Knocking down of Polo-like kinase 2 inhibits cell proliferation and induced cell apoptosis in human glioma cells

A potential tumor suppressor role of PLK2 in glioblastoma

Glioblastoma (GBM) is a highly malignant brain tumor with limited treatment options. Polo-like kinase 2 (PLK2), a member of the polo-like kinase family, has been variably implicated in cancer, but its role in GBM has not been fully elucidated. We utilized RNA-seq data from multiple databases, including Gene Expression Omnibus (GEO), the Cancer Genome Atlas (TCGA), and the Chinese Glioma Genome Atlas (CGGA), and conducted experiments on human glioma cell lines to explore PLK2's expression and function. The effects of PLK2 overexpression on GBM cell viability, proliferation, migration, cell cycle, and apoptosis were assessed, and the tumorigenic potential of PLK2 was evaluated in a mouse model. PLK2 was consistently downregulated in GBM tissues compared to normal brain tissues across several datasets. Overexpression of PLK2 in GBM cell lines U87MG and U251 reduced their tumorigenic potential and enhanced cell cycle arrest and apoptosis, with significant reductions observed in apoptosis markers. Our findings suggest that PLK2 may potentially function as a tumor suppressor in GBM. Hence, PLK2 overexpression could potentially be leveraged as a therapeutic strategy to inhibit tumor progression and enhance apoptosis, providing new avenues for GBM treatment.

RNF180 weakened the lipid droplet formation and subsequent chemoresistance by destabilizing ACC1 and ACLY in esophageal cancer

Objective

RNF180 (Ring finger protein 180) is an E3 ubiquitin-protein ligase that promotes polyubiquitination and proteasomal degradation. The study aimed to clarify the clinicopathological significances, signal pathways and molecular mechanisms of RNF180 expression in esophageal cancer.

Methods

We analyzed the clinicopathological significances and signal pathways of RNF180 expression in esophageal cancer (EC) through bioinformatics and pathological analysis. We also clarified its effects on aggressiveness and related molecular mechanisms in vitro.

Results

RNF180 mRNA expression was lower in EC than in normal tissues (p < 0.05), opposite for its methylation (p < 0.05). RNF180 mRNA expression was negatively correlated with its promoter methylation, but positively with high histological grading, N stage, and poor prognosis of EC (p < 0.05). RNF180 protein expression was positively associated with T stage, N stage, and TNM stage, but negatively with unfavorable overall survival of EC as an independent factor (p < 0.05). The differential genes of RNF180 can be categorized into olfactory transduction, focal adhesion, vascular smooth muscle contraction, calcium signal pathway, cell adhesion molecules, muscle contraction, ECM receptor interaction, and collagen degradation (p < 0.05). RNF180-related genes can be categorized into gastric acid and insulin section, muscle and cardiomyopathy, glycoprotein binding, collagen and extracellular matrix, fat digestion and diabetes, PPAR signal pathway and peptidase activity. RNF180 overexpression reduced proliferation, migration, invasion and epithelial-mesenchymal transition, and induce mitochondrial apoptosis, and Caspase-1-dependent pyroptosis of EC cells (p < 0.05). RNF180 might induce chemosensitivity by weakening ACC1- and ACLY-mediated lipogenesis via the ubiquitination and proteasomal degradation of ACC1 and ACLY, and lipid droplet assembly.

Conclusion

RNF180 might be considered as a biological marker for aggressive behaviors and poor prognosis in EC and as a molecular target of gene therapy.

Polo-like kinase2 regulates renal tubulointerstitial fibrosis via notch signaling pathway in diabetic kidney disease

