Induction of autophagy and senescence by knockdown of ROC1 E3 ubiquitin ligase to suppress the growth of liver cancer cells

SCFFBXW5-mediated degradation of AQP3 suppresses autophagic cell death through the PDPK1-AKT-MTOR axis in hepatocellular carcinoma cells

AQP3 (aquaporin 3 (Gill blood group)), a member of the AQP family, is an aquaglyceroporin which transports water, glycerol and small solutes across the plasma membrane. Beyond its role in fluid transport, AQP3 plays a significant role in regulating various aspects of tumor cell behavior, including cell proliferation, migration, and invasion. Nevertheless, the underlying regulatory mechanism of AQP3 in tumors remains unclear. Here, for the first time, we report that AQP3 is a direct target for ubiquitination by the SCFFBXW5 complex. In addition, we revealed that downregulation of FBXW5 significantly induced AQP3 expression to prompt macroautophagic/autophagic cell death in hepatocellular carcinoma (HCC) cells. Mechanistically, AQP3 accumulation induced by FBXW5 knockdown led to the degradation of PDPK1/PDK1 in a lysosomal-dependent manner, thus inactivating the AKT-MTOR pathway and inducing autophagic death in HCC. Taken together, our findings revealed a previously undiscovered regulatory mechanism through which FBXW5 degraded AQP3 to suppress autophagic cell death via the PDPK1-AKT-MTOR axis in HCC cells.Abbreviation: BafA1: bafilomycin A1; CQ: chloroquine; CRL: CUL-Ring E3 ubiquitin ligases; FBXW5: F-box and WD repeat domain containing 5; HCC: hepatocellular carcinoma; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; 3-MA: 3-methyladenine; PDPK1/PDK1: 3-phosphoinositide dependent protein kinase 1; RBX1/ROC1: ring-box 1; SKP1: S-phase kinase associated protein 1; SCF: SKP1-CUL1-F-box protein.

Blockade of a novel MAP4K4-LATS2-SASH1-YAP1 cascade inhibits tumorigenesis and metastasis in luminal breast cancer

Novel components in the noncanonical Hippo pathway that mediate the growth, metastasis, and drug resistance of breast cancer (BC) cells need to be identified. Here, we showed that expression of SAM and SH3 domain-containing protein 1 (SASH1) is negatively correlated with expression of mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) in a subpopulation of patients with luminal-subtype BC. Downregulated SASH1 and upregulated MAP4K4 synergistically regulated the proliferation, migration, and invasion of luminal-subtype BC cells. The expression of LATS2, SASH1, and YAP1 and the phosphorylation of YAP1 were negatively regulated by MAP4K4, and LATS2 then phosphorylated SASH1 to form a novel MAP4K4-LATS2-SASH1-YAP1 cascade. Dephosphorylation of Yes1 associated transcriptional regulator (YAP1), YAP1/TAZ nuclear translocation, and downstream transcriptional regulation of YAP1 were promoted by the combined effects of ectopic MAP4K4 expression and SASH1 silencing. Targeted inhibition of MAP4K4 blocked proliferation, cell migration, and ER signaling both in vitro and in vivo. Our findings reveal a novel MAP4K4-LATS2-SASH1-YAP1 phosphorylation cascade, a noncanonical Hippo pathway that mediates ER signaling, tumorigenesis, and metastasis in breast cancer. Targeted intervention with this noncanonical Hippo pathway may constitute a novel alternative therapeutic approach for endocrine-resistant BC.

A Conversation with ChatGPT on Contentious Issues in Senescence and Cancer Research

Artificial intelligence (AI) platforms, such as Generative Pretrained Transformer (ChatGPT), have achieved a high degree of popularity within the scientific community due to their utility in providing evidence-based reviews of the literature. However, the accuracy and reliability of the information output and the ability to provide critical analysis of the literature, especially with respect to highly controversial issues, has generally not been evaluated. In this work, we arranged a question/answer session with ChatGPT regarding several unresolved questions in the field of cancer research relating to therapy-induced senescence (TIS), including the topics of senescence reversibility, its connection to tumor dormancy, and the pharmacology of the newly emerging drug class of senolytics. ChatGPT generally provided responses consistent with the available literature, although occasionally overlooking essential components of the current understanding of the role of TIS in cancer biology and treatment. Although ChatGPT, and similar AI platforms, have utility in providing an accurate evidence-based review of the literature, their outputs should still be considered carefully, especially with respect to unresolved issues in tumor biology. SIGNIFICANCE STATEMENT: Artificial Intelligence platforms have provided great utility for researchers to investigate biomedical literature in a prompt manner. However, several issues arise when it comes to certain unresolved biological questions, especially in the cancer field. This work provided a discussion with ChatGPT regarding some of the yet-to-be-fully-elucidated conundrums of the role of therapy-induced senescence in cancer treatment and highlights the strengths and weaknesses in utilizing such platforms for analyzing the scientific literature on this topic.

Protein neddylation and its role in health and diseases

NEDD8 (Neural precursor cell expressed developmentally downregulated protein 8) is an ubiquitin-like protein that is covalently attached to a lysine residue of a protein substrate through a process known as neddylation, catalyzed by the enzyme cascade, namely NEDD8 activating enzyme (E1), NEDD8 conjugating enzyme (E2), and NEDD8 ligase (E3). The substrates of neddylation are categorized into cullins and non-cullin proteins. Neddylation of cullins activates CRLs (cullin RING ligases), the largest family of E3 ligases, whereas neddylation of non-cullin substrates alters their stability and activity, as well as subcellular localization. Significantly, the neddylation pathway and/or many neddylation substrates are abnormally activated or over-expressed in various human diseases, such as metabolic disorders, liver dysfunction, neurodegenerative disorders, and cancers, among others. Thus, targeting neddylation becomes an attractive strategy for the treatment of these diseases. In this review, we first provide a general introduction on the neddylation cascade, its biochemical process and regulation, and the crystal structures of neddylation enzymes in complex with cullin substrates; then discuss how neddylation governs various key biological processes via the modification of cullins and non-cullin substrates. We further review the literature data on dysregulated neddylation in several human diseases, particularly cancer, followed by an outline of current efforts in the discovery of small molecule inhibitors of neddylation as a promising therapeutic approach. Finally, few perspectives were proposed for extensive future investigations.

A common molecular and cellular pathway in developing Alzheimer and cancer

Globally cancer and Alzheimer's disease (AD) are two major diseases and still, there is no clearly defined molecular mechanism. There is an opposite relation between cancer and AD which are the proportion of emerging cancer was importantly slower in AD patients, whereas slow emerging AD in patients with cancer. In cancer, regulation of cell mechanisms is interrupted by an increase in cell survival and proliferation, while on the contrary, AD is related to augmented neuronal death, that may be either produced by or associated with amyloid-β (Aβ) and tau deposition. Stated that the probability that disruption of mechanisms takes part in the regulation of cell survival/death and might be implicated in both diseases. The mechanism of actions such as DNA-methylation, genetic polymorphisms, or another mechanism of actions that induce alteration in the action of drugs with significant roles in resolving the finding to repair and live or die might take part in the pathogenesis of these two ailments. The functions of miRNA, p53, Pin1, the Wnt signaling pathway, PI3 KINASE/Akt/mTOR signaling pathway GRK2 signaling pathway, and the pathophysiological role of oxidative stress are presented in this review as potential candidates which hypothetically describe inverse relations between cancer and AD. Innovative materials almost mutual mechanisms in the aetiology of cancer and AD advocates novel treatment approaches. Among these treatment strategies, the most promising use treatment such as tyrosine kinase inhibitor, nilotinib, protein kinase C, and bexarotene.

