HACE1, a Potential Tumor Suppressor Gene on 6q21, Is Not Involved in Extranodal Natural Killer/T-Cell Lymphoma Pathophysiology

Targeting the signaling in Epstein-Barr virus-associated diseases: mechanism, regulation, and clinical study

Epstein–Barr virus-associated diseases are important global health concerns. As a group I carcinogen, EBV accounts for 1.5% of human malignances, including both epithelial- and lymphatic-originated tumors. Moreover, EBV plays an etiological and pathogenic role in a number of non-neoplastic diseases, and is even involved in multiple autoimmune diseases (SADs). In this review, we summarize and discuss some recent exciting discoveries in EBV research area, which including DNA methylation alterations, metabolic reprogramming, the changes of mitochondria and ubiquitin-proteasome system (UPS), oxidative stress and EBV lytic reactivation, variations in non-coding RNA (ncRNA), radiochemotherapy and immunotherapy. Understanding and learning from this advancement will further confirm the far-reaching and future value of therapeutic strategies in EBV-associated diseases.

Loss of the Tumor Suppressor HACE1 Contributes to Cancer Progression

HACE1 belongs to the family of HECT domain-containing E3 ligases, which plays an important role in the occurrence, invasion and metastatic process in many human malignancies. HACE1 is a tumor suppressor gene that is reduced in most cancer tissues compared to adjacent normal tissue. The loss or knocking out of HACE1 leads to enhanced tumor growth, invasion, and metastasis; in contrast, the overexpression of HACE1 can inhibit the development of tumors. Hypermethylation reduces the expression of HACE1, thereby promoting tumor development. HACE1 can inhibit the development of inflammation or tumors via the ubiquitination pathway. Therefore, HACE1 may be a potential therapeutic target, providing new strategies for disease prevention and treatment.

Epstein-Barr Virus-Positive Natural Killer/T-Cell Lymphoma

Extranodal natural killer/T-cell lymphoma, nasal type (ENKL), is a rare malignancy of Non-Hodgkin lymphoma characterized by an aggressive clinical course and poor prognosis. It shows strong association with Epstein-Barr virus infection and occurs more commonly in Asia and Latin America. Various genetic alterations have been identified in ENKL by gene expression profiling and sequencing techniques. The frequent deletion of chromosome 6q21 was reported to lead to the silence of several tumor suppressor genes. Also, there have been novel genetic mutations that were recently uncovered and were found to frequently activate several oncogenic pathways, including the JAK/STAT, NF-κB, and MAPK pathways. Besides, we believe that deregulated single genes and epigenetic dysregulation might be relevant to the mechanism of this disease and thus, may have the potential to shed lights on the development of new therapeutic strategies. The consensus on the standard treatment for ENKL has not yet been currently established. For localized ENKL patients, radiotherapy with concurrent chemotherapy and sequential patterns of chemotherapy and radiotherapy are recommended as first-line therapy. As for advanced or relapsed/refractory ENKL patients, the application of non-anthracycline-containing regimens have significantly improved the clinical outcome, contributing to higher response rate, longer overall survival and progression-free survival. Hematopoietic stem cell transplantation is widely recommended for consolidation after a complete remission or partial remission has been achieved. The anti-programmed death 1 antibody, an immune checkpoint inhibitor, has demonstrated favorable results in treating relapsed or refractory ENKL. Of the current ENKL treatment, researchers are still striving to validate how radiotherapy and chemotherapy should be optimally combined and which of the non-anthracycline-containing regimens is superior. In this review, we summarize the main genetic alterations frequently found in ENKL and their role in providing new insights into the therapeutic targets of this disease, and highlight the recent findings regarding new biologic markers, novel therapeutic strategies applied to this intriguing neoplasm.

Advances in multiple omics of natural-killer/T cell lymphoma

Natural-killer/T cell lymphoma (NKTCL) represents the most common subtype of extranodal lymphoma with aggressive clinical behavior. Prevalent in Asians and South Americans, the pathogenesis of NKTCL remains to be fully elucidated. Using system biology techniques including genomics, transcriptomics, epigenomics, and metabolomics, novel biomarkers and therapeutic targets have been revealed in NKTCL. Whole-exome sequencing studies identify recurrent somatic gene mutations, involving RNA helicases, tumor suppressors, JAK-STAT pathway molecules, and epigenetic modifiers. Another genome-wide association study reports that single nucleotide polymorphisms mapping to the class II MHC region on chromosome 6 contribute to lymphomagenesis. Alterations of oncogenic signaling pathways janus kinase-signal transducer and activator of transcription (JAK-STAT), nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK), WNT, and NOTCH, as well as epigenetic dysregulation of microRNA and long non-coding RNAs, are also frequently observed in NKTCL. As for metabolomic profiling, abnormal amino acids metabolism plays an important role on disease progression of NKTCL. Of note, through targeting multiple omics aberrations, clinical outcome of NKTCL patients has been significantly improved by asparaginase-based regimens, immune checkpoints inhibitors, and histone deacetylation inhibitors. Future investigations will be emphasized on molecular classification of NKTCL using integrated analysis of system biology, so as to optimize targeted therapeutic strategies of NKTCL in the era of precision medicine.

The Genomics and Molecular Biology of Natural Killer/T-Cell Lymphoma: Opportunities for Translation

Extranodal NK/T-cell lymphoma, nasal type (ENKTL), is an aggressive malignancy with a poor prognosis. While the introduction of L-asparaginase in the treatment of this disease has significantly improved the prognosis, the outcome of patients relapsing after asparaginase-based chemotherapy, which occurs in up to 50% of patients with disseminated disease, remains dismal. There is hence an urgent need for effective targeted therapy especially in the relapsed/refractory setting. Gene expression profiling studies have provided new perspectives on the molecular biology, ontogeny and classification of ