RNF138 confers cisplatin resistance in gastric cancer cells via activating Chk1 signaling pathway

An innovative prognostic auxiliary for colon adenocarcinoma based on zinc finger protein genes

Background

The carcinogenesis and progression of colon adenocarcinoma (COAD) are intensively related to the abnormal expression of the zinc finger (ZNF) protein genes. We aimed to employ these genes to provide a reliable prognosis and treatment stratification tool for COAD patients.

Methods

Cox and the least absolute shrinkage and selection operator (LASSO) regression analysis were applied, utilizing The Cancer Genome Atlas (TCGA) metadata, to build a ZNF protein gene-based prognostic model. Using this model, patients in the training cohort and testing cohort (GSE17537) were labelled as either high or low risk. Kaplan-Meier (KM) survival analysis and time-dependent receiver operating characteristic (ROC) curve analysis were performed in the patients with opposite risk status to assess the predictive ability in each cohort. The potentiality of the mechanism was explored by the estimation of stromal and immune cells in malignant tumor tissues using expression data (ESTIMATE), single-sample gene set enrichment analysis (ssGSEA), gene set enrichment analysis (GSEA), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG). Finally, the degrees of expression of model genes were validated by immunohistochemistry (IHC).

Results

The prognostic model consisting of INSM1, PHF21B, RNF138, SYTL4, WRNIP1, ZNF585B, and ZNF514, classified patients into opposite risk statuses. Patients in the high-risk subset had a considerably lower chance of surviving compared to those in the low-risk subset. There is a high probability that these model genes were attached to immune-related biological processes, which can be confirmed by the results of the above mechanistic methods. Moreover, patients in the low-risk subset also significantly outperformed the patients in the high-risk subset when calculating immune cells and function scores. Drug sensitivity and tumor immune dysfunction and exclusion (TIDE) analyses showed a clear difference in the immunological and chemotherapeutic efficacy predictions within the two risk groups. Additionally, the degrees of expression of model genes in high-risk and low-risk subsets presented great discrepancies.

Conclusions

The signature may be applied as a predictive classifier to shepherd special medication for COAD patients.

The role of RNF138 in DNA end resection is regulated by ubiquitylation and CDK phosphorylation

Double-strand breaks (DSBs) are DNA lesions that pose a significant threat to genomic stability. The repair of DSBs by the homologous recombination (HR) pathway is preceded by DNA end resection, the 5' to 3' nucleolytic degradation of DNA away from the DSB. We and others previously identified a role for RNF138, a really interesting new gene finger E3 ubiquitin ligase, in stimulating DNA end resection and HR. Yet, little is known about how RNF138's function is regulated in the context of DSB repair. Here, we show that RNF138 is phosphorylated at residue T27 by cyclin-dependent kinase (CDK) activity during the S and G2 phases of the cell cycle. We also observe that RNF138 is ubiquitylated constitutively, with ubiquitylation occurring in part on residue K158 and rising during the S/G2 phases. Interestingly, RNF138 ubiquitylation decreases upon genotoxic stress. By mutating RNF138 at residues T27, K158, and the previously identified S124 ataxia telangiectasia mutated phosphorylation site (Han et al., 2016, ref. 22), we find that post-translational modifications at all three positions mediate DSB repair. Cells expressing the T27A, K158R, and S124A variants of RNF138 are impaired in DNA end resection, HR activity, and are more sensitive to ionizing radiation compared to those expressing wildtype RNF138. Our findings shed more light on how RNF138 activity is controlled by the cell during HR.

E3 ubiquitin-ligase RNF138 may regulate p53 protein expression to regulate the self-renewal and tumorigenicity of glioma stem cells

BACKGROUND

Glioblastoma multiforme (GBM), the most malignant tumor of the central nervous system, is characterized by poor survival and high recurrence. Glioma stem cells (GSCs) are key to treating GBM and are regulated by various signaling pathways. Ubiquitination, a post-translational modification, plays an important regulatory role in many biological processes. Ring finger protein 138 (RNF138) is an E3 ubiquitin-protein ligase that is highly expressed in several tumors; however, its role in GBM is unclear. This study investigated whether RNF138 regulates the self-renewal ability of glioma stem GSCs to treat GBM.

