Search Results (12)

Polo-like kinase 1 (PLK1) is a serine/threonine protein kinase expressed in smooth muscle cells (SMCs), with emerging roles in regulating contraction. We hypothesize that PLK1 contributes to smooth muscle contractility in pudendal arteries (PA), small mesenteric arteries (SMA), and the corpus cavernosum (CC). Using male C57BL/6J mice, we assessed mRNA and protein expression of PLK1 in these tissues. In addition, the arteries and CC were mounted in myographs for isometric force measurement. We then investigated whether PLK1 regulates SMC contractility induced by phenylephrine (PE), U46619, and angiotensin II (Ang II) in arteries, and by PE, serotonin (5-HT), and electrical field stimulation (EFS; 1–16 Hz) in the CC, both in the presence and absence of the PLK1 inhibitor volasertib. PLK1 expression was confirmed in the SMA, PA, and CC by RT-qPCR or Western blotting. Notably, PLK1 inhibition significantly reduced Ang II-induced contraction in the PA and SMA and attenuated EFS-induced contraction at 2 and 4 Hz in the CC. In contrast, responses to PE, U46619, and 5-HT were unaffected by PLK1 inhibition. These results suggest that PLK1 selectively mediates contraction in response to Ang II and neurogenic stimuli. PLK1 may therefore represent a novel, stimulus-specific regulator of vascular and erectile smooth muscle contractility. Full article

Skin cancer remains a significant global health challenge, with rising incidence and associated mortality in late-stage and drug-resistant cases. This underscores a continuing need for more effective novel therapeutic options that can be utilized for efficient management of skin cancers. A promising approach involves exploiting novel targets, which are dysregulated in skin cancer, either alone or in combination with existing therapeutics. Among these, polo-like kinases (PLKs), a family of serine/threonine kinases, has emerged as promising candidates due to their essential role in cell cycle and maintaining genomic stability, key hallmarks of cancer. Within this family, polo-like kinase 4 (PLK4) stands out as a structurally distinct member and the master regulator of centriole duplication, ensuring this process occurs only once per cell division. Dysregulation of PLK4 can disrupt genomic integrity, contributing to tumorigenesis, thus making it a promising target for cancer management. Notably, PLK4 is frequently overexpressed in several cancers, including skin cancer, and its precise role in skin cancer is an area of current investigation. Further, several small-molecule PLK4 inhibitors such as centrinone, YLZ-F5, CFI-400945, and RP-1664 have demonstrated efficacy in targeting PLK4. Among these, CFI-400945 has advanced to clinical trials, where it has shown modest anti-cancer activity. In this review, we provide a comprehensive overview of the known functions of PLK4 in skin cancer. Additionally, we discuss potential mechanistic insights into PLK4′s involvement in skin cancer progression by extrapolating evidence from studies in other cancer types including colorectal cancer, thyroid cancer, lymphomas, leukemia, etc., while identifying gaps for future research. Full article

Centriole duplication is a vital process for cellular organisation and function, underpinning essential activities such as cell division, microtubule organisation and ciliogenesis. This review summarises the latest research on the mechanisms and regulatory pathways that control this process, focusing on important proteins such as polo-like kinase 4 (PLK4), SCL/TAL1 interrupting locus (STIL) and spindle assembly abnormal protein 6 (SAS-6). This study examines the complex steps involved in semi-conservative duplication, from initiation in the G1–S phase to the maturation of centrioles during the cell cycle. Additionally, we will explore the consequences of dysregulated centriole duplication. Dysregulation of this process can lead to centrosome amplification and subsequent chromosomal instability. These factors are implicated in several cancers and developmental disorders. By integrating recent study findings, this review emphasises the importance of centriole duplication in maintaining cellular homeostasis and its potential as a therapeutic target in disease contexts. The presented findings aim to provide a fundamental understanding that may inform future research directions and clinical interventions related to centriole biology. Full article

(1) Background: This study investigated whether polo-like kinase 4 (PLK4) is a suitable therapeutic target or biomarker for lung adenocarcinoma (LUAD). (2) Methods: We acquired LUAD data from The Cancer Genome Atlas (TCGA) database through the UCSC Xena data portal. Gene expression, clinical, survival, and mutation data from multiple samples were analyzed. Gene enrichment analysis, unsupervised clustering of PLK4-related pathways, and differential gene expression analyses were performed. Additionally, correlations, t-tests, survival analyses, and statistical analyses were performed. (3) Results: PLK4 expression was higher in LUAD tissues than in normal tissues and was associated with poor prognosis for both overall and progression-free survival in LUAD. PLK4 was highly correlated with cell-proliferation-related pathways using Gene Ontology (GO) biological process terms. PLK4 expression and pathways that were highly correlated with PLK4 expression levels were upregulated in patients with LUAD with the TP53 mutation. (4) Conclusions: PLK4 expression affects the survival of patients with LUAD and is a potential therapeutic target for LUAD with TP53 mutations. Full article

