Autophagy in hepatocellular carcinomas: from pathophysiology to therapeutic response

Acetazolamide suppresses the progression of hepatocellular carcinoma induced by diethylnitrosamine in Wistar albino rats

Hepatocellular carcinoma (HCC) continues to be the most prevalent type of liver cancer worldwide. Diethylnitrosamine (DEN)-induced HCC is an extensively used hepatic cancer model in experimental animals. Acetazolamide (AZA) is a carbonic anhydrase enzyme inhibitor. This study aimed to assess the therapeutic mechanism of AZA against DEN-induced HCC. Thirty male Wistar albino rats were divided equally into three groups. Group I (C): control group, Group II (HCC): DEN-induced HCC, and Group III (HCC/AZA): AZA-treated HCC. Verification of the HCC induced by DEN was confirmed by elevated liver enzymes' activities, and increased α-fetoprotein (AFP) levels, as well as distinct liver architecture changes. On the other hand, the AZA-treated HCC group experienced decreases in the activities of serum liver enzymes and AFP levels, as well as, regulated liver architecture. Additionally, it downregulated p-p38 MAPK/p-JNK1/JNK2/p-C-Jun/p-NF-κB p65 protein expressions. Moreover, it ameliorated autophagy by controlling the expression of the p-AMPK/p-mTOR1/LC3 I/II proteins. Furthermore, it downregulated the relative gene expressions of carbonic anhydrase-IX (CAIX) and hexokinase-II (HKII). Histopathological examination of AZA-treated HCC liver tissues supported these findings. Conclusion: AZA provides a new dimension in ameliorating experimentally induced HCC through regulation of hepatic biomarkers, antioxidant status, inflammatory markers, and autophagy, mediated by amelioration of CAIX and HKII gene expressions.

Expression of LC3A, LC3B and p62/SQSTM1 autophagy proteins in hepatocellular carcinoma (HCC) tissues and the predicted microRNAs involved in the autophagy-related pathway

BACKGROUND

Autophagy plays multifaceted roles in regulating hepatocellular carcinoma (HCC) and the mechanisms involved are under-explored. Regulatory microRNAs (miRNAs) have been reported to target autophagy proteins but their roles in HCC is not well studied. Using HCC patient tissues, this study aims to investigate the association of autophagy with several clinicopathological parameters as well as identifying the autophagy-related miRNAs and the possible pathways.

METHODS AND RESULTS

Autophagy level in the HCC patient-derived cancer and non-cancer tissues was determined by immunohistochemistry (IHC) targeting SQSTM1, LC3A and LC3B proteins. Significance tests of clinicopathological variables were tested using the Fisher's exact or Chi-square tests. Gene and miRNA expression assays were carried out and analyzed using Nanostring platform and software followed by validation of other online bioinformatics tools, namely String and miRabel. Autophagy expression was significantly higher in cancerous tissues compared to adjacent non-cancer tissues. High LC3B expression was associated with advanced tumor histology grade and tumor location. Nanostring gene expression analysis revealed that SQSTM1, PARP1 and ATG9A genes were upregulated in HCC tissues compared to non-cancer tissues while SIRT1 gene was downregulated. These genes are closely related to an autophagy pathway in HCC. Further, using miRabel tool, three downregulated miRNAs (hsa-miR-16b-5p, hsa-miR-34a-5p, and hsa-miR-660-5p) and one upregulated miRNA (hsa-miR-539-5p) were found to closely interact with the abovementioned autophagy-related genes. We then mapped out the possible pathway involving the genes and miRNAs in HCC tissues.

CONCLUSIONS

We conclude that autophagy events are more active in HCC tissues compared to the adjacent non-cancer tissues. We also reported the possible role of several miRNAs in regulating autophagy-related genes in the autophagy pathway in HCC. This may contribute to the development of potential therapeutic targets for improving HCC therapy. Future investigations are warranted to validate the target genes reported in this study using a larger sample size and more targeted molecular technique.

Advances in the Pathogenesis of Metabolic Liver Disease-Related Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the sixth most common cancer globally and the primary cause of death in cancer cases, with significant public health concern worldwide. Despite the overall decline in the incidence and mortality rates of HCC in recent years in recent years, the emergence of metabolic liver disease-related HCC is causing heightened concern, especially in countries like the United States, the United Kingdom, and P.R. China. The escalation of metabolic liver disease-related HCC is attributed to a combination of factors, including genetic predisposition, lifestyle choices, and changes in the living environment. However, the pathogenesis of metabolic liver disease-associated HCC remains imperfect. In this review, we encapsulate the latest advances and essential aspects of the pathogenesis of metabolic liver disease-associated HCC, including alcoholic liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), and inherited metabolic liver diseases.

Targeting lipophagy as a potential therapeutic strategy for nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is becoming an increasingly serious disease worldwide. Unfortunately, no specific drug has been approved to treat NAFLD. Accumulating evidence suggests that lipotoxicity, which is induced by an excess of intracellular triacylglycerols (TAGs), is a potential mechanism underlying the ill-defined progression of NAFLD. Under physiological conditions, a balance is maintained between TAGs and free fatty acids (FFAs) in the liver. TAGs are catabolized to FFAs through neutral lipolysis and/or lipophagy, while FFAs can be anabolized to TAGs through an esterification reaction. However, in the livers of patients with NAFLD, lipophagy appears to fail. Reversing this abnormal state through several lipophagic molecules (mTORC1, AMPK, PLIN, etc.) facilitates NAFLD amelioration; therefore, restoring failed lipophagy may be a highly efficient therapeutic strategy for NAFLD. Here, we outline the lipophagy phases with the relevant important proteins and discuss the roles of lipophagy in the progression of NAFLD. Additionally, the potential candidate drugs with therapeutic value targeting these proteins are discussed to show novel strategies for future treatment of NAFLD.

