F-box And WD Repeat Domain-containing 7 Expression Research Articles

Cancer-associated fibroblast exosomes promote prostate cancer metastasis through miR-500a-3p/FBXW7/HSF1 axis under hypoxic microenvironment.

Metastasis is the main cause of deaths in prostate cancer (PCa). However, the exact mechanisms underlying PCa metastasis are not fully understood. In this study, we discovered pronounced hypoxia in primary lesions of metastatic PCa(mPCa). The exosomes secreted by cancer-associated fibroblasts (CAFs) under hypoxic conditions significantly enhance PCa metastasis both in vitro and in vivo. Through miRNA sequencing and reverse transcription quantitative PCR (RT-qPCR), we found that hypoxia elevated miR-500a-3p levels in CAFs exosomes. Subsequent RT-qPCR, western blotting, and dual luciferase reporter assays identified F-box and WD repeat domain-containing 7(FBXW7) as a target of miR-500a-3p. In addition, immunohistochemistry revealed that FBXW7 expression decreased with the progression of PCa, while heat shock transcription factor 1(HSF1) expression increased. Introducing an FBXW7 plasmid into PCa cells reduced their metastatic potential and significantly lowered HSF1 expression. These findings suggest that CAFs exosomes drive PCa metastasis via the miR-500a-3p/FBXW7/HSF1 axis in a hypoxic microenvironment. Targeting either hypoxia or exosomal miR-500a-3p could be a promising strategy for PCa management.

Coordination-driven FBXW7 DNAzyme-Fe nanoassembly enables a binary switch of breast cancer cell cycle checkpoint responses for enhanced ferroptosis-radiotherapy.

Radiotherapy is a mainstream modality for breast cancer treatment that employs ionizing radiation (IR) to damage tumor cell DNA and elevate ROS stress, which demonstrates multiple clinically-favorable advantages including localized treatment and low invasiveness. However, breast cancer cells may activate the p53-mediated cell cycle regulation in response to radiotherapy to repair IR-induced cellular damage and facilitate post-treatment survival. F-Box and WD Repeat Domain Containing 7 (FBXW7) is a promoter of p53 degradation and critical nexus of cell proliferation and survival events. Herein, we engineered a cooperative radio-ferroptosis-stimulatory nanomedicine through coordination-driven self-assembly between ferroptosis-inducing Fe2+ ions and FBXW7-inhibiting DNAzymes and further modification of tumor-targeting dopamine-modified hyaluronic acid (HA). The nanoassembly could be selectively internalized by breast cancer cells and disintegrated in lysosomes to release the therapeutic payload. DNAzyme readily abolishes FBXW7 expression and stabilizes phosphorylated p53 to cause irreversible G2 phase arrest for amplifying post-IR tumor cell apoptosis. Meanwhile, the p53 stabilization also inhibits the SLC7A11-cystine-GSH axis, which combines with the IR-upregulated ROS levels to amplify Fe2+-mediated ferroptotic damage. The DNAzyme-Fe-HA nanoassembly could thus systematically boost the tumor cell damaging effects of IR, presenting a simple and effective approach to augment the response of breast cancer to radiotherapy. STATEMENT OF SIGNIFICANCE: To overcome the intrinsic radioresistance in breast cancer, we prepared co-assembly of Fe2+ and FBXW7-targeted DNAzymes and modified surface with dopamine conjugated hyaluronic acid (HA), which enabled tumor-specific FBXW7-targeted gene therapy and ferroptosis therapy in IR-treated breast cancers. The nanoassembly could be activated in acidic condition to release the therapeutic contents. Specifically, the DNAzymes could selectively degrade FBXW7 mRNA in breast cancer cells to simultaneously induce accumulation of p53 and retardation of NHEJ repair, eventually inducing irreversible cell cycle arrest to promote apoptosis. The p53 stabilization would also inhibit the SLC7A11/GSH/GPX4 axis to enhance Fe2+ mediated ferroptosis. These merits could act in a cooperative manner to induce pronounced tumor inhibitory effect, offering new approaches for tumor radiosensitization in the clinics.

The Role of FBXW7 in Gynecologic Malignancies.