The conserved Ser/Thr protein phosphatase 5 (PP5) is involved in the regulation of key cellular processes, including DNA damage repair and cell division in eukaryotes. As a co-chaperone of Hsp90, PP5 has been shown to modulate the maturation and activity of numerous oncogenic kinases. Here, we identify a novel substrate of PP5, the Polo-like kinase 4 (Plk4), which is the master regulator of centriole duplication in animal cells. We show that PP5 specifically interacts with Plk4, and is able to dephosphorylate the kinase in vitro and in vivo, which affects the interaction of Plk4 with its partner proteins. In addition, we provide evidence that PP5 and Plk4 co-localize to the centrosomes in Drosophila embryos and cultured cells. We demonstrate that PP5 is not essential; the null mutant flies are viable without a severe mitotic phenotype; however, its loss significantly reduces the fertility of the animals. Our results suggest that PP5 is a novel regulator of the Plk4 kinase in Drosophila. Full article

Patients with psoriasis tend to develop skin cancer, and the hyperproliferation of the epidermis is a histopathological hallmark of both psoriasis and cutaneous squamous cell carcinoma (SCC), indicating that they may share pathogenic mechanisms. Interleukin-17 (IL17) stimulates the proliferation of the epidermis, leading to psoriasis. Overexpression of Polo-like kinase 4 (PLK4), which controls centriole duplication, has been identified in SCC, which also shows the hyperproliferation of keratinocytes. To investigate the cooperation between IL17 signaling and centriole duplication in epidermal proliferation, we established psoriasis and skin papilloma models in wild type (WT), IL17 receptor A (T779A) knockin (Il17ra(T779A)-KI), and IL17 receptor C knockout (Il17rc-KO) mouse strains. Bioinformatics, Western blot, immunohistochemical staining, colony formation, and real-time PCR were used to determine the effect of IL17 signaling and centrinone on epithelial proliferation. In the psoriasis model, compared to WT and Il17ra(T779A)-KI, Il17rc-KO dramatically suppressed epidermal thickening. The proliferation of keratinocytes significantly decreased in this order from WT to Il17ra(T779A)-KI and Il17rc-KO mice. In the skin papilloma model, Il17ra(T779A)-KI significantly decreased tumor burden compared to the WT, while Il17rc-KO abolished papilloma development. However, centrinone, a selective inhibitor of PLK4, did not affect skin lesion formation in either model. Our data demonstrated that Il17ra(T779A)-KI and Il17rc-KO prevent the development of psoriasis and tumorigenesis in the skin, while the topical administration of centrinone does not have any effect. Full article

Centrosomes nucleate and anchor microtubules and therefore play major roles in spindle formation and chromosome segregation during mitosis. Duplication of the centrosome occurs, similar to DNA, only once during the cell cycle. Aberration of the centrosome number is common in human tumors. At the core of centriole duplication is the conserved polo-like kinase 4, Plk4, and two structural proteins, STIL and Sas-6. In this review, I summarize and discuss developments in our understanding of the first steps of centriole duplication and their regulation. Full article

Cyclin D1 (CCND1) and cyclin-dependent kinase 4 (CDK4) both play significant roles in regulating cell cycle progression, while polo-like kinase 1 (PLK1) regulates cell differentiation and tumor progression, and activates cancer stem cells (CSCs), with the cluster of differentiation 44 (CD44) surface marker mostly being expressed. These oncogenes have emerged as promoters of metastasis in a variety of cancer types. In this study, we employed comprehensive computational and bioinformatics analyses to predict drug targets of our novel small molecules, NSC765600 and NSC765691, respectively derived from diflunisal and fostamatinib. The target prediction tools identified CCND1/CDK4/PLK1/CD44 as target genes for NSC765600 and NSC765691 compounds. Additionally, the results of our in silico molecular docking analysis showed unique ligand–protein interactions with putative binding affinities of NSC765600 and NSC765691 with CCND1/CDK4/PLK1/CD44 oncogenic signaling pathways. Moreover, we used drug-likeness precepts as our guidelines for drug design and development, and found that both compounds passed the drug-likeness criteria of molecular weight, polarity, solubility, saturation, flexibility, and lipophilicity, and also exhibited acceptable pharmacokinetic properties. Furthermore, we used development therapeutics program (DTP) algorithms and identified similar fingerprints and mechanisms of NSC765600 and NSC765691 with synthetic compounds and standard anticancer agents in the NCI database. We found that NSC765600 and NSC765691 displayed antiproliferative and cytotoxic effects against a panel of NCI-60 cancer cell lines. Based on these finding, NSC765600 and NSC765691 exhibited satisfactory levels of safety with regard to toxicity, and met all of the required criteria for drug-likeness precepts. Currently, further in vitro and in vivo investigations in tumor-bearing mice are in progress to study the potential treatment efficacies of the novel NSC765600 and NSC765691 small molecules. Full article

