F-box and WD repeat domain containing 7 inhibits the activation of hepatic stellate cells by degrading delta-like ligand 1 to block Notch signaling pathway.

Hepatic fibrosis (HF) is a precursor of liver cirrhosis, and activated hepatic stellate cells are an important driver of fibrosis. F-box and WD repeat domain containing 7 (FBXW7) expression level is down-regulated in HF, but the underlying mechanism is yet to be elucidated. The interaction between FBXW7 and delta-like ligand 1 (DLL1) was predicted. LX-2 cells were subjected to transfection of FBXW7/DLL1 silencing or overexpression plasmid. The expressions of FBXW7 and DLL1 in HF in vitro were measured by quantitative reverse transcription polymerase chain reaction and western blot. The LX-2 cell cycle, viability, proliferation, and ubiquitination were determined by flow cytometry, cell counting kit-8, colony formation, and ubiquitination assays, respectively. FBXW7 overexpression suppressed the cell viability and proliferation, facilitated cell cycle arrest, and down-regulated α-smooth muscle actin (α-SMA), Collagen I, and DLL1 protein levels, but FBXW7 silencing did the opposite. DLL1 was bound to and ubiquitin-dependently degraded by FBXW7 overexpression. DLL1 overexpression promoted the cell viability and proliferation, accelerated cell cycle, and up-regulated the levels of α-SMA, Collagen I, NOTCH2, NOTCH3, and HES1, but these trends were reversed by FBXW7 overexpression. To sum up, FBXW7 overexpression suppresses the progression of HF in vitro by ubiquitin-dependently degrading DLL1.

Myelin regulatory factor is a target of individual and interactive effects of HIV-1 Tat and morphine in the striatum and pre-frontal cortex.

HIV-associated neurocognitive disorders (HAND) remain pervasive even with increased efficacy/use of antiretroviral therapies. Opioid use/abuse among HIV + individuals is documented to exacerbate CNS deficits. White matter (WM) alterations, including myelin pallor, and volume/structural alterations detected by diffusion tensor imaging are common observations in HIV + individuals, and studies in non-human primates suggest that WM may harbor virus. Using transgenic mice that express the HIV-1 Tat protein, we examined in vivo effects of 2-6 weeks of Tat and morphine exposure on WM using genomic and biochemical methods. RNA sequencing of striatal tissue at 2 weeks revealed robust changes in mRNAs associated with oligodendrocyte precursor populations and myelin integrity, including those for transferrin, the atypical oligodendrocyte marker N-myc downstream regulated 1 (Ndrg1), and myelin regulatory factor (Myrf/Mrf), an oligodendrocyte-specific transcription factor with a significant role in oligodendrocyte differentiation/maturation. Western blots conducted after 6-weeks exposure in 3 brain regions (striatum, corpus callosum, pre-frontal cortex) revealed regional differences in the effect of Tat and morphine on Myrf levels, and on levels of myelin basic protein (MBP), whose transcription is regulated by Myrf. Responses included individual and interactive effects. Although baseline and post-treatment levels of Myrf and MBP differed between brain regions, post-treatment MBP levels in striatum and pre-frontal cortex were compatible with changes in Myrf activity. Additionally, the Myrf regulatory ubiquitin ligase Fbxw7 was identified as a novel target in our model. These results suggest that Myrf and Fbxw7 contribute to altered myelin gene regulation in HIV.

circKL inhibits the growth and metastasis of kidney cancer by sponging miR­182­5p and upregulating FBXW7.

Circular RNAs (circRNAs) are a type of non­coding 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, high­throughput 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 transcription­quantitative PCR. In the present study, Cell Counting Kit­8, colony formation, Transwell, wound­healing 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 dual­luciferase and RNA immunoprecipitation assays. Western blot assays confirmed that overexpression of circKL significantly increased the protein level of F­box and WD repeat domain containing 7 (FBXW7). All results suggested that circKL suppressed the growth and migration of kidney cancer by sponging microRNA (miR)­182­5p and upregulating FBXW7 expression. Overall, the circKL/miR­182­5p/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.

