Core fucosylated glycan-dependent inhibitory effect of QSOX1-S on invasion and metastasis of hepatocellular carcinoma

Glycoproteomic contributions to hepatocellular carcinoma research: a 2023 update

INTRODUCTION

Hepatocellular carcinoma (HCC) represents a significant burden globally, which ranks sixth among the most frequently diagnosed cancers and stands as the third leading cause of cancer-related mortality. Glycoproteomics, as an important branch of proteomics, has already made significant achievements in the field of HCC research. Aberrant protein glycosylation has shown to promote the malignant transformation of hepatocytes by modulating a wide range of tumor-promoting signaling pathways. The glycoproteome provides valuable information for understanding cancer progression, tumor immunity, and clinical outcome, which could serve as potential diagnostic, prognostic, and therapeutic tools in HCC.

AREAS COVERED

In this review, recent advances of glycoproteomics contribute to clinical applications (diagnosis and prognosis) and molecular mechanisms (hepatocarcinogenesis, progression, stemness and recurrence, and drug resistance) of HCC are summarized.

EXPERT OPINION

Glycoproteomics shows promise in HCC, enhancing early detection, risk stratification, and personalized treatments. Challenges include sample heterogeneity, diverse glycans structures, sensitivity issues, complex workflows, limited databases, and incomplete understanding of immune cell glycosylation. Addressing these limitations requires collaborative efforts, technological advancements, standardization, and validation studies. Future research should focus on targeting abnormal protein glycosylation therapeutically. Advancements in glycobiomarkers and glycosylation-targeted therapies will greatly impact HCC diagnosis, prognosis, and treatment.

Advancements in Oncoproteomics Technologies: Treading toward Translation into Clinical Practice

Proteomics continues to forge significant strides in the discovery of essential biological processes, uncovering valuable information on the identity, global protein abundance, protein modifications, proteoform levels, and signal transduction pathways. Cancer is a complicated and heterogeneous disease, and the onset and progression involve multiple dysregulated proteoforms and their downstream signaling pathways. These are modulated by various factors such as molecular, genetic, tissue, cellular, ethnic/racial, socioeconomic status, environmental, and demographic differences that vary with time. The knowledge of cancer has improved the treatment and clinical management; however, the survival rates have not increased significantly, and cancer remains a major cause of mortality. Oncoproteomics studies help to develop and validate proteomics technologies for routine application in clinical laboratories for (1) diagnostic and prognostic categorization of cancer, (2) real-time monitoring of treatment, (3) assessing drug efficacy and toxicity, (4) therapeutic modulations based on the changes with prognosis and drug resistance, and (5) personalized medication. Investigation of tumor-specific proteomic profiles in conjunction with healthy controls provides crucial information in mechanistic studies on tumorigenesis, metastasis, and drug resistance. This review provides an overview of proteomics technologies that assist the discovery of novel drug targets, biomarkers for early detection, surveillance, prognosis, drug monitoring, and tailoring therapy to the cancer patient. The information gained from such technologies has drastically improved cancer research. We further provide exemplars from recent oncoproteomics applications in the discovery of biomarkers in various cancers, drug discovery, and clinical treatment. Overall, the future of oncoproteomics holds enormous potential for translating technologies from the bench to the bedside.

Perspectives and mechanisms for targeting ferroptosis in the treatment of hepatocellular carcinoma

Ferroptosis is a novel process of regulated cell death discovered in recent years, mainly caused by intracellular lipid peroxidation. It is morphologically manifested as shrinking of mitochondria, swelling of cytoplasm and organelles, rupture of plasma membrane, and formation of double-membrane vesicles. Work done in the past 5 years indicates that induction of ferroptosis is a promising strategy in the treatment of hepatocellular carcinoma (HCC). System xc^-/GSH/GPX4, iron metabolism, p53 and lipid peroxidation pathways are the main focus areas in ferroptosis research. In this paper, we analyze the ferroptosis-inducing drugs and experimental agents that have been used in the last 5 years in the treatment of HCC. We summarize four different key molecular mechanisms that induce ferroptosis, i.e., system xc^-/GSH/GPX4, iron metabolism, p53 and lipid peroxidation. Finally, we outline the prognostic analysis associated with ferroptosis in HCC. The findings summarized suggest that ferroptosis induction can serve as a promising new therapeutic approach for HCC and can provide a basis for clinical diagnosis and prevention of this disease.

