A novel tRNA-derived fragment tRF-3023b suppresses inflammation in RAW264.7 cells by targeting Cul4a through NF-κB signaling.

The role of transfer RNA (tRNA)-derived fragment (tRF) in various diseases has been established. However, the effect of tRF-3023b on inflammation remains unclear. Inflammation was imitated in RAW264.7 cells by adding Lipopolysaccharide (LPS). Cells were first divided into control, LPS, and LPS + Bulleyaconitine A (BLA) groups. The contents of TNF-α, IL-6, and MCP-1 were quantified using ELISA. The levels of cyclooxygenase-2 (COX2), inducible nitric oxide synthase (iNOS), and the phosphorylation of nuclear factor-kappa B (NF-κB)-P65 (p-P65) were detected by Western blotting. RNA sequencing was utilized to find differentially expressed tRFs (DE-tRFs) among three groups. The levels of various tRFs were checked by quantitative real-time PCR (qRT-PCR). Cell cycle and apoptosis were checked by flow cytometry. Dluciferase reporter assay was applied to predict and confirm the interaction between tRF-3023b and Cullin 4A (Cul4a), subsequently RNA pull-down followed by mass spectrometry analysis were conducted. BLA treatment decreased the contents of TNF-α, IL-6, MCP-1, and the expression levels of COX2, iNOS, p-P65. We found 6 DE-tRFs in LPS + BLA group compared to LPS group, tRF-3023b was high expression in control and BLA groups, and the lowest in LPS group. Cul4a was a direct target of tRF-3023b. tRF-3023b mimic affected the cell cycle distribution, promoted cells apoptosis, and suppressed the TNF-α, IL-6, MCP-1, COX2, iNOS and p-P65. The suppression of Cul4a affected the cell cycle distribution, resulted in an increase of cell apoptosis while a decrease of TNF-α, IL-6, MCP-1, COX2, iNOS and p-P65. Furthermore, Cul4a overexpression reversed the effect of tRF-3023b mimic. Cul4a knockdown reversed the effect of tRF-3023b inhibitor. Our study positions tRF-3023b as a compelling candidate, through its interaction with Cul4a, the underlying mechanism on inflammation maybe related to NF-κB pathway. The study provides a basis for exploring new therapeutic strategies for inflammation.

circSNTB2 and CUL4A Induces Dysfunction of Nucleus Pulposus Cells by Competitively Binding miR-665.

Circular RNA (circRNA) plays important roles in lumbar degenerative diseases. This study aimed to investigate the role of circSNTB2 in regulating the development of lumbar disc herniation (LDH) in vitro and in vivo. The abnormally expressed circSNTB2 in intervertebral disc degeneration (IDD) through bioinformatics analysis was identified, and verified in nucleus pulposus (NP) tissues of patients with LDH. NP cells were treated with TNF-α to mimic the LDH microenvironment. RT-qPCR was applied to determine levels of mRNA and microRNA (miRNA) in clinical samples and cells. We performed CCK-8, EdU, TUNEL and flow cytometric apoptosis assays to evaluate the proliferation and apoptosis of NP cells. The predicted the miRNAs and downstream target genes were verified with the help of luciferase reporter gene and RNA pull-down experiments. Finally, we established an LDH rat model to further verify the role of circSNTB2 in vivo. circSNTB2 was significantly up-regulated in the NP tissues of LDH group and TNF-α -treated NP cells. miR-665 binds to circSNTB2 and cullin 4A (CUL4A) is the downstream target gene of miR-665. Knockdown of circSNTB2 promoted NP cells proliferation and inhibited apoptosis, which was reversed by down-regulation of miR-665. In addition, up-regulated CUL4A reversed the effects of over-expressed miR-665 on proliferation and apoptosis of NP cells. Meanwhile, results of in vivo experiments demonstrated that knocking down circSNTB2 alleviated LDH-induced thermo-mechanical pain and NP injury. In summary, circSNTB2 regulates the proliferation and apoptosis of NP by mediating miR-665 regulation of CUL4A, which provides a reliable idea for targeted therapy of LDH.

CUL4A silencing attenuates cervical carcinogenesis and improves Cisplatin sensitivity.

