Aspartate β-hydroxylase disrupts mitochondrial DNA stability and function in hepatocellular carcinoma

Mitochondrial DNA copy number in Hepatitis C virus-related chronic liver disease: impact of direct-acting antiviral therapy

Hepatitis C virus (HCV) infection can regulate the number and dynamics of mitochondria, and is associated with a prominent hepatic mitochondrial injury. Mitochondrial distress conveys oxidative damage which is implicated in liver disease progression. The present study was conducted to assess the change of mitochondrial DNA (mtDNA) copy number in patients with HCV-related chronic liver disease and the impact of direct-acting antiviral (DAA) therapy. Whole blood mtDNA copy number was measured using real-time quantitative polymerase chain reaction at baseline and 12 weeks after the end of therapy in 50 treatment-naïve HCV-infected patients who achieved sustained viral response (SVR) after DAA therapy and 20 healthy controls. Whole blood mtDNA copy number appeared significantly lower in HCV-infected patients before therapy compared to healthy subjects (P < 0.001). Post-treatment, there was significant increase of mtDNA copy number in HCV-infected patients at SVR12 compared to the pre-treatment values (P < 0.001), meanwhile it didn't differ significantly between HCV-infected patients after therapy and healthy subjects (P = 0.059). Whole blood mtDNA copy number correlated inversely to the serum bilirubin in HCV-infected patients (P = 0.013), however it didn't correlate significantly to the serum aminotransferases, viral load or fibrosis-4 score (P > 0.05). In conclusion, chronic HCV infection has been associated with a prominent mitochondrial injury which could mediate a progressive liver disease. The improved mtDNA content after DAA therapy highlights a possible potential of these drugs to alleviate mitochondrial damage in HCV-related liver disease.

Labyrinthin: A distinct pan-adenocarcinoma diagnostic and immunotherapeutic tumor specific antigen

Structural analysis and detection of optimal cell surface localization of labyrinthin, a pan-adenocarcinoma target, was studied with respect to adenocarcinoma specificity vs. normal and non-adenocarcinoma cells. Patient-derived tissue microarray immunohistochemistry (IHC) was performed on 729 commercially prepared tissue blocks of lung, colon, breast, pancreas, prostate, and ovary cancers combined, plus a National Cancer Institute (NCI) tissue microarray derived from another 236 cases. The results confirmed that anti-labyrinthin mouse monoclonal MCA 44-3A6 antibody recognized adenocarcinomas, but not normal or non-adenocarcinoma cancer cells. The consensus of multiple topology analysis programs on labyrinthin (255 amino acids) estimate a type II cell membrane associated protein with an N-terminus signal peptide. However, because the labyrinthin sequence is enveloped within the 758 amino acids of the intracellular aspartyl/asparaginyl beta-hydroxylase (ASPH), a purported tumor associated antigen, standard IHC methods that permeabilize cells can expose common epitopes. To circumvent antibody cross-reactivity, cell surface labyrinthin was distinguished from intracellular ASPH by FACS analysis of permeabilized vs non-permeabilized cells. All permeabilized normal, adeno-and non-adenocarcinoma cells produced a strong MCA 44-3A6 binding signal, likely reflecting co-recognition of intracellular ASPH proteins along with internalized labyrinthin, but in non-permeabilized cells only adenocarcinoma cells were positive for labyrinthin. Confocal microscopy confirmed the FACS results. Labyrinthin as a functional cell-surface marker was suggested when: 1) WI-38 normal lung fibroblasts transfected with labyrinthin sense cDNA displayed a cancerous phenotype; 2) antisense transfection of A549 human lung adenocarcinoma cells appeared more normal; and 3) MCA44-3A6 suppressed A549 cell proliferation. Collectively, the data indicate that labyrinthin is a unique, promising adenocarcinoma tumor-specific antigen and therapeutic target. The study also raises a controversial issue on the extent, specificity, and usefulness of ASPH as an adenocarcinoma tumor-associated antigen.