The F-Box and WD Repeat Domain Containing 7 (FBXW7) protein has been shown to regulate cellular growth and act as a tumor suppressor. This protein, also known as FBW7, hCDC4, SEL10 or hAGO, is encoded by the gene FBXW7. It is a crucial component of the Skp1-Cullin1-F-box (SCF) complex, which is a ubiquitin ligase. This complex aids in the degradation of many oncoproteins, such as cyclin E, c-JUN, c-MYC, NOTCH, and MCL1, via the ubiquitin-proteasome system (UPS). The FBXW7 gene is commonly mutated or deleted in numerous types of cancer, including gynecologic cancers (GCs). Such FBXW7 mutations are linked to a poor prognosis due to increased treatment resistance. Hence, detection of the FBXW7 mutation may possibly be an appropriate diagnostic and prognostic biomarker that plays a central role in determining suitable individualized management. Recent studies also suggest that, under specific circumstances, FBXW7 may act as an oncogene. There is mounting evidence indicating that the aberrant expression of FBXW7 is involved in the development of GCs. The aim of this review is to give an update on the role of FBXW7 as a potential biomarker and also as a therapeutic target for novel treatments, particularly in the management of GCs.

FBXW7 promotes autophagy and inhibits proliferation of oral squamous cell carcinoma

F-box and WD repeat domain containing 7 (FBXW7) is a critical tumor suppressor. The expression of FBXW7 is decreased in oral squamous cell carcinoma (OSCC) tissues and shows diagnosis value. We aimed to investigate the influence of FBXW7 overexpression on OSCC cell proliferation and autophagy. In Balb/c nude mice, CAL27 xenograft tumor model was established. Western blot was employed to evaluate protein level. Messenger RNA level was analyzed by quantitative reverse transcription-polymerase chain reaction. Colony formation assay and MTT assay were employed to evaluate cell proliferation. FBXW7 expression was decreased in OSCC cell lines. FBXW7 inhibited cell proliferation of SCC9 and CAL27. FBXW7 increased Autophagy related 7 (Atg7), Beclin1 (BECN1), B-cell lymphoma 2 (BCL2) -associated X (BAX), BCL2 antagonist killer (BAK), and microtubule-associated protein 1 light chain 3 (LC3) levels and decreased MCL1 and BCL2 levels in CAL27 cells. FBXW7 decreased tumor volume and weight in CAL27 xenograft tumor model. FBXW7 increased BECN1, Atg7, and LC3 levels in CAL27 xenograft tumor model. In conclusion, decreased expression of FBXW7 is confirmed in diverse OSCC cell lines. The enhanced FBXW7 expression inhibits cancer cell proliferation and promotes autophagy in both OSCC cells and xenograft tumor model.

E3 ubiquitin ligase FBXW7 enhances radiosensitivity of non-small cell lung cancer cells by inhibiting SOX9 regulation of CDKN1A through ubiquitination

AbstractNon-small cell lung cancer (NSCLC) has high rates of morbidity and mortality. E3 ubiquitin ligase usually has antitumor effects. This study evaluated the mechanism of E3 ligase FBXW7 (F-box and WD repeat domain containing 7) in the radiosensitivity of NSCLC. NCI-H1299 and NCI-H1299R cells were irradiated by 0, 2, 4, and 6 Gy doses of X-ray, respectively. In addition to the measurement of cell proliferation, apoptosis, and γ-H2AX, FBXW7 expression was measured and the interaction between FBXW7 and SOX9 (SRY-box transcription factor 9) was evaluated. Ubiquitination level and protein stability of SOX9 were examined after FBXW7 overexpression. The binding relationship between SOX9 and CDKN1A (cyclin-dependent kinase inhibitor 1A) was verified. Xenograft tumor model was established to evaluate the effect of FBXW7 on radiosensitivity in vivo. FBXW7 was under-expressed in radioresistant cells. Overexpression of FBXW7 repressed NCI-H1299 and NCI-H1299R cell proliferation and colony formation and increased γ-H2AX-positive foci. Overexpression of FBXW7 increased the ubiquitination level and reduced the protein stability of SOX9. SOX9 bound to the CDKN1A promoter to inhibit CDKN1A expression. FBXW7 inhibited tumorigenesis and apoptosis and enhanced radiosensitivity of NSCLC cells in vivo via the SOX9/CDKN1A axis. Overall, FBXW7 inhibited SOX9 expression by promoting SOX9 ubiquitination and proteasome degradation, suppressing the binding of SOX9 to CDKN1A, and upregulating CDKN1A, thereby improving the radiosensitivity of NSCLC cells.

