Eun Jin Sun

Bio: Eun Jin Sun is an academic researcher from James Cook University. The author has contributed to research in topics: Autophagy & Protein kinase B. The author has co-authored 1 publications.

Targeting the PI3K/Akt/mTOR Pathway in Hepatocellular Carcinoma.

Abstract: Despite advances in the treatment of cancers through surgical procedures and new pharmaceuticals, the treatment of hepatocellular carcinoma (HCC) remains challenging as reflected by low survival rates. The PI3K/Akt/mTOR pathway is an important signaling mechanism that regulates the cell cycle, proliferation, apoptosis, and metabolism. Importantly, deregulation of the PI3K/Akt/mTOR pathway leading to activation is common in HCC and is hence the subject of intense investigation and the focus of current therapeutics. In this review article, we consider the role of this pathway in the pathogenesis of HCC, focusing on its downstream effectors such as glycogen synthase kinase-3 (GSK-3), cAMP-response element-binding protein (CREB), forkhead box O protein (FOXO), murine double minute 2 (MDM2), p53, and nuclear factor-κB (NF-κB), and the cellular processes of lipogenesis and autophagy. In addition, we provide an update on the current ongoing clinical development of agents targeting this pathway for HCC treatments.

The Emerging Role of Branched-Chain Amino Acids in Liver Diseases

Abstract: Chronic liver diseases pose a substantial health burden worldwide, with approximately two million deaths each year. Branched-chain amino acids (BCAAs)—valine, leucine, and isoleucine—are a group of essential amino acids that are essential for human health. Despite the necessity of a dietary intake of BCAA, emerging data indicate the undeniable correlation between elevated circulating BCAA levels and chronic liver diseases, including non-alcoholic fatty liver diseases (NAFLD), cirrhosis, and hepatocellular carcinoma (HCC). Moreover, circulatory BCAAs were positively associated with a higher cholesterol level, liver fat content, and insulin resistance (IR). However, BCAA supplementation was found to provide positive outcomes in cirrhosis and HCC patients. This review will attempt to address the contradictory claims found in the literature, with a special focus on BCAAs’ distribution, key signaling pathways, and the modulation of gut microbiota. This should provide a better understanding of BCAAs’ possible contribution to liver health.

Combined Targeting of AKT and mTOR Inhibits Tumor Formation of EpCAM+ and CD90+ Human Hepatocellular Carcinoma Cells in an Orthotopic Mouse Model

Abstract: Simple Summary Cancer stem cells are a distinct tumor subpopulation associated with poor outcome. The epithelial cell adhesion molecule (EpCAM) and Thy-1 cell surface antigen (CD90) have been implicated as cancer stem cell (CSC) markers in hepatocellular carcinoma (HCC). Eradication of those CSCs is of high importance with respect to the outcome of treatment. We aimed to verify the impact of targeting HCC cells expressing the CSC marker CD90 and EpCAM with combined therapy of AKT and mTOR inhibitors. Our data demonstrated that combined targeting of AKT and mTOR is highly synergistic in vitro but leads to treatment resistance of xenograft tumors in an orthotopic mouse model in vivo. The development of resistance was observed in large numbers of MK2206/RAD001 treated cells. Restoration of phosphorylated AKT was observed in most tumors during AKT/mTOR therapy underlining the importance of restored AKT signaling as a resistance mechanism. Further work is required to verify the molecular mechanisms of HCC treatment resistance. Abstract The epithelial cell adhesion molecule (EpCAM) and Thy-1 cell surface antigen (CD90) have been implicated as cancer stem cell (CSC) markers in hepatocellular carcinoma (HCC). Expression of EpCAM and CD90 on HCC cells is associated with increased tumorigenicity, metastasis and poor prognosis. In this study, we demonstrate that combined treatment with AKT and mTOR inhibitors—i.e., MK2206 and RAD001—results in a synergistic reduction in proliferation of EpCAM+ and CD90+ HCC cells cultured either as adherent cells or as tumoroids in vitro. In addition, tumor growth was reduced by combined treatment with AKT and mTOR inhibitors in an orthotopic xenograft mouse model of an EpCAM+ HCC cell line (Huh7) and primary patient-derived EpCAM+ HCC cells (HCC1) as well as a CD90+ HCC-related cell line (SK-HEP1) in vivo. However, during AKT/mTOR treatment, outgrowth of therapy-resistant tumors was observed in all mice analyzed within a few weeks. Resistance was associated in most cases with restoration of AKT signaling in the tumors, intrahepatic metastases and distant metastases. In addition, an upregulation of the p38 MAPK pathway was identified in the AKT/mTOR inhibitor-resistant tumor cells by kinome profiling. The development of resistant cells during AKT/mTOR therapy was further analyzed by red-green-blue (RGB) marking of HCC cells, which revealed an outgrowth of a large number of Huh7 cells over a period of 6 months. In summary, our data demonstrate that combined treatment with AKT and mTOR inhibitors exhibits synergistic effects on proliferation of EpCAM+ as well as CD90+ HCC cells in vitro. However, the fast development of large numbers of resistant clones under AKT/mTOR therapy observed in vitro and in the orthotopic xenotransplantation mouse model in vivo strongly suggests that this therapy alone will not be sufficient to eliminate EpCAM+ or CD90+ cancer stem cells from HCC patients.