Aspartate β-hydroxylase targeting in castration-resistant prostate cancer modulates the NOTCH/HIF1α/GSK3β crosstalk

Castration-resistant prostate cancer (CRPC) is an incurable stage of the disease. A multivariate principal component analysis on CRPC in vitro models identified aspartyl (asparaginyl) β hydrolase (ASPH) as the most relevant molecule associated with the CRPC phenotype. ASPH is overexpressed in various malignant neoplasms and catalyzes the hydroxylation of aspartyl and asparaginyl residues in the epidermal growth factor (EGF)-like domains of proteins like NOTCH receptors and ligands, enhancing cell motility, invasion and metastatic spread. Bioinformatics analyses of ASPH in prostate cancer (PCa) and CRPC datasets indicate that ASPH gene alterations have prognostic value both in PCa and CRPC patients. In CRPC cells, inhibition of ASPH expression obtained through specific small interfering RNA or culturing cells in hypoxic conditions, reduced cell proliferation, invasion and cyclin D1 expression through modulation of the NOTCH signaling. ASPH and HIF1α crosstalk, within a hydroxylation-regulated signaling pathway, might be transiently driven by the oxidative stress evidenced inside CRPC cells. In addition, increased phosphorylation of GSK3β by ASPH silencing demonstrates that ASPH regulates GSK3β activity inhibiting its interactions with upstream kinases. These findings demonstrate the critical involvement of ASPH in CRPC development and may represent an attractive molecular target for therapy.

Diverse molecular functions of aspartate β‑hydroxylase in cancer (Review)

Aspartate/asparagine β-hydroxylase (AspH) is a type II transmembrane protein that catalyzes the post-translational hydroxylation of definite aspartyl and asparaginyl residues in epidermal growth factor-like domains of substrates. In the last few decades, accumulating evidence has indicated that AspH expression is upregulated in numerous types of human malignant cancer and is associated with poor survival and prognosis. The AspH protein aggregates on the surface of tumor cells, which contributes to inducing tumor cell migration, infiltration and metastasis. However, small-molecule inhibitors targeting hydroxylase activity can markedly block these processes, both in vitro and in vivo. Immunization of tumor-bearing mice with a phage vaccine fused with the AspH protein can substantially delay tumor growth and progression. Additionally, AspH antigen-specific CD4⁺ and CD8⁺ T cells were identified in the spleen of tumor-bearing mice. Therefore, these agents may be used as novel strategies for cancer treatment. The present review summarizes the current progress on the underlying mechanisms of AspH expression in cancer development.

Aspartate β-hydroxylase as a target for cancer therapy

As metastasis is a major cause of death in cancer patients, new anti-metastatic strategies are needed to improve cancer therapy outcomes. Numerous pathways have been shown to contribute to migration and invasion of malignant tumors. Aspartate β-hydroxylase (ASPH) is a key player in the malignant transformation of solid tumors by enhancing cell proliferation, migration, and invasion. ASPH also promotes tumor growth by stimulation of angiogenesis and immunosuppression. These effects are mainly achieved via the activation of Notch and SRC signaling pathways. ASPH expression is upregulated by growth factors and hypoxia in different human tumors and its inactivation may have broad clinical impact. Therefore, small molecule inhibitors of ASPH enzymatic activity have been developed and their anti-metastatic effect confirmed in preclinical mouse models. ASPH can also be targeted by monoclonal antibodies and has also been used as a tumor-associated antigen to induce both cluster of differentiation (CD) 8+ and CD4+ T cells in mice. The PAN-301-1 vaccine against ASPH has already been tested in a phase 1 clinical trial in patients with prostate cancer. In summary, ASPH is a promising target for anti-tumor and anti-metastatic therapy based on inactivation of catalytic activity and/or immunotherapy.

Mitochondrial DNA in liver inflammation and oxidative stress

The function of liver is highly dependent on mitochondria producing ATP for biosynthetic and detoxifying properties. Accumulating evidence indicates that most hepatic disorders are characterized by profound mitochondrial dysfunction. Mitochondrial dysfunction not only exhibits mitochondrial DNA (mtDNA) damage and depletion, but also releases mtDNA. mtDNA is a closed circular molecule encoding 13 of the polypeptides of the oxidative phosphorylation system. Extensive mtDNA lesions could exacerbate mitochondrial oxidative stress and subsequently cause damage to hepatocytes. When mtDNA leaves the confines of mitochondria to the cytosolic and extracellular environment, it can act as damage-associated molecular patterns (DAMPs) to trigger the inflammatory response through the Toll-like receptor 9, inflammasomes, and stimulator of interferon genes (STING) pathways and further exacerbate hepatocellular damage and even remote organs injury. In addition, mtDNA also plays a vital role in hepatitis B virus (HBV)-related liver injury and hepatocellular carcinoma (HCC). In this review, we describe mtDNA alterations during liver injury, focusing on the mechanisms of mtDNA-mediated liver inflammation and oxidative stress injury.