Renal tubulointerstitial fibrosis is considered as an important pathological feature of diabetic kidney disease (DKD). However, the underlying mechanism remains unclear. Polo-like kinase2 (PLK2) is a known player in the regulation of organ fibrosis. Herein, we investigated the expression and function of PLK2 in renal tubular epithelial cells in DKD. Data from the GSE30529 datasets were subjected to analyze the differentially expressed genes (DEGs) in non-diabetic and diabetic renal tubule samples. Molecular docking analysis and Co-IP assay were performed to investigate the interaction between PLK2 and NOTCH1. Immunohistochemistry, immunofluorescent staining, qRT-PCR, and western blot were performed. Our research revealed an increased expression of PLK2 in both DKD mouse kidney tissues and HK-2 cells stimulated by high glucose (HG). Silencing PLK2 remarkably reduced the expression of the renal fibrosis-related markers fibronectin (FN), connective tissue growth factor (CTGF) and alpha smooth muscle actin(αSMA). Furthermore, we verified the interaction between PLK2 and NOTCH1. Silencing PLK2 significantly inhibited the activation of the Notch signaling pathway, and concurrently overexpressing HES1 rescued the downregulation of FN, CTGF, and αSMA induced by transfecting si-PLK2. Finally, we found that treatment with DAPT suppressed the activation of the Notch signaling pathway and reversed the progression of renal fibrosis caused by HG. This study demonstrates that PLK2 mediates renal tubulointerstitial fibrosis in DKD by activating the Notch signaling pathway, suggesting that PLK2 may be a potential therapeutic target for DKD.

Epigenetic dysregulation in glioblastoma: potential pathways to precision medicine

The emerging field of epigenetics has been driving glioblastoma multiforme (GBM) development and progression. Various epigenetic alterations involving tumor suppressor genes, oncogenes, and signaling pathways have been identified in GBM. These alterations contribute to the aggressive behavior, therapeutic resistance, and tumor heterogeneity observed in GBM. Furthermore, the identification of specific genetic mutations associated with epigenetic dysregulation in GBM has provided new insights into the molecular subtypes and potential therapeutic targets within GBM. Understanding the complex interplay between genetic and epigenetic alterations in GBM is crucial for the development of effective and personalized therapies for this devastating disease. This review paper provides an overview of the epigenetic changes occurring in GBM and the potential of targeted epigenetic therapies as a promising avenue for GBM treatment, highlighting the challenges and future directions in this field has been deliberated.

Proteasome activation is critical for cell death induced by inhibitors of polo-like kinase 1 (PLK1) in multiple cancers

Inhibitors of polo-like kinase (PLK) are currently being evaluated as anticancer drugs. However, the molecular mechanism of PLK inhibitor-induced cell death is not fully understood. In this study, we found that GW843682X and BI2536, two inhibitors of PLK1, significantly induced cell death in multiple type cells. The induction of cell death was related to the preferring expression of PLK1. However, in human umbilical vascular endothelial cells (HUVEC) and human colorectal carcinoma cells, which expressed higher levels of both PLK1 and PLK2, PLK1 inhibitors induced very low levels of cell death. Clinical analysis reveals PLK1 presence in 26 of 30 NPC tumor tissues. In in vivo NPC lung metastasis nude mouse models, PLK1 inhibitors decreased NPC progress. Mechanistically, the PLK1 inhibitor did not activate p53, and the cell death was not reversed by p53 inhibition. Moreover, PLK1 inhibitor-induced cell death was PARP- and caspase-independent. Although PLK1 inhibitors induced down-regulation of calpain inhibitor calpastatin and calpain was activated by PLK1 inhibition, calpain blocking did not reverse cell death induced by PLK1 inhibitors, suggesting the non-involvement of calpain. Surprisingly, we found that PLK1 inhibitors induced the activation of proteasome, and the treatment of cells with PLK1 inhibitors reduced the levels of ubiquitinated proteins. And proteasome inhibitors reversed cell death induced by PLK1 inhibitors in various cell types in which PLK1 was preferentially expressed. Moreover, PLK1 inhibition reversed the degradation of proteins including p53, caspase 8, PARP and calpastatin. These results suggest that the activation of proteasome is critical for cell death induced by PLK1 inhibition.

E3 ubiquitin ligase RNF180 impairs IPO4/SOX2 complex stability and inhibits SOX2-mediated malignancy in ovarian cancer

