A functional reference map of the RNF8 interactome in cancer

Ubiquitination and deubiquitination: Implications for the pathogenesis and treatment of osteoarthritis

Osteoarthritis (OA) is a degenerative disease that affects multiple cells and associated extracellular matrix (ECM). Chondrocytes and chondroextracellular matrix together constitute articular cartilage tissue. Any factors that affect the activity of chondrocytes and destroy the metabolic balance of the chondrocyte ECM will lead to the inability of articular cartilage to perform normal functions. The articular subchondral bone and articular cartilage must be coordinated to resist enough friction and mechanical stress, so the articular subchondral bone lesion will aggravate the articular cartilage defect and vice versa. Synoviocytes, including fibroblast-like synoviocytes (FLSs) and synovial macrophages at the joint, are also important factors that cause low-grade chronic progressive inflammation of OA. Regulation of phenotype transformation of synovial macrophages has become another possible target for the clinical treatment of OA. Ubiquitination and deubiquitination are the main post-translational protein modification pathways in the human body, which are widely involved in multiple signaling pathways and physiological processes. Naturally, they also play a very important regulatory role in the occurrence and development of OA. These effects are summarized in this review, including (A) regulating the aging and apoptosis of chondrocytes, FLSs and osteoblasts; (B) regulation of ECM degradation; (C) regulation of macrophage phenotypic transformation; (D) modulation of skeletal muscle and adipose tissues. Ubiquitination targeting drugs for OA treatment are also listed. Depending on the high efficiency of ubiquitination and deubiquitination, understanding OA-related ubiquitination pathways can help design more efficient drugs to treat OA and provide more potential targets for clinical treatment. The Translational Potential of This Article. In this paper, the ubiquitination-related pathways in osteoarthritis (OA), including aging, apoptosis and autophagy in chondrocytes, osteoblasts, FLSs and macrophages were investigated. In particular, several ubiquitination-related targets are expected to be effective approaches for OA clinical treatment. In addition, in the process of OA occurrence and development, the complex relationship between the local joint area and other tissues including skeletal muscle and adipose tissue is also discussed. These myokines and adipokines from musculoskeletal tissues are all expected to become efficient targets for OA treatment apart from the joint itself. In addition, those myokines secreted by cardiovascular tissues would show potential therapeutic effects as well. What if altering the contents for these ubiquitination-related targets in the serum through exercise will provide a new idea for OA therapy or prevent OA from deteriorating continuously?

Genomic and transcriptomic profiling of hepatocellular carcinoma reveals a rare molecular subtype

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide, occurring predominantly in patients with underlying chronic liver disease and cirrhosis. Here, we describe a case of a 62-year-old man that was admitted to our hospital and diagnosed with HCC where the cancer has already metastasized to the retroperitoneum and peritoneum. In order to better characterize the HCC, both the cancerous liver tissue and the adjacent normal liver tissue of the patient were collected and subjected to a genomic, transcriptomic and proteomic analysis. Our patient carries a highly mutated HCC, which is characterized by both somatic mutation in the following genes ALK, CDK6, TP53, PGR. In addition, we observe several molecular alterations that are associated with potential therapy resistance, for example the expression of the organic-anion-transporting polypeptide (OATP) family members B1 and B3, that mediate the transport of the anticancer drugs, has been found decreased. Overall, our molecular profiling potentially classify the patient with poor prognosis and possibly displaying resistance to pharmacological therapy.

Hyperoside Inhibits RNF8-mediated Nuclear Translocation of β-catenin to Repress PD-L1 Expression and Prostate Cancer

BACKGROUND

Hyperoside is a flavonol glycoside isolated from Hypericum perforatum L. that has inhibitory effects on cancer cells; however, its effects on prostate cancer (PCa) remain unclear. Therefore, we studied the anti-PCa effects of hyperoside and its underlying mechanisms in vitro and in vivo.

AIM

This study aimed to explore the mechanism of hyperoside in anti-PCa.

METHODS

3-(4,5-Dimethyl-2-Thiazolyl)-2,5-Diphenyl Tetrazolium Bromide (MTT), transwell, and flow cytometry assays were used to detect PCa cell growth, invasion, and cell apoptosis. Immunoblot analysis, immunofluorescence, immunoprecipitation, and quantitative real-time PCR (qRT-PCR) were used to analyze the antitumor mechanism of hyperoside.

RESULTS

Hyperoside inhibited PCa cell growth, invasion, and cell cycle and induced cell apoptosis. Furthermore, RING finger protein 8 (RNF8), an E3 ligase that assembles K63 polyubiquitination chains, was predicted to be a direct target of hyperoside and was downregulated by hyperoside. Downregulation of RNF8 by hyperoside impeded the nuclear translocation of β-catenin and disrupted the Wnt/β-catenin pathway, which reduced the expression of the target genes c-myc, cyclin D1, and programmed death ligand 1 (PD-L1). Decreased PD-L1 levels contributed to induced immunity in Jurkat cells in vitro. Finally, in vivo studies demonstrated that hyperoside significantly reduced tumor size, inhibited PD-L1 and RNF8 expression, and induced apoptosis in tumor tissues of a subcutaneous mouse model.

CONCLUSION

Hyperoside exerts its anti-PCa effect by reducing RNF8 protein, inhibiting nuclear translocation of β-catenin, and disrupting the Wnt/β-catenin pathway, in turn reducing the expression of PD-L1 and improving Jurkat cell immunity.