Circular RNA circ-BNC2 (hsa_circ_0008732) inhibits the progression of ovarian cancer through microRNA-223-3p/ FBXW7 axis

BackgroundCircular RNAs (circRNAs) are reported to be key regulators in the progression of human cancers. This work focuses on the function and molecular mechanism of circRNA-BNC2 (circ-BNC2) (also known as hsa_circ_0008732) in ovarian cancer (OC).MethodsQuantitative real-time polymerase chain reaction (qRT-PCR) was conducted to detect circ-BNC2, microRNA-223-3p (miR-223-3p) and F-box and WD repeat domain containing 7 (FBXW7) mRNA expressions in OC tissues and cells. Besides, cell counting kit 8 (CCK-8), transwell assay and cell cycle assays were executed to assess the proliferative, migrative, invasive abilities, and cell cycle progression of OC cells, respectively. Dual-luciferase reporter gene assay and RNA pull-down assay were used to validate the targeting relationships between miR-223-3p and circ-BNC2 or FBXW7. Western blot was adopted to determine FBXW7 protein levels in OC cells.ResultsCirc-BNC2 expression was downregulated in OC tissues and cell lines, which was associated with higher FIGO stage and lymph node metastasis of OC patients. Circ-BNC2 overexpression repressed the proliferation, migration, invasion of OC cells and induced cell cycle arrest, while silencing circ-BNC2 worked oppositely. Mechanistically, circ-BNC2 could upregulate FBXW7 expression in OC cells via sponging miR-223-3p.ConclusionCirc-BNC2 suppresses the progression of OC via regulating miR-223-3p / FBXW7 axis. Our findings provided potential biomarker for OC therapy.

Induction of GLI1 by miR-27b-3p/FBXW7/KLF5 pathway contributes to pulmonary arterial hypertension

Glioma-associated oncogene homolog 1 (GLI1), a zinc-finger transcription factor, is upregulated in tumors and promotes cancer cell proliferation and migration. However, whether GLI1 involves in pulmonary artery smooth muscle cells (PASMCs) proliferation and migration and the detailed molecular mechanisms underlying GLI1 in pulmonary arterial hypertension (PAH) are not yet clear. Primary cultured rat PASMCs and monocrotaline (MCT)-induced PAH rats model were applied to address these issues in the present study. We found that the expression of GLI1 was significantly increased in endothelin-1 (ET-1) treated PASMCs, accompanied with the activation of microRNA (miR)-27b-3p/F-box and WD repeat domain containing 7 (FBXW7)/kruppel-like factor 5 (KLF5)/GLI1 pathway through endothelin-1 receptor type A (ETAR). Elevated miR-27b-3p suppressed FBXW7 expression, which led to KLF5 accumulation by decreasing its ubiquitinated degradation, KLF5 further induced GLI1 upregulation leading to PASMCs proliferation and migration. In addition, in MCT-induced PAH rats, targeting ETAR/miR-27b-3p/FBXW7/KLF5/GLI1 pathway effectively prevented the pulmonary vascular remodeling and the development of PAH in rats. Our study indicates that interfering ETAR/miR-27b-3p/FBXW7/KLF5/GLI1 signaling axis might have a potential value in the prevention and treatment of PAH.

Recent Insight on Regulations of FBXW7 and Its Role in Immunotherapy.

SCFFBXW7 E3 ubiquitin ligase complex is a crucial enzyme of the ubiquitin proteasome system that participates in variant activities of cell process, and its component FBXW7 (F-box and WD repeat domain–containing 7) is responsible for recognizing and binding to substrates. The expression of FBXW7 is controlled by multiple pathways at different levels. FBXW7 facilitates the maturity and function maintenance of immune cells via functioning as a mediator of ubiquitination-dependent degradation of substrate proteins. FBXW7 deficiency or mutation results in the growth disturbance and dysfunction of immune cell, leads to the resistance against immunotherapy, and participates in multiple illnesses. It is likely that FBXW7 coordinating with its regulators and substrates could offer potential targets to improve the sensitivity and effects of immunotherapy. Here, we review the mechanisms of the regulation on FBXW7 and its tumor suppression role in immune filed among various diseases (mostly cancers) to explore novel immune targets and treatments.

LncRNA TUG1 compromised neuronal mitophagy in cerebral ischemia/reperfusion injury by targeting sirtuin 1.

