Present and Future Perspective on PLK1 Inhibition in Cancer Treatment

Discovery of a novel PLK1 inhibitor with high inhibitory potency using a combined virtual screening strategy

PLK1 is essential for cell cycle regulation and proliferation, and its elevated expression in prostate cancer is associated with high tumour grade. Therefore, PLK1 inhibition is considered a promising strategy for the treatment of prostate cancer. Here, we identified five compounds (Hits 1-5) targeting the kinase domain (KD) of PLK1 using a combined virtual screening approach. Hits 1-5 all had picomolar (pM) inhibitory potency against PLK1. Notably, Hit-4 showed the strongest inhibitory activity against PLK1 (IC50 = 22.61 ± 1.12 pM) and displayed high selectivity for PLK1. Meanwhile, molecular dynamics (MD) simulations revealed that the complex formed by Hit-4 and PLK1 remained stable. Importantly, Hit-4 exhibited potent inhibitory effects on the proliferation of DU-145 prostate cancer cells (IC50 = 0.09 ± 0.01 nM). In conclusion, Hit-4 is a potent and highly selective antitumor candidate with therapeutic potential for prostate cancer.

Differential Response and Resistance to KRAS-Targeted Therapy

KRAS is the most frequently mutated oncogene. In epithelial malignancies such as lung, colorectal, and pancreatic tumors, KRAS is mutated in 25 to above 90% cases. KRAS was considered undruggable for over three decades until the recent development of covalent inhibitors targeting the KRAS G12C mutant. The recent approval of the KRAS G12C inhibitors sotorasib and adagrasib has ushered in a new era of KRAS-targeted therapy. Despite this success, a major challenge in KRAS-targeted therapy is intrinsic and acquired resistance to KRAS inhibitors. Clinical studies have shown that many patients with KRAS G12C cancers did not respond to sotorasib and adagrasib. Colorectal cancer, in particular, has a markedly lower response rate to KRAS G12C inhibitors compared to non-small cell lung cancer. Furthermore, the therapeutic response to KRAS G12C inhibition was short-lived, with quick emergence of acquired resistance. In this review, we summarize several major themes that have emerged from recent clinical and preclinical studies on the mechanisms of intrinsic and acquired resistance to KRAS-targeted therapy in colorectal, lung, and pancreatic cancers. We also discuss various combination strategies for targeting these mechanisms to overcome resistance to KRAS inhibitors.

Optimizing Peptide-Conjugated Lipid Nanoparticles for Efficient siRNA Delivery across the Blood-Brain Barrier and Treatment of Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is a WHO grade 4 glioma and the most common malignant primary brain tumor. Addressing the clinical management of GBM presents an exceptionally daunting and intricate challenge, particularly in overcoming the blood-brain barrier (BBB) to deliver effective therapies to the brain. Nanotechnology-based drug delivery systems have exhibited considerable promise in tackling this aggressive brain cancer. However, the BBB remains a key challenge in achieving effective brain delivery of nanocarriers. Here, we have optimized a lipid nanoparticle (LNP) formulation (C2) and modified the LNP with Angiopep-2 peptide, which exhibits the most significant improvements in blood-brain barrier penetration and brain accumulation (about 2.23% injection dose). Using the Ang-2-coupled C2 LNP formulation, we researched the therapeutic effect of Polo-like Kinase 1(PLK1)-targeted siRNA delivery to treat a mouse model of GBM. The optimized LNP formulation was demonstrated to significantly inhibit mouse GBM growth and extend the median survival of mice (2.18-fold). This work demonstrates the efficacy of a brain-targeted siRNA delivery system in GBM treatment. As the understanding of the role of RNAs in GBM deepens and innovative delivery methods are continually developed and refined, RNA-based therapies could emerge as a crucial breakthrough in the advancement of brain tumor treatment.

Targeting PLK1-CBX8-GPX4 axis overcomes BRAF/EGFR inhibitor resistance in BRAFV600E colorectal cancer via ferroptosis

Metastatic BRAFV600E colorectal cancer (CRC) confers poor prognosis and represents a therapeutic bottleneck. To identify resistance mechanisms of the mitogen-activated protein kinase (MAPK) pathway in BRAFV600E CRC, we perform genome-wide CRISPR-Cas9 screening and discover that targeting glutathione peroxidase 4 (GPX4) overcomes resistance to BRAF inhibitor (BRAFi) combined with or without epidermal growth factor receptor inhibitor (EGFRi) in BRAFV600E CRC. Specifically, BRAFi ± EGFRi upregulates GPX4 expression, which antagonizes therapy-induced ferroptosis. Moreover, polo-like kinase 1 (PLK1) substrate activation promotes PLK1 translocation to the nucleus, activating chromobox protein homolog 8 (CBX8) phosphorylation at Ser265 to drives GPX4 expression. Targeting PLK1 enhances BRAFi ± EGFRi inhibition and triggers ferroptosis in vitro, vivo, organoid, and patient-derived xenograft model. Collectively, we demonstrate a PLK1-CBX8-GPX4 signaling axis that relays the ferroptosis mechanism of therapeutic resistance and propose a clinically actionable strategy to overcome BRAFi ± EGFRi resistance in BRAFV600E CRC.

PLK1 Inhibition Induces Synthetic Lethality in Fanconi Anemia Pathway-Deficient Acute Myeloid Leukemia

SIGNIFICANCE

This work demonstrates that FA pathway mutations, which are frequently observed in sporadic AML, induce hypersensitivity to PLK1 inhibition, providing rationale for a novel synthetic lethal therapeutic strategy for this patient population.

Onvansertib exhibits anti-proliferative and anti-invasive effects in endometrial cancer

Polo-like kinase 1 (Plk1) is widely recognized as an oncogene that promotes cell proliferation by regulating cell division, DNA damage response, and genome stability and has been shown to be overexpressed in many cancers, including endometrial cancer. Targeting Plk1 by onvansertib has been shown to have anti-tumor activity in pre-clinical models of multiple cancers and is currently being evaluated in phase 1 and 2 clinical trials in cancer patients. In this study, we evaluated the potential anti-tumorigenic effects of onvansertib in endometrial cancer cells and the LKB1fl/fl p53fl/fl mouse model of endometrial cancer. Onvansertib inhibited cellular proliferation, caused G2 phase arrest, induced cellular stress and apoptosis, and inhibited cellular migration and invasion in endometrial cancer cells. Combined treatment with onvansertib and paclitaxel led to synergistic inhibition of cell proliferation. Onvansertib treatment for 4 weeks significantly reduced tumor growth in LKB1fl/flp53fl/fl mice. Given these promising pre-clinical results, further studies are needed to evaluate the clinical translatability of onvansertib combined with paclitaxel as an effective treatment for endometrial cancer.

Druggable upregulated proteins in EWS-FLI-driven Ewing sarcoma as emerging new therapeutic targets

Ewing sarcoma (ES) is a highly aggressive soft tissue tumor that primarily affects the long bones of children and young adults. It is distinguished by a characteristic chromosomal translocation between the Ewing sarcoma breakpoint region 1 (EWS) gene and the erythroblast transformation-specific (ETS) family of genes, most commonly resulting in the EWS-friend leukemia integration 1 (EWS-FLI1) fusion gene. This translocation is observed in approximately 80%-85% of ES cases. This fusion gene encodes a non-physiological chimeric fusion protein that plays a central role in tumorigenesis by interacting with numerous partner proteins. Several studies have demonstrated the tumorigenic potential of the EWS-FLI1 protein when transfected into non-cancer cell lines. However, targeting EWS-FLI1 directly remains a significant challenge, as no drug to date has been reported to bind to and inhibit its activity effectively. An alternative therapeutic strategy involves targeting key overexpressed protein complexes implicated in ES tumorigenesis, many of which may be downstream interacting partners of EWS-FLI1. This review explores emerging protein targets as potential therapeutic avenues in ES treatment.

Transcriptome Analysis of Canine Histiocytic Sarcoma Tumors and Cell Lines Reveals Multiple Targets for Therapy

Background: Histiocytic sarcoma (HS) is a highly aggressive malignancy characterized by the excessive proliferation of histiocytes in dogs and humans. A subset of dog breeds, including the Bernese Mountain Dog (BMD), show a remarkably high prevalence of HS. Previous work by us and others has identified somatic driver mutations of HS in the PTPN11 and KRAS genes that activate the MAPK pathway in about 60% of canine HS. However, no somatic driver mutations have been identified in the remaining 40%. Objectives: Our goals are to study HS in BMDs to gain insight into the molecular pathogenesis of the disease, and identify rational approaches to therapy. Methods: Here, we report our whole transcriptome analysis of 18 well-characterized BMD HS tumor tissues, as well as three HS cell lines. Results: Our analysis reveals the significant upregulation of molecular pathways involving the FOXM1, AURKB, PLK1, and E2F genes, in HS as well as hemophagocytic HS, providing new information regarding pathways that may be targeted with inhibitors. In addition, we document the expression of multiple checkpoint genes, suggesting the option of treatment with small-molecule inhibitors together with checkpoint inhibitors. Further, we show that the transcriptomes of three canine HS cell lines mirror those of canine patient tumors, further highlighting their potential use in drug discovery and efficacy studies. Finally, we demonstrate, for the first time, that aurora kinase inhibitors are effective in curtailing the growth of HS cells in vitro and show synergism with MAPK inhibition. Conclusions: This study provides the most detailed analysis of the canine HS transcriptome to date, highlighting key pathways in its pathogenesis and suggesting new avenues for both single and combination treatment strategies, which may be pertinent to the treatment of human HS.