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.

Circular RNA hsa_circ_0001306 Functions as a Competing Endogenous RNA to Regulate FBXW7 Expression by Sponging miR-527 in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is one of the most common types of cancer worldwide. Circular RNAs (circRNAs) have been reported to regulate many types of cancers, including HCC. The purpose of this study was to investigate the potential roles of hsa_circ_0001306 in HCC. Firstly, the downregulation of hsa_circ_0001306 was identified by high­throughput RNA sequencing and further verified by qRT-PCR. Secondly, we evaluated the effects of hsa_circ_0001306 on HCC cell proliferation, invasion, cell cycle. Finally, we used an animal model to validate the in vitro experimental results. The expression of hsa_circ_0001306 was closely related to tumor size. Knockdown of hsa_circ_0001306 could downregulate F-box and WD repeat domain containing 7(FBXW7), a target of miR-527, thereby promoting HCC cell proliferation and invasion. Furthermore, hsa_circ_0001306 siRNA increased the multiplication rate of HCC tumors. Mechanistic studies indicated that hsa_circ_0001306 acts as a ceRNA for miR-527, which resulted in the reduction of its endogenous target, FBXW7. Hsa_circ_001306 is significantly downregulated in HCC, and the hsa_circ_0001306/miR-527/FBXW7 axis plays an important role in HCC progression.

Exosomal transfer of miR­25­3p promotes the proliferation and temozolomide resistance of glioblastoma cells by targeting FBXW7.

Intrinsic or acquired resistance to temozolomide (TMZ) is a frequent occurrence in patients with glioblastoma (GBM). Accumulating evidence has indicated that the exosomal transfer of proteins and RNAs may confer TMZ resistance to recipient cells; however, the potential molecular mechanisms are not fully understood. Thus, the aim of the present study was to elucidate the possible role of exosomal microRNAs (miRNAs/miRs) in the acquired resistance to TMZ in GBM. A TMZ­resistant GBM cell line (A172R) was used, and exosomes derived from A172R cells were extracted. Exosomal miR­25­3p was identified as a miRNA associated with TMZ resistance. The potential functions of exosomal miR­25­3p were evaluated by reverse transcription­quantitative PCR, as well as cell viability, colony formation and soft agar assay, flow cytometry, western blot analysis, BrdU incorporation assay, tumor xenograft formation, luciferase reporter assay and RNA immunoprecipitation. It was found that A172R­derived exosomes promoted the proliferation and TMZ resistance of sensitive GBM cells. Moreover, miR­25­3p epxression was upregulated in the exosomes of A172R cells and in serum samples of patients with GBM treated with TMZ. The depletion of exosomal miR­25­3p partially abrogated the effects induced by the transfer of exosomes from A172R cells. By contrast, miR­25­3p overexpression facilitated the proliferation and TMZ resistance of sensitive GBM cells. F­box and WD repeat domain­containing­7 (FBXW7) was identified as a direct target of miR­25­3p. FBXW7 knockdown promoted the proliferation and TMZ resistance of GBM cells. Furthermore, the exosomal transfer of miR­25­3p promoted c­Myc and cyclin E expression by downregulating FBXW7. Our results provided a novel insight into exosomal microRNAs in acquired TMZ resistance of GBM cells. Besides, exosomal miR­25­3p might be a potential prognostic marker for GBM patients.

FBXW7 inhibits invasion, migration and angiogenesis in ovarian cancer cells by suppressing VEGF expression through inactivation of ß-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 ß-catenin and c-Myc were assessed, and lithium chloride (LiCl), an agonist of ß-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 ß-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 ß-catenin signaling. Thus, FBXW7 may be used as a novel therapeutic target for the treatment of OC.

Phosphorylation regulates cullin-based ubiquitination in tumorigenesis.