MATERIALS AND METHODS

The expression of RNF138 in glioma tissues and its correlation with GSCs were analyzed using bioinformatics. Short hairpin ribonucleic acid (RNA) was designed to downregulate the expression of RNF138 in GSCs, and immunofluorescence, secondary pellet formation, and western blotting were used to detect changes in GSC markers and self-renewal ability. The effects of RNF138 on p53 protein expression were determined by immunofluorescence and western blotting. The effects of RNF138 on the self-renewal and tumorigenic abilities of GSCs were evaluated in vivo.

RESULTS

RNF138 expression was higher in glioma tissues than in normal brain tissues, and was highly expressed in GSCs. RNF138 downregulation significantly decreased the expression of the GSC markers cluster of differentiation 133 (CD133) and nestin. Mechanistically, RNF138 may interfere with the self-renewal ability of GSCs by regulating the expression of p53. RNF138 downregulation in vivo prolonged survival time and regulated the expression of p53 protein in tumor-bearing mice.

CONCLUSION

RNF138 may regulate the expression of p53 protein through ubiquitination, thereby affecting the self-renewal and tumorigenic ability of GSCs. This study provides a scientific basis for the treatment of glioblastoma by targeting RNF138 to inhibit GSCs.

RNF138 Downregulates Antiviral Innate Immunity by Inhibiting IRF3 Activation

A viral infection activates the transcription factors IRF3 and NF-κB, which synergistically induces type I interferons (IFNs). Here, we identify the E3 ubiquitin ligase RNF138 as an important negative regulator of virus-triggered IRF3 activation and IFN-β induction. The overexpression of RNF138 inhibited the virus-induced activation of IRF3 and the transcription of the IFNB1 gene, whereas the knockout of RNF138 promoted the virus-induced activation of IRF3 and transcription of the IFNB1 gene. We further found that RNF138 promotes the ubiquitination of PTEN and subsequently inhibits PTEN interactions with IRF3, which is essential for the PTEN-mediated nuclear translocation of IRF3, thereby inhibiting IRF3 import into the nucleus. Our findings suggest that RNF138 negatively regulates virus-triggered signaling by inhibiting the interaction of PTEN with IRF3, and these data provide new insights into the molecular mechanisms of cellular antiviral responses.

Mechanism of cisplatin resistance in gastric cancer and associated microRNAs

Gastric cancer (GC) is a common malignant tumor with high morbidity and mortality rates that seriously affects human health worldwide. Although surgery is currently the preferred clinical treatment for GC, chemotherapy remains the first choice for perioperative treatment, adjuvant therapy, and palliative care for patients with advanced GC. Cisplatin (DDP) is an antineoplastic agent that has been used clinically for decades, and it is the first-line chemotherapy for many solid tumors. However, the therapeutic efficacy of DDP is often limited by resistance and the complexity of its resistance mechanisms, which involve multiple proteins and signaling pathways. It is well documented that a variety of microRNAs (miRNAs) differentially expressed in DDP-resistant GC cells play important roles in regulating or reversing DDP resistance via various pathways. In this review, we first provide an introduction to the cytotoxicity and major resistance mechanisms of DDP in GC and then discuss the role and mechanism of miRNAs in regulating the DDP resistance process in GC cells. This work demonstrates the potential of relevant miRNAs to become diagnostic and prognostic biomarkers for gastric cancer and targets of action to enhance chemosensitivity and provides directions for future research.

A state-of-art of underlying molecular mechanisms and pharmacological interventions/nanotherapeutics for cisplatin resistance in gastric cancer

The fourth common reason of death among patients is gastric cancer (GC) and it is a dominant tumor type in Ease Asia. One of the problems in GC therapy is chemoresistance. Cisplatin (CP) is a platinum compound that causes DNA damage in reducing tumor progression and viability of cancer cells. However, due to hyperactivation of drug efflux pumps, dysregulation of genes and interactions in tumor microenvironment, tumor cells can develop resistance to CP chemotherapy. The current review focuses on the CP resistance emergence in GC cells with emphasizing on molecular pathways, pharmacological compounds for reversing chemoresistance and the role of nanostructures. Changes in cell death mechanisms such as upregulation of pro-survival autophagy can prevent CP-mediated apoptosis that results in drug resistance. Moreover, increase in metastasis via EMT induction induces CP resistance. Dysregulation of molecular pathways such as PTEN, PI3K/Akt, Nrf2 and others result in changes in CP response of GC cells. Non-coding RNAs determine CP response of GC cells and application of pharmacological compounds with activity distinct of CP can result in sensitivity in tumor cells. Due to efficacy of exosomes in transferring bioactive molecules such as RNA and DNA molecules among GC cells, exosomes can also result in CP resistance. One of the newest progresses in overcoming CP resistance in GC is application of nanoplatforms for delivery of CP in GC therapy that they can increase accumulation of CP at tumor site and by suppressing carcinogenic factors and overcoming biological barriers, they increase CP toxicity on cancer cells.

