CUL4A promotes proliferation and metastasis of colorectal cancer cells by regulating H3K4 trimethylation in epithelial-mesenchymal transition

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 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.

Retinoblastoma-Binding Protein 5 Regulates H3K4 Methylation Modification to Inhibit the Proliferation of Melanoma Cells by Inactivating the Wnt/β-Catenin and Epithelial-Mesenchymal Transition Pathways

Histone 3 lysine 4 methylation (H3K4me), especially histone 3 lysine 4 trimethylation (H3K4me3), is one of the most extensively studied patterns of histone modification and plays crucial roles in many biological processes. However, as a part of H3K4 methyltransferase that participates in H3K4 methylation and transcriptional regulation, retinoblastoma-binding protein 5 (RBBP5) has not been well studied in melanoma. The present study sought to explore RBBP5-mediated H3K4 histone modification and the potential mechanisms in melanoma. RBBP5 expression in melanoma and nevi specimens was detected by immunohistochemistry. Western blotting was performed for three pairs of melanoma cancer tissues and nevi tissues. In vitro and in vivo assays were used to investigate the function of RBBP5. The molecular mechanism was determined using RT-qPCR, western blotting, ChIP assays, and Co-IP assays. Our study showed that RBBP5 was significantly downregulated in melanoma tissue and cells compared with nevi tissues and normal epithelia cells (P < 0.05). Reducing RBBP5 in human melanoma cells leads to H3K4me3 downregulation and promotes cell proliferation, migration, and invasion. On the one hand, we verified that WSB2 was an upstream gene of RBBP5-mediated H3K4 modification, which could directly bind to RBBP5 and negatively regulate its expression. On the other hand, we also confirmed that p16 (a cancer suppressor gene) was a downstream target of H3K4me3, the promoter of which can directly bind to H3K4me3. Mechanistically, our data revealed that RBBP5 inactivated the Wnt/β-catenin and epithelial-mesenchymal transition (EMT) pathways (P < 0.05), leading to melanoma suppression. Histone methylation is rising as an important factor affecting tumorigenicity and tumor progression. Our findings verified the significance of RBBP5-mediated H3K4 modification in melanoma and the potential regulatory mechanisms of melanoma proliferation and growth, suggesting that RBBP5 is a potential therapeutic target for the treatment of melanoma.

Lentivirus-mediated short hairpin RNA interference of CENPK inhibits growth of colorectal cancer cells with overexpression of Cullin 4A

BACKGROUND

Colorectal cancer (CRC) is one of the most common malignant tumors worldwide. The identification of novel diagnostic and prognostic biomarkers for CRC is a key research imperative. Immunohistochemical analysis has revealed high expression of centromere protein K (CENPK) in CRC. However, the role of CENPK in the progression of CRC is not well characterized.

AIM

To evaluate the effects of knockdown of CENPK and overexpression of Cullin 4A (CUL4A) in RKO and HCT116 cells.

METHODS

Human colon cancer samples were collected and tested using a human gene expression chip. We identified CENPK as a potential oncogene for CRC based on bioinformatics analysis. In vitro experiments verified the function of this gene. We investigated the expression of CENPK in RKO and HCT116 cells using quantitative polymerase chain reaction (qPCR), western blot, and flow cytometry. The effect of short hairpin RNA (shRNA) virus-infected RKO cells on tumor growth was evaluated in vivo using quantitative analysis of fluorescence imaging. To evaluate the effects of knockdown of CENPK and overexpression of CUL4A in RKO and HCT116 cells, we performed a series of in vitro experiments, using qPCR, western blot, MTT assay, and flow cytometry.

RESULTS

We demonstrated overexpression of CENPK in human colon cancer samples. CENPK was an independent risk factor in patients with CRC. The downstream genes FBX32, CUL4A, and Yes-associated protein isoform 1 were examined to evaluate the regulatory action of CENPK in RKO cells. Significantly delayed xenograft tumor emergence, slower growth rate, and lower final tumor weight and volume were observed in the CENPK short hairpin RNA virus infected group compared with the CENPK negative control group. The CENPK gene interference inhibited the proliferation of RKO cells in vitro and in vivo. The lentivirus-mediated shRNA interference of CENPK inhibited the proliferation of RKO and HCT116 colon cancer cells, with overexpression of the CUL4A.