Cullin-RING ligases (CRLs) recognize and interact with substrates for ubiquitination and degradation, and can be targeted for disease treatment when the abnormal expression of substrates involves pathologic processes. Phosphorylation, either of substrates or receptors of CRLs, can alter their interaction. Phosphorylation-dependent ubiquitination and proteasome degradation influence various cellular processes and can contribute to the occurrence of various diseases, most often tumorigenesis. These processes have the potential to be used for tumor intervention through the regulation of the activities of related kinases, along with the regulation of the stability of specific oncoproteins and tumor suppressors. This review describes the mechanisms and biological functions of crosstalk between phosphorylation and ubiquitination, and most importantly its influence on tumorigenesis, to provide new directions and strategies for tumor therapy.

FBXW7 mediates high glucose­induced SREBP­1 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 element­binding protein 1 (SREBP­1) overexpression mediates aberrant lipid accumulation in renal tubular cells of DN. However, the exact mechanism involved in increased SREBP­1 has not been fully elucidated. The aim of the present study was to explore the mechanism involved in SREBP­1 upregulation. Diabetic mice and high glucose­cultured HKC cells were chosen to detect the expression of FBXW7 and SREBP­1 using immunohistochemistry, western blotting and PCR. The present study demonstrated that F­box and WD repeat domain containing 7 (FBXW7) expression was decreased in renal tubular cells of diabetic mice. Moreover, the co­expression of FBXW7 and SREBP­1 was observed in renal tubular cells, but not in the glomeruli. High glucose­induced the downregulation of FBXW7 expression in in vitro cultured HKC cells, which was accompanied by SREBP­1 upregulation. In addition, overexpression of FBXW7 in HKC cells led to SREBP­1 downregulation. By contrast, knockdown of FBXW7 caused SREBP­1 upregulation in HKC cells. It was found that the PI3K/Akt signaling pathway was activated in high glucose­stimulated HKC cells, and inhibition of PI3K/Akt pathway using LY294002 increased FBXW7 expression and decreased SREBP­1 expression. Taken together, the present results suggested that FBXW7 mediated high glucose­induced SREBP­1 expression in renal tubular cells of DN, under the regulation of the PI3K/Akt signaling pathway.

Repression of FBXW7 by HES5 contributes to inactivation of the TGF-ß signaling pathway and alleviation of endometriosis.

Endometriosis (EMS) is a gynecologic disorder associated with infertility and characterized by the endometrial-type mucosa outside the uterine cavity. Currently available treatment modalities are limited to undesirable effects. Thus, in the present study, we sought to study the pathogenesis mechanism of EMS. For this purpose, the ectopic and eutopic endometrial tissues were resected from 86 patients with EMS and 54 infertile patients without EMS, respectively. The regulatory mechanism among HES family bHLH transcription factor 5 (HES5), transforming growth factor-beta (TGF-ß)-induced factor 1 (TGIF1), F-box, and WD repeat domain containing 7 (FBXW7) was studied by performing co-immunoprecipitation, dual-luciferase reporter gene assay, and chromatin immunoprecipitation, respectively. A mouse model of EMS was established to verify the aforementioned regulatory mechanism in vivo. Upregulation of HES5 and TGIF1, as well as downregulation of FBXW7, was observed in EMS endometrial tissues and human endometrial stromal cells (hESCs), respectively. The overexpression of HES5 was found to suppress the FBXW7 transcription and TGIF1 degradation, resulting in the inactivation of the TGF-ß signaling pathway, as well as inhibition of hESC proliferation and invasion, thereby enhancing apoptosis. Results from a mouse model of EMS showed that the presence of HES5 contributed to the alleviation of EMS. Collectively, we attempted to provide a mechanistic insight into the unrecognized roles of the HES5/FBXW7 in EMS progression.

Expression levels of FBXW7 and MDM2 E3 ubiquitin ligases and their c-Myc and p53 substrates in patients with dysplastic nevi or melanoma.