Serum Beclin 1 and autophagy-related protein-5 and the risk of hepatocellular carcinoma among cirrhotic hepatitis C patients

Background

The most common primary liver cancer in adults is hepatocellular carcinoma (HCC) which is commonly presented with a poor prognosis. Therefore, it is important to explore effective biomarkers and therapeutic targets for HCC patients. Autophagy is involved in the development and prevention of cancer. Mammalian Beclin-1 is needed for an autophagic vesicle in HCC. Autophagy-related protein-5 (ATG5) is an important molecule involved in cell death during autophagy. The objective is to investigate serum ATG 5 and Beclin 1 levels in HCV-induced liver cirrhosis with and without HCC. The study was conducted on 80 individuals classified into 3 groups:

Results

Serum ATG 5 was significantly lower in HCC than liver cirrhosis patients. Serum Beclin 1 was significantly higher in HCC than liver cirrhosis patients. A cutoff value of < 95.7 and > 5.3 of serum ATG5 and Beclin 1 could be suggested for diagnosis of HCC among patients with HCV-related cirrhosis.

Conclusion

Serum Beclin 1 and ATG 5 could be used as a novel diagnostic marker for HCC. Moreover, scoring of serum BECLIN 1, ATG 5, and cachexia might be a future promising tool to predict the risk of HCC development.

Identification of an autophagy-related gene signature predicting overall survival for hepatocellular carcinoma

The poor prognosis of hepatocellular carcinoma (HCC) calls for the development of accurate prognostic models. The growing number of studies indicating a correlation between autophagy activity and HCC indicates there is a commitment to finding solutions for the prognosis of HCC from the perspective of autophagy. We used a cohort in The Cancer Genome Atlas (TCGA) to evaluate the expression of autophagy-related genes in 371 HCC samples using univariate Cox and lasso Cox regression analysis, and the prognostic features were identified. A prognostic model was established by combining the expression of selected genes with the multivariate Cox regression coefficient of each gene. Eight autophagy-related genes were selected as prognostic features of HCC. We established the HCC prognostic risk model in TCGA dataset using these identified prognostic genes. The model's stability was confirmed in two independent verification sets (GSE14520 and GSE36376). The model had a good predictive power for the overall survival (OS) of HCC (hazard ratio = 2.32, 95% confidence interval = 1.76-3.05, P<0.001). Moreover, the risk score computed by the model did not depend on other clinical parameters. Finally, the applicability of the model was demonstrated through a nomogram (C-index = 0.701). In the present study, we established an autophagy-related risk model having a high prediction accuracy for OS in HCC. Our findings will contribute to the definition of prognosis and establishment of personalized therapy for HCC patients.

In Vitro Effects of Lithium Carbonate on Cell Cycle, Apoptosis, and Autophagy in Hepatocellular Carcinoma-29 Cells

We studied the effects of lithium carbonate on the cell cycle, apoptosis, and autophagy in hepatocellular carcinoma-29 cells (HCC-29) in vitro. Flow cytofluorometry analysis revealed accumulation of G2/M-phase HCC-29 cells and increase in the number of apoptotic cells in 48 h after administration of 5 mM lithium carbonate. Induction of autophagy in HCC-29 cells was detected by transmission electron microscopy and immunofluorescence staining. Thus, lithium carbonate produces an antitumor effect by arresting cell cycle in the G2/M-phase and induction of apoptosis and autophagy in HCC-29 cells, which confirms the lithium potential as a promising drug for the treatment of hepatocellular carcinoma.

The Role of Autophagy in Liver Cancer: Crosstalk in Signaling Pathways and Potential Therapeutic Targets

Autophagy is an evolutionarily conserved lysosomal-dependent pathway for degrading cytoplasmic proteins, macromolecules, and organelles. Autophagy-related genes (Atgs) are the core molecular machinery in the control of autophagy, and several major functional groups of Atgs coordinate the entire autophagic process. Autophagy plays a dual role in liver cancer development via several critical signaling pathways, including the PI3K-AKT-mTOR, AMPK-mTOR, EGF, MAPK, Wnt/β-catenin, p53, and NF-κB pathways. Here, we review the signaling pathways involved in the cross-talk between autophagy and hepatocellular carcinoma (HCC) and analyze the status of the development of novel HCC therapy by targeting the core molecular machinery of autophagy as well as the key signaling pathways. The induction or the inhibition of autophagy by the modulation of signaling pathways can confer therapeutic benefits to patients. Understanding the molecular mechanisms underlying the cross-link of autophagy and HCC may extend to translational studies that may ultimately lead to novel therapy and regimen formation in HCC treatment.

Effect of Combined Sorafenib/Cisplatinum Treatment on the Autophagy and Proliferation of Hepatocellular Carcinoma hepG2 Cells in Vitro

Objective:

To explore the effect of combined Sorafenib/ cisplatinum treatment on the autophagy and proliferation of hepatocellular carcinoma (HepG2) cells in vitro.

