 recruits polo-like kinase PLK-1 to the anterior cytoplasm where PLK-1 inhibits the retention of its substrate POS-1, leading to POS-1 segregation to the posterior. In this study, we tested whether PLK-1 similarly regulates MEX-1 polarization. We find that both the retention of MEX-1 in the anterior and the segregation of MEX-1 to the posterior depend on PLK kinase activity and on the interaction between MEX-5 and PLK-1. Human PLK1 directly phosphorylates recombinant MEX-1 on 9 predicted PLK-1 sites in vitro, four of which were identified in previous phosphoproteomic analysis of C. elegans embryos. The introduction of alanine substitutions at these four PLK-1 phosphorylation sites (MEX-1(4A)) significantly weakened the inhibition of MEX-1 retention in the anterior, thereby weakening MEX-1 segregation to the posterior. In contrast, mutation of a predicted CDK1 phosphorylation site had no effect on MEX-1 retention or on MEX-1 segregation. MEX-1(4A) mutants are viable and fertile but display significant sterility and fecundity defects at elevated temperatures. Taken together with our previous findings, these findings suggest PLK-1 phosphorylation drives both MEX-1 and POS-1 polarization during the asymmetric division of the zygote.

Research Advances of Lipid Nanoparticles in the Treatment of Colorectal Cancer

Colorectal cancer (CRC) is a common type of gastrointestinal tract (GIT) cancer and poses an enormous threat to human health. Current strategies for metastatic colorectal cancer (mCRC) therapy primarily focus on chemotherapy, targeted therapy, immunotherapy, and radiotherapy; however, their adverse reactions and drug resistance limit their clinical application. Advances in nanotechnology have rendered lipid nanoparticles (LNPs) a promising nanomaterial-based drug delivery system for CRC therapy. LNPs can adapt to the biological characteristics of CRC by modifying their formulation, enabling the selective delivery of drugs to cancer tissues. They overcome the limitations of traditional therapies, such as poor water solubility, nonspecific biodistribution, and limited bioavailability. Herein, we review the composition and targeting strategies of LNPs for CRC therapy. Subsequently, the applications of these nanoparticles in CRC treatment including drug delivery, thermal therapy, and nucleic acid-based gene therapy are summarized with examples provided. The last section provides a glimpse into the advantages, current limitations, and prospects of LNPs in the treatment of CRC.

PLK1 inhibition leads to mitotic arrest and triggers apoptosis in cholangiocarcinoma cells

Cholangiocarcinoma (CCA) is a lethal cancer originating from the epithelial cells within the bile duct and ranks as the second most prevalent form of liver cancer in Thailand. Polo-like kinase 1 (PLK1), a protein serine/threonine kinase, regulates a number of steps in cell mitosis and is upregulated in several types of cancer, including CCA. Our previous study identified PLK1 as a biomarker of the C1 subtype, correlating with poor prognosis in intrahepatic CCA. The present study aimed to examine the effect of PLK1 inhibition on CCA cells. Different CCA cell lines developed from Thai patients, HuCCA1, KKU055, KKU100 and KKU213A, were treated with two PLK1 inhibitors, BI2536 and BI6727, and were transfected with small interfering RNA, followed by analysis of cell proliferation, cell cycle distribution and cell apoptosis. It was discovered that BI2536 and BI6727 inhibited cell proliferation and caused G2/M-phase arrest in CCA cells. Furthermore, the number of total apoptotic cells was increased in PLK1 inhibitor-treated CCA cells. The expression levels of mitotic proteins, aurora kinase A, phosphorylated PLK1 (T210) and cyclin B1, were augmented in PLK1-inhibited CCA cells. Additionally, inhibition of PLK1 led to increased DNA damage, as determined by the upregulated levels of γH2AX and increased cleavage of poly (ADP-ribose) polymerase, an apoptotic marker. These results suggested that inhibiting PLK1 prolonged mitotic arrest and subsequently triggered cell apoptosis. Validation of the antiproliferative effects of PLK1 inhibition was accomplished through silencing of the PLK1 gene. In conclusion, targeting PLK1 provided promising results for further study as a potential candidate for targeted therapy in CCA.

Cell cycle machinery in oncology: A comprehensive review of therapeutic targets

The cell cycle is tightly regulated to ensure controlled cell proliferation. Dysregulation of the cell cycle machinery is a hallmark of cancer that leads to unchecked growth. This review comprehensively analyzes key molecular regulators of the cell cycle and how they contribute to carcinogenesis when mutated or overexpressed. It focuses on cyclins, cyclin-dependent kinases (CDKs), CDK inhibitors, checkpoint kinases, and mitotic regulators as therapeutic targets. Promising strategies include CDK4/6 inhibitors like palbociclib, ribociclib, and abemaciclib for breast cancer treatment. Other possible targets include the anaphase-promoting complex/cyclosome (APC/C), Skp2, p21, and aurora kinase inhibitors. However, challenges with resistance have limited clinical successes so far. Future efforts should focus on combinatorial therapies, next-generation inhibitors, and biomarkers for patient selection. Targeting the cell cycle holds promise but further optimization is necessary to fully exploit it as an anti-cancer strategy across diverse malignancies.

Drug screening in human physiologic medium identifies uric acid as an inhibitor of rigosertib efficacy

The nonphysiological nutrient levels found in traditional culture media have been shown to affect numerous aspects of cancer cell physiology, including how cells respond to certain therapeutic agents. Here, we comprehensively evaluated how physiological nutrient levels affect therapeutic response by performing drug screening in human plasma-like medium. We observed dramatic nutrient-dependent changes in sensitivity to a variety of FDA-approved and clinically trialed compounds, including rigosertib, an experimental cancer therapeutic that recently failed in phase III clinical trials. Mechanistically, we found that the ability of rigosertib to destabilize microtubules is strongly inhibited by the purine metabolism end product uric acid, which is uniquely abundant in humans relative to traditional in vitro and in vivo cancer models. These results demonstrate the broad and dramatic effects nutrient levels can have on drug response and how incorporation of human-specific physiological nutrient medium might help identify compounds whose efficacy could be influenced in humans.

Thinking Outside the Box: Indirect Myc Modulation in Canine B-Cell Lymphoma

B-cell lymphomas (BCL) is the most frequent hematological cancer in dogs. Treatment typically consists of chemotherapy, with CHOP-based protocols. However, outcome remains generally poor, urging the exploration of new therapeutic strategies with a targeted approach. Myc transcription factor plays a crucial role in regulating cellular processes, and its dysregulation is implicated in numerous human and canine malignancies, including canine BCL (cBCL). This study aims to evaluate the efficacy of indirectly inhibiting Myc in cBCL using BI2536 and MZ1 compounds in two in vitro models (CLBL-1 and KLR-1201). Both BI2536 and MZ1, alone and combined, affected cell viability in a significant concentration- and time-dependent manner. Western Blot revealed an upregulation of PLK1 expression in both cell lines upon treatment with BI2536, in association with a reduction in c-Myc protein levels. Conversely, MZ1 led to a decrease in its primary target, BRD4, along with a reduction in c-Myc. Furthermore, BI2536, both alone and in combination with MZ1, induced larger transcriptomic changes in cells compared to MZ1 alone, primarily affecting MYC target genes and genes involved in cell cycle regulation. These data underscore the potential role of Myc as therapeutic target in cBCL, providing a novel approach to indirectly modulate this molecule.

