PLK4: a promising target for cancer therapy

Reversal of the tamoxifen‑resistant breast cancer malignant phenotype by proliferation inhibition with bromosulfonamidine amino‑podophyllotoxin

One of the lignans isolated from plants within the genus Podophyllum is podophyllotoxin (PPT). PPT and its derivatives are pharmacologically active compounds with potential antiproliferative properties in several kinds of tumors. Although these compounds have been used to treat other malignancies, no PPT derivative-based chemotherapeutic agent has been used to cure tamoxifen (TAM)-resistant breast cancer in clinical trials, to the best of our knowledge. Thus, using TAM-resistant breast cancer as a disease model, the present study assessed the effects of a recently synthesized PPT derivative, bromosulfonamidine amino-PPT (BSAPPT), on TAM-resistant breast cancer. Using the tamoxifen-resistant breast cancer cell model (MCF-7/TAMR) in vitro, Cell Counting Kit-8 and colony formation assays were adopted to evaluate the effect of BSAPPT on cell proliferation. Cell apoptosis and cell cycle assays were used to assess the influence of BSAPPT on cell apoptosis and the cell cycle in MCF-7/TAMR. The targets of the potential mechanism of action were analyzed by RT-qPCR and western blotting. The present study demonstrated that BSAPPT suppressed MCF-7/TAMR cell proliferation in a dose-dependent manner. By modulating the level of expression of genes linked to both apoptosis and the cell cycle, BSAPPT triggered MCF-7/TAMR cells to undergo apoptosis and prevented them from entering the cell cycle. Consequently, BSAPPT blocked these cells from proliferating, thereby halting the malignant advancement of TAM-resistant breast cancer. Therefore, these findings indicate that new therapeutic agents involving BSAPPT may be developed to facilitate the treatment of TAM-resistant breast cancer.

Polo-Like Kinase 4 Correlates with Aggressive Tumor Characteristics, Shortened Disease-Free Survival and Overall Survival in Patients with Cutaneous Melanoma who Undergo Surgical Resection

Polo-like kinase 4 (PLK4) involves in tumor progression via regulating centriole duplication. This study aimed to investigate correlations of PLK4 with tumor characteristics and survival in cutaneous melanoma patients undergoing surgical resection. Tumor specimens of 43 patients were retrieved for PLK4 determination by immunohistochemistry (IHC). The IHC score was a multiplication of staining intensity and percentage of staining-positive cells. This study found the median and mean tumor PLK4 IHC score was 0.0 (interquartile range: 0.0-6.0) and 3.5 ± 3.2 (mean ± SD), respectively. Elevated tumor PLK4 IHC score correlated with lymph node metastasis (P = 0.028), higher tumor node metastasis (TNM) stage (P = 0.004), and adjuvant therapy (P =0.029). Tumor PLK4 IHC score > 0 did not relate to disease-free survival (DFS) or overall survival (OS) (both P > 0.050). Tumor PLK4 IHC score > 3 associated with decreased DFS (P = 0.027), but not OS (P = 0.098). Five-year DFS rate of patients with tumor PLK4 IHC score = 0 and > 0 was 75.0% and 53.9%, correspondingly; while the rate of patients with the score ≤ 3 and > 3 was 81.0% and 37.5%, respectively. Five-year OS rate of patients with the score = 0 and > 0 was 100.0% and 66.3%, accordingly; whereas the rate of patients with the score ≤ 3 and > 3 was 85.7% and 61.5%, correspondingly. According to forward-step multivariate analysis, neither the score > 0 nor > 3 independently related to worse DFS and OS (all P > 0.050). Further validation via THE HUMAN PROTEIN ATLAS database showed high PLK4 RNA expression associated with shortened OS in melanoma patients (P = 0.001). PLK4 correlates with lymph node metastasis, increased TNM stage, and poor DFS in cutaneous melanoma patients undergoing surgical resection.

Centrosomes and associated proteins in pathogenesis and treatment of breast cancer

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

Explore Key Genes and Mechanisms Involved in Colon Cancer Progression Based on Bioinformatics Analysis

To explore underlying mechanisms related to the progression of colon cancer and identify hub genes associated with the prognosis of patients with colon cancer. GSE10950 and GSE62932 were downloaded from the Gene Expression Omnibus (GEO) database. GEO2R was utilized to screen out the differentially expressed genes (DEGs). Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were conducted on DEGs. Moreover, STRING and Cytoscape software were utilized for establishing the network of protein-protein interaction (PPI) and identifying hub genes. Afterward, data from The Cancer Genome Atlas (TCGA) was utilized for identifying prognosis-related hub genes by Kaplan-Meier survival analysis. Colon cancer cell line LOVO and human normal intestinal epithelial cell line NCM-460 were exploited to demonstrate the differential expression of selected hub genes through RT-qPCR and western blot. The LOVO cells were transfected to regulate expressions of prognosis-associated genes, followed by exploring the effects of those genes on prognosis by Cell Counting Kit-8 assay and colony-forming assay for cancer cell proliferation, cell scratch test and transwell migration assay for cancer cell migration and Annexin V-PE/7-AAD double staining as well as flow cytometry for cancer cell apoptosis. In this study, 266 common DEGs were obtained from the intersection of two datasets. The GO analysis suggested the common DEGs mainly participated in the one-carbon metabolic process, cell cycle G2/M phase transition, organelle fission, cell cycle phase transition regulation, and regulation of mitotic cell cycle phase transition. The KEGG analysis demonstrated the common DEGs were related to the p53 signaling pathway, nitrogen metabolism, mineral absorption, and cell cycle. 10 hub genes including CCNB1, KIF4A, TPX2, MT1F, PRC1, PLK4, CALD1, MMP9, CLCA1, and MMP1 were identified and CCNB1, CLCA1, and PLK4 were prognosis-related. Increased expression of CCNB1, CLCA1, and PLK4 restrained proliferation as well as migration of cancer cells and induced apoptosis of cancer cells. CCNB1, KIF4A, TPX2, MT1F, PRC1, PLK4, CALD1, MMP9, CLCA1, and MMP1 were identified as hub genes and CCNB1, CLCA1, and PLK4 could inhibit the progression of colon cancer through inhibiting proliferation as well as migration of the cancer cell and promoting apoptosis of cancer cell.