Repression of YEATS2 induces cellular senescence in hepatocellular carcinoma and inhibits tumor growth

Hepatocellular carcinoma (HCC) stands as the third leading cause of cancer-related fatalities globally. In this study, we observed a significant increase in the expression level of the YEATS2 gene in HCC patients, and it is negatively correlated with the patients' survival rate. While we have previously identified the association between YEATS2 and the survival of pancreatic cancer cells, the regulatory mechanisms and significance in HCC are still to be fully elucidated. Our study shows that knockdown (KD) of YEATS2 expression leads to DNA damage, which in turn results in an upregulation of γ-H2A.X expression and activation of the canonical senescence-related pathway p53/p21Cip1. Moreover, our transcriptomic analysis reveals that YEATS2 KD cells can enhance the expression of p21Cip1 via the c-Myc/miR-93-5p pathway, consequently fostering the senescence of HCC cells. The initiation of cellular senescence through dual-channel activation suggests that YEATS2 plays a pivotal regulatory role in the process of cell proliferation. Ultimately, our in vivo research utilizing a nude mouse tumor model revealed a notable decrease in both tumor volume and weight after the suppression of YEATS2 expression. This phenomenon is likely attributable to the attenuation of proliferative cell activity, coupled with a concurrent augmentation in the population of natural killer (NK) cells. In summary, our research results have supplemented the understanding of the regulatory mechanisms of HCC cell proliferation and indicated that targeting YEATS2 may potentially inhibit liver tumor growth.

RING box protein-1(RBX1), a key component of SCF E3 ligase, induced multiple myeloma cell drug-resistance though suppressing p27

Multiple myeloma (MM) is a clonal disease of plasma cells that remains, for the most part, incurable despite the advent of several novel therapeutics. The elevated expression of p27 and its association with cell-cycle arrest is speculated to be one of the major mechanisms by which MM cells escape the cytotoxic effects of therapeutic agents. In this study, we demonstrated that RBX1 silencing could inhibit MM cell growth and promote cell drug resistance. RBX1 directly interacted with and triggered the ubiquitination and degradation of p27, ultimately causing p27 reduction. Additionally, cell growth and apoptosis analysis indicated that the role of RBX1 in regulating myeloma cell proliferation and drug resistance resulted from p27 accumulation, which occurred in a Thr187 phosphorylation-dependent manner. Furthermore, the cell-cycle analysis demonstrated that RBX1 overexpression induced cells to enter the cell cycle (S-phase) and partially inhibited chemotherapeutic drugs-mediated cell cycle arrest. Notably, the forced expression of RBX1 also inhibited the cell adhesion-mediated elevation of p27 and induced the accumulation of adherent cells in apoptosis, especially the proteolytic cleavage of caspase-3. Additionally, RBX1 knockdown significantly inhibited myeloma development in SCID-Hu mice and in a human MM xenotransplant model. Overall, these in vitro and in vivo experiments indicated that the RBX1-p27 axis could be a central molecular mechanism by which RBX1 functions as a tumor promoter and stimulates cell growth in chemotherapeutic drugs treated MM cells.

Targeting cullin neddylation for cancer and fibrotic diseases

Protein neddylation is a post-translational modification, and its best recognized substrates are cullin family proteins, which are the core component of Cullin-RING ligases (CRLs). Given that most neddylation pathway proteins are overactivated in different cancers and fibrotic diseases, targeting neddylation becomes an emerging approach for the treatment of these diseases. To date, numerous neddylation inhibitors have been developed, of which MLN4924 has entered phase I/II/III clinical trials for cancer treatment, such as acute myeloid leukemia, melanoma, lymphoma and solid tumors. Here, we systematically describe the structures and biological functions of the critical enzymes in neddylation, highlight the medicinal chemistry advances in the development of neddylation inhibitors and propose the perspectives concerning targeting neddylation for cancer and fibrotic diseases.

Deneddylating enzyme SENP8 regulates neuronal development

Neddylation is a cellular process in which the neural precursor cell expressed, developmentally down-regulated 8 (NEDD8) is conjugated to the lysine residue of target proteins via serial enzymatic cascades. Recently, it has been demonstrated that neddylation is required for synaptic clustering of metabotropic glutamate receptor 7 (mGlu7) and postsynaptic density protein 95 (PSD-95), and the inhibition of neddylation impairs neurite outgrowth and excitatory synaptic maturation. Similar to the balanced role of deubiquitylating enzymes (DUBs) in the ubiquitination process, we hypothesized that deneddylating enzymes can regulate neuronal development by counteracting the process of neddylation. We find that the SUMO peptidase family member, NEDD8 specific (SENP8) acts as a key neuronal deneddylase targeting the global neuronal substrates in primary rat cultured neurons. We demonstrate that SENP8 expression levels are developmentally regulated, peaking around the first postnatal week and gradually diminishing in mature brain and neurons. We find that SENP8 negatively regulates neurite outgrowth through multiple pathways, including actin dynamics, Wnt/β-catenin signaling, and autophagic processes. Alterations in neurite outgrowth by SENP8 subsequently result in the impairment of excitatory synapse maturation. Our data indicate that SENP8 plays an essential role in neuronal development and is a promising therapeutic target for neurodevelopmental disorders.

Clinicopathological and prognostic role of ROC1 in neoplasms: A PRISMA-compliant systematic review and meta-analysis

BACKGROUND

Regulator of cullins 1 (ROC1) is frequently overexpressed in multiple tumors, and many pieces of research demonstrate that ROC1 is associated with the prognosis and development of a diversity of neoplasms and it is able to serve as a promising prognostic biomarker. Here we performed this meta-analysis to evaluate the prognostic and clinicopathological significance of ROC1 in patients suffering from cancer.

METHODS

We searched Pubmed, Embase, Web of Science, Chinese National Knowledge Infrastructure (CNKI), and WanFang database. The role of ROC1 in cancers was evaluated by pooled hazard ratios (HRs), odd ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

In total, 9 studies including 1002 patients were enrolled in this analysis. The pooled results showed that patients with high expression of ROC1 had poor overall survival (OS) (HR: 2.04, 95% CI: 1.48-2.60, P < 0.001) and recurrence-free survival (RFS) (HR: 1.727, 95% CI: 0.965-2.488, P < 0.001). Additionally, elevated expression of ROC1 was significantly correlated with advanced clinical Tumor Node Metastasis stage (OR: 2.708, 95% CI: 1.856-3.951, P < 0.001), positive lymph node metastasis (OR: 1.968; 95% CI: 1.294-2.993, P = .002), large tumor size (OR: 1.522, 95% CI: 1.079-2.149, P = .017) and poor tumor differentiation (OR: 2.448, 95% CI: 1.793-3.344, P < 0.001).

CONCLUSIONS

Elevated ROC1 expression predicted worse prognosis and advanced pathological parameters in various cancers. ROC1 was a significant prognostic biomarker for poor survival in human cancers.

Genetic and Epigenetic Mechanisms Deregulate the CRL2pVHL Complex in Hepatocellular Carcinoma

Dysregulation of ubiquitin-proteasome pathway genes through copy number alteration, promoter hypomethylation, and miRNA deregulation is involved in cancer development and progression. Further characterizing alterations in these genes may uncover novel drug targets across a range of diseases in which druggable alterations are uncommon, including hepatocellular carcinoma (HCC). We analyzed 377 HCC and 59 adjacent non-malignant liver tissue samples, focusing on alterations to component genes of the widely studied CRL2^pVHL E3 ubiquitin ligase complex. mRNA upregulation of the component genes was common, and was correlated with DNA hypomethylation and copy number increase, but many tumours displayed overexpression that was not explained by either mechanism. Interestingly, we found 66 miRNAs, including 39 previously unannotated miRNAs, that were downregulated in HCC and predicted to target one or more CRL2^pVHL components. Several miRNAs, including hsa-miR-101-3p and hsa-miR-139-5p, were negatively correlated with multiple component genes, suggesting that miRNA deregulation may contribute to CRL2^pVHL overexpression. Combining miRNA and mRNA expression, DNA copy number, and methylation status into one multidimensional survival analysis, we found a significant association between greater numbers of alterations and poorer overall survival for multiple component genes. While the intricacies of CRL2^pVHL complex gene regulation require additional research, it is evident that multiple causes for the deregulation of these genes must be considered in HCC, including non-traditional mechanisms.