Methods:

HepG2 cells were cultured and treated with different concentrations of Sorafenib, cisplatinum, or a combination of both over a 24-hour period. Cell proliferation was evaluated using a CCK8 assay, and the mRNA expression of the autophagy-related proteins AKT, mTOR, and LC3 were detected using quantitative PCR (qPCR). AKT, pAKT (Ser473), mTOR, pmTOR (Ser2448), LC3I, and LC3II protein expression levels were evaluated by western blot.

Results:

We found that the survival rate of HepG2 cells was 47.42% when treated with Sorafenib (10 μmol/L) monotherapy, and 46.04% when treated with cisplatinum (10 mg/L) monotherapy. When Sorafenib(10 μmol/L) was combined with cisplatinum (10 mg/L), the cellular proliferation and survival rate was only 16.71% ( P <0.05). qPCR and western blot revealed that a combination of Sorafenib (10 μmol/L) and cisplatinum (10 mg/L) reduced the transcription and protein expression of autophagy-related AKT and mTOR but increased that of LC3 (P <0.05).

Conclusion:

Combining Sorafenib and cisplatinum can effectively induce cell autophagy and reduce cellular proliferation via the PI3K/AKT/mTOR signal pathway.

The signaling axis of Rac1-TFEB regulates autophagy and tumorigenesis

Macroautophagy (hereafter referred to as autophagy) plays essential roles in cellular and organismal homeostasis. Transcription factor EB (TFEB) is a master regulator of autophagy and lysosome biogenesis. It is not fully understood how the function of TFEB in autophagy pathway is regulated. Here, we show that Rac1 GTPase is a negative modulator of autophagy by targeting TFEB. Mechanistically, Rac1 reduces autophagy flux by repressing the expressing of autophagy genes. Further investigation revealed that under nutrient-rich conditions, mammalian target of rapamycin (mTOR) phosphorylates TFEB to facilitate the interaction between Rac1 and TFEB. Biochemical dissection uncovered that guanosine 5'-triphosphate (GTP)-bound form of Rac1 selectively interacts with phosphorylated TFEB. This inhibitory interaction prevents the dephosphorylation and nucleus translocation of TFEB, which hampers the transcriptional activation of autophagy-related genes. Furthermore, Rac1-TFEB axis appeared to be important for tumorigenesis, as overexpression of dephosphorylated mutant of TFEB was able to delay the tumor growth driven by Rac1 overexpression. Together, this study not only elucidates a previously uncharacterized autophagy regulation mechanism involving Rac1 and TFEB under physiological and pathological conditions but also suggests a strategy to treat cancers that are driven by Rac1 overexpression.

Effect of Oleanolic Acid on Apoptosis and Autophagy of SMMC-7721 Hepatoma Cells

BACKGROUND Liver cancer is a common cancer with high morbidity and mortality. Due to the large toxic side effects of chemotherapeutic drugs and the overexpression of multidrug resistance genes in liver cancer, no effective chemotherapeutic drug has yet been found. Therefore, the search for a highly effective, low-toxic, and safe natural anticancer therapy is a hot issue. MATERIAL AND METHODS SMMC-7721 cells (a hepatocellular carcinoma cell line) were treated with different concentrations of oleanolic acid (OA) plus autophagy inhibitor 3-methyladenine (3-MA) (3-MA+OA) or chloroquine (CQ) plus OA (CQ+OA). We used MTT and Hoechst 33258 staining methods to determine the proliferation and apoptotic effect of OA on cells. Flow cytometry was used to detect apoptosis. Mitochondrial function was assessed by measuring mitochondrial membrane potential and adenosine triphosphate (ATP) concentration. To evaluate the ability of OA on apoptosis and autophagy mechanisms on SMMC 7721 cells, the related protein expression for apoptosis, autophagy, and the autophagic pathway were detected and analyzed by western blot. RESULTS OA can inhibit and induce apoptosis of SMMC-7721 in a dose-dependent manner. Compared with the control group, OA significantly reduced the intracellular mitochondrial membrane potential, and the intracellular ATP concentration was also significantly reduced. Moreover, OA reduced the expression of p-Akt and p-mTOR. The expression of p62 was decreased, and LC3-II and Beclin-1 protein expression levels increased. After inhibiting autophagy with 3-MA or CQ, compared with OA alone, cell mitochondrial membrane potential and ATP concentration were significantly reduced, cell p62 expression was reduced, and LC3-II expression was increased, apoptosis-related protein Bax protein was increased, and Bcl-2 protein was decreased, which suggested that 3-MA or CQ treatment increased OA-induced apoptosis of SMMC-7721 cells. This suggested that OA activated autophagy of SMMC-7721 cells in a protective autophagic manner. CONCLUSIONS The study findings suggest that OA combined with autophagy inhibitor 3-MA can better exert its anticancer effect.