Finding New Ways How to Control BACE1

Recently, all applications of BACE1 inhibitors failed as therapeutical targets for Alzheimer´s disease (AD) due to severe side effects. Therefore, alternative ways for treatment development are a hot research topic. The present analysis investigates BACE1 protein-protein interaction networks and attempts to solve the absence of complete knowledge about pathways involving BACE1. A bioinformatics analysis matched the functions of the non-substrate interaction network with Voltage-gated potassium channels, which also appear as top priority protein nodes. Targeting BACE1 interactions with PS1 and GGA-s, blocking of BACE1 access to APP by BRI3 and RTN-s, activation of Wnt signaling and upregulation of β-catenin, and brain delivery of the extracellular domain of p75^NTR, are the main alternatives to the use of BACE 1 inhibitors highlighted by the analysis. The pathway enrichment analysis also emphasized substrates and substrate candidates with essential biological functions, which cleavage must remain controlled. They include ephrin receptors, ROBO1, ROBO2, CNTN-s, CASPR-s, CD147, CypB, TTR, APLP1/APLP2, NRXN-s, and PTPR-s. The analysis of the interaction subnetwork of BACE1 functionally related to inflammation identified a connection to three cardiomyopathies, which supports the hypothesis of the common molecular mechanisms with AD. A lot of potential shows the regulation of BACE1 activity through post-translational modifications. The interaction network of BACE1 and its phosphorylation enzyme CSNK1D functionally match the Circadian clock, p53, and Hedgehog signaling pathways. The regulation of BACE1 glycosylation could be achieved through N-acetylglucosamine transferases, α-(1→6)-fucosyltransferase, β-galactoside α-(2→6)-sialyltransferases, galactosyltransferases, and mannosidases suggested by the interaction network analysis of BACE1-MGAT3. The present analysis proposes possibilities for the alternative control of AD pathology.

Ferroptosis in Cancer Immunotherapy—Implications for Hepatocellular Carcinoma

Ferroptosis is a recently recognized iron-dependent form of non-apoptotic regulated cell death (RCD) characterized by lipid peroxide accumulation to lethal levels. Cancer cells, which show an increased iron dependency to enable rapid growth, seem vulnerable to ferroptosis. There is also increasing evidence that ferroptosis might be immunogenic and therefore could synergize with immunotherapies. Hepatocellular carcinoma (HCC) is the most common primary liver tumor with a low survival rate due to frequent recurrence and limited efficacy of conventional chemotherapies, illustrating the urgent need for novel drug approaches or combinatorial strategies. Immunotherapy is a new treatment approach for advanced HCC patients. In this setting, ferroptosis inducers may have substantial clinical potential. However, there are still many questions to answer before the mystery of ferroptosis is fully unveiled. This review discusses the existing studies and our current understanding regarding the molecular mechanisms of ferroptosis with the goal of enhancing response to immunotherapy of liver cancer. In addition, challenges and opportunities in clinical applications of potential candidates for ferroptosis-driven therapeutic strategies will be summarized. Unraveling the role of ferroptosis in the immune response could benefit the development of promising anti-cancer therapies that overcome drug resistance and prevent tumor metastasis.

Molecular Targets of Ferroptosis in Hepatocellular Carcinoma

Ferroptosis is a special form of regulatory cell death caused by the accumulation of intracellular iron and lipid peroxidation. Here, we summarize the research progress on ferroptosis in hepatocellular carcinoma (HCC), trace the development of the concept of ferroptosis and its key regulatory factors, and discuss the application value of ferroptosis in the treatment of HCC from different perspectives. We believe that exploring the relationship between ferroptosis and HCC and clarifying the metabolism and expression of ferroptosis-specific genes and molecules will accelerate the development of novel ferroptosis-related molecules as HCC markers and therapeutic targets. We hope to provide a theoretical basis for better diagnosis and treatment to effectively improve the prognosis of patients with HCC.

QSOX2 Is an E2F1 Target Gene and a Novel Serum Biomarker for Monitoring Tumor Growth and Predicting Survival in Advanced NSCLC

Background

Quiescin Q6 sulfhydryl oxidase 2 (QSOX2), an enzyme that can be directly secreted into the extracellular space, is known to be associated with oxidative protein folding. However, whether QSOX2 is abnormally expressed in non-small cell lung cancer (NSCLC) and its role in tumor growth remains unclear.