Recent evidence indicates that activation of adenosine monophosphate-activated protein kinase (AMPK), a highly conserved sensor and modulator of cellular energy and redox, regulates cell mitosis. However, the underlying molecular mechanisms for AMPKα subunit regulation of chromosome segregation remain poorly understood. This study aimed to ascertain if AMPKα1 deletion contributes to chromosome missegregation by elevating Polo-like kinase 4 (PLK4) expression. Centrosome proteins and aneuploidy were monitored in cultured mouse embryonic fibroblasts (MEFs) isolated from wild type (WT, C57BL/6J) or AMPKα1 homozygous deficient (AMPKα1^−/−) mice by Western blotting and metaphase chromosome spread. Deletion of AMPKα1, the predominant AMPKα isoform in immortalized MEFs, led to centrosome amplification and chromosome missegregation, as well as the consequent aneuploidy (34–66%) and micronucleus. Furthermore, AMPKα1 null cells exhibited a significant induction of PLK4. Knockdown of nuclear factor kappa B2/p52 ameliorated the PLK4 elevation in AMPKα1-deleted MEFs. Finally, PLK4 inhibition by Centrinone reversed centrosome amplification of AMPKα1-deleted MEFs. Taken together, our results suggest that AMPKα1 plays a fundamental role in the maintenance of chromosomal integrity through the control of p52-mediated transcription of PLK4, a trigger of centriole biogenesis. Full article

DNA Polymerase Theta (POLQ) is a DNA polymerase involved in error-prone translesion DNA synthesis (TLS) and error-prone repair of DNA double-strand breaks (DSBs). In the present study, we examined whether abnormal POLQ expression may be involved in the pathogenesis of lung adenocarcinoma (LAC). First, we found overexpression of POLQ at both the mRNA and protein levels in LAC, using data from the Cancer Genome Atlas (TCGA) database and by immunohistochemical analysis of our LAC series. POLQ overexpression was associated with an advanced pathologic stage and an increased total number of somatic mutations in LAC. When H1299 human lung cancer cell clones overexpressing POLQ were established and examined, the clones showed resistance to a DSB-inducing chemical in the clonogenic assay and an increased frequency of mutations in the supF forward mutation assay. Further analysis revealed that POLQ overexpression was also positively correlated with Polo Like Kinase 4 (PLK4) overexpression in LAC, and that PLK4 overexpression in the POLQ-overexpressing H1299 cells induced centrosome amplification. Finally, analysis of the TCGA data revealed that POLQ overexpression was associated with an increased somatic mutation load and PLK4 overexpression in diverse human cancers; on the other hand, overexpressions of nine TLS polymerases other than POLQ were associated with an increased somatic mutation load at a much lower frequency. Thus, POLQ overexpression is associated with advanced pathologic stage, increased somatic mutation load, and PLK4 overexpression, the last inducing centrosome amplification, in LAC, suggesting that POLQ overexpression is involved in the pathogenesis of LAC. Full article

Polo-like kinase 4 (PLK4) is a cell cycle-regulated protein kinase (PK) recruited at the centrosome in dividing cells. Its overexpression triggers centrosome amplification, which is associated with genetic instability and carcinogenesis. In previous work, we established that PLK4 is overexpressed in pediatric embryonal brain tumors (EBT). We also demonstrated that PLK4 inhibition exerted a cytostatic effect in EBT cells. Here, we examined an array of PK inhibitors (CFI-400945, CFI-400437, centrinone, centrinone-B, R-1530, axitinib, KW-2449, and alisertib) for their potential crossover to PLK4 by comparative structural docking and activity inhibition in multiple established embryonal tumor cell lines (MON, BT-12, BT-16, DAOY, D283). Our analyses demonstrated that: (1) CFI-400437 had the greatest impact overall, but similar to CFI-400945, it is not optimal for brain exposure. Also, their phenotypic anti-cancer impact may, in part, be a consequence of the inhibition of Aurora kinases (AURKs). (2) Centrinone and centrinone B are the most selective PLK4 inhibitors but they are the least likely to penetrate the brain. (3) KW-2449, R-1530 and axitinib are the ones predicted to have moderate-to-good brain penetration. In conclusion, a new selective PLK4 inhibitor with favorable physiochemical properties for optimal brain exposure can be beneficial for the treatment of EBT. Full article

Neuroblastoma (NB) is the most common extracranial solid tumor in pediatrics, with rare occurrences of primary and metastatic tumors in the central nervous system (CNS). We previously reported the overexpression of the polo-like kinase 4 (PLK4) in embryonal brain tumors. PLK4 has also been found to be overexpressed in a variety of peripheral adult tumors and recently in peripheral NB. Here, we investigated PLK4 expression in NBs of the CNS (CNS-NB) and validated our findings by performing a multi-platform transcriptomic meta-analysis using publicly available data. We evaluated the PLK4 expression by quantitative real-time PCR (qRT-PCR) on the CNS-NB samples and compared the relative expression levels among other embryonal and non-embryonal brain tumors. The relative PLK4 expression levels of the NB samples were found to be significantly higher than the non-embryonal brain tumors (p-value < 0.0001 in both our samples and in public databases). Here, we expand upon our previous work that detected PLK4 overexpression in pediatric embryonal tumors to include CNS-NB. As we previously reported, inhibiting PLK4 in embryonal tumors led to decreased tumor cell proliferation, survival, invasion and migration in vitro and tumor growth in vivo, and therefore PLK4 may be a potential new therapeutic approach to CNS-NB. Full article