Zooming into the structure-function of RING finger proteins for anti-cancer therapeutic applications

Cancer is one of the most common and widely diagnosed diseases worldwide. With an increase in prevalence and incidence, many studies in cancer biology have been looking at the role pro-cancer proteins play. One of these proteins is the Really Interesting New Gene (RING), which has been studied extensively due to its structure and functions such as apoptosis, neddylation, and its role in ubiquitination. The RING domain is a cysteine-rich domain known to bind Cysteine and Histidine residues. It also binds two zinc ions that help stabilize the protein in various patterns, often with a 'cross-brace' topology. Different RING finger proteins have been studied and found to have suitable targets for developing anti-cancer therapeutics. These identified candidate proteins include Parkin, COP1, MDM2, BARD1, BRCA-1, PIRH2, c-CBL, SIAH1, RBX1 and RNF8. Inhibiting these candidate proteins provides opportunities for shutting down pathways associated with tumour development and metastasis.

RNF8 depletion attenuates hepatocellular carcinoma progression by inhibiting epithelial-mesenchymal transition and enhancing drug sensitivity

Despite substantial advances that have been made in understanding the etiology of hepatocellular carcinoma (HCC), the early-stage diagnosis and treatment of advanced-stage HCC remain a major challenge. RNF8, an E3 ligase important for the DNA damage response, has been proven to facilitate the progression of breast and lung cancer, but its role in HCC remains unclear. In this study, we find that the expression of RNF8 is up-regulated in HCC tissues and positively correlated with poor prognosis of HCC. Furthermore, silencing RNF8 by siRNAs attenuates the migration of HCC cells and inhibits epithelial-mesenchymal transition (EMT) by regulating the expressions of proteins including N-cadherin, β-catenin, snail, and ZO-1. Moreover, Kaplan‒Meier survival analysis shows that high RNF8 expression predicts poor survival benefits from sorafenib. Finally, cell viability assay demonstrates that RNF8 depletion enhances the sensitivity of HCC cells to sorafenib and lenvatinib treatment. We hypothesize that the inhibitory role of RNF8 in EMT and its enhancing effects on anti-cancer drugs orchestrate the protective effects of RNF8 deficiency in HCC, which indicates its potential in clinical application.

ZNF750: A Novel Prognostic Biomarker in Metastatic Prostate Cancer

Prostate cancer is the most frequently diagnosed cancer and the fifth leading cause of cancer death among men in 2020. The clinical decision making for prostate cancer patients is based on the stratification of the patients according to both clinical and pathological parameters such as Gleason score and prostate-specific antigen levels. However, these tools still do not adequately predict patient outcome. The aim of this study was to investigate whether ZNF750 could have a role in better stratifying patients, identifying those with a higher risk of metastasis and with the poorest prognosis. The data reported here revealed that ZNF750 protein levels are reduced in human prostate cancer samples, and this reduction is even higher in metastatic samples. Interestingly, nuclear positivity is significantly reduced in patients with metastatic prostate cancer, regardless of both Gleason score and grade group. More importantly, the bioinformatics analysis indicates that ZNF750 expression is positively correlated with better prognosis. Overall, our findings suggest that nuclear expression of ZNF750 may be a reliable prognostic biomarker for metastatic prostate cancer, which lays the foundation for the development of new biological therapies.

Alpha-actnin-4 (ACTN4) selectively affects the DNA double-strand breaks repair in non-small lung carcinoma cells

BACKGROUND

ACTN4 is an actin-binding protein involved in many cellular processes, including cancer development. High ACTN4 expression is often associated with a poor prognosis. However, it has been identified as a positive marker for platinum-based adjuvant chemotherapy for non-small cell lung cancer (NSCLC). The goal of our study was to investigate the involvement of ACTN4 in the NSCLC cells' response to the genotoxic drugs.

RESULTS

We generated H1299 cells with the ACTN4 gene knock-out (ACTN4 KO), using the CRISPR/Cas9 system. The resistance of the cells to the cisplatin and etoposide was analyzed with the MTT assay. We were also able to estimate the efficiency of DNA repair through the DNA comet assay and gamma-H2AX staining. Possible ACTN4 effects on the non-homologous end joining (NHEJ) and homologous recombination (HR) were investigated using pathway-specific reporter plasmids and through the immunostaining of the key proteins. We found that the H1299 cells with the ACTN4 gene knock-out did not show cisplatin-resistance, but did display a higher resistance to the topoisomerase II inhibitors etoposide and doxorubicin, suggesting that ACTN4 might be somehow involved in the repair of DNA strand breaks. Indeed, the H1299 ACTN4 KO cells repaired etoposide- and doxorubicin-induced DNA breaks more effectively than the control cells. Moreover, the ACTN4 gene knock-out enhanced NHEJ and suppressed HR efficiency. Supporting the data, the depletion of ACTN4 resulted in the faster assembly of the 53BP1 foci with a lower number of the phospho-BRCA1 foci after the etoposide treatment.

CONCLUSIONS

Thus, we are the first to demonstrate that ACTN4 may influence the resistance of cancer cells to the topoisomerase II inhibitors, and affect the efficiency of the DNA double strand breaks repair. We hypothesize that ACTN4 interferes with the assembly of the NHEJ and HR complexes, and hence regulates balance between these DNA repair pathways.