Methods

Real-time quantitative PCR (qPCR), immunohistochemistry (IHC), bioinformatics analyses were applied to analyze the expression pattern and prognostic significance of QSOX2 in NSCLC. Xenografts model, enzyme-linked immunosorbent assays (ELISA), western blot analysis (WB), and IHC were preformed to examine in vivo tumor suppression and intracellular and extracellular expression of QSOX2. Flow cytometry, WB and qPCR analyses were used to elucidate the role of QSOX2 in cell cycle regulation. Chromatin immunoprecipitation assay (ChIP) assay and Dual-Luciferase reporter assay were employed to investigate transcriptional regulation of QSOX2 by E2F Transcription Factor 1 (E2F1).

Results

Quiescin sulfhydryl oxidase 2 was significantly overexpressed in NSCLC and associated with poor survival in advanced-stage patients. The intracellular and extracellular expression of QSOX2 by tumor cells markedly decreased after anti-cancer therapy in vitro, in vivo and in the clinic. Moreover, QSOX2 silencing in NSCLC cell lines resulted in inhibition of cancer cell proliferation, induction of apoptosis, and decreased expression of cell division-related genes (CENPF and NUSAP1) and Wnt pathway activators (PRRX2 and Nuc-β-catenin). Mechanistically, QSOX2 was expressed periodically during cell cycle and directly regulated by E2F1.

Conclusions

Our findings demonstrate that QSOX2 is directly regulated by E2F1 in the cell cycle, which is essential for the proliferation of NSCLC cells. Furthermore, QSOX2 is a prognostic indicator for NSCLC and may be developed into a biomarker for monitoring tumor burden and therapeutic progress.

Fucosyltransferase 8 regulation and breast cancer suppression by transcription factor activator protein 2γ

Alterations of glycosyltransferase expression are often associated with tumor occurrence and progression. Among the many glycosyltransferases, increased expression of fucosyltransferase 8 (FUT8) has been frequently observed to be involved in progression and metastasis of various types of cancer. The regulatory mechanisms of FUT8 expression remain unclear. FUT8 expression was shown, in this study, to be elevated in breast cancer. Systematic analysis revealed that transcription factor activator protein 2γ (AP-2γ) is the target gene of microRNA-10b (miR-10b), which we previously identified as a positive regulator of FUT8. Overexpression of AP-2γ inhibited FUT8 expression, with associated reduction of cell invasiveness and migration ability. AP-2γ was capable of binding to transcription factor STAT3, and phosphorylation of STAT3 induced transcription of the FUT8 gene. On the basis of our findings, we propose that binding of AP-2γ to STAT3 results in formation of the AP-2γ/STAT3 complex and consequent inhibition of STAT3 phosphorylation, thereby preventing entry of p-STAT3 into the nucleus to initiate FUT8 transcription. This study clarifies the molecular mechanisms whereby transcription factor AP-2γ regulates FUT8 expression in breast cancer.

Quiescin sulfhydryl oxidase 1 promotes sorafenib-induced ferroptosis in hepatocellular carcinoma by driving EGFR endosomal trafficking and inhibiting NRF2 activation

Sorafenib is a first-line molecular-target drug for advanced hepatocellular carcinoma (HCC), but its clinical effects are still limited. In this study we identify Quiescin sulfhydryl oxidase 1 (QSOX1) acting as a cellular pro-oxidant, specifically in the context of sorafenib treatment of HCC. QSOX1 disrupts redox homoeostasis and sensitizes HCC cells to oxidative stress by inhibiting activation of the master antioxidant transcription factor NRF2. A negative correlation between QSOX1 and NRF2 expression was validated in tumor tissues from 151 HCC patients. Mechanistically, QSOX1 restrains EGF-induced EGFR activation by promoting ubiquitination-mediated degradation of EGFR and accelerating its intracellular endosomal trafficking, leading to suppression of NRF2 activity. Additionally, QSOX1 potentiates sorafenib-induced ferroptosis by suppressing NRF2 in vitro and in vivo. In conclusion, the data presented identify QSOX1 as a novel candidate target for sorafenib-based combination therapeutic strategies in HCC or other EGFR-dependent tumor types.