Mitophagy protects against cerebral ischemia/reperfusion (CI/R)-induced neuronal apoptosis via mitochondrial clearance. Although taurine-upregulated gene 1 (lncRNA TUG1) has been proposed to be involved in the neuronal apoptosis evoked by CI/R, its specific role in mitophagy during the progression of CI/R injury remains unknown. The CI/R rat model was established using middle cerebral artery occlusion/reperfusion (MCAO/R). Human neuroblastoma cell line SH-SY5Y was subjected to oxygen-glucose deprivation and reoxygenation (OGD/R). Ubiquitination assay, co-immunoprecipitation assay, RNA pull-down, and RNA immunoprecipitation were used to determine the interplay among TUG1, sirtuin 1 (SIRT1), and F-box and WD repeat domain-containing 7 (FBXW7). The upregulation of the TUG1 level and downregulation of the mitophagy were observed in both MCAO/R-treated rats and OGD/R-treated cells. The administration of si-TUG1 (a siRNA directed against TUG1) potentiated mitophagy and suppressed neuronal apoptosis in OGD/R-treated cells. However, the neuroprotective effect of si-TUG1 was reversed by mitophagy inhibitor or SIRT1 knockdown in vitro. Functionally, TUG1 enhanced FBXW7-mediated SIRT1 ubiquitination by upregulating FBXW7 expression. The overexpression of FBXW7 abrogated the si-TUG1-reinforced mitophagy by decreasing SIRT1 expression, thus aggravating neuronal apoptosis in the OGD/R+si-TUG1-treated cells. In rats with MCAO/R, the interference of TUG1 clearly decreased neuronal apoptosis, lessened the infarct volume, and relieved the neurological deficits. TUG1 knockdown promotes SIRT1-induced mitophagy by suppressing FBXW7-mediated SIRT1 degradation, thus relieving the neuronal apoptosis induced by CI/R injury. LncRNA TUG1 promotes neuronal apoptosis through inhibition of mitophagy. TUG1 decreased SIRT1 expression by promoting FBXW7-mediated SIRT1 ubiquitination. FBXW7/SIRT1 axis mediated the effect of TUG1 on OGD/R-induced neuronal apoptosis by regulating mitophagy.

Downregulation of Circular RNA circPSD3 Promotes Metastasis by Modulating FBXW7 Expression in Clear Cell Renal Cell Carcinoma.

Circular RNAs (circRNAs), a novel class of noncoding RNAs, have been shown to play critical regulatory roles in clear cell renal cell carcinoma (ccRCC). Metastasis is the main contributor to the poor prognosis of patients with ccRCC. However, the role of circRNAs in ccRCC metastasis has not been fully elucidated. In this study, microarray and RNA-seq analyses revealed that circPSD3 (hsa_circ_0002111) was dramatically downregulated in ccRCC tissues compared to adjacent nontumor tissues. A qRT-PCR analysis performed on our ccRCC cohorts confirmed the downregulation of circPSD3 in ccRCC tissues and further suggested that a low level of circPSD3 expression was associated with tumor metastasis in patients with ccRCC. Based on the results of functional studies, circPSD3 significantly inhibited cell migration, invasion, and the epithelial-mesenchymal transition (EMT) in vitro and blocked pulmonary metastasis in vivo. Mechanistically, circPSD3 functioned as a competing endogenous RNA for microRNA 25-3p (miR-25-3p) to regulate F-box and WD repeat domain-containing 7 (FBXW7) expression. Further verification indicated that circPSD3 overexpression restrained an EMT-like phenotype in cells, while miR-25-3p partially rescued these effects. In summary, circPSD3 inhibits tumor metastasis by repressing the miR-25-3p/FBXW7-EMT axis and might be developed as a potential diagnostic and therapeutic target for ccRCC.

Overexpression of F-box and WD repeat domain containing 7 prevents tumor growth of bladder cancer cells through regulating SREBP1a.