Accelerating discovery of bioactive ligands with pharmacophore-informed generative models

Deep generative models have advanced drug discovery but often generate compounds with limited structural novelty, providing constrained inspiration for medicinal chemists. To address this, we develop TransPharmer, a generative model that integrates ligand-based interpretable pharmacophore fingerprints with a generative pre-training transformer (GPT)-based framework for de novo molecule generation. TransPharmer excels in unconditioned distribution learning, de novo generation, and scaffold elaboration under pharmacophoric constraints. Its unique exploration mode could enhance scaffold hopping, producing structurally distinct but pharmaceutically related compounds. Its efficacy is validated through two case studies involving the dopamine receptor D2 (DRD2) and polo-like kinase 1 (PLK1). Notably, three out of four synthesized PLK1-targeting compounds show submicromolar activities, with the most potent, IIP0943, exhibiting a potency of 5.1 nM. Featuring a new 4-(benzo[b]thiophen-7-yloxy)pyrimidine scaffold, IIP0943 also has high PLK1 selectivity and submicromolar inhibitory activity in HCT116 cell proliferation. TransPharmer offers a promising tool for discovering structurally novel and bioactive ligands.

Mitochondrial signatures shape phenotype switching and apoptosis in response to PLK1 inhibitors

PLK1 inhibitors are emerging anticancer agents that are being tested as monotherapy and combination therapies for various cancers. Although PLK1 inhibition in experimental models has shown potent antitumor effects, translation to the clinic has been hampered by low antitumor activity and tumor relapse. Here, we report the identification of mitochondrial protein signatures that determine the sensitivity to approaches targeting PLK1 in human melanoma cell lines. In response to PLK1 inhibition or gene silencing, resistant cells adopt a pro-inflammatory and dedifferentiated phenotype, whereas sensitive cells undergo apoptosis. Mitochondrial DNA depletion and silencing of the ABCD1 transporter sensitize cells to PLK1 inhibition and attenuate the associated pro-inflammatory response. We also found that nonselective inhibitors of the p90 ribosomal S6 kinase (RSK) exert their antiproliferative and pro-inflammatory effects via PLK1 inhibition. Specific inhibition of RSK, on the other hand, is anti-inflammatory and promotes a program of antigen presentation. This study reveals the overlooked effects of PLK1 on phenotype switching and suggests that mitochondrial precision medicine can help improve the response to targeted therapies.

Cyclin E1 overexpression sensitizes ovarian cancer cells to WEE1 and PLK1 inhibition

Cyclin E1 (CCNE1) amplification is associated with poor prognosis of ovarian carcinomas across histological subtypes. Inhibitors targeting PLK1 or WEE1 are emerging as promising therapeutic agents for cancer treatment that disrupt the critical G2/M checkpoint, leading to cancer cell death. However, biomarkers that predict the response to these inhibitors are not well defined. Here, we evaluated the efficacy of the PLK1 inhibitor, volasertib, and the WEE1 inhibitor, adavosertib, along with the biomarker potential of cyclin E1 in ovarian cancer cells. Both inhibitors suppressed the proliferation of cyclin E1-overexpressing cells to a greater extent than that of cells exhibiting low cyclin E1 expression. TP53 silencing did not increase the sensitivity to these inhibitors. In cyclin E1-overexpressing cells, PLK1 inhibition reduced the proportion of cells in the G1 phase and increased those in the G2/M and sub-G1 phases. WEE1 inhibition reduced G1 phase cells without a clear peak in the S-G2/M phase and increased the sub-G1 phase cells. Both inhibitors suppressed the growth of cyclin E1-overexpressing tumors in vivo. Taken together, cyclin E1 overexpression, regardless of TP53 status, may serve as a predictive biomarker for the efficacy of these inhibitors, offering potential personalized treatment strategies for ovarian cancer.

MYC and HSF1 Cooperate to Drive Sensitivity to Polo-like Kinase 1 Inhibitor Volasertib in High-grade Serous Ovarian Cancer

SIGNIFICANCE

We show that HSF1 and MYC genes are co-amplified in more than 30% of HGSOC and demonstrate that HSF1 and MYC functionally cooperate to drive the growth of HGSOC cells. This work provides the foundation for HSF1 and MYC co-amplification as a biomarker for treatment efficacy of the polo-like kinase 1 inhibitor volasertib in HGSOC.

Conservation of OFD1 Protein Motifs: Implications for Discovery of Novel Interactors and the OFD1 Function

OFD1 is a protein involved in many cellular processes, including cilia biogenesis, mitotic spindle assembly, translation, autophagy and the repair of double-strand DNA breaks. Despite many potential interactors identified in high-throughput studies, only a few have been directly confirmed with their binding sites identified. We performed an analysis of the evolutionary conservation of the OFD1 sequence in three clades: 80 Tetrapoda, 144 Vertebrata or 26 Animalia species, and identified 59 protein-binding motifs localized in the OFD1 regions conserved in various clades. Our results indicate that OFD1 contains 14 potential post-translational modification (PTM) sites targeted by at least eight protein kinases, seven motifs bound by proteins recognizing phosphorylated aa residues and a binding site for phosphatase 2A. Moreover, OFD1 harbors both a motif that enables its phosphorylation by mitogen-activated protein kinases (MAPKs) and a specific docking site for these proteins. Generally, our results suggest that OFD1 forms a scaffold for interaction with many proteins and is tightly regulated by PTMs and ligands. Future research on OFD1 should focus on the regulation of OFD1 function and localization.

Upregulation of phosphatase and tensin homolog deleted on chromosome ten inhibits lung cancer cell proliferation by suppressing the oncogene polo-like kinase 1 and inducing autophagy

Objective

Lung cancer is one of the main causes of cancer-related mortality globally, and it poses considerable therapeutic challenges. Polo-like kinase 1 (PLK1) exhibits upregulation in lung cancer, and PLK1 silencing promotes autophagy in lung cancer cells, which inhibits tumor progression. The phosphatase and tensin homolog deleted on chromosome ten (PTEN) acts as a tumor suppressor gene. This study aimed to investigate whether PTEN regulates autophagy and inhibits lung cancer-cell proliferation by suppressing PLK1.

Material and Methods

In this study, we evaluated cell proliferation by silencing or overexpressing PLK1 and PTEN in A549 cells through 5-ethynyl-2'-deoxyuridine labeling and cloning experiments. The autophagy levels were detected through transmission electron microscopy, real-time quantitative polymerase chain reaction, and Western blot. Finally, the results of in vitro experiment were further verified using an in vivo xenograft tumor animal model.

Results

The upregulation of PTEN suppressed PLK1 expression in lung cancer cells and reduced their proliferation rate. In addition, the overexpression of PTEN has been associated with the growth of lung cancer tumors. In parallel, the levels of autophagy of lung cancer cells rose in response to PTEN upregulation in vivo and in vitro.

Conclusion

This study revealed that PTEN promotes the autophagy of lung cancer cells and inhibits cell proliferation and tumor growth by suppressing PLK1 expression. This finding provides a new strategy for lung cancer treatment by utilizing the autophagy-regulating effect of PTEN to inhibit lung cancer growth by targeting PLK1.

Onvansertib and Navitoclax Combination as a New Therapeutic Option for Mucinous Ovarian Carcinoma

Mucinous epithelial ovarian cancer (mEOC) is a rare subtype of epithelial ovarian cancer, characterized by poor responses to standard platinum-based chemotherapy. Polo-like kinase 1 (PLK1) is a key regulator of mitosis and cell cycle progression and its inhibition has been recently identified as a target in mEOC. In this study, we aimed to identify further therapeutic targets in mEOC using a CRISPR/Cas9 library targeting 3015 genes, with and without treatment with onvansertib, a PLK1 inhibitor. We identified twelve genes associated with cell survival (ZC2HC1C, RPA2, KIN17, TUBG1, SMC2, CDC26, CDC42, HOXA9, TAF10, SENP1, MRPS31, and COPS2) and three genes (JUND, CARD9, and BCL2L2) in synthetic lethality with onvansertib treatment. We validated that SENP1 downregulation is important for the growth of mEOC cells through esiRNA interference and the use of a pharmacological inhibitor Momordin Ic. The downregulation of CARD9 and BCL2L2 combined with subtoxic doses of onvansertib interfered with mEOC cell growth. Interestingly, the combination of navitoclax, an inhibitor of BcL2 family members including BCL2L2, was synergistic in all four of the mEOC cell lines tested and substantially induced cell death through apoptosis. These data support the use of a combination of navitoclax and onvansertib as a new therapeutic strategy for mEOC.

