RNF8 promotes epithelial-mesenchymal transition of breast cancer cells

PI3K/AKT pathway as a pivotal regulator of epithelial-mesenchymal transition in lung tumor cells

Lung cancer, as the leading cause of cancer related deaths, is one of the main global health challenges. Despite various progresses in diagnostic and therapeutic methods, there is still a high rate of mortality among lung cancer patients, which can be related to the lack of clinical symptoms to differentiate lung cancer from the other chronic respiratory disorders in the early tumor stages. Most lung cancer patients are identified in advanced and metastatic tumor stages, which is associated with a poor prognosis. Therefore, it is necessary to investigate the molecular mechanisms involved in lung tumor progression and metastasis in order to introduce early diagnostic markers as well as therapeutic targets. Epithelial-mesenchymal transition (EMT) is considered as one of the main cellular mechanisms involved in lung tumor metastasis, during which tumor cells gain the metastatic ability by acquiring mesenchymal characteristics. Since, majority of the oncogenic signaling pathways exert their role in tumor cell invasion by inducing the EMT process, in the present review we discussed the role of PI3K/AKT signaling pathway in regulation of EMT process during lung tumor metastasis. It has been reported that the PI3K/AKT acts as an inducer of EMT process through the activation of EMT-specific transcription factors in lung tumor cells. MicroRNAs also exerted their inhibitory effects during EMT process by inhibition of PI3K/AKT pathway. This review can be an effective step towards introducing the PI3K/AKT pathway as a suitable therapeutic target to inhibit the EMT process and tumor metastasis in lung cancer patients.

SiRNF8 Delivered by DNA Framework Nucleic Acid Effectively Sensitizes Chemotherapy in Colon Cancer

Background

The evident side effects and decreased drug sensitivity significantly restrict the use of chemotherapy. However, nanoparticles based on biomaterials are anticipated to address this challenge.

Methods

Through bioinformatics analysis and colon cancer samples, we initially investigated the expression level of RNF8 in colon cancer. Next, we constructed nanocarrier for delivering siRNF8 based on DNA tetrahedron (si-Tet), and Doxorubicin (DOX) was further intercalated into the DNA structure (si-DOX-Tet) for combination therapy. Further, the effects and mechanism of RNF8 inhibition on the sensitivity of colon cancer cells to DOX chemotherapy have also been studied.

Results

RNF8 expression was increased in colon cancer. Agarose gel electrophoresis, transmission electron microscopy, and size distribution and potential analysis confirmed the successful preparation of the two nanoparticles, with particle sizes of 10.29 and 37.29 nm, respectively. Fluorescence imaging reveals that the carriers can be internalized into colon cancer cells and escape from lysosomes after 12 hours of treatment, effectively delivering siRNF8 and DOX. Importantly, Western blot analysis verified treatment with 50nM si-Tet silenced RNF8 expression by approximately 50% in colon cancer cells, and combined treatment significantly inhibited cell proliferation. Furthermore, the CCK-8 assay demonstrated that si-Tet treatment enhanced the sensitivity of colon cancer cells to the three chemotherapeutic drugs. Significant more DNA damage was detected after treatment with both si-Tet or si-DOX-Tet. Further flow cytometry analysis revealed that si-DOX-Tet treatment led to significantly more apoptosis, approximately 1.6-fold higher than treatment with DOX alone. Mechanistically, inhibiting RNF8 led to decreased ABCG2 expression and DOX efflux, but increased DNA damage, thereby enhancing the chemotherapeutic effect of DOX.

Conclusion

We have successfully constructed si-DOX-Tet. By inhibiting the expression of RNF8, it enhances the chemotherapy sensitivity of DOX. Therefore, this tetrahedral FNA nanocarrier offers a new approach for the combined treatment of colon cancer.

Mutual regulation of TGFβ-induced oncogenic EMT, cell cycle progression and the DDR

TGFβ signaling and the DNA damage response (DDR) are two cellular toolboxes with a strong impact on cancer biology. While TGFβ as a pleiotropic cytokine affects essentially all hallmarks of cancer, the multifunctional DDR mostly orchestrates cell cycle progression, DNA repair, chromatin remodeling and cell death. One oncogenic effect of TGFβ is the partial activation of epithelial-to-mesenchymal transition (EMT), conferring invasiveness, cellular plasticity and resistance to various noxae. Several reports show that both individual networks as well as their interface affect chemo-/radiotherapies. However, the underlying mechanisms remain poorly resolved. EMT often correlates with TGFβ-induced slowing of proliferation, yet numerous studies demonstrate that particularly the co-activated EMT transcription factors counteract anti-proliferative signaling in a partially non-redundant manner. Collectively, evidence piled up over decades underscore a multifaceted, reciprocal inter-connection of TGFβ signaling / EMT with the DDR / cell cycle progression, which we will discuss here. Altogether, we conclude that full cell cycle arrest is barely compatible with the propagation of oncogenic EMT traits and further propose that 'EMT-linked DDR plasticity' is a crucial, yet intricate facet of malignancy, decisively affecting metastasis formation and therapy resistance.

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 enhances the sensitivity of PD-L1 inhibitor against melanoma through ubiquitination of galectin-3 in stroma

The failure of melanoma immunotherapy can be mediated by immunosuppression in the tumor microenvironment (TME), and insufficient activation of effector T cells against the tumor. Here, we show that inhibition of galectin-3 (gal-3) enhances the infiltration of T cells in TME and improves the sensitivity of anti-PD-L1 therapy. We identify that RNF8 downregulated the expression of gal-3 by K48-polyubiquitination and promoted gal-3 degradation via the ubiquitin-proteasome system. RNF8 deficiency in the host but sufficiency in implanted melanoma results in immune exclusion and tumor progression due to the upregulation of gal-3. Upregulation of gal-3 decreased the immune cell infiltration by restricting IL-12 and IFN-γ. Inhibition of gal-3 reverses immunosuppression and induces immune cell infiltration in the tumor microenvironment. Moreover, gal-3 inhibitor treatment can increase the sensitivity of PD-L1 inhibitors via increasing immune cell infiltration and enhancing immune response in tumors. This study reveals a previously unrecognized immunoregulation function of RNF8 and provides a promising strategy for the therapy of "cold" tumors. Tremendous effects of melanoma treatment can be achieved by facilitating immune cell infiltration combined with anti-PD-L1 treatment.

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.

Invention of 3Mint for feature grouping and scoring in multi-omics

Advanced genomic and molecular profiling technologies accelerated the enlightenment of the regulatory mechanisms behind cancer development and progression, and the targeted therapies in patients. Along this line, intense studies with immense amounts of biological information have boosted the discovery of molecular biomarkers. Cancer is one of the leading causes of death around the world in recent years. Elucidation of genomic and epigenetic factors in Breast Cancer (BRCA) can provide a roadmap to uncover the disease mechanisms. Accordingly, unraveling the possible systematic connections between-omics data types and their contribution to BRCA tumor progression is crucial. In this study, we have developed a novel machine learning (ML) based integrative approach for multi-omics data analysis. This integrative approach combines information from gene expression (mRNA), microRNA (miRNA) and methylation data. Due to the complexity of cancer, this integrated data is expected to improve the prediction, diagnosis and treatment of disease through patterns only available from the 3-way interactions between these 3-omics datasets. In addition, the proposed method bridges the interpretation gap between the disease mechanisms that drive onset and progression. Our fundamental contribution is the 3 Multi-omics integrative tool (3Mint). This tool aims to perform grouping and scoring of groups using biological knowledge. Another major goal is improved gene selection via detection of novel groups of cross-omics biomarkers. Performance of 3Mint is assessed using different metrics. Our computational performance evaluations showed that the 3Mint classifies the BRCA molecular subtypes with lower number of genes when compared to the miRcorrNet tool which uses miRNA and mRNA gene expression profiles in terms of similar performance metrics (95% Accuracy). The incorporation of methylation data in 3Mint yields a much more focused analysis. The 3Mint tool and all other supplementary files are available at https://github.com/malikyousef/3Mint/.