CONCLUSION

We indicated a potential role of CENPK in promoting tumor proliferation, and it may be a novel diagnostic and prognostic biomarker for CRC.

Cul4a attenuates LPS-induced acute kidney injury via blocking NF-kB signaling pathway in sepsis

Background

Acute kidney injury (AKI) is a common disease that can develop into end-stage kidney disease. Sepsis is one of the main causes of AKI. Currently, there is no satisfactory way to treat septic AKI. Therefore, we have shown the protective function of Cul4a in septic AKI and its molecular mechanism.

Methods

The cellular and animal models of septic AKI were established by using lipopolysaccharide (LPS). Western blot (WB) was employed to analyze Cul4a expression. RT-qPCR was employed to test the expression of Cul4a, SOD1, SOD2, GPX1, CAT, IL-6, TNF-a, Bcl-2, IL1b, Bax and KIM-1 mRNA. ELISA was performed to detect the contents of inflammatory factors and LDH. CCK-8 was utilized to detect cell viability. Flow cytometry was utilized to analyze the apoptosis. DHE-ROS kit was used to detect the content of ROS.

Results

Cul4a was down-regulated in cellular and animal models of septic AKI. Oxidative stress is obviously induced by LPS, as well as apoptosis and inflammation. However, these can be significantly inhibited by up-regulating Cul4a. Moreover, LPS induced the activation of the NF-kB pathway, which could also be inhibited by overexpression of Cul4a.

Conclusions

Cul4awas found to be a protective factor in septic AKI, which could inhibit LPS-induced oxidative stress, apoptosis and inflammation of HK-2 cells by inhibiting the NF-kB pathway.

Targeting Cullin-RING E3 Ubiquitin Ligase 4 by Small Molecule Modulators

Cullin-RING E3 ubiquitin ligase 4 (CRL4) plays an essential role in cell cycle progression. Recent efforts using high throughput screening and follow up hit-to-lead studies have led to identification of small molecules 33-11 and KH-4-43 that inhibit E3 CRL4's core ligase complex and exhibit anticancer potential. This review provides: 1) an updated perspective of E3 CRL4, including structural organization, major substrate targets and role in cancer; 2) a discussion of the challenges and strategies for finding the CRL inhibitor; and 3) a summary of the properties of the identified CRL4 inhibitors as well as a perspective on their potential utility to probe CRL4 biology and act as therapeutic agents.

CUL4A regulates endometrial cancer cell proliferation, invasion and migration by interacting with CSN6

Endometrial cancer (EC) is a common malignant gynecological tumor arising from the endometrium, with an annually increasing morbidity and mortality. The present study aimed to investigate the functions of cullin 4A (CUL4A) in EC, as well as the underlying mechanisms. CUL4A expression was assessed in several human EC cells and normal human endometrial epithelial cells (hEECs) via reverse transcription‑quantitative polymerase chain reaction and western blotting. Subsequently, short hairpin (sh)RNA‑CULA4 was transfected into cells, and cell proliferation, invasion and migration were detected using Cell Counting kit‑8, Transwell and wound healing assays, respectively. The STRING database identified that CSN6 interacted with CULA4, and immunoprecipitation was performed to verify the interaction. Subsequently, following CUL4A knockdown, pcDNA3.1‑CSN6 was transfected into cells and its effects on cell proliferation, invasion and migration were assessed. The expression levels of matrix metallopeptidase (MMP)2, MMP9 and p53 were evaluated via western blotting. The results indicated that CUL4A was highly expressed in EC cells, compared with hEECs. CULA4‑knockdown notably inhibited EC cell proliferation, invasion and migration. The expression levels of MMP2 and MMP9 were significantly decreased, while p53 expression was enhanced following CUL4A‑knockdown. The immunoprecipitation assay verified that COP9 signalosome subunit 6 (CSN6) interacted with CULA4. Furthermore, CSN6‑overexpression alleviated the inhibitory effects of CUL4A‑knockdown on EC cell proliferation, invasion and migration. Similarly, CSN6 overexpression reversed CUL4A‑knockdown‑mediated effects on the expression of MMP2, MMP9 and p53. In summary, the results demonstrated that CUL4A regulated EC cell proliferation, invasion and migration by interacting with CSN6.

An amino-terminal BRAF deletion accounting for acquired resistance to RAF/EGFR inhibition in colorectal cancer

Although combination therapy with RAF and EGFR inhibitors has improved the survival outcomes of patients with BRAF-mutated colorectal cancer (CRC), acquired resistance invariably develops. The mechanisms of acquired resistance to RAF inhibitors have been largely attributed to activating mutations in RASgenes, MAP2K mutations, and amplifications in BRAF, RAS genes, and EGFR. In this report, we describe a patient with BRAF-mutated CRC who acquired an amino-terminal BRAF deletion involving the Ras-binding domain (RBD) after treatment with RAF/EGFR inhibitor therapy. Amino-terminal BRAF deletions involving the RBD are a rare mechanism of acquired resistance to RAF inhibitors, particularly in CRC for which there is only one prior report in the literature.

Identification and Validation of Stage-Associated PBMC Biomarkers in Breast Cancer Using MS-Based Proteomics

Background: It is well-described that the transcriptome of peripheral blood mononuclear cells (PBMCs) can be altered in the context of many malignancies to allow them avoid the effective immune response, which leads to cancer invasiveness. Here, we used an MS-based strategy to discover biomarkers in the PBMCs of breast cancer (BC) patients and validated them at different stages of BC. Methods: PBMCs were isolated from the breast cancer patients and were cultured alone or co-cultured with breast cancer cell lines. The role of PBMC in the invasion property of breast cancer cells was explored. NF-kB activity was also measured in the co-cultured breast cancer cells. Identification of protein profiles in the secretome and proteome of the co-cultured PBMCs was performed using SWATH mass spectrometry. Pathway enrichment and gene ontology analyses were carried out to look for the molecular pathways correlated with the protein expression profile of PBMCs in the breast cancer patients. Quantitative real-time polymerase chain reaction (qPCR) was performed to validate the candidate genes in the PBMC fraction of the breast cancer patients at the primary and metastatic stages. In silico survival analysis was performed to assess the potential clinical biomarkers in these PBMC subtypes. Results: PBMCs could significantly increase the invasion property of the BC cells concomitant with a decrease in E-cadherin and an increase in both Vimentin and N-cadherin expression. The NF-kB activity in the BC cells significantly increased following co-culturing implying the role of PBMCs in EMT induction. Enrichment analysis showed that the differentially expressed proteins in PBMCs are mainly associated with IL-17, PI3K-Akt, and HIF-1 signaling pathway, in which a set of seven proteins including TMSB4X, HSPA4, S100A9, SRSF6, THBS1, CUL4A, and CANX were frequently expressed. Finally, in silico analysis confirmed that a gene set consisting of S100A9, SRSF6, THBS1, CUL4A, and CANX were found to provide an insight for the identification of metastasis in breast cancer patients. Conclusion: In conclusion, our study revealed that the protein expression profile in PBMCs is a reflection of the proteins expressed in the BC tissue itself; however, the abundance level is different due to the stage of cancer.

High level of H3K4 tri-methylation modification predicts poor prognosis in esophageal cancer

Objectives: An increase in the trimethylation of lysine 4 of histone 3 (H3K4me3) has been reported to be involved in the development of several types of tumors. However, the level and role of H3K4me3 in human esophageal cancer (HEC) remain unknown. Here, we assessed the role and clinical significance of H3K4me3 in HEC.