CUL4A is an ubiquitin ligase deregulated in numerous pathologies including cancer and even hijacked by viruses for facilitating their survival and propagation. However, its role in Human papilloma virus (HPV)-mediated cervical carcinogenesis remains elusive. The UALCAN and GEPIA datasets were analyzed to ascertain the transcript levels of CUL4A in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) patients. Subsequently, various biochemical assays were employed to explore the functional contribution of CUL4A in cervical carcinogenesis and to shed some light on its involvement in Cisplatin resistance in cervical cancer. Our UALCAN and GEPIA datasets analyses reveal elevated CUL4A transcript levels in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) patients that correlate with adverse clinicopathological parameters such as tumor stage and lymph node metastasis. Kaplan-Meier plot and GEPIA assessment depict poor prognosis of CESC patients having high CUL4A expression. Varied biochemical assays illustrate that CUL4A inhibition severely curtails hallmark malignant properties such as cellular proliferation, migration, and invasion of cervical cancer cells. We also show that CUL4A knockdown in HeLa cells causes increased susceptibility and better apoptotic induction toward Cisplatin, a mainstay drug used in cervical cancer treatment. More interestingly, we find reversion of Cisplatin-resistant phenotype of HeLa cells and an augmented cytotoxicity towards the platinum compound upon CUL4A downregulation. Taken together, our study underscores CUL4A as a cervical cancer oncogene and illustrates its potential as a prognosis indicator. Our investigation provides a novel avenue in improving current anti-cervical cancer therapy and overcoming the bottle-neck of Cisplatin resistance.

CUL4A-mediated ZEB1/microRNA-340-5p/HMGB1 axis promotes the development of osteoporosis.

Understanding the molecular mechanisms underlying osteoclast differentiation provides insights into bone loss and even osteoporosis. The specific mechanistic actions of cullin 4A (CUL4A) in osteoclast differentiation and resultant osteoporosis is poorly explored. We developed a mouse model of osteoporosis using bilateral ovariectomy (OVX) and examined CUL4A expression. It was noted that CUL4A expression was increased in the bone marrow of OVX mice. Overexpression of CUL4A promoted osteoclast differentiation, and knockdown of CUL4A alleviated osteoporosis symptoms of OVX mice. Bioinformatic analyses were applied to identify the downstream target genes of microRNA-340-5p (miR-340-5p), followed by interaction analysis. The bone marrow macrophages (BMMs) were isolated from femur of OVX mice, which were transfected with different plasmids to alter the expression of CUL4A, Zinc finer E-box binding homeobox 1 (ZEB1), miR-340-5p, and Toll-like receptor 4 (TLR4). ChIP assay was performed to detect enrichment of ZEB1 promoter by H3K4me3 antibody in BMMs. ZEB1 was overexpressed in the bone marrow of OVX mice. Overexpression of CUL4A mediated H3K4me3 methylation to increase ZEB1 expression, thus promoting osteoclast differentiation. Meanwhile, ZEB1 could inhibit miR-340-5p expression and upregulate HMGB1 to induce osteoclast differentiation. Overexpressed ZEB1 activated the TLR4 pathway by regulating the miR-340-5p/HMGB1 axis to induce osteoclast differentiation, thus promoting the development of osteoporosis. Overall, E3 ubiquitin ligase CUL4A can upregulate ZEB1 to repress miR-340-5p expression, leading to HMGB1 upregulation and the TLR4 pathway activation, which promotes osteoclast differentiation and the development of osteoporosis.

lncRNA SNHG11 Promotes Gastric Cancer Progression by Activating the Wnt/ß-Catenin Pathway and Oncogenic Autophagy.

Long non-coding RNAs (lncRNAs) are under active investigation in the development of cancers, including gastric cancer (GC). Oncogenic autophagy is required for cancer cell survival. The present study aimed to investigate the regulatory role of lncRNA small nucleolar host gene 11 (SNHG11) in GC. We show that SNHG11 is upregulated in GC, and that its upregulation correlated with dismal patient outcomes. Functionally, SNHG11 aggravated oncogenic autophagy to facilitate cell proliferation, stemness, migration, invasion, and epithelial-to-mesenchymal transition (EMT) in GC. Mechanistically, SNHG11 post-transcriptionally upregulated catenin beta 1 (CTNNB1) and autophagy related 12 (ATG12) through miR-483-3p/miR-1276, while the processing of precursor (pre-)miR-483/pre-miR-1276 was hindered by SNHG11. SNHG11 induced GSK-3ß ubiquitination through interacting with Cullin 4A (CUL4A) to further activate the Wnt/ß-catenin pathway. Intriguingly, SNHG11 regulated autophagy in a manner dependent on ATG12 rather than the Wnt/ß-catenin pathway, whereas SNHG11 contributed to the malignant behaviors of GC cells via both pathways. Finally, SNHG11 upregulation in GC cells was shown to be transcriptionally induced by TCF7L2. In conclusion, we reveal that SNHG11 is an onco-lncRNA in GC and might be a promising prognostic and therapeutic target for GC.