A functional reference map of the RNF8 interactome in cancer

Background

RNF8 is an E3 ligase identified as a critical DNA damage-responsive protein. Recently, multiple reports have shown that RNF8 could be used as an important therapeutic target for cancer chemo/radiotherapy. However, the understanding of RNF8 remains limited due to the lack of its interactome reference map and comprehensive analysis of RNF8 in diverse cancers, which underscores the need to map the interactome of RNF8 via high-throughput methods.

Results

A two-way identification method based on LC–MS was designed for the identification of the RNF8 interactome with high-specificity. By in silico analysis and in vitro validation, we identified a new reference map of the RNF8 interactome network containing many new targets, such as YBX1, DNMT1, and HDCA1, new biological functions and the gene-disease associations of RNF8. Our results revealed a close relationship between RNF8 and neurodegenerative diseases or tumor-infiltrating immune cells using bulk RNA-seq and scRNA-seq datasets. As a proof of concept of our interactome map, we validated the direct binding between RNF8 and YBX1 and showed that RNF8 catalyzed the ubiquitination of YBX1. These results demonstrated that RNF8 might be a crucial regulator of YBX1.

Conclusions

Our work provides a unique framework for researchers and clinicians who seek to better explore or understand RNF8-regulated biological functions in cancers. This study will hopefully facilitate the rational design and further development of anti-RNF8 therapy in cancers.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13062-022-00331-z.

Comprehensive Analysis of hsa-miR-654-5p's Tumor-Suppressing Functions

The pivotal roles of miRNAs in carcinogenesis, metastasis, and prognosis have been demonstrated recently in various cancers. This study intended to investigate the specific roles of hsa-miR-654-5p in lung cancer, which is, in general, rarely discussed. A series of closed-loop bioinformatic functional analyses were integrated with in vitro experimental validation to explore the overall biological functions and pan-cancer regulation pattern of miR-654-5p. We found that miR-654-5p abundance was significantly elevated in LUAD tissues and correlated with patients’ survival. A total of 275 potential targets of miR-654-5p were then identified and the miR-654-5p-RNF8 regulation axis was validated in vitro as a proof of concept. Furthermore, we revealed the tumor-suppressing roles of miR-654-5p and demonstrated that miR-654-5p inhibited the lung cancer cell epithelial-mesenchymal transition (EMT) process, cell proliferation, and migration using target-based, abundance-based, and ssGSEA-based bioinformatic methods and in vitro validation. Following the construction of a protein–protein interaction network, 11 highly interconnected hub genes were identified and a five-genes risk scoring model was developed to assess their potential prognostic ability. Our study does not only provide a basic miRNA-mRNA-phenotypes reference map for understanding the function of miR-654-5p in different cancers but also reveals the tumor-suppressing roles and prognostic values of miR-654-5p.

Neuroprotective Effect of E3 Ubiquitin Ligase RNF8 Against Ischemic Stroke via HDAC2 Stability Reduction and Reelin-Dependent GSK3β Inhibition

Loss of E3 ubiquitin ligase RING finger protein 8 (RNF8) may lead to neuronal DNA damage and apoptosis. In order to expand on our knowledge on the mechanistic basis underlying neuronal death in ischemic stroke, the present study sought to investigate the potential role of E3 ubiquitin ligase RNF8 on ischemic stroke and explore the underlying downstream mechanism. Middle cerebral artery occlusion (MCAO) in mice and oxygen–glucose deprivation/reoxygenation (OGD/R) in neurons were induced to simulate an ischemic stroke environment. It was found that downregulation of RNF8 and Reelin occurred in MCAO mice and OGD/R-exposed neurons. Silencing of RNF8 enhanced the MCAO-induced neuronal apoptosis and oxidative stress. Mechanistically, RNF8 enhanced the ubiquitination and degradation of HDAC2, thus attenuating OGD/R-induced neuronal apoptosis and oxidative stress. Moreover, HDAC2 inhibited Reelin expression through deacetylation of H3K27me3 in its promoter, causing reduced glycogen synthase kinase-3beta (GSK3β)-Ser9 phosphorylation and the resultant elevated GSK3β activity. By this mechanism, RNF8 alleviated ischemic stroke. Coherently, this study suggests that RNF8 plays a neuroprotective effect against ischemic stroke by downregulating HDAC2 expression and inducing Reelin-induced GSK3β inhibition.

Ginsenoside Rh4 Suppresses Metastasis of Gastric Cancer via SIX1-Dependent TGF-β/Smad2/3 Signaling Pathway

Gastric cancer (GC) is the leading causes of cancer-related death worldwide. Surgery remains the cornerstone of gastric cancer treatment, and new strategies with adjuvant chemotherapy are currently gaining more and more acceptance. Ginsenoside Rh4 has excellent antitumor activity. Conversely, the mechanisms involved in treatment of GC are not completely understood. In this study, we certified that Rh4 showed strong anti-GC efficiency in vitro and in vivo. MTT and colony formation assays were performed to exhibit that Rh4 significantly inhibited cellular proliferation and colony formation. Results from the wound healing assay, transwell assays, and Western blotting indicated that Rh4 restrained GC cell migration and invasion by reversing epithelial–mesenchymal transition (EMT). Further validation by proteomic screening, co-treatment with disitertide, and SIX1 signal silencing revealed that SIX1, a target of Rh4, induced EMT by activating the TGF-β/Smad2/3 signaling pathway. In summary, our discoveries demonstrated the essential basis of the anti-GC metastatic effects of Rh4 via suppressing the SIX1–TGF-β/Smad2/3 signaling axis, which delivers a new idea for the clinical treatment of GC.

RNF8 up-regulates AR/ARV7 action to contribute to advanced prostate cancer progression

Androgen receptor (AR) signaling drives prostate cancer (PC) progression. Androgen deprivation therapy (ADT) is temporally effective, whereas drug resistance inevitably develops. Abnormal expression of AR/ARV7 (the most common AR splicing variant) is critical for endocrine resistance, while the detailed mechanism is still elusive. In this study, bioinformatics and immunohistochemical analyses demonstrate that RNF8 is high expressed in PC and castration-resistant PC (CRPC) samples and the expression of RNF8 is positively correlated with the Gleason score. The high expression of RNF8 in PCs predicts a poor prognosis. These results provide a potential function of RNF8 in PC progression. Furthermore, the mRNA expression of RNF8 is positively correlated with that of AR in PC. Mechanistically, we find that RNF8 upregulates c-Myc-induced AR transcription via altering histone modifications at the c-Myc binding site within the AR gene. RNF8 also acts as a co-activator of AR, promoting the recruitment of AR/ARV7 to the KLK3 (PSA) promoter, where RNF8 modulates histone modifications. These functions of RNF8 are dependent on its E3 ligase activity. RNF8 knockdown further reduces AR transactivation and PSA expression in CRPC cells with enzalutamide treatment. RNF8 depletion restrains cell proliferation and alleviates enzalutamide resistance in CRPC cells. Our findings indicate that RNF8 may be a potential therapeutic target for endocrine resistance in PC.