BackgroundThis study aimed to explore the effect of F-box and WD repeat domain containing 7 (FBXW7) overexpression on bladder cancer, and to determine the regulatory effect of FBXW7 on sterol regulatory element-binding protein 1a (SREBP1a) in bladder cancer.MethodsThe function of F-box and FBXW7 in tumor growth of bladder cancer cells was investigated using in vivo and in vitro models. We constructed and transfected FBXW7 overexpression vectors into T24 and J82 bladder cancer cells. After transfections, the expression of FBXW7 at messenger RNA (mRNA) and protein levels in human bladder cancer cells was confirmed. To verify the effect of FBXW7 on tumor growth, cell proliferation and migration were detected in the tumor cells after overexpression of FBXW7. Additionally, an in vivo tumor model was produced by inoculating the tumor cells and the effect of FBXW7 was evaluated. Finally, the regulation mechanisms were determined.ResultsOur data showed that overexpression of FBXW7 in J28 and T24 cells significantly inhibited the migration and proliferation of J82 and T24 cells, arrested the cells at G0/G1 phase, and up-regulated phosphorylation of glycogen synthase kinase-3β, while suppressing SREBP1a expression. In vivo data also showed that FBXW7 overexpression triggered apoptosis of tumor cells, prevented the pathological changes of tumor tissues, up-regulated p-GSK3β expression, and suppressed SREBP1a expression. In addition, an interaction between FBXW7 and SREBP1a was confirmed by co-immunoprecipitation.ConclusionsTogether, our data indicate that overexpression of FBXW7 prevents tumor growth of bladder cancer cells, likely through suppressing SREBP1a expression.

CircKL inhibits the growth and metastasis of kidney cancer by sponging miR‑182‑5p and upregulating FBXW7.

Circular RNAs (circRNAs) are a type of non-coding RNA with important roles in the regulation of various biological processes involved in malignant progression. However, the potential molecular mechanisms and roles of circRNAs in kidney cancer have remained to be fully elucidated. In a previous study by our group, high-throughput microarray sequencing data were analyzed to determine the differentially expressed circRNAs in kidney cancer. In this analysis, a novel circRNA (hsa_circ_0100312, named circKL) was identified as a frequently downregulated circRNA in kidney cancer cells and tissues by reverse transcription-quantitative PCR. In the present study, Cell Counting Kit-8, colony formation, Transwell, wound-healing and mouse xenograft assays as well as a lung metastasis experiment were performed to confirm the functions of circKL. The experiments confirmed that circKL overexpression significantly inhibited the proliferation, migration, tumor growth and metastasis of kidney cancer both in vitro and in vivo. The potential molecular mechanisms of circKL were investigated by performing dual-luciferase and RNA immunoprecipitation assays. Western blot assays confirmed that overexpression of circKL significantly increased the protein level of F-box and WD repeat domain containing 7 (FBXW7). All results suggested that circKL suppressed the growth and migration of kidney cancer by sponging microRNA (miR)-182-5p and upregulating FBXW7 expression. Overall, the circKL/miR-182-5p/FBXW7 axis was indicated to have a key role in the growth and metastasis of kidney cancer and may be targeted as a novel therapeutic strategy.

F-box and WD repeat domain-containing 7 (FBXW7) mediates the hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) signaling pathway to affect hypoxic-ischemic brain damage in neonatal rats

ABSTRACT The aim of this study was to determine whether F-box and WD repeat domain-containing 7 (FBXW7) can mediate the hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) signaling pathway to affect neonatal hypoxic-ischemic brain damage (HIBD) in neonatal rats. HIBD rats were treated with LV-shFBXW7. Cerebral infarct size was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining, while microvessel density (MVD) was evaluated by immunohistochemistry. Learning and memory were tested using the Morris water maze (MWM) test. FBXW7 and HIF-1α/VEGF signaling pathway proteins were measured by Western blotting. Brain microvascular endothelial cells (BMECs) were isolated to establish an oxygen-glucose deprivation (OGD) model to evaluate treatment with FBXW7 siRNA. Cell viability was detected using a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, while cell migration was evaluated using a wound healing assay. The tube formation of BMECs was also assessed. The results demonstrated that HIBD rats exhibited increased protein expression of FBXW7, HIF-1α, and VEGF. HIBD rats also displayed increased cerebral infarct size, prolonged escape latency and a decreased number of platform crossings. However, HIBD rats treated with LV-shFBXW7 exhibited reversal of these changes. In vitro experiments showed that BMECs in the OGD group had significantly decreased cell viability, shorter vascular lumen length, and shorter migration distance than cells in the control group. Moreover, silencing FBXW7 promoted proliferation, tube formation and migration of BMECs. Taken together, silencing FBXW7 upregulates the HIF-1α/VEGF signaling pathway to promote the angiogenesis of neonatal HIBD rats after brain injury, reducing infarct volume and improving recovery of nerve function in HIBD rats.

Innate Immune Evasion of Porcine Epidemic Diarrhea Virus through Degradation of the FBXW7 Protein via the Ubiquitin-Proteasome Pathway.