Integrated stress response in hepatitis C promotes Nrf2-related chaperone-mediated autophagy: A novel mechanism for host-microbe survival and HCC development in liver cirrhosis

The molecular mechanism(s) how liver damage during the chronic hepatitis C virus (HCV) infection evolve into cirrhosis and hepatocellular carcinoma (HCC) is unclear. HCV infects hepatocyte, the major cell types in the liver. During infection, large amounts of viral proteins and RNA replication intermediates accumulate in the endoplasmic reticulum (ER) of the infected hepatocyte, which creates a substantial amount of stress response. Infected hepatocyte activates a different type of stress adaptive mechanisms such as unfolded protein response (UPR), antioxidant response (AR), and the integrated stress response (ISR) to promote virus-host cell survival. The hepatic stress is also amplified by another layer of innate and inflammatory response associated with cellular sensing of virus infection through the production of interferon (IFN) and inflammatory cytokines. The interplay between various types of cellular stress signal leads to different forms of cell death such as apoptosis, necrosis, and autophagy depending on the intensity of the stress and nature of the adaptive cellular response. How do the adaptive cellular responses decode such death programs that promote host-microbe survival leading to the establishment of chronic liver disease? In this review, we discuss how the adaptive cellular response through the Nrf2 pathway that promotes virus and cell survival. Furthermore, we provide a glimpse of novel stress-induced Nrf2 mediated compensatory autophagy mechanisms in virus-cell survival that degrade tumor suppressor gene and activation of oncogenic signaling during HCV infection. Based on these facts, we hypothesize that the balance between hepatic stress, inflammation and different types of cell death determines liver disease progression outcomes. We propose that a more nuanced understanding of virus-host interactions under excessive cellular stress may provide an answer to the fundamental questions why some individuals with chronic HCV infection remain at risk of developing cirrhosis, cancer and some do not.

Dissecting pharmacological effects of chloroquine in cancer treatment: interference with inflammatory signaling pathways

Chloroquines are 4-aminoquinoline-based drugs mainly used to treat malaria. At pharmacological concentrations, they have significant effects on tissue homeostasis, targeting diverse signaling pathways in mammalian cells. A key target pathway is autophagy, which regulates macromolecule turnover in the cell. In addition to affecting cellular metabolism and bioenergetic flow equilibrium, autophagy plays a pivotal role at the interface between inflammation and cancer progression. Chloroquines consequently have critical effects in tissue metabolic activity and importantly, in key functions of the immune system. In this article, we will review the work addressing the role of chloroquines in the homeostasis of mammalian tissue, and the potential strengths and weaknesses concerning their use in cancer therapy.

Harmonized Autophagy Versus Full-Fledged Hepatitis B Virus: Victorious or Defeated

Autophagy is a finely tuned process in the regulation of innate immunity to avoid excessive inflammatory responses and inflammasome signaling. In contrast, the results of recent studies have shown that autophagy may disease-dependently contribute to the pathogenesis of liver diseases, such as fibrosis, cirrhosis, and hepatocellular carcinoma (HCC) during hepatitis B virus (HBV) infection. HBV has learned to subvert the cell's autophagic machinery to promote its replication. Given the great impact of the autophagy mechanism on the HBV infection and HCC, recognizing these factors may be offered new hope for human intervention and treatment of chronic HBV. This review focuses on recent findings viewing the dual role of autophagy plays in the pathogenesis of HBV infected hepatocytes.

Autophagy during viral infection - a double-edged sword

Autophagy is a powerful tool that host cells use to defend against viral infection. Double-membrane vesicles, termed autophagosomes, deliver trapped viral cargo to the lysosome for degradation. Specifically, autophagy initiates an innate immune response by cooperating with pattern recognition receptor signalling to induce interferon production. It also selectively degrades immune components associated with viral particles. Following degradation, autophagy coordinates adaptive immunity by delivering virus-derived antigens for presentation to T lymphocytes. However, in an ongoing evolutionary arms race, viruses have acquired the potent ability to hijack and subvert autophagy for their benefit. In this Review, we focus on the key regulatory steps during viral infection in which autophagy is involved and discuss the specific molecular mechanisms that diverse viruses use to repurpose autophagy for their life cycle and pathogenesis.

Autophagy is crucial for innate and adaptive antiviral immunity; in turn, viruses evade and subvert autophagy to support their replication and pathogenesis. In this Review, Choi, Bowman and Jung discuss the molecular mechanisms that govern autophagy during host–virus interactions.

Ultrastructural Changes in Hepatocellular Carcinoma-29 Cells after Treatment with Lithium Carbonate

We studied the effect of lithium carbonate on hepatocellular carcinoma-29 cells in CBA male mice after injection in a dose of 20 mM along the tumor periphery. Transmission electron microscopy revealed a decrease in the volume density of the granular endoplasmic reticulum in the cell cytoplasm and an increase in the total numerical and volume density of autophagosomes and autolysosomes and zones of destruction of intracellular organelles. The ability of lithium carbonate to activate intracellular degradation processes in tumor cells and to stimulate cell death can be used to develop new combined strategies in the chemotherapy for hepatocellular carcinoma.

RNA Binding Protein HuR Promotes Autophagosome Formation by Regulating Expression of Autophagy-Related Proteins 5, 12, and 16 in Human Hepatocellular Carcinoma Cells

Autophagy is a process of lysosomal self-degradation of cellular components by forming autophagosomes. Autophagosome formation is an essential process in autophagy and is fine-tuned by various autophagy-related gene (ATG) products, including ATG5, ATG12, and ATG16. Although several reports have shown that numerous factors affect multiple levels of gene regulation to orchestrate cellular autophagy, the detailed mechanism of autophagosome formation still needs further investigation. In this study, we demonstrate that the RNA binding protein HuR (human antigen R) performs an essential function in autophagosome formation. We observe that HuR silencing leads to inhibition of autophagosome formation and autophagic flux in liver cells. Ribonucleoprotein immunoprecipitation (RIP) assay allows the identification of ATG5, ATG12, and ATG16 mRNAs as the direct targets of HuR. We further show that HuR mediates the translation of ATG5, ATG12, and ATG16 mRNAs by binding to their 3' untranslated regions (UTRs). In addition, we show that HuR expression positively correlates with the levels of ATG5 and ATG12 in hepatocellular carcinoma (HCC) cells. Collectively, our results suggest that HuR functions as a pivotal regulator of autophagosome formation by enhancing the translation of ATG5, ATG12, and ATG16 mRNAs and that augmented expression of HuR and ATGs may participate in the malfunction of autophagy in HCC cells.