Polo-like Kinase 1 Expression as a Biomarker in Colorectal Cancer: A Retrospective Two-Center Study

Background/Objectives: Early-onset colorectal cancer (EOCRC) is more frequently characterized by poorly differentiated, aggressive tumors, often diagnosed at advanced stages, and associated with worse prognoses. Despite these differences, current treatment guidelines do not distinguish between EOCRC and late-onset colorectal cancer (LOCRC). Elevated expression of polo-like kinase 1 (PLK-1) has been linked to advanced disease stages and poorer treatment outcomes, including resistance to both chemotherapy and radiotherapy. However, data on PLK-1 expression in EOCRC compared to LOCRC remain limited. Methods: Patients with sporadic CRC, aged >18 years, were included in this study. We categorized the patients into two groups: patients younger than 50 years, and those aged 50 years or older. Immunohistochemical staining was performed to assess PLK-1 expression. The aim of this study was to assess PLK-1 expression considering the age of the patients and its effects on overall survival (OS) and progression-free survival (PFS). Results: A total of 146 patients with metastatic colorectal cancer (mCRC) were included in this retrospective two-center study. Patients with low PLK-1 expression were older than patients with high PLK-1 expression (64 (49-71) years vs. 49 (42-67) years, p = 0.016). Multiple logistic regression confirmed that age is a significant predictor of PLK-1 expression, independent of the covariates (p = 0.036). The Kaplan-Meier analysis revealed no significant association between PLK-1 expression and PFS (p = 0.397) or OS (p = 0.448). Accordingly, Cox proportional hazards regression analysis showed no significant association between PLK-1 expression and OS (HR 1.20, 95% CI 0.73-1.96, p = 0.598) or PFS (HR 0.85, 95% CI 0.51-1.43, p = 0.611) when covariates were taken into account. Finally, no significant differences in PFS (p = 0.423) or OS (p = 0.104) were found between the age groups of interest. Conclusions: PLK-1 expression was not associated with survival or progression in EOCRC and LOCRC patients. Further research on these combinations is necessary, as well as the discovery of new potential targets for targeted therapy and the mechanisms of synergistic effects in tumors with PLK-1 overexpression.

Integrative analysis of anoikis-related genes prognostic signature with immunotherapy and identification of CDKN3 as a key oncogene in lung adenocarcinoma

Anoikis, a form of programmed cell death induced by loss of cell contact, is closely associated with tumor invasion and metastasis, making it highly significant in lung cancer research. We examined the expression patterns and prognostic relevance of Anoikis-related genes (ARGs) in lung adenocarcinoma (LUAD) using the TCGA-LUAD database. This study identified molecular subtypes associated with Anoikis in LUAD and conducted functional enrichment analyses. We constructed an ARG risk score using univariate least absolute shrinkage and selection operator (LASSO) Cox regression, validated externally with GEO datasets and clinical samples. The clinical applicability of the prognostic model was evaluated using nomograms, calibration curves, decision curve analysis (DCA), and time-dependent AUC assessments. We identified four prognostically significant genes (PLK1, SLC2A1, CDKN3, PHLDA2) and two ARG-related molecular subtypes. ARGs were generally upregulated in LUAD and correlated with multiple pathways including the cell cycle and DNA replication. The prognostic model indicated that the low-risk group had better outcomes and significant correlations with clinicopathological features, tumor microenvironment, immune therapy responses, drug sensitivity, and pan-RNA epigenetic modification-related genes. Patients with low-risk LUAD were potential beneficiaries of immune checkpoint inhibitor (ICI) therapy. Prognostic ARGs' distribution and expression across various immune cell types were further analyzed using single-cell RNA sequencing. The pivotal role of CDKN3 in LUAD was confirmed through qRT-PCR and gene knockout experiments, demonstrating that CDKN3 knockdown inhibits tumor cell proliferation, migration, and invasion. Additionally, we constructed a ceRNA network involving CDKN3/hsa-miR-26a-5p/SNHG6, LINC00665, DUXAP8, and SLC2A1/hsa-miR-218-5p/RNASEH1-AS1, providing new insights for personalized and immune therapy decisions in LUAD patients.

Polo-like kinase 2 targeting as novel strategy to sensitize mutant p53-expressing tumor cells to anticancer treatments

Polo-like kinase 2 (Plk2) belongs to a family of serine/threonine kinases, and it is involved in tumorigenesis of diverse kind of tissues. We previously reported that Plk2 gene was a transcriptional target of the mutant p53/NF-Y oncogenic complex. Plk2 protein can bind to and phosphorylate mutant p53 triggering an oncogenic autoregulatory feedback loop involved in cancer cell proliferation and chemoresistance. In this study, we aimed to assess whether the specific inhibition of Plk2 kinase activity by the selective TC-S 7005 inhibitor could decrease cell proliferation and migration inhibiting mutant p53 phosphorylation, thus disarming its oncogenic potential. We found that the Plk2 inhibitor treatment sensitized the cells to the irradiation and chemotherapy drugs, thereby overcoming the mutant p53-dependent chemoresistance. Taken together, we provided results that Plk2 could be considered a tractable pharmacological target for cancers expressing mutant p53 proteins. The combined treatment with conventional chemotherapeutic drugs and Plk2 inhibitors may represent a new candidate intervention approach, which may be considered for improving tumor cell sensitivity to DNA damaging drugs. KEY MESSAGES : Missense mutations are present in the TP53 gene in about half of all human cancers and correlate with poor patient outcome. Mutant p53 proteins exert gain of function (GOF) activities in tumor cells such as increased proliferation, genomic instability and resistance to therapies. Polo-like kinase 2 (PLK2) binds and phosphorylates mutant p53 protein strengthening its GOF activities. Pharmacologically targeting PLK2 weakens mutant p53 proteins and sensitizes tumor cells to therapeutic treatments.

Ultrasound Control of Genomic Regulatory Toolboxes for Cancer Immunotherapy

There remains a critical need for the precise control of CRISPR (clustered regularly interspaced short palindromic repeats)-based technologies. Here, we engineer a set of inducible CRISPR-based tools controllable by focused ultrasound (FUS), which can penetrate deep and induce localized hyperthermia for transgene activation. We demonstrate the capabilities of FUS-inducible CRISPR, CRISPR activation (CRISPRa), and CRISPR epigenetic editor (CRISPRee) in modulating the genome and epigenome. We show that FUS-CRISPR-mediated telomere disruption primes solid tumours for chimeric antigen receptor (CAR)-T cell therapy. We further deliver FUS-CRISPR in vivo using adeno-associated viruses (AAVs), followed by FUS-induced telomere disruption and the expression of a clinically validated antigen in a subpopulation of tumour cells, functioning as "training centers" to activate synthetic Notch (synNotch) CAR-T cells to produce CARs against a universal tumour antigen to exterminate neighboring tumour cells. The FUS-CRISPR(a/ee) toolbox hence allows the noninvasive and spatiotemporal control of genomic/epigenomic reprogramming for cancer treatment.

Application of Fluorescence- and Bioluminescence-Based Biosensors in Cancer Drug Discovery

Recent advances in drug discovery have established biosensors as indispensable tools, particularly valued for their precision, sensitivity, and real-time monitoring capabilities. The review begins with a brief overview of cancer drug discovery, underscoring the pivotal role of biosensors in advancing cancer research. Various types of biosensors employed in cancer drug discovery are then explored, with particular emphasis on fluorescence- and bioluminescence-based technologies such as FRET, TR-FRET, BRET, NanoBRET, and NanoBiT. These biosensors have enabled breakthrough discoveries, including the identification of Celastrol as a novel YAP-TEAD inhibitor through NanoBiT-based screening, and the development of TR-FRET assays that successfully identified Ro-31-8220 as a SMAD4R361H/SMAD3 interaction inducer. The integration of biosensors in high throughput screening and validation for cancer drug compounds is examined, highlighting successful applications such as the development of LATS biosensors that revealed VEGFR as an upstream regulator of the Hippo signaling pathway. Real-time monitoring of cellular responses through biosensors has yielded invaluable insights into cancer cell signaling pathways, as demonstrated by NanoBRET assays detecting RAF dimerization and HiBiT systems monitoring protein degradation dynamics. The review addresses challenges linked to biosensor applications, such as maintaining stability in complex tumor microenvironments and achieving consistent sensitivity in HTS applications. Emerging trends are discussed, including integrating artificial intelligence and advanced nanomaterials for enhanced biosensor performance. In conclusion, this review offers a comprehensive analysis of fluorescence- and bioluminescence-based biosensor applications in the dynamic cancer drug discovery field, presenting quantitative evidence of their impact and highlighting their potential to revolutionize targeted cancer treatments.