Mito-Nuclear Communication in Hepatocellular Carcinoma Metabolic Rewiring

As the main metabolic and detoxification organ, the liver constantly adapts its activity to fulfill the energy requirements of the whole body. Despite the remarkable adaptive capacity of the liver, prolonged exposure to noxious stimuli such as alcohol, viruses and metabolic disorders results in the development of chronic liver disease that can progress to hepatocellular carcinoma (HCC), which is currently the second leading cause of cancer-related death worldwide. Metabolic rewiring is a common feature of cancers, including HCC. Altered mito-nuclear communication is emerging as a driving force in the metabolic reprogramming of cancer cells, affecting all aspects of cancer biology from neoplastic transformation to acquired drug resistance. Here, we explore relevant aspects (and discuss recent findings) of mito-nuclear crosstalk in the metabolic reprogramming of hepatocellular carcinoma.

Recent advances in research on aspartate β-hydroxylase (ASPH) in pancreatic cancer: A brief update

Pancreatic cancer (PC) is a highly aggressive tumor, often difficult to diagnose and treat. Aspartate β-hydroxylase (ASPH) is a type II transmembrane protein and the member of α-ketoglutarate-dependent dioxygenase family, found to be overexpressed in different cancer types, including PC. ASPH appears to be involved in the regulation of proliferation, invasion and metastasis of PC cells through multiple signaling pathways, suggesting its role as a tumor biomarker and therapeutic target. In this review, we briefly summarize the possible mechanisms of action of ASPH in PC and recent progress in the therapeutic approaches targeting ASPH.

Hydroxylase Activity of ASPH Promotes Hepatocellular Carcinoma Metastasis Through Epithelial-to-Mesenchymal Transition Pathway

Over-expression of aspartyl (asparagynal)-β-hydroxylase (ASPH) contributes to hepatocellular carcinoma (HCC) invasiveness, but the role of ASPH hydroxylase activity in this process remains to be defined. As such, the current study investigated the role of ASPH hydroxylase activity in downstream signalling of HCC tumorgenesis and, specifically, metastasis development. Over-expression of wild-type ASPH, but not a hydroxylase mutant, promoted HCC cell migration in vitro, as well as intrahepatic and distant metastases in vivo. The enhanced migration and epithelial to mesenchymal transition (EMT) activation was notably absent in response to hydroxylase activity blockade. Vimentin, a regulator of EMT, interacted with ASPH and likely mediated the effect of ASPH hydroxylase activity with cell migration. The enhanced hydroxylase activity in tumor tissues predicted worse prognoses of HCC patients. Collectively, the hydroxylase activity of ASPH affected HCC metastasis through interacting with vimentin and regulating EMT. As such, ASPH might be a promising therapeutic target of HCC.

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Over-expression of ASPH promoted HCC intrahepatic and distant metastases in vivo.

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ASPH interacts with vimentin to promote HCC cell migration.

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Enhanced hydroxylase activity in tumor predicted worse prognoses of HCC patients.

Hepatocellular carcinoma has aggressive invasiveness and high metastatic rate. The reason for metastasis is largely unknown and the effective treatment is still lacking. Although over-expression of ASPH has been demonstrated to enhance hepatocellular carcinoma invasiveness, whether its hydroxylase activity is necessary remains uncharacterized. Here, we found the hydroxylase activity was critical to promote hepatocellular carcinoma invasiveness in vitro and metastasis in vivo, and associated with post-surgery survival. ASPH hydroxylase activity play an important role in epithelial-to-mesenchymal transition through interacting with vimentin. Our findings imply that ASPH antagonists might be promising in developing novel therapy.