Overexpression of p28/gankyrin in human hepatocellular carcinoma and its clinical significance

Gankyrin inhibits ferroptosis through the p53/SLC7A11/GPX4 axis in triple-negative breast cancer cells

Gankyrin is found in high levels in triple-negative breast cancer (TNBC) and has been established to form a complex with the E3 ubiquitin ligase MDM2 and p53, resulting in the degradation of p53 in hepatocarcinoma cells. Therefore, this study sought to determine whether gankyrin could inhibit ferroptosis through this mechanism in TNBC cells. The expression of gankyrin was investigated in relation to the prognosis of TNBC using bioinformatics. Co-immunoprecipitation and GST pull-down assays were then conducted to determine the presence of a gankyrin and MDM2 complex. RT-qPCR and immunoblotting were used to examine molecules related to ferroptosis, such as gankyrin, p53, MDM2, SLC7A11, and GPX4. Additionally, cell death was evaluated using flow cytometry detection of 7-AAD and a lactate dehydrogenase release assay, as well as lipid peroxide C11-BODIPY. Results showed that the expression of gankyrin is significantly higher in TNBC tissues and cell lines, and is associated with a poor prognosis for patients. Subsequent studies revealed that inhibiting gankyrin activity triggered ferroptosis in TNBC cells. Additionally, silencing gankyrin caused an increase in the expression of the p53 protein, without altering its mRNA expression. Co-immunoprecipitation and GST pull-down experiments indicated that gankyrin and MDM2 form a complex. In mouse embryonic fibroblasts lacking both MDM2 and p53, this gankyrin/MDM2 complex was observed to ubiquitinate p53, thus raising the expression of molecules inhibited by ferroptosis, such as SLC7A11 and GPX4. Furthermore, silencing gankyrin in TNBC cells disrupted the formation of the gankyrin/MDM2 complex, hindered the degradation of p53, increased SLC7A11 expression, impeded cysteine uptake, and decreased GPX4 production. Our findings suggest that TNBC cells are able to prevent cell ferroptosis through the gankyrin/p53/SLC7A11/GPX4 signaling pathway, indicating that gankyrin may be a useful biomarker for predicting TNBC prognosis or a potential therapeutic target.

Second Generation Small Molecule Inhibitors of Gankyrin for the Treatment of Pediatric Liver Cancer

Background: Gankyrin, a member of the 26S proteasome, is an overexpressed oncoprotein in hepatoblastoma (HBL) and hepatocellular carcinoma (HCC). Cjoc42 was the first small molecule inhibitor of Gankyrin developed; however, the IC50 values of >50 μM made them unattractive for clinical use. Second-generation inhibitors demonstrate a stronger affinity toward Gankyrin and increased cytotoxicity. The aim of this study was to characterize the in vitro effects of three cjoc42 derivatives. Methods: Experiments were performed on the HepG2 (HBL) and Hep3B (pediatric HCC) cell lines. We evaluated the expression of TSPs, cell cycle markers, and stem cell markers by Western blotting and/or real-time quantitative reverse transcription PCR. We also performed apoptotic, synergy, and methylation assays. Results: The treatment with cjoc42 derivatives led to an increase in TSPs and a dose-dependent decrease in the stem cell phenotype in both cell lines. An increase in apoptosis was only seen with AFM-1 and -2 in Hep3B cells. Drug synergy was seen with doxorubicin, and antagonism was seen with cisplatin. In the presence of cjoc42 derivatives, the 20S subunit of the 26S proteasome was more available to transport doxorubicin to the nucleus, leading to synergy. Conclusion: Small-molecule inhibitors for Gankyrin are a promising therapeutic strategy, especially in combination with doxorubicin.

Activating IL-6/STAT3 Enhances Protein Stability of Proteasome 20S α+β in Colorectal Cancer by miR-1254

A widely recognized feature of colorectal cancer (CRC) is an increase in cytokine levels, which result in an inflammatory environment in the tumor. Interleukin-6 (IL-6) is a robust protumor cytokine. Several studies suggest that IL-6 plays a role in the development of tumors. Most intracellular protein breakdown occurs in eukaryotes via the ubiquitin-proteasome pathway; this mechanism may also be involved in cancer pathogenesis. The tumor tissues and paracancerous tissues were collected from 90 patients with colorectal cancer. The expressions of pSTAT3, proteasome 20S α+β, miR-1254, and PSMD1 in tissues were detected by immunohistochemistry, ELISA, and qRT-PCR, and the effects of pSTAT3 and proteasome 20s α+β expressions on the survival of patients were studied. HCT116 and HCT116-R cells were cultured and added IL-6, AG490, STAT3 plasmid, or overexpression/knockdown of miR-1254 in cells. Immunofluorescence, western blot, qRT-PCR, double luciferase gene reporter assay, and flow cytometry were used to detect the expression of pSTAT3, STAT3, proteasome 20s α+β, miR-1254, and PSMD1 and cell cycle. The nude mouse xenograft model was constructed and divided into 3 groups: PBS group, IL-6 treatment group, and IL-6+miR-1254 mimic group. After 28 days, the tumor tissues were collected, and the expressions of miR-1254, pSTST3, proteasome 20s α+β, and PSMD1 in the tissues were detected by qRT-PCR and immunohistochemistry, respectively. Our study discovered that the level of proteasome 20S α+β had a strong connection with pSTAT3 in CRC patients. They were also linked to the development and clinical outcome of CRC. In addition, we found that IL-6 dramatically increased the expression of proteasome 20S α+β and pSTAT3; however, it did not affect the proteasome 20S α+β mRNA synthesis. Circulating proteasome concentration correlated with tumor tissue proteasome 20S α+β. STAT3 could occupy the miR-1254 promoter to inhibit transcription, and it could suppressed miR-1254 which targeted PSMD10, promoting proteasome 20S α+β protein stability. This is a prospective target for developing a new colorectal cancer therapy strategy.

A druggable pocket on PSMD10Gankyrin that can accommodate an interface peptide and doxorubicin

BACKGROUND

PSMD10^Gankyrin, a proteasomal chaperone is also an oncoprotein. Overexpression of PSMD10^Gankyrin is associated with poor prognosis and survival in many cancers. Therefore, PSMD10^Gankyrin is a sought-after drug target in many hard-to-treat cancers. However, its surface appears flat and undruggable. Here, we build on our earlier discovery of a common hot spot region that defined the interface of multiple interacting partners of PSMD10^Gankyrin to expose vulnerable spots for a peptide and a small molecule inhibitor.

METHODS

High throughput virtual screening was used to screen compounds against PSMD10^Gankyrin. Interaction of PSMD10^Gankyrin with the drug or protein (CLIC1) or peptide was studied using any one or more of these techniques; Microscale Thermophoresis, limited trypsinolysis, SPR and ITC. Cytotoxic effect of doxorubicin was evaluated using MTT assay.

RESULTS

We identified doxorubicin as the first-generation small molecule inhibitor of PSMD10^Gankyrin. K116 and to a lesser extent R41 on PSMD10^Gankyrin contribute to the bulk of binding energy for the peptide EEVD, CLIC1 and doxorubicin. We further demonstrate that PSMD10^Gankyrin is an intended target for doxorubicin in cells.

GENERAL SIGNIFICANCE

Drug design against protein interactions in general and PSMD10^Gankyrin in particular, remains a challenge. We provide consolidated biophysical evidence for the use of a shared interface motif EEVD as a possible inhibitor of interaction network in cancers driven by PSMD10^Gankyrin. We identify a chemical scaffold for designing novel inhibitors of PSMD10^Gankyrin. These findings will impact the field of protein interactions in the context of disease biology/drug discovery.