E3 ubiquitin ligases are of interest as drug targets due to their involvement in the regulation of the functions and interactions of several proteins. Various E3 ligase complexes are considered oncogenes or tumor suppressors associated with the development of melanoma. These proteins regulate the functions of various signaling pathways and proteins, such as p53 and Notch. The aim of the present study was to determine the expression levels of F-box and WD repeat domain-containing 7 (FBXW7), c-Myc, MDM2 and p53 proteins in samples from patients with dysplastic nevi or melanoma, and to evaluate their association with clinicopathological parameters and prognosis of the disease. Paraffin blocks with postoperative material from 100 patients diagnosed with dysplastic moles or melanoma were used in the present study. Tissue microarrays and immunohistochemistry were used to examine FBXW7, c-Myc, MDM2 and p53 protein expression. The results revealed that there was significantly lower FBXW7 expression in advanced melanoma compared with dysplastic nevus, melanoma in situ and stage pT1 melanoma (P<0.001). Additionally, there was a statistically significant association between the expression levels of FBXW7 and the morphological type of the tumor (P<0.001). In addition, there was a strong positive association between FBXW7 expression and the changes in c-Myc expression (P<0.02), and a strong trend was observed between decreased FBXW7 expression and a higher risk of death in patients, with the major factor in patient mortality being the stages of melanoma. Additionally, p53 expression was associated with the depth of melanoma invasion and the morphological type of the tumor. In summary, FBXW7 expression exhibited the highest statistically significant prognostic value and associations with advanced melanoma. As the majority of FBXW7 substrates are oncoproteins, their degradation by FBXW7 may highlight these proteins as potential targets for the treatment of melanoma.

MicroRNA­223­induced inhibition of the FBXW7 gene affects the proliferation and apoptosis of colorectal cancer cells via the Notch and Akt/mTOR pathways.

The tumour suppressor gene F­box and WD repeat domain­containing 7 (FBXW7) plays an important role in human cancer by regulating cell division, proliferation and differentiation. However, the exact regulatory mechanisms of microRNA (miR)­223 in colorectal cancer (CRC) cells are still unknown. The present study aimed to investigate the effect and mechanism of miR­223 inhibiting FBXW7 on the proliferation and apoptosis of CRC cells. HCT116 cells were transfected with miR­223 mimics or small interfering RNA (siRNA) targeting FBXW7 (siFBXW7), and the effects of these treatments on cell proliferation and apoptosis were examined. The downstream Notch and Akt/mTOR pathways were also assessed. Following miR­223 overexpression, the mRNA and protein expression levels of FBXW7 were downregulated. Transfection with miR­223 mimics or siFBXW7 promoted the proliferation of HCT116 cells and inhibited apoptosis by promoting the Notch and Akt/mTOR signalling pathways. Conversely, miR­223 mimics transfection with FBXW7 overexpression inhibited cell viability and restored apoptosis. Thus, the present study demonstrated that miR­223 could bind to the FBXW7 gene and inhibit its expression, ultimately increasing the proliferation and preventing the apoptosis of CRC cells through the Notch and Akt/mTOR signalling pathways.

Cell proliferation is induced in renal cell carcinoma through miR-92a-3p upregulation by targeting FBXW7.