Inflammation-dependent overexpression of c-Myc enhances CRL4DCAF4 E3 ligase activity and promotes ubiquitination of ST7 in colitis-associated cancer.

Inflammation is well known as an important driver of the initiation of colitis-associated cancer (CAC). Some cytokines, such as IL-6 and TNF-α can activate expression of the oncogene c-Myc (MYC) and regulate its downstream effects. Cullin-RING E3 Ligases (CRLs) are emerging as master regulators controlling tumorigenesis. Here, we demonstrate that two cullin genes, CUL4A and CUL4B, but not other members, are specifically overexpressed in CAC tumour samples and positively correlate with levels of the proinflammatory cytokines IL-1ß and IL-6. In vitro experiments revealed that the transcription factor c-Myc can specifically activate the expression of CUL4A and CUL4B by binding to a conserved site (CACGTG) located in their promoters. Additionally, we found that both CUL4A and CUL4B can form an E3 complex with DNA damage-binding protein 1 (DDB1) and DDB1-CUL4-associated factor 4 (DCAF4). In vitro and in vivo ubiquitination analyses indicate that CRL4DCAF4 E3 ligase specifically directs degradation of ST7 (suppression of tumorigenicity 7). Overexpression of c-Myc in human colon epithelial cells resulted in the accumulation of CUL4A, CUL4B and DCAF4, but degradation of ST7. In contrast, knockdown of c-Myc, CUL4A or CUL4B in the colon adenocarcinoma cell line HT29 caused accumulation of ST7 and inhibition of cell proliferation, colony formation ability and in vivo tumour growth. Collectively, our results provide in vitro and in vivo evidence that c-Myc regulates CRL4DCAF4 E3 ligase activity to mediate ubiquitination of ST7, whose presence is physiologically essential for CAC tumorigenesis. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Inflammation-dependent downregulation of miR-194-5p contributes to human intervertebral disc degeneration by targeting CUL4A and CUL4B.

Inflammation is one of the major causes of intervertebral disc degeneration (IDD). Emerging evidence has revealed that increase in the levels of pro-inflammatory cytokines, such as interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α), can activate a variety of signaling pathways, eventually resulting in IDD. Here, we show that the two cullin family genes, CUL4A and CUL4B, but not other cullins, are specifically overexpressed in IDD samples compared with healthy controls, and the CUL4A and CUL4B levels are positively correlated with the severity of IDD. In vitro analyses in human osteoblast cells (hFOB1.19), nucleus pulposus cells (hNPCs), and annulus fibrosus cells (hAFCs) indicated that treatment with IL-6 and TNF-α can increase CUL4A and CUL4B levels. By performing a microRNA-based microarray analysis, we found a set of microRNAs (miRNAs) that were differentially expressed in IDD samples compared with samples from healthy controls. Of these miRNAs, miR-194-5p, was significantly downregulated in IDD samples and could bind to the three prime untranslated regions (3'-UTRs) of both CUL4A and CUL4B, thereby downregulating their expression. The in vitro overexpression or downregulation of miR-194-5p, with a miR-194-5p-mimic or with anti-miR-194-5p, can cause the repression or induction of both CUL4A and CUL4B, respectively. Interestingly, treatment with IL-6 and TNF-α inhibitors in primary hNPCs and hAFCs that were isolated from patients with IDD led to the downregulation of CUL4A and CUL4B. Together, these findings provide insight into how the inflammation-dependent downregulation of miR-194-5p contributes to the pathogenesis of IDD, which may aid in the development of new therapeutic approaches for IDD by directly targeting miR-194-5p or CUL4A and CUL4B.

KDM5D inhibit epithelial-mesenchymal transition of gastric cancer through demethylation in the promoter of Cul4A in male.