The MTOR signaling pathway regulates macrophage differentiation from mouse myeloid progenitors by inhibiting autophagy

Understanding of the mechanism for myeloid differentiation provides important insights into the hematopoietic developmental processes. By using an ESC-derived myeloid progenitor cell model, we found that CSF2/GM-CSF triggered macrophage differentiation and activation of the MTOR signaling pathway. Activation or inhibition of the MTOR signaling enhanced or attenuated macrophage differentiation, respectively, suggesting a critical function. We further showed that macroautophagy/autophagy was inhibited with the addition of CSF2. Furthermore, pharmacological inhibition and genetic modification of autophagy enhanced macrophage differentiation and rescued the inhibitory effect on differentiation caused by MTOR inhibition. Thus, the MTOR signaling pathway regulates macrophage differentiation of myeloid progenitors by inhibiting autophagy. Our results provide new insights into the mechanisms for myeloid differentiation and may prove useful for therapeutic applications of hematopoietic and myeloid progenitor cells. Abbreviations: 2-DG: 2-deoxy-D-glucose; ADGRE1/F4/80: adhesion G protein-coupled receptor E1; BM: bone marrow; CQ: chloroquine; ECAR: extracellular acidification rate; ESC: embryonic stem cell; CSF2/GM-CSF: colony stimulating factor 2; CSF3/G-CSF: colony stimulating factor 3; HPC: hematopoietic progenitor cell; ITGAM/CD11b: integrin alpha M; LPS: lipopolysaccharide; MFI: median fluorescence intensity; MTOR: mechanistic target of rapamycin kinase; RPS6KB1/p70S6K1: ribosomal protein S6 kinase, polypeptide 1; shRNA: short hairpin RNA; SQSTM1/p62: sequestosome 1.

Chaperone-mediated autophagy compensates for impaired macroautophagy in the cirrhotic liver to promote hepatocellular carcinoma

Macroautophagy and chaperone-mediated autophagy (CMA) represent two major lysosomal degradation processes and often compensate for one another to facilitate cell survival. The aim of this study was to determine whether these autophagy pathways could compensate for one another to promote HCC cell survival in the cirrhotic liver. Analysis of normal liver tissue showed no expression of glypican-3 or p62 proteins, suggesting that macroautophagy is the major contributor to autophagic flux under non-pathological conditions. Of 46 cirrhotic livers with HCC examined, 39 (84%) of HCCs showed increased expression of p62, and 36 (78%) showed increased expression of glypican-3, while adjacent non-tumorous hepatocytes were negative for expression of p62 and glypican-3, similar to normal liver tissue. These results suggest that macroautophagy flux is impaired in HCC. Furthermore, more than 95% of HCCs showed altered expression of LAMP-2A compared to the surrounding non-tumorous cirrhotic liver, consistent with induction of CMA in HCC. Elevated expression of glucose-regulated protein 78 (GRP78) and heat shock cognate protein (Hsc70) were detected in 100% of HCC and adjacent non-tumorous cirrhotic livers, suggesting that unresolved ER-stress is associated with HCC risk in liver cirrhosis. Interestingly, inhibition of lysosomal degradation using hydroxychloroquine (HCQ) induced expression of the tumor suppressor p53, promoted apoptosis, and inhibited HCC growth, whereas activation of autophagy using an mTOR inhibitor (Torin1) promoted HCC growth. Results of this study suggest that induction of CMA compensates for the impairment of macroautophagy to promote HCC survival in the cirrhotic liver.

Dysregulation of autophagy in rat liver with mitochondrial DNA depletion induced by the nucleoside analogue zidovudine

The nucleoside reverse transcriptase inhibitor zidovudine (AZT), used in HIV infection treatment, induces mitochondrial DNA (mtDNA) depletion. A cause-effect relationship between mtDNA status alterations and autophagy has been reported. Both events are common in several liver diseases, including hepatocellular carcinoma. Here, we have studied autophagy activation in rat liver with mtDNA depletion induced by AZT administration in drinking water for 35 days. AZT at a concentration of 1 mg/ml, but not 0.5 mg/ml in the drinking water, decreased mtDNA levels in rat liver and extrahepatic tissues. In liver, mtDNA-encoded cytochrome c oxidase 1 protein levels were decreased. Although serum biomarkers of liver and kidney toxicity remained unaltered, β-hydroxybutyrate levels were increased in liver of AZT-treated rats. Moreover, autophagy was dysregulated at two levels: (i) decreased induction signalling of this process as indicated by increases in autophagy inhibitors activity (AKT/mTOR), and absence of changes (Beclin-1, Atg5, Atg7) or decreases (AMPK/ULK1) in the expression/activity of pro-autophagy proteins; and (ii) reduced autophagosome degradation as indicated by decreases in the lysosome abundance (LAMP2 marker) and the transcription factor TFEB controlling lysosome biogenesis. This resulted in increased autophagosome abundance (LC3-II marker) and accumulation of the protein selectively degraded by autophagy p62, and the transcription factor Nrf2 in liver of AZT-treated rats. Nrf2 was activated as indicated by the up-regulation of antioxidant target genes Nqo1 and Hmox-1. In conclusion, rat liver with AZT-induced mtDNA depletion presented dysregulations in autophagosome formation and degradation balance, which results in accumulation of these structures in parenchymal liver cells, favouring hepatocarcinogenesis.