Renal cell carcinoma (RCC) is the most common type of kidney cancer whose incidence has gradually increased worldwide. MicroRNAs (miRNAs) represent a type of short endogenous non-coding RNA containing approximately 22 nucleotides, which are capable of regulating mRNAs at the post-transcriptional level in human cells. miRNAs have been demonstrated to mediate gene expression by influencing important regulatory genes. Accumulating evidence indicates that certain miRNAs are involved in RCC development. The present study investigated the underlying mechanism and functional role of miR-92a-3p in RCC cells using reverse transcription-quantitative polymerase chain reaction, western blotting, 3' UTR luciferase assay, cell proliferation assay and soft agar assay. The results demonstrated that miR-92a-3p expression level is significantly upregulated in RCC tissues and cell lines; however, F-box and WD repeat domain containing 7 (FBXW7) expression level was significantly downregulated in RCC tissues and cell lines. Subsequently, whether FBXW7 could be considered as a direct target of miR-92a-3p in RCC cells was investigated. The results demonstrated that miR-92a-3p overexpression significantly promoted RCC cell proliferation and colony formation. Conversely, miR-92a-3p downregulation significantly inhibited RCC cell proliferation and colony formation. In addition, FBXW7 knockdown significantly enhanced RCC cell proliferation and colony formation. Conversely, FBXW7 overexpression significantly inhibited RCC cell proliferation and colony formation. Collectively, these results demonstrated that miR-92a-3p/FBXW7 pathway may represent a novel strategy and therapeutic target for RCC.

Hsa_circ_RNA_0011780 Represses the Proliferation and Metastasis of Non-Small Cell Lung Cancer by Decreasing FBXW7 via Targeting miR-544a.

PURPOSE: Circular RNA (circRNA) is involved in the development of various cancers. However, whether circRNA can inhibit the tumorigenesis of non-small cell lung cancer (NSCLC) is still unclear. We aimed to explore the epigenetic function of tumor-suppressive circRNA (hsa_circ_RNA_0011780) and its downstream regulatory factors in NSCLC. PATIENTS AND METHODS: Quantitative polymerase chain reaction (qPCR) was used to evaluate hsa_circ_11780 expression in NSCLC tissues and cell lines. The impact of high hsa_circ_11780 expression on overall survival in patients with NSCLC was tested using the Log rank test. The association between decreased hsa_circ_11780 expression and clinicopathological features in patients with NSCLC was analyzed using the Chi-squared test. In vitro cell proliferation and apoptosis were assayed using the cell counting kit-8 (CCK-8) and flow cytometry, respectively. Mice xenograft models were used to determine the tumor promoting effects of hsa_circ_11780 on NSCLC in vivo. The underlying regulatory mechanism was predicted by bioinformatics and verified by a dual-luciferase reporter assay, RNA transfection, qPCR, and Western blotting. The correlation between miR-544a and hsa_circ_11780 expression was verified using Spearman correlation coefficient. RESULTS: The expression of hsa_circ_11780 in NSCLC tissues and cell lines strongly declined. Low hsa_circ_11780 expression is more likely to present in patients with a large tumor size (>3cm), distant metastasis, and poor overall survival. hsa_circ_11780 overexpression strongly inhibited proliferation, migration, and invasion of NSCLC cells (H226 and A549) in vitro and inhibited tumor growth in vivo. Furthermore, hsa_circ_11780 repressed miR-544a function by competitively binding to the complementary sites of miR-544a. miR-544a released by the declining expression of hsa_circ_11780 reduced the protein concentration of F-Box and WD repeat domain containing 7 (FBXW7) in NSCLC cells. CONCLUSION: FBXW7 expression mediated by the hsa_circ_11780/miR-544a axis is markedly associated with the proliferation, migration, and invasion of NSCLC, resulting in decreased survival. These findings suggest that this regulatory axis may serve as a novel therapeutic target in NSCLC.

The ubiquitin ligase FBXW7 targets the centriolar assembly protein HsSAS-6 for degradation and thereby regulates centriole duplication.