RING finger protein 180 (RNF180), an E3 ubiquitin ligase, is thought to be a tumor suppressor gene. However, the detailed mechanism of its effect on ovarian cancer (OV) has not been elucidated. Importin 4 (IPO4) which belongs to transport protein is reported to have cancer-promoting effects on OV. Here, we explored the potential signaling pathways related to RNF180 and IPO4. It was first verified that RNF180 is downregulated and IPO4 is upregulated in OV. By overexpressing or knocking down RNF180 in OV cells, we confirmed that RNF180 inhibited the malignant behaviors of OV cells both in vitro and in vivo. Bioinformatics analysis and proteomics experiments found that RNF180 could interact with IPO4 and promote the degradation of IPO4 through ubiquitination. In addition, overexpression of IPO4 removed the inhibitory effect of RNF180 on OV. We subsequently found that IPO4 could bind to the oncogene Sex determining Region Y-box 2 (SOX2). Knockdown of IPO4 in OV cells decreased SOX2 protein level in nucleus and promoted cyclin-dependent kinase inhibitory protein-1 (p21) expression. Overexpression of RNF180 also inhibited the expression of SOX2 in nucleus. All these results indicated that RNF180 inhibited the nuclear translocation of SOX2 by promoting ubiquitination of IPO4, which ultimately promoted the expression of p21 and then suppressed the progression of OV. This study verified the tumor suppressor effect of RNF180 on OV, elucidated the mechanism of the molecule network related to RNF180 and IPO4 in OV and identified for OV.

Comparison of two protocols for the generation of iPSC-derived human astrocytes

BACKGROUND

Astrocytes have recently gained attention as key contributors to the pathogenesis of neurodegenerative disorders including Parkinson's disease. To investigate human astrocytes in vitro, numerous differentiation protocols have been developed. However, the properties of the resulting glia are inconsistent, which complicates the selection of an appropriate method for a given research question. Thus, we compared two approaches for the generation of iPSC-derived astrocytes. We phenotyped glia that were obtained employing a widely used long, serum-free ("LSF") method against an in-house established short, serum-containing ("SSC") protocol which allows for the generation of astrocytes and midbrain neurons from the same precursor cells.

RESULTS

We employed high-content confocal imaging and RNA sequencing to characterize the cultures. The astrocytes generated with the LSF or SSC protocols differed considerably in their properties: while the former cells were more labor-intense in their generation (5 vs 2 months), they were also more mature. This notion was strengthened by data resulting from cell type deconvolution analysis that was applied to bulk transcriptomes from the cultures to assess their similarity with human postmortem astrocytes.

CONCLUSIONS

Overall, our analyses highlight the need to consider the advantages and disadvantages of a given differentiation protocol, when designing functional or drug discovery studies involving iPSC-derived astrocytes.

The malignancy suppression and ferroptosis facilitation of BCL6 in gastric cancer mediated by FZD7 repression are strengthened by RNF180/RhoC pathway

BACKGROUND

B-cell lymphoma 6 (BCL6) is a transcription repressor that plays a tumor suppressor or promoting role in various tumors. However, its function and molecular mechanism in gastric cancer (GC) remain unclear. Ferroptosis, a novel programmed cell death, is closely related to tumor development. In this research, we aimed to explore the role and mechanism of BCL6 in malignant progression and ferroptosis of gastric cancer.

METHODS

Firstly, BCL6 was identified as an important biomarker that attenuated the proliferation and metastasis of GC through tumor microarrays and confirmed in GC cell lines. RNA sequence was performed to explore the downstream genes of BCL6. The underlying mechanisms were further investigated by ChIP, dual luciferase reporter assays and rescue experiments. Cell death, lipid peroxidation, MDA and Fe2+ level were detected to determine the effect of BCL6 on ferroptosis and the mechanism was revealed. CHX, MG132 treatment and rescue experiments were used to explore the upstream regulatory mechanism of BCL6.

RESULTS

Here we showed that BCL6 expression was significantly decreased in GC tissues, and patients with low BCL6 expression showed more malignant clinical features and poor prognosis. The upregulation of BCL6 may significantly inhibited the proliferation and metastasis of GC cells in vitro and in vivo. In addition, we found that BCL6 directly binds and transcriptionally represses Wnt receptor Frizzled 7 (FZD7) to inhibit the proliferation, metastasis of GC cells. We also found that BCL6 promoted lipid peroxidation, MDA and Fe2+ level to facilitate ferroptosis of GC cells by FZD7/β-catenin/TP63/GPX4 pathway. Furthermore, the expression and function of BCL6 in GC were regulated by the ring finger protein 180 (RNF180)/ras homolog gene family member C (RhoC) pathway, which had been elucidated to be involved in significantly mediating the proliferation and metastasis of GC cells.