RNF4 silencing induces cell growth arrest and DNA damage by promoting nuclear targeting of p62 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the largest causes of cancer-related deaths worldwide owing to the limitation of effective treatment options. The ubiquitin-proteasome system has been rapidly recognized as a frequent target of deregulation leading to cancers. Enhanced DNA damage response (DDR) promotes HCC growth and prevents chemosensitivity, and ubiquitin E3 ligases are key modulators in DDR. Therefore, a better understanding of how E3 ligases regulate cell growth and DNA damage may provide novel insights in understanding the oncogenic mechanism and improving the efficacy of DNA damage therapeutic agents. Here, we performed a high-content RNAi screening targeting 52 DDR-related E3 ligases in HCC and found that ring finger protein 4 (RNF4) was essential for HCC growth. RNF4 was highly expressed in HCC tissues, and the expression levels of RNF4 were associated with poor outcomes. RNF4 silencing significantly suppressed the cell growth, and subsequently induced G2/M arrest and apoptosis of HCC cells in vitro; RNF4 silencing also demonstrated the tumor-suppressive efficacy on HCC in vivo. Moreover, RNF4 silencing increased DNA damage, and rendered HCC cells more sensitive to DNA damage drugs and radiation. We found RNF4 functionally interacts with p62, and mechanistic analyses indicated that RNF4 silencing triggered the nuclear enrichment of p62. Moreover, the p62 nuclear targeting was required for increased DNA damage and growth suppression mediated by RNF4 silencing. Thus, our findings suggest RNF4 is essential for HCC proliferation via preventing nuclear translocation of p62. RNF4 silencing promotes DNA damage and may serve as a novel strategy to suppress cell growth and increase the sensitivity of DNA damage therapeutic agents in HCC.

Long non-coding RNA DDX11-AS1 promotes esophageal carcinoma cell proliferation and migration through regulating the miR-514b-3p/RBX1 axis

Esophageal carcinoma (ESCA) is one of the most aggressive malignancies with extremely high morbidity and mortality. At present, limited advancement in ESCA treatment has achieved. Therefore, it is urgent to explore the pathogenesis and progression mechanism of ESCA to provide the basis for the formulation of novel therapeutic strategies. Previous studies have found that long non-coding RNA (lncRNA) DDX11-AS1 expression enhances the paclitaxel resistance of ESCA cells. However, the mechanisms underlying the drug resistance conferred by lncRNA DDX11-AS1 in ESCA remains to be elucidated. Our research aims to clarify the role and mechanism of lncRNA DDX11-AS1 in regulating the progression of ESCA. We found that the expression of lncRNA DDX11-AS1 in ESCA tissues and cell lines was significantly upregulated. Subsequently, silencing lncRNA DDX11-AS1 significantly inhibited the proliferation, migration and invasion of ESCA cells, and induced the level of cell apoptosis. In terms of mechanism, our data showed that miR-514b-3p/RING box protein 1 (RBX1) axis played a crucial role in the oncogenic function of lncRNA DDX11-AS1. LncRNA DDX11-AS1 expression impaired the inhibitory function of miR-514b-3p on RBX1 through sponging effect. Taken together, our data support the notion that lncRNA DDX11-AS1 promotes the progression of ESCA through miR-514b-3p/RBX1 axis. Our research uncovers the novel regulatory role of lncRNA DDX11-AS1 in ESCA and lays a theoretical basis for developing novel treatment strategy of ESCA.

ROC1 promotes the malignant progression of bladder cancer by regulating p-IκBα/NF-κB signaling

Background

Regulator of cullins 1 (ROC1) is an important catalytic subunit of cullin–RING E3 ligase. Nuclear factor-kappa B (NF-κB) signaling is closely related to tumor invasion and metastasis. Earlier, we reported that ROC1 was associated with a poor prognosis in patients with bladder cancer (BCa). However, it is unclear whether ROC1 is involved in the NF-κB signaling associated with malignant BCa progression.

Methods

The expression of ROC1 and p65 in bladder cancer and paracancerous tissues were detected by immunohistochemistry (IHC). Pearson correlation was used to assess correlation between ROC1 and p65 protein expressions. The wound-healing and transwell assays were used to monitor cell invasion and migration. The effect of ROC1 on the expression of key proteins in the NF-κB signaling was determined by immunofluorescence and western blot (WB). Cycloheximide (CHX), MG132 and immunoprecipitation assays were used to evaluate the effect of ROC1 on the ubiquitination of phosphorylated inhibitor of kappa B alpha (p-IκBα). A lung metastasis mouse model was generated to detect the role of ROC1 in tumor metastasis.

Results

We found that ROC1 was up-regulated in BCa tissues and cell lines, and high ROC1 levels were positively correlated with higher tumour grade, lymph node metastasis, distant metastasis and poor prognosis. Linear-regression analysis showed significant a Pearson correlation between ROC1 and nuclear p65 expression in BCa tissue microarray (TMA) samples. Functional studies demonstrated that ROC1 promoted BCa cell invasion and migration. In vitro and in vivo experiments showed that ROC1 activated NF-κB signaling by enhancing the ubiquitination of p-IκBα, which caused p65 nuclear translocation and promoted the transcription of some metastasis-related target genes, such as urokinase-type plasminogen activator receptor (uPAR), intracellular adhesion molecule 1 (ICAM1), vascular cell adhesion molecule 1 (VCAM1), and matrix metalloproteinase 9 (MMP9), resulting in promoting BCa metastasis.

Conclusion

ROC1 plays an important role in the progression of BCa and serves as a potential diagnostic and therapeutic target for patients with BCa.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01935-5.

A Destiny for Degradation: Interplay between Cullin-RING E3 Ligases and Autophagy

Autophagy and the ubiquitin-proteasome system (UPS) are two major pathways for protein degradation. The cullin-RING E3 ligases (CRLs) are the largest E3 ligase family and have key biological functions in maintaining protein homeostasis. We provide an updated review of the interactions between CRLs and autophagy, focusing on the regulatory effects of CRLs on the core autophagy machinery that consists of several autophagy-related protein (ATG) complexes and their key upstream signaling pathways. The involvement of such functional interactions in health and disease is also discussed. Understanding the role of CRLs in autophagy is helpful for the development of therapeutic strategies for diseases in which CRLs and autophagy are dysregulated, such as cancer and neurodegenerative conditions.

Tumor-associated antigen Prame targets tumor suppressor p14/ARF for degradation as the receptor protein of CRL2Prame complex

Protein Preferentially Expressed Antigen in Melanoma (Prame), a tumor-associated antigen, has been found to frequently overexpress in various cancers, which indicates advanced cancer stages and poor clinical prognosis. Moreover, previous reports noted that Prame functions as a substrate recognizing receptor protein of Cullin RING E3 ligases (CRLs) to mediate potential substrates degradation through Ubiquitin Proteasome System (UPS). However, none of the Prame specific substrate has been identified so far. In this study, proteomic analysis of RBX1-interacting proteins revealed p14/ARF, a well-known tumor suppressor, as a novel ubiquitin target of RBX1. Subsequently, immunoprecipitation and in vivo ubiquitination assay determined Cullin2-RBX1-Transcription Elongation Factor B Subunit 2 (EloB) assembled CRL2 E3 ligase complex to regulate the ubiquitination and subsequent degradation of p14/ARF. Finally, through siRNA screening, Prame was identified as the specific receptor protein responsible for recognizing p14/ARF to be degraded. Additionally, via bioinformatics analysis of TCGA database and clinical samples, Prame was determined to overexpress in tumor tissues vs. paired adjacent tissues and associated with poor prognosis of cancer patients. As such, downregulation of Prame expression significantly restrained cancer cell growth by inducing G2/M phase cell cycle arrest, which could be rescued by simultaneously knocking down of p14/ARF. Altogether, targeting overexpressed Prame in cancer cells inactivated RBX1-Cullin2-EloB-Prame E3 ligase (CRL2^Prame) and halted p14/ARF degradation to restrain tumor growth by inducing G2/M phase cell cycle arrest.