Temporally distinct roles of Aurora A in polarization of the C. elegans zygote

During asymmetric cell division, cell polarity is coordinated with the cell cycle to allow proper inheritance of cell fate determinants and the generation of cellular diversity. In the Caenorhabditis elegans zygote, polarity is governed by evolutionarily conserved Partitioning-defective (PAR) proteins that segregate to opposing cortical domains to specify asymmetric cell fates. Timely establishment of PAR domains requires a cell cycle kinase, Aurora A (AIR-1 in C. elegans). Aurora A depletion by RNAi causes a spectrum of phenotypes including reversed polarity, excess posterior domains and no posterior domain. How depletion of a single kinase can cause seemingly opposite phenotypes remains obscure. Using an auxin-inducible degradation system and drug treatments, we found that AIR-1 regulates polarity differently at different times of the cell cycle. During meiosis I, AIR-1 acts to prevent later formation of bipolar domains, whereas in meiosis II, AIR-1 is necessary to recruit PAR-2 onto the membrane. Together, these data clarify the origin of multiple polarization phenotypes in RNAi experiments and reveal multiple roles of AIR-1 in coordinating PAR protein localization with cell cycle progression.

Centrosomes and associated proteins in pathogenesis and treatment of breast cancer

Breast cancer is the most prevalent malignancy among women worldwide. Despite significant advances in treatment, it remains one of the leading causes of female mortality. The inability to effectively treat advanced and/or treatment-resistant breast cancer demonstrates the need to develop novel treatment strategies and targeted therapies. Centrosomes and their associated proteins have been shown to play key roles in the pathogenesis of breast cancer and thus represent promising targets for drug and biomarker development. Centrosomes are fundamental cellular structures in the mammalian cell that are responsible for error-free execution of cell division. Centrosome amplification and aberrant expression of its associated proteins such as Polo-like kinases (PLKs), Aurora kinases (AURKs) and Cyclin-dependent kinases (CDKs) have been observed in various cancers, including breast cancer. These aberrations in breast cancer are thought to cause improper chromosomal segregation during mitosis, leading to chromosomal instability and uncontrolled cell division, allowing cancer cells to acquire new genetic changes that result in evasion of cell death and the promotion of tumor formation. Various chemical compounds developed against PLKs and AURKs have shown meaningful antitumorigenic effects in breast cancer cells in vitro and in vivo. The mechanism of action of these inhibitors is likely related to exacerbation of numerical genomic instability, such as aneuploidy or polyploidy. Furthermore, growing evidence demonstrates enhanced antitumorigenic effects when inhibitors specific to centrosome-associated proteins are used in combination with either radiation or chemotherapy drugs in breast cancer. This review focuses on the current knowledge regarding the roles of centrosome and centrosome-associated proteins in breast cancer pathogenesis and their utility as novel targets for breast cancer treatment.

Degradation of Polo-like Kinase 1 by the Novel Poly-Arginine N-Degron Pathway PROTAC Regulates Tumor Growth in Nonsmall Cell Lung Cancer

Polo-like kinase 1 (PLK1), which is crucial in cell cycle regulation, is considered a promising anticancer drug target. Herein, we present the N-degron pathway-based proteolysis targeting chimera (PROTAC) for PLK1 degradation, targeting the Polo-box domain (PBD). We identified DD-2 as the most potent PROTAC that selectively induces PLK1 degradation in cancer cells, including HeLa and nonsmall cell lung cancer (NSCLC), through the N-degron pathway. DD-2 exhibited significant in vitro anticancer effects, inducing G2/M arrest and apoptosis in HeLa and NSCLC cell lines. DD-2 showed significant tumor growth inhibition in a xenograft mouse model using HeLa and NSCLC cell lines, highlighting its potential in cancer treatment. Furthermore, the combination of DD-2 with tyrosine kinase inhibitor (TKI), osimertinib, effectively suppressed tumor growth in double-mutated H1975 cell lines, emphasizing DD-2's potential in combination cancer therapies. Collectively, this study demonstrates the potential of the N-degron pathway, especially using DD-2, for targeted cancer therapies.

Transcriptome and single-cell transcriptomics reveal prognostic value and potential mechanism of anoikis in skin cutaneous melanoma

BACKGROUND

Skin cutaneous melanoma (SKCM) is a highly lethal cancer, ranking among the top four deadliest cancers. This underscores the urgent need for novel biomarkers for SKCM diagnosis and prognosis. Anoikis plays a vital role in cancer growth and metastasis, and this study aims to investigate its prognostic value and mechanism of action in SKCM.

METHODS

Utilizing consensus clustering, the SKCM samples were categorized into two distinct clusters A and B based on anoikis-related genes (ANRGs), with the B group exhibiting lower disease-specific survival (DSS). Gene set enrichment between distinct clusters was examined using Gene Set Variation Analysis (GSVA) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis.

RESULTS

We created a predictive model based on three anoikis-related differently expressed genes (DEGs), specifically, FASLG, IGF1, and PIK3R2. Moreover, the mechanism of these prognostic genes within the model was investigated at the cellular level using the single-cell sequencing dataset GSE115978. This analysis revealed that the FASLG gene was highly expressed on cluster 1 of Exhausted CD8( +) T (Tex) cells.

CONCLUSIONS

In conclusion, we have established a novel classification system for SKCM based on anoikis, which carries substantial clinical implications for SKCM patients. Notably, the elevated expression of the FASLG gene on cluster 1 of Tex cells could significantly impact SKCM prognosis through anoikis, thus offering a promising target for the development of immunotherapy for SKCM.

Eph signal inhibition potentiates the growth-inhibitory effects of PLK1 inhibition toward cancer cells

Anti-mitotic drugs are clinically used as anti-cancer treatments. Polo-like kinase 1 (PLK1) is a promising target against cancer cell division due to its importance in the whole process of mitosis, and thus PLK1-targeting agents have been developed in the last few decades. Clinical trial studies show that several PLK1 inhibitors are generally well-tolerated. However, the response rates are limited; therefore, it is needed to improve the efficacy of those drugs. Here, we show that NVP-BHG712, an erythropoietin-producing human hepatocellular (Eph) signaling inhibitor, potentiates the growth-inhibitory effects of the PLK1 inhibitors BI2536 and BI6727 in cancer cells. This combination treatment strongly suppresses cancer spheroid formation. Moreover, the combination drastically arrests cells at mitosis by continuous activation of the spindle assembly checkpoint (SAC), thereby inducing apoptosis. SAC activation caused by the combination of NVP-BHG712 and BI2536 is due to the inhibition of centrosome maturation and separation. Although the inactivation level of the PLK1 kinase is comparable between BI2536 treatment alone and combination treatment, the combination treatment strongly inactivates MAPK signaling in mitosis. Since inhibition of MAPK signaling potentiates the efficacy of BI2536 treatment, inactivation of PLK1 kinase and MAPK signaling contributes to the strong inhibition of centrosome separation. These results suggest that Eph signal inhibition potentiates the effect of PLK1 inhibition, leading to strong mitotic arrest via SAC activation and the subsequent reduction of cancer cell survival. The combination of PLK1 inhibition and Eph signal inhibition will provide a new effective strategy for targeting cancer cell division.