Recent Advances of Functional Proteomics in Gastrointestinal Cancers- a Path towards the Identification of Candidate Diagnostic, Prognostic, and Therapeutic Molecular Biomarkers

Gastrointestinal (GI) cancer remains one of the common causes of morbidity and mortality. A high number of cases are diagnosed at an advanced stage, leading to a poor survival rate. This is primarily attributed to the lack of reliable diagnostic biomarkers and limited treatment options. Therefore, more sensitive, specific biomarkers and curative treatments are desirable. Functional proteomics as a research area in the proteomic field aims to elucidate the biological function of unknown proteins and unravel the cellular mechanisms at the molecular level. Phosphoproteomic and glycoproteomic studies have emerged as two efficient functional proteomics approaches used to identify diagnostic biomarkers, therapeutic targets, the molecular basis of disease and mechanisms underlying drug resistance in GI cancers. In this review, we present an overview on how functional proteomics may contribute to the understanding of GI cancers, namely colorectal, gastric, hepatocellular carcinoma and pancreatic cancers. Moreover, we have summarized recent methodological developments in phosphoproteomics and glycoproteomics for GI cancer studies.

QSOX1 promotes mitochondrial apoptosis of hepatocellular carcinoma cells during anchorage-independent growth by inhibiting lipid synthesis

Anoikis is a programmed death of cell induced upon detachment from the extracellular matrix (ECM). Resistance to anoikis is a critical contributor to cancer invasion and metastasis. High frequency of metastatic recurrence is a huge challenge for current therapy of hepatocellular carcinoma (HCC). Our previous study had identified sulfhydryl oxidase 1 (QSOX1) as a suppressor of HCC metastasis. In the present study, we used the anchorage-independent growth condition to mimic the detachment of HCC cells from ECM. We found that QSOX1 was induced in HCC cells under the anchorage-independent growth condition and that could be blocked by endoplasmic reticulum stress (ERS) inhibitor. Overexpression and knockdown of QSOX1 gene were performed on HCC cells. QSOX1 inhibited de novo synthesis of fatty acids (FAs) and cholesterol (ChE) and reduced their content in the detached HCC cells, and thus mediated mitochondrial apoptosis of HCC cells. In conclusion, QSOX1 is induced under detached culture condition via ERS. QSOX1 promotes mitochondrial apoptosis by suppressing the lipid synthesis of HCC cells in detached condition. QSOX1 appears to accelerate anoikis of HCC cells. These findings offer a new insight into how to overcome anoikis resistance of HCC cells and provide a potential target for prevention of HCC metastasis.

Quiescin Sulfhydryl Oxidase 1 Regulates the Proliferation, Migration and Invasion of Human Glioblastoma Cells via PI3K/Akt Pathway

Background

Quiescin sulfhydryl oxidase 1 (QSOX1) involves in the formation of disulfide bonds and participates in the protein folding process. In recent years, accumulating evidences have shown that QSOX1 is a biomarker for tumor development and prognosis. However, the biological function of QSOX1 in glioblastoma (GBM) remains unclear.

Materials and Methods

QSOX1 expression in glioma and overall survival of glioma patients were analyzed through The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) databases. shRNAs were used to decrease the expression of QSOX1 in U87 and U251 cells. Celltiter-Glo and colony formation assays were used to assess cell proliferation. Transwell and scratch assays were utilized to determine cell migration and invasion, the xenograft mouse models were established to evaluate the effect of QSOX1 knockdown in vivo. Western blot assays were used to detect the changes of E-cadherin/N-cadherin/vimentin and PI3K/Akt pathway.

Results

We found that QSOX1 was upregulated in glioma, especially in GBM. Upregulation of QSOX1 was correlated with poor prognosis in glioma patients. We discovered for the first time that suppression of QSOX1 expression inhibited proliferation, migration and invasion, as well as epithelial-mesenchymal transition (EMT) in GBM cell lines. In addition, phosphorylated PI3K and Akt were downregulated in the QSOX1-knockdown groups. Moreover, QSOX1 knockdown-impaired cell growth was partially rescued by Akt activator.

Conclusion

Our findings revealed that QSOX1 was a novel biomarker for GBM patients and QSOX1 promoted cell proliferation, migration and invasion through regulating PI3K/Akt pathway in GBM.