CONCLUSIONS

In summary, BCL6 should be considered a potential intermediate tumor suppressor to inhibit the malignant progression and induce ferroptosis, which might be a promising molecular biomarker for further mechanistic investigation of GC.

Plasma Methylated RNF180 for Noninvasive Diagnosis of Gastric Cancer

Background

RNF180 is a tumor suppressor gene involved in cell development, proliferation, and apoptosis. Methylation of RNF180 (mRNF180) leads to low expression of RNF180, which is closely related to the occurrence and development of gastric cancer (GC). This study was designed to evaluate the potential performance of plasma mRNF180 as noninvasive biomarker for the diagnosis of GC.

Methods

A total of 156 participants, including 60 patients with GC, 39 with chronic superficial gastritis (CSG), 27 with chronic atrophic gastritis (CAG), and 30 with gastric ulcer (GU) were recruited for this study. Plasma mRNF180 level was measured using real-time polymerase chain reaction.

Results

As a diagnostic target, mRNF180 had a sensitivity of 71.67% (95% CI: 58.36%-82.18%) and specificity of 59.38% (95% CI: 48.85%-69.14%). The area under the ROC curve value of mRNF180 was 0.731 (95% CI: 0.648%-0.813%) for differentiation of GC from benign gastric diseases (BGD). The effectiveness of mRNF180 was superior to that of CEA, CA199, and CA724. mRNF180 was positively correlated with age, tumor size, T stage, N stage, M stage, and clinical stage of patients with GC.

Conclusions

Plasma mRNF180 might serve as a useful and noninvasive biomarker for the diagnosis of GC and can be used to evaluate its prognosis.

Polo-Like Kinase 2: From Principle to Practice

Polo-like kinase (PLK) 2 is an evolutionarily conserved serine/threonine kinase that shares the n-terminal kinase catalytic domain and the C-terminal Polo Box Domain (PBD) with other members of the PLKs family. In the last two decades, mounting studies have focused on this and tried to clarify its role in many aspects. PLK2 is essential for mitotic centriole replication and meiotic chromatin pairing, synapsis, and crossing-over in the cell cycle; Loss of PLK2 function results in cell cycle disorders and developmental retardation. PLK2 is also involved in regulating cell differentiation and maintaining neural homeostasis. In the process of various stimuli-induced stress, including oxidative and endoplasmic reticulum, PLK2 may promote survival or apoptosis depending on the intensity of stimulation and the degree of cell damage. However, the role of PLK2 in immunity to viral infection has been studied far less than that of other family members. Because PLK2 is extensively and deeply involved in normal physiological functions and pathophysiological mechanisms of cells, its role in diseases is increasingly being paid attention to. The effect of PLK2 in inhibiting hematological tumors and fibrotic diseases, as well as participating in neurodegenerative diseases, has been gradually recognized. However, the research results in solid organ tumors show contradictory results. In addition, preliminary studies using PLK2 as a disease predictor and therapeutic target have yielded some exciting and promising results. More research will help people better understand PLK2 from principle to practice.

E3 ubiquitin ligase RNF180 reduces sensitivity of triple-negative breast cancer cells to Gefitinib by downregulating RAD51

BACKGROUND

Gefitinib (Gef) is an EGFR inhibitor and its resistance in triple negative breast cancer (TNBC) is a critical concern. E3 ubiquitin ligases are pivotal for mediation of TNBC metastasis. However, the role of E3 ubiquitin ligase Ring Finger Protein 180 (RNF180) in EGFR inhibitor resistance of TNBC remains unclear. This study was performed to investigate how the E3 ubiquitin protein ligase RNF180 manipulated the growth, metastasis, and resistance to Gef of TNBC cells.

METHODS

TNBC tissues were harvested for detection of RNF180 and RAD51 expression. Gef-resistant cell lines were constructed. Next, gain- and loss-of-function assays were implemented in TNBC cell lines and Gef-resistant cell lines, followed by assessment of TNBC cell biological processes. IP assay was performed to detect the interaction between RNF180 and RAD51. Drug resistance-related genes (MRP1, BCRP, and MDR1) were evaluated by Western blot and RT-qPCR. The tumorigenesis was performed in nude mice to observe the growth and metastasis of TNBC in vivo.