Methods: The level of H3K4me3 was determined in 15 pairs of HEC and paracancerous tissues by Western blotting. A tissue microarray including samples from 100 HEC patients was analyzed by immunohistochemistry to determine the relationship between the level of H3K4me3 and the clinicopathological features of HEC patients. Then, the levels of H3K4me3 in HEC cells were elevated via knockdown of inhibitor of growth family member 4(Ing4) expression. Finally, the prognostic significance of H3K4me3 levels in HEC patients was further analyzed.

Results: We found that H3K4me3 levels were frequently elevated in HEC tissues compared with adjacent esophageal tissues, and elevated H3K4me3 was significantly associated with poor tumor differentiation (p =1.39×10-5) and advanced tumor stage (p=8.5×10-5). After Ing4 knockdown in HEC cells, we found that the cell proliferation, metastasis, invasion and colony formation abilities were enhanced compared to those in the control cells. Notably, we found that HEC patients with a high level of H3K4me3 exhibited an unfavorable 5-year survival rate compared to those with a low level of H3K4me3 (p=6.8×10-5). The univariate analysis showed that the tumor differentiation, TNM stage, and H3K4me3 level were predictors of the overall survival rate of HEC patients. In the multivariate analysis, tumor stage (p=0.015) and H3K4me3 level (p=0.034) were revealed to be independent parameters for predicting the prognosis of HEC patients.

Conclusions: Thus, high levels of H3K4me3 may be used as a meaningful biomarker for HEC prognosis evaluation.

Cullin 4-DCAF Proteins in Tumorigenesis

Cullin-RING ligase 4 (CRL4), a member of the cullin-RING ligase family, orchestrates a variety of critical cellular processes and pathophysiological events. Recent results from mouse genetics, clinical analyses, and biochemical studies have revealed the impact of CRL4 in development and cancer etiology and elucidated its in-depth mechanism on catalysis of ubiquitination as a ubiquitin E3 ligase. Here, we summarize the versatile roles of the CRL4 E3 ligase complexes in tumorigenesis dependent on the evidence obtained from knockout and transgenic mouse models as well as biochemical and pathological studies.

Small molecule TSC01682 inhibits osteosarcoma cell growth by specifically disrupting the CUL4B-DDB1 interaction and decreasing the ubiquitination of CRL4B E3 ligase substrates

The direct interaction between Cullin 4B (CUL4B) and DNA damage-binding protein 1 (DDB1) is required for the assembly of Cullin4B-RING E3 ligase complex (CRL4B), which are involved in the tumorigenesis of osteosarcoma through ubiquitinating and degrading multiple tumor suppressors and cell cycle regulators. Thus, targeting CUL4B-DDB1 interaction to prevent the assembly of CRL4B may be a potent approach to inhibit osteosarcoma cell growth. In the present study, we identified six naturally-sourced small molecules that can specifically disrupt the CUL4B-DDB1 interaction using an in vitro high-throughput screening (HTS) system in yeast. We focused our investigation on revealing the molecular effects of TSC01682, the most active compound capable of inhibiting osteosarcoma cell growth. Biochemically, TSC01682 significantly repressed the CUL4B-DDB1 interaction in both yeast cells and osteosarcoma cells. Moreover, TSC01682 treatment in osteosarcoma cells also caused a decrease of other CRL4B components including CUL4-associated factor 11 (DCAF11) and DCAF13, but an increase of two CRL4B substrates including cyclin-dependent kinase inhibitor 1A (CDKN1A, also known as p21) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) through inhibiting their ubiquitination. Consistent with these molecular changes, TSC01682 treatment significantly inhibited cell proliferation, colony formation, invasion, and in vivo tumor growth. Collectively, our results suggest that TSC01682 is a potent compound capable of disrupting the CUL4B-DDB1 interaction, and it may be developed as a chemotherapeutic drug for osteosarcoma treatment.