Exploring the Target Genes of Fucosylated Chondroitin Sulfate in Treating Lung Adenocarcinoma Based on the Integration of Bioinformatics Analysis, Molecular Docking, and Experimental Verification

Fucosylated chondroitin sulfate (FCS), extracted from sea cucumbers' body walls, has been found to inhibit the proliferation of lung adenocarcinoma (LUAD) cells. However, there have been few studies of the associated drug targets. This study combined bioinformatics analysis and molecular docking to screen the main targets of FCS intervention in LUAD. Moreover, an experimental validation was performed. First, we downloaded the LUAD gene data set from The Cancer Genome Atlas (TCGA) database and the cisplatin (DDP) resistance gene data set of LUAD A549 cells from the Gene Expression Omnibus (GEO) database. Nine significant genes (PLK1, BUB1, CDK1, CDC20, CCNB1, BUB1B, KIF11, CCNB2, and DLAGP5) were identified by bioinformatics analysis, and these nine genes overlapped in both data sets. Then, molecular docking results showed that FCS had a better affinity with target proteins BUB1 and PLK1. Further experimental verification revealed that FCS inhibited the growth of A549 cells and increased the sensitivity of A549 cells to DDP. Quantitative real-time polymerase chain reaction (qRT-PCR) revealed that A549 cells treated with FCS exhibited down-regulated BUB1 and PLK1 mRNA expression. At the same time, FCS+DDP treatment resulted in a more significant reduction in BUB1 and PLK1 mRNA expression than DDP or FCS treatment alone. These findings reveal potential targets of FCS for LUAD and provide clues for the development of FCS as a potential anticancer agent.

Nanoparticles Bounded to Interfering RNAs as a Therapy for Pancreatic Cancer: A Systematic Review

Pancreatic cancer is one of the tumors with poor prognosis and low survival due to late diagnosis, high resistance, and very limited effective therapeutic options. Thus, new pharmacological treatments are necessary to improve the prognosis of patients. In this context, nanoparticles represent an efficient system for transporting and administering therapeutic molecules. Furthermore, siRNA can be used in cancer treatment to selectively inhibit the expression of any target gene. Therefore, nanoparticles associated with siRNA have been tested as a new therapeutic strategy to solve the pancreatic cancer treatment failure in the clinical setting. The current article presents a systematic revision of the literature of the last 10 years in which nanoparticles loading siRNA are used in pancreatic cancer. This research was carried out in three databases (PubMed, Scopus, and Web of Science) obtaining 164 articles from which 37 were selected. Our results show an overall view of the high effectiveness of this new therapy that combines nanoparticles with genetic therapy in pancreatic cancer suggesting that siRNA-based medicines will likely open up a new therapeutic era in the treatment of this type of tumors.

PLK1 Inhibitor Onvansertib Enhances the Efficacy of Alpelisib in PIK3CA-Mutated HR-Positive Breast Cancer Resistant to Palbociclib and Endocrine Therapy: Preclinical Insights

BACKGROUND

Endocrine therapy (ET) combined with cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) is the preferred first-line treatment for hormone receptor-positive (HR+)/HER2- metastatic breast cancer. Although this is beneficial, acquired resistance leads to disease progression, and patients harboring PIK3CA mutations are treated with targeted therapies such as the PI3Kα inhibitor, alpelisib, alongside ET. Drug-associated resistance mechanisms limit the efficacy of alpelisib, highlighting the need for better combination therapies. This study aimed to evaluate the efficacy of combining alpelisib with a highly specific PLK1 inhibitor, onvansertib, in PIK3CA-mutant HR+ breast cancer preclinical models.

METHODS

We assessed the effect of the alpelisib and onvansertib combination on cell viability, PI3K signaling pathway, cell cycle phase distribution and apoptosis in PI3K-activated HR+ breast cancer cell lines. The antitumor activity of the combination was evaluated in three PIK3CA-mutant HR+ breast cancer patient-derived xenograft (PDX) models, resistant to ET and CDK4/6 inhibitor palbociclib. Pharmacodynamics studies were performed using immunohistochemistry and Simple Western analyses in tumor tissues.

RESULTS

The combination synergistically inhibited cell viability, suppressed PI3K signaling, induced G2/M arrest and apoptosis in PI3K-activated cell lines. In the three PDX models, the combination demonstrated superior anti-tumor activity compared to the single agents. Pharmacodynamic studies confirmed the inhibition of both PLK1 and PI3K activity and pronounced apoptosis in the combination-treated tumors.

CONCLUSIONS

Our findings support that targeting PLK1 and PI3Kα with onvansertib and alpelisib, respectively, may be a promising strategy for patients with PIK3CA-mutant HR+ breast cancer failing ET + CDK4/6i therapies and warrant clinical evaluation.

Proteomic analysis reveals a PLK1-dependent G2/M degradation program and a role for AKAP2 in coordinating the mitotic cytoskeleton

Ubiquitination is an essential regulator of cell division. The kinase Polo-like kinase 1 (PLK1) promotes protein degradation at G2/M phase through the E3 ubiquitin ligase Skp1-Cul1-F box (SCF)βTrCP. However, the magnitude to which PLK1 shapes the mitotic proteome is uncharacterized. Combining quantitative proteomics with pharmacologic PLK1 inhibition revealed a widespread, PLK1-dependent program of protein breakdown at G2/M. We validated many PLK1-regulated proteins, including substrates of the cell-cycle E3 SCFCyclin F, demonstrating that PLK1 promotes proteolysis through at least two distinct E3 ligases. We show that the protein-kinase-A-anchoring protein A-kinase anchor protein 2 (AKAP2) is cell-cycle regulated and that its mitotic degradation is dependent on the PLK1/βTrCP signaling axis. Expression of a non-degradable AKAP2 mutant resulted in actin defects and aberrant mitotic spindles, suggesting that AKAP2 degradation coordinates cytoskeletal organization during mitosis. These findings uncover PLK1's far-reaching role in shaping the mitotic proteome post-translationally and have potential implications in malignancies where PLK1 is upregulated.

Dual TTK/PLK1 inhibition has potent anticancer activity in TNBC as monotherapy and in combination

Background

Threonine tyrosine kinase (TTK) and polo-like kinase 1 (PLK1) are common essential kinases that collaborate in activating the spindle assembly checkpoint (SAC) at the kinetochore, ensuring appropriate chromosome alignment and segregation prior to mitotic exit. Targeting of either TTK or PLK1 has been clinically evaluated in cancer patients; however, dual inhibitors have not yet been pursued. Here we present the in vitro and in vivo characterization of a first in class, dual TTK/PLK1 inhibitor (BAL0891).

Methods

Mechanism of action studies utilized biochemical kinase and proteomics-based target-engagement assays. Cellular end-point assays included immunoblot- and flow cytometry-based cell cycle analyses and SAC integrity evaluation using immunoprecipitation and immunofluorescence approaches. Anticancer activity was assessed in vitro using cell growth assays and efficacy was evaluated, alone and in combination with paclitaxel and carboplatin, using mouse models of triple negative breast cancer (TNBC).

Results

BAL0891 elicits a prolonged effect on TTK, with a transient activity on PLK1. This unique profile potentiates SAC disruption, forcing tumor cells to aberrantly exit mitosis with faster kinetics than observed with a TTK-specific inhibitor. Broad anti-proliferative activity was demonstrated across solid tumor cell lines in vitro. Moreover, intermittent intravenous single-agent BAL0891 treatment of the MDA-MB-231 mouse model of TNBC induced profound tumor regressions associated with prolonged TTK and transient PLK1 in-tumor target occupancy. Furthermore, differential tumor responses across a panel of thirteen TNBC patient-derived xenograft models indicated profound anticancer activity in a subset (~40%). Using a flexible dosing approach, pathologically confirmed cures were observed in combination with paclitaxel, whereas synergy with carboplatin was schedule dependent.

Conclusions

Dual TTK/PLK1 inhibition represents a novel approach for the treatment of human cancer, including TNBC patients, with a potential for potent anticancer activity and a favorable therapeutic index. Moreover, combination approaches may provide an avenue to expand responsive patient populations.

Exploring Predictive and Prognostic Biomarkers in Colorectal Cancer: A Comprehensive Review

Colorectal cancer (CRC) remains the second leading cause of cancer-related mortality worldwide. While immune checkpoint inhibitors have significantly improved patient outcomes, their effectiveness is mostly limited to tumors with microsatellite instability (MSI-H/dMMR) or an increased tumor mutational burden, which comprise 10% of cases. Advancing personalized medicine in CRC hinges on identifying predictive biomarkers to guide treatment decisions. This comprehensive review examines established tissue markers such as KRAS and HER2, highlighting their roles in resistance to anti-EGFR agents and discussing advances in targeted therapies for these markers. Additionally, this review summarizes encouraging data on promising therapeutic targets and highlights the clinical utility of liquid biopsies. By synthesizing current evidence and identifying knowledge gaps, this review provides clinicians and researchers with a contemporary understanding of the biomarker landscape in CRC. Finally, the review examines future directions and challenges in translating promising biomarkers into clinical practice, with the goal of enhancing personalized medicine approaches for colorectal cancer patients.

In Vitro and In Silico Studies on 4-Nitroacetophenone Thiosemicarbazone Potential Cytotoxicity Against A549 Cell Lines

Lung malignancy is a major worldwide issue that occurs due to the dysregulation of various growth factors. Lung cancer has no apparent signs in the early stages, which makes it harder to catch it in time and leads to a higher fatality rate. So, the goal of this work was to create and analyze a novel chemical molecule called 4-nitro acetophenone thiosemicarbazone (4-NAPTSc) against the lung cancer cell line A549 and human non-tumorigenic lung epithelial cell line BAES-2B. The ligand was synthesized by refluxing the reaction mixture of 4-nitro acetophenone and thiosemicarbazide and was further characterized by UV, FTIR, and 1H and 13C NMR and Differential Scanning Calorimetry (DSC) study. Cytotoxicity assay/MTT (3-(4,5-dimethylthiazol-2-yl))2,5-diphenyltetrazolium bromide) was used to evaluate the cytotoxicity of the compound. Epidermal growth factor receptors (EGFR), polo-like kinase-1 (PLK1), and vascular endothelial growth factor receptors (VEGFR) were chosen as the target proteins for molecular docking to find potential ligand binding sites and inhibit their function. A novel yellow-colored crystalline solid has been synthesized. 4-NAPTSc had an IC50 of 2.93 μg/mL against the A549 lung cancer cells. When the dosage is increased from 5 to 15 μg/mL along with time, the cell viability falls. Docking results showed that the compound binds with the targeted proteins' amino acid residues, and the likeness profile of the compound is also favorable. This study reveals that the compound has the potential for further investigation and can be used in multitargeted cancer therapies.