Fibroblast growth factor signalling influences homologous recombination-mediated DNA damage repair to promote drug resistance in ovarian cancer

BACKGROUND

Ovarian cancer patients frequently develop chemotherapy resistance, limiting treatment options. We have previously shown that individuality in fibroblast growth factor 1 (FGF1) expression influences survival and chemotherapy response.

METHODS

We used MTT assays to assess chemosensitivity to cisplatin and carboplatin following shRNA-mediated knockdown or heterologous over-expression of FGF1 (quantified by qRT-PCR and immunoblot analysis), and in combination with the FGFR inhibitors AZD4547 and SU5402, the ATM inhibitor KU55933 and DNA-PK inhibitor NU7026. Immunofluorescence microscopy was used to quantify the FGF1-dependent timecourse of replication protein A (RPA) and γH2AX foci formation.

RESULTS

Pharmacological inhibition of FGF signalling reversed drug resistance in immortalised cell lines and in primary cell lines from drug-resistant ovarian cancer patients, while FGF1 over-expression induced resistance. Ataxia telangiectasia mutated (ATM) phosphorylation, but not DNA adduct formation was FGF1 dependent, following cisplatin or carboplatin challenge. Combining platinum drugs with the ATM inhibitor KU55933, but not with the DNA-PK inhibitor NU7026 re-sensitised resistant cells. FGF1 expression influenced the timecourse of damage-induced RPA and γH2AX nuclear foci formation.

CONCLUSION

Drug resistance arises from FGF1-mediated differential activation of high-fidelity homologous recombination DNA damage repair. FGFR and ATM inhibitors reverse platinum drug resistance, highlighting novel combination chemotherapy approaches for future clinical trial evaluation.

RING finger 138 deregulation distorts NF-кB signaling and facilities colitis switch to aggressive malignancy

Prolonged activation of nuclear factor (NF)-кB signaling significantly contributes to the development of colorectal cancer (CRC). New therapeutic opportunities are emerging from targeting this distorted cell signaling transduction. Here, we discovered the critical role of RING finger 138 (RNF138) in CRC tumorigenesis through regulating the NF-кB signaling, which is independent of its Ubiquitin-E3 ligase activity involved in DNA damage response. RNF138^−/− mice were hyper-susceptible to the switch from colitis to aggressive malignancy, which coincided with sustained aberrant NF-кB signaling in the colonic cells. Furthermore, RNF138 suppresses the activation of NF-кB signaling pathway through preventing the translocation of NIK and IKK-Beta Binding Protein (NIBP) to the cytoplasm, which requires the ubiquitin interaction motif (UIM) domain. More importantly, we uncovered a significant correlation between poor prognosis and the downregulation of RNF138 associated with reinforced NF-кB signaling in clinical settings, raising the possibility of RNF138 dysregulation as an indicator for the therapeutic intervention targeting NF-кB signaling. Using the xenograft models built upon either RNF138-dificient CRC cells or the cells derived from the RNF138-dysregulated CRC patients, we demonstrated that the inhibition of NF-кB signaling effectively hampered tumor growth. Overall, our work defined the pathogenic role of aberrant NF-кB signaling due to RNF138 downregulation in the cascade events from the colitis switch to colonic neoplastic transformation and progression, and also highlights the possibility of targeting the NF-кB signaling in treating specific subtypes of CRC indicated by RNF138-ablation.