Gastric cancer is one of the top causes of cancer-related death around the world, and poor prognosis of gastric cancer is due to the lack of early detection and effective treatment especially in male. Here, we first revealed the role of histone lysine-specific demethylase 5D (KDM5D) in gastric cancer in male. KDM5D was associated with the metastasis of gastric cancer because of its critical role in the epithelial-mesenchymal transition of gastric cancer cells. Downregulation of KDM5D in gastric cancer cells significantly increase the number of migrated or invaded cells due to the increasing expressions of mesenchymal markers. Downregulation of KDM5D also promotes tumor formation of gastric cancer cell in vivo. For mechanism, downregulation of KDM5D could inhibit the demethylation in the promoter of CUL4A, which lead to the increasing expression of ZEB1 and decreasing expressions of p21 and p53. Collectively, KDM5D performed its role in metastasis of gastric cancer through demethylation in the promoter of CUL4A, and it suggested us a novel target in gastric cancer treatment in male.

The cullin4A is up-regulated in chronic obstructive pulmonary disease patient and contributes to epithelial-mesenchymal transition in small airway epithelium.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a common respiratory disease with high morbidity and mortality. The most important pathophysiological change of COPD is airway obstruction. Airway obstruction can cause airflow restriction and obstructive ventilation dysfunction. Currently, many studies have shown that there is EMT phenomenon in the process of airway remodeling of COPD. Cullin4A (CUL4A) is an E3 ubiquitin ligase that interacts with other factors to form the E3 complex. Studies have shown that CLU4A is associated with EMT in non-small cell lung cancer and other cancers. However, its relationship with EMT in COPD has not been reported systematically. In this study, we detected the expression of CUL4A in lung epithelium of COPD patients. In addition, the regulatory effect and mechanism of CUL4A on EMT in COPD were clarified in small airway epithelial cells. METHODS: The expression of CUL4A was assessed by immunohistochemistry in lung epithelium specimens from smokers, non-smokers and patients with chronic obstructive pulmonary disease. The role of CUL4A on cigarette smoke extract (CSE)-induced epithelial-mesenchymal transition (EMT) in human small airway epithelial cells (HSAEpiCs) was assessed by silencing or overexpression CUL4A in vitro. Cigarette smoke is recognized as a high-risk factor in the induction of COPD, and its damage to the airway involves airway damage, airway inflammation and airway remodeling. RESULTS: The results shown that CUL4A expression in small airway epithelium was significantly increased in patients with COPD. We also observed a significant negative association between CUL4A and FEV1%, a useful clinical marker for the diagnosis and evaluation of COPD severity, in small airway epithelial cells. In vitro, CSE-induced EMT is associated with high expression of CUL4A, and targeted silencing of CUL4A with shRNA inhibits CSE-induced EMT in human small airway epithelial cells. CONCLUSIONS: Our results showed that CUL4A was overexpressed in lung epithelium of COPD patients, and CUL4A could regulate EMT of human small airway epithelium, which revealed a new mechanism of remodeling of small airway epithelium of COPD patients.

CENP-A Ubiquitylation Contributes to Maintaining the Chromosomal Location of the Centromere.

The centromere plays an essential role in accurate chromosome segregation, and the chromosomal location of the centromere is determined by the presence of a histone H3 variant, centromere protein A (CENP-A), in centromeric nucleosomes. However, the precise mechanisms of deposition, maintenance, and inheritance of CENP-A at centromeres are unclear. We have reported that CENP-A deposition requires ubiquitylation of CENP-A lysine 124 mediated by the E3 ligase activity of Cullin 4A (CUL4A)-RING-box protein 1 (RBX1)-COP9 signalsome complex subunit 8 (COPS8). We have proposed a model of inheritance for CENP-A ubiquitylation, through dimerization between rounds of cell divisions, that maintains the position of centromeres.

High Expressions of CUL4A and TP53 in Colorectal Cancer Predict Poor Survival.