Circulating Tumor Cells in Breast Cancer Patients: A Balancing Act between Stemness, EMT Features and DNA Damage Responses

Circulating tumor cells (CTCs) traverse vessels to travel from the primary tumor to distant organs where they adhere, transmigrate, and seed metastases. To cope with these challenges, CTCs have reached maximal flexibility to change their differentiation status, morphology, migratory capacity, and their responses to genotoxic stress caused by metabolic changes, hormones, the inflammatory environment, or cytostatic treatment. A significant percentage of breast cancer cells are defective in homologous recombination repair and other mechanisms that protect the integrity of the replication fork. To prevent cell death caused by broken forks, alternative, mutagenic repair, and bypass pathways are engaged but these increase genomic instability. CTCs, arising from such breast tumors, are endowed with an even larger toolbox of escape mechanisms that can be switched on and off at different stages during their journey according to the stress stimulus. Accumulating evidence suggests that DNA damage responses, DNA repair, and replication are integral parts of a regulatory network orchestrating the plasticity of stemness features and transitions between epithelial and mesenchymal states in CTCs. This review summarizes the published information on these regulatory circuits of relevance for the design of biomarkers reflecting CTC functions in real-time to monitor therapeutic responses and detect evolving chemoresistance mechanisms.

E3 Ubiquitin Ligases in Breast Cancer Metastasis: A Systematic Review of Pathogenic Functions and Clinical Implications

Female breast cancer has become the most commonly occurring cancer worldwide. Although it has a good prognosis under early diagnosis and appropriate treatment, breast cancer metastasis drastically causes mortality. The process of metastasis, which includes cell epithelial–mesenchymal transition, invasion, migration, and colonization, is a multistep cascade of molecular events directed by gene mutations and altered protein expressions. Ubiquitin modification of proteins plays a common role in most of the biological processes. E3 ubiquitin ligase, the key regulator of protein ubiquitination, determines the fate of ubiquitinated proteins. E3 ubiquitin ligases target a broad spectrum of substrates. The aberrant functions of many E3 ubiquitin ligases can affect the biological behavior of cancer cells, including breast cancer metastasis. In this review, we provide an overview of these ligases, summarize the metastatic processes in which E3s are involved, and comprehensively describe the roles of E3 ubiquitin ligases. Furthermore, we classified E3 ubiquitin ligases based on their structure and analyzed them with the survival of breast cancer patients. Finally, we consider how our knowledge can be used for E3s’ potency in the therapeutic intervention or prognostic assessment of metastatic breast cancer.

RNF8-mediated regulation of Akt promotes lung cancer cell survival and resistance to DNA damage

Despite the tremendous success of targeted and conventional therapies for lung cancer, therapeutic resistance is a common and major clinical challenge. RNF8 is a ubiquitin E3 ligase that plays essential roles in the DNA damage response; however, its role in the pathogenesis of lung cancer is unclear. Here, we report that RNF8 is overexpressed in lung cancer and positively correlates with the expression of p-Akt and poor survival of patients with non-small-cell lung cancer. In addition, we identify RNF8 as the E3 ligase for regulating the activation of Akt by K63-linked ubiquitination under physiological and genotoxic conditions, which leads to lung cancer cell proliferation and resistance to chemotherapy. Together, our study suggests that RNF8 could be a very promising target in precision medicine for lung cancer.

Resistance to Intervention: Paclitaxel in Breast Cancer

Breast cancer stands as the most prevalent cancer in women globally, and contributes to the highest percentage of mortality due to cancer-related deaths in women. Paclitaxel (PTX) is heavily relied on as a frontline chemotherapy drug in breast cancer treatment, especially in advanced metastatic cancer. Generation of resistance to PTX often derails clinical management and adversely affects patient outcomes. Understanding the molecular mechanism of PTX resistance is necessary to device methods to aid in overcoming the resistance. Recent studies exploring the mechanism of development of PTX resistance have led to unveiling of a range novel therapeutic targets. PTX resistance pathways that involve major regulatory proteins/RNAs like RNF8/Twist/ROR1, TLR, ErbB3/ErbB2, BRCA1- IRIS, MENA, LIN9, MiRNA, FoxM1 and IRAK1 have expanded the complexity of resistance mechanisms, and brought newer insights into the development of drug targets. These resistance-related targets can be dealt with synthetic/natural therapeutics in combination with PTX. The present review encompasses the recent understanding of PTX resistance mechanisms in breast cancer and possible therapeutic combinations to overcome resistance.

Autophagic Organelles in DNA Damage Response

Autophagy is an important subcellular event engaged in the maintenance of cellular homeostasis via the degradation of cargo proteins and malfunctioning organelles. In response to cellular stresses, like nutrient deprivation, infection, and DNA damaging agents, autophagy is activated to reduce the damage and restore cellular homeostasis. One of the responses to cellular stresses is the DNA damage response (DDR), the intracellular pathway that senses and repairs damaged DNA. Proper regulation of these pathways is crucial for preventing diseases. The involvement of autophagy in the repair and elimination of DNA aberrations is essential for cell survival and recovery to normal conditions, highlighting the importance of autophagy in the resolution of cell fate. In this review, we summarized the latest information about autophagic recycling of mitochondria, endoplasmic reticulum (ER), and ribosomes (called mitophagy, ER-phagy, and ribophagy, respectively) in response to DNA damage. In addition, we have described the key events necessary for a comprehensive understanding of autophagy signaling networks. Finally, we have highlighted the importance of the autophagy activated by DDR and appropriate regulation of autophagic organelles, suggesting insights for future studies. Especially, DDR from DNA damaging agents including ionizing radiation (IR) or anti-cancer drugs, induces damage to subcellular organelles and autophagy is the key mechanism for removing impaired organelles.

The ubiquitin ligase RNF8 regulates Rho GTPases and promotes cytoskeletal changes and motility in triple-negative breast cancer cells

The ubiquitin ligase RNF8 is known to induce epithelial-to-mesenchymal (EMT) transition and metastasis in triple-negative breast cancer (TNBC). Besides EMT, Rho GTPases have been shown as key regulators in metastasis. In this study, we investigated the role of RNF8 in regulating Rho GTPases and cell motility. We find that RNF8 knockdown in TNBC cells attenuates the protein and mRNA levels of Ras homolog family member A (RHOA) and cell division cycle 42 (CDC42). We show that the formation of filopodia, focal adhesions, and the association of focal adhesions to stress fibers is impaired upon RNF8 knockdown. Cell migration is significantly inhibited by RNF8 knockdown. Our study suggests a potential novel role for RNF8 in mediating cell migration in TNBC through regulation of the Rho GTPases RHOA and CDC42.

Identification of the potential roles of ring finger protein 8 in TP53-mutant breast cancer

Breast cancer is one of the malignant tumors with the highest mortality rate. With the development of precise treatment technology for cancer, numerous molecular targets have been identified and applied in the treatment of diseases. The present study investigated the potential role of ring finger protein 8 (RNF8) in TP53-mutant breast cancer and explored its possible mechanisms of action through a combination of bioinformatics techniques and cell biology. The results revealed that significantly different genes were expressed in RNF8-knockout mice sequencing data compared with in the control group in the presence of TP53 mutations. Downregulated genes were significantly enriched in several pathways of cell proliferation and apoptosis regulation, development and transcription regulation, while upregulated genes were mainly enriched in immune response-associated signaling pathways. Therefore, the consensus genes of the major signaling pathways were further analyzed, revealing that among patients with TP53 wild-type breast cancer, the prognosis of patients with low expression levels of fibroblast growth factor receptor 1, LIM homeobox 2 and EPH receptor B2 was improved compared with that of patients with high expression levels, while among patients with TP53-mutant breast cancer, there was no significant difference in survival status. In addition, among patients with TP53-mutant breast cancer, the prognosis of patients with high BR serine/threonine kinase 1 expression was significantly improved compared with that in patients with low expression. Finally, cell biology experiments demonstrated that in TP53-mutant breast cancer cells (HCC1937), inhibition of RNF8 significantly inhibited the proliferation of TP53-mutant HCC1937 cells and promoted their apoptosis. The present findings may enrich the understanding of the role of RNF8 and indicated that RNF8 may be used as a potential molecular target in TP53-mutant breast cancer, which may lead to the development of clinical treatment strategies.