PLK4 inhibitor exhibits antitumor effect and synergizes sorafenib via arresting cell cycle and inactivating Wnt/β-catenin pathway in anaplastic thyroid cancer

The anti-tumor effect of polo-like kinase 4 (PLK4) inhibitor has been explored in several solid carcinomas, while its application in anaplastic thyroid cancer (ATC) remains scarce. Hence, the current study aimed to investigate the effect of PLK4 inhibitor on the malignant behaviors of ATC cell lines and its synergistic antitumor effect with sorafenib. C643 and 8305c cells were cultured in various concentrations of centrinone (PLK4 inhibitor) with or without sorafenib. Meanwhile, the cell viability, cell apoptosis, cell cycle and expressions of glycogen synthetase kinase beta (GSK3β), p-GSK3β, β-catenin were determined. PLK4 mRNA and protein expressions were higher in most ATC cell lines than the normal thyroid epithelial cell line (all P < .05). Centrinone decreased cell viability, induced cell apoptosis, arrested cell cycle at G2/M phase and inactivated Wnt/β-catenin signaling with dose-dependent manners in C643 and 8305c cells (all P < .05). Interestingly, centrinone plus sorafenib further improved antitumor effect (P < .05 at most concentrations), with the highest combination index at 5 nM centrinone plus 4 μM sorafenib in C643 cells, then 4 nM centrinone plus 4 μM sorafenib in C643 cells. Subsequently, centrinone plus sorafenib reduced cell viability, promoted cell apoptosis, facilitated cell cycle at G2/M phase and repressed Wnt/β-catenin signaling more effectively compared with centrinone or sorafenib monotherapy in C643 and 8305c cells (all P < .05). PLK4 inhibitor exhibits antitumor effect and synergizes sorafenib via arresting cell cycle and inactivating Wnt/β-catenin pathway in ATC.

Design, synthesis, and biological evaluation of novel pyrimidin-2-amine derivatives as potent PLK4 inhibitors

Serine/threonine protein kinase PLK4 is a master regulator of centriole duplication, which is significant for maintaining genome integrity. Accordingly, due to the detection of PLK4 overexpression in a variety of cancers, PLK4 has been identified as a candidate anticancer target. Thus, it is a very meaningful to find effective and safe PLK4 inhibitors for the treatment of cancer. However, the reported PLK4 inhibitors are scarce and have potential safety issues. In this study, a series of novel and potent PLK4 inhibitors with an aminopyrimidine core was obtained utilizing the scaffold hopping strategy. The in vitro enzyme activity results showed that compound 8h (PLK4 IC50 = 0.0067 μM) displayed high PLK4 inhibitory activity. In addition, compound 8h exhibited a good plasma stability (t1/2 > 289.1 min), liver microsomal stability (t1/2 > 145 min), and low risk of DDIs. At the cellular level, it presented excellent antiproliferative activity against breast cancer cells. Taken together, these results suggest that compound 8h has potential value in the further research of PLK4-targeted anticancer drugs.

Design, synthesis, and biological evaluation of a potent PLK4 inhibitor WY29 with 1H-pyrazolo[3,4-d]pyrimidine scaffold

Centriole duplication occurs once per cell cycle and is regulated by Polo-like kinase 4 (PLK4). Overexpression of PLK4 in somatic cells can lead to the excessive formation of centrioles, directly causing chromosome segregation errors and tumorigenesis. In this study, we described our efforts to develop a series of PLK4 inhibitors with 1H-pyrazolo[3,4-d]pyrimidine core, and further structure- and receptor-based design and optimization resulted in a potent inhibitor WY29 (IC₅₀  = 0.027 μM), which exhibited good selectivity to other PLK family members (PLK1-3). At the cellular level, compound WY29 showed excellent antiproliferative activity against three breast cancer cell lines (MCF-7, BT474, and MDA-MB-231) while weak inhibitory activity was found on normal cell line HUVECs. In addition, the in vitro preliminary drug-like properties evaluation of compound WY29 showed outstanding stability in human plasma and liver microsomes, and weak inhibitory activity against the major subtypes of human cytochrome P450. Also, the drug-like properties prediction of compound WY29 displayed remarkable drug-like properties (drug-likeness mode score: 1.06). In conclusion, these results support the further development of compound WY29 as a lead compound for PLK4-targeted anticancer drug discovery.

Downregulation of Polo-like kinase 4 induces cell apoptosis and G2/M arrest in acute myeloid leukemia

BACKGROUND

Polo-like kinase 4 (PLK4) is a crucial regulator for centriole replication and is reported to be aberrantly expressed in various cancers, where it participates to tumorigenesis. However, PLK4 effect in acute myeloid leukemia (AML), is still uncertain. This study investigates the function of PLK4 in AML.

METHODS

Quantitative real-time PCR was used to measure the level of PLK4. Centrinone, a selective PLK4 small molecule inhibitor, was used for PLK4 inhibition and explore its effect in AML cells. The cell growth was detected by the CCK8, while the cell cycle and apoptosis were assessed by flow cytometry. The level of proteins associated with apoptosis, cell cycle and endoplasmic reticulum (ER) stress were analyzed by western blotting.

RESULTS

PLK4 was overexpressed in AML cells. PLK4 knockdown or its specific inhibition by centrinone induced G2/M phase arrest via suppressing the expression of cyclin B1 and Cdc2 and promoting the level of proapoptotic proteins. Moreover, PLK4 targeting enhanced the level of proteins related to ER stress, such as GRP78, ATF4, ATF6, and CHOP.

CONCLUSION

These findings demonstrated that targeting PLK4 can induce apoptosis, G2/M and ER stress in AML cells.

Polo-like kinase 4 (Plk4) potentiates anoikis-resistance of p53KO mammary epithelial cells by inducing a hybrid EMT phenotype

Polo-like kinase 4 (Plk4), the major regulator of centriole biogenesis, has emerged as a putative therapeutic target in cancer due to its abnormal expression in human carcinomas, leading to centrosome number deregulation, mitotic defects and chromosomal instability. Moreover, Plk4 deregulation promotes tumor growth and metastasis in mouse models and is significantly associated with poor patient prognosis. Here, we further investigate the role of Plk4 in carcinogenesis and show that its overexpression significantly potentiates resistance to cell death by anoikis of nontumorigenic p53 knock-out (p53KO) mammary epithelial cells. Importantly, this effect is independent of Plk4's role in centrosome biogenesis, suggesting that this kinase has additional cellular functions. Interestingly, the Plk4-induced anoikis resistance is associated with the induction of a stable hybrid epithelial-mesenchymal phenotype and is partially dependent on P-cadherin upregulation. Furthermore, we found that the conditioned media of Plk4-induced p53KO mammary epithelial cells also induces anoikis resistance of breast cancer cells in a paracrine way, being also partially dependent on soluble P-cadherin secretion. Our work shows, for the first time, that high expression levels of Plk4 induce anoikis resistance of both mammary epithelial cells with p53KO background, as well as of breast cancer cells exposed to their secretome, which is partially mediated through P-cadherin upregulation. These results reinforce the idea that Plk4, independently of its role in centrosome biogenesis, functions as an oncogene, by impacting the tumor microenvironment to promote malignancy.