BACKGROUND/AIMS: Cullin 4A (CUL4A) is vital in cell survival, development, growth and cell cycle, it plays an important role in chaperone-mediated ubiquitination and interacts with TP53 in carcinogenesis. However, the clinicopathologic significance of CUL4A expression in colorectal cancer is unknown; in particular, the prognostic value of CUL4A combined with TP53 expression has not been explored. METHODS: We analyzed the expression of CUL4A in both public database (Oncomine) and 180 cases of colorectal cancer and paired normal tissues by real-time polymerase chain reaction and western blotting. Colony formation, wound healing, migration and invasion assays and tumorigenesis in nude mice were used to explore the function of CUL4A in CRC proliferation and metastasis in vitro and in vivo. Markers of epithelial to mesenchymal transition (EMT) were evaluated by western blotting. Immunohistochemistry (IHC) was used to analyse the relationship between CUL4A expression and E-cadherin expression. RESULTS: CUL4A and TP53 protein expression was significantly higher in cancerous tissues compared to normal tissues. Significant correlation between CUL4A and TP53 expression was observed. CUL4A expression was an independent prognostic factor for overall survival (OS) and disease-free survival (DFS). Interestingly, patients with tumors that had both CUL4A overexpression and mutant TP53 protein accumulation relapsed and died within a significantly short period after surgery (P < 0.001). Multivariate analysis showed that patients with both CUL4A+ and TP53+ positive tumors had extremely poor OS and DFS. Knockdown of CUL4A by a short interfering RNA (siRNA) significantly suppressed the progression of EMT, proliferation, migration, and invasion of colon cancer cells in vitro and tumor growth in vivo. ZEB1 silencing blocked CUL4A-driven these processes. CONCLUSION: CUL4A expression correlated positively with the prognosis of colorectal cancer. Mechanistically, ZEB1 was confirmed to mediate the function of CUL4A in regulating the EMT. The assessment of both CUL4A and mutant TP53 expression will be helpful in predicting colon cancer prognosis.

CUL4A overexpression as an independent adverse prognosticator in intrahepatic cholangiocarcinoma.

BACKGROUND: CUL4A has been known for its oncogenic properties in various human cancers. However, its role in intrahepatic cholangiocarcinoma (iCCA) has not been explored. METHODS: We retrospectively investigated 105 iCCA cases from a single medical institution. Tissue microarrays were used for immunohistochemical analysis of CUL4A expression. CUL4A expression vectors were introduced in cell lines. Cell migration and invasion assays were used to compare the mobility potential of iCCA cells under basal conditions and after manipulation. Then we evaluated the effects of CUL4A on the cell growth by proliferation assay, and further checked the susceptibility to cisplatin in iCCA cells with or without CUL4A overexpression. RESULTS: CUL4A overexpression was detected in 34 cases (32.4%). Patients with CUL4A-overexpressing tumors exhibited shortened disease-free survival (mean, 27.7 versus 90.4 months; P = 0.011). In the multivariate analysis model, CUL4A overexpression was shown to be an independent unfavorable predictor for disease-free survival (P = 0.045). Moreover, stably transfected CUL4A-overexpressing iCCA cell lines displayed an increased mobility potential and enhanced cell growth without impact on susceptibility to cisplatin. CONCLUSIONS: Our data demonstrate that overexpression of CUL4A plays an oncogenic role in iCCA and adversely affects disease-free survival. Thus, it may prove to be a powerful prognostic factor and a potential therapeutic target.

Knockdown of cullin 4A inhibits growth and increases chemosensitivity in lung cancer cells.

Cullin 4A (Cul4A) has been observed to be overexpressed in various cancers. In this study, the role of Cul4A in the growth and chemosensitivity in lung cancer cells were studied. We showed that Cul4A is overexpressed in lung cancer cells and tissues. Knockdown of the Cul4A expression by shRNA in lung cancer cells resulted in decreased cellular proliferation and growth in lung cancer cells. Increased sensitivity to gemcitabine, a chemotherapy drug, was also noted in those Cul4A knockdown lung cancer cells. Moreover, increased expression of p21, transforming growth factor (TGF)-ß inducible early gene-1 (TIEG1) and TGF beta-induced (TGFBI) was observed in lung cancer cells after Cul4A knockdown, which may be partially related to increased chemosensitivity to gemcitabine. G0/G1 cell cycle arrest was also noted after Cul4A knockdown. Notably, decreased tumour growth and increased chemosensitivity to gemcitabine were also noted after Cul4A knockdown in lung cancer xenograft nude mice models. In summary, our study showed that targeting Cul4A with RNAi or other techniques may provide a possible insight to the development of lung cancer therapy in the future.

CUL4A functions as an oncogene in ovarian cancer and is directly regulated by miR-494.