EGR1-mediated linc01503 promotes cell cycle progression and tumorigenesis in gastric cancer

Objectives

Long non‐coding RNAs (lncRNAs) are key mediators in various malignancies. Linc01503 was previously elucidated to promote gastric cancer (GC) cell invasion. However, the upstream mechanism of linc01503 and its involvement in GC cell cycle, apoptosis and tumorigenesis still remain unclear.

Materials and Methods

Bioinformatics analysis and quantitative reverse transcription polymerase chain reaction (qRT‐PCR) assays were implicated to detect linc01503 level in GC. The role of linc01503 was detected by in vitro functional assays and in vivo xenograft tumour models. The association between linc01503 and its upstream effector was identified by chromatin immunoprecipitation (ChIP) assays. The mechanistic model of linc01503 was clarified using subcellular separation, fluorescence in situ hybridization, RNA‐sequencing, RNA immunoprecipitation (RIP) and ChIP assays.

Results

Linc01503 was remarkably elevated in GC and tightly linked with the overall survival of patients with GC. The key transcription factor early growth response protein 1 (EGR1) critically activated the transcription of linc01503. Functionally, linc01503 knockdown resulted in the activation of apoptosis and G1/G0 phase arrest in GC. Mechanistically, linc01503 interacted with histone modification enzyme enhancer of zeste 2 (EZH2) and lysine (K)‐specific demethylase 1A (LSD1), thereby mediating the transcriptional silencing of dual‐specificity phosphatase 5 (DUSP5) and cyclin‐dependent kinase inhibitor 1A (CDKN1A) in GC.

Conclusions

EGR1‐activated linc01503 could epigenetically silence DUSP5/CDKN1A expression to mediate cell cycle progression and tumorigenesis, implicating it as a prospective target for GC therapeutics.

RNF8 Promotes Epithelial-Mesenchymal Transition in Lung Cancer Cells via Stabilization of Slug

RNF8 (ring finger protein 8), a RING finger E3 ligase best characterized for its role in DNA repair and sperm formation via ubiquitination, has been found to promote tumor metastasis in breast cancer recently. However, whether RNF8 also plays a role in other types of cancer, especially in lung cancer, remains unknown. We show here that RNF8 expression levels are markedly increased in human lung cancer tissues and negatively correlated with the survival time of patients. Overexpression of RNF8 promotes the EMT process and migration ability of lung cancer cells, while knockdown of RNF8 demonstrates the opposite effects. In addition, overexpression of RNF8 activates the PI3K/Akt signaling pathway, knockdown of RNF8 by siRNA inhibits this activation, and pharmacologic inhibition of PI3K/Akt in RNF8-overexpressing cells also reduces the expression of EMT markers and the ability of migration. Furthermore, RNF8 is found to directly interact with Slug and promoted the K63-Ub of Slug, and knockdown of Slug disrupts RNF8-dependent EMT in A549 cells, whereas overexpression of Slug rescues RNF8-dependent MET in H1299 cells, and depletion of RNF8 expression by shRNA inhibits metastasis of lung cancer cells in vivo. Taken together, these results indicate that RNF8 is a key regulator of EMT process in lung cancer and suggest that inhibition of RNF8 could be a useful strategy for lung cancer treatment. IMPLICATIONS: This study provides a new mechanistic insight into the novel role of RNF8 and identifies RNF8 as a potential new therapeutic target for the treatment of lung cancer.

DUBs Activating the Hedgehog Signaling Pathway: A Promising Therapeutic Target in Cancer

The Hedgehog (HH) pathway governs cell proliferation and patterning during embryonic development and is involved in regeneration, homeostasis and stem cell maintenance in adult tissues. The activity of this signaling is finely modulated at multiple levels and its dysregulation contributes to the onset of several human cancers. Ubiquitylation is a coordinated post-translational modification that controls a wide range of cellular functions and signaling transduction pathways. It is mediated by a sequential enzymatic network, in which ubiquitin ligases (E3) and deubiquitylase (DUBs) proteins are the main actors. The dynamic balance of the activity of these enzymes dictates the abundance and the fate of cellular proteins, thus affecting both physiological and pathological processes. Several E3 ligases regulating the stability and activity of the key components of the HH pathway have been identified. Further, DUBs have emerged as novel players in HH signaling transduction, resulting as attractive and promising drug targets. Here, we review the HH-associated DUBs, discussing the consequences of deubiquitylation on the maintenance of the HH pathway activity and its implication in tumorigenesis. We also report the recent progress in the development of selective inhibitors for the DUBs here reviewed, with potential applications for the treatment of HH-related tumors.

RNF8 induces β-catenin-mediated c-Myc expression and promotes colon cancer proliferation

DNA damage signals transducer RING finger protein 8 (RNF8) is involved in maintaining genomic stability by facilitating the repair of DNA double-strand breaks (DSB) via ubiquitin signaling. By analyzing the TCGA database and colon cancer tissue microarrays, we found that the expression level of RNF8 was positively correlated with that of c-Myc in colon cancer, which were closely associated with poor survival of colon cancer patients. Furthermore, overexpressing and knocking down RNF8 increased and decreased the expression of c-Myc in colon cancer cells, respectively. In addition, RNF8 interacted with β-catenin and facilitated its nuclear translocation by conjugating K63 polyubiquitination on it. These observations suggested a de novo role of RNF8 in promoting the progression of colon cancer by inducing β-catenin-mediated c-Myc expression.

CBP mediated DOT1L acetylation confers DOT1L stability and promotes cancer metastasis

Background and Aim: DOT1L regulates various genes involved in cancer onset and progression by catalyzing H3K79 methylation, but how DOT1L activity itself is regulated is unclear. Here, we aimed to identify specific DOT1L post-translational modifications that might regulate DOT1L activity and thus impact on colorectal cancer (CRC) progression. Methods: We conducted affinity purification and mass spectrometry to explore DOT1L post-translational modifications. We then established transwell migration and invasion assays to specifically investigate the role of DOT1L(K358) acetylation on CRC cellular behavior in vitro and a bioluminescence imaging approach to determine the role of DOT1L(K358) acetylation in CRC metastasis in vivo. We performed chromatin immunoprecipitation to identify DOT1L acetylation-controlled target genes. Finally, we used immunohistochemical staining of human tissue arrays to examine the relevance of DOT1L(K358) acetylation in CRC progression and metastasis and the correlation between DOT1L acetylation and CBP. Results: We found that CBP mediates DOT1L K358 acetylation in human colon cancer cells and positively correlates with CRC stages. Mechanistically, DOT1L acetylation confers DOT1L stability by preventing the binding of RNF8 to DOT1L and subsequent proteasomal degradation, but does not affect its enzyme activity. Once stabilized, DOT1L can catalyze the H3K79 methylation of genes involved in epithelial-mesenchymal transition, including SNAIL and ZEB1. An acetylation mimic DOT1L mutant (Q358) could induce a cancer-like phenotype in vitro, characterized by metastasis and invasion. Finally, DOT1L(K358) acetylation correlated with CRC progression and a poor survival rate as well as with high CBP expression. Conclusions: DOT1L acetylation by CBP drives CRC progression and metastasis. Targeting DOT1L deacetylation signaling is a potential therapeutic strategy for DOT1L-driven cancers.