Helicobacter pylori and Epstein-Barr Virus Coinfection Stimulates Aggressiveness in Gastric Cancer through the Regulation of Gankyrin

Persistent coinfection with Helicobacter pylori and Epstein-Barr virus (EBV) promotes aggressive gastric carcinoma (GC). The molecular mechanisms underlying the aggressiveness in H. pylori and EBV-mediated GC are not well characterized. We investigated the molecular mechanism involved in H. pylori- and EBV-driven proliferation of gastric epithelial cells. Results showed that the coinfection is significantly more advantageous to the pathogens as coinfection creates a microenvironment favorable to higher pathogen-associated gene expression. The EBV latent genes ebna1 and ebna3c are highly expressed in the coinfection compared to lone EBV infection at 12 and 24 h. The H. pylori-associated genes 16S rRNA, cagA, and babA were also highly expressed during coinfection compared to H. pylori alone. In addition, upregulation of gankyrin, which is a small oncoprotein, modulates various cell signaling pathways, leading to oncogenesis. Notably, the knockdown of gankyrin decreased the cancer properties of gastric epithelial cells. Gankyrin showed a similar expression pattern as that of ebna3c at both transcript and protein levels, suggesting a possible correlation. Further, EBV and H. pylori created a microenvironment that induced cell transformation and oncogenesis through dysregulation of the cell cycle regulatory (ccnd1, dapk3, pcna, and akt), GC marker (abl1, tff-2, and cdx2), cell migration (mmp3 and mmp7), DNA response (pRB, pten, and p53), and antiapoptotic (bcl2) genes in infected gastric epithelial cells through gankyrin. Our study provides a new insight into the interplay of two oncogenic agents (H. pylori and EBV) that leads to an enhanced carcinogenic activity in gastric epithelial cells through overexpression of gankyrin. IMPORTANCE In the present study, we evaluated the synergistic effects of EBV and H. pylori infection on gastric epithelial cells in various coinfection models. These coinfection models were among the first to depict the exposures of gastric epithelial cells to EBV followed by H. pylori; however, coinfection models exist that narrated the scenario upon exposure to H. pylori followed by that to EBV. We determined that a coinfection by EBV and H. pylori enhanced the expression of oncogenic protein gankyrin. The interplay between EBV and H. pylori promoted the oncogenic properties of AGS cells like elevated focus formation, cell migration, and cell proliferation through gankyrin. EBV and H. pylori mediated an enhanced expression of gankyrin, which further dysregulated cancer-associated genes such as cell migratory, tumor suppressor, DNA damage response, and proapoptotic genes.

Selenite Downregulates STAT3 Expression and Provokes Lymphocytosis in the Liver of Chronically Exposed Syrian Golden Hamsters

Arsenic is considered a worldwide pollutant that can be present in drinking water. Arsenic exposure is associated with various diseases, including cancer. Antioxidants as selenite and α-tocopherol-succinate have been shown to modulate arsenic toxic effects. Since changes in STAT3 and PSMD10 gene expression have been associated with carcinogenesis, the aim of this study was to evaluate the effect of arsenic exposure and co-treatments with selenite or α-tocopherol-succinate on the expression of these genes, in the livers of chronically exposed Syrian golden hamsters. Animals were divided into six groups: (i) control, (ii) chronically treated with 100 ppm arsenic, (iii) treated with 6 ppm α-tocopherol-succinate (α-TOS), (iv) treated with 8.5 ppm selenite, (v) treated with arsenic + α-TOS, and (vi) treated with arsenic + selenite. Urine samples and livers were collected after 20 weeks of continuous exposure. The urine samples were analyzed for arsenic species by atomic absorption spectrophotometry, and real-time RT-qPCR analysis was performed for gene expression evaluation. A reduction in STAT3 expression was observed in the selenite-treated group. No differences in PSMD10 expression were found among groups. Histopathological analysis revealed hepatic lymphocytosis in selenite-treated animals. As a conclusion, long-term exposure to arsenic does not significantly alter the expression of STAT3 and PSMD10 oncogenes in the livers of hamsters; however, selenite down-regulates STAT3 expression and provokes lymphocytosis.

Inhibiting effect of MicroRNA-3619-5p/PSMD10 axis on liver cancer cell growth in vivo and in vitro

AIMS

Liver cancer is one of the leading causes of cancer death worldwide owing to its delayed diagnosis and absence of efficient treatment at advanced TNM stages. Increasing evidence demonstrated that microRNAs are implicated in tumorgenesis and cancer development by regulating cancer-related proteins. This study aimed to explore the effect of miR-3619-5p on cell growth in liver cancer.

MAIN METHODS

The effect of miR-3619-5p on cell proliferation was measured by quantitative real-time PCR, MTT assay, flow cytometry, and Immunofluorescence assay. The interaction between miR-3619-5p and PSMD10 was validated using dual-luciferase. The expression of PSMD10 and Ki67 was further determined by immunohistochemistry.

KEY FINDINGS

MiR-3619-5p over-expression remarkably inhibited cell proliferation and induced G1 phase arrest, accompanied with reduced expression of proliferating cell nuclear antigen. The expression of miR-3619-5p was negatively correlated to that of PSMD10, and PSMD10 was validated to be a downstream target of miR-3619-5p. Moreover, miR-3619-5p induced suppressed proliferation and G1 phase arrest were abrogated by elevated the expression of PSMD10 in liver cancer cells. PSMD10 over-expression also induced phosphorylation of signal transducer and activator of transcription 3 (STAT3) and retinoblastoma protein (Rb1). Besides, elevated cyclin A, cyclin D1 and cyclin E expression supported that PSMD10 promoted the progress of cell cycle. In addition, miR-3619-5p inhibited tumor growth in vivo by targeting PSMD10, accompanied with blocked cell cycle.

SIGNIFICANCE

In conclusion, our findings revealed that miR-3619-5p inhibits cancer cell proliferation by targeting PSMD10, and miR-3619-5p as a potential therapeutic target for the treatment of liver cancer.

An Allosteric Interaction Network Promotes Conformation State-Dependent Eviction of the Nas6 Assembly Chaperone from Nascent 26S Proteasomes

The 26S proteasome is the central ATP-dependent protease in eukaryotes and is essential for organismal health. Proteasome assembly is mediated by several dedicated, evolutionarily conserved chaperone proteins. These chaperones associate transiently with assembly intermediates but are absent from mature proteasomes. Chaperone eviction upon completion of proteasome assembly is necessary for normal proteasome function, but how they are released remains unresolved. Here, we demonstrate that the Nas6 assembly chaperone, homolog of the human oncogene gankyrin, is evicted from nascent proteasomes during completion of assembly via a conformation-specific allosteric interaction of the Rpn5 subunit with the proteasomal ATPase ring. Subsequent ATP binding by the ATPase subunit Rpt3 promotes conformational remodeling of the ATPase ring that evicts Nas6 from the nascent proteasome. Our study demonstrates how assembly-coupled allosteric signals promote chaperone eviction and provides a framework for understanding the eviction of other chaperones from this bio-medically important molecular machine.

Nemec et al. report how the evolutionarily conserved Nas6 assembly chaperone is evicted from nascent 26S proteasomes. Nucleotide binding events within the nascent proteasome trigger formation of conformation-specific intersubunit contacts that expel Nas6. This mechanism may serve a quality control function by blocking formation of 26S proteasomes from defective components.

LncRNA DANCR Promotes Sorafenib Resistance via Activation of IL-6/STAT3 Signaling in Hepatocellular Carcinoma Cells

Background

Hepatocellular carcinoma (HCC) is one of the major malignancies and the second most common cause of cancer-related death worldwide. Sorafenib, an approved first-line systematic treatment agent for HCC, is capable to effectively improve the survival of patients with advanced HCC. The long-noncoding RNA (lncRNA) differentiation antagonizing non-protein coding RNA (DANCR) has been reported to exert oncogenic functions in several kinds of human cancers. However, the role of lncRNA DANCR in sorafenib resistance in HCC remains unknown.

Methods

The expression levels of DANCR in HCC tissues were detected by qRT-PCR. DANCR overexpression and knockdown models were established and utilized to investigate the functional role of DANCR on sorafenib resistance in HCC cells. The MS2-binding sequences-MS2-binding protein–based RNA immunoprecipitation assay, RNA pull-down and luciferase reporter assay was used to detect the association between DANCR and PSMD10 mRNA. The activation of DANCR transcription mediated by STAT3 was assessed by luciferase reporter and chromatin immunoprecipitation assays.

Results

We found that DANCR was significantly overexpressed in HCC tissues and associated with prognosis of HCC patients. Overexpression and knockdown experiments demonstrated that DANCR promoted sorafenib resistance in HCC cells in vitro and in vivo. Mechanistically, the role of DANCR relied largely on the association with PSMD10. DANCR stabilized PSMD10 mRNA through blocking the repressing effect of several microRNAs on PSMD10. Besides, DANCR activated IL-6/STAT3 signaling via PSMD10. Furthermore, we revealed that DANCR transcription was enhanced by the activation of IL-6/STAT3 signaling, indicating a positive feedback loop of DANCR and IL-6/STAT3 signaling.