Formation of a single new centriole from a pre-existing centriole is strictly controlled to maintain correct centrosome number and spindle polarity in cells. However, the mechanisms that govern this process are incompletely understood. Here, using several human cell lines, immunofluorescence and structured illumination microscopy methods, and ubiquitination assays, we show that the E3 ubiquitin ligase F-box and WD repeat domain-containing 7 (FBXW7), a subunit of the SCF ubiquitin ligase, down-regulates spindle assembly 6 homolog (HsSAS-6), a key protein required for procentriole cartwheel assembly, and thereby regulates centriole duplication. We found that FBXW7 abrogation stabilizes HsSAS-6 and increases its recruitment to the mother centriole at multiple sites, leading to supernumerary centrioles. Ultrastructural analyses revealed that FBXW7 is broadly localized on the mother centriole and that its presence is reduced at the site where the HsSAS-6-containing procentriole is formed. This observation suggested that FBXW7 restricts procentriole assembly to a specific site to generate a single new centriole. In contrast, during HsSAS-6 overexpression, FBXW7 strongly associated with HsSAS-6 at the centriole. We also found that SCFFBXW7 interacts with HsSAS-6 and targets it for ubiquitin-mediated degradation. Further, we identified putative phosphodegron sites in HsSAS-6, whose substitutions rendered it insensitive to FBXW7-mediated degradation and control of centriole number. In summary, SCFFBXW7 targets HsSAS-6 for degradation and thereby controls centriole biogenesis by restraining HsSAS-6 recruitment to the mother centriole, a molecular mechanism that controls supernumerary centrioles/centrosomes and the maintenance of bipolar spindles.

miR-25-3p promotes glioma cell proliferation and migration by targeting FBXW7 and DKK3.

MicroRNAs (miRs) serve important roles in glioma. However, the underlying molecular mechanism of miR-25 in glioma progression remains largely unknown; therefore, it was investigated in the present study. RT-qPCR analysis revealed that miR-25 expression levels were markedly increased in human glioma tissue and glioma cell lines compared with normal brain tissues and normal human astrocytes, respectively. miR-25 upregulation exhibited an association with glioma progression, and the knockdown of miR-25 significantly inhibited glioma cell proliferation and migration. F-box and WD repeat domain containing 7 (FBXW7) and dickkopf WNT signaling pathway inhibitor 3 (DKK3) were identified as target genes of miR-25. FBXW7 and DKK3 expression levels were significantly downregulated in glioma tissue samples compared with normal brain tissue, and their expression levels were negatively regulated by miR-25 expression in glioma cells. Furthermore, inhibition of FBXW7 and DKK3 expression suppressed the miR-25-induced effects on glioma cell proliferation and migration. The findings of the present study suggest that miR-25 may promote glioma cell proliferation and migration by inhibiting the expression of FBXW7 and DKK3. Therefore, miR-25 may serve as a promising molecular target for the treatment of glioma.

SCFFbxw7 ubiquitylates KLF7 for degradation in a manner dependent on GSK-3-mediated phosphorylation.

The biological relation between ubiquitin ligases and their substrates has been largely unclear. We previously developed a method-differential proteomics-based identification of ubiquitylation substrates (DiPIUS)-for the comprehensive identification of substrates for a given ubiquitin ligase. We have now applied DiPIUS to the F-box protein Fbxw7 in three cell lines (mHepa, Neuro2A and C2C12) and thereby identified Krüppel-like factor 7 (KLF7) as a candidate substrate of the SCFFbxw7 ubiquitin ligase complex. KLF7 was shown to interact with Fbxw7 and to undergo Fbxw7-mediated polyubiquitylation. The stability of KLF7 was increased by depletion of Fbxw7, mutation of a putative Cdc4 phosphodegron (CPD) of KLF7 or exposure to inhibitors of glycogen synthase kinase-3 (GSK-3). Over-expression of Fbxw7 in Neuro2A cells down-regulated expression of the p21Cip1 gene, which is a transcriptional target of KLF7 in neuronal differentiation and maintenance. Despite the presence of an almost identical CPD sequence in KLF6, the closest paralog of KLF7, mutation of this sequence affected neither the interaction of KLF6 with Fbxw7 nor its half-life. Our results suggest that KLF7, but not KLF6, is a bona fide substrate of SCFFbxw7 , and that control of KLF7 abundance by SCFFbxw7 might contribute to the regulation of neuronal differentiation and maintenance.