Polo-like kinase 4 inhibitor CFI-400945 inhibits carotid arterial neointima formation but increases atherosclerosis

Neointima lesion and atherosclerosis are proliferative vascular diseases associated with deregulated proliferation of vascular smooth muscle cells (SMCs). CFI-400945 is a novel, highly effective anticancer drug that inhibits polo-like kinase 4 (PLK4) and targets mitosis. In this study, we aim to investigate how CFI-400945 affects the development of proliferative vascular diseases. In C57BL/6 mice, neointima formation was generated by complete carotid ligation. In apolipoprotein E knockout (ApoE^-/-) mice fed a high-fat diet, atherosclerosis was induced by partial carotid ligation. CFI-400945 was directly applied to carotid arteries via a perivascular collar. Our results showed that CFI-400945 drastically inhibited neointima formation but significantly accelerated atherosclerosis. In vitro studies showed that CFI-400945 treatment induced SMC polyploidization and arrested cells in the G2/M phase. CFI-400945 treatment upregulated p53 and p27 expression but decreased p21 and cyclin B1 expression. CFI-400945 also induced SMC apoptosis, which was inhibited by hydroxyurea, a DNA synthesis inhibitor that inhibits polyploidization. Furthermore, CFI-400945 caused supernumerary centrosomes, leading to mitotic failure, resulting in polyploidization. In conclusion, CFI-400945 prevents carotid arterial neointima formation in C57BL/6 mice but accelerates atherosclerosis in ApoE^-/- mice, likely through mitotic arrest and subsequent induction of polyploidization and apoptosis.

CRISPR activation screening in a mouse model for drivers of hepatocellular carcinoma growth and metastasis

Hepatocellular carcinoma (HCC) remains a major cause of cancer-related mortality worldwide. Here we described a genome-wide screen by CRISPR activation (CRISPRa) library in vivo for drivers of HCC growth and metastasis. Pathological results showed the cell population formed highly metastatic tumors in lung after being mutagenized with CRISPRa. In vitro validation indicated overexpression of XAGE1B, PLK4, LMO1 and MYADML2 promoted cells proliferation and invasion, and the inhibition suppressed HCC progress. In addition, we reported high MYADML2 protein level exhibited worse overall survival in HCC, which increased significantly in patients over 60 years. Moreover, high MYADML2 reduced the sensitivity to chemotherapeutic drugs. Interestingly, immune cell infiltration analysis showed that the dendritic cells, macrophages, and so forth might play important role in HCC progress. In brief, we provides a roadmap for screening functional genes related to HCC invasion and metastasis in vivo, which may provide new potential targets for the treatment of HCC.

TWEAK/Fn14 signaling may function as a reactive compensatory mechanism against extracellular matrix accumulation in keloid fibroblasts

Overabundance of the extracellular matrix resulting from hyperproliferation of keloid fibroblasts (KFs) and dysregulation of apoptosis represents the main pathophysiology underlying keloids. TWEAK is a weak apoptosis inducer, and it plays a critical role in pathological tissue remodeling via its receptor, Fn14. However, the role of TWEAK/Fn14 signaling in the pathogenesis of keloids has not been investigated. In this study, we confirmed the overexpression levels of TWEAK and Fn14 in clinical keloid tissue specimens and primary KFs. The extracellular matrix (ECM)-related genes were also evaluated between primary KFs and their normal counterparts to determine the factors leading to the formation or development of keloids. Unexpectedly, exogenous TWEAK significantly reduced the levels of collagen I and collagen III, as well as alpha-smooth muscle actin (α-SMA). Additionally, TWEAK promoted MMPs expression and apoptosis activity of KFs. Furthermore, we verified that the inhibitory effect of TWEAK on KFs is through down-regulation of Polo-like kinase 5, which modulates cell differentiation and apoptosis. The TWEAK-Fn14 axis seems to be a secondary, although less effective, compensatory mechanism to increase the catabolic functions of fibroblasts in an attempt to further decrease the accumulation of collagen. DATA AVAILABILITY: All data generated or analyzed during this study are included in this published article (and its Supporting Information files).

PLK4 initiates crosstalk between cell cycle, cell proliferation and macrophages infiltration in gliomas

Tumor immune microenvironment plays an important role in tumorigenesis and metastasis. Polo-like kinases 4 (PLK4) is a crucial regulatory factor in the process of cell cycle, and its abnormal regulation often leads to a variety of diseases including tumorigenesis. We have previously explored the function of PLK4 in sensitizing chemotherapy in glioma, but there are few studies on the correlation between PLK4 and tumor immune microenvironment. PLK4 was found to be highly expressed in various types of cancers, including glioma and closely related to histological and genetic features in public databases. Kaplan-Meier survival analysis and Cox regression analysis revealed that higher PLK4 expression is associated with poorer prognosis. GO and KEGG functional enrichment analysis showed that PLK4 expression level was significantly correlated with regulation of immune microenvironment, cell cycle and genomic instability. Immune infiltration analysis showed that high expression of PLK4 resulted in reduced infiltration of macrophages. M1 macrophage infiltration assays showed that PLK4 knockdown GBM cell lines promoted the recruitment of M1-type macrophages via altering expression of chemokines. And in intracranial tumor mouse models, PLK4 inhibition increased tumor-infiltrating M1 macrophages. In summary, our results demonstrated the correlation between high PLK4 expression level and malignant progression of gliomas, and the possible involvement of PLK4 in regulation of cell cycle, cell proliferation and macrophages infiltration in gliomas.

Effects of the PLK4 inhibitor Centrinone on the biological behaviors of acute myeloid leukemia cell lines

Polo-like kinase 4 (PLK4), a key regulator of centriole biogenesis, is frequently overexpressed in cancer cells. However, roles and the mechanism of PLK4 in the leukemiagenesis of acute myeloid leukemia (AML) remain unclear. In this study, the PLK4 inhibitor Centrinone and the shRNA knockdown were used to investigate roles and the mechanism of PLK4 in the leukemiagenesis of AML. Our results indicated that Centrinone inhibited the proliferation of AML cells in a dose- and time-dependent manner via reduced the expression of PLK4 both in the protein and mRNA levels. Moreover, colony formation assay revealed that Centrinone reduced the number and the size of the AML colonies. Centrinone induced AML cell apoptosis by increasing the activation of Caspase-3/poly ADP-ribose polymerase (PARP). Notably, Centrinone caused the G2/M phase cell cycle arrest by decreasing the expression of cell cycle-related proteins such as Cyclin A2, Cyclin B1, and Cyclin-dependent kinase 1 (CDK1). Consistent with above results, knockdown the expression of PLK4 also inhibited cell proliferation and colony formation, induced cell apoptosis, and caused G2/M phase cell cycle arrest without affecting cell differentiation. All in all, this study suggested that PLK4 inhibited the progression of AML in vitro, and these results herein may provide clues in roles of PLK4 in the leukemiagenesis of AML.

Perturbation of biological processes with small molecule kinase inhibitors

The reversible phosphorylation of substrates mediated by kinases and phosphatases affects their subcellular localization, catalytic activity, and/or interaction with other molecules. It is essential for signal transduction and the regulation of nearly all cellular processes, such as proliferation, apoptosis, metabolism, motility, and differentiation. Small molecule kinase inhibitors (SMKIs) have served as critical chemical probes to reveal the biological functions and mechanisms of kinases and their potential as therapeutic targets. In this review, we focused on a few novel SMKIs and their recent application in biological and preclinical studies to showcase how highly selective and potent SMKIs can be developed and utilized to propel the investigations on kinases and the biology behind.