Reduced miR-203 predicts metastasis and poor survival in esophageal carcinoma

We analyzed data from two non-coding RNA profiling arrays made available by the Gene Expression Omnibus (GEO) and found 17 miRNAs with remarkable differential expression between malignant and normal esophageal tissue. Correlation analysis between expression of these 17 miRNAs and patients’ clinicopathological characteristics showed that miR-203 was down-regulated in esophageal carcinoma (EC) tissues and was significantly associated with lymph node metastasis and poor overall survival. Overexpression of miR-203 significantly attenuated cellular proliferation, migration and invasion by EC cells in culture. Additionally, gene expression profiles and bioinformatics analysis revealed KIF5C to be a direct target of miR-203, and KIF5C overexpression partially counteracted the tumor inhibitory effects of miR-203 on EC cells. We also observed that miR-203, reduced KIFC5 protein levels, promoted cytoplasmic accumulation of Axin2, and reversed the invasive phenotype of EC cells. Taken together, these data demonstrate that miR-203 is a tumor suppressor in EC cells and its expression level could potentially be used as a prognostic indicator for EC patient outcomes.

Bioinformatic Identification of miR-622 Key Target Genes and Experimental Validation of the miR-622-RNF8 Axis in Breast Cancer

Breast cancer is the leading cause of cancer-associated deaths among females. In recent decades, microRNAs (miRNAs), a type of short non-coding RNA that regulates gene expression at the post-transcription level, have been reported to participate in the regulation of many hub genes associated with tumorigenesis, tumor progression, and metastasis. However, the precise mechanism by which miRNAs regulate breast cancer metastasis remains poorly discussed, which limits the opportunity for the development of novel, effective therapeutic targets. Here, we aimed to determine the miR-622-related principal regulatory mechanism in cancer. First, we found that miR-622 was significantly related to a poor prognosis in various cancers. By utilizing an integrated miRNA prediction process, we identified 77 promising targets and constructed a protein-protein interaction network. Furthermore, enrichment analyses, including GO and KEGG pathway analyses, were performed to determine the potential function of miR-622, which revealed regulation networks and potential functions of miR-622. Then, we identified a key cluster comprised of six hub genes in the protein-protein interaction network. These genes were further chosen for pan-cancer expression, prognostic and predictive marker analyses based on the TCGA and GEO datasets to mine the potential clinical values of these hub genes. To further validate our bioinformatic results, the regulatory axis of miR-622 and RNF8, one of the hub genes recently reported to promote breast cancer cell EMT process and breast cancer metastasis, was selected as in vitro proof of concept. In vitro, we demonstrated the direct regulation of RNF8 by miR-622 and found that the predicted miR-622-RNF8 axis could regulate RNF8-induced epithelial-mesenchymal transition, cell migration, and cell viability. These results were further demonstrated with rescue experiments. We established a closed-loop miRNA-target-phenotype research model that integrated the bioinformatic analysis of the miRNA target genes and experimental validation of the identified key miRNA-target-phenotype axis. We not only identified the hub target genes of miR-622 in silico but also revealed the regulatory mechanism of miR-622 in breast cancer cell EMT process, viability, and migration in vitro for the first time.

The p97-Ataxin 3 complex regulates homeostasis of the DNA damage response E3 ubiquitin ligase RNF8

The E3 ubiquitin ligase RNF8 (RING finger protein 8) is a pivotal enzyme for DNA repair. However, RNF8 hyper-accumulation is tumour-promoting and positively correlates with genome instability, cancer cell invasion, metastasis and poor patient prognosis. Very little is known about the mechanisms regulating RNF8 homeostasis to preserve genome stability. Here, we identify the cellular machinery, composed of the p97/VCP ubiquitin-dependent unfoldase/segregase and the Ataxin 3 (ATX3) deubiquitinase, which together form a physical and functional complex with RNF8 to regulate its proteasome-dependent homeostasis under physiological conditions. Under genotoxic stress, when RNF8 is rapidly recruited to sites of DNA lesions, the p97-ATX3 machinery stimulates the extraction of RNF8 from chromatin to balance DNA repair pathway choice and promote cell survival after ionising radiation (IR). Inactivation of the p97-ATX3 complex affects the non-homologous end joining DNA repair pathway and hypersensitises human cancer cells to IR. We propose that the p97-ATX3 complex is the essential machinery for regulation of RNF8 homeostasis under both physiological and genotoxic conditions and that targeting ATX3 may be a promising strategy to radio-sensitise BRCA-deficient cancers.

miR-214 inhibits epithelial-mesenchymal transition of breast cancer cells via downregulation of RNF8

MicroRNAs (miRNAs) are a class of endogenous noncoding genes that regulate gene expression at the posttranscriptional level. In recent decades, miRNAs have been reported to play important roles in tumor growth and metastasis, while some reported functions of a specific miRNA in tumorigenesis are contradictory. In this study, we reevaluated the role of miR-214, which has been reported to serve as an oncogene or anti-oncogene in breast cancer metastasis. We found that miR-214 inhibited breast cancer via targeting RNF8, a newly identified regulator that could promote epithelial-mesenchymal transition (EMT). Specifically, the survival rate of breast cancer patients was positively correlated with miR-214 levels and negatively correlated with RNF8 expression. The overexpression of miR-214 inhibited cell proliferation and invasion of breast cancer, while suppression of miR-214 by chemically modified antagomir enhanced the proliferation and invasion of breast cancer cells. Furthermore, miR-214 could modulate the EMT process via downregulating RNF8. To our knowledge, this is the first report that reveals the role of the miR-214-RNF8 axis in EMT, and our results demonstrate a novel mechanism for miR-214 acting as a tumor suppressor through the regulation of EMT.

ESRP1 Induces Cervical Cancer Cell G1-Phase Arrest Via Regulating Cyclin A2 mRNA Stability

Accumulating evidence indicates that epithelial splicing regulatory protein 1 (ESRP1) can inhibit the epithelial-to-mesenchymal transition (EMT), thus playing a central role in regulating the metastatic progression of tumors. However, it is still not clear whether ESRP1 directly influences the cell cycle, or what the possible underlying molecular mechanisms are. In this study, we showed that ESRP1 protein levels were significantly correlated with the Ki-67 proliferative index (r = −0.521; p < 0.01), and that ESRP1 overexpression can significantly inhibit cervical carcinoma cell proliferation and induced G1-phase arrest by downregulating cyclin A2 expression. Importantly, ESRP1 can bind to GGUGGU sequence in the 3′UTR of the cyclin A2 mRNA, and ESRP1 overexpression significantly decreases the stability of the cyclin A2 mRNA. In addition, our experimental results confirm that ESRP1 overexpression results in enhanced CDC20 expression, which is known to be responsible for cyclin A2 degradation. This study provides the first evidence that ESRP1 overexpression induces G1-phase cell cycle arrest via reducing the stability of the cyclin A2 mRNA, and inhibits cervical carcinoma cell proliferation. The findings suggest that the ESRP1/cyclin A2 regulatory axis may be essential as a regulator of cell proliferation, and may thus represent an attractive target for cervical cancer prevention and treatment.