Autophagy in liver diseases

Autophagy is the liver cell energy recycling system regulating a variety of homeostatic mechanisms. Damaged organelles, lipids and proteins are degraded in the lysosomes and their elements are re-used by the cell. Investigations on autophagy have led to the award of two Nobel Prizes and a health of important reports. In this review we describe the fundamental functions of autophagy in the liver including new data on the regulation of autophagy. Moreover we emphasize the fact that autophagy acts like a two edge sword in many occasions with the most prominent paradigm being its involvement in the initiation and progress of hepatocellular carcinoma. We also focused to the implication of autophagy and its specialized forms of lipophagy and mitophagy in the pathogenesis of various liver diseases. We analyzed autophagy not only in well studied diseases, like alcoholic and nonalcoholic fatty liver and liver fibrosis but also in viral hepatitis, biliary diseases, autoimmune hepatitis and rare diseases including inherited metabolic diseases and also acetaminophene hepatotoxicity. We also stressed the different consequences that activation or impairment of autophagy may have in hepatocytes as opposed to Kupffer cells, sinusoidal endothelial cells or hepatic stellate cells. Finally, we analyzed the limited clinical data compared to the extensive experimental evidence and the possible future therapeutic interventions based on autophagy manipulation.

Regulator of cullins-1 (ROC1) negatively regulates the Gli2 regulator SUFU to activate the hedgehog pathway in bladder cancer

BACKGROUND

The regulator of cullins-1 (ROC1) is an essential subunit in the cullin-RING ligase (CRL) protein complex and has been shown to be critical in bladder cancer cell survival and progression. This study aimed to explore the molecular mechanism of ROC1 action in the malignant progression of bladder cancer.

METHODS

This study utilized ex vivo, in vitro, and in vivo nude mouse experiments to assess the underlying mechanisms of ROC1 in bladder cancer cells. The expression of the components of the sonic hedgehog (SHH) pathway was determined by western blot analysis. ROC1 expression in human tumors was evaluated by immunohistochemistry.

RESULTS

ROC1 overexpression promoted the growth of bladder cancer cells, whereas knockdown of ROC1 expression had the opposite effect in bladder cancer cells. Mechanistically, ROC1 was able to target suppressor of fused homolog (SUFU) for ubiquitin-dependent degradation, allowing Gli2 release from the SUFU complex to activate the SHH pathway. Furthermore, knockdown of SUFU expression partially rescued the ROC1 knockdown-suppressed SHH activity as well as cancer cell growth inhibition. In ex vivo experiments, tissue microarray analysis of human bladder cancer specimens revealed a positive association of ROC1 expression with the SHH pathway activity.

CONCLUSION

This study demonstrated that dysregulation of the ROC1-SUFU-GLI2 axis plays an important role in bladder cancer progression and that targeting ROC1 expression is warranted in further investigations as a novel strategy for the future control of bladder cancer.

Cellular Senescence in Liver Disease and Regeneration

Cellular senescence is an irreversible cell cycle arrest implemented by the cell as a result of stressful insults. Characterized by phenotypic alterations, including secretome changes and genomic instability, senescence is capable of exerting both detrimental and beneficial processes. Accumulating evidence has shown that cellular senescence plays a relevant role in the occurrence and development of liver disease, as a mechanism to contain damage and promote regeneration, but also characterizing the onset and correlating with the extent of damage. The evidence of senescent mechanisms acting on the cell populations of the liver will be described including the role of markers to detect cellular senescence. Overall, this review intends to summarize the role of senescence in liver homeostasis, injury, disease, and regeneration.

Reduced RBX1 expression induces chromosome instability and promotes cellular transformation in high-grade serous ovarian cancer precursor cells

Despite high-grade serous ovarian cancer (HGSOC) being the most common and lethal gynecological cancer in women, the early etiological events driving disease development remain largely unknown. Emerging evidence now suggests that chromosome instability (CIN; ongoing changes in chromosome numbers) may play a central role in the development and progression of HGSOC. Importantly, genomic amplification of the Cyclin E1 gene (CCNE1) contributes to HGSOC pathogenesis in ~20% of patients, while Cyclin E1 overexpression induces CIN in model systems. Cyclin E1 levels are normally regulated by the SCF (SKP1-CUL1-FBOX) complex, an E3 ubiquitin ligase that includes RBX1 as a core component. Interestingly, RBX1 is heterozygously lost in ~80% of HGSOC cases and reduced expression corresponds with worse outcomes, suggesting it may be a pathogenic event. Using both short (siRNA) and long (CRISPR/Cas9) term approaches, we show that reduced RBX1 expression corresponds with significant increases in CIN phenotypes in fallopian tube secretory epithelial cells, a cellular precursor of HGSOC. Moreover, reduced RBX1 expression corresponds with increased Cyclin E1 levels and anchorage-independent growth. Collectively, these data identify RBX1 as a novel CIN gene with pathogenic implications for HGSOC.

The functional analysis of Cullin 7 E3 ubiquitin ligases in cancer

Cullin (CUL) proteins have critical roles in development and cancer, however few studies on CUL7 have been reported due to its characteristic molecular structure. CUL7 forms a complex with the ROC1 ring finger protein, and only two F-box proteins Fbxw8 and Fbxw11 have been shown to bind to CUL7. Interestingly, CUL7 can interact with its substrates by forming a novel complex that is independent of these two F-box proteins. The biological implications of CUL-ring ligase 7 (CRL7) suggest that the CRL7 may not only perform a proteolytic function but may also play a non-proteolytic role. Among the existing studied CRL7-based E3 ligases, CUL7 exerts both tumor promotion and suppression in a context-dependent manner. Currently, the mechanism of CUL7 in cancer remains unclear, and no studies have addressed potential therapies targeting CUL7. Consistent with the roles of the various CRL7 adaptors exhibit, targeting CRL7 might be an effective strategy for cancer prevention and treatment. We systematically describe the recent major advances in understanding the role of the CUL7 E3 ligase in cancer and further summarize its potential use in clinical therapy.

Ring box protein-1 is associated with a poor prognosis and tumor progression in esophageal cancer

Ring box protein-1 (RBX1) is an essential component of the S-phase kinase-associated protein, Cullin and F-box containing ubiquitin ligases. Overexpression of RBX1 has been reported in several cancer types; however, little is known regarding the prognostic value and role of RBX1 in esophageal cancer. The present study examined 120 patients with esophageal cancer (EC) who underwent curative esophagectomy and 61 patients with EC who underwent neoadjuvant combination chemotherapy with docetaxel, cisplatin and 5-fluorouracil (5-FU; DCF) using immunohistochemistry. All specimens were classified into two groups according to the percentage of RBX1-positive tumor cells. In addition, the impact of RBX1 expression on cancer cell proliferation was analyzed in vitro using a small interfering RNA silencing technique. RBX1 expression levels showed significant differences according to tumor size (P<0.001), tumor depth (P=0.002), lymph node metastasis (P=0.004), pathological stage (P=0.001), lymphatic invasion (P=0.001) and venous invasion (P=0.001). The overall survival (OS) rate in the RBX1 high expression group was significantly lower compared with that in the low group (P=0.004). Multivariate analysis demonstrated that RBX1 status was an independent prognostic factor. RBX1 gene silencing inhibited the proliferation of human EC cells and enhanced the antitumor effect of 5-FU. Among patients who underwent neoadjuvant DCF therapy, the RBX1 high expression group had a significantly lower OS rate compared with that of the RBX1-low group (P<0.001). In conclusion, RBX1 has notable prognostic value, and RBX1 may serve an important function in the tumor progression of EC.

Neddylation inhibition activates the protective autophagy through NF-κB-catalase-ATF3 Axis in human esophageal cancer cells

Background

Protein neddylation plays a tumor-promoting role in esophageal cancer. Our previous study demonstrated that neddylation inhibition induced the accumulation of ATF4 to promote apoptosis in esophageal cancer cells. However, it is completely unknown whether neddylation inhibition could induce autophagy in esophageal cancer cells and affect the expression of other members of ATF/CREB subfamily, such as ATF3.