The Translational Bridge between Inflammation and Hepatocarcinogenesis

Abstract: Viral infections or persistent alcohol or drug abuse, together with intrinsic factors, lead to hepatitis, which often ends in the development of liver cirrhosis or hepatocellular carcinoma (HCC). With this review, we describe inflammatory liver diseases, such as acute liver failure, virus-induced hepatitis, alcoholic- and non-alcoholic steatohepatitis, and autoimmune hepatitis, and highlight their driving mechanisms. These include external factors such as alcohol misuse, viral infection and supernutrition, as well as intrinsic parameters such as genetic disposition and failure, in immune tolerance. Additionally, we describe what is known about the translational machinery within all these diseases. Distinct eukaryotic translation initiation factors (eIFs) with specific functional roles and aberrant expression in HCC are reported. Many alterations to the translational machinery are already triggered in the precancerous lesions described in this review, highlighting mTOR pathway proteins and eIFs to emphasize their putative clinical relevance. Here, we identified a lack of knowledge regarding the roles of single eIF proteins. A closer investigation will help to understand and treat HCC as well as the antecedent diseases.

Exosomes From Cancer-Associated Mesenchymal Stem Cells Transmit TMBIM6 to Promote the Malignant Behavior of Hepatocellular Carcinoma via Activating PI3K/AKT Pathway

Abstract: Objective Cancer-associated mesenchymal stem cells (MSCs) regulate the progression of cancers through exosome-delivered components, while few studies are conducted on hepatocellular carcinoma (HCC). This study aimed to evaluate the effect of exosomes from HCC-associated MSCs (HCC-MSCs) on HCC cellular functions and the potential regulatory mechanism. Methods HCC cells (Huh7 and PLC) were cultured normally or co-cultured with HCC-MSCs, HCC-MSCs plus GW4869, or HCC-MSC-derived exosomes; then mRNA sequencing and RT-qPCR validation were conducted. Subsequently, candidate genes were sorted out and modified in HCC cells. Next, TMBIM6-modified HCC-MSCs were used to treat HCC cells. Results Both HCC-MSCs and their derived exosomes promoted proliferation, invasion, sphere formation ability but suppressed apoptosis in HCC cells (all p < 0.05); however, the effect of HCC-MSCs on these cellular functions was repressed by exosome inhibitor (GW4869). Subsequently, TMBIM6, EEF2, and PRDX1 were sorted out by mRNA sequencing and RT-qPCR validation as candidate genes implicated in the regulation of HCC cellular functions by HCC-MSC-derived exosomes. Among them, TMBIM6 had a potent effect (all p < 0.05), while EEF2 and PRDX1 had less effect on regulating HCC cell viability and invasion. Next, direct silencing TMBIM6 repressed viability, sphere formation, invasion, epithelial–mesenchymal transition (EMT), and PI3K/AKT pathway but promoted apoptosis in HCC cells; however, overexpressing TMBIM6 showed the opposite effect. Furthermore, incubating with exosomes from TMBIM6-modified HCC-MSCs presented a similar effect as direct TMBIM6 modification in HCC cells. Conclusion HCC-MSC-derived exosomes transmit TMBIM6 to promote malignant behavior via PI3K/AKT pathway in HCC.