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.

Deubiquitinase inhibitor b-AP15 activates endoplasmic reticulum (ER) stress and inhibits Wnt/Notch1 signaling pathway leading to the reduction of cell survival in hepatocellular carcinoma cells

b-AP15, a potent and selective inhibitor of the ubiquitin-specific peptidase 14 (USP14), displays in vitro and in vivo antitumor abilities on some types of cancer cells. However, the mechanism underlying its action is not well elucidated. The purposes of the present study are to observe the potential impacts of b-AP15 on cell survival of hepatocellular carcinoma cells and to investigate whether and how this compound inhibits some survival-promoting signaling pathways. We found that b-AP15 significantly decreased cell viability and increased cell apoptosis in a dose-dependent manner in hepatocellular carcinoma cells, along with the perturbation of cell cycle and the decreased expressions of cell cycle-related proteins. We also demonstrated that the endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) were enhanced by b-AP15 supplementation. The inhibition of ER stress/UPR only partly attenuated the cytotoxicity of b-AP15 on hepatocellular carcinoma cells. In addition, b-AP15 treatment inhibited Wnt/β-catenin and Notch1 signaling pathways, and suppressed phosphorylation of STAT3, Akt, and Erk1/2, which were not restored by the inhibition of ER stress/UPR. Furthermore, the expression levels of signaling molecules in Notch1 were reduced by specific inhibitor of Wnt/β-catenin pathway. Notably, either Wnt or Notch1 signaling inhibitor mitigated phosphorylation of STAT3, Akt, and Erk1/2, and mimicked the cytotoxicity of b-AP15 on hepatocellular carcinoma cells. These results clearly indicate that b-AP15 induced cytotoxic response to hepatocellular carcinoma cells by augmenting ER stress/UPR and inhibiting Wnt/Notch1 signaling pathways. This new finding provides a novel mechanism by which b-AP15 produces its antitumor therapeutic effects.

Investigating miRNA-661 and ATG4-B mRNA expression as potential biomarkers for hepatocellular carcinoma

AIM

We aimed to examine the statistical association between serum expression of miRNA 661 (miR-661) and ATG-4B mRNA and hepatocellular carcinoma (HCC) based on in silico data analysis followed by clinical validation.

PATIENTS & METHODS

Quantitative reverse-transcriptase real-time PCR was used to examine the expression of miR-661 and ATG-4B mRNA in the sera of HCC patients versus control.

RESULTS

The expression of miR-661 and ATG-4B mRNA was positive in 97.14 and 77.14%, respectively, in HCC patients. The survival analysis showed that ATG-4B mRNA was an independent prognostic factor.

CONCLUSION

Our data are the first report of its kind regarding the considerable clinical significance of miR-661 and ATG-4B mRNA in HCC patients.

Autophagy suppresses proliferation of HepG2 cells via inhibiting glypican-3/wnt/β-catenin signaling

Introduction

Autophagy plays an important role in the growth and survival of hepatocellular carcinoma (HCC) cells through several target proteins or signaling pathways. Glypican-3 (GPC3) is a new reliable HCC marker, which is involved in tumor growth in HCC, primarily mediated by wnt/β-catenin signaling.

Objective

The present study aimed to identify the role of autophagy in the proliferation of HepG2 cells through GPC3/wnt/β-catenin signaling.

Results and discussion

Results demonstrated that induction of autophagy by nutrition starvation and rapamycin treatment led to the downregulation of GPC3 expression in HepG2 cells, accompanied by the decreased expression of wnt downstream target genes (β-catenin, c-myc and cyclin D1). On the other hand, inhibition of autophagy by 3-methyl adenine (3-MA) could rescue rapamycin-directed downregulation of GPC3 and wnt/β-catenin target genes and augment the proliferation of HepG2 cells. Furthermore, interference of GPC3 by siRNA suppressed wnt/β-catenin signaling and attenuated 3-MA stimulation of HepG2 cell proliferation. More interestingly, the mRNA of GPC3 remained unchanged when the protein levels of GPC3 were decreased by autophagy activation, suggesting that induction of autophagy may accelerate the degradation of GPC3.

Conclusion

These results suggest that autophagy suppresses proliferation of HepG2 cells partially by inhibition of GPC3/wnt/β-catenin signaling.

Interpreting lipoproteins in nonalcoholic fatty liver disease

PURPOSE OF REVIEW

The pathophysiologies of nonalcoholic fatty liver disease (NAFLD), metabolic syndrome, and cardiovascular disease are closely interlinked and associated with atherogenic dyslipidemia. Liver and cardiovascular disease may silently progress to advanced stages if alarming signs, such as abdominal obesity, elevated fasting and postprandial triglycerides, and low HDL cholesterol are overlooked. We review the metabolic mechanisms in NAFLD at the cellular level in the context of standard clinical lipid measurements.

RECENT FINDINGS

We discuss the pathogenesis of NAFLD, nonalcoholic steatohepatitis (NASH), and metabolic syndrome, atherogenic dyslipidemia, lipotoxicity, and lipophagy.