Methods

The expression of relevant proteins of NF-κB/Catalase/ATF3 pathway after neddylation inhibition was determined by immunoblotting analysis and downregulated by siRNA silencing for mechanistic studies. ROS generation upon MLN4924 treatment was determined by H2-DCFDA staining. The proliferation inhibition induced by MLN4924 was evaluated by ATPLite assay and apoptosis was evaluated by Annexin V /PI double staining.

Results

For the first time, we reported that MLN4924, a specific inhibitor of Nedd8-activating enzyme, promoted the expression of ATF3 to induce autophagy in esophageal cancer. Mechanistically, MLN4924 inhibited the activity of CRLs and induced the accumulation of its substrate IκBα to block NF-κB activation and Catalase expression. As a result, MLN4924 activated ATF3-induced protective autophagy, thereby inhibiting MLN4924-induced apoptosis, which could be alleviated by ATF3 silencing.

Conclusions

In our study, we elucidates a novel mechanism of NF-κB/Catalase/ATF3 pathway in MLN4924-induced protective autophagy in esophageal cancer cells, which provides a sound rationale and molecular basis for combinational anti-ESCC therapy with knockdown ATF3 and neddylation inhibitor (e.g. MLN4924).

The CRL3BTBD9 E3 ubiquitin ligase complex targets TNFAIP1 for degradation to suppress cancer cell migration

Tumor necrosis factor alpha-induced protein 1 (TNFAIP1) modulates a plethora of important biological processes, including tumorigenesis and cancer cell migration. However, the regulatory mechanism of TNFAIP1 degradation remains largely elusive. In the present study, with a label-free quantitative proteomic approach, TNFAIP1 was identified as a novel ubiquitin target of the Cullin-RING E3 ubiquitin ligase (CRL) complex. More importantly, Cul3-ROC1 (CRL3), a subfamily of CRLs, was identified to specifically interact with TNFAIP1 and promote its polyubiquitination and degradation. Mechanistically, BTBD9, a specific adaptor component of CRL3 complex, was further defined to bind and promote the ubiquitination and degradation of TNFAIP1 in cells. As such, downregulation of BTBD9 promoted lung cancer cell migration by upregulating the expression of TNFAIP1, whereas TNFAIP1 deletion abrogated this effect. Finally, bioinformatics and clinical sample analyses revealed that BTBD9 was downregulated while TNFAIP1 was overexpressed in human lung cancer, which was associated with poor overall survival of patients. Taken together, these findings reveal a previously unrecognized mechanism by which the CRL3^BTBD9 ubiquitin ligase controls TNFAIP1 degradation to regulate cancer cell migration.

Autophagy compensates for defects in mitochondrial dynamics

Compromising mitochondrial fusion or fission disrupts cellular homeostasis; however, the underlying mechanism(s) are not fully understood. The loss of C. elegans fzo-1MFN results in mitochondrial fragmentation, decreased mitochondrial membrane potential and the induction of the mitochondrial unfolded protein response (UPRmt). We performed a genome-wide RNAi screen for genes that when knocked-down suppress fzo-1MFN(lf)-induced UPRmt. Of the 299 genes identified, 143 encode negative regulators of autophagy, many of which have previously not been implicated in this cellular quality control mechanism. We present evidence that increased autophagic flux suppresses fzo-1MFN(lf)-induced UPRmt by increasing mitochondrial membrane potential rather than restoring mitochondrial morphology. Furthermore, we demonstrate that increased autophagic flux also suppresses UPRmt induction in response to a block in mitochondrial fission, but not in response to the loss of spg-7AFG3L2, which encodes a mitochondrial metalloprotease. Finally, we found that blocking mitochondrial fusion or fission leads to increased levels of certain types of triacylglycerols and that this is at least partially reverted by the induction of autophagy. We propose that the breakdown of these triacylglycerols through autophagy leads to elevated metabolic activity, thereby increasing mitochondrial membrane potential and restoring mitochondrial and cellular homeostasis.

Targeting Protein Neddylation for Cancer Therapy

Neddylation is a posttranslational modification that conjugates a ubiquitin-like protein NEDD8 to substrate proteins. The best-characterized substrates of neddylation are the cullin subunits of cullin-RING E3 ubiquitin ligase complexes (CRLs). CRLs as the largest family of E3 ubiquitin ligases control many important biological processes, including tumorigenesis, through promoting ubiquitylation and subsequent degradation of a variety of key regulatory proteins. The process of protein neddylation is overactivated in multiple types of human cancers, providing a sound rationale as an attractive anticancer therapeutic strategy, evidenced by the development of the NEDD8-activating enzyme (NAE) inhibitor MLN4924 (also known as pevonedistat). Recently, increasing evidence strongly indicates that neddylation inhibition by MLN4924 exerts anticancer effects mainly by triggering cell apoptosis, senescence, and autophagy and causing angiogenesis suppression, inflammatory responses, and chemo-/radiosensitization in a context-dependent manner. Here, we briefly summarize the latest progresses in this field, focusing on the preclinical studies to validate neddylation modification as a promising anticancer target.

Expression of Ring Box-1 protein and its relationship with Fuhrman grade and other clinical-pathological parameters in renal cell cancer

OBJECTIVE

To determine the relationship between RING-box protein 1 (RBX-1) expression and renal cell carcinoma (RCC) with prognostic factors.

METHODS

A total of 88 patients who underwent radical/partial nephrectomy between January 2009 and January 2016 have been included in our study. The age, gender, tumor location, tumor size, and tumor-node-metastasis stage of each patient was evaluated. From the best sections in hematoxylin-eosin stained pathology preparations, tumor histological subtype, Fuhrman nuclear grade, lymphovascular invasion, renal artery/vein invasion, capsule invasion, perirenal fatty tissue invasion, and tumor grade were evaluated. Participants were divided into 2 groups according to Fuhrman grade. Fuhrman grades 1 to 2 comprised Group 1, and Fuhrman grades 3 to 4 comprised Group 2. An immunoreactivity scoring system was used to evaluate RBX-1 expression.

RESULTS

Upon examining all histological subtypes together, it was observed that RBX-1 expression was statistically higher in Group 2 compared to Group 1 (P < 0.008). Upon examining clear RCC cases, it was observed again that Group 2 had a higher RBX-1 expression than Group 1 (P < 0.009). RBX-1 expression was not associated with clinical-pathological parameters including tumor grade, lymphovascular invasion, capsule invasion, or perirenal invasion.

CONCLUSION

RBX-1 expression is closely associated with a highly important prognostic factor in RCC-Fuhrman grade-and it shows promise as a prognostic marker. Further studies are required to reveal the importance of RBX-1 in RCC prognosis and treatment.

Augmenting the therapeutic efficacy of adenosine against pancreatic cancer by switching the Akt/p21-dependent senescence to apoptosis

Background

There are many reports of the anti-tumour effects of exogenous adenosine in gastrointestinal tumours. Gemcitabine, a first line agent for patients with poor performance status, and adenosine have structural similarities. For these reasons, it is worth exploring the therapeutic efficacy of adenosine and its underlying mechanism in pancreatic cancer.

Methods

Tumour volumes and survival periods were measured in a patient-derived xenograft (PDX) model of pancreatic cancer. The Akt-p21 signalling axis was blocked by p21 silencing or by the Akt inhibitor GSK690693. The combined effect of GSK690693 and adenosine was calculated by the Chou-Talalay equation and verified by measuring fluorescent areas in orthotopic models.

Findings

Among the PDX mice, the tumour volume in the adenosine treatment group was only 61% of that in the saline treatment group. Adenosine treatment in combination with the Akt inhibitor, GSK690693, or the silencing of p21 to interfere with the Akt-p21 axis can switch the senescence-to-apoptosis signal and alleviate drug resistance. A GSK690693-adenosine combination caused 37.4% further reduction of tumour fluorescent areas in orthotopic models compared with that observed in adenosine monotherapy.

Interpretation: Our data confirmed the therapeutic effect of adenosine on pancreatic cancer, and revealed the potential of Akt inhibitors as sensitization agents in this treatment.

Fund

The work is supported by grants from the National Natural Science Foundation of China to Dongqin Yang (81572336, 81770579) and Jie Liu (81630016, 81830080), and jointly by the Development Fund for Shanghai Talents (201660).