Conclusion

Collectively, our study is the first to elucidate the mechanism of DANCR-mediated sorafenib resistance via PSMD10-IL-6/STAT3 signaling axis, which provides a promising target for developing new therapeutic strategy for sorafenib tolerance of HCC.

The oncogene Gankyrin is expressed in testicular cancer and contributes to cisplatin sensitivity in embryonal carcinoma cells

Background

Testicular germ cell cancer (TGCC) develops from pre-malignant germ neoplasia in situ (GCNIS) cells. GCNIS originates from fetal gonocytes (POU5F1⁺/MAGE-A4⁻), which fail to differentiate to pre-spermatogonia (POU5F1⁻/MAGE-A4⁺) and undergo malignant transformation. Gankyrin is an oncogene which has been shown to prevent POU5F1 degradation and specifically interact with MAGE-A4 in hepatocellular carcinoma (HCC) cells. We aimed to investigate the role of Gankyrin in progression from gonocyte to pre-invasive GCNIS and subsequent invasive TGCC.

Methods

We determined Gankyrin expression in human fetal testicular tissue (gestational weeks 9–20; n = 38), human adult testicular tissue with active spermatogenesis (n = 9), human testicular tissue with germ cell maturation delay (n = 4), testicular tissue from patients with pre-invasive GCNIS (n = 6), and invasive TGCC including seminoma (n = 6) and teratoma (n = 7). Functional analysis was performed in-vitro by siRNA knock-down of Gankyrin in the NTera2 cells (derived from embryonal carcinoma).

Results

Germ cell expression of Gankyrin was restricted to a sub-population of prespermatogonia in human fetal testes. Nuclear Gankyrin was also expressed in GCNIS cells of childhood and adult pre-invasive TGCC patients, and in GCNIS from seminoma and non-seminoma patients. Cytoplasmic expression was observed in seminoma tumour cells and NTera2 cells. Gankyrin knock-down in NTera2 cells resulted in an increase in apoptosis mediated via the TP53 pathway, whilst POU5F1 expression was unaffected. Furthermore, Gankyrin knock-down in NTera2 cells increased cisplatin sensitivity with an increase in cell death (13%, p < 0.05) following Gankyrin knock-down, when compared to cisplatin treatment alone, likely via BAX and FAS. Our results demonstrate that Gankyrin expression changes in germ cells during normal transition from gonocyte to prespermatogonia. In addition, changes in Gankyrin localisation are associated with progression of pre-invasive GCNIS to invasive TGCC. Furthermore, we found that Gankyrin is involved in the regulation of NTera2 cell survival and that a reduction in Gankyrin expression can modulate cisplatin sensitivity.

Conclusions

These results suggest that manipulation of Gankyrin expression may reduce the cisplatin dose required for the treatment of TGCC, with benefits in reducing dose-dependent side effects of chemotherapy. Further studies are required in order to assess the effects of modulating Gankyrin on GCNIS/TGCC using in vivo models.

Small-Molecule Inhibitors of the Proteasome's Regulatory Particle

Cells need to synthesize and degrade proteins consistently. Maintaining a balanced level of protein in the cell requires a carefully controlled system and significant energy. Degradation of unwanted or damaged proteins into smaller peptide units can be accomplished by the proteasome. The proteasome is composed of two main subunits. The first is the core particle (20S CP), and within this core particle are three types of threonine proteases. The second is the regulatory complex (19S RP), which has a myriad of activities including recognizing proteins marked for degradation and shuttling the protein into the 20S CP to be degraded. Small-molecule inhibitors of the 20S CP have been developed and are exceptional treatments for multiple myeloma (MM). 20S CP inhibitors disrupt the protein balance, leading to cellular stress and eventually to cell death. Unfortunately, the 20S CP inhibitors currently available have dose-limiting off-target effects and resistance can be acquired rapidly. Herein, we discuss small molecules that have been discovered to interact with the 19S RP subunit or with a protein closely associated with 19S RP activity. These molecules still elicit their toxicity by preventing the proteasome from degrading proteins, but do so through different mechanisms of action.

Dysregulation of Nrf2 in Hepatocellular Carcinoma: Role in Cancer Progression and Chemoresistance

The liver executes versatile functions and is the chief organ for metabolism of toxicants/xenobiotics. Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and the third foremost cause of cancer death worldwide. Oxidative stress is a key factor related with the development and progression of HCC. Nuclear factor erythroid 2 [NF-E2]-related factor 2 (Nrf2) is a cytosolic transcription factor, which regulates redox homeostasis by activating the expression of an array of antioxidant response element-dependent genes. Nrf2 displays conflicting roles in normal, healthy liver and HCC; in the former, Nrf2 offers beneficial effects, whereas in the latter it causes detrimental effects favouring the proliferation and survival of HCC. Sustained Nrf2 activation has been observed in HCC and facilitates its progression and aggressiveness. This review summarizes the role and mechanism(s) of action of Nrf2 dysregulation in HCC and therapeutic options that can be employed to modulate this transcription factor.

Small interfering RNA-mediated gene suppression as a therapeutic intervention in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the lethal and difficult-to-cure cancers worldwide. Owing to the late diagnosis and drug resistance of malignant hepatocytes, treatment of this cancer by conventional chemotherapy agents is challenging, and researchers are seeking new alternative treatment options to overcome therapy resistance in this neoplasm. RNA interference (RNAi) is a potent and specific approach in targeting gene expression and has emerged as a novel therapeutic tool for many diseases, including cancers. Small interfering RNA (siRNA) is a type of RNAi that is produced intracellularly from exogenous synthetic oligonucleotides and can selectively knock down target gene expression in a sequence-specific manner. Various factors play roles in the initiation and progression of HCC and provide multiple candidate targets for siRNA intervention. In addition, due to the liver's unique architecture and availability of some hepatic siRNA delivery methods, this organ has received much more attention as a target tissue for such oligonucleotide action. Recent advances in designing nanoparticle systems for the in vivo delivery of siRNAs have markedly enhanced the potency of siRNA-mediated gene silencing under clinical development for HCC therapy. The utility of siRNAs as anti-HCC agents is the subject of the current review. siRNA-based gene therapies could be one of the main feasible approaches for HCC therapy in the future.

Gankyrin as a potential target for tumor therapy: evidence and perspectives

Gankyrin (also known as PSMD10 or p28GANK), engages in diverse biological processes, including cellular growth, proliferation and invasion. Several studies have demonstrated that Gankyrin is a candidate oncogene. In parallel, the dysregulation of Gankyrin has been observered in a variety of human cancer. Overexpression of Gankyrin is involved in tumor initiation and progression by regulating several signaling pathways that control cell-cycle process, cell growth, apoptosis, et al. On the contrary, downregulation of Gankyrin significantly inhibits cell growth, proliferation and metastasis. Therefore, Gankyrin appears to be a potential target for tumor therapy. Herein, this review summarizes the current knowledge in understanding the biological functions and oncogenic role of Gankyrin in human cancers from the perspective of clinical-pathological significances, aiming to provide guidance for the development of Gankyrin-targeted therapy.

Minority stress and leukocyte gene expression in sexual minority men living with treated HIV infection

Sexual minority (i.e., non-heterosexual) individuals experience poorer mental and physical health, accounted for in part by the additional burden of sexual minority stress occurring from being situated in a culture favoring heteronormativity. Informed by previous research, the purpose of this study was to identify the relationship between sexual minority stress and leukocyte gene expression related to inflammation, cancer, immune function, and cardiovascular function. Sexual minority men living with HIV who were on anti-retroviral medication, had viral load < 200 copies/mL, and had biologically confirmed, recent methamphetamine use completed minority stress measures and submitted blood samples for RNA sequencing on leukocytes. Differential gene expression and pathway analyses were conducted comparing those with clinically elevated minority stress (n = 18) and those who did not meet the clinical cutoff (n = 20), covarying reactive urine toxicology results for very recent stimulant use. In total, 90 differentially expressed genes and 138 gene set pathways evidencing 2-directional perturbation were observed at false discovery rate (FDR) < 0.10. Of these, 41 of the differentially expressed genes and 35 of the 2-directionally perturbed pathways were identified as functionally related to hypothesized mechanisms of inflammation, cancer, immune function, and cardiovascular function. The neuroactive-ligand receptor pathway (implicated in cancer development) was identified using signaling pathway impact analysis. Our results suggest several potential biological pathways for future work investigating the relationship between sexual minority stress and health.