SIAH1 reverses chemoresistance in epithelial ovarian cancer via ubiquitination of YBX-1

Chemoresistance is a severe outcome among patients with epithelial ovarian cancer (EOC) that leads to a poor prognosis. YBX-1 has been shown to cause treatment failure and cancer progression in EOC. However, strategies that directly target YBX-1 are not yet conceivable. Here, we identified that SIAH1 which was downregulated in chemoresistant EOC samples and cell lines functioned as novel E3 ligases to trigger degradation of YBX-1 at cytoplasm by RING finger domain. Mechanistic studies show that YBX-1 was ubiquitinated by SIAH1 at lys304 that lead to the instability of its target m5C-modified mRNAs, thus sensitized EOC cells to cDDP. Overexpression of SIAH1 enhanced the antitumor efficacy of cisplatin in vitro and in vivo, which were partially impaired by ectopic expression of YBX-1 or depletion of YBX-1 ubiquitination. In summary, our data identify the SIAH1/YBX-1 interaction as a therapeutic target for overcoming EOC chemoresistance.

Glaucocalyxin A suppresses multiple myeloma progression in vitro and in vivo through inhibiting the activation of STAT3 signaling pathway

Background

Multiple myeloma (MM) is the most common malignant hematological disease in the people worldwide. Glaucocalyxin A (GLA) is a bioactive ent-kauranoid diterpenoid, that is derived from Rabdosia japonica var. GLA has been demonstrated that it had various pharmacological activities, such as anti-coagulation, anti-bacterial, anti-tumor, anti-inflammation, antioxidant activities. Although GLA has effective anti-tumor properties, its effects on multiple myeloma remain unclear. The aim of this study was to examine the possible anti-cancer effects of GLA and their molecular mechanisms on MM cells in vitro and in vivo.

Methods

To evaluate the role of GLA on the proliferation of MM cells in vitro and in vivo, we used MTT method to detect the role of GLA on the proliferation of MM cells. Cell apoptosis and cell cycle assay were evaluated by flow cytometry. Protein expressions in GLA-treated and untreated MM cells were evaluated by western blot analyses. MM xenograft nude mice model was used to investigate the role of GLA on the proliferation of MM cells in vivo. IHC assay was used to examine the role of GLA on the MM xenograft model in vivo.

Results

In the present study, we firstly reported the potent anti-myeloma activity of GLA on MM cells. We found that GLA could induce apoptosis in vitro and in vivo. GLA could inhibit the phosphorylation of the signal transducer and activator of transcription 3 (STAT3) and downregulate interleukin IL-6 induced STAT3 phosphorylation in MM. Overexpression of STAT3 could significantly prevent apoptosis induced by GLA; while knockdown of STAT3 enhanced it. Moreover, GLA could inhibit cell proliferation by inducing the cell cycle arrest. GLA reduced the expression of cell cycle-related proteins CCNB1, CCND1, CCND2, and CCND3 and increased the expression of p21 in MM cell lines. In addition, in the MM xenograft nude mice model, GLA exhibited very good anti-myeloma activity. Administration of GLA almost completely inhibited tumor growth within 19 days without physical toxicity. And the IHC results showed GLA significantly inhibited cell proliferation and interfered STAT3 pathway on MM xenograft model tumor tissues.

Conclusions

Taken together, our present research indicated that GLA inhibits the MM cell proliferation, induces MM cell apoptosis and cell cycle arrest through blocking the activation of STAT3 pathway. Thus, GLA may be a potential therapeutic candidate for MM patients in the future.

LncRNA HLA Complex Group 11 Knockdown Alleviates Cisplatin Resistance in Gastric Cancer by Targeting the miR-144-3p/UBE2D1 Axis

OBJECTIVE

Cisplatin (DDP) treatment is one of the most predominant chemotherapeutic strategies for patients with gastric cancer (GC). LncRNA noncoding RNA HLA complex group 11 (lncRNA HCG11) has been confirmed to promote GC progression. This study attempted to investigate the underlying molecular mechanism of HCG11 in DDP resistance of GC.

METHODS

qRT-PCR was performed to evaluate the expression of HCG11, microRNA-144-3p (miR-144-3p), and ubiquitin-conjugating enzyme E2 D1 (UBE2D1) in GC. The correlation between HCG11 and clinicopathological features of GC patients was assessed. DDP-resistant GC cells and their parental cells were cultured in different concentrations of DDP. The role of HCG11 for the viability and the half maximal inhibitory concentration (IC50) of DDP in DDP-resistant GC cells was determined by MTT assay. Then, the invasion of DDP-resistant GC cells was measured by transwell assay. Next, a dual-luciferase reporter assay was used to confirm the interactions among HCG11, miR-144-3p, and UBE2D1 in GC.