Cul4A Modulates Invasion and Metastasis of Lung Cancer Through Regulation of ANXA10

: Cullin 4A (Cul4A) is overexpressed in a number of cancers and has been established as an oncogene. This study aimed to elucidate the role of Cul4A in lung cancer invasion and metastasis. We observed that Cul4A was overexpressed in non-small cell lung cancer (NSCLC) tissues and the overexpression of Cul4A was associated with poor prognosis after surgical resection and it also decreased the expression of the tumor suppressor protein annexin A10 (ANXA10). The knockdown of Cul4A was associated with the upregulation of ANXA10, and the forced expression of Cul4A was associated with the downregulation of ANXA10 in lung cancer cells. Further studies showed that the knockdown of Cul4A inhibited the invasion and metastasis of lung cancer cells, which was reversed by the further knockdown of ANXA10. In addition, the knockdown of Cul4A inhibited lung tumor metastasis in mouse tail vein injection xenograft models. Notably, Cul4A regulated the degradation of ANXA10 through its interaction with ANXA10 and ubiquitination in lung cancer cells. Our findings suggest that Cul4A is a prognostic marker in NSCLC patients, and Cul4A plays important roles in lung cancer invasion and metastasis through the regulation of the ANXA10 tumor suppressor.

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-1β 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 CRL4^DCAF4 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 CRL4^DCAF4 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.

The emerging role for Cullin 4 family of E3 ligases in tumorigenesis

As a member of the Cullin-RING ligase family, Cullin-RING ligase 4 (CRL4) has drawn much attention due to its broad regulatory roles under physiological and pathological conditions, especially in neoplastic events. Based on evidence from knockout and transgenic mouse models, human clinical data, and biochemical interactions, we summarize the distinct roles of the CRL4 E3 ligase complexes in tumorigenesis, which appears to be tissue- and context-dependent. Notably, targeting CRL4 has recently emerged as a noval anti-cancer strategy, including thalidomide and its derivatives that bind to the substrate recognition receptor cereblon (CRBN), and anticancer sulfonamides that target DCAF15 to suppress the neoplastic proliferation of multiple myeloma and colorectal cancers, respectively. To this end, PROTACs have been developed as a group of engineered bi-functional chemical glues that induce the ubiquitination-mediated degradation of substrates via recruiting E3 ligases, such as CRL4 (CRBN) and CRL2 (pVHL). We summarize the recent major advances in the CRL4 research field towards understanding its involvement in tumorigenesis and further discuss its clinical implications. The anti-tumor effects using the PROTAC approach to target the degradation of undruggable targets are also highlighted.

TRIM37 promotes cell invasion and metastasis by regulating SIP1-mediated epithelial-mesenchymal transition in gastric cancer

Background

Tripartite motif containing 37 (TRIM37) has been demonstrated to function importantly during the progression of various cancers. However, the role of TRIM37 in gastric cancer (GC) remains elusive.

Materials and methods

TRIM37 mRNA and protein expressions were determined by qRT-PCR, Western blot, and immunohistochemical staining in GC specimens. The effects of TRIM37 on GC cells behavior were evaluated by transwell assays in vitro and metastasis assay in vivo, respectively. Besides, qRT-PCR, Western blot, and immunofluorescence staining were employed to detect the expressions of TRIM37 and epithelial–mesenchymal transition (EMT)-related markers.

Results

The present study revealed that TRIM37 mRNA or protein expression was significantly increased in GC tissues compared with that in paracancerous control tissues, and its aberrant overexpression was closely associated with clinical metastasis and poor prognosis in patients with GC. TRIM37 knockdown significantly suppressed GC cells migration and invasion in vitro, as well as metastasis in vivo. Inversely, TRIM37 overexpression exerted the opposite effects. Mechanistic studies suggested that SIP1-mediated EMT might be responsible for TRIM37-facilitated GC cells migration and invasion.

Conclusion

Our findings revealed that high TRIM37 expression was associated with clinical metastasis and poor survival in patients with GC. TRIM37 promoted GC cells migration and invasion via EMT, mediated by the transcription factor SIP1, thus providing a candidate target for GC treatment.