Nrf2-p62 autophagy pathway and its response to oxidative stress in hepatocellular carcinoma

Deregulation of autophagy is proposed to play a key pathogenic role in hepatocellular carcinoma (HCC), the most common primary malignancy of the liver and the third leading cause of cancer death. Autophagy is an evolutionarily conserved catabolic process activated to degrade and recycle cell's components. Under stress conditions, such as oxidative stress and nutrient deprivation, autophagy is an essential survival pathway that operates in harmony with other stress response pathways. These include the redox-sensitive transcription complex Nrf2-Keap1 that controls groups of genes with roles in detoxification and antioxidant processes, intermediary metabolism, and cell cycle regulation. Recently, a functional association between a dysfunctional autophagy and Nrf2 pathway activation has been identified in HCC. This appears to occur through the physical interaction of the autophagy adaptor p62 with the Nrf2 inhibitor Keap1, thus leading to increased stabilization and transcriptional activity of Nrf2, a key event in reprogramming metabolic and stress response pathways of proliferating hepatocarcinoma cells. These emerging molecular mechanisms and the therapeutic perspective of targeting Nrf2-p62 interaction in HCC are discussed in this paper along with the prognostic value of autophagy in this type of cancer.

Gankyrin: a novel promising therapeutic target for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is known as fifth common malignancies and third common cause of cancer-related death worldwide. The identification of various mechanisms which are involved in hepatocarcinogenesis contributes in finding a variety of cellular and molecular targets for HCC diagnosis, prevention and therapy. Among various identified targets in HCC pathogenesis, Gankyrin is a crucial oncoprotein that is up-regulated in HCC and plays a pivotal role in the initiation and progression of the HCC. Oncogenic role of Gankyrin has been found to stem from inhibition of two ubiquitous tumour suppressor proteins, retinoblastoma protein (pRb) and P53, and also modulation of several vital cellular signalling pathways including Wnt/β-Catenin, NF-κB, STAT3/Akt, IL-1β/IRAK-1 and RhoA/ROCK. As a result, Gankyrin can be considered as a potential candidate for diagnosis and treatment of HCC. In this review, we summarized the physiological function and the significant role of Gankyrin as an important therapeutic target in HCC.

Gankyrin has an antioxidative role through the feedback regulation of Nrf2 in hepatocellular carcinoma

Yang et al. identify a feedback loop between gankyrin, an oncoprotein overexpressed in human hepatocellular carcinoma (HCC), and Nrf2. The positive feedback modulates a series of antioxidant enzymes that lower intracellular reactive oxygen species to confer protection from mitochondrial damage and cell death.

Oxidative stress status has a key role in hepatocellular carcinoma (HCC) development and progression. Normally, reactive oxygen species (ROS) levels are tightly controlled by an inducible antioxidant program that responds to cellular stressors. How HCC cells respond to excessive oxidative stress remains elusive. Here, we identified a feedback loop between gankyrin, an oncoprotein overexpressed in human HCC, and Nrf2 maintaining the homeostasis in HCC cells. Mechanistically, gankyrin was found to interact with the Kelch domain of Keap1 and effectively competed with Nrf2 for Keap1 binding. Increased expression of gankyrin in HCC cells blocked the binding between Nrf2 and Keap1, inhibiting the degradation of Nrf2 by proteasome. Interestingly, accumulation and translocation of Nrf2 increased the transcription of gankyrin through binding to the ARE elements in the promoter of gankyrin. The positive feedback regulation involving gankyrin and Nrf2 modulates a series of antioxidant enzymes, thereby lowering intracellular ROS and conferring a steadier intracellular environment, which prevents mitochondrial damage and cell death induced by excessive oxidative stress. Our results indicate that gankyrin is a regulator of cellular redox homeostasis and provide a link between oxidative stress and the development of HCC.

Synthetic Proteins Potently and Selectively Bind the Oncoprotein Gankyrin, Modulate Its Interaction with S6 ATPase, and Suppress Gankyrin/MDM2-Dependent Ubiquitination of p53

Overexpression of the ankyrin repeat oncoprotein gankyrin is directly linked to the onset, proliferation, and/or metastasis of many cancers. The role of gankyrin in multiple disease-relevant biochemical processes is profound. In addition to other cellular processes, gankyrin overexpression leads to decreased cellular levels of p53, through a complex that involves MDM2. Thus, inhibition of this interaction is an attractive strategy for modulating oncogenic phenotypes in gankyrin-overexpressing cells. However, the lack of well-defined, hydrophobic, small-molecule binding pockets on the putative ankyrin repeat binding face presents a challenge to traditional small-molecule drug discovery. In contrast, by virtue of their size and relatively high folding energies, synthetic gankyrin-binding proteins could, in principle, compete with physiologically relevant PPIs involving gankyrin. Previously, we showed that a shape-complementary protein scaffold can be resurfaced to bind gankyrin with moderate affinity (KD ∼6 μM). Here, we used yeast display high-throughput screening, error-prone PCR, DNA shuffling, and protein engineering to optimize this complex. The best of these proteins bind gankyrin with excellent affinity (KD ∼21 nM), selectively co-purifies with gankyrin from a complex cellular milieu, modulates an interaction between gankyrin and a physiological binding partner (S6 ATPase), and suppresses gankyrin/MDM2-dependent ubiquitination of p53.

Gankyrin is a predictive and oncogenic factor in well-differentiated and dedifferentiated liposarcoma

Liposarcoma is one of the most common histologic types of soft tissue sarcoma and is frequently an aggressive cancer with poor outcome. Hence, alternative approaches other than surgical excision are necessary to improve treatment of well-differentiated/dedifferentiated liposarcoma (WDLPS/DDLPS).

For this reason, we performed a two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry/mass spectrometry (MALDI-TOF/MS) analysis to identify new factors for WDLPS and DDLPS. Among the selected candidate proteins, gankyrin, known to be an oncoprotein, showed a significantly high level of expression pattern and inversely low expression of p53/p21 in WDLPS and DDLPS tissues, suggesting possible utility as a new predictive factor. Moreover, inhibition of gankyrin not only led to reduction of in vitro cell growth ability including cell proliferation, colony-formation, and migration, but also in vivo DDLPS cell tumorigenesis, perhaps via downregulation of the p53 tumor suppressor gene and its p21 target and also reduction of AKT/mTOR signal activation. This study identifies gankyrin, for the first time, as new potential predictive and oncogenic factor of WDLPS and DDLPS, suggesting the potential for service as a future LPS therapeutic approach.

p28(GANK) associates with p300 to attenuate the acetylation of RelA

Oncoprotein p28(GANK), overexpressed in hepatocellular carcinomas (HCC), binds to RelA and retains NF-κB in the cytoplasm to suppress NF-κB transactivation. However, the mechanism has not yet been elucidated. In this study, we clarified the mechanism of NF-κB regulated by p28(GANK). p28(GANK) reduced TNF-α-induced nuclear translocation of RelA/NF-κB independent of HDAC3. p28(GANK) interacted with p300 to attenuate assembly of RelA with p300, which lessened acetylation of RelA on the lysine 310 sites. Moreover, overexpression of p28(GANK) attenuated the capability of NF-κB binding to the target gene IκBα promoter, but also weakened adriamycin-induced NF-κB pro-apoptotic gene Fas and FasL expression, which subsequently made p53-deficient tumor cells resistance to adriamycin. These results present mechanistic insight into the key role of p28(GANK) in post-translational regulation of RelA/NF-κB.