Downregulation of PLK4 expression induces apoptosis and G0/G1-phase cell cycle arrest in keloid fibroblasts

Objectives

Keloids are benign fibroproliferative tumors that display many cancer‐like characteristics, such as progressive uncontrolled growth, lack of spontaneous regression, and extremely high rates of recurrence. Polo‐like kinase 4 (PLK4) was recently identified as a master regulator of centriole replication, and its aberrant expression is closely associated with tumorigenesis. This study aimed to investigate the expression and biological role of PLK4 in the pathogenesis of keloids.

Materials and Methods

We evaluated the expression of PLK4 in keloids and adjacent normal skin tissue samples. Then, we established PLK4 knockdown and overexpression cell lines in keloid fibroblasts (KFs) and normal skin fibroblasts (NFs), respectively, to investigate the roles of PLK4 in the regulation of proliferation, migration, invasion, apoptosis, and cell cycle in KFs. Centrinone B (Cen‐B), a highly selective PLK4 inhibitor, was used to inhibit PLK4 activity in KFs to evaluate the therapeutic effect on KFs.

Results

We discovered that PLK4 was overexpressed in keloid dermal samples and KFs compared with adjacent normal skin samples and NFs derived from the same patients. High PLK4 expression was positively associated with the proliferation, migration, and invasion of KFs. Furthermore, knockdown of PLK4 expression or inhibition of PLK4 activity by Cen‐B suppressed KF growth, induced KF apoptosis via the caspase‐9/3 pathway, and induced cell cycle arrest at the G0/G1 phase in vitro.

Conclusions

These findings demonstrate that PLK4 is a critical regulator of KF proliferation, migration, and invasion, and thus, Cen‐B is a promising candidate drug for keloid treatment.

Transmission ratio distortion of mutations in the master regulator of centriole biogenesis PLK4

The evolutionary conserved Polo-like kinase 4 (PLK4) is essential for centriole duplication, spindle assembly, and de novo centriole formation. In man, homozygous mutations in PLK4 lead to primary microcephaly, altered PLK4 expression is associated with aneuploidy in human embryos. Here, we report on a consanguineous four-generation family with 8 affected individuals compound heterozygous for a novel missense variant, c.881 T > G, and a deletion of the PLK4 gene. The clinical phenotype of the adult patients is mild compared to individuals with previously described PLK4 mutations. One individual was homozygous for the variant c.881G and phenotypically unaffected. The deletion was inherited by 14 of 16 offspring and thus exhibits transmission ratio distortion (TRD). Moreover, based on the already published families with PLK4 mutations, it could be shown that due to the preferential transmission of the mutant alleles, the number of affected offspring is significantly increased. It is assumed that reduced expression of PLK4 decreases the intrinsically high error rate of the first cell divisions after fertilization, increases the number of viable embryos and thus leads to preferential transmission of the deleted/mutated alleles.

Fraxetin down-regulates polo-like kinase 4 (PLK4) to inhibit proliferation, migration and invasion of prostate cancer cells through the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway

Fraxetin, a natural product isolated from herb Cortex Fraxini, has been demonstrated to exhibit anti-cancer effects on various cancers. The aim of this work is to investigate the anti-tumor effect of Fraxetin in prostate cancer and the potential mechanisms. In this study, the prostatic epithelial cell RWPE-1 and prostate cancer cell DU145 were exposed to Fraxetin (10, 20, 40, and 80 μM) to detect the changes in cell viability using cell counting kit-8 (CCK-8) assay. Fraxetin (10, 20, and 40 μM) was utilized to treat DU145 cell, then the changes in cell proliferation, apoptosis, migration, and invasion were assessed. Western blot assay was employed to detect the expression of proteins that participate in the above cellular processes as well as Polo-like kinase 4 (PLK4), phosphatidylinositol 3-kinase (PI3K). In addition to 40 μM Fraxetin treatment, DU145 cells were overexpressed with PLK4, and then the above experiments were repeated. Results revealed that Fraxetin markedly decreased DU145 cell viability, but didn’t affect the cell viability of RWPE-1. Fraxetin suppressed cell proliferation, migration, invasion, and induced apoptosis of DU145 cells in a concentration-dependent manner. Furthermore, the expression of PLK4 and phosphorylated PI3K and protein kinase B (Akt) were reduced upon Fraxetin treatment. Finally, PLK4 overexpression significantly reversed all the effects of Fraxetin on DU145 cells. Collectively, Fraxetin acted as a cancer suppressor in prostate cancer through inhibiting PLK4 expression thereby inactivating PI3K/Akt signaling.

Hypoxia Drives Centrosome Amplification in Cancer Cells via HIF1α-dependent Induction of Polo-Like Kinase 4

Centrosome amplification (CA) has been implicated in the progression of various cancer types. Although studies have shown that overexpression of PLK4 promotes CA, the effect of tumor microenvironment on polo-like kinase 4 (PLK4) regulation is understudied. The aim of this study was to examine the role of hypoxia in promoting CA via PLK4. We found that hypoxia induced CA via hypoxia-inducible factor-1α (HIF1α). We quantified the prevalence of CA in tumor cell lines and tissue sections from breast cancer, pancreatic ductal adenocarcinoma (PDAC), colorectal cancer, and prostate cancer and found that CA was prevalent in cells with increased HIF1α levels under normoxic conditions. HIF1α levels were correlated with the extent of CA and PLK4 expression in clinical samples. We analyzed the correlation between PLK4 and HIF1A mRNA levels in The Cancer Genome Atlas (TCGA) datasets to evaluate the role of PLK4 and HIF1α in breast cancer and PDAC prognosis. High HIF1A and PLK4 levels in patients with breast cancer and PDAC were associated with poor overall survival. We confirmed PLK4 as a transcriptional target of HIF1α and demonstrated that in PLK4 knockdown cells, hypoxia-mimicking agents did not affect CA and expression of CA-associated proteins, underscoring the necessity of PLK4 in HIF1α-related CA. To further dissect the HIF1α-PLK4 interplay, we used HIF1α-deficient cells overexpressing PLK4 and showed a significant increase in CA compared with HIF1α-deficient cells harboring wild-type PLK4. These findings suggest that HIF1α induces CA by directly upregulating PLK4 and could help us risk-stratify patients and design new therapies for CA-rich cancers.

IMPLICATIONS

Hypoxia drives CA in cancer cells by regulating expression of PLK4, uncovering a novel HIF1α/PLK4 axis.

A review of Plks: Thinking outside the (polo) box

The polo-like kinase (Plk) family is comprised of five different members (Plk1-5), each with their own distinct functions. Plk family members participate in pivotal cell division processes as well as in non-mitotic roles. Importantly, Plk expression has been correlated with various disease states, including cancer. Multiples therapies, which primarily target Plk1, are currently being investigated alone or in combination with other agents for clinical use in different cancers. As the role of Plks in disease progression becomes more prominent, it is important to outline their functions as cell cycle regulators and more. This review summarizes the structure and both mitotic and non-mitotic functions of each of the five Plk family members, sequentially. Additionally, the proposed mechanisms for how Plks contribute to tumorigenesis and the therapeutics currently under investigation are outlined.

Keep Calm and Carry on with Extra Centrosomes

Simple Summary

Precise chromosome segregation during mitosis is a vital event orchestrated by formation of bipolar spindle poles. Supernumerary centrosomes, caused by centrosome amplification, deteriorates mitotic processes, resulting in segregation defects leading to chromosomal instability (CIN). Centrosome amplification is frequently observed in various types of cancer and considered as a significant contributor to destabilization of chromosomes. This review provides a comprehensive overview of causes and consequences of centrosome amplification thoroughly describing molecular mechanisms.

Abstract

Aberrations in the centrosome number and structure can readily be detected at all stages of tumor progression and are considered hallmarks of cancer. Centrosome anomalies are closely linked to chromosome instability and, therefore, are proposed to be one of the driving events of tumor formation and progression. This concept, first posited by Boveri over 100 years ago, has been an area of interest to cancer researchers. We have now begun to understand the processes by which these numerical and structural anomalies may lead to cancer, and vice-versa: how key events that occur during carcinogenesis could lead to amplification of centrosomes. Despite the proliferative advantages that having extra centrosomes may confer, their presence can also lead to loss of essential genetic material as a result of segregational errors and cancer cells must deal with these deadly consequences. Here, we review recent advances in the current literature describing the mechanisms by which cancer cells amplify their centrosomes and the methods they employ to tolerate the presence of these anomalies, focusing particularly on centrosomal clustering.

Radiotherapy and radiosensitization in breast cancer: Molecular targets and clinical applications

Relatively poor survival outcomes are observed in advanced or metastatic breast cancer, where local control of the primary or metastatic disease may be achieved by surgical resection, local ablative and radiation therapies. Radioresistance, poses a major challenge in achieving durable oncologic outcomes, mandating development of novel management strategies. Although multimodality approaches that combine radiotherapy with chemotherapy, or systemic agents, are utilized for radiosensitization and treatment of various malignancies, this approach has not yet found its clinical application in breast cancer. Some agents for breast cancer treatment can serve as radiosensitizers, creating an opportunity to enhance effects of radiation while providing systemic disease control. Hence, combination of radiotherapy with radiosensitizing agents have the potential to improve oncologic outcomes in advanced or metastatic breast cancer. This review discusses molecular targets for radiosensitization and novel systemic agents that have potential for clinical use as radiosensitizers in breast cancer.

Centrosomal-associated Proteins: Potential therapeutic targets for solid tumors?

The centrosome is a special organelle in human cells and an organizing unit for microtubules and signaling molecules. In addition, the centrosome is tightly restricted during the cell cycle and forms the basal body of the cilia in ciliated cells. Centrosome abnormality is frequently observed in malignant tumors. The dysregulation of centrosome-associated proteins leads to multipolar mitosis, aneuploidy, and nondirected cell migration, and therefore promotes cancer progression. The overduplication of primary centrosome and the accumulation of chromosome, comprise the majority cause of chromosomal mis-segregation in cancer cells. This review discusses the structure and function of the centrosome and the role of its associated proteins in the progression of solid tumors. We summarized the effects of centrosome amplification abnormalities and other centrosome-related phenotypes on tumors. The mechanism of the delineation of centrosome amplification with tumor malignancy remains to be decided. A better understanding of centrosome abnormality in tumorigenesis may be useful to screen novel therapeutic strategies for the treatment of solid tumors.

Repair of Spinal Cord Injury by Inhibition of PLK4 Expression Through Local Delivery of siRNA-Loaded Nanoparticles

Polo-like kinase 4 (PLK4) is one of the key regulators of centrosomal replication. However, its role and mechanism in spinal cord injury (SCI) are still unclear. The SCI model on rats was constructed and the expression and localization of PLK4 in the spinal cord are analyzed with Western blot and immunofluorescence, respectively. Then the specific siRNAs were encapsulated in nanoparticles for the inhibition of PLK4 expression. Afterward, the role of PLK4 on astrocytes was investigated by knocking down its expression in the primary astrocytes. Moreover, siRNA-loaded nanoparticles were injected into the injured spinal cord of rats, and the motor function recovery of rats after SCI was assessed using the Basso, Beattie, and Bresnahan (BBB) locomotor scale method. Notably, the siRNA-loaded nanoparticles effectively transfect primary astrocytes and significantly inhibit PLK4 expression, together with the expression of PCNA with significance. After treatment, restoration of the motor function following SCI was significantly improved in the PLK4 knockdown group compared with the control group. Therefore, we speculate that inhibition of Plk4 may inhibit the proliferation of astrocytes and decrease the inflammatory response mediated by astrocytes, so as to promote the functional recovery of SCI. In conclusion, inhibition of PLK4 expression via siRNA-loaded nanoparticles may be a potential treatment for SCI.

The development of 3-substituted indolin-2-one derivatives as kinase inhibitors for cancer therapy

Kinases are pivotal regulators in tumorigenesis and metastasis by modulating the expression of oncogenes and the transcription of antioncogenes directly or indirectly. Correspondingly, multifarious 3-substituted indolin-2-one derivatives as selective kinase inhibitors for cancer therapy exhibited a low nanomolar activity with prominent efficacy, superior response rate and admirable tolerability. Particularly, certain 3-substituted indolin-2-one derivatives have met the requirements for clinical trials or the pharmaceutical market. Herein, we focus on the traits of 3-substituted indolin-2-one derivatives as kinase inhibitors for cancer therapy, overview recent progress of 3-substituted indolin-2-one derivatives as kinase inhibitors for cancer therapy, analyze the selectivity for tyrosine kinases inhibitors and serine/threonine kinases inhibitors from the molecular aspects based on the molecular docking studies, summarize the structure-activity relationships (SARs) as selective kinase inhibitors and provide our perspectives for the development of 3-substituted indolin-2-one derivatives as kinase inhibitors for cancer therapy.

Modelling the Functions of Polo-Like Kinases in Mice and Their Applications as Cancer Targets with a Special Focus on Ovarian Cancer

Polo-like kinases (PLKs) belong to a five-membered family of highly conserved serine/threonine kinases (PLK1-5) that play differentiated and essential roles as key mitotic kinases and cell cycle regulators and with this in proliferation and cellular growth. Besides, evidence is accumulating for complex and vital non-mitotic functions of PLKs. Dysregulation of PLKs is widely associated with tumorigenesis and by this, PLKs have gained increasing significance as attractive targets in cancer with diagnostic, prognostic and therapeutic potential. PLK1 has proved to have strong clinical relevance as it was found to be over-expressed in different cancer types and linked to poor patient prognosis. Targeting the diverse functions of PLKs (tumor suppressor, oncogenic) are currently at the center of numerous investigations in particular with the inhibition of PLK1 and PLK4, respectively in multiple cancer trials. Functions of PLKs and the effects of their inhibition have been extensively studied in cancer cell culture models but information is rare on how these drugs affect benign tissues and organs. As a step further towards clinical application as cancer targets, mouse models therefore play a central role. Modelling PLK function in animal models, e.g., by gene disruption or by treatment with small molecule PLK inhibitors offers promising possibilities to unveil the biological significance of PLKs in cancer maintenance and progression and give important information on PLKs' applicability as cancer targets. In this review we aim at summarizing the approaches of modelling PLK function in mice so far with a special glimpse on the significance of PLKs in ovarian cancer and of orthotopic cancer models used in this fatal malignancy.

Recent progress in agents targeting polo-like kinases: Promising therapeutic strategies

Polo-like kinases (PLKs) play important roles in regulating multiple aspects of cell cycle and cell proliferation. In many cancer types, PLK family members are often dysregulated, which can lead to uncontrolled cell proliferation and aberrant cell division and has been shown to associate with poor prognosis of cancers. The key roles of PLK kinases in cancers lead to an enhanced interest in them as promising targets for anticancer drug development. In consideration of PLK inhibitors and some other anticancer agents, such as BRD4, EEF2K and Aurora inhibitors, exert synergy effects in cancer cells, dual-targeting of PLK and other cancer-related targets is regarded as an rational and potent strategy to enhance the effectiveness of single-targeting therapy for cancer treatment. This review introduces the PLK family members at first and then focuses on the recent advances of single-target PLK inhibitors and summarizes the corresponding SARs of them. Moreover, we discuss the synergisms between PLK and other anti-tumor targets, and sum up the current dual-target agents based on them.

Synthesis and biological evaluation of indazole derivatives as anti-cancer agents

Several FDA approved small molecule anti-cancer drugs contain indazole scaffolds. Here, we report the design, synthesis and biological evaluation of a series of indazole derivatives. In vitro antiproliferative activity screening showed that compound 2f had potent growth inhibitory activity against several cancer cell lines (IC₅₀ = 0.23–1.15 μM). Treatment of the breast cancer cell line 4T1 with 2f inhibited cell proliferation and colony formation. 2f dose-dependently promoted the apoptosis of 4T1 cells, which was connected with the upregulation of cleaved caspase-3 and Bax, and downregulation of Bcl-2. 2f also decreased the mitochondrial membrane potential and increased the levels of reactive oxygen species (ROS) in 4T1 cells. Additionally, treatment with 2f disrupted 4T1 cells migration and invasion, and the reduction of matrix metalloproteinase metalloproteinase-9 (MMP9) and increase of tissue inhibitor matrix metalloproteinase 2 (TIMP2) were also observed. Moreover, 2f could suppress the growth of the 4T1 tumor model without obvious side effects in vivo. Taken together, these results identified 2f as a potential small molecule anti-cancer agent.

One of the synthesized indazole derivatives, 2f, displayed inhibitory activities against proliferation, migration and invasion of breast cancer cell line 4T1, with the potential of inducing cell apoptosis, and suppressing tumor growth in vivo.

Cytokinesis regulators as potential diagnostic and therapeutic biomarkers for human hepatocellular carcinoma

Cytokinesis, the final step of mitosis, is critical for maintaining the ploidy level of cells. Cytokinesis is a complex, highly regulated process and its failure can lead to genetic instability and apoptosis, contributing to the development of cancer. Human hepatocellular carcinoma is often accompanied by a high frequency of aneuploidy and the DNA ploidy pattern observed in human hepatocellular carcinoma results mostly from impairments in cytokinesis. Many key regulators of cytokinesis are abnormally expressed in human hepatocellular carcinoma, and their expression levels are often correlated with patient prognosis. Moreover, preclinical studies have demonstrated that the inhibition of key cytokinesis regulators can suppress the growth of human hepatocellular carcinoma. Here, we provide an overview of the current understanding of the signaling networks regulating cytokinesis, the key cytokinesis regulators involved in the initiation and development of human hepatocellular carcinoma, and their applications as potential diagnostic and therapeutic biomarkers.

Exogenous bacterial DnaK increases protein kinases activity in human cancer cell lines

BACKGROUND

Studies of molecular mechanisms underlying tumor cell signaling highlighted a critical role for kinases in carcinogenesis and cancer progression. To this regard, protein kinases regulates a number of critical cellular pathways by adding phosphate groups to specific substrates. For this reason, their involvement in the complex interactions between the human microbiota and cancer cells to determine therapy and tumor progression outcome is becoming increasingly relevant. Mycoplasmas are components of the normal human microbiota, and several species have also been associated to human diseases, including certain cancers. It is also important to note that Mycoplasmas and their proteins are a component of the common tumor microenvironment. In addition, several epidemiological, in vivo and in vitro studies indicate a close involvement of Mycoplasmas in cellular transformation and cancer progression.

METHODS

In this study, we investigate the effect of exogenous Mycoplasma DnaK on kinases activity by treating in vitro four different eukaryotic cancer cell lines, namely lung and prostate cancer, colon adenocarcinoma, and neuroblastoma. Phosphorylation of kinases and specific substrates was measured at 20 and 60 min.

RESULTS

Kinome analysis of our data indicates that Mycoplasma DnaK promotes the dysregulation of the activity of specific kinases and their substrates, with a known involvement in carcinogenesis and cancer progression.

CONCLUSIONS

Given the similarity in structure and amino acid composition of this protein with other bacterial DnaKs we provide a novel mechanism whereby components of the human microbiota and present in the tumor microenvironment are able to deregulate phosphorylation events occurring during carcinogenesis and cancer progression.

Identification of compounds that bind the centriolar protein SAS-6 and inhibit its oligomerization

Centrioles are key eukaryotic organelles that are responsible for the formation of cilia and flagella, and for organizing the microtubule network and the mitotic spindle in animals. Centriole assembly requires oligomerization of the essential protein spindle assembly abnormal 6 (SAS-6), which forms a structural scaffold templating the organization of further organelle components. A dimerization interaction between SAS-6 N-terminal "head" domains was previously shown to be essential for protein oligomerization in vitro and for function in centriole assembly. Here, we developed a pharmacophore model allowing us to assemble a library of low-molecular-weight ligands predicted to bind the SAS-6 head domain and inhibit protein oligomerization. We demonstrate using NMR spectroscopy that a ligand from this family binds at the head domain dimerization site of algae, nematode, and human SAS-6 variants, but also that another ligand specifically recognizes human SAS-6. Atomistic molecular dynamics simulations starting from SAS-6 head domain crystallographic structures, including that of the human head domain which we now resolve, suggest that ligand specificity derives from favorable Van der Waals interactions with a hydrophobic cavity at the dimerization site.

Identification of cancer stem cell-related biomarkers in intestinal-type and diffuse-type gastric cancer by stemness index and weighted correlation network analysis

Background

Cancer stem cells (CSCs) play an important role in drug resistance, recurrence, and metastasis of tumors. Considering the heterogeneity of tumors, this study aimed to explore the key genes regulating stem cells in intestinal-type and diffuse-type gastric cancer.

Methods

RNA-seq data and related clinical information were downloaded from The Cancer Genome Atlas (TCGA). WGCNA was used to clustered differentially expressed genes with similar expression profiles to form modules. Furtherly, based on the mRNA expression-based stemness index (mRNAsi), significant modules and key genes were identified. Next, the expression of key genes was further verified by the Oncomine database.

Results

MRNAsi scores of GC were significantly higher than that of normal tissue. Additionally, mRNAsi scores of intestinal-type GC (IGC) were significantly higher than that of diffuse-type GC (DGC). WGCNA showed that the blue module of IGC and the brown module of DGC were both the most significantly associated with mRNAsi. We screened out 16 and 43 key genes for IGC and DGC and found that these genes were closely related, respectively. Functional analysis showed the relationship between the key genes confirmed in the Oncomine database and the fate of cells.

Conclusions

In this study, 16 and 43 genes related to the characteristics of CSCs were identified in IGC and DGC, respectively. These genes were both associated with cell cycle, which could serve as therapeutic targets for the inhibition of stem cells from both types of GC.

Excess centrosomes disrupt vascular lumenization and endothelial cell adherens junctions

Proper blood vessel formation requires coordinated changes in endothelial cell polarity and rearrangement of cell-cell junctions to form a functional lumen. One important regulator of cell polarity is the centrosome, which acts as a microtubule organizing center. Excess centrosomes perturb aspects of endothelial cell polarity linked to migration, but whether centrosome number influences apical-basal polarity and cell-cell junctions is unknown. Here, we show that excess centrosomes alter the apical-basal polarity of endothelial cells in angiogenic sprouts and disrupt endothelial cell-cell adherens junctions. Endothelial cells with excess centrosomes had narrower lumens in a 3D sprouting angiogenesis model, and zebrafish intersegmental vessels had reduced perfusion following centrosome overduplication. These results indicate that endothelial cell centrosome number regulates proper lumenization downstream of effects on apical-basal polarity and cell-cell junctions. Endothelial cells with excess centrosomes are prevalent in tumor vessels, suggesting how centrosomes may contribute to tumor vessel dysfunction.

Silencing of long non-coding RNA DLX6-AS1 weakens neuroblastoma progression by the miR-513c-5p/PLK4 axis

Emerging evidence has demonstrated the crucial roles of long noncoding RNAs in human cancers, including neuroblastoma (NB). DLX6 antisense RNA 1 (DLX6-AS1) has been identified as an oncogenic driver in NB. However, the mechanisms of DLX6-AS1 in NB progression are not fully understood. Our data showed that DLX6-AS1 was significantly overexpressed in NB tissues and cells. Moreover, DLX6-AS1 silencing repressed NB cell viability, colony formation, migration, and invasion, and promoted cell cycle arrest and apoptosis in vitro, as well as decreased tumor growth in vivo. Mechanistically, DLX6-AS1 operated as a miR-513c-5p sponge. MiR-513c-5p mediated the regulation of DLX6-AS1 on NB cell malignant progression in vitro. PLK4 was a target of miR-513c-5p- and DLX6-AS1-controlled PLK4 expression via sponging miR-513c-5p. Furthermore, the suppressive effect of miR-513c-5p overexpression on NB cell malignant progression in vitro was reversed by PLK4 upregulation. Our findings identified a novel regulatory mechanism, the DLX6-AS1/miR-513c-5p/PLK4 axis, in NB progression, highlighting a strong rationale for developing DLX6-AS1 as a new target for NB management.

Comprehensive analysis of transcriptome data stemness indices identifies key genes for controlling cancer stem cell characteristics in gastric cancer

BACKGROUND

Cancer stem cells (CSCs) are the tumor cell of origin with self-renewing ability and multi-differentiation potency. CSCs can play vital roles in gastric cancer (GC) metastasis and relapse. However, the genes that regulate the stemness maintenance of CSCs in GC patients remain largely unknown. In the present study, we sought to determine the key genes associated with stemness in GC patients.

METHODS

mRNA expression-based stemness index (mRNA SI) was analyzed with regard to the differential expression levels between normal and GC tissues, as well as clinical features and survival outcomes. Weighted gene co-expression network analysis (WGCNA) was performed to identify modules of interest and key genes. The differences in mRNA expression of key genes between normal and GC tissues were calculated by "ggpubr" package in R. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) analysis were carried out to annotate the function of key genes. Protein-protein interaction (PPI) and gene co-expression analyses were conducted using STRING and "corrplot" package in R, respectively.

RESULTS

mRNA SI score was markedly increased in GC tumor compared to normal tissues. High mRNA SI score was remarkably associated with more advanced tumor stage and higher pathologic grade, but longer survival times. Based on the results of WGCNA, 19 key genes (i.e., BUB1, BUB1B, KIF14, NCAPH, RACGAP1, KIF15, CENPF, TPX2, RAD54L, KIF18B, TTX, KIF4A, SGO2, PLK4, ARHGAP11A, XRCC2, C1orf112, NCAPG, ORC6) were identified. GO and KEGG functional analyses revealed that these 19 key genes were mainly related to cell proliferation. From PPI and gene co-expression analyses, these 19 key genes were discovered to be intensively associated with each other at both protein and transcription levels.

CONCLUSIONS

our study identified 19 key genes that play vital roles in the stemness maintenance of CSCs in GC patients. Targeting these key genes may help to control CSC characteristics in GC.

Features of alternative splicing in stomach adenocarcinoma and their clinical implication: a research based on massive sequencing data

BACKGROUND

Alternative splicing (AS) offers a main mechanism to form protein polymorphism. A growing body of evidence indicates the correlation between splicing disorders and carcinoma. Nevertheless, an overall analysis of AS signatures in stomach adenocarcinoma (STAD) is absent and urgently needed.

RESULTS

2042 splicing events were confirmed as prognostic molecular events. Furthermore, the final prognostic signature constructed by 10 AS events gave good result with an area under the curve (AUC) of receiver operating characteristic (ROC) curve up to 0.902 for 5 years, showing high potency in predicting patient outcome. We built the splicing regulatory network to show the internal regulation mechanism of splicing events in STAD. QKI may play a significant part in the prognosis induced by splicing events.

CONCLUSIONS

In our study, a high-efficiency prognostic prediction model was built for STAD patients, and the results showed that AS events could become potential prognostic biomarkers for STAD. Meanwhile, QKI may become an important target for drug design in the future.

MiR-654-3p Suppresses Non-Small Cell Lung Cancer Tumourigenesis by Inhibiting PLK4

Purpose

MiR-654-3p plays important roles in many types of malignant tumours. However, the biological function of miR-654-3p in non-small cell lung cancer (NSCLC) remains unknown. In this study, the role of miR-654-3p in NSCLC was investigated.

Methods

qRT-PCR was used to evaluate the level of miR-654-3p in NSCLC tissues and cell lines, while Cell Counting Kit-8, Annexin V/propidium iodide dual staining or TUNEL staining were used to investigate proliferation and apoptosis of NSCLC cells. Luciferase assays and Western blotting were performed to validate potential targets of miR-654-3p.