A CIC-related-epigenetic factors-based model associated with prediction, the tumor microenvironment and drug sensitivity in osteosarcoma

Osteosarcoma is generally considered a cold tumor and is characterized by epigenetic alterations. Although tumor cells are surrounded by many immune cells such as macrophages, T cells may be suppressed, be inactivated, or not be presented due to various mechanisms, which usually results in poor prognosis and insensitivity to immunotherapy. Immunotherapy is considered a promising anti-cancer therapy in osteosarcoma but requires more research, but osteosarcoma does not currently respond well to this therapy. The cancer immunity cycle (CIC) is essential for anti-tumor immunity, and is epigenetically regulated. Therefore, it is possible to modulate the immune microenvironment of osteosarcoma by targeting epigenetic factors. In this study, we explored the correlation between epigenetic modulation and CIC in osteosarcoma through bioinformatic methods. Based on the RNA data from TARGET and GSE21257 cohorts, we identified epigenetic related subtypes by NMF clustering and constructed a clinical prognostic model by the LASSO algorithm. ESTIMATE, Cibersort, and xCell algorithms were applied to analyze the tumor microenvironment. Based on eight epigenetic biomarkers (SFMBT2, SP140, CBX5, HMGN2, SMARCA4, PSIP1, ACTR6, and CHD2), two subtypes were identified, and they are mainly distinguished by immune response and cell cycle regulation. After excluding ACTR6 by LASSO regression, the prognostic model was established and it exhibited good predictive efficacy. The risk score showed a strong correlation with the tumor microenvironment, drug sensitivity and many immune checkpoints. In summary, our study sheds a new light on the CIC-related epigenetic modulation mechanism of osteosarcoma and helps search for potential drugs for osteosarcoma treatment.

The role of primary cilia in thyroid diseases

Primary cilia (PC) are non-motile and microtube-based organelles protruding from the surface of almost all thyroid follicle cells. They maintain homeostasis in thyrocytes and loss of PC can result in diverse thyroid diseases. The dysfunction of structure and function of PC are found in many patients with common thyroid diseases. The alterations are associated with the cause, development, and recovery of the diseases and are regulated by PC-mediated signals. Restoring normal PC structure and function in thyrocytes is a promising therapeutic strategy to treat thyroid diseases. This review explores the function of PC in normal thyroid glands. It summarizes the pathology caused by PC alterations in thyroid cancer (TC), autoimmune thyroid diseases (AITD), hypothyroidism, and thyroid nodules (TN) to provide comprehensive references for further study.

Application of a Fluorescence Recovery-Based Polo-Like Kinase 1 Binding Assay to Polo-Like Kinase 2 and Polo-Like Kinase 3

Assay systems for evaluating compound protein-binding affinities are essential for developing agonists and/or antagonists. Targeting individual members of a protein family can be extremely important and for this reason it is critical to have methods for evaluating selectivity. We have previously reported a fluorescence recovery assay that employs a fluorescein-labelled probe to determine IC50 values of ATP-competitive type 1 inhibitors of polo-like kinase 1 (Plk1). This probe is based on the potent Plk1 inhibitor BI2536 [fluorescein isothiocyanate (FITC)-polyethylene glycol (PEG)-lysine (Lys) (BI2536) 1]. Herein, we extend this approach to the highly homologous Plk2 and Plk3 members of this kinase family. Our results suggest that this assay system is suitable for evaluating binding affinities against Plk2 and Plk3 as well as Plk1. The new methodology represents the first example of evaluating N-terminal catalytic kinase domain (KD) affinities of Plk2 and Plk3. It represents a simple and cost-effective alternative to traditional kinase assays to explore the KD-binding compounds against Plk2 and Plk3 as well as Plk1.

Small Molecule Ligands of the BET-like Bromodomain, SmBRD3, Affect Schistosoma mansoni Survival, Oviposition, and Development

Schistosomiasis is a disease affecting >200 million people worldwide, but its treatment relies on a single agent, praziquantel. To investigate new avenues for schistosomiasis control, we have conducted the first systematic analysis of bromodomain-containing proteins (BCPs) in a causative species, Schistosoma mansoni. Having identified 29 putative bromodomains (BRDs) in 22 S. mansoni proteins, we selected SmBRD3, a tandem BRD-containing BCP that shows high similarity to the human bromodomain and extra terminal domain (BET) family, for further studies. Screening 697 small molecules identified the human BET BRD inhibitor I-BET726 as a ligand for SmBRD3. An X-ray crystal structure of I-BET726 bound to the second BRD of SmBRD3 [SmBRD3(2)] enabled rational design of a quinoline-based ligand (15) with an ITC Kd = 364 ± 26.3 nM for SmBRD3(2). The ethyl ester pro-drug of compound 15 (compound 22) shows substantial effects on sexually immature larval schistosomula, sexually mature adult worms, and snail-infective miracidia in ex vivo assays.

A Comprehensive Review of Small Interfering RNAs (siRNAs): Mechanism, Therapeutic Targets, and Delivery Strategies for Cancer Therapy

Small interfering RNA (siRNA) delivery by nanocarriers has been identified as a promising strategy in the study and treatment of cancer. Short nucleotide sequences are synthesized exogenously to create siRNA, which triggers RNA interference (RNAi) in cells and silences target gene expression in a sequence-specific way. As a nucleic acid-based medicine that has gained popularity recently, siRNA exhibits novel potential for the treatment of cancer. However, there are still many obstacles to overcome before clinical siRNA delivery devices can be developed. In this review, we discuss prospective targets for siRNA drug design, explain siRNA drug properties and benefits, and give an overview of the current clinical siRNA therapeutics for the treatment of cancer. Additionally, we introduce the siRNA chemical modifications and delivery systems that are clinically sophisticated and classify bioresponsive materials for siRNA release in a methodical manner. This review will serve as a reference for researchers in developing more precise and efficient targeted delivery systems, promoting ongoing advances in clinical applications.

Palmitoylation landscapes across human cancers reveal a role of palmitoylation in tumorigenesis

BACKGROUND

Protein palmitoylation, which is catalyzed by palmitoyl-transferase and de-palmitoyl-transferase, plays a crucial role in various biological processes. However, the landscape and dynamics of protein palmitoylation in human cancers are not well understood.

METHODS

We utilized 23 palmitoyl-acyltransferases and seven de-palmitoyl-acyltransferases as palmitoylation-related genes for protein palmitoylation analysis. Multiple publicly available datasets were employed to conduct pan-cancer analysis, examining the transcriptome, genomic alterations, clinical outcomes, and correlation with c-Myc (Myc) for palmitoylation-related genes. Real-time quantitative PCR and immunoblotting were performed to assess the expression of palmitoylation-related genes and global protein palmitoylation levels in cancer cells treated with Myc depletion or small molecule inhibitors. Protein docking and drug sensitivity analyses were employed to predict small molecules that target palmitoylation-related genes.

RESULTS

We identified associations between palmitoylation and cancer subtype, stage, and patient survival. We discovered that abnormal DNA methylation and oncogenic Myc-driven transcriptional regulation synergistically contribute to the dysregulation of palmitoylation-related genes. This dysregulation of palmitoylation was closely correlated with immune infiltration in the tumor microenvironment and the response to immunotherapy. Importantly, dysregulated palmitoylation was found to modulate canonical cancer-related pathways, thus influencing tumorigenesis. To support our findings, we performed a proof-of-concept experiment showing that depletion of Myc led to reduced expression of most palmitoylation-related genes, resulting in decreased global protein palmitoylation levels. Through mass spectrometry and enrichment analyses, we also identified palmitoyl-acyltransferases ZDHHC7 and ZDHHC23 as significant contributors to mTOR signaling, DNA repair, and immune pathways, highlighting their potential roles in tumorigenesis. Additionally, our study explored the potential of three small molecular (BI-2531, etoposide, and piperlongumine) to modulate palmitoylation by targeting the expression or activity of palmitoylation-related genes or enzymes.