FBXW7 expression affects the response to chemoradiotherapy and overall survival among patients with oral squamous cell carcinoma: A single-center retrospective study.

FBXW7 (F-box and WD repeat domain containing-7) is a tumor suppressor protein that regulates the degradation of various oncoproteins in several malignancies. However, limited information is available regarding FBXW7 expression in oral squamous cell carcinoma. Therefore, this study aimed to determine the clinical significance of FBXW7 expression in oral squamous cell carcinoma. The FBXW7 expression patterns in oral squamous cell carcinoma and adjacent normal tissues from 15 patients who underwent radical resection were evaluated using quantitative real-time polymerase chain reaction and immunohistochemical staining. In addition, immunohistochemistry was performed using paraffin-embedded sections from biopsy specimens obtained from 110 patients with oral squamous cell carcinoma who underwent surgery after 5 fluorouracil-based chemoradiotherapy. The associations of FBXW7 expression with various clinicopathological features and prognosis were evaluated in these patients. As a results, in the 15 matched samples, the FBXW7 expression was significantly decreased in the oral squamous cell carcinoma tissues compared to that in the adjacent normal tissues. In the clinicopathological analysis, compared to high protein expression, low FBXW7 expression was found to significantly associate with a poor histological response to preoperative chemoradiotherapy. Kaplan-Meier curve analysis revealed that low FBXW7 expression was significantly associated with a poor prognosis, and FBXW7 expression was found to be an independent predictor of overall survival in the multivariate analysis. Our results suggest that FBXW7 may function as a tumor suppressor protein in oral squamous cell carcinoma. In addition, FBXW7 could be a potential biomarker for predicting not only the clinical response to chemoradiotherapy but also overall survival in patients with oral squamous cell carcinoma.

miR-223 decreases cell proliferation and enhances cell apoptosis in acute myeloid leukemia via targeting FBXW7.

The expression of microRNA-223 (miR-233) has been investigated in various types of cancer. However, to the best of our knowledge, the expression and function of miR-223 in acute myeloid leukemia (AML) remains to be elucidated. The expression of miR-223 was measured by reverse transcription-quantitative polymerase chain reaction. Following transfection with miR-223, cell viability assays, cell apoptosis assays, western blot analysis and luciferase assays were conducted in AML cell lines. In the present study, it was initially observed that miR-223 was downregulated in AML patients compared with healthy subjects. It was also demonstrated that miR-223 inhibited cell proliferation and enhanced cell apoptosis in AML cell lines. Additionally, the present study provided evidence that miR-223 may directly target F-box and WD repeat domain containing 7 in AML. The identification of candidate target genes of miR-223 may provide an understanding of the potential mechanisms underlying the development of AML. In conclusion, the results of the present study have therapeutic implications and may be exploited for further treatment of AML.

Dysfunction of microRNA-32 regulates ubiquitin ligase FBXW7 in multiple myeloma disease.

Dysfunction of microRNA (miRNA) expression has been associated with tumor occurrence, progression, and development. The aim of this work was to study the dysfunction of miR-32 - an miRNA that was abnormally regulated in different tumors - in clinical tissues from patients with multiple myeloma (MM). The tumor tissues in which we assessed miR-32 expression levels were collected during our 5 years of clinical practice. Our study found an increase in miR-32 expression in MM tissues. Assessment of F-box and WD repeat domain-containing 7 (FBXW7) in MM tissues showed an inverse relation between the expression of FBXW7 and miR-32. To further investigate the relation between miR-32 and FBXW7, cells were transfected with miR-32 or anti-miR-32. In vitro studies found that cells transfected with miR-32 showed a lower expression of FBXW7 and a higher expression of cancer-related proteins, c-Jun and c-Myc. In contrast, the cells transfected with anti-miR32 showed a relatively higher expression of FBXW7, but a lower expression of c-Jun and c-Myc. This study may offer perceptive insights into developing new strategies for MM cancer detection and therapy.