Cullin 4A (CUL4A), as a well-defined oncogene, has been reported to be upregulated in ovarian cancer clinically. However, the biological functions of CUL4A and the molecular mechanism underlying its upregulation in ovarian cancer remains unknown throughly. Here, we show that expression of CUL4A is significantly higher in ovarian cancer tissues compared to corresponding non-cancerous tissues. Moreover, silencing of CUL4A by siRNA markedly inhibits cell proliferation, invasion and epithelial-mesenchymal transition (EMT). We identified CUL4A as a novel target gene of miR-494. Further investigations showed that miR-494 was remarkably downregulated and correlated with poor prognosis in ovarian cancer. Overexpression of miR-494 inhibited proliferation, migration, invasion and EMT of ovarian cancer cells by directly suppressing CUL4A expression. Therefore, our findings indicate that miR-494/CUL4A axis is important in the control of ovarian cancer tumorigenesis.

CUL4A expression in pediatric osteosarcoma tissues and its effect on cell growth in osteosarcoma cells.

Osteosarcoma (OS) is the most common bone malignancy in the pediatric population, and it comprises about 3 % of all pediatric tumors. Aberrant expression of the Cullin 4A (CUL4A) is found in many tumor types, but the role of CUL4A in OS progression remains largely unknown. The aim of this study was to investigate the expression and function of CUL4A in OS. CUL4A expression was detected in 30 samples of surgically resected OS and matched tumor-adjacent tissues using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot. Cell proliferation was assessed by MTT, and migration and invasion were analyzed by Transwell and Matrigel assays after CUL4A knockdown in OS in vitro. Our result showed increased CUL4A expression in OS tissues. CUL4A knockdown inhibited the proliferation of MG63 cells. Furthermore, CUL4A siRNA ameliorated the migration and invasion of MG63 cell lines with altered expression of epithelial-mesenchymal transition (EMT)-associated molecules. Taken together, our findings indicate that CUL4A plays a pivotal role in OS progression and may serve as a potential marker for clinical diagnosis and target for therapy.

Cul4A overexpression associated with Gli1 expression in malignant pleural mesothelioma.

Malignant pleural mesothelioma (mesothelioma) is a highly aggressive cancer without an effective treatment. Cul4A, a scaffold protein that recruits substrates for degradation, is amplified in several human cancers, including mesothelioma. We have recently shown that Cul4A plays an oncogenic role in vitro and in a mouse model. In this study, we analysed clinical mesothelioma tumours and found moderate to strong expression of Cul4A in 70.9% (51/72) of these tumours, as shown by immunohistochemistry. In 72.2% mesothelioma tumours with increased Cul4A copy number identified by fluorescence in situ hybridization analysis, Cul4A protein expression was moderate to strong. Similarly, Cul4A was overexpressed and Cul4A copy number was increased in human mesothelioma cell lines. Because Gli1 is highly expressed in human mesothelioma cells, we compared Cul4A and Gli1 expression in mesothelioma tumours and found their expression associated (P < 0.05, chi-square). In mesothelioma cell lines, inhibiting Cul4A by siRNA decreased Gli1 expression, suggesting that Gli1 expression is, at least in part, regulated by Cul4A in mesothelioma cells. Our results suggest a linkage between Cul4A and Gli1 expression in human mesothelioma.

Clinical significance of CUL4A in human prostate cancer.

Aberrant expression of the Cullin 4A (CUL4A) is found in many tumor types, but the functions and mechanism of CUL4A in prostate cancer (PCa) development and progression remain largely unknown. The aim of this study was to investigate the possible role of CUL4A in prostate tumorigenesis. Immunohistochemistry was used to examine CUL4A expression in human PCa tissues and BPH tissues. Cell proliferation was assessed by MTT, and migration and invasion were analyzed by Transwell and Matrigel assays after CUL4A knockdown in PCa in vitro. The results showed that CUL4A protein was overexpressed in 86.21 % of PCa tissues. CUL4A knockdown with siRNA in PCa cells decreased cell proliferation, migration, and invasion. Mechanistically, CUL4A could modulate the expression of P53 in PCa cells. Our results indicate that CUL4A overexpression play an oncogenic role in the pathogenesis of PCa, and CUL4A may be a potential therapeutic target for PCa.

Lung tumourigenesis in a conditional Cul4A transgenic mouse model.