New Horizons of Synthetic Lethality in Cancer: Current Development and Future Perspectives

In recent years, synthetic lethality has been recognized as a solid paradigm for anticancer therapies. The discovery of a growing number of synthetic lethal targets has led to a significant expansion in the use of synthetic lethality, far beyond poly(ADP-ribose) polymerase inhibitors used to treat BRCA1/2-defective tumors. In particular, molecular targets within DNA damage response have provided a source of inhibitors that have rapidly reached clinical trials. This Perspective focuses on the most recent progress in synthetic lethal targets and their inhibitors, within and beyond the DNA damage response, describing their design and associated therapeutic strategies. We will conclude by discussing the current challenges and new opportunities for this promising field of research, to stimulate discussion in the medicinal chemistry community, allowing the investigation of synthetic lethality to reach its full potential.

Onvansertib treatment overcomes olaparib resistance in high-grade ovarian carcinomas

Occurrence of resistance to olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor (PARPi) approved in ovarian carcinoma, has already been shown in clinical settings. Identifying combination treatments to sensitize tumor cells and/or overcome resistance to olaparib is critical. Polo-like kinase 1 (PLK1), a master regulator of mitosis, is also involved in the DNA damage response promoting homologous recombination (HR)-mediated DNA repair and in the recovery from the G2/M checkpoint. We hypothesized that PLK1 inhibition could sensitize tumor cells to PARP inhibition. Onvansertib, a highly selective PLK1 inhibitor, and olaparib were tested in vitro and in vivo in BRCA1 mutated and wild-type (wt) ovarian cancer models, including patient-derived xenografts (PDXs) resistant to olaparib. The combination of onvansertib and olaparib was additive or synergic in different ovarian cancer cell lines, causing a G2/M block of the cell cycle, DNA damage, and apoptosis, much more pronounced in cells treated with the two drugs as compared to controls and single agents treated cells. The combined treatment was well tolerated in vivo and resulted in tumor growth inhibition and a statistically increased survival in olaparib-resistant-BRCA1 mutated models. The combination was also active, although to a lesser extent, in BRCA1 wt PDXs. Pharmacodynamic analyses showed an increase in mitotic, apoptotic, and DNA damage markers in tumor samples derived from mice treated with the combination versus vehicle. We could demonstrate that in vitro onvansertib inhibited both HR and non-homologous end-joining repair pathways and in vivo induced a decrease in the number of RAD51 foci-positive tumor cells, supporting its ability to induce HR deficiency and favoring the activity of olaparib. Considering that the combination was well tolerated, these data support and foster the clinical evaluation of onvansertib with PARPis in ovarian cancer, particularly in the PARPis-resistant setting.

Secondary Analysis of Human Bulk RNA-Seq Dataset Suggests Potential Mechanisms for Letrozole Resistance in Estrogen-Positive (ER+) Breast Cancer

Estrogen receptor-positive (ER+) breast cancer is common among postmenopausal women and is frequently treated with Letrozole, which inhibits aromatase from synthesizing estrogen from androgens. Decreased estrogen slows the growth of tumors and can be an effective treatment. The increase in Letrozole resistance poses a unique problem for patients. To better understand the underlying molecular mechanism(s) of Letrozole resistance, we reanalyzed transcriptomic data by comparing individuals who responded to Letrozole therapy (responders) to those who were resistant to treatment (non-responders). We identified SOX11 and S100A9 as two significant differentially expressed genes (DEGs) between these patient cohorts, with "PLK1 signaling events" being the most significant signaling pathway. We also identified PRDX4 and E2F8 gene products as being the top mechanistic transcriptional markers for ER+ treatment resistance. Many of the significant DEGs that we identified play a known role in ER+ breast cancer or other types of cancer, which partially validate our results. Several of the gene products we identified are novel in the context of ER+ breast cancer. Many of the genes that we identified warrant further research to elucidate the more specific molecular mechanisms of Letrozole resistance in this patient population and could potentially be used as prognostic markers with further wet lab validation. We anticipate that these findings could contribute to improved detection and therapeutic outcomes in aromatase-resistant ER+ breast cancer patients.

Targeting polo-like kinase 1 to treat kidney diseases

Globally, ∼850 million individuals suffer from some form of kidney disease. This staggering figure underscores the importance of continued research and innovation in the field of nephrology to develop effective treatments and improve overall global kidney health. In current research, the polo-like kinase (Plk) family has emerged as a group of highly conserved enzyme kinases vital for proper cell cycle regulation. Plks are defined by their N-terminal kinase domain and C-terminal polo-box domain, which regulate their catalytic activity, subcellular localization, and substrate recognition. Among the Plk family members, Plk1 has garnered significant attention due to its pivotal role in regulating multiple mitotic processes, particularly in the kidneys. It is a crucial serine-threonine (Ser-Thr) kinase involved in cell division and genomic stability. In this review, we delve into the types and functions of Plks, focusing on Plk1's significance in processes such as cell proliferation, spindle assembly, and DNA damage repair. The review also underscores Plk1's vital contributions to maintaining kidney homeostasis, elucidating its involvement in nuclear envelope breakdown, anaphase-promoting complex/cyclosome activation, and the regulation of mRNA translation machinery. Furthermore, the review discusses how Plk1 contributes to the development and progression of kidney diseases, emphasizing its overexpression in conditions such as acute kidney injury, chronic kidney disease, and so forth. It also highlights the importance of exploring Plk1 modulators as targeted therapies for kidney diseases in future. This review will help in understanding the role of Plk1 in kidney disease development, paving the way for the discovery and development of novel therapeutic approaches to manage kidney diseases effectively.

Mitotic kinases are emerging therapeutic targets against metastatic breast cancer

This review aims to outline mitotic kinase inhibitors' roles as potential therapeutic targets and assess their suitability as a stand-alone clinical therapy or in combination with standard treatments for advanced-stage solid tumors, including triple-negative breast cancer (TNBC). Breast cancer poses a significant global health risk, with TNBC standing out as the most aggressive subtype. Comprehending the role of mitosis is crucial for understanding how TNBC advances from a solid tumor to metastasis. Chemotherapy is the primary treatment used to treat TNBC. Some types of chemotherapeutic agents target cells in mitosis, thus highlighting the need to comprehend the molecular mechanisms governing mitosis in cancer. This understanding is essential for devising targeted therapies to disrupt these mitotic processes, prevent or treat metastasis, and improve patient outcomes. Mitotic kinases like Aurora kinase A, Aurora Kinase B, never in mitosis gene A-related kinase 2, Threonine-Tyrosine kinase, and Polo-kinase 1 significantly impact cell cycle progression by contributing to chromosome separation and centrosome homeostasis. When these kinases go awry, they can trigger chromosome instability, increase cell proliferation, and activate different molecular pathways that culminate in a transition from epithelial to mesenchymal cells. Ongoing clinical trials investigate various mitotic kinase inhibitors as potential biological treatments against advanced solid tumors. While clinical trials against mitotic kinases have shown some promise in the clinic, more investigation is necessary, since they induce severe adverse effects, particularly affecting the hematopoietic system.

MYC and HSF1 Cooperate to Drive PLK1 inhibitor Sensitivity in High Grade Serous Ovarian Cancer

Ovarian cancer is a deadly female cancer with high rates of recurrence. The primary treatment strategy for patients is platinum-based therapy regimens that almost universally develop resistance. Consequently, new therapeutic avenues are needed to overcome the plateau that current therapies have on patient outcomes. We describe a gene amplification involving both HSF1 and MYC, wherein these two genes on chromosome 8q are co-amplified in over 7% of human tumors that is enriched to over 30% of patients with ovarian cancer. We further found that HSF1 and MYC transcriptional activity is correlated in human tumors and ovarian cancer cell lines, suggesting they may cooperate in ovarian cancer cells. CUT&RUN for HSF1 and MYC in co-amplified ovarian cancer cells revealed that HSF1 and MYC have overlapping binding at a substantial number of locations throughout the genome where their binding peaks are near identical. Consistent with these data, a protein-protein interaction between HSF1 and MYC was detected in ovarian cancer cells, implying these two transcription factors have a molecular cooperation. Further supporting their cooperation, growth of HSF1-MYC co-amplified ovarian cancer cells were found to be dependent on both HSF1 and MYC. In an attempt to identify a therapeutic target that could take advantage of this dependency on both HSF1 and MYC, PLK1 was identified as being correlated with HSF1 and MYC in primary human tumor specimens, consistent with a previously established effect of PLK1 on HSF1 and MYC protein levels. Targeting PLK1 with the compound volasertib (BI-6727) revealed a greater than 200-fold increased potency of volasertib in HSF1-MYC co-amplified ovarian cancer cells compared to ovarian cancer cells wild-type HSF1 and MYC copy number, which extended to several growth assays, including spheroid growth. Volasertib, and other PLK1 inhibitors, have not shown great success in clinical trials and this study suggests that targeting PLK1 may be viable in a precision medicine approach using HSF1-MYC co-amplification as a biomarker for response.