Results

MiR-654-3p levels were significantly decreased in NSCLC patients and cell lines and were significantly correlated with the tumour size and tumour node metastasis stage of NSCLC patients. In A549 cells, miR-654-3p overexpression significantly increased apoptosis and inhibited growth both in vivo and in vitro, while downregulation of miR-654-3p had the opposite effects. In addition, polo-like kinase 4 (PLK4) was shown to be a target gene of miR-654-3p that is negatively regulated by miR-654-3p in A549 cells. Furthermore, PLK4 was observed to be highly expressed in NSCLC tissues and cells, and PLK4 overexpression abolished the inhibitory effects of miR-654-3p overexpression on NSCLC cell proliferation. Finally, the animal experiment results further demonstrated that miR-654-3p inhibits tumour growth and regulates PLK4 expression.

Conclusion

Our results demonstrate that miR-654-3p functions as a growth-suppressing miRNA by targeting PLK4 in NSCLC.

Anticancer effects of the PLK4 inhibitors CFI-400945 and centrinone in Ewing's sarcoma cells

Purpose

Polo-like kinase 4 (PLK4) inhibitors, such as CFI-400945 and centrinone, are emerging as promising antineoplastic agents. However, their effectiveness against Ewing’s sarcoma, a highly aggressive childhood cancer, remains to be established.

Methods

CFI-400945 and centrinone were tested in three Ewing’s sarcoma cell lines with different TP53 status. Effects were assessed by flow-cytometric analyses of cell death, dissipation of the mitochondrial transmembrane potential and cell cycle distribution, by cell viability assay as well as by caspase 3/7 activity measurement, by immunoblotting and by immunofluorescence microscopy.

Results

CFI-400945 and centrinone elicited cell death in p53 wild-type and mutant Ewing’s sarcoma cells. Both agents induced mitochondrial membrane depolarisation, caspase 3/7 activation, PARP1 cleavage and DNA fragmentation, indicating an apoptotic form of cell death. In addition, the PLK4 inhibitors induced a G2/M cell cycle arrest, particularly when cell killing was attenuated by the pan-caspase inhibitor z-VAD-fmk. Moreover, CFI-400945 treatment produced polyploidy.

Conclusion

Our findings show that PLK4 inhibitors were effective against Ewing’s sarcoma cells in vitro and thus provide a rationale for their evaluation in vivo.

Electronic supplementary material

The online version of this article (10.1007/s00432-020-03346-z) contains supplementary material, which is available to authorized users.

Clinical Significance of Polo-Like Kinase 4 as a Marker for Advanced Tumor Stage and Dismal Prognosis in Patients With Surgical Gastric Cancer

Objective:

This study aimed to investigate the correlation of polo-like kinase 4 with clinicopathological features and survival profiles in patients with gastric cancer.

Methods:

This retrospective study was conducted based on the clinical data from 289 eligible patients with gastric cancer who received resection. Polo-like kinase 4 expression in adjacent tissue and tumor tissue was determined by immunohistochemical assay and semiquantified scoring method using immunohistochemical score by staining intensity score multiplying staining density score. Based on the total immunohistochemical score (ranged from 0 to 12), the polo-like kinase 4 expression was classified as low expression (immunohistochemical: 0-3) and high expression (immunohistochemical: 4-12); furthermore, high expression was divided into high+ expression (immunohistochemical: 4-6), high++ expression (immunohistochemical: 7-9), and high+++ expression (immunohistochemical: 10-12).

Results:

Polo-like kinase 4 expression was elevated in tumor tissue compared with adjacent tissue. Tumor polo-like kinase 4 high expression correlated with increased T stage and Tumor, Node, Metastasis (TNM) stage, while, it did not correlate with age, gender, current smoke, current drink, chronic complications, Helicobacter pylori infection, tumor location, pathological grade, or N stage. Besides, higher tumor polo-like kinase 4 expression correlated with shorter disease-free survival and overall survival. Subsequently, multivariate Cox proportional hazards regression analysis showed that higher tumor polo-like kinase 4 expression was an independent predictive factor for worse disease-free survival but not for overall survival.

Conclusion:

Polo-like kinase 4 possesses the clinical significance as a biomarker for aiding prognostication and facilitating postoperative tumor management in patients with gastric cancer.

YLZ-F5, a novel polo-like kinase 4 inhibitor, inhibits human ovarian cancer cell growth by inducing apoptosis and mitotic defects

PURPOSE

Polo-like kinase 4 (PLK4), a member of the polo-like kinase family, plays several important roles in mitotic regulation, including centrosome duplication, spindle formation, and cytokinesis. PLK4 overexpression is frequently detected in many human cancers, including ovarian cancer, and the inhibition of PLK4 activity results in cancer cell mitotic arrest and apoptosis. Therefore, PLK4 might be a valid therapeutic target for antitumor therapy. In the present study, we aimed to determine if YLZ-F5, a potent small-molecule inhibitor of PLK4, inhibits ovarian cancer cell growth.

METHODS AND RESULTS

MTT assay showed that YLZ-F5 inhibited ovarian cancer cell proliferation in a concentration- and time-dependent manner. The results of colony formation assays were consistent with those of the MTT assay results. In addition, YLZ-F5 induced ovarian cancer cell apoptosis that was associated with activation of caspase-3/caspase-9. Moreover, YLZ-F5 caused aberrant in centriole duplication that was associated with the inhibition of PLK4 phosphorylation. Notably, we showed that YLZ-F5 promoted the accumulation of ovarian cancer cells with mitotic defects (> 4 N DNA content) in a concentration-dependent manner. Furthermore, YLZ-F5 markedly inhibited the migration of A2780 cells.

CONCLUSION

Taken together, these findings suggest that YLZ-F5 is a potential drug candidate for human ovarian cancer.

An overview of spirooxindole as a promising scaffold for novel drug discovery

Introduction: Spirooxindole, a unique and versatile scaffold, has been widely studied in some fields such as pharmaceutical chemistry and synthetic chemistry. Especially in the application of medicine, quite a few compounds featuring spirooxindole motif have displayed excellent and broad pharmacological activities. Many identified candidate molecules have been used in clinical trials, showing promising prospects.Areas covered: This article offers an overview of different applications and developments of spirooxindoles (including the related natural products and their derivatives) in the process of drug innovation, including such as in anticancer, antimicrobial, anti-inflammatory, analgesic, antioxidant, antimalarial, and antiviral activities. Furthermore, the crucial structure-activity relationships, molecular mechanisms, pharmacokinetic properties, and main synthetic methods of spirooxindoles-based derivatives are also reviewed.Expert opinion: Recent progress in the biological activity profiles of spirooxindole derivatives have demonstrated their significant position in present-day drug discovery. Furthermore, we believe that the multidirectional development of novel drugs containing this core scaffold will continue to be the research hotspot in medicinal chemistry in the future.