RESULTS

RAD51 was highly expressed in TNBC tissues and cells, while RNF180 was poorly expressed. Mechanistically, RNF180 degraded RAD51 by ubiquitination. Overexpression of RNF180 or silencing of RAD51 suppressed proliferation, invasion, migration, and Gef resistance of TNBC cells and accelerated their apoptosis. Upregulation of RNF180 or downregulation of RAD51 diminished tumorigenesis and Gef resistance of TNBC in mice.

CONCLUSION

RNF180 degraded RAD51 by ubiquitination, thereby inhibiting TNBC cell growth and metastasis and sensitizing TNBC cells to Gef.

Deficient immunoproteasome assembly drives gain of α-synuclein pathology in Parkinson's disease

Aberrant α-synuclein (α-Syn) accumulation resulting from proteasome dysfunction is considered as a prominent factor to initiate and aggravate the neurodegeneration in Parkinson's disease (PD). Although the involvement of 26S proteasome in proteostasis imbalance has been widely accepted, our knowledge about the regulation of immunoproteasome function and its potential role in α-Syn pathology remains limited. Immunoproteasome abundance and proteolytic activities depend on the finely tuned assembly process, especially β-ring formation mediated by the only well-known chaperone proteasome maturation protein (POMP). Here, we identified that α-Syn overexpression was associated with a reduction in immunoproteasome function, which in turn limited the degradation of polo-like kinase 2 (PLK2), exacerbated α-Syn Ser129 phosphorylation and aggregation, ultimately leading to the neurodegeneration. These effects could be dramatically attenuated by β5i overexpression. Mechanistically, α-Syn suppressed the transcriptional regulation of POMP by nuclear factor erythroid 2-related factor 2 (NRF2), thereby preventing the assembly of immunoproteasome β subunits. Dopaminergic neurons-specific overexpression of NRF2-POMP axis effectively rescued the aggregation of α-Syn and PD-like phenotypes. These findings characterized abnormal immunoproteasome assembly as a key contributor governing α-Syn accumulation and neurodegeneration, which might open up a new perspective for the implication of immunoproteasome in PD and provide approaches of manipulating immunoproteasome assembly for therapeutic purposes.

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α-Syn negatively regulated immunoproteasome by inhibiting POMP-mediated assembly.

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Immunoproteasome deficiency prevented PLK2 degradation to aggravate neurotoxicity.

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Enhanced immunoproteasome assembly via NRF2-POMP axis alleviated α-Syn pathology.

FOXN3 inhibits cell proliferation and invasion via modulating the AKT/MDM2/p53 axis in human glioma

This study aimed to evaluate the biological role of forkhead box N3 (FOXN3) in human glioma and clarify the possible molecular mechanisms. FOXN3 expression patterns in clinical tissue specimens were characterized via qPCR and Western blotting. Kaplan-Meier survival curve was applied to assess the correlation between FOXN3 expression and overall survival. Effects of FOXN3 over-expression and depletion on glioma cell proliferation, apoptosis, migration and invasion were assessed by CCK8, colony formation assay, flow cytometry, scratch wound healing assay and Transwell invasion assay, respectively. Moreover, the involvement of AKT/murine double minute 2 (MDM2)/p53 pathway was evaluated. Additionally, tumor transplantation model assay was performed to determine the effects of FOXN3 over-expression on glioma cell growth in vivo. Results showed that FOXN3 was significantly down-regulated in glioma tissues compared with normal tissues. Patients with lower FOXN3 expression exhibited a shorter overall survival time. Gain- and loss-of-function analyses demonstrated that FOXN3 over-expression significantly suppressed proliferation, survival and motility of glioma cells, whereas FOXN3 knockdown remarkably promoted glioma cell proliferation, survival and motility. Furthermore, FOXN3 over-expression inhibited the activation of AKT/MDM2/p53 signaling pathway in glioma cells, while FOXN3 depletion facilitated its activation. Additionally, tumor xenograft assays revealed that FOXN3 over-expression retarded glioma cell growth in vivo. Collectively, these findings indicate that FOXN3 inhibits cell growth and invasion through inactivating the AKT/MDM2/p53 signaling pathway and that FOXN3-AKT/MDM2/p53 axis may represent a novel therapeutic target for glioma patients.