RESULTS

The expression of HCG11 and UBE2D1 was elevated in tumor tissues of GC patients, but miR-144-3p was declined. HCG11 expression was elevated in DDP-resistant GC patients and is strongly correlated with DDP sensitivity and World Health Organization grade in GC patients. HCG11 knockdown reduced the viability, IC50 of DDP, and invasion of DDP-resistant GC cells. Additionally, HCG11 targeted miR-144-3p and miR-144-3p further targeted UBE2D1. Feedback experiments indicated that low expression of miR-144-3p or overexpression of UBE2D1 mitigated the inhibitory effect of HCG11 depletion on DDP resistance of GC cells.

CONCLUSION

HCG11 knockdown attenuated DDP resistance of GC cells through via miR-144-3p/UBE2D1 axis, affording a novel therapeutic strategy for GC.

Silencing microRNA‑29b‑3p expression protects human trabecular meshwork cells against oxidative injury via upregulation of RNF138 to activate the ERK pathway

In recent years, the potential involvement of numerous microRNAs (miRNAs) in glaucoma has been widely reported. However, the role of microRNA-29b-3p (miR-29b-3p) in the pathogenesis of glaucoma remains unknown. This study aimed to explore the biological role and regulatory mechanism of miR-29b-3p in the oxidative injury of human trabecular meshwork (HTM) cells induced by H₂O₂ stimulation. By establishing a glaucoma rat model, the effects of miR-29-3p in glaucoma were detected in vivo. Our findings demonstrated that miR-29b-3p was upregulated in a glaucoma model and antagomiR-29b-3p alleviated the symptoms of glaucoma. In vitro assays revealed that miR-29b-3p expression was significantly upregulated in HTM cells with H₂O₂ stimulation. Knockdown of miR-29b-3p alleviated H₂O₂-induced oxidative injury in HTM cells by promoting cell viability, and inhibiting cell apoptosis, reactive oxygen species generation and extracellular matrix production. Subsequently, it was found that E3 ubiquitin-protein ligase RNF138 (RNF138) was a downstream target of miR-29b-3p. RNF138 expression was downregulated in HTM cells with H₂O₂ stimulation. RNF138 knockdown significantly rescued the protective effect of miR-29b-3p inhibitor on HTM cells under oxidative injury. Additionally, miR-29b-3p silencing activated the ERK pathway via upregulating RNF138. Collectively, silencing of miR-29b-3p protected HTM cells against oxidative injury by upregulation of RNF138 to activate the ERK pathway.

E3 Ubiquitin Ligase in Anticancer Drugdsla Resistance: Recent Advances and Future Potential

Drug therapy is the primary treatment for patients with advanced cancer. The use of anticancer drugs will inevitably lead to drug resistance, which manifests as tumor recurrence. Overcoming chemoresistance may enable cancer patients to have better therapeutic effects. However, the mechanisms underlying drug resistance are poorly understood. E3 ubiquitin ligases (E3s) are a large class of proteins, and there are over 800 putative functional E3s. E3s play a crucial role in substrate recognition and catalyze the final step of ubiquitin transfer to specific substrate proteins. The diversity of the set of substrates contributes to the diverse functions of E3s, indicating that E3s could be desirable drug targets. The E3s MDM2, FBWX7, and SKP2 have been well studied and have shown a relationship with drug resistance. Strategies targeting E3s to combat drug resistance include interfering with their activators, degrading the E3s themselves and influencing the interaction between E3s and their substrates. Research on E3s has led to the discovery of possible therapeutic methods to overcome the challenging clinical situation imposed by drug resistance. In this article, we summarize the role of E3s in cancer drug resistance from the perspective of drug class.