SUMMARY

Physicians should infer from biomarkers or clinical findings that their abdominally obese patients are at risk of severe cardiovascular, liver fatty disease, or both. Physicians should carry out laboratory tests of plasma cholesterol, triglycerides, LDL and HDL cholesterol, non-HDL cholesterol, apolipoprotein B and platelets, and for diabetes, but importantly, plasma triglycerides also in the nonfasting state. But note, clinical routine plasma lipid and lipoprotein measurements are not necessarily reliable for interpreting severe metabolic changes. Notably, in advanced stages of NAFLD (i.e., late steatohepatitis and cirrhosis), routine lipid profiles do not necessarily show any more abnormalities.

Autophagy determines efficiency of liver-directed gene therapy with adeno-associated viral vectors

Use of adeno-associated viral (AAV) vectors for liver-directed gene therapy has shown considerable success, particularly in patients with severe hemophilia B. However, the high vector doses required to reach therapeutic levels of transgene expression caused liver inflammation in some patients that selectively destroyed transduced hepatocytes. We hypothesized that such detrimental immune responses can be avoided by enhancing the efficacy of AAV vectors in hepatocytes. Because autophagy is a key liver response to environmental stresses, we characterized the impact of hepatic autophagy on AAV infection. We found that AAV induced mammalian target of rapamycin (mTOR)-dependent autophagy in human hepatocytes. This cell response was critically required for efficient transduction because under conditions of impaired autophagy (pharmacological inhibition, small interfering RNA knockdown of autophagic proteins, or suppression by food intake), recombinant AAV-mediated transgene expression was markedly reduced, both in vitro and in vivo. Taking advantage of this dependence, we employed pharmacological inducers of autophagy to increase the level of autophagy. This resulted in greatly improved transduction efficiency of AAV vectors in human and mouse hepatocytes independent of the transgene, driving promoter, or AAV serotype and was subsequently confirmed in vivo. Specifically, short-term treatment with a single dose of torin 1 significantly increased vector-mediated hepatic expression of erythropoietin in C57BL/6 mice. Similarly, coadministration of rapamycin with AAV vectors resulted in markedly enhanced expression of human acid-α-glucosidase in nonhuman primates.

CONCLUSION

We identified autophagy as a pivotal cell response determining the efficiency of AAVs intracellular processing in hepatocytes and thus the outcome of liver-directed gene therapy using AAV vectors and showed in a proof-of-principle study how this virus-host interaction can be employed to enhance efficacy of this vector system. (Hepatology 2017;66:252-265).

Lipid Droplets in Health and Disease

Lipids are essential building blocks synthesized by complex molecular pathways and deposited as lipid droplets (LDs) in cells. LDs are evolutionary conserved organelles found in almost all organisms, from bacteria to mammals. They are composed of a hydrophobic neutral lipid core surrounding by a phospholipid monolayer membrane with various decorating proteins. Degradation of LDs provide metabolic energy for divergent cellular processes such as membrane synthesis and molecular signaling. Lipolysis and autophagy are two main catabolic pathways of LDs, which regulate lipid metabolism and, thereby, closely engaged in many pathological conditons. In this review, we first provide an overview of the current knowledge on the structural properties and the biogenesis of LDs. We further focus on the recent findings of their catabolic mechanism by lipolysis and autophagy as well as their connection ragarding the regulation and function. Moreover, we discuss the relevance of LDs and their catabolism-dependent pathophysiological conditions.

Staurosporine suppresses survival of HepG2 cancer cells through Omi/HtrA2-mediated inhibition of PI3K/Akt signaling pathway

Staurosporine, which is an inhibitor of a broad spectrum of protein kinases, has shown cytotoxicity on several human cancer cells. However, the underlying mechanism is not well understood. In this study, we examined whether and how this compound has an inhibitory action on phosphatidylinositol 3-kinase (PI3K)/Akt pathway in vitro using HepG2 human hepatocellular carcinoma cell line. Cell viability and apoptosis were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and terminal deoxyribonucleotidyl transferase–mediated dUTP-digoxigenin nick end labeling (TUNEL) assay, respectively. Glutathione S-transferase (GST) pull-down assay and co-immunoprecipitation were performed to detect protein–protein interactions. Small interfering RNA (siRNA) was used to silence the expression of targeted protein. We found that staurosporine significantly decreased cell viability and increased cell apoptosis in a concentration- and time-dependent manner in HepG2 cancer cells, along with the decreased expressions of PDK1 protein and Akt phosphorylation. Staurosporine was also found to enhance Omi/HtrA2 release from mitochondria. Furthermore, Omi/HtrA2 directly bound to PDK1. Pharmacological and genetic inhibition of Omi/HtrA2 restored protein levels of PDK1 and protected HepG2 cancer cells from staurosporine-induced cell death. In addition, staurosporine was found to activate autophagy. However, inhibition of autophagy exacerbated cell death under concomitant treatment with staurosporine. Taken together, our results indicate that staurosporine induced cytotoxicity response by inhibiting PI3K/Akt signaling pathway through Omi/HtrA2-mediated PDK1 degradation, and the process provides a novel mechanism by which staurosporine produces its therapeutic effects.