Identification of miR-145 targets through an integrated omics analysis

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression and protein synthesis. To characterize functions of miRNAs and to assess their potential applications, we carried out an integrated multi-omics analysis to study miR-145, a miRNA that has been shown to suppress tumor growth. We employed gene expression profiling, miRNA profiling and quantitative proteomic analysis of a pancreatic cancer cell line. In our transcriptomic analysis, overexpression of miR-145 was found to suppress the expression of genes that are implicated in development of cancer such as ITGA11 and MAGEA4 in addition to previously described targets such as FSCN1, YES1 and PODXL. Based on miRNA profiling, overexpression of miR-145 also upregulated other miRNAs including miR-124, miR-133b and miR-125a-3p, all of which are implicated in suppression of tumors and are generally co-regulated with miR-145 in other cancers. Using the SILAC system, we identified miR-145-induced downregulation of several oncoproteins/cancer biomarkers including SET, RPA1, MCM2, ABCC1, SPTBN1 and SPTLC1. Luciferase assay validation carried out on a subset of downregulated candidate targets confirmed them to be novel direct targets of miR-145. Overall, this multi-omics approach provided insights into miR-145-mediated tumor suppression and could be used as a general strategy to study the targets of individual miRNAs.

Characterization of the binding interaction between the oncoprotein gankyrin and a grafted S6 ATPase

A complex with the C-terminal portion of the proteosomal subunit S6 ATPase is the only available structure of a protein-protein interaction involving the oncoprotein gankyrin. However, difficulties associated with recombinant expression of S6 ATPase alone, or truncations thereof, have limited our understanding of this assembly. We replaced the C-terminal portion of FtsH from Escherichia coli with the structurally homologous C-terminal portion of S6 ATPase and used this grafted protein to characterize the gankyrin-S6 ATPase binding interaction by isothermal titration calorimetry.

Resurfaced shape complementary proteins that selectively bind the oncoprotein gankyrin

Increased cellular levels of protein-protein interactions involving the ankyrin repeat oncoprotein gankyrin are directly linked to aberrant cellular events and numerous cancers. Inhibition of these protein-protein interactions is thus an attractive therapeutic strategy. However, the relatively featureless topology of gankyrin's putative binding face and large surface areas involved in gankyrin-dependent protein-protein interactions present a dramatic challenge to small molecule discovery. The size, high folding energies, and well-defined surfaces present in many proteins overcome some of the challenges faced by small molecule discovery. We used split-superpositive Green Fluorescent Protein (split-spGFP) reassembly to screen a 5×10(9) library of resurfaced proteins that are shape complementary to the putative binding face of gankyrin and identified mutants that potently and selectively bind this oncoprotein in vitro and in living cells. Collectively, our findings represent the first synthetic proteins that bind gankyrin and may represent a general strategy for developing protein basic research tools and drug leads that bind disease-relevant ankyrin repeats.

Gradually elevated expression of Gankyrin during human hepatocarcinogenesis and its clinicopathological significance

Gankyrin is an important oncoprotein that is overexpressed in human hepatocellular carcinoma (HCC). However, the gradual alteration of Gankyrin in successive stages during human HCC development and the mechanism of Gankyrin-mediated hepatocarcinogenesis remain largely unknown. In this study, we evaluated the pattern and level of Gankyrin protein expression using immunohistochemistry in various liver tissues, including normal liver, chronic hepatitis, cirrhosis, adenomatous hyperplasia (AH), and HCC tissues, to analyze its clinicopathological significance. Furthermore, we stably transfected the shRNA-Gan vector, which targets human Gankyrin, into HepG2 cells to assess the role of Gankyrin in cell proliferation and tumorigenicity. The expression level of Gankyrin in the cytoplasm, nucleus, and whole cell was gradually elevated during consecutive stages of hepatocarcinogenesis. The nuclear Gankyrin level in AH was significantly higher than that in normal liver, chronic hepatitis, and cirrhotic tissues. The cytoplasmic, nuclear, and total cellular Gankyrin expression levels in HCC were significantly correlated with capsular invasion and intrahepatic metastasis. Silencing Gankyrin expression using shRNA-Gan repressed tumor cell proliferation, tumorigenicity, migration, and invasion in vitro. Our findings demonstrate that Gankyrin is aberrantly expressed beginning at the initiation stage and plays an important role in the initiation, promotion, and progression of hepatocarcinogenesis.

Expression of the oncoprotein gankyrin and phosphorylated retinoblastoma protein in human testis and testicular germ cell tumor

OBJECTIVE

The oncoprotein, gankyrin, is known to facilitate cell proliferation through phosphorylation and degradation of retinoblastoma protein. In the present study, we evaluated the expression of gankyrin and phosphorylated retinoblastoma protein in human testis and testicular germ cell tumors.

METHODS

The effects of suppression of gankyrin by locked nucleic acid on phosphorylation status of retinoblastoma and cell proliferation were analyzed using western blot analysis and testicular tumor cell line NEC8. The expressions of gankyrin, retinoblastoma and retinoblastoma protein were analyzed in 93 testicular germ cell tumor samples and five normal human testis by immunohistochemistry. The retinoblastoma protein expression was determined using an antibody to retinoblastoma protein, Ser795.

RESULTS

Gankyrin was expressed in NEC8 cells as well as a normal human testis and testicular tumors. Suppression of gankyrin by locked nucleic acid led to suppression of retinoblastoma protein and cell proliferation in NEC8 cells. Immunohistochemistry of normal testis showed that gankyrin is expressed dominantly in spermatocytes. In testicular germ cell tumors, high expressions of gankyrin and phosphorylated-retinoblastoma protein were observed in seminoma and embryonal carcinoma, whereas the expressions of both proteins were weak in histological subtypes of non-seminoma. Growing teratoma and testicular malignant transformation tissues expressed phosphorylated-retinoblastoma protein strongly, but gankyrin faintly.

CONCLUSION

Gankyrin is dominantly expressed in normal spermatocytes and seminoma/embryonal carcinoma, and its expression correlates well with retinoblastoma protein expression except in the growing teratoma and testicular malignant transformation cases. These data provide new insights into the molecular mechanisms of normal spermatogenesis and pathogenesis of testicular germ cell tumors.

Gankyrin is frequently overexpressed in cervical high grade disease and is associated with cervical carcinogenesis and metastasis

Our previous studies have showed that Gankyrin expression is correlated with a malignant phenotype in endometrial carcinoma. Here, we investigated the possible role of Gankyrin in cervical disease. The increasing protein level of Gankyrin was observed in high-grade cervical intraepithelial neoplasia and carcinoma compared with benign cervical tissues and low-grade cervical intraepithelial neoplasia. In para-carcinoma tissues, it was found interestingly that there was no lymph node metastasis when nuclei Gankyrin was positively expressed, but lymph node metastasis rate was 30% (6/20) when nuclei Gankyrin was negatively expressed. In vitro, the transfection of Gankyrin resulted in markedly up-regulating of Vimentin, β-catenin and Twist2, as well as down-regulating of E-cadherin in cervical carcinoma cells. Our results suggested that Gankyrin may be functional in cervical carcinogenesis and metastasis.

Gankyrin promotes tumor growth and metastasis through activation of IL-6/STAT3 signaling in human cholangiocarcinoma

Although gankyrin is involved in the tumorigenicity and metastasis of some malignancies, the role of gankyrin in cholangiocarcinoma (CCA) is unclear. In this study we investigated the expression of gankyrin in human CCA tissues and cell lines. The effects of gankyrin on CCA tumor growth and metastasis were determined both in vivo and in vitro. The results showed that gankyrin was overexpressed in CCA tissues and cell lines. Gankyrin expression was associated with CCA histological differentiation, TNM stage, and metastasis. The multivariate Cox analysis revealed that gankyrin was an independent prognostic indicator for overall survival. Gankyrin overexpression promoted CCA cell proliferation, migration, and invasion, while gankyrin knockdown inhibited CCA tumor growth, metastasis, and induced Rb-dependent senescence and G1 phase cell cycle arrest. Gankyrin increased the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and promoted the nuclear translocation of p-STAT3. Suppression of STAT3 signaling by small interfering RNA (siRNA) or STAT3 inhibitor interfered with gankyrin-mediated carcinogenesis and metastasis, while interleukin (IL)-6, a known upstream activator of STAT3, could restore the proliferation and migration of gankyrin-silenced CCA cells. The IL-6 level was decreased by gankyrin knockdown, while increased by gankyrin overexpression. Gankyrin regulated IL-6 expression by way of facilitating the phosphorylation of Rb; meanwhile, rIL-6 treatment increased the expression of gankyrin, suggesting that IL-6 was regulated by a positive feedback loop involving gankyrin in CCA. In the xenograft experiments, gankyrin overexpression accelerated tumor formation and increased tumor weight, whereas gankyrin knockdown showed the opposite effects. The in vivo spontaneous metastasis assay revealed that gankyrin promoted CCA metastasis through IL-6/STAT3 signaling pathway.