Validation of NEDD8-conjugating enzyme UBC12 as a new therapeutic target in lung cancer

Background

The neddylation pathway is overactivated in human cancers. Inhibition of neddylation pathway has emerged as an attractive anticancer strategy. The mechanisms underlying neddylation overactivation in cancer remain elusive. MLN4924/Pevonedistat, a first-in-class NEDD8-activating enzyme (NAE, E1) inhibitor, exerts significant anti-tumor effects, but its mutagenic resistance remains unresolved.

Methods

The expression of NEDD8-conjugating enzyme UBC12/UBE2M (E2) and NEDD8 were estimated by bioinformatics analysis and western blot in human lung cancer cell lines. The malignant phenotypes of lung cancer cells were evaluated both in vitro and in vivo upon UBC12 knockdown. Cell-cycle arrest was evaluated by quantitative proteomic analysis and propidium iodide stain and fluorescence - activated cell sorting (FACS). The growth of MLN4924 - resistant H1299 cells was also evaluated upon UBC12 knockdown.

Findings

The mRNA level of UBC12 in lung cancer tissues was much higher than that in normal lung tissues, increased with disease deterioration, and positively correlated with NEDD8 expression. Moreover, the overexpression of UBC12 significantly enhanced protein neddylation modification whereas the downregulation of UBC12 reduced neddylation modification of target proteins. Functionally, neddylation inactivation by UBC12 knockdown suppressed the malignant phenotypes of lung cancer cells both in vitro and in vivo. The quantitative proteomic analysis and cell cycle profiling showed that UBC12 knockdown disturbed cell cycle progression by triggering G₂ phase cell-cycle arrest. Further mechanistical studies revealed that UBC12 knockdown inhibited Cullin neddylation, led to the inactivation of CRL E3 ligases and induced the accumulation of tumor-suppressive CRL substrates (p21, p27 and Wee1) to induce cell cycle arrest and suppress the malignant phenotypes of lung cancer cells. Finally, UBC12 knockdown effectively inhibited the growth of MLN4924-resistant lung cancer cells.

Interpretation

These findings highlight a crucial role of UBC12 in fine-tuned regulation of neddylation activation status and validate UBC12 as an attractive alternative anticancer target against neddylation pathway.

Fund

Chinese Minister of Science and Technology grant (2016YFA0501800), National Natural Science Foundation of China (Grant Nos. 81401893, 81625018, 81820108022, 81772470, 81572340 and 81602072), Innovation Program of Shanghai Municipal Education Commission (2019-01-07-00-10-E00056), Program of Shanghai Academic/Technology Research Leader (18XD1403800), National Thirteenth Five-Year Science and Technology Major Special Project for New Drug and Development (2017ZX09304001). The funders had no role in study design, data collection, data analysis, interpretation, writing of the report.

Inactivation of SAG or ROC1 E3 Ligase Inhibits Growth and Survival of Renal Cell Carcinoma Cells: Effect of BIM

SAG (Sensitive to Apoptosis Gene) and ROC1 (Regulator of Cullin-1) are two family members of the RING component of CRL (Cullin RING ligase). Both members are essential for growth and survival of several types of human cancer cells; their role in renal cell carcinoma (RCC), however, remains elusive. Here we reported that compared to adjacent normal tissues, both SAG and ROC1 are overexpressed in RCC, which is positively correlated with poor patient survival, particularly for SAG. Depletion of SAG or ROC1 inhibited growth and survival of RCC cells by inducing G2/M arrest, senescence, and apoptosis likely due to accumulation of WEE1, p21, p27, NOXA, and BIM. Interestingly, simultaneous BIM knockdown in RCC cells partially rescues growth suppression triggered by depletion of SAG, but not ROC1, suggesting a differential role of BIM. Collectively, our study provides the proof-of-concept evidence that RING components of CRL are attractive candidates for targeted therapy of RCC.

Alzheimer's Disease and Cancer: When Two Monsters Cannot Be Together

Alzheimer's disease (AD) and cancer are among the leading causes of human death around the world. While neurodegeneration is the main feature of AD, the most important characteristic of malignant tumors is cell proliferation, placing these two diseases in opposite sides of cell division spectrum. Interestingly, AD and cancer's pathologies consist of a remarkable common feature and that is the presence of active cell cycle in both conditions. In an in vitro model of primary adult neuronal culture, we previously showed that treating cell with beta amyloid forced neurons to start a cell cycle. Instead of cell division, however, neuronal cell cycle was aborted and a massive neurodegeneration was left behind as the consequence. A high level of cell cycle entry, which is a requirement for cancer pathogenesis, was reported in clinically diagnosed cases of AD, leading to neurodegeneration. The diverse clinical manifestation of a similar etiology, have puzzled researchers for many years. In fact, the evidence showed an inverse association between AD and cancer prevalence, suggesting that switching pathogenesis toward AD protects patients against cancer and vice versa. In this mini review, we discussed the possibility of involvement of cell proliferation and survival dysregulation as the underlying mechanism of neurodegeneration in AD, and the leading event to develop both disorders' pathology. As examples, the role of phosphoinositide 3 kinase/Akt/ mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway in cell cycle re-entry and blocking autophagy are discussed as potential common intracellular components between AD and cancer pathogenesis, with diverse clinical diagnosis.

Diverse Functions of Autophagy in Liver Physiology and Liver Diseases

Autophagy is a catabolic process by which eukaryotic cells eliminate cytosolic materials through vacuole-mediated sequestration and subsequent delivery to lysosomes for degradation, thus maintaining cellular homeostasis and the integrity of organelles. Autophagy has emerged as playing a critical role in the regulation of liver physiology and the balancing of liver metabolism. Conversely, numerous recent studies have indicated that autophagy may disease-dependently participate in the pathogenesis of liver diseases, such as liver hepatitis, steatosis, fibrosis, cirrhosis, and hepatocellular carcinoma. This review summarizes the current knowledge on the functions of autophagy in hepatic metabolism and the contribution of autophagy to the pathophysiology of liver-related diseases. Moreover, the impacts of autophagy modulation on the amelioration of the development and progression of liver diseases are also discussed.

DEPTOR at the Nexus of Cancer, Metabolism, and Immunity

DEP domain-containing mechanistic target of rapamycin (mTOR)-interacting protein (DEPTOR) is an important modulator of mTOR, a kinase at the center of two important protein complexes named mTORC1 and mTORC2. These highly studied complexes play essential roles in regulating growth, metabolism, and immunity in response to mitogens, nutrients, and cytokines. Defects in mTOR signaling have been associated with the development of many diseases, including cancer and diabetes, and approaches aiming at modulating mTOR activity are envisioned as an attractive strategy to improve human health. DEPTOR interaction with mTOR represses its kinase activity and rewires the mTOR signaling pathway. Over the last years, several studies have revealed key roles for DEPTOR in numerous biological and pathological processes. Here, we provide the current state of the knowledge regarding the cellular and physiological functions of DEPTOR by focusing on its impact on the mTOR pathway and its role in promoting health and disease.

Targeting CAND1 promotes caspase-8/RIP1-dependent apoptosis in liver cancer cells

Cullin-associated NEDD8-dissociated 1 (CAND1) plays a vital role in regulating the activity of Cullin-RING ubiquitin ligases (CRLs), which are frequently dysregulated in cancer. However, the role of CAND1 in hepatocellular carcinoma (HCC) remains unknown. Here, we found that CAND1 was overexpressed in HCC tissues compared to corresponding adjacent liver tissues (71.7% vs 16.7%); high expression of CAND1 was associated with poor overall survival (40.7 vs 57.3 months, P=0.0013); and CAND1 was an independent risk factor for the prognosis of HCC patients (N=138, P=0.018). Functional studies revealed that CAND1 knockdown efficiently suppressed the proliferation of liver cancer cells by activating caspase-8-dependent mitochondrial apoptosis. We also observed a mutual activation loop between caspase-8 and Receptor Interacting Protein 1 (RIP1), which amplified CAND1 knockdown-induced apoptotic signals in the cells. Furthermore, RIP1 inhibitor Necrostatin-1 eliminated the activation of caspase-8. In conclusion, our study pioneered in reporting high CAND1 expression as a predictor of poor prognosis for HCC patients. CAND1 silencing suppressed HCC cell proliferation by inducing caspase-8/RIP1-dependent apoptosis. These findings supported that CAND1 could be a new therapeutic target for liver cancer.