TGF-β-Mediated Epithelial-Mesenchymal Transition and Cancer Metastasis

Transforming growth factor β (TGF-β) is a secreted cytokine that regulates cell proliferation, migration, and the differentiation of a plethora of different cell types. Consistent with these findings, TGF-β plays a key role in controlling embryogenic development, inflammation, and tissue repair, as well as in maintaining adult tissue homeostasis. TGF-β elicits a broad range of context-dependent cellular responses, and consequently, alterations in TGF-β signaling have been implicated in many diseases, including cancer. During the early stages of tumorigenesis, TGF-β acts as a tumor suppressor by inducing cytostasis and the apoptosis of normal and premalignant cells. However, at later stages, when cancer cells have acquired oncogenic mutations and/or have lost tumor suppressor gene function, cells are resistant to TGF-β-induced growth arrest, and TGF-β functions as a tumor promotor by stimulating tumor cells to undergo the so-called epithelial-mesenchymal transition (EMT). The latter leads to metastasis and chemotherapy resistance. TGF-β further supports cancer growth and progression by activating tumor angiogenesis and cancer-associated fibroblasts and enabling the tumor to evade inhibitory immune responses. In this review, we will consider the role of TGF-β signaling in cell cycle arrest, apoptosis, EMT and cancer cell metastasis. In particular, we will highlight recent insights into the multistep and dynamically controlled process of TGF-β-induced EMT and the functions of miRNAs and long noncoding RNAs in this process. Finally, we will discuss how these new mechanistic insights might be exploited to develop novel therapeutic interventions.

The Functions of DNA Damage Factor RNF8 in the Pathogenesis and Progression of Cancer

The really interesting new gene (RING) finger protein 8 (RNF8) is a central factor in DNA double strand break (DSB) signal transduction. DSB damage is the most toxic type of DNA damage to cells and is related to genomic instability. Multiple roles for RNF8 have been identified in DNA damage response as well as in other functions, such as telomere protection, cell cycle control and transcriptional regulation. These functions are closely correlated to tumorigenesis and cancer progression. Indeed, deficiency of RNF8 caused spontaneous tumorigenesis in a mouse model. Deciphering these mechanisms of RNF8 may shed light on strategies for cancer treatment. In this review, we summarize the current understanding of both classical and nonclassical functions of RNF8, and discuss its roles in the pathogenesis and progression of tumor.

Abnormally elevated USP37 expression in breast cancer stem cells regulates stemness, epithelial-mesenchymal transition and cisplatin sensitivity

Background

Recent studies have indicated that deubiquitinating enzymes (DUBs) are related to the stem-cell pathway network and chemo-resistance in cancer. Ubiquitin-specific peptidase 37 (USP37), a novel DUB, was identified to be a potential factor associated with tumor progression. However, the biological functions of USP37 in breast cancer remain unclear.

Methods

The distribution of USP37 expression in breast cancer and the correlation between USP37 expression and the overall survival rate were detected by The Cancer Genome Atlas (TCGA) database. Gene set enrichment analysis (GSEA) was utilized to evaluate potential mechanism of USP37 in breast cancer. The USP37 expression in breast cancer tissues and breast cancer cell lines were detected by immunohistochemistry and western blotting. Sorting of breast cancer stem cells (BCSCs) were by using MACS assay. In vitro and in vivo assays were performed to examine the biological functions of USP37 in breast cancer cells. MG132, CHX chase, immunofluorescence staining and co-immunoprecipitation assays were used to test the interaction between USP37 and Gli-1.

Results

Bioinformatics analysis demonstrated that USP37 gene was elevated in breast cancer tissues and its overexpression was strongly correlated with the increased mortality rate. GSEA analysis showed that USP37 expression was positively associated with cell growth and metastasis while negatively related to cell apoptosis in the TCGA breast cancer samples. USP37 expression was elevated in breast cancer tissues and breast cancer cell lines. Moreover, we also detected that USP37 was overexpressed in BCSCs. USP37 regulated the ability of cell invasion, epithelial-mesenchymal transition (EMT), stemness and cisplatin sensitivity in breast cancer cell lines. Additionally, USP37 knockdown inhibited tumorigenicity and increased anticancer effect of cisplatin in vivo. Knockdown of USP37 significantly decreased hedgehog (Hh) pathway components Smo and Gli-1. Gli-1 was stabilized by USP37 and they interacted with each other. Further studies indicated that USP37 knockdown could inhibit the stemness, cell invasion and EMT in breast cancer via downregulation of Hh pathway.

Conclusions

These findings reveal that USP37 is highly expressed in BCSCs and is correlated with poor prognosis in breast cancer patients. USP37 can regulate the stemness, cell invasion and EMT via Hh pathway, and decreased USP37 confers sensitivity to cisplatin in breast cancer cells. USP37 is required for the regulation of breast cancer progression, as well as a critical target for clinical treatment of breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0934-9) contains supplementary material, which is available to authorized users.

Post-Translational Modifications of H2A Histone Variants and Their Role in Cancer

Histone variants are chromatin components that replace replication-coupled histones in a fraction of nucleosomes and confer particular characteristics to chromatin. H2A variants represent the most numerous and diverse group among histone protein families. In the nucleosomal structure, H2A-H2B dimers can be removed and exchanged more easily than the stable H3-H4 core. The unstructured N-terminal histone tails of all histones, but also the C-terminal tails of H2A histones protrude out of the compact structure of the nucleosome core. These accessible tails are the preferential target sites for a large number of post-translational modifications (PTMs). While some PTMs are shared between replication-coupled H2A and H2A variants, many modifications are limited to a specific histone variant. The present review focuses on the H2A variants H2A.Z, H2A.X, and macroH2A, and summarizes their functions in chromatin and how these are linked to cancer development and progression. H2A.Z primarily acts as an oncogene and macroH2A and H2A.X as tumour suppressors. We further focus on the regulation by PTMs, which helps to understand a degree of context dependency.

MiR-520f promotes cell aggressiveness by regulating fibroblast growth factor 16 in hepatocellular carcinoma

Cancer metastasis is a multistep cellular process, which has be confirmed one of mainly causes of cancer associated-death in hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) participate in tumorigenesis function as either tumor suppressor genes or oncogenes. In order to elaborate the critical miRNAs and their targets in HCC, we compared the differential expression of miRNA between HCC tissues and normal tissues. Microarray analysis revealed there were several significantly up-expression miRNAs in HCC, compared to normal solid tissue. Among them, the expression of miR-520f was the most over-expression in HCC cell lines than that in human normal liver cells LO2, as well as up-regulated in HCC than that in the corresponding normal tissues. Moreover, Kaplan Meier-plotter analyses revealed that higher miR-520f levels were negatively correlated with poor overall survival. By applying bioinformatics methods to identify the targeting genes of miRNA, we demonstrated that fibroblast growth factor 16 (FGF16) was the miR-520f-targeted gene. Meanwhile, FGF16 exhibited similar expression patterns to miR-520f in HCC. Forced miR-520f expression accelerated HCC cells proliferation and aggressiveness in vitro and in vivo, whereas down-regulation of miR-520f caused an opposite outcome. Moreover, over-expression of FGF16 was closely related to the metastatic potential of HCC cells. Herein, we also confirmed that ectopic expression of FGF16 in HCC cells promoted proliferation, colony formation, and increased migration, invasion of HCC cells in vitro. Collectively, our results indicated that over-expression of miR-520f and FGF16 was positively associated with aggressive phenotypes and poor survival of patients with HCC, and miR-520f promoted HCC aggressive phenotypes by regulating the expression of FGF16. MiR-520f may be employed as a prognostic factor and therapeutic target for HCC.

Collagen triple helix repeat containing-1 negatively regulated by microRNA-30c promotes cell proliferation and metastasis and indicates poor prognosis in breast cancer

Background

Collagen triple helix repeat containing-1 (CTHRC1), which was firstly identified overexpressed in the adventitia and neointima of injured rat arteries, could inhibit collagen expression and increase cell migration. It was then found to be ubiquitously expressed in numerous cell types such as fibroblasts and smooth muscle cells, and aberrantly up-regulated in several malignant tumors. However, the functional role of CTHRC1 and its related mechanism in breast cancer still remains unclear.