Porcine epidemic diarrhea virus (PEDV) causes a porcine disease associated with swine epidemic diarrhea. Different antagonistic strategies have been identified, and the mechanism by which PEDV infection impairs the production of interferon (IFN) and delays the activation of the IFN response to escape host innate immunity has been determined, but the pathogenic mechanisms of PEDV infection remain enigmatic. Our preliminary results revealed that endogenous F-box and WD repeat domain-containing 7 (FBXW7) protein, the substrate recognition component of the SCF-type E3 ubiquitin ligase, is downregulated in PEDV-infected Vero E6 cells, according to the results from an isobaric tags for relative and absolute quantification (iTRAQ) analysis. Overexpression of FBXW7 in target cells makes them more resistant to PEDV infection, whereas ablation of FBXW7 expression by small interfering RNA (siRNA) significantly promotes PEDV infection. In addition, FBXW7 was verified as an innate antiviral factor capable of enhancing the expression of RIG-I and TBK1, and it was found to induce interferon-stimulated genes (ISGs), which led to an elevated antiviral state of the host cells. Moreover, we revealed that PEDV nonstructural protein 2 (nsp2) interacts with FBXW7 and targets FBXW7 for degradation through the K48-linked ubiquitin-proteasome pathway. Consistent with the results proven in vitro, FBXW7 reduction was also confirmed in different intestinal tissues from PEDV-infected specific-pathogen-free (SPF) pigs. Taken together, the data indicated that PEDV has evolved with a distinct antagonistic strategy to circumvent the host antiviral response by targeting the ubiquitin-proteasome-mediated degradation of FBXW7. Our findings provide novel insights into PEDV infection and pathogenesis. IMPORTANCE To counteract the host antiviral defenses, most viruses, including coronaviruses, have evolved with diverse strategies to dampen host IFN-mediated antiviral response, by interfering with or evading specific host regulators at multiple steps of this response. In this study, a novel antagonistic strategy was revealed showing that PEDV infection could circumvent the host innate response by targeted degradation of endogenous FBXW7 in target cells, a process that was verified to be a positive modulator for the host innate immune system. Degradation of FBXW7 hampers host innate antiviral activation and facilitates PEDV replication. Our findings reveal a new mechanism exploited by PEDV to suppress the host antiviral response.

Phragmunis a suppresses glioblastoma through the regulation of MCL1-FBXW7 by blocking ELK1-SRF complex-dependent transcription

Glioblastoma (GBM) is a highly aggressive brain tumor. During screening work, we found a new compound named phragmunis A (PGA), which is derived from the fruitbody of Trogia venenata, exhibits a potential cytotoxic effect on patient-derived recurrent GBM cells and temozolomide (TMZ)-resistant cell lines. The present study was designed to investigate the potential molecular mechanism of the anti-glioma effects of PGA in vitro and in vivo. Studies investigating the mechanism revealed that PGA diminished the binding efficiency of ETS family of transcription factor (ELK1) and Serum response factor (SRF), and suppressed ELK1-SRF complex-dependent transcription, which decreased the transcriptional levels of downstream genes Early growth response protein 1 (EGR1)-Polycomb ring finger (BMI1), thus inducing the imbalanced regulation between Myeloid cell leukaemia-1 (MCL1) and F-Box and WD repeat domain containing 7 (FBXW7). Finally, orthotopic xenograft models were established to confirm the anti-glioma effect of PGA on tumour growth. We showed, for the first time, that the cytotoxic effects of PGA occurred by inducing MCL1 inhibition and FBXW7 activation by blocking ELK1-SRF complex-dependent transcription. The blockage of ELK1-mediated transcription resulted in the suppression of EGR1-BMI1, which led to the upregulation of FBXW7 expression and downregulation of MCL1. These findings suggested that PGA could be a therapeutic drug candidate for the treatment of recurrent GBM by targeting the ELK1-SRF complex.