A first-in-class inhibitor, MLN4924 (pevonedistat), induces cell-cycle arrest, senescence, and apoptosis in human renal cell carcinoma by suppressing UBE2M-dependent neddylation modification

PURPOSE

MLN4924 is a second-generation inhibitor that targets ubiquitin-proteasome system by inhibiting neddylation activation enzyme (NAE), and subsequently blocking the neddylation-dependent activation of Cullin-RING E3 ligases (CRLs), which leads to the accumulation of CRLs substrates and hence, suppressing diverse tumor development. In this study, we investigated the potential application of this first-in-class inhibitor MLN4924 in the treatment of human renal cell carcinoma both in vitro and in vivo.

METHODS

The impact of MLN4924 on renal cancer cells was determined by measuring viability (MTS), proliferation cell count test and clonogenic assays, cell cycle progression (flow cytometry with propidium iodide staining), apoptosis (flow cytometry with annexin V-FITC labeling) and DNA damage (immunofluorescent staining). The cell cycle regulatory molecules, apoptosis-related molecules, and cell stress-related proteins were examined by Western blotting. The influence of tumor cell migration was analyzed by wound healing assays. A well-established SCID xenograft mouse model was used to evaluate the effects of MLN4924 on tumor growth in vivo.

RESULTS

The data showed that MLN4924 induced a dose-dependent cytotoxicity, anti-proliferation, anti-migration, and apoptosis in human renal cancer cells; and caused cell cycle arrested at the G2 phase. In addition, the E2 conjugating enzymes of Neddylation UBE2M played a major role in the proliferation control of renal cancer cells. Finally, we confirmed MLN4924 inhibited tumor growth in a RCC xenograft mouse model with minimal general toxicity.

CONCLUSION

We concluded that MLN4924 induces apoptosis and cell cycle arrest. These findings implied that MLN4924 provides a novel strategy for the treatment of RCC.

Targeting the overexpressed ROC1 induces G2 cell cycle arrest and apoptosis in esophageal cancer cells

Recent reports showed that regulator of Cullins-1 (ROC1) play an important role in tumor progression in a tumor-specific manner. However, the role and mechanism of ROC1 in esophageal cancer remains elusive. Here we demonstrated that ROC1 was overexpressed in esophageal squamous cell carcinomas, which was positive associated with poor prognosis of esophageal cancer patients. ROC1 knockdown significantly inhibited the growth of esophageal cancer cells in vitro and in vivo. Mechanistically, ROC1 silencing induced G2 cell cycle arrest and triggered apoptosis by accumulating the pro-apoptotic protein NOXA. Consistently, the downregulation of NOXA expression via siRNA substantially attenuated apoptosis induced by ROC1 silencing. These findings suggest that ROC1 is an appealing drug target for esophageal cancer.

Simvastatin and metformin inhibit cell growth in hepatitis C virus infected cells via mTOR increasing PTEN and autophagy

Hepatitis C virus (HCV) infection has been related to increased risk of development of hepatocellular carcinoma (HCC) while metformin (M) and statins treatment seemed to protect against HCC development. In this work, we aim to identify the mechanisms by which metformin and simvastatin (S) could protect from liver cancer. Huh7.5 cells were infected with HCV particles and treated with M+S. Human primary hepatocytes were treated with M+S. Treatment with both drugs inhibited Huh7.5 cell growth and HCV infection. In non-infected cells S increased translational controlled tumor protein (TCTP) and phosphatase and tensin homolog (PTEN) proteins while M inhibited mammalian target of rapamycin (mTOR) and TCTP. Simvastatin and metformin co-administered down-regulated mTOR and TCTP, while PTEN was increased. In cells infected by HCV, mTOR, TCTP, p62 and light chain 3B II (LC3BII) were increased and PTEN was decreased. S+M treatment increased PTEN, p62 and LC3BII in Huh7.5 cells. In human primary hepatocytes, metformin treatment inhibited mTOR and PTEN, but up-regulated p62, LC3BII and Caspase 3. In conclusion, simvastatin and metformin inhibited cell growth and HCV infection in vitro. In human hepatocytes, metformin increased cell-death markers. These findings suggest that M+S treatment could be useful in therapeutic prevention of HCV-related hepatocellular carcinoma.

Protein neddylation and its alterations in human cancers for targeted therapy

Neddylation, a post-translational modification that conjugates an ubiquitin-like protein NEDD8 to substrate proteins, is an important biochemical process that regulates protein function. The best-characterized substrates of neddylation are the cullin subunits of Cullin-RING ligases (CRLs), which, as the largest family of E3 ubiquitin ligases, control many important biological processes, including tumorigenesis, through promoting ubiquitylation and subsequent degradation of a variety of key regulatory proteins. Recently, increasing pieces of experimental evidence strongly indicate that the process of protein neddylation modification is elevated in multiple human cancers, providing sound rationale for its targeting as an attractive anticancer therapeutic strategy. Indeed, neddylation inactivation by MLN4924 (also known as pevonedistat), a small molecule inhibitor of E1 NEDD8-activating enzyme currently in phase I/II clinical trials, exerts significant anticancer effects by inducing cell cycle arrest, apoptosis, senescence and autophagy in a cell-type and context dependent manner. Here, we summarize the latest progresses in the field with a major focus on preclinical studies in validation of neddylation modification as a promising anticancer target.

RBX1-mediated ubiquitination of SESN2 promotes cell death upon prolonged mitochondrial damage in SH-SY5Y neuroblastoma cells

Sestrins are evolutionary conserved stress-inducible genes which regulate the axis of cell survival and cell death. Suppression of Sestrin 2 (SESN2) has been linked with increase in oxidative stress and cell death but mechanistic details related to regulation of SESN2 during mitochondrial damage remain unknown. Our study shows that prolonged CCCP-induced mitochondrial damage decreases SESN2 levels and viability of SH-SY5Y cells while overexpression of SESN2 significantly rescues the viability of cells. Further, we demonstrate that Ring box protein 1 (RBX1) is a novel interactive partner and E3 ligase for SESN2 which mediates its K-48-linked ubiquitination upon extensive mitochondrial damage. Downregulation of RBX1 causes stabilization in levels of SESN2. Notably, silencing of RBX1 expression substantially declines cell death and generation of mitochondrial ROS in response to prolonged mitochondrial damage. Taken together, we suggest that SESN2 is critical to protect cells against detrimental effect of mitochondrial damage and RBX1 is a negative regulator of SESN2 which hampers its stabilization.

Cellular senescence and liver disease: Mechanisms and therapeutic strategies

Cellular senescence is a fundamental cell fate caused by several cellular injuries which results in irreversible cell cycle arrest yet remaining metabolically active across all species. Cellular senescence not only can prevent tumor occurrence by inhibiting the proliferation of injured cells, but also can affect the surrounding cells through the senescence-associated secretory phenotype (SASP). Attractively, accumulating evidence shows that cellular senescence is closely related to various liver diseases. Therapeutic opportunities based on targeting senescent cells and the SASP are considered to be potential strategy for liver diseases. However, although research on cell senescence has attracted widespread attention, the overview on detailed mechanism and biological function of cell senescence in liver disease is still largely unknown. The present review summarizes the specific role of cell senescence in various liver diseases, and updates the molecular mechanisms underlying cell senescence. Moreover, the review also explores new strategies for prevention and treatment of liver disease through promoting senescence or counteracting excessive pathological senescence.

Targeting neddylation pathway with MLN4924 (Pevonedistat) induces NOXA-dependent apoptosis in renal cell carcinoma

Inhibition of protein neddylation pathway has emerged an attractive anticancer strategy in preclinical studies by using Nedd8-activating enzyme (NAE) inhibitor MLN4924 (Pevonedistat). Previous studies have reported the antitumor activity of MLN4924 mediated by its efficacy on apoptosis, autophagy and senescence. However, whether MLN4924 has any effect on renal carcinoma cells (RCC) remains unexplored. Here we reported that MLN4924 specifically inhibited protein neddylation pathway, leading to statistically significantly suppress the proliferation, survival and migration of RCC cells by inducing G₂ cell-cycle arrest, followed by apoptosis in a MLN4924 dose-dependent manner. Further mechanistic study revealed that MLN4924-induced apoptosis was mediated by substantial up-regulation of pro-apoptotic NOXA. These findings highlighted the anticancer effects of the neddylation inhibitors (e.g. MLN4924) for the treatment of RCC.

Expression of CDCA3 Is a Prognostic Biomarker and Potential Therapeutic Target in Non-Small Cell Lung Cancer

INTRODUCTION

NSCLC is the leading cause for cancer-related deaths worldwide. New therapeutic targets are needed, as development of resistance to current treatment, such as platinum-based chemotherapy, is inevitable. The purpose of this study was to determine the functional relevance and therapeutic potential of cell division cycle associated 3 protein (CDCA3) in NSCLC.

METHODS

The expression of CDCA3 in squamous and nonsquamous NSCLC was investigated by using bioinformatics, Western blot analysis of matched tumor and normal tissue, and immunohistochemistry of a tissue microarray. The function of CDCA3 in NSCLC was determined by using several in vitro assays with small interfering RNA depleting CDCA3 in a panel of three immortalized human bronchial epithelial cell (HBEC) lines and seven NSCLC cell lines.

RESULTS

In this study, cell division cycle associated 3 gene (CDCA3) transcripts were identified as highly increased in NSCLC versus in nonmalignant tissue, with high levels of CDCA3 being associated with poor patient prognosis. CDCA3 protein was also increased in NSCLC tissue and expression was limited to tumor cells. CDCA3 expression was similarly increased in a panel of NSCLC cell lines compared with in three HBEC lines. Although depletion of CDCA3 in the HBEC lines did not affect cellular proliferation, depletion of CDCA3 expression markedly reduced the proliferation of all NSCLC cell lines. CDCA3 depletion caused a defective G2/M-phase cell cycle progression, upregulation of p21 independent of p53, and induction of cellular senescence.

CONCLUSIONS

Our findings highlight CDCA3 as a prognostic factor and potential novel therapeutic target in NSCLC through inhibition of tumor growth and promotion of tumor senescence.

NEDD8-activating enzyme inhibitor, MLN4924 (Pevonedistat) induces NOXA-dependent apoptosis through up-regulation of ATF-4

It has been reported that MLN4924 can inhibit cell growth and metastasis in various kinds of cancer. We have reported that MLN4924 is able to inhibit angiogenesis through the induction of cell apoptosis both in vitro and in vivo models. Moreover, Neddylation inhibition using MLN4924 triggered the accumulation of pro-apoptotic protein NOXA in Human umbilical vein endothelial cells (HUVECs). However, the mechanism of MLN4924-induced NOXA up-regulation has not been addressed in HUVECs yet. In this study, we investigated how MLN4924 induced NOXA expression and cellular apoptosis in HUVECs treated with MLN4924 at indicated concentrations. MLN4924-induced apoptosis was evaluated by Annexin V-FITC/PI analysis and expression of genes associated with apoptosis was assessed by Quantitative RT-PCR and western blotting. As a result, MLN4924 triggered NOXA-dependent apoptosis in a dose-dependent manner in HUVECs. Mechanistically, inactivation of Neddylation pathway caused up-regulation of activating transcription factor 4 (ATF-4), a substrate of Cullin-Ring E3 ubiquitin ligases (CRL). NOXA was subsequently transactivated by ATF-4 and further induced apoptosis. More importantly, knockdown of ATF-4 by siRNA significantly decreased NOXA expression and apoptotic induction in HUVECs. In summary, our study reveals a new mechanism underlying MLN4924-induced NOXA accumulation in HUVECs, which may help extend further study of MLN4924 for angiogenesis inhibition treatment.

MLN4924 therapy as a novel approach in cancer treatment modalities

MLN4924 is an investigational and a newly discovered small molecule that is a potent and selective inhibitor of the NEDD8 (Neural precursor cell-Expressed Developmentally down-regulated 8) Activating Enzyme (NAE), a pivotal regulator of the Cullin Ring Ligases E3 (CRL), which has been implicated recently in DNA damage. MLN4924 effectively inhibits tumour cell growth by inducing all three common types of death, namely apoptosis, autophagy and senescence and it was also reported that the formation of capillary vessels was significantly suppressed by MLN4924.In this review, we are going to highlight the molecular mechanism of MLN4924 in cancer therapy and its pros and cons in cancer therapy.

Natriuretic peptide receptor A inhibition suppresses gastric cancer development through reactive oxygen species-mediated G2/M cell cycle arrest and cell death

Natriuretic peptide receptor A (NPRA), the major receptor for atrial natriuretic peptide (ANP), has been implicated in tumorigenesis; however, the role of ANP-NPRA signaling in the development of gastric cancer remains unclear. Immunohistochemical analyses indicated that NPRA expression was positively associated with gastric tumor size and cancer stage. NPRA inhibition by shRNA induced G2/M cell cycle arrest, cell death, and autophagy in gastric cancer cells, due to accumulation of reactive oxygen species (ROS). Either genetic or pharmacologic inhibition of autophagy led to caspase-dependent cell death. Therefore, autophagy induced by NPRA silencing may represent a cytoprotective mechanism. ROS accumulation activated c-Jun N-terminal kinase (JNK) and AMP-activated protein kinase (AMPK). ROS-mediated activation of JNK inhibited cell proliferation by disturbing cell cycle and decreased cell viability. In addition, AMPK activation promoted autophagy in NPRA-downregulated cancer cells. Overall, our results indicate that the inhibition of NPRA suppresses gastric cancer development and targeting NPRA may represent a promising strategy for the treatment of gastric cancer.

Cullin-RING ligases in regulation of autophagy

Cullin-RING ligases (CRLs), the largest E3 ubiquitin ligase family, promote ubiquitination and degradation of various cellular key regulators involved in a broad array of physiological and pathological processes, including cell cycle progression, signal transduction, transcription, cardiomyopathy, and tumorigenesis. Autophagy, an intracellular catabolic reaction that delivers cytoplasmic components to lysosomes for degradation, is crucial for cellular metabolism and homeostasis. The dysfunction of autophagy has been proved to associate with a variety of human diseases. Recent evidences revealed the emerging roles of CRLs in the regulation of autophagy. In this review, we will focus mainly on recent advances in our understandings of the regulation of autophagy by CRLs and the cross-talk between CRLs and autophagy, two degradation systems. We will also discuss the pathogenesis of human diseases associated with the dysregulation of CRLs and autophagy. Finally, we will discuss current efforts and future perspectives on basic and translational research on CRLs and autophagy.

RBX1 expression is an unfavorable prognostic factor in patients with non-small cell lung cancer

The purpose of this study was to assess the prognostic value of RBX1 in patients with non-small cell lung cancer (NSCLC). Quantitative real-time (RT-PCR) and western blot were used to evaluate the mRNA and protein expression of RBX1 in NSCLC and corresponding non-cancerous tissues. Immunohistochemistry was performed to examine the expression of RBX1 in 192 NSCLC tissue samples. Overall survival was evaluated by the Kaplan-Meier method and analyzed by the log-rank test between different groups. The results showed that the RBX1 expression was significantly higher in NSCLC tissues than the corresponding non-cancerous lung tissues. High RBX1 expression was related to poor tumor differentiation, advanced TNM stage, and lymph node metastasis. Patients with high RBX1 expression had poor overall survival than those with high expression levels, which was consistent with the results of the subgroup analysis. Multivariate analysis showed that high RBX1 expression was an unfavorable prognostic factor for NSCLC patients. Our study indicated that RBX1 might play an important role in the observation of prognosis in NSCLC and could be a valuable marker for predicting the treatment outcome in patients with NSCLC.