Auranofin and reactive oxygen species inhibit protein synthesis and regulate the level of the PLK1 protein in Ewing sarcoma cells

Novel therapeutic approaches are needed for the treatment of Ewing sarcoma tumors. We previously identified that Ewing sarcoma cell lines are sensitive to drugs that inhibit protein translation. However, translational and therapeutic approaches to inhibit protein synthesis in tumors are limited. In this work, we identified that reactive oxygen species, which are generated by a wide range of chemotherapy and other drugs, inhibit protein synthesis and reduce the level of critical proteins that support tumorigenesis in Ewing sarcoma cells. In particular, we identified that both hydrogen peroxide and auranofin, an inhibitor of thioredoxin reductase and regulator of oxidative stress and reactive oxygen species, activate the repressor of protein translation 4E-BP1 and reduce the levels of the oncogenic proteins RRM2 and PLK1 in Ewing and other sarcoma cell lines. These results provide novel insight into the mechanism of how ROS-inducing drugs target cancer cells via inhibition of protein translation and identify a mechanistic link between ROS and the DNA replication (RRM2) and cell cycle regulatory (PLK1) pathways.

FBXO45 levels regulated ferroptosis renal tubular epithelial cells in a model of diabetic nephropathy by PLK1

Objective

This research aims to investigate the role and underlying biological mechanism of FBXO45 in regulating ferroptosis of renal fibrocytes in a diabetic nephropathy (DN) model.

Methods

C57BL/6 mice were fed with a high-fat diet and injected with streptozotocin to induce diabetes. Human renal glomerular endothelial cells stimulated with d-glucose.

Results

Serum FBXO45 mRNA expression was found to be down-regulated in patients with DN. There was a negative correlation between the expression of serum FBXO45 mRNA and serum α-SMA, Collagen I, and E-cadherin mRNA in patients with DN. Additionally, the expression of serum FBXO45 mRNA showed a negative correlation with blood sugar levels. Based on a 3D model prediction, it was observed that FBXO45 interacts with polo-like kinase 1 (PLK1) at GLY-271, ILE-226, GLY-166, LEU-165, ARG-245, and ASN-220, while PLK1 interacts with FBXO45 at TYR-417, ARG-516, HIS-489, TYR-485, GLN-536, and ARG-557. This interaction was confirmed through immunoprecipitation assay, which showed the interlinking of FBXO45 protein with PLK1 protein.

Conclusions

These findings indicate that FBXO45 plays a role in mitigating ferroptosis in DN through the regulation of the PLK1/GPX4/SOX2 pathway. This highlights the potential of targeting FBXO45 as a therapeutic approach to ameliorate ferroptosis in DN.

Onvansertib in Combination with FOLFIRI and Bevacizumab in Second-Line Treatment of KRAS-Mutant Metastatic Colorectal Cancer: A Phase Ib Clinical Study

PURPOSE

Onvansertib is a highly specific inhibitor of polo-like kinase 1 (PLK1), with demonstrated safety in solid tumors. We evaluated, preclinically and clinically, the potential of onvansertib in combination with chemotherapy as a therapeutic option for KRAS-mutant colorectal cancer.

PATIENTS AND METHODS

Preclinical activity of onvansertib was assessed (i) in vitro in KRAS wild-type and -mutant isogenic colorectal cancer cells and (ii) in vivo, in combination with irinotecan, in a KRAS-mutant xenograft model. Clinically, a phase Ib trial was conducted to investigate onvansertib at doses 12, 15, and 18 mg/m2 (days 1-5 and 14-19 of a 28-day cycle) in combination with FOLFIRI/bevacizumab (days 1 and 15) in patients with KRAS-mutant metastatic colorectal cancer who had prior oxaliplatin exposure. Safety, efficacy, and changes in circulating tumor DNA (ctDNA) were assessed.

RESULTS

In preclinical models, onvansertib displayed superior activity in KRAS-mutant than wild-type isogenic colorectal cancer cells and demonstrated potent antitumor activity in combination with irinotecan in vivo. Eighteen patients enrolled in the phase Ib study. Onvansertib recommended phase II dose was established at 15 mg/m2. Grade 3 and 4 adverse events (AE) represented 15% of all treatment-related AEs, with neutropenia being the most common. Partial responses were observed in 44% of patients, with a median duration of response of 9.5 months. Early ctDNA dynamics were predictive of treatment efficacy.

CONCLUSIONS

Onvansertib combined with FOLIFRI/bevacizumab exhibited manageable safety and promising efficacy in second-line treatment of patients with KRAS-mutant metastatic colorectal cancer. Further exploration of this combination therapy is ongoing. See related commentary by Stebbing and Bullock, p. 2005.

Auranofin and reactive oxygen species inhibit protein synthesis and regulate the level of the PLK1 protein in Ewing sarcoma cells

Novel therapeutic approaches are needed for the treatment of Ewing sarcoma tumors. We previously identified that Ewing sarcoma cell lines are sensitive to drugs that inhibit protein translation. However, translational and therapeutic approaches to inhibit protein synthesis in tumors are limited. In this work, we identified that reactive oxygen species, which are generated by a wide range of chemotherapy and other drugs, inhibit protein synthesis and reduce the level of critical proteins that support tumorigenesis in Ewing sarcoma cells. In particular, we identified that both hydrogen peroxide and auranofin, an inhibitor of thioredoxin reductase and regulator of oxidative stress and reactive oxygen species, activate the repressor of protein translation 4E-BP1 and reduce the levels of the oncogenic proteins RRM2 and PLK1 in Ewing and other sarcoma cell lines. These results provide novel insight into the mechanism of how ROS-inducing drugs target cancer cells via inhibition of protein translation and identify a mechanistic link between ROS and the DNA replication (RRM2) and cell cycle regulatory (PLK1) pathways.

Polo-like Kinase 1 Inhibition in KRAS-Mutated Metastatic Colorectal Cancer

Inhibition of Polo-like kinase 1 (Plk1) is a promising new target and therapeutic strategy in metastatic colorectal cancer, especially those with KRAS mutations. New data support further development of onvansertib, and highlights the role of circulating tumor DNA in phase I clinical trials. See related article by Ahn et al., p. 2039.

Peptide mimetic NC114 induces growth arrest by preventing PKCδ activation and FOXM1 nuclear translocation in colorectal cancer cells

The peptide mimetic, NC114, is a promising anticancer compound that specifically kills colorectal cancer cells without affecting normal colon epithelial cells. In our previous study, we observed that NC114 inhibited the Wnt/β-catenin pathway, with significant downregulation of both Ser 675-phosphorylated β-catenin and its target genes, cyclin D1 and survivin. However, the molecular mechanism responsible for its cytotoxic effect has not yet been fully characterized. In the present study, we demonstrated that NC114 prevented cell cycle progression from S to G2/M phase by downregulating cell cycle-related gene expression, and also induced growth arrest in SW480 and HCT-116 colorectal cancer cells. A novel covariation network analysis combined with transcriptome analysis revealed a series of signaling cascades affected by NC114 treatment, and identified protein kinase C-δ (PKCδ) and forkhead box protein M1 (FOXM1) as important regulatory factors for NC114-induced growth arrest. NC114 treatment inhibits the activation of PKCδ and its kinase activity, which suppresses MEK/ERK signaling. Attenuated MEK/ERK signaling then results in a reduction in FOXM1 phosphorylation and subsequent nuclear translocation of FOXM1 and β-catenin. Consequently, formation of a T-cell factor-4 (TCF4)/β-catenin transcription complex in the nucleus is inhibited and transcription of its target genes, such as cell cycle-related genes, is downregulated. The efficacy of NC114 on tumor growth was confirmed in a xenograft model. Collectively, elucidation of the mechanism by which NC114 induces growth arrest in colorectal cancer cells should provide a novel therapeutic strategy for colorectal cancer treatment.