In search for biomarkers and potential drug targets for uterine serous endometrial cancer

ObjectiveSerous endometrial cancer (USC) is a challenging malignancy associated with metastasis, recurrence and poor outcome. To identify clinically relevant prognostic biomarkers, we focused on a panel of proteins selected after a comprehensive literature review, for tumour profiling of a homogeneous cohort of USC patients.MethodsProtein levels and localization were assessed by immunohistochemistry analysis in 36 hysterectomy samples. Tissue sections were stained with the following antibodies: Aurora A, phospho (T288) Aurora A, BRCA1, CHK1, CIP2A, Cyclin B1, Cyclin E, E2F-1, phospho (S364) E2F-1, FBXW7, FOXM1, phospho (S9) GSK3Beta, PLK1, phospho (T210) PLK1, PPP2R1B, p73, RAD51. Each marker was evaluated as a continuously-scaled variable for association with disease progression and death, using Cox proportional hazards models. The sample consisted of 36 patients with USC, half with stage III or IV disease.ResultsResults showed that higher CHK1 (Checkpoint kinase 1) expression was associated with a decreased risk of progression and death, after adjusting for stage. Interestingly, analysis of a TCGA data set of 109 USC patients corroborates our results showing a favourable prognostic role of CHEK1 after adjusting for stage. Higher FBXW7 (F-box and WD repeat domain containing 7) expression and higher cytoplasmic expression of PPP2R1B (Protein Phosphatase 2 A, Scaffold Subunit Abeta) were each associated with a decreased risk of progression, after adjusting for stage.ConclusionsIn conclusion, results from the present study identify new clinically relevant biomarkers and potential drug targets for uterine serous endometrial cancer.

FBXW7 inhibits invasion, migration and angiogenesis in ovarian cancer cells by suppressing VEGF expression through inactivation of β-catenin signaling.

F-box and WD repeat domain containing 7 (FBXW7) is a tumor suppressor gene frequently inactivated in several human malignancies. The present study aimed to investigate the role of FBXW7 in the invasion, migration and angiogenesis of ovarian cancer (OC) cells, and to identify its potential molecular mechanisms. First, the expression levels of FBXW7 and vascular endothelial growth factor (VEGF) were detected in several human OC cell lines using western blotting. Subsequently, FBXW7 was overexpressed to determine VEGF expression in SKOV3 cells. Transwell, wound healing and tube formation assays were performed following transfection with FBXW7 and VEGF overexpression plasmids to assess invasion, migration and angiogenesis in SKOV3 cells, respectively. Western blot analysis was performed to detect the expression levels of epithelial-to-mesenchymal transition and angiogenesis-associated proteins. In addition, the expression levels of β-catenin and c-Myc were assessed, and lithium chloride (LiCl), an agonist of β-catenin signaling, was used to elucidate the molecular mechanisms by which FBXW7 mediates its antitumor activity in OC. The results demonstrated that FBXW7 expression was markedly downregulated, whilst VEGF expression was markedly upregulated in OC cell lines compared with that in normal ovarian cells. Overexpression of FBXW7 significantly decreased VEGF expression in SKOV3 cells. Notably, overexpression of VEGF reversed the inhibitory effects of FBXW7 overexpression on the invasion, migration and angiogenesis of OC cells, accompanied by upregulated expression levels of N-cadherin, slug, CD31, VEGF receptor 1 (VEGFR1) and VEGFR2, and downregulated expression levels of E-cadherin. Furthermore, overexpression of FBXW7 markedly suppressed β-catenin and c-Myc expression, whereas the decreased expression levels of VEGF, VEGFR1 and VEGFR2 following overexpression of FBXW7 were increased after treatment of SKOV3 cells with LiCl. Overall, the results of the present study suggested that FBXW7 inhibited invasion, migration and angiogenesis of OC cells by suppressing VEGF expression through inactivation of β-catenin signaling. Thus, FBXW7 may be used as a novel therapeutic target for the treatment of OC.

Circ_CLASP2 Regulates High Glucose-Induced Dysfunction of Human Endothelial Cells Through Targeting miR-140-5p/FBXW7 Axis.