CONCLUSIONS

Overall, our findings underscore the critical role of dysregulated palmitoylation in tumorigenesis and the response to immunotherapy, mediated through classical cancer-related pathways and immune cell infiltration. Additionally, we propose that the aforementioned three small molecule hold promise as potential therapeutics for modulating palmitoylation, thereby offering novel avenues for cancer therapy.

Temporally distinct roles of Aurora A in polarization of the C. elegans zygote

During asymmetric cell division, coordination of cell polarity and the cell cycle is critical for proper inheritance of cell fate determinants and generation of cellular diversity. In Caenorhabditis elegans (C. elegans), polarity is established in the zygote and is governed by evolutionarily conserved Partitioning defective (PAR) proteins that localize to distinct cortical domains. At the time of polarity establishment, anterior and posterior PARs segregate to opposing cortical domains that specify asymmetric cell fates. Timely establishment of these PAR domains requires a cell cycle kinase, Aurora A (AIR-1 in C.elegans). Aurora A depletion by RNAi causes a spectrum of phenotypes including no posterior domain, reversed polarity, and excess posterior domains. How depletion of a single kinase can cause seemingly opposite phenotypes remains obscure. Using an auxin-inducible degradation system, drug treatments, and high-resolution microscopy, we found that AIR-1 regulates polarity via distinct mechanisms at different times of the cell cycle. During meiosis I, AIR-1 acts to prevent the formation of bipolar domains, while in meiosis II, AIR-1 is necessary to recruit PAR-2 onto the membrane. Together these data clarify the origin of the multiple polarization phenotypes observed in RNAi experiments and reveal multiple roles of AIR-1 in coordinating PAR protein localization with the progression of the cell cycle.

Prognostic value and immune landscapes of cuproptosis-related lncRNAs in esophageal squamous cell carcinoma

BACKGROUND

Precisely forecasting the prognosis of esophageal squamous cell carcinoma (ESCC) patients is a formidable challenge. Cuproptosis has been implicated in ESCC pathogenesis; however, the prognostic value of cuproptosis-associated long noncoding RNAs (CuRLs) in ESCC is unclear.

METHODS

Transcriptomic and clinical data related to ESCC were sourced from The Cancer Genome Atlas (TCGA). Using coexpression and Cox regression analysis to identify prognostically significant CuRLs, a prognostic signature was created. Nomogram models were established by incorporating the risk score and clinical characteristics. Tumor Immune Dysfunction and Rejection (TIDE) scores were derived by conducting an immune landscape analysis and evaluating the tumor mutational burden (TMB). Drug sensitivity analysis was performed to explore the underlying molecular mechanisms and guide clinical dosing.

RESULTS

Our risk score based on 5 CuRLs accurately predicted poorer prognosis in high-risk ESCC patients across almost all subgroups. The nomogram that included the risk score provided more precise prognostic predictions. Immune pathways, such as the B-cell receptor signaling pathway, were enriched in the datasets from high-risk patients. High TMB in high-risk patients indicated a relatively poor prognosis. High-risk patients with lower TIDE scores were found to benefit more from immunotherapy. High-risk patients exhibited greater responsiveness to Nilotinib, BI-2536, P22077, Zoledronate, and Fulvestrant, as revealed by drug sensitivity analysis. Real-time PCR validation demonstrated significant differential expression of four CuRLs between ESCC and normal cell lines.

CONCLUSIONS

The above risk score and nomogram can accurately predict prognosis in ESCC patients and provide guidance for chemotherapy and immunotherapy.

Diverse microtubule-targeted anticancer agents kill cells by inducing chromosome missegregation on multipolar spindles

Microtubule-targeted agents are commonly used for cancer treatment, though many patients do not benefit. Microtubule-targeted drugs were assumed to elicit anticancer activity via mitotic arrest because they cause cell death following mitotic arrest in cell culture. However, we recently demonstrated that intratumoral paclitaxel concentrations are insufficient to induce mitotic arrest and rather induce chromosomal instability (CIN) via multipolar mitotic spindles. Here, we show in metastatic breast cancer and relevant human cellular models that this mechanism is conserved among clinically useful microtubule poisons. While multipolar divisions typically produce inviable progeny, multipolar spindles can be focused into near-normal bipolar spindles at any stage of mitosis. Using a novel method to quantify the rate of CIN, we demonstrate that cell death positively correlates with net loss of DNA. Spindle focusing decreases CIN and causes resistance to diverse microtubule poisons, which can be counteracted by addition of a drug that increases CIN without affecting spindle polarity. These results demonstrate conserved mechanisms of action and resistance for diverse microtubule-targeted agents. Trial registration: clinicaltrials.gov, NCT03393741.

Mild replication stress causes premature centriole disengagement via a sub-critical Plk1 activity under the control of ATR-Chk1

A tight synchrony between the DNA and centrosome cycle is essential for genomic integrity. Centriole disengagement, which licenses centrosomes for duplication, occurs normally during mitotic exit. We recently demonstrated that mild DNA replication stress typically seen in cancer cells causes premature centriole disengagement in untransformed mitotic human cells, leading to transient multipolar spindles that favour chromosome missegregation. How mild replication stress accelerates the centrosome cycle at the molecular level remained, however, unclear. Using ultrastructure expansion microscopy, we show that mild replication stress induces premature centriole disengagement already in G2 via the ATR-Chk1 axis of the DNA damage repair pathway. This results in a sub-critical Plk1 kinase activity that primes the pericentriolar matrix for Separase-dependent disassembly but is insufficient for rapid mitotic entry, causing premature centriole disengagement in G2. We postulate that the differential requirement of Plk1 activity for the DNA and centrosome cycles explains how mild replication stress disrupts the synchrony between both processes and contributes to genomic instability.

Polo-like kinase 1 promotes pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) is a lethal vascular disease with limited therapeutic options. The mechanistic connections between alveolar hypoxia and PH are not well understood. The aim of this study was to investigate the role of mitotic regulator Polo-like kinase 1 (PLK1) in PH development.

METHODS

Mouse lungs along with human pulmonary arterial smooth muscle cells and endothelial cells were used to investigate the effects of hypoxia on PLK1. Hypoxia- or Sugen5416/hypoxia was applied to induce PH in mice. Plk1 heterozygous knockout mice and PLK1 inhibitors (BI 2536 and BI 6727)-treated mice were checked for the significance of PLK1 in the development of PH.

RESULTS

Hypoxia stimulated PLK1 expression through induction of HIF1α and RELA. Mice with heterozygous deletion of Plk1 were partially resistant to hypoxia-induced PH. PLK1 inhibitors ameliorated PH in mice.

CONCLUSIONS

Augmented PLK1 is essential for the development of PH and is a druggable target for PH.