Roles of E3 ubiquitin ligases in gastric cancer carcinogenesis and their effects on cisplatin resistance

Although gastric cancer (GC) is one of the most common cancers with high incidence and mortality rates, its pathogenesis is still not elucidated. GC carcinogenesis is complicated and involved in the activation of oncoproteins and inactivation of tumor suppressors. The ubiquitin-proteasome system (UPS) is crucial for protein degradation and regulation of physiological and pathological processes. E3 ubiquitin ligases are pivotal enzymes in UPS, containing various subfamily proteins. Previous studies report that some E3 ligases, including SKP2, CUL1, and MDM2, act as oncoproteins in GC carcinogenesis. On the other hand, FBXW7, FBXL5, FBXO31, RNF43, and RNF180 exert as tumor suppressors in GC carcinogenesis. Moreover, E3 ligases modulate cell growth, cell apoptosis, and cell cycle; thus, it is complicated to confer cisplatin resistance/sensitivity in GC cells. The intrinsic and acquired cisplatin resistance limits its clinical application against GC. In this review, we explore oncogenic and tumor suppressive roles of E3 ligases in GC carcinogenesis and focus on the effects of E3 ligases on cisplatin resistance in GC cells, which will provide novel therapeutic targets for GC therapy, especially for cisplatin-resistant patients.

RING finger protein 38 induces the drug resistance of cisplatin in non-small-cell lung cancer

Cisplatin resistance of non-small-cell lung cancer (NSCLC) needs to be well elucidated. RING finger protein (RNF38) has been proposed as a biomarker of NSCLC poor prognosis. However, its role in drug resistance in NSCLC is poorly understood. RNF38 expression was detected in normal lung epithelial cell and four NSCLC cell lines. RNF38 was stably overexpressed in A549 and H460 cells or silenced in H1975 and cisplatin-resistant A549 cells (A549-CDDP resistant) using lentiviral vectors. RNF38 expression levels were determined using quantitative real-time polymerase chain reaction and western blotting analysis. Cell viability in response to different concentrations of cisplatin was evaluated by Cell Counting Kit-8 assay. RNF38 expression levels were markedly elevated in NSCLC cells and cells harboring high RNF38 were less sensitive to cisplatin. Overexpression of RNF38 reduced, while RNF38 silencing increased the drug sensitivity of cisplatin in NSCLC cells. Cisplatin-resistant cells expressed high RNF38 level. RNF38 silencing promoted cell apoptosis and enhanced the drug sensitivity of cisplatin in cisplatin-resistant NSCLC cells. These findings indicate that RNF38 might induce cisplatin resistance of NSCLC cells via promoting cell apoptosis and RNF38 could be a novel target for rectify cisplatin resistance in NSCLC cases.

A Gene-Expression Predictor for Efficacy of Induction Chemotherapy in Locoregionally Advanced Nasopharyngeal Carcinoma

BACKGROUND

Induction chemotherapy (IC) followed by concurrent chemoradiotherapy is the mainstay treatment for patients with locoregionally advanced nasopharyngeal carcinoma. However, some patients obtain little benefit and experience unnecessary toxicities from IC. We intended to develop a gene-expression signature that can identify beneficiaries of IC.

METHODS

We screened chemosensitivity-related genes by comparing gene-expression profiles of patients with short-term tumor response or nonresponse to IC (n = 95) using microarray analysis. Chemosensitivity-related genes were quantified by digital expression profiling in a training cohort (n = 342) to obtain a gene signature. We then validated this gene signature in the clinical trial cohort (n = 187) and an external independent cohort (n = 240). Tests of statistical significance are 2-sided.

RESULTS

We identified 43 chemosensitivity-related genes associated with the short-term tumor response to IC. In the training cohort, a 6-gene signature was developed that was highly accurate at predicting the short-term tumor response to IC (area under the curve [AUC] = 0.87, sensitivity = 87.5%, specificity = 75.6%). We further found that IC conferred failure-free survival benefits only in patients in the benefit group (hazard ratio [HR] = 0.54, 95% confidence interval [CI] = 0.34 to 0.87; P = .01) and not on those in the no-benefit group (HR = 1.25, 95% CI = 0.62 to 2.51; P = .53). In the clinical trial cohort, the 6-gene signature was also highly accurate at predicting the tumor response (AUC = 0.82, sensitivity = 87.5%, specificity = 71.8%) and indicated failure-free survival benefits. In the external independent cohort, similar results were observed.

CONCLUSIONS

The 6-gene signature can help select beneficiaries of IC and lay a foundation for a more individualized therapeutic strategy for locoregionally advanced nasopharyngeal carcinoma patients.