Hyperglycemia exposure results in the dysfunction of endothelial cells (ECs) and the development of diabetic complications. Circular RNAs (circRNAs) have been demonstrated to play critical roles in EC dysfunction. The current study aimed to explore the role and mechanism of circRNA CLIP–associating protein 2 (circ_CLASP2, hsa_circ_0064772) on HG-induced dysfunction in human umbilical vein endothelial cells (HUVECs). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to assess the levels of circ_CLASP2, miR-140-5p and F-box, and WD repeat domain-containing 7 (FBXW7). The stability of circ_CLASP2 was identified by the actinomycin D and ribonuclease (RNase) R assays. Cell colony formation, proliferation, and apoptosis were measured by a standard colony formation assay, colorimetric 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay, and flow cytometry, respectively. Western blot analysis was performed to determine the expression of related proteins. Targeted correlations among circ_CLASP2, miR-140-5p, and FBXW7 were confirmed by dual-luciferase reporter assay. High glucose (HG) exposure downregulated the expression of circ_CLASP2 in HUVECs. Circ_CLASP2 overexpression or miR-140-5p knockdown promoted proliferation and inhibited apoptosis of HUVECs under HG conditions. Circ_CLASP2 directly interacted with miR-140-5p via pairing to miR-140-5p. The regulation of circ_CLASP2 overexpression on HG-induced HUVEC dysfunction was mediated by miR-140-5p. Moreover, FBXW7 was a direct target of miR-140-5p, and miR-140-5p regulated HG-induced HUVEC dysfunction via FBXW7. Furthermore, circ_CLASP2 mediated FBXW7 expression through sponging miR-140-5p. Our current study suggested that the overexpression of circ_CLASP2 protected HUVEC from HG-induced dysfunction at least partly through the regulation of the miR-140-5p/FBXW7 axis, highlighting a novel therapeutic approach for the treatment of diabetic-associated vascular injury.

Gain of circBRAF Represses Glioma Progression by Regulating miR-1290/FBXW7 Axis.

Dysregulated circular RNAs (circRNAs) have been confirmed to partake in the modulation of the glioma progression. Here, we intended to explore the role of circBRAF in glioma and the possible action mechanism. The expression levels of circBRAF, microRNA (miR)-1290 and F-box and WD repeat domain containing 7 (FBXW7) were analyzed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) or western blot. Cell viability was assessed by 3-(4, 5)-dimethylthiazole-2-y1)-2, 5-biphenyl tetrazolium bromide (MTT) assay. Cell cycle distribution was determined by flow cytometry. Cell migration and invasion were evaluated through Trans-well assay. Related protein levels were detected by western blot. Targeted relation among circBRAF, miR-1290 and FBXW7 was validated by dual-luciferase reporter, RNA immunoprecipitation (RIP) and pull-down assays. Xenograft model was constructed to explore the function of circBRAF in vivo. Expression of circBRAF and FBXW7 was decreased in glioma tissues and cells. Upregulation of circBRAF inhibited glioma cell proliferation and metastasis in vitro. MiR-1290 was upregulated in glioma, which was sponged by circBRAF. Besides, circBRAF elevated FBXW7 expression by targeting miR-1290. Introduction of miR-1290 or FBXW7 knockdown could counteract the inhibitory effects of circBRAF upregulation on the malignant phenotypes of glioma cells. Overexpression of circBRAF repressed the tumor growth in vivo. Upregulation of circBRAF suppressed glioma evolvement in vitro and in vivo by regulating miR-1290/FBXW7 axis, broadening the cognition of glioma progression.

FBXW7 mediates high glucose‑induced SREBP‑1 expression in renal tubular cells of diabetic nephropathy under PI3K/Akt pathway regulation.

Diabetic nephropathy (DN) is a severe complication of diabetes mellitus and lipid metabolism abnormality serves a key role in the pathogenesis of DN. Sterol regulatory element-binding protein 1 (SREBP-1) overexpression mediates aberrant lipid accumulation in renal tubular cells of DN. However, the exact mechanism involved in increased SREBP-1 has not been fully elucidated. The aim of the present study was to explore the mechanism involved in SREBP-1 upregulation. Diabetic mice and high glucose-cultured HKC cells were chosen to detect the expression of FBXW7 and SREBP-1 using immunohistochemistry, western blotting and PCR. The present study demonstrated that F-box and WD repeat domain containing 7 (FBXW7) expression was decreased in renal tubular cells of diabetic mice. Moreover, the co-expression of FBXW7 and SREBP-1 was observed in renal tubular cells, but not in the glomeruli. High glucose-induced the downregulation of FBXW7 expression in in vitro cultured HKC cells, which was accompanied by SREBP-1 upregulation. In addition, overexpression of FBXW7 in HKC cells led to SREBP-1 downregulation. By contrast, knockdown of FBXW7 caused SREBP-1 upregulation in HKC cells. It was found that the PI3K/Akt signaling pathway was activated in high glucose-stimulated HKC cells, and inhibition of PI3K/Akt pathway using LY294002 increased FBXW7 expression and decreased SREBP-1 expression. Taken together, the present results suggested that FBXW7 mediated high glucose-induced SREBP-1 expression in renal tubular cells of DN, under the regulation of the PI3K/Akt signaling pathway.