Genetic enhancers of partial PLK1 inhibition reveal hypersensitivity to kinetochore perturbations

Polo-like kinase 1 (PLK1) is a serine/threonine kinase required for mitosis and cytokinesis. As cancer cells are often hypersensitive to partial PLK1 inactivation, chemical inhibitors of PLK1 have been developed and tested in clinical trials. However, these small molecule inhibitors alone are not completely effective. PLK1 promotes numerous molecular and cellular events in the cell division cycle and it is unclear which of these events most crucially depend on PLK1 activity. We used a CRISPR-based genome-wide screening strategy to identify genes whose inactivation enhances cell proliferation defects upon partial chemical inhibition of PLK1. Genes identified encode proteins that are functionally linked to PLK1 in multiple ways, most notably factors that promote centromere and kinetochore function. Loss of the kinesin KIF18A or the outer kinetochore protein SKA1 in PLK1-compromised cells resulted in mitotic defects, activation of the spindle assembly checkpoint and nuclear reassembly defects. We also show that PLK1-dependent CENP-A loading at centromeres is extremely sensitive to partial PLK1 inhibition. Our results suggest that partial inhibition of PLK1 compromises the integrity and function of the centromere/kinetochore complex, rendering cells hypersensitive to different kinetochore perturbations. We propose that KIF18A is a promising target for combinatorial therapies with PLK1 inhibitors.

Drug screening in human physiologic medium identifies uric acid as an inhibitor of rigosertib efficacy

The non-physiological nutrient levels found in traditional culture media have been shown to affect numerous aspects of cancer cell physiology, including how cells respond to certain therapeutic agents. Here, we comprehensively evaluated how physiological nutrient levels impact therapeutic response by performing drug screening in human plasma-like medium (HPLM). We observed dramatic nutrient-dependent changes in sensitivity to a variety of FDA-approved and clinically trialed compounds, including rigosertib, an experimental cancer therapeutic that has recently failed in phase 3 clinical trials. Mechanistically, we found that the ability of rigosertib to destabilize microtubules is strongly inhibited by the purine metabolism waste product uric acid, which is uniquely abundant in humans relative to traditional in vitro and in vivo cancer models. Structural modelling studies suggest that uric acid interacts with the tubulin-rigosertib complex and may act as an uncompetitive inhibitor of rigosertib. These results offer a possible explanation for the failure of rigosertib in clinical trials and demonstrate the utility of physiological media to achieve in vitro results that better represent human therapeutic responses.

A novel DNA damage repair-related gene signature predicting survival, immune infiltration and drug sensitivity in cervical cancer based on single cell sequencing

Background

Aberrant DNA damage repair (DDR) is one of the hallmarks of tumors, and therapeutic approaches targeting this feature are gaining increasing attention. This study aims to develop a signature of DDR-related genes to evaluate the prognosis of cervical cancer (CC).

Methods

Differentially expressed genes were identified between high and low DDR groups of cells from the single-cell RNA sequencing dataset GSE168652 based on DDR scores. Using the ssGSEA and WGCNA methods, DDR-related differentially expressed genes were identified from different patients within the TCGA-CESC cohort. Using Cox analysis and LASSO regression analysis, a DDR-related gene signature was constructed based on the intersection of two groups of differentially expressed genes and DDR-related genes from WGCNA, and validated in GSE52903. Immune cell infiltration analysis, mutation analysis, survival analysis, drug sensitivity analysis, etc., were performed in different groups which were established based on the DDR gene signature scoring. A key gene affecting prognosis was selected and validated through biological experiments such as wound healing, migration, invasion, and comet assays.

Results

A novel DDR-related signature was constructed and the nomogram results showed this signature performed better in predicting prognosis than other clinical features for CC. The high DDR group exhibited poorer prognosis, weaker immune cell infiltration in the immune microenvironment, lower expression of immune checkpoint-related genes, lower gene mutation frequencies and more sensitivity to drugs such as BI.2536, Bleomycin and etc. ITGB1, ZC3H13, and TOMM20 were expressed at higher levels in CaSki and HeLa cells compared to ECT1 cells. Compared with the native CaSki and HeLa cells, the proliferation, migration, invasion and DDR capabilities of CaSki and HeLa cell lines with ITGB1 suppressed expression were significantly decreased.

Conclusion

The 7 DDR-related gene signature was an independent and powerful prognostic biomarker that might effectively evaluate the prognosis of CC and provide supplementary information for a more personalized evaluation and precision therapy. ITGB1 was a potential candidate gene that may affect the DDR capacity of CC cells, and its mechanism of action was worth further in-depth study.

A polo-like kinase inhibitor identified by computational repositioning attenuates pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a fatal fibrotic lung disease with few effective therapeutic options. Recently, drug repositioning, which involves identifying novel therapeutic potentials for existing drugs, has been popularized as a new approach for the development of novel therapeutic reagents. However, this approach has not yet been fully utilized in the field of pulmonary fibrosis.

METHODS

The present study identified novel therapeutic options for pulmonary fibrosis using a systematic computational approach for drug repositioning based on integration of public gene expression signatures of drug and diseases (in silico screening approach).

RESULTS

Among the top compounds predicted to be therapeutic for IPF by the in silico approach, we selected BI2536, a polo-like kinase (PLK) 1/2 inhibitor, as a candidate for treating pulmonary fibrosis using an in silico analysis. However, BI2536 accelerated mortality and weight loss rate in an experimental mouse model of pulmonary fibrosis. Because immunofluorescence staining revealed that PLK1 expression was dominant in myofibroblasts while PLK2 expression was dominant in lung epithelial cells, we next focused on the anti-fibrotic effect of the selective PLK1 inhibitor GSK461364. Consequently, GSK461364 attenuated pulmonary fibrosis with acceptable mortality and weight loss in mice.

CONCLUSIONS

These findings suggest that targeting PLK1 may be a novel therapeutic approach for pulmonary fibrosis by inhibiting lung fibroblast proliferation without affecting lung epithelial cells. In addition, while in silico screening is useful, it is essential to fully determine the biological activities of candidates by wet-lab validation studies.

Kinase Degraders, Activators, and Inhibitors: Highlights and Synthesis Routes to the Chemical Probes on opnMe.com, Part 1

Kinases are among the most important and successful drug targets. Chemical probe compounds have played a critical role in elucidating the role of kinases in many biological pathways. There are currently twelve well-validated chemical probes that target kinases available free-of-cost via the Molecules to Order (M2O) arm of Boehringer Ingelheim's open innovation platform, opnMe.com. Here we present a summary of the key data for each of these probe compounds and the synthesis routes to all twelve compounds. We hope this will aid researchers who use or plan to use these compounds in their research.

The Role of Polo-Like Kinase 1 in Regulating the Forkhead Box Family Transcription Factors

Polo-like kinase 1 (PLK1) is a serine/threonine kinase with more than 600 phosphorylation substrates through which it regulates many biological processes, including mitosis, apoptosis, metabolism, RNA processing, vesicle transport, and G₂ DNA-damage checkpoint recovery, among others. Among the many PLK1 targets are members of the FOX family of transcription factors (FOX TFs), including FOXM1, FOXO1, FOXO3, and FOXK1. FOXM1 and FOXK1 have critical oncogenic roles in cancer through their antagonism of apoptotic signals and their promotion of cell proliferation, metastasis, angiogenesis, and therapeutic resistance. In contrast, FOXO1 and FOXO3 have been identified to have broad functions in maintaining cellular homeostasis. In this review, we discuss PLK1-mediated regulation of FOX TFs, highlighting the effects of PLK1 on the activity and stability of these proteins. In addition, we review the prognostic and clinical significance of these proteins in human cancers and, more importantly, the different approaches that have been used to disrupt PLK1 and FOX TF-mediated signaling networks. Furthermore, we discuss the therapeutic potential of targeting PLK1-regulated FOX TFs in human cancers.