Cullin4A (Cul4A) is a scaffold protein that assembles cullin-RING ubiquitin ligase (E3) complexes and regulates many cellular events, including cell survival, development, growth and cell cycle control. Our previous study suggested that Cul4A is oncogenic in vitro, but its oncogenic role in vivo has not been studied. Here, we used a Cul4A transgenic mouse model to study the potential oncogenic role of Cul4A in lung tumour development. After Cul4A over-expression was induced in the lungs for 32 weeks, atypical epithelial cells were observed. After 40 weeks, lung tumours were visible and were characterized as grade I or II adenocarcinomas. Immunohistochemistry (IHC) revealed decreased levels of Cul4A-associated proteins p21(CIP1) and tumour suppressor p19(ARF) in the lung tumours, suggesting that Cul4A regulated their expression in these tumours. Increased levels of p27(KIP1) and p16(INK4a) were also detected in these tumours. Moreover, the protein level of DNA replication licensing factor CDT1 was decreased. Genomic instability in the lung tumours was further analysed by the results from pericentrin protein expression and array comparative genomic hybridization analysis. Furthermore, knocking down Cul4A expression in lung cancer H2170 cells increased their sensitivity to the chemotherapy drug cisplatin in vitro, suggesting that Cul4A over-expression is associated with cisplatin resistance in the cancer cells. Our findings indicate that Cul4A is oncogenic in vivo, and this Cul4A mouse model is a tool in understanding the mechanisms of Cul4A in human cancers and for testing experimental therapies targeting Cul4A.

Knockdown of CUL4A inhibits invasion and induces apoptosis in osteosarcoma cells.

Cullin4A (CUL4A) is implicated in many cellular events including cell survival and growth. However, the specific function and underlying mechanisms of CUL4A in cancer invasion have not yet been elucidated. In this work, we were focused on investigating the role of CUL4A in human osteosarcoma (OS). The expression level of CUL4A was evaluated by immunohistochemical (IHC) assay in human OS tissues. Lentivirus-mediated CUL4A shRNA (Lv-shCUL4A) constructed by us was transfected into OS cells for assessing its effects on cell proliferation and invasive potential, respectively detected by MTT and Transwell assays. It was demonstrated that the expression of CUL4A protein was markedly increased in OS tissues compared with the adjacent non-cancerous tissues (ANCT) (57.8% vs. 25.6%, P = 0.019), and was associated with the distant metastases in OS patients (P = 0.016). In vitro, silencing of CUL4A gene inhibited OS cell proliferation and invasion, and induced cell apoptosis, followed by increased expression of p27 and p53 and decreased expression of MMP-2. Therefore, these findings indicate that elevated expression of CUL4A is positively correlated with distant metastases in OS patients, and knockdown of CUL4A suppresses invasion and induces apoptosis in OS cells, suggesting that CUL4A may serve as a potential target for the treatment of OS.

CUL4A Ubiquitin Ligase Is an Independent Predictor of Overall Survival in Pancreatic Adenocarcinoma.

BACKGROUND/AIM: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with dismal prognosis. Genomic instability due to defects in cell-cycle regulation/mitosis or deficient DNA-damage repair is a major driver of PDAC progression with clinical relevance. Deregulation of licensing of DNA replication leads to DNA damage and genomic instability, predisposing cells to malignant transformation. While overexpression of DNA replication-licensing factors has been reported in several human cancer types, their role in PDAC remains largely unknown. We aimed here to examine the expression and prognostic significance of the DNA replication-licensing factors chromatin licensing and DNA replication factor 1 (CDT1), cell-division cycle 6 (CDC6), minichromosome maintenance complex component 7 (MCM7) and also of the ubiquitin ligase regulator of CDT1, cullin 4A (CUL4A), in PDAC. MATERIALS AND METHODS: Expression levels of CUL4, CDT1, CDC6 and MCM7 were evaluated by immunohistochemistry in 76 formalin-fixed paraffin-embedded specimens of PDAC patients in relation to DNA-damage response marker H2AX, clinicopathological parameters and survival. We also conducted bioinformatics analysis of data from online available databases to corroborate our findings. RESULTS: CUL4A and DNA replication-licensing factors were overexpressed in patients with PDAC and expression of CDT1 positively correlated with H2AX. Expression of CUL4A and CDT1 positively correlated with lymph node metastasis. Importantly, elevated CUL4A expression was associated with reduced overall survival and was an independent indicator of poor prognosis on multivariate analysis. CONCLUSION: Our findings implicate CUL4A, CDT1, CDC6 and MCM7 in PDAC progression and identify CUL4A as an independent prognostic factor for this disease.