Autophagy and hepatic lipid metabolism

Autophagy is initially thought to be a non-selective process in which intracellular proteins or damaged organelles are degraded. It is activated when cells lack nutrients and energy. Autophagy degrades cytoplasmic components within lysosomes and reuses the energy of amino acids to promote cell survival and maintain the cytoplasmic content. Current evidence implicates autophagy in the regulation of lipid stores within the two main organs involved in maintaining lipid homeostasis, the liver and adipose tissue. Upregulation of autophagy may lead to conversion of white adipose tissue into brown adipose tissue, thus regulating energy expenditure and obesity. Discovering new therapeutic interventions to treat lipid and lipoprotein disorders is of great interest and the discovery of autophagy as a regulator of lipid metabolism has opened up a new avenue for this area. In the liver, autophagy can play a role in some common metabolic disorders, which needs further research.

Downregulation of ASPP2 improves hepatocellular carcinoma cells survival via promoting BECN1-dependent autophagy initiation

Autophagy is an important catabolic process, which sustains intracellular homeostasis and lengthens cell survival under stress. Here we identify the ankyrin-repeat-containing, SH3-domain-containing, and proline-rich region-containing protein 2 (ASPP2), a haploinsufficient tumor suppressor, as a molecular regulator of starvation-induced autophagy in hepatocellular carcinoma (HCC). ASPP2 expression is associated with an autophagic response upon nutrient deprivation and downregulation of ASPP2 facilitates autophagic flux, whereas overexpression of ASPP2 blocks this starvation-induced autophagy in HCC cells. Mechanistically, ASPP2 inhibits autophagy through regulating BECN1 transcription and formation of phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3) complex. Firstly, ASPP2 inhibits p65/RelA-induced transcription of BECN1, directly by an ASPP2-p65/RelA-IκBα complex which inhibits phosphorylation of IκBα and the translocation of p65/RelA into the nucleus. Secondly, ASPP2 binds to BECN1, leading to decreased binding of PIK3C3 and UV radiation resistance-associated gene (UVRAG), and increased binding of Rubicon in PIK3C3 complex. Downregulation of ASPP2 enhances the pro-survival and chemoresistant property via autophagy in HCC cells in vitro and in vivo. Decreased ASPP2 expression was associated with increased BECN1 and poor survival in HCC patients. Therefore, ASPP2 is a key regulator of BECN1-dependent autophagy, and decreased ASPP2 may contribute to tumor progression and chemoresistance via promoting autophagy.

Nanoceria-Mediated Drug Delivery for Targeted Photodynamic Therapy on Drug-Resistant Breast Cancer

Photodynamic therapy (PDT) has shown great potential for overcoming drug-resistant cancers. Here, we report a multifunctional drug delivery system based on chlorin e6 (Ce6)/folic acid (FA)-loaded branched polyethylenimine-PEGylation ceria nanoparticles (PPCNPs-Ce6/FA), which was developed for targeted PDT to overcome drug-resistant breast cancers. Nanocarrier delivery and FA targeting significantly promoted the cellular uptake of photosensitizers (PSs), followed by their accumulation in lysosomes. PPCNPs-Ce6/FA generated reactive oxygen species (ROS) after near-infrared irradiation (NIR, 660 nm), leading to reduced P-glycoprotein (P-gp) expression, lysosomal membrane permeabilization (LMP), and excellent phototoxicity toward resistant MCF-7/ADR cells, even at ultralow doses. Moreover, we identified NIR-triggered lysosomal-PDT using the higher dose of PPCNPs-Ce6/FA, which stimulated cell death by plasma membrane blebbing, cell swelling, and energy depletion, indicating an oncosis-like cell death pathway, despite the occurrence of apoptotic or autophagic mechanisms at lower drug doses. In vivo studies showed prolonged blood circulation times, low toxicity in mice, and high tumor accumulation of PPCNPs-Ce6/FA. In addition, using NIR-triggered PDT, PPCNPs-Ce6/FA displayed excellent potency for tumor regression in the MCF-7/ADR xenograft murine model. This study suggested that multifunctional PPCNPs-Ce6/FA nanocomposites are a versatile and effective drug delivery system that may potentially be exploited for phototherapy to overcome drug-resistant cancers, and the mechanisms of cell death induced by PDT should be considered in the design of clinical protocols.

Hepatitis C Virus Infection Induces Autophagy as a Prosurvival Mechanism to Alleviate Hepatic ER-Stress Response

Hepatitis C virus (HCV) infection frequently leads to chronic liver disease, liver cirrhosis and hepatocellular carcinoma (HCC). The molecular mechanisms by which HCV infection leads to chronic liver disease and HCC are not well understood. The infection cycle of HCV is initiated by the attachment and entry of virus particles into a hepatocyte. Replication of the HCV genome inside hepatocytes leads to accumulation of large amounts of viral proteins and RNA replication intermediates in the endoplasmic reticulum (ER), resulting in production of thousands of new virus particles. HCV-infected hepatocytes mount a substantial stress response. How the infected hepatocyte integrates the viral-induced stress response with chronic infection is unknown. The unfolded protein response (UPR), an ER-associated cellular transcriptional response, is activated in HCV infected hepatocytes. Over the past several years, research performed by a number of laboratories, including ours, has shown that HCV induced UPR robustly activates autophagy to sustain viral replication in the infected hepatocyte. Induction of the cellular autophagy response is required to improve survival of infected cells by inhibition of cellular apoptosis. The autophagy response also inhibits the cellular innate antiviral program that usually inhibits HCV replication. In this review, we discuss the physiological implications of the HCV-induced chronic ER-stress response in the liver disease progression.