GSK461364A suppresses proliferation of gastric cancer cells and induces apoptosis

Polo-like kinase-1 (PLK1) is crucial in regulating cell division and has been shown to have an oncogenic function in several cancers. Since PLK1 overexpression is closely related to tumorigenesis and has been correlated with poor clinical outcomes, specific inhibition of PLK1 in cancer cells is a promising approach for developing new anticancer drugs. In this context, the aim of the present study was to evaluated the potential cytotoxic effects of GSK461364A, a competitive inhibitor for PLK1, in gastric cancer cell line SNU-1 cells and explored its cytotoxic mechanism. The cells were exposed to GSK461364A at different concentrations ranging from 1 to 40 μM for 24 h, and it showed considerable cytotoxicity with an IC50 value of 4.34 μM. The treatment of SNU-1 cells with GSK461364A results in cell cycle arrest at the G2/M phase, decreased mitochondrial membrane potential, and increased apoptosis as indicated by Annexin V binding assay. In addition, GSK461364A treatment significantly increased the total oxidant (TOS) level, a signal of oxidative stress, and increased cleaved PARP and 8-oxo-dG levels as an indicator of DNA damage. ELISA experiments evaluating Bax, BCL-2, and cleaved caspase-3 also confirmed the apoptotic effect of GSK461364A. Current findings suggest that GSK461364A may be a chemotherapeutic agent in patients with gastric cancer. Nevertheless, more research is needed to evaluate GSK461364A as a cancer treatment drug.

Targeting bromodomain-containing proteins: research advances of drug discovery

Bromodomain (BD) is an evolutionarily conserved protein module found in 46 different BD-containing proteins (BCPs). BD acts as a specific reader for acetylated lysine residues (KAc) and serves an essential role in transcriptional regulation, chromatin remodeling, DNA damage repair, and cell proliferation. On the other hand, BCPs have been shown to be involved in the pathogenesis of a variety of diseases, including cancers, inflammation, cardiovascular diseases, and viral infections. Over the past decade, researchers have brought new therapeutic strategies to relevant diseases by inhibiting the activity or downregulating the expression of BCPs to interfere with the transcription of pathogenic genes. An increasing number of potent inhibitors and degraders of BCPs have been developed, some of which are already in clinical trials. In this paper, we provide a comprehensive review of recent advances in the study of drugs that inhibit or down-regulate BCPs, focusing on the development history, molecular structure, biological activity, interaction with BCPs and therapeutic potentials of these drugs. In addition, we discuss current challenges, issues to be addressed and future research directions for the development of BCPs inhibitors. Lessons learned from the successful or unsuccessful development experiences of these inhibitors or degraders will facilitate the further development of efficient, selective and less toxic inhibitors of BCPs and eventually achieve drug application in the clinic.

BICD2 phosphorylation regulates dynein function and centrosome separation in G2 and M

The activity of dynein is regulated by a number of adaptors that mediate its interaction with dynactin, effectively activating the motor complex while also connecting it to different cargos. The regulation of adaptors is consequently central to dynein physiology but remains largely unexplored. We now describe that one of the best-known dynein adaptors, BICD2, is effectively activated through phosphorylation. In G2, phosphorylation of BICD2 by CDK1 promotes its interaction with PLK1. In turn, PLK1 phosphorylation of a single residue in the N-terminus of BICD2 results in a structural change that facilitates the interaction with dynein and dynactin, allowing the formation of active motor complexes. Moreover, modified BICD2 preferentially interacts with the nucleoporin RanBP2 once RanBP2 has been phosphorylated by CDK1. BICD2 phosphorylation is central for dynein recruitment to the nuclear envelope, centrosome tethering to the nucleus and centrosome separation in the G2 and M phases of the cell cycle. This work reveals adaptor activation through phosphorylation as crucial for the spatiotemporal regulation of dynein activity.

Human Polo-like Kinase Inhibitors as Antiplasmodials

Protein kinases have proven to be a very productive class of therapeutic targets, and over 90 inhibitors are currently in clinical use primarily for the treatment of cancer. Repurposing these inhibitors as antimalarials could provide an accelerated path to drug development. In this study, we identified BI-2536, a known potent human polo-like kinase 1 inhibitor, with low nanomolar antiplasmodial activity. Screening of additional PLK1 inhibitors revealed further antiplasmodial candidates despite the lack of an obvious orthologue of PLKs in Plasmodium. A subset of these inhibitors was profiled for their in vitro killing profile, and commonalities between the killing rate and inhibition of nuclear replication were noted. A kinase panel screen identified PfNEK3 as a shared target of these PLK1 inhibitors; however, phosphoproteome analysis confirmed distinct signaling pathways were disrupted by two structurally distinct inhibitors, suggesting PfNEK3 may not be the sole target. Genomic analysis of BI-2536-resistant parasites revealed mutations in genes associated with the starvation-induced stress response, suggesting BI-2536 may also inhibit an aminoacyl-tRNA synthetase.

Polo-like kinase inhibitor BI2536 induces eryptosis

BI2536 is potent inhibitor of polo-like kinases PLK1, 2, and 3. The inhibition of PLKs in nucleated cells induces apoptosis by perturbing the cell cycle with consequent engagement of mitotic catastrophe. BI2536 is being tested as chemotherapy in various phase I/II/III clinical trials. Erythrocytes do not have a nucleus; however, they may undergo programmed suicide with characteristic hallmarks including cell shrinkage and phosphatidylserine translocation to the cell surface. This particular death is baptized eryptosis. Our study explored whether BI2536 induces eryptosis. We used flow cytometry to access death in red blood cells. We analyzed the cellular volume, the intracellular calcium concentration, the cell surface phosphatidylserine exposure, and the ceramide abundance. In addition, we analyzed the effect of BI2536 on hemolysis. Our investigation showed that after 48 h of incubation with PLK inhibitor BI2536, erythrocytes lost volume and were positive for annexin‑V without any effect on hemolysis. Cells also showed an abundance of ceramide and an increase of intracellular calcium. All these finding suggest that BI2536 provokes eryptosis in red blood cells, ostensibly in part due to Ca2+ entry and ceramide accumulation.

Development of Cell Permeable NanoBRET Probes for the Measurement of PLK1 Target Engagement in Live Cells

PLK1 is a protein kinase that regulates mitosis and is both an important oncology drug target and a potential antitarget of drugs for the DNA damage response pathway or anti-infective host kinases. To expand the range of live cell NanoBRET target engagement assays to include PLK1, we developed an energy transfer probe based on the anilino-tetrahydropteridine chemotype found in several selective PLK inhibitors. Probe 11 was used to configure NanoBRET target engagement assays for PLK1, PLK2, and PLK3 and measure the potency of several known PLK inhibitors. In-cell target engagement for PLK1 was in good agreement with the reported cellular potency for the inhibition of cell proliferation. Probe 11 enabled the investigation of the promiscuity of adavosertib, which had been described as a dual PLK1/WEE1 inhibitor in biochemical assays. Live cell target engagement analysis of adavosertib via NanoBRET demonstrated PLK activity at micromolar concentrations but only selective engagement of WEE1 at clinically relevant doses.