Targeted delivery of polo-like kinase 1 siRNA nanoparticles using an EGFR-PEG bispecific antibody inhibits proliferation of high-risk neuroblastoma

High-risk neuroblastoma has poor survival due to treatment failure and off-target side effects of therapy. Small molecule inhibitors have shown therapeutic efficacy at targeting oncogenic cell cycle dysregulators, such as polo-like kinase 1 (PLK1). However, their clinical success is limited by a lack of efficacy and specificity, causing off-target toxicity. Herein, we investigate a new treatment strategy whereby a bispecific antibody (BsAb) with dual recognition of methoxy polyethylene glycol (PEG) and a neuroblastoma cell-surface receptor, epidermal growth factor receptor (EGFR), is combined with a PEGylated small interfering RNA (siRNA) lipid nanoparticle, forming BsAb-nanoparticle RNA-interference complexes for targeted PLK1 inhibition against high-risk neuroblastoma. Therapeutic efficacy of this strategy was explored in neuroblastoma cell lines and a tumor xenograft model. Using ionizable lipid-based nanoparticles as a low-toxicity and clinically safe approach for siRNA delivery, we identified that their complexing with EGFR-PEG BsAb resulted in increases in cell targeting (1.2 to >4.5-fold) and PLK1 gene silencing (>2-fold) against EGFR+ high-risk neuroblastoma cells, and enhancements correlated with EGFR expression on the cells (r > 0.94). Through formulating nanoparticles with PEG-lipids ranging in diffusivity, we further identified a highly diffusible PEG-lipid which provided the most pronounced neuroblastoma cell binding, PLK1 silencing, and significantly reduced cancer growth in vitro in high-risk neuroblastoma cell cultures and in vivo in a tumor-xenograft mouse model of the disease. Together, this work provides an insight on the role of PEG-lipid diffusivity and EGFR targeting as potentially relevant variables influencing the therapeutic efficacy of siRNA nanoparticles in high-risk neuroblastoma.

PLK1 and its substrate MISP facilitate intrahepatic cholangiocarcinoma progression by promoting lymphatic invasion and impairing E-cadherin adherens junctions

Intrahepatic cholangiocarcinoma (iCCA) is a subtype of CCA and has a high mortality rate and a relatively poor prognosis. However, studies focusing on increased cell motility and loss of epithelial integrity during iCCA progression remain relatively scarce. We collected seven fresh tumor samples from four patients to perform RNA sequencing (RNA-seq) and assay for transposase-accessible chromatin using sequencing (ATAC-seq) to determine the transcriptome profile and chromatin accessibility of iCCA. The increased expression of cell cycle regulators, including PLK1 and its substrate MISP, was identified. Ninety-one iCCA patients were used to validate the clinical significance of PLK1 and MISP. The upregulation of PLK1 and MISP was determined in iCCA tissues. Increased expression of PLK1 and MISP was significantly correlated with tumor number, N stage, and lymphatic invasion in an iCCA cohort. Knockdown of PLK1 or MISP reduced trans-lymphatic endothelial migration and wound healing and affected focal adhesions in vitro. In cell‒cell junctions, MISP localized to adherens junctions and suppressed E-cadherin dimerization. PLK1 disrupted adherens junctions in a myosin-dependent manner. Furthermore, PLK1 and MISP promoted cell proliferation in vitro and tumorigenesis in vivo. In iCCA, PLK1 and MISP promote aggressiveness by increasing lymphatic invasion, tumor growth, and motility through the repression of E-cadherin adherens junctions.

Fatty acid binding protein 5 is a novel therapeutic target for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is an aggressive subtype of liver cancer and is one of the most common cancers with high mortality worldwide. Reprogrammed lipid metabolism plays crucial roles in HCC cancer cell survival, growth, and evolution. Emerging evidence suggests the importance of fatty acid binding proteins (FABPs) in contribution to cancer progression and metastasis; however, how these FABPs are dysregulated in cancer cells, especially in HCC, and the roles of FABPs in cancer progression have not been well defined.

AIM

To understand the genetic alterations and expression of FABPs and their associated cancer hallmarks and oncogenes in contributing to cancer malignancies.

METHODS

We used The Cancer Genome Atlas datasets of pan cancer and liver hepatocellular carcinoma (LIHC) as well as patient cohorts with other cancer types in this study. We investigated genetic alterations of FABPs in various cancer types. mRNA expression was used to determine if FABPs are abnormally expressed in tumor tissues compared to non-tumor controls and to investigate whether their expression correlates with patient clinical outcome, enriched cancer hallmarks and oncogenes previously reported for patients with HCC. We determined the protein levels of FABP5 and its correlated genes in two HCC cell lines and assessed the potential of FABP5 inhibition in treating HCC cells.

RESULTS

We discovered that a gene cluster including five FABP family members (FABP4, FABP5, FABP8, FABP9 and FABP12) is frequently co-amplified in cancer. Amplification, in fact, is the most common genetic alteration for FABPs, leading to overexpression of FABPs. FABP5 showed the greatest differential mRNA expression comparing tumor with non-tumor tissues. High FABP5 expression correlates well with worse patient outcomes (P < 0.05). FABP5 expression highly correlates with enrichment of G2M checkpoint (r = 0.33, P = 1.1e-10), TP53 signaling pathway (r = 0.22, P = 1.7e-5) and many genes in the gene sets such as CDK1 (r = 0.56, P = 0), CDK4 (r = 0.49, P = 0), and TP53 (r = 0.22, P = 1.6e-5). Furthermore, FABP5 also correlates well with two co-expressed oncogenes PLK1 and BIRC5 in pan cancer especially in LIHC patients (r = 0.58, P = 0; r = 0.58, P = 0; respectively). FABP5high Huh7 cells also expressed higher protein levels of p53, BIRC5, CDK1, CDK2, and CDK4 than FABP5low HepG2 cells. FABP5 inhibition more potently inhibited the tumor cell growth in Huh7 cells than in HepG2 cells.

CONCLUSION

We discovered that FABP5 gene is frequently amplified in cancer, especially in HCC, leading to its significant elevated expression in HCC. Its high expression correlates well with worse patient outcome, enriched cancer hallmarks and oncogenes in HCC. FABP5 inhibition impaired the cell viability of FABP5high Huh7 cells. All these support that FABP5 is a novel therapeutic target for treating FABP5high HCC.

Prognostic and immunological roles of heat shock protein A4 in lung adenocarcinoma

BACKGROUND

Heat shock protein A4 (HSPA4) belongs to molecular chaperone protein family which plays important roles within variable cellular activities, including cancer initiation and progression. However, the prognostic and immunological significance of HSPA4 in lung adenocarcinoma (LUAD) has not been revealed yet.

AIM

To explore the prognostic and immunological roles of HSPA4 to identify a novel prognostic biomarker and therapeutic target for LUAD.

METHODS

We assessed the prognostic and immunological significance of HSPA4 in LUAD using data from The Cancer Genome Atlas database. The association between HSPA4 expression and clinical-pathological features was assessed through Kruskal-Wallis and Wilcoxon signed-rank test. Univariate/multivariate Cox regression analyses and Kaplan-Meier curves were employed to evaluate prognostic factors, including HSPA4, in LUAD. Gene set enrichment analysis (GSEA) was conducted to identify the key signaling pathways associated with HSPA4. The correlation between HSPA4 expression and cancer immune infiltration was evaluated using single-sample gene set enrichment analysis (ssGSEA).

RESULTS

Overexpressing HSPA4 was significantly related to advanced pathologic TNM stage, advanced pathologic stage, progression disease status of primary therapy outcome and female subgroups with LUAD. In addition, increased HSPA4 expression was found to be related to worse disease-specific survival and overall survival. GSEA analysis indicated a significant correlation between HSPA4 and cell cycle regulation and immune response, particularly through diminishing the function of cytotoxicity cells and CD8 T cells. The ssGSEA algorithm showed a positive correlation between HSPA4 expression and infiltrating levels of Th2 cells, while a negative correlation was observed with cytotoxic cell infiltration levels.

CONCLUSION

Our findings indicate HSPA4 is related to prognosis and immune cell infiltrates and may act as a novel prognostic biomarker and therapeutic target for LUAD.

PLK1 and PARP positively correlate in Middle Eastern breast cancer and their combined inhibition overcomes PARP inhibitor resistance in triple negative breast cancer

Background

Despite advancements in treatment approaches, patients diagnosed with aggressive breast cancer (BC) subtypes typically face an unfavorable prognosis. Globally, these cancers continue to pose a significant threat to women's health, leading to substantial morbidity and mortality. Consequently, there has been a significant struggle to identify viable molecular targets for therapeutic intervention in these patients. Polo-like Kinase-1 (PLK1) represents one of these molecular targets currently undergoing rigorous scrutiny for the treatment of such tumors. Yet, its role in the pathogenesis of BC in Middle Eastern ethnicity remains unexplored.

Methods

We investigated the expression of PLK1 protein in a cohort of more than 1500 Middle Eastern ethnicity BC cases by immunohistochemistry. Association with clinicopathological parameters and prognosis were performed. In vitro studies were conducted using the PLK1 inhibitor volasertib and the PARP inhibitor olaparib, either alone or in combination, in PTC cell lines.

Results

Overexpression of PLK1 was detected in 27.4% of all BC cases, and this was notably correlated with aggressive clinicopathological markers. PLK1 was enriched in the triple-negative breast cancer (TNBC) subtype and exhibited poor overall survival (p = 0.0347). Notably, there was a positive correlation between PLK1 and PARP overexpression, with co-expression of PLK1 and PARP observed in 15.7% of cases and was associated with significantly poorer overall survival (OS) compared to the overexpression of either protein alone (p = 0.0050). In vitro, we studied the effect of PLK1 and PARP inhibitors either single or combined treatments in two BRCA mutated, and one BRCA proficient TNBC cell lines. We showed that combined inhibition significantly reduced cell survival and persuaded apoptosis in TNBC cell lines. Moreover, our findings indicate that inhibition of PLK1 can reinstate sensitivity in PARP inhibitor (PARPi) resistant TNBC cell lines.