Methods

CTHRC1 expressions in breast cancer tissues and cells were assessed by qRT-PCR, western blot and immunohistochemistry. The relative expression level of miR-134, miR-155, miR-30c and miR-630 in breast cancer cells respectively was detected by qRT-PCR. Wild type (Wt) and Mutant type (Mut) CTHRC1 3’UTR sequences were cloned into a psi-CHECK2 reporter vector, and the relative luciferase activity was detected by dual-luciferase reporter assay in indicated cells. The effect of ectopic expression of miR-30c or gain and loss of CTHRC1 on cell viability, cell proliferation, cell cycle progression and apoptosis, cell invasion and migration was respectively detected by CCK-8 assay, colony formation assay, flow cytometry analysis, transwell invasion/migration assay. Protein levels of β-catenin, active β-catenin, normal and phosphorylated form of GSK-3β were detected by western blot in indicated cells. Immunofluorescence staining of β-catenin was performed to observe nuclear localization.

Results

We found CTHRC1 was frequently up-regulated in human breast cancer cells and tissues. Then our cohort study and further meta-analysis validated high expression of CTHRC1 was associated with aggressive clinicopathological features and poor clinical outcome of breast cancer patients. In addition, CTHRC1 promoted cell proliferation, invasion and migration and suppressed cell apoptosis in breast cancer, which might be by activating GSK-3β/β-catenin signaling and inhibiting Bax/Caspase-9/Caspase-3 signaling respectively; and these biological functions of CTHRC1 could be directly negatively regulated by miR-30c.

Conclusion

Taken together, we identified the role of miR-30c/CTHRC1 axis in breast cancer progression and demonstrated CTHRC1 may serve as a prognostic biomarker and therapeutic target for breast cancer.

Electronic supplementary material

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Silencing of advanced glycosylation and glycosylation and product-specific receptor (RAGE) inhibits the metastasis and growth of non-small cell lung cancer

Non-small cell lung cancer (NSCLC) constitutes the main cases of lung cancer and is the world's most common and lethal cancer owing to regional invasion or distant metastasis. Growing morbidity and lethality demonstrates that valid molecular target in management of NSCLC metastasis is still absence. The receptor of advanced glycation end-products (RAGE) has been identified as an oncogenic gene and appears to promote the growth and metastasis of various cancers. Here, we investigated if RAGE targeted by RNA interference (RNAi) might have certain effect on the restraint of the growth of NSCLC and tumor metastasis. Wound healing and Transwell invasion assays indicated that RAGE favored the metastatic capabilities of NSCLC H1975 cells. Besides, soft-agar colony assay revealed that silencing RAGE significantly blocked colony-forming capability of H1975 cells in vitro. Furthermore, we observed that RAGE participated in H1975 cells growth, metastasis and epithelial-mesenchymal transition (EMT) by regulating interdict crux intracellular signaling pathways, including phosphatidylinositol-3 kinase/serine-threonine kinase (PI3K/AKT) and V-Ki-ras2 kirsten rat sarcoma viral oncogene homolog/RAF proto-oncogene serine/threonine-protein kinase (KRAS/RAF-1). In xenograft model, significantly reduction intumor growth and Ki67 expression was demonstrated in nude mice inoculation with RAGE down-regulation H1975 cells. To conclude, our study demonstrated that RAGE played a crucial role in the metastasis and growth of NSCLC by regulating PI3K/AKT and KRAS/RAF-1 signaling pathways, thereby might be a promising therapeutic target for NSCLC.

CXCL10 accelerates EMT and metastasis by MMP-2 in hepatocellular carcinoma

Human malignant hepatocellular carcinoma (HCC) is a common tumor, which severely threatens human health and shortens longevity. The poor prognosis of HCC is primarily attributed to distant metastases. C-X-C motif chemokine 10 (CXCL10) regulates the control of several cellular and developmental processes including tumor cell proliferation, apoptosis, and cell metastasis. Previous studies have confirmed that CXCL10 functions as an oncogene in several cancers. However, the expression and biological functions of CXCL10 in HCC, especially with regard to metastasis, need further investigation. In this study, CXCL10 was found to be over expressed in invasive HCC cells and HCC clinical samples. While the over-expression of CXCL10 enhanced migration, invasion, and metastasis of HCC cells in vitro as well as in vivo, silencing of CXCL10 resulted in inhibition of HCC cell metastasis. Further, CXCL10 was found to accelerate epithelial-mesenchymal transition of HCC cells. The microarray analysis indicated that matrix metallopeptidase-2 (MMP-2) functions as a downstream factor of CXCL10. This study demonstrates that CXCL10 partakes in the metastasis of HCC by activating MMP-2 expression.

Identification of RING-box 2 as a potential target for combating colorectal cancer growth and metastasis

Development of cancer metastasis is a key contributor to mortality in patients with colorectal cancer. High expression of RING-box 2 (RBX2) in cancer cells is known to play a key role in tumor progression. However, the role of RBX2 in colorectal cancer progression is not well elucidated. In this study, we silenced RBX2 via CRISPR/Cas9 in two colorectal cancer cell lines, HCT116 and SW480. RBX2 knockout attenuated proliferation, colony formation and enhanced sensitivity of colorectal cancer cells to paclitaxel treatment. Invasive property of HCT116 and SW480 cells was also attenuated by RBX2 silencing. We confirmed that increased RBX2 correlated with higher tumor cells growth and metastasis abilities by ectopic expression of RBX2 in HCT116 and SW480 cells. In vivo studies suggested that knockout of RBX2 inhibited xenografts growth and metastasis to lung tissue, whereas ectopic expression of RBX2 promoted these cellular functions. Mechanically, RBX2 induced gastric cancer cell growth and metastasis by activating mammalian target of rapamycin/S6 kinase 1 (mTOR/S6K1). Treatment of everolimus, the specific mTOR inhibitor, significantly attenuated RBX2-mediated cell proliferation and mobility in vitro. Taken together, these results revealed a novel role of RBX2 in colorectal cancer cell growth and metastasis via the mTOR pathway and suggested RBX2 may serve as a therapeutic target in colorectal cancer.

GABPA predicts prognosis and inhibits metastasis of hepatocellular carcinoma

Background

Increasing evidence indicates that abnormal expression of GABPA is associated with tumor development and progression. However, the function and clinicopathological significance of GABPA in hepatocellular carcinoma (HCC) remain obscure.

Methods

The mRNA and protein expression of GABPA in HCC clinical specimens and cell lines was examined by real-time PCR and western blotting, respectively. Follow-up data were used to uncover the relationship between GABPA expression and the prognosis of HCC patients. HCC cell lines stably overexpressing or silencing GABPA were established to explore the function of GABPA in HCC cell migration and invasion by Transwell and wound healing assays in vitro and in a xenograft model in vivo. Restoration of function analysis was used to examine the underlying molecular mechanisms.

Results

GABPA was downregulated at the protein and mRNA levels in HCC tissues compared with adjacent normal tissues. Decreased GABPA expression was correlated with alpha-fetoprotein levels (P = 0.001), tumor grade (P = 0.017), and distant metastasis (P = 0.021). Kaplan-Meier survival analysis showed that patients with lower GABPA expression had significantly shorter survival times than those with higher GABPA (P = 0.031). In vivo and in vitro assays demonstrated that GABPA negatively regulated HCC cell migration and invasion, and the effect of GABPA on HCC cell migration was mediated at least partly by the regulation of E-cadherin.

Conclusions

Collectively, our data indicate that GABPA inhibits HCC cell migration by modulating E-cadherin and could serve as a novel biomarker for HCC prognosis. GABPA may act as a tumor suppressor during HCC progression and metastasis, and is a potential therapeutic target in HCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3373-7) contains supplementary material, which is available to authorized users.