Study on Pharmacokinetics and Metabolic Profiles of Novel Potential PLK-1 Inhibitors by UHPLC-MS/MS Combined with UHPLC-Q-Orbitrap/HRMS

PLK-1 (Polo-like kinase-1) plays an essential role in cytokinesis, and its aberrant expression is considered to be keenly associated with a wide range of cancers. It has been selected as an appealing target and small-molecule inhibitors have been developed and studied in clinical trials. Unfortunately, most have been declared as failures due to the poor therapeutic response and off-target toxicity. In the present study, a novel potent PLK-1 inhibitor, compound 7a, was designed and synthetized. 1H NMR, 13C NMR, 19F NMR and mass spectrum were comprehensively used for the compound characterization. The compound exhibited higher potency against PLK-1 kinase, HCT-116 and NCI-H2030 cell lines than the positive control. Molecular docking indicated that the binding mode that the ATP binding site of PLK-1 was occupied by the compound. Then, a UHPLC-MS/MS method was established and validated to explore the pharmacokinetic behavior of the drug candidate. The method had good selectivity, high sensitivity and wide linearity. The exposure increased linearly with the dose, but the oral bioavailability was not satisfactory enough. Then, the metabolism was studied using liver microsomes by UHPLC-Q-Orbitrap/HRMS. Our research first studied the pharmacokinetic metabolic characteristics of 7a and may serve as a novel lead compound for the development of PLK-1 inhibitors.

Development of Cell Permeable NanoBRET Probes for the Measurement of PLK1 Target Engagement in Live Cells

PLK1 is a protein kinase that regulates mitosis and is both an important oncology drug target and a potential anti target of drugs for the DNA damage response pathway or anti-infective host kinases. To expand the range of live cell NanoBRET target engagement assays to include PLK1 we developed an energy transfer probe based on the anilino-tetrahydropteridine chemotype found in several selective PLK inhibitors. Probe 11 was used to configure NanoBRET target engagement assays for PLK1, PLK2, and PLK3 and measure the potency of several known PLK inhibitors. In cell target engagement for PLK1 was in good agreement with the reported cellular potency for inhibition of cell proliferation. Probe 11 enabled investigation of the promiscuity of adavosertib, which had been described as a dual PLK1/WEE1 inhibitor in biochemical assays. Live cell target engagement analysis of adavosertib by NanoBRET demonstrated PLK activity at micromolar concentrations but only selective engagement of WEE1 at clinically relevant doses.

Increased recombinant adeno-associated virus production by HEK293 cells using small molecule chemical additives

Recombinant adeno-associated virus (rAAV) has established itself as a highly efficacious gene delivery vector with a well characterised safety profile allowing broad clinical application. Recent successes in rAAV-mediated gene therapy clinical trials will continue to drive demand for improved rAAV production processes to reduce costs. Here, we demonstrate that small molecule bioactive chemical additives can significantly increase recombinant AAV vector production by human embryonic kidney (HEK) cells up to three-fold. Nocodazole (an anti-mitotic agent) and M344 (a selective histone deacetylase inhibitor) were identified as positive regulators of rAAV8 genome titre in a microplate screening assay. Addition of nocodazole to triple-transfected HEK293 suspension cells producing rAAV arrested cells in G2/M phase, increased average cell volume and reduced viable cell density relative to untreated rAAV producing cells at harvest. Final crude genome vector titre from nocodazole treated cultures was >2-fold higher compared to non-treated cultures. Further investigation showed nocodazole addition to cultures to be time critical. Genome titre improvement was found to be scalable and serotype independent across two distinct rAAV serotypes, rAAV8 and rAAV9. Furthermore, a combination of M344 and nocodazole produced a positive additive effect on rAAV8 genome titre, resulting in a three-fold increase in genome titre compared to untreated cells.

Drugging Hijacked Kinase Pathways in Pediatric Oncology: Opportunities and Current Scenario

Childhood cancer is considered rare, corresponding to ~3% of all malignant neoplasms in the human population. The World Health Organization (WHO) reports a universal occurrence of more than 15 cases per 100,000 inhabitants around the globe, and despite improvements in diagnosis, treatment and supportive care, one child dies of cancer every 3 min. Consequently, more efficient, selective and affordable therapeutics are still needed in order to improve outcomes and avoid long-term sequelae. Alterations in kinases' functionality is a trademark of cancer and the concept of exploiting them as drug targets has burgeoned in academia and in the pharmaceutical industry of the 21st century. Consequently, an increasing plethora of inhibitors has emerged. In the present study, the expression patterns of a selected group of kinases (including tyrosine receptors, members of the PI3K/AKT/mTOR and MAPK pathways, coordinators of cell cycle progression, and chromosome segregation) and their correlation with clinical outcomes in pediatric solid tumors were accessed through the R2: Genomics Analysis and Visualization Platform and by a thorough search of published literature. To further illustrate the importance of kinase dysregulation in the pathophysiology of pediatric cancer, we analyzed the vulnerability of different cancer cell lines against their inhibition through the Cancer Dependency Map portal, and performed a search for kinase-targeted compounds with approval and clinical applicability through the CanSAR knowledgebase. Finally, we provide a detailed literature review of a considerable set of small molecules that mitigate kinase activity under experimental testing and clinical trials for the treatment of pediatric tumors, while discuss critical challenges that must be overcome before translation into clinical options, including the absence of compounds designed specifically for childhood tumors which often show differential mutational burdens, intrinsic and acquired resistance, lack of selectivity and adverse effects on a growing organism.

A Review of the Regulatory Mechanisms of N-Myc on Cell Cycle

Neuroblastoma has obvious heterogeneity. It is one of the few undifferentiated malignant tumors that can spontaneously degenerate into completely benign tumors. However, for its high-risk type, even with various intensive treatment options, the prognosis is still unsatisfactory. At the same time, a large number of research data show that the abnormal amplification and high-level expression of the MYCN gene are positively correlated with the malignant progression, poor prognosis, and mortality of neuroblastoma. In this context, this article explores the role of the N-Myc, MYCN gene expression product on its target genes related to the cell cycle and reveals its regulatory network in promoting tumor proliferation and malignant progression. We hope it can provide ideas and direction for the research and development of drugs targeting N-Myc and its downstream target genes.

Plk1 Inhibitors and Abiraterone Synergistically Disrupt Mitosis and Kill Cancer Cells of Disparate Origin Independently of Androgen Receptor Signaling

Abiraterone is a standard treatment for metastatic castrate-resistant prostate cancer (mCRPC) that slows disease progression by abrogating androgen synthesis and antagonizing the androgen receptor (AR). Here we report that inhibitors of the mitotic regulator polo-like kinase-1 (Plk1), including the clinically active third-generation Plk1 inhibitor onvansertib, synergizes with abiraterone in vitro and in vivo to kill a subset of cancer cells from a wide variety of tumor types in an androgen-independent manner. Gene-expression analysis identified an AR-independent synergy-specific gene set signature upregulated upon abiraterone treatment that is dominated by pathways related to mitosis and the mitotic spindle. Abiraterone treatment alone caused defects in mitotic spindle orientation, failure of complete chromosome condensation, and improper cell division independently of its effects on AR signaling. These effects, although mild following abiraterone monotherapy, resulted in profound sensitization to the antimitotic effects of Plk1 inhibition, leading to spindle assembly checkpoint-dependent mitotic cancer cell death and entosis. In a murine patient-derived xenograft model of abiraterone-resistant metastatic castration-resistant prostate cancer (mCRPC), combined onvansertib and abiraterone resulted in enhanced mitotic arrest and dramatic inhibition of tumor cell growth compared with either agent alone. Overall, this work establishes a mechanistic basis for the phase II clinical trial (NCT03414034) testing combined onvansertib and abiraterone in mCRPC patients and indicates this combination may have broad utility for cancer treatment.