Conclusion

Our results shed light on the role of PLK1 in the pathogenesis and prognosis of Middle Eastern BC and support the potential clinical development of combined inhibition of PLK1 and PARP, a strategy that could potentially broaden the use of PLK1 and PARP inhibitors beyond BC cases lacking BRCA.

PLK1 inhibitors as a new targeted treatment for adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is an aggressive malignancy with limited treatment options. Polo-like kinase 1 (PLK1) is a promising drug target; PLK1 inhibitors (PLK1i) have been investigated in solid cancers and are more effective in TP53-mutated cases. We evaluated PLK1 expression in ACC samples and the efficacy of two PLK1i in ACC cell lines with different genetic backgrounds. PLK1 protein expression was investigated by immunohistochemistry in tissue samples and correlated with clinical data. The efficacy of rigosertib (RGS), targeting RAS/PI3K, CDKs and PLKs, and poloxin (Pol), specifically targeting the PLK1 polo-box domain, was tested in TP53-mutated NCI-H295R, MUC-1, and CU-ACC2 cells and in TP53 wild-type CU-ACC1. Effects on proliferation, apoptosis, and viability were determined. PLK1 immunostaining was stronger in TP53-mutated ACC samples vs wild-type (P = 0.0017). High PLK1 expression together with TP53 mutations correlated with shorter progression-free survival (P= 0.041). NCI-H295R showed a time- and dose-dependent reduction in proliferation with both PLK1i (P< 0.05at 100 nM RGS and 30 µM Pol). In MUC-1, a less pronounced decrease was observed (P< 0.05at 1000 nM RGS and 100 µM Pol). 100 nM RGS increased apoptosis in NCI-H295R (P< 0.001), with no effect on MUC-1. CU-ACC2 apoptosis was induced only at high concentrations (P < 0.05 at 3000 nM RGS and 100 µM Pol), while proliferation decreased at 1000 nM RGS and 30 µM Pol. CU-ACC1 proliferation reduced, and apoptosis increased, only at 100 µM Pol. TP53-mutated ACC cell lines demonstrated better response to PLK1i than wild-type CU-ACC1. These data suggest PLK1i may be a promising targeted treatment of a subset of ACC patients, pre-selected according to tumour genetic signature.

Pyroptosis-related gene signature: A predictor for overall survival, immunotherapy response, and chemosensitivity in patients with pancreatic adenocarcinoma

Background

Pancreatic adenocarcinoma (PAAD) is a lethal malignancy with high levels of heterogeneity. Pyroptosis is thought to influence the development of various tumors. Nevertheless, the role of pyroptosis-related genes (PRGs) in prognostic risk stratification and therapeutic guidance for PAAD remains ambiguously.

Methods

Transcriptome profile and clinical information of PAAD patients were retrieved from The Cancer Genome Atlas (TCGA) as well as Gene Expression Omnibus (GEO) databases, followed by differential analysis. Patients were divided into distinct pyroptosis phenotype subtypes based on the characteristic of differently expressed PRGs (DEPRGs). Then a PRG signature was established through univariate analysis and LASSO algorithm in the training set to assess the prognostic risk, and its reliability was verified in the validation set using receiver operating characteristic(ROC) curve. The correlation of risk score with tumor microenvironment(TME), TMB and chemotherapeutic drug sensitivity were also analyzed. In addition, a nomogram was constructed to promote better clinical application.

Results

A total of 28 DEPRGs were determined in the integrated TCGA-GEO datasets. Patients were divided into three pyroptosis phenotype subtypes, Kaplan-Meier curve suggested patients in cluster B had a worse prognosis than those in cluster A and C. Then a price signature comprised of 8 PRGs was generated. TME analysis suggested that the low-risk subgroup displayed potential stronger antitumor immune effect and might respond better to immune checkpoint inhibitors (ICIs) therapy. Furthermore, PRG signature exhibited favorable discriminatory ability for TMB status and the sensitivity of multiple conventional chemotherapeutic agents including paclitaxel. Ultimately, we constructed a promising nomogram according to the risk score and N stage with good predictive accuracy compared with the actual overall survival (OS) probabilities.

Conclusion

We established an 8-gene signature that could be regarded as an independent prognostic risk factor for PAAD patients. The 8-gene signature could provide rationale for immunotherapy and chemotherapy, which might help clinicians make precise individualized treatment regimens.

The expression and clinical significance of PLK1/p-PLK1 protein in NK/T cell Lymphoma

AIMS

To investigate the expression of polo-like kinase 1 protein (PLK1) and its phosphorylation level (p-PLK1) in extranodal NK/T cell lymphoma (NKTCL) and their correlation with clinical characteristics and prognosis.

METHODS

We collected 40 cases of NKTCL (referred to as the experimental group), which received diagnoses at the First Affiliated Hospital of Zhengzhou University between January 2018 and October 2022. Concurrently, we assembled a control group, including 20 cases afflicted with nasopharyngeal mucosal lymphoid hyperplasia diseases during the same timeframe. We utilized immunohistochemical techniques to evaluate the levels of PLK1 and p-PLK1 expression in both the experimental and control groups. Subsequently, we conducted an analysis to identify disparities in their expression and explore their relationships with clinical characteristics and patient prognosis.

RESULTS

Among the 40 NKTCL patients, there were 27 males and 11 females, with a median age of 51 years (range 12-80 years). Compared to the control group, the tissue samples of NKTCL patients exhibited significantly elevated expression levels and active phosphorylation levels of PLK1 (P < 0.05). Correlation analysis of the immunohistochemical H score and Ki-67 positive rate of PLK1 and p-PLK1, revealed a significant positive correlation for both (P < 0.0001, each). No statistically significant differences were observed in the distribution of PLK1 and p-PLK1 expression in NKTCL patients with respect to gender, age, Ann Arbor stage, PINK-E score, B-symptoms, lactate dehydrogenase, β2-microglobulin, blood EBV-DNA, bone marrow invasion, and lymph node metastasis (p > 0.05). Grouping based on PLK1 and p-PLK1 immunohistochemical H-scores revealed that the high expression of PLK1 and p-PLK1 was associated with poor prognosis.

CONCLUSIONS

The expression levels and active phosphorylation levels of PLK1 were significantly increased in NK/T cell lymphoma, and patients with overexpression of PLK1 and p-PLK1 had a poorer prognosis.

Proteomic Analysis Reveals a PLK1-Dependent G2/M Degradation Program and Links PKA-AKAP2 to Cell Cycle Control

Targeted protein degradation by the ubiquitin-proteasome system is an essential mechanism regulating cellular division. The kinase PLK1 coordinates protein degradation at the G2/M phase of the cell cycle by promoting the binding of substrates to the E3 ubiquitin ligase SCFβTrCP. However, the magnitude to which PLK1 shapes the mitotic proteome has not been characterized. Combining deep, quantitative proteomics with pharmacologic PLK1 inhibition (PLK1i), we identified more than 200 proteins whose abundances were increased by PLK1i at G2/M. We validate many new PLK1-regulated proteins, including several substrates of the cell cycle E3 SCFCyclin F, demonstrating that PLK1 promotes proteolysis through at least two distinct SCF-family E3 ligases. Further, we found that the protein kinase A anchoring protein AKAP2 is cell cycle regulated and that its mitotic degradation is dependent on the PLK1/βTrCP-signaling axis. Interactome analysis revealed that the strongest interactors of AKAP2 function in signaling networks regulating proliferation, including MAPK, AKT, and Hippo. Altogether, our data demonstrate that PLK1 coordinates a widespread program of protein breakdown at G2/M. We propose that dynamic proteolytic changes mediated by PLK1 integrate proliferative signals with the core cell cycle machinery during cell division. This has potential implications in malignancies where PLK1 is aberrantly regulated.

Polo-like kinase 1 suppresses lung adenocarcinoma immunity through necroptosis

Polo-like kinase 1 (PLK1) plays a crucial role in cell mitosis and has been associated with necroptosis. However, the role of PLK1 and necroptosis in lung adenocarcinoma (LA) remains unclear. In this study, we analyzed The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression databases to evaluate the prognostic value and mechanistic role of PLK1 in LA. PLK1 was found to be highly expressed in LA and was positively associated with advanced disease staging and poor survival outcomes. Functional enrichment analysis showed that PLK1 was involved in cell mitosis, neurotransmitter transmission, and drug metabolism. Further analysis using single-sample gene set enrichment analysis and ESTIMATE algorithm revealed a correlation between PLK1 expression and immune infiltration in LA. Silencing of PLK1 using miRNA transfection in LA cells reduced cell proliferation and increased apoptosis, as well as upregulating the expression of necroptosis-related proteins, such as RIPK1, RIPK3, and MLKL. Additionally, nude mouse transplantation tumor experiments demonstrated that silencing PLK1 reduced the growth capacity of LA cells. These findings suggest that PLK1 plays a critical role in LA progression by regulating necroptosis and immune infiltration, and may serve as a potential therapeutic target for immunotherapy. Furthermore, PLK1 expression can be used as a prognostic biomarker for LA patients.