CONCLUSION

Gankyrin is crucial for CCA carcinogenesis and metastasis by activating IL-6/STAT3 signaling pathway through down-regulating Rb protein.

Discovery of multiple interacting partners of gankyrin, a proteasomal chaperone and an oncoprotein--evidence for a common hot spot site at the interface and its functional relevance

Gankyrin, a non-ATPase component of the proteasome and a chaperone of proteasome assembly, is also an oncoprotein. Gankyrin regulates a variety of oncogenic signaling pathways in cancer cells and accelerates degradation of tumor suppressor proteins p53 and Rb. Therefore gankyrin may be a unique hub integrating signaling networks with the degradation pathway. To identify new interactions that may be crucial in consolidating its role as an oncogenic hub, crystal structure of gankyrin-proteasome ATPase complex was used to predict novel interacting partners. EEVD, a four amino acid linear sequence seems a hot spot site at this interface. By searching for EEVD in exposed regions of human proteins in PDB database, we predicted 34 novel interactions. Eight proteins were tested and seven of them were found to interact with gankyrin. Affinity of four interactions is high enough for endogenous detection. Others require gankyrin overexpression in HEK 293 cells or occur endogenously in breast cancer cell line- MDA-MB-435, reflecting lower affinity or presence of a deregulated network. Mutagenesis and peptide inhibition confirm that EEVD is the common hot spot site at these interfaces and therefore a potential polypharmacological drug target. In MDA-MB-231 cells in which the endogenous CLIC1 is silenced, trans-expression of Wt protein (CLIC1_EEVD) and not the hot spot site mutant (CLIC1_AAVA) resulted in significant rescue of the migratory potential. Our approach can be extended to identify novel functionally relevant protein-protein interactions, in expansion of oncogenic networks and in identifying potential therapeutic targets.

Gankyrin is essential for hypoxia enhanced metastatic potential in breast cancer cells

Hypoxia, a critical regulator of tumor growth and metastasis, induces the transcriptional activation of several pathways involved in proliferation, migration and invasion. Gankyrin was found to be overexpressed, and also promoted the metastasis in breast cancer cells, which is also involved in the regulation of hypoxia inducible factor‑1 and hypoxia‑inducible factor‑1α. The present study showed that gankyrin mRNA and protein expression were increased under hypoxic conditions in the BT474 breast cancer cell line, accompanied with increased ability of cell migration and invasion. Lentivirus‑mediated siRNA targeting gankyrin was transfected into BT474 cells. Wound‑healing and transwell experiments showed that gankyrin deletion abrogated the increased migration and invasion of BT474 cells due to hypoxia. In addition, E‑cadherin was found to be involved in the gankyrin induced invasion of breast cancer cells due to hypoxia. The present study indicated that gankyrin deletion abrogated the increased metastatic potential of breast cancer cells under hypoxic conditions partly through regulating E‑cadherin, suggesting that an improved understanding of gankyrin may offer a potential therapeutic target for the treatment of human breast cancer metastasis.

The impact of hypoxia in hepatocellular carcinoma metastasis

Hypoxia is a common phenomenon in hepatocellular carcinoma (HCC). Hypoxia stabilizes transcription factor, hypoxia-inducible factor (HIF), to activate gene transcription. Expression of HIF is closely associated with metastasis and poor prognosis in HCC. HIF mediates expression of genes that are involved in every step of HCC metastasis including epithelial-mesenchymal transition, invasion of the extracellular matrix, intravasation, extravasation, and secondary growth of the metastases. Because HIF is the central regulator of HCC metastasis, HIF inhibitors are attractive tools when used alone or as combined treatment to curb HCC metastasis. This review will summarize the current findings on the impact of hypoxia/HIF in HCC, with a particular focus on cancer metastasis.

Farnesoid X receptor inhibits gankyrin in mouse livers and prevents development of liver cancer

One of the early events in the development of liver cancer is a neutralization of tumor suppressor proteins Rb, p53, hepatocyte nuclear factor 4α (HNF4α), and CCAAT/enhancer binding protein (C/EBP) α. The elimination of these proteins is mediated by a small subunit of proteasome, gankyrin, which is activated by cancer. The aim of this study was to determine the mechanisms that repress gankyrin in quiescent livers and mechanisms of activation of gankyrin in liver cancer. We found that farnesoid X receptor (FXR) inhibits expression of gankyrin in quiescent livers by silencing the gankyrin promoter through HDAC1-C/EBPβ complexes. C/EBPβ is a key transcription factor that delivers HDAC1 to gankyrin promoter and causes epigenetic silencing of the promoter. We show that down-regulation of C/EBPβ in mouse hepatoma cells and in mouse livers reduces C/EBPβ-HDAC1 complexes and activates the gankyrin promoter. Deletion of FXR signaling in mice leads to de-repression of the gankyrin promoter and to spontaneous development of liver cancer at 12 months of age. Diethylnitrosoamine (DEN)-mediated liver cancer in wild-type mice also involves the reduction of FXR and activation of gankyrin. Examination of liver cancer in old mice and liver cancer in human patients revealed that FXR is reduced, while gankyrin is elevated during spontaneous development of liver cancer. Searching for animal models with altered levels of FXR, we found that long-lived Little mice have high levels of FXR and do not develop liver cancer with age and after DEN injections due to failure to activate gankyrin and eliminate Rb, p53, HNF4α and C/EBPα proteins.

CONCLUSION

FXR prevents liver cancer by inhibiting the gankyrin promoter via C/EBPβ-HDAC1 complexes, leading to subsequent protection of tumor suppressor proteins from degradation.

Up-regulated oncoprotein P28GANK correlates with proliferation and poor prognosis of human glioma

Background

The significance of p28GANK in gliomas remains unknown. This study aims to clarify the clinical significance of p28GANK in human gliomas.

Methods

The expression of p28GANK in 138 gliomas and 50 matched para-cancerous tissues was detected by immunohistochemical staining, and statistical analyses were performed to test the correlation of p28GANK with clinical parameters. To investigate the effects of p28GANK down-regulation on the growth of cells both in vitro and in vivo, an siRNA targeting p28GANK was transfected into U251 cells.

Results

P28GANK expression was significantly higher in tumor specimens than in matched para-cancerous tissues. Over-expressed p28GANK significantly correlated with high karnofsky performance score (KPS), advanced WHO grade and poor overall survival of the patients. Univariate analysis showed that WHO grade and KPS also correlated with the survival of patients, and multivariate analysis suggested that KPS and p28GANK expression were two independent prognostic factors. Moreover, p28GANK gene silencing decreased the malignant growth of U251 cells both in vitro and in vivo.

Conclusions

Increased expression of p28GANK is correlated with poor clinical outcomes in glioma patients. The down-regulation of p28GANK significantly inhibited cell proliferation, indicating that p28GANK might be a potential therapeutic target for glioma treatment.

Role of miR-224 in hepatocellular carcinoma: a tool for possible therapeutic intervention?

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide, characterized by high mortality rate and poor prognosis. Our understanding of the HCC pathology is still very much fragmented and little progress has been made to improve the clinical outcome of HCC patients. While recently discovered microRNA deregulation in HCC has added to the complexity of our understanding of HCC, it has also presented promising novel approaches to understand, diagnose and treat HCC. Here, we highlight one miRNA, miR-224, which has been more consistently reported to be upregulated in HCC than other miRNAs. We will discuss the validated and predicted functional roles of this miRNA in HCC, speculate on the possible mechanism for its upregulation in HCC and explore the potential of miR-224 as an exciting novel biomarker for the early detection of liver malignancies as well as a novel therapeutic target for HCC treatment.