SIGNIFICANCE

Abiraterone treatment induces mitotic defects that sensitize cancer cells to Plk1 inhibition, revealing an AR-independent mechanism for this synergistic combination that is applicable to a variety of cancer types.

Kinase PLK1 regulates the disassembly of the lateral elements and the assembly of the inner centromere during the diakinesis/metaphase I transition in male mouse meiosis

PLK1 is a serine/threonine kinase with crucial roles during mitosis. However, its involvement during mammalian male meiosis remains largely unexplored. By inhibiting the kinase activity of PLK1 using BI 2536 on organotypic cultures of seminiferous tubules, we found that the disassembly of SYCP3 and HORMAD1 from the lateral elements of the synaptonemal complex during diakinesis is impeded. We also found that the normal recruitment of SYCP3 and HORMAD1 to the inner centromere in prometaphase I spermatocytes did not occur. Additionally, we analyzed the participation of PLK1 in the assembly of the inner centromere by studying its implication in the Bub1-H2AT120ph-dependent recruitment of shugoshin SGO2, and the Haspin-H3T3ph-dependent recruitment of Aurora B/C and Borealin. Our results indicated that both pathways are regulated by PLK1. Altogether, our results demonstrate that PLK1 is a master regulator of the late prophase I/metaphase I transition in mouse spermatocytes.

Non-coding RNAs in human health and disease: potential function as biomarkers and therapeutic targets

Human diseases have been a critical threat from the beginning of human history. Knowing the origin, course of action and treatment of any disease state is essential. A microscopic approach to the molecular field is a more coherent and accurate way to explore the mechanism, progression, and therapy with the introduction and evolution of technology than a macroscopic approach. Non-coding RNAs (ncRNAs) play increasingly important roles in detecting, developing, and treating all abnormalities related to physiology, pathology, genetics, epigenetics, cancer, and developmental diseases. Noncoding RNAs are becoming increasingly crucial as powerful, multipurpose regulators of all biological processes. Parallel to this, a rising amount of scientific information has revealed links between abnormal noncoding RNA expression and human disorders. Numerous non-coding transcripts with unknown functions have been found in addition to advancements in RNA-sequencing methods. Non-coding linear RNAs come in a variety of forms, including circular RNAs with a continuous closed loop (circRNA), long non-coding RNAs (lncRNA), and microRNAs (miRNA). This comprises specific information on their biogenesis, mode of action, physiological function, and significance concerning disease (such as cancer or cardiovascular diseases and others). This study review focuses on non-coding RNA as specific biomarkers and novel therapeutic targets.

Multiple Roles of PLK1 in Mitosis and Meiosis

Cells are equipped with a diverse network of signaling and regulatory proteins that function as cell cycle regulators and checkpoint proteins to ensure the proper progression of cell division. A key regulator of cell division is polo-like kinase 1 (PLK1), a member of the serine/threonine kinase family that plays an important role in regulating the mitotic and meiotic cell cycle. The phosphorylation of specific substrates mediated by PLK1 controls nuclear envelope breakdown (NEBD), centrosome maturation, proper spindle assembly, chromosome segregation, and cytokinesis. In mammalian oogenesis, PLK1 is essential for resuming meiosis before ovulation and for establishing the meiotic spindle. Among other potential roles, PLK1 regulates the localized translation of spindle-enriched mRNAs by phosphorylating and thereby inhibiting the translational repressor 4E-BP1, a downstream target of the mTOR (mammalian target of rapamycin) pathway. In this review, we summarize the functions of PLK1 in mitosis, meiosis, and cytokinesis and focus on the role of PLK1 in regulating mRNA translation. However, knowledge of the role of PLK1 in the regulation of meiosis remains limited.

Biodegradable Carbon Dioxide-Derived Non-Viral Gene Vectors for Osteosarcoma Gene Therapy

Osteosarcoma often occurs in children and adolescents with high invasiveness and high mortality. Polo-like kinase 1 (PLK1) overexpressed in most tumors promotes cancer cell proliferation and transformation. PLK1 is considered as a therapeutic target for osteosarcoma. RNA interference-based therapies are employed to combat osteosarcoma through silencing PLK1 gene expression. However, the treatment results remain unsatisfactory due to the lack of a safe and efficient nonviral gene vector. To tackle this hurdle, biodegradable and CO₂ -derivative cationic poly(vinylcyclohexene carbonates) (CPCHCs) are used as gene vectors to perform a siPLK1 therapeutic strategy for osteosarcoma treatment. Of those CPCHCs, CPCHC60 demonstrates the most excellent performance in gene transfection efficiency, endo-lysosome escaping, biodegradability, and biosafety. With the treatment of CPCHCs/siRNA nanoparticles, the expression level of PLK1 gene in osteosarcoma cells is significantly down-regulated. Subsequently, cells are arrested in the G₂ /M phase and subsequently dead in the form of apoptosis, resulting in significant tumor regression both in vitro and in vivo. This study brings a new insight into the development of superior nonviral gene vectors for practical cancer treatment. Based on the results, the resulting nanoparticle-based gene drug formation is considered to have a highly successful chance in further translational nanomedicine applications.

Virtual screening of natural compounds as selective inhibitors of polo-like kinase-1 at C-terminal polo box and N-terminal catalytic domain

The over-expression of Polo-like kinase-1 (PLK1) is associated with cancer prognosis due to its pivotal role in cell proliferation. The N-terminal catalytic domain (NCD) and C-terminal polo box domain (PBD) of PLK1 are critical for the activity of the protein. Drugs that inhibit PLK1 by targeting these domains are on clinical trials, but so far, none has been approved by FDA. Thus, this study targets the two domains of PLK1 to identify compounds with inhibitory potential. Four validated e-pharmacophore models from NCD (PDB ID: 2OU7 and 4J52) and PBD (PDB ID: 5NEI and 5NN2) were used to screen over 26,000 natural compounds from NPASS database. Hits were identified after the well-fitted compounds were subjected to molecular docking study and ADME prediction. The pIC50 and electronic behaviour of the identified hits selectively targeting NCD and PBD of PLK1 were predicted via an externally validated QSAR model and quantum mechanics. The results showed that CAA180504, CAA197326, CAA74619, CAA328856 modulating PLK1 at NCD, and CBB130581, CBB230713, CBB206123, CBB12656 and CBB267117 modulating PLK1 at PBD had better molecular docking scores, pharmacokinetics and drug-like properties than NCD (volasertib) and PBD (purpurogallin) reference inhibitors. The compounds all had satisfactory inhibitory (pIC50) values which range from 6.187 to 7.157. The electronic behaviours of understudied compounds using HOMO/LUMO and global descriptive parameters revealed the atomic portion of the compounds prone to donating and accepting electrons. In conclusion, the hit compounds identified from the library of natural compounds are worthy of further experimental validation.Communicated by Ramaswamy H. Sarma.

Common Markers and Small Molecule Inhibitors in Golgi Studies

In this chapter, we provide a detailed guide for the application of commonly used small molecules to study Golgi structure and function in vitro. Furthermore, we have curated a concise, validated list of endomembrane markers typically used in downstream assays to examine the consequent effect on the Golgi via microscopy and western blot after drug treatment. This chapter will be useful for researchers beginning their foray into the field of intracellular trafficking and Golgi biology.