FOXQ1 promotes cancer metastasis by PI3K/AKT signaling regulation in colorectal carcinoma

Colorectal cancer is one of the major health problems, with invade surrounding tissues, and migrate to distant organs being the most critical concern, thus identified metastasis associated hallmarks and more efficacious treatment are urgently needed. It found that forkhead box q1 (FOXQ1) is aberrant expression in variety of human cancers and FOXQ1 is involved in oncogenic pathways. However, the role of FOXQ1 has been unexplored in colorectal cancer metastasis to date. Here, expression of FOXQ1 was higher in colorectal cancer tissue samples and cancer cell lines than in normal colorectal tissue and cell lines. Further research suggested that FOXQ1 positively regulated cell proliferation in colorectal cancer and down-regulation of CDK6, extracellular regulated protein kinases 1/2 (ERK1/2) and mammalian target of rapamycin (mTOR). In corresponding to this result, over-expression of FOXQ1 significantly promoted colorectal cancer growth in vivo. Moreover, down regulation of FOXQ1 expression in colorectal carcinoma cell HCT116 and LOVO strikingly inhibits tumor growth in vivo. Finally, FOXQ1-dependent inhibition of colorectal cancer cell migration and invasion and down-regulation of focal adhesion kinase (FAK), phosphatidyl inositol 3-kinase (PI3K) phosphorylation, AKT (v-akt murine thymoma viral oncogene) phosphorylation and matrix metalloproteinase-2/9 (MMP-2/9) expression. These integrated efforts have identified FOXQ1 as a tumor promoter and might provide promising approaches for colorectal cancer metastasis treatment.

RNF8 identified as a co-activator of estrogen receptor α promotes cell growth in breast cancer

The ring finger protein 8 (RNF8), a key component of protein complex crucial for DNA-damage response, consists of a forkhead-associated (FHA) domain and a really interesting new gene (RING) domain that enables it to function as an E3 ubiquitin ligase. However, the biological functions of RNF8 in estrogen receptor α (ERα)-positive breast cancer and underlying mechanisms have not been fully defined. Here, we have explored RNF8 as an associated partner of ERα in breast cancer cells, and co-activates ERα-mediated transactivation. Accordingly, RNF8 depletion inhibits the expression of endogenous ERα target genes. Interestingly, our results have demonstrated that RNF8 increases ERα stability at least partially if not all via triggering ERα monoubiquitination. RNF8 functionally promotes breast cancer cell proliferation. RNF8 is highly expressed in clinical breast cancer samples and the expression of RNF8 positively correlates with that of ERα. Up-regulation of ERα-induced transactivation by RNF8 might contribute to the promotion of breast cancer progression by allowing enhancement of ERα target gene expression. Our study describes RNF8 as a co-activator of ERα increases ERα stability via post-transcriptional pathway, and provides a new insight into mechanisms for RNF8 to promote cell growth of ERα-positive breast cancer.

A High-Throughput Screening Strategy for Development of RNF8-Ubc13 Protein-Protein Interaction Inhibitors

The ubiquitin-proteasome system plays an essential role in a broad range of cellular signaling pathways. Ubiquitination is a posttranslational protein modification that involves the action of an enzymatic cascade (E1, E2, and E3 enzymes) for the covalent attachment of ubiquitin to target proteins. The emerging knowledge of the molecular mechanisms and correlation of deregulation of the ubiquitin system in human diseases is uncovering new opportunities for therapeutics development. The E3 ligase RNF8 acts in cooperation with the heterodimeric E2 enzyme Ubc13/Uev1a to generate ubiquitin conjugates at the sides of DNA double-strand breaks, and recent findings suggest RNF8 as a potential therapeutic target for the treatment of breast cancer. Here, we present a novel high-throughput screening (HTS)-compatible assay based on the AlphaScreen technology to identify inhibitors of the RNF8-Ubc13 protein-protein interaction, along with a follow-up strategy for subsequent validation. We have adapted the AlphaScreen assay to a 384-well format and demonstrate its reliability, reproducibility, and suitability for automated HTS campaigns. In addition, we have established a biochemical orthogonal homogeneous time-resolved fluorescence (HTRF) assay in HTS format and a cellular microscopy-based assay allowing verification of the primary hits. This strategy will be useful for drug screening programs aimed at RNF8-Ubc13 modulation.

PLK1 promotes epithelial-mesenchymal transition and metastasis of gastric carcinoma cells

Cancer cell epithelial-mesenchymal transition (EMT) is the crucial event for cancer progression and plays a vital role in the metastasis of cancer cells. Activation of Polo-like kinase 1 (PLK1) signaling has been implicated as the critical event in several tumor metastasis and EMT, however, whether PLK1 participates in gastric carcinoma metastasis and EMT still remains unclear. For this study, we elucidated the potential physiological function of PLK1 in the metastasis of gastric tumors, as well its distinct role in cells EMT and subsequently determined the mechanism involved in PLK1 regulated. Immunoblotting assay and Oncomine data mining analysis indicated that PLK1 expression was highly up-regulated in gastric carcinoma. Kaplan-Meier survival analysis for the relationship between survival outcomes and PLK1 expression in gastric carcinoma was performed with an online Kaplan-Meier plotter (http://kmplot.com/analysis/). Over-expression of PLK1 in gastric cancer cells SGC-7901 and MKN-28 significantly promoted cells profound morphological changes and enhanced metastatic ability of tumor cells. On the contrary, silencing of PLK1 induced mesenchymal epithelial transition (MET)-like morphological and inhibited the metastatic process. Furthermore, we found that the metastatic characters promoting effects of PLK1 in gastric carcinoma was related to the activation of protein kinase B (AKT). Our mechanistic investigations revealed that AKT inhibition reversed PLK1-induced EMT, blocked gastric carcinoma cells invasiveness and metastasis. Additionally, over-expression of AKT promoted the migratory and invasion ability of the two cell lines, which was disrupted by PLK1 down-regulation. To conclude, our findings demonstrate that PLK1 accelerates the metastasis and epithelial-mesenchyme transition of gastric cancer cells through regulating the AKT pathway.

Two-faced activity of RNF8: What "twists" it from a genome guardian to a cancer facilitator?

The RING finger protein 8 (RNF8)-induced ubiquitination signaling cascade promotes DNA repair and maintains genomic stability. Our study reveals an unexpected action of RNF8 in promoting cancer metastasis, cancer stem cell formation, and chemoresistance through the regulation of TWIST lysine 63 (K63)-linked ubiquitination, suggesting that RNF8 may serve as a new cancer prognosis marker and therapeutic target.

ATF2 predicts poor prognosis and promotes malignant phenotypes in renal cell carcinoma

Background

Activating transcription factor 2 (ATF2) is a basic helix-loop-helix transcription factor, which has been shown to participate in the pathobiology of numerous cancers. However, the role of ATF2 in renal cell carcinoma (RCC) remains unclear.

Methods

ATF2 knockdown and overexpression studies were performed in RCC cells to evaluate changes in cell viability, cell cycle, apoptosis, migration and invasion. Xenograft models were used to examine the tumorigenic and metastatic capability of RCC cells upon ATF2 suppression. The expression of ATF2 in human RCC samples was determined using immunohistochemistry on a tissue microarray.

Results

ATF2 knockdown in RCC cells reduced their proliferative and metastatic potentials, whereas ATF2 overexpression enhanced these properties. Mechanistic studies revealed that the transcription of CyclinB1, CyclinD1, Snail and Vimentin was directly regulated by ATF2 in RCC cells. Moreover, ATF2 was shown to be highly expressed in RCC tissues, especially in tumors with metastases. High expression of ATF2 correlated with aggressive clinico-pathological characteristics and predicted poor prognosis of RCC patients.

Conclusions

ATF2 exerts an oncogenic role in RCC and could serve as an important prognostic biomarker.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0383-2) contains supplementary material, which is available to authorized users.