MicroRNA-224 is up-regulated in hepatocellular carcinoma through epigenetic mechanisms

MicroRNA-224 (miR-224) is one of the most commonly up-regulated microRNAs in hepatocellular carcinoma (HCC), which affects crucial cellular processes such as apoptosis and cell proliferation. In this study, we aim to elucidate the molecular mechanism that leads to the overexpression of miR-224 in HCC. We examined the transcript expression of miR-224 and neighboring miR-452 and genes on chromosome Xq28 in tumor and paired adjacent nontumorous tissues from 100 patients with HCC and found that miR-224 is coordinately up-regulated with its neighboring microRNA (miRNA) and genes. This coordinated up-regulation of miRNAs and genes at the Xq28 locus can be mimicked in nontransformed immortalized human liver cells by the introduction of histone deacetylase (HDAC) inhibitors, which resulted in a corresponding increase in histone H3 acetylation in this region. This miR-224-residing locus in Xq28 is reciprocally regulated by HDAC1, HDAC3, and histone acetylase protein, E1A binding protein p300 (EP300). Notably, in HCC tumors that significantly overexpress microRNA-224, EP300 is also overexpressed and displays increased binding to the Xq28 locus. In transformed HCC cells, high miR-224 expression can be attenuated through the inhibition of EP300, using either siRNA or the specific drug C646. In summary, overexpression of EP300 may account, in part, for the up-regulation of miR-224 expression in patients with HCC.

Gankyrin-mediated dedifferentiation facilitates the tumorigenicity of rat hepatocytes and hepatoma cells

Gankyrin is a critical oncoprotein overexpressed in human hepatocellular carcinoma (HCC). However, the mechanism underlying gankyrin-mediated hepatocarcinogenesis remains elusive. Herein, we provide evidence that gankyrin expression was progressively elevated in liver fibrosis, cirrhosis, and HCC. Levels of gankyrin expression were closely associated with the dedifferentiation status of hepatoma in patients. Decrease of hepatocyte characteristic markers and increase of cholangiocyte-specific markers were observed in rat primary hepatocytes with enforced gankyrin expression and diethylnitrosamine (DEN)-triggered rat hepatocarcinogenesis. Overexpression of gankyrin also attenuated the hepatic function of primary hepatocytes, which further suggests that gankyrin promotes the dedifferentiation of hepatocytes. Moreover, elevated expression of gankyrin closely correlated with the expression of HCC stem/progenitor cell markers in DEN-triggered hepatocarcinogenesis and human HCCs. Hepatoma cells derived from suspension-cultured spheroids exhibited a higher gankyrin level, and enforced gankyrin expression in hepatoma cells remarkably enhanced cluster of differentiation (CD)133, CD90, and epithelial cellular adhesion molecule expression, indicating a role of gankyrin in hepatoma cell dedifferentiation and the generation of hepatoma stem/progenitor cells. In contrast, down-regulation of gankyrin in hepatoma cells by lentivirus-mediated microRNA delivery significantly improved their differentiation status and attenuated malignancy. Interference of gankyrin expression in hepatoma cells also diminished the proportion of cancer stem/progenitor cells and their self-renewal capacity. Furthermore, gankyrin was found to bind hepatocyte nuclear factor 4α (HNF4α), which determines hepatocyte differentiation status and enhances proteasome-dependent HNF4α degradation in hepatoma cells. The inverse correlation of gankyrin and HNF4α was further confirmed in primary hepatocytes, DEN-induced hepatocarcinogenesis, and human HCCs.

CONCLUSION

Gankyrin-mediated dedifferentiation of hepatocytes and hepatoma cells via, at least partially, down-regulation of HNF4α facilitates HCC development, and interference of gankyrin expression could be a novel strategy for HCC prevention and differentiation therapy.

p28GANK overexpression accelerates hepatocellular carcinoma invasiveness and metastasis via phosphoinositol 3-kinase/AKT/hypoxia-inducible factor-1α pathways

The overall survival of patients with hepatocellular carcinoma (HCC) remains poor, and the molecular mechanisms underlying HCC progression and aggressiveness are unclear. Here, we report that increased expression of p28(GANK) (Gankyrin, PSMD10, or p28) in human HCC predicts poor survival and disease recurrence after surgery. Patients with HCC who have large tumors, with vascular invasion and intrahepatic or distant metastasis, expressed high levels of p28(GANK) . Invasive tumors overexpressing p28(GANK) were featured by active epithelial-mesenchymal transition (EMT), and exhibited increased angiogenesis associated with vascular endothelial growth factor overexpression, whereas silencing p28(GANK) expression attenuated EMT and motility/invasion of tumor cells. The p28(GANK) activates phosphoinositide 3-kinase (PI3K)-V-akt Murine Thymoma Viral Oncogene Homolog (AKT)-hypoxia-inducible factor 1α (HIF-1α) signaling to promote TWIST1, vascular endothelial growth factor, and metalloproteinase 2 expression. Suppression of the PI3K-AKT-HIF-1α pathway interfered with p28(GANK) -mediated EMT and invasion. Consistently, we detected a significant correlation between p28(GANK) expression and p-AKT levels in a cohort of HCC biopsies, and the combination of these two parameters is a more powerful predictor of poor prognosis.

CONCLUSION

These results present novel mechanistic insight into a critical role of p28(GANK) in HCC progression and metastasis.

Intracellular signaling and hepatocellular carcinoma

Liver cancer is the fifth most common cancer and the third most common cause of cancer related death in the world. The recent development of new techniques for the investigations of global change in the gene expression, signaling pathways and wide genome binding has provided novel information for the mechanisms underlying liver cancer progression. Although these studies identified gene expression signatures in hepatocellular carcinoma, the early steps of the development of hepatocellular carcinomas (HCC) are not well understood. The development of HCC is a multistep process which includes the progressive alterations of gene expression leading to the increased proliferation and to liver cancer. This review summarizes recent progress in the identification of the key steps of the development of HCC with the focus on early events of carcinogenesis and on the role of translational and epigenetic alterations in the development of HCC. Quiescent stage of the liver is supported by several tumor suppressor proteins including p53, Rb and C/EBPα. Studies with chemical models of liver carcinogenesis and with human HCC have shown that the elevation of gankyrin is responsible for the elimination of these three proteins at early steps of carcinogenesis. Later stages of progression of the liver cancer are associated with alterations in many signaling pathways including translation which leads to epigenetic silencing/activation of many genes. Particularly, recent reports suggest a critical role of histone deacetylase 1, HDAC1, in the development of HCC through the interactions with transcription factors such as C/EBP family proteins.

Gankyrin promotes the proliferation of human pancreatic cancer

Previous studies in our laboratory have suggested that gankyrin expression is correlated with a malignant phenotype in colorectal cancer. Here, we investigated the possible role of gankyrin in pancreatic carcinogenesis. Gankyrin expression was significantly increased in pancreatic cancer compared to non-cancerous tissues. This expression significantly enhanced cancer cell proliferation and growth in vitro and in vivo. Suppression of gankyrin downregulated cyclin A, cyclin D1, cyclin E, CDK2, CDK4, PCNA and p-Rb but upregulated p27, Rb and p53. However, gankyrin overexpression led to opposite results. Thus, gankyrin could enhance pancreatic cancer cell proliferation by promoting cell cycle progression and p53 degradation.

Gankyrin Oncoprotein: Structure, Function, and Involvement in Cancer

Gankyrin, a newly defined oncoprotein also known as PSMD10 and P28, functions as a dual-negative regulator of the two most prominent tumor suppressor pathways, the CDK/pRb and HDM2/P53 pathways. Its aberrant expression has been prevalently found in human hepatocellular carcinomas (HCC) and esophagus squamous cell carcinomas (ESCC), indicative of the potential of gankyrin as a rational diagnostic and therapeutic target in cancers. Here, we review the unique structural features and functional diversity of gankyrin, and discuss its implication in cancer diagnostics and therapeutics from the perspective of chemical biology.

Hepatitis C virus-induced hepatocarcinogenesis

Although there is strong evidence that hepatitis C virus (HCV) is one of the leading causes of hepatocellular carcinoma (HCC), there is still much to understand regarding the mechanism of HCV-induced transformation. While liver fibrosis resulting from long-lasting chronic inflammation and liver regeneration resulting from immune-mediated cell death are likely factors that contribute to the development of HCC, the direct role of HCV proteins remains to be determined. In vitro studies have shown that HCV expression may interfere with cellular functions that are important for cell differentiation and cell growth. However, most studies were performed in artificial models which can only give clues for potential mechanisms that need to be confirmed in more relevant models. Furthermore, the difficulty to identify HCV proteins and infected liver cells in patients, contributes to the complexity of our current understanding. For these reasons, there is currently very little experimental evidence for a direct oncogenic role of HCV. Further studies are warranted to clarify these issues.

p28GANK inhibits endoplasmic reticulum stress-induced cell death via enhancement of the endoplasmic reticulum adaptive capacity

It has been shown that oncoprotein p28(GANK), which is consistently overexpressed in human hepatocellular carcinoma (HCC), plays a critical role in tumorigenesis of HCC. However, the underlying mechanism remains unclear. Here, we demonstrated that p28(GANK) inhibits apoptosis in HCC cells induced by the endoplasmic reticulum (ER) stress. During ER stress, p28(GANK) enhances the unfolded protein response, promotes ER recovery from translational repression, and thereby facilitates cell's ability to cope with the stress conditions. Furthermore, p28(GANK) upregulates glucose-regulated protein 78 (GRP78), a key ER chaperone protein, which subsequently enhances the ER folding capacity and promotes recovery from ER stress. We also demonstrated that p28(GANK) increases p38 mitogen-activated protein kinase and Akt phosphorylation, and inhibits nuclear factor kappa B (NF-kappaB) activation under ER stress, which in turn contributes to GRP78 upregulation. Taken together, our results indicate that p28(GANK) inhibits ER stress-induced apoptosis in HCC cells, at least in part, by enhancing the adaptive response and GRP78 expression. We propose that p28(GANK) has potential implications for HCC progression under the ER stress conditions.

The regulation of non-coding RNA expression in the liver of mice fed DDC

Mallory-Denk bodies (MDBs) are found in the liver of patients with alcoholic and chronic nonalcoholic liver disease, and hepatocellular carcinoma (HCC). Diethyl 1,4-dihydro-2,4,6,-trimethyl-3,5-pyridinedicarboxylate (DDC) is used as a model to induce the formation of MDBs in mouse liver. Previous studies in this laboratory showed that DDC induced epigenetic modifications in DNA and histones. The combination of these modifications changes the phenotype of the MDB forming hepatocytes, as indicated by the marker FAT10. These epigenetic modifications are partially prevented by adding to the diet S-adenosylmethionine (SAMe) or betaine, both methyl donors. The expression of three imprinted ncRNA genes was found to change in MDB forming hepatocytes, which is the subject of this report. NcRNA expression was quantitated by real-time PCR and RNA FISH in liver sections. Microarray analysis showed that the expression of three ncRNAs was regulated by DDC: up regulation of H19, antisense Igf2r (AIR), and down regulation of GTL2 (also called MEG3). S-adenosylmethionine (SAMe) feeding prevented these changes. Betaine, another methyl group donor, prevented only H19 and AIR up regulation induced by DDC, on microarrays. The results of the SAMe and betaine groups were confirmed by real-time PCR, except for AIR expression. After 1 month of drug withdrawal, the expression of the three ncRNAs tended toward control levels of expression. Liver tumors that developed also showed up regulation of H19 and AIR. The RNA FISH approach showed that the MDB forming cells' phenotype changed the level of expression of AIR, H19 and GTL2, compared to the surrounding cells. Furthermore, over expression of H19 and AIR was demonstrated in tumors formed in mice withdrawn for 9 months. The dysregulation of ncRNA in MDB forming liver cells has been observed for the first time in drug-primed mice associated with liver preneoplastic foci and tumors.

Overexpression of a new gene P28GANK confers multidrug resistance of gastric cancer cells

Here we investigated the roles of P28GANK in multidrug resistance of gastric cancer cells and the possible mechanisms. We constructed the siRNA vector of P28GANK and transfected it into human vincristine-resistant gastric adenocarcinoma cell line SGC7901/VCR. Down-regulation of P28GANK could enhance the sensitivity of SGC7901/VCR cells towards anticancer drugs and could decrease the capacity of cells to efflux adriamycin. P28GANK could down-regulate the expression of P-gp, but not affect MRP or GST. In vivo experiment also confirmed our above results. Further study of the biological functions of P28GANK might be helpful for understanding the mechanisms of MDR in gastric cancer.

Hepatocellular carcinoma and the ubiquitin-proteasome system

Hepatocellular carcinoma is one of the largest causes of cancer-related deaths worldwide for which there are very limited treatment options that are currently effective. The ubiquitin-proteasome system has rapidly become acknowledged as both critical for normal cellular function and a frequent target of de-regulation leading to disease. This review appraises the evidence linking the ubiquitin-proteasome system with this devastatingly intractable cancer and asks whether it may prove to be fertile ground for the development of novel therapeutic interventions against hepatocellular carcinoma.

Alpha-fetoprotein and other tumour-associated antigens for immunotherapy of hepatocellular cancer

BACKGROUND

Hepatocellular carcinoma (HCC) is a leading cause of cancer death, with few treatment options for advanced disease.

OBJECTIVES

Here, we review the aetiology of HCC and focus on recent data on tumour-associated antigens (TAA) for HCC, their functions and potential use as immunological targets for immune-based therapy for HCC. In addition, we examine some aspects of antigen presentation within the liver.

RESULTS/CONCLUSIONS

alpha-Fetoprotein (AFP) has been investigated for many years as a TAA, and has been tested in recent clinical trials. More recently, additional TAA have been identified and new therapeutic approaches have been investigated which may be testable clinically in this difficult disease setting.

Harnessing the RNA interference pathway to advance treatment and prevention of hepatocellular carcinoma

Primary liver cancer is the fifth most common malignancy in the world and is a leading cause of cancer-related mortality. Available treatment for hepatocellular carcinoma (HCC), the commonest primary liver cancer, is rarely curative and there is a need to develop therapy that is more effective. Specific and powerful gene silencing that can be achieved by activating RNA interference (RNAi) has generated enthusiasm for exploiting this pathway for HCC therapy. Many studies have been carried out with the aim of silencing HCC-related cellular oncogenes or the hepatocarcinogenic hepatitis B virus (HBV) and hepatitis C virus (HCV). Proof of principle studies have demonstrated promising results, and an early clinical trial assessing RNAi-based HBV therapy is currently in progress. Although the data augur well, there are several significant hurdles that need to be overcome before the goal of RNAi-based therapy for HCC is realized. Particularly important are the efficient and safe delivery of RNAi effecters to target malignant tissue and the limitation of unintended harmful non-specific effects.

Association of gankyrin protein expression with early clinical stages and insulin-like growth factor-binding protein 5 expression in human hepatocellular carcinoma

Gankyrin (also known as PSMD10) is a liver oncoprotein that interacts with multiple proteins including MDM2 and accelerates degradation of the tumor suppressors p53 and Rb. We produced a monoclonal anti-gankyrin antibody and immunohistochemically assessed the clinicopathological significance of gankyrin overexpression in 43 specimens of human hepatocellular carcinoma (HCC). Specific cytoplasmic staining for gankyrin was observed in 62.8% (27/43) of HCCs, which was significantly associated with low TNM stage (P = 0.004), no capsular invasion (P = 0.018), no portal venous invasion (P = 0.008), and no intrahepatic metastasis (P = 0.012). The cumulative survival rate of patients with gankyrin-positive HCC was significantly higher than that with gankyrin-negative HCC (P = 0.037). p53 and MDM2 were positively stained by antibodies in 30.2% and 23.3%, respectively, of HCCs, but neither was inversely associated with gankyrin expression. In the Huh-7 human HCC cell line, overexpression of gankyrin up-regulated expression of insulin-like growth factor binding protein 5 (IGFBP-5), whereas suppression of gankyrin expression by siRNA down-regulated it. Supression of IGFBP-5 expression inhibited proliferation of Huh-7 cells as well as U-2 OS osteosarcoma cells. In HCC specimens, positive staining for IGFBP-5 was observed by immunohistochemistry in 41.9% (18/43), and the level of expression was significantly correlated with that of gankyrin (rho = 0.629, P < 0.001).

CONCLUSION

These results suggest that gankyrin plays an oncogenic role(s) mainly at the early stages of human hepatocarcinogenesis, and that IGFBP-5 inducible by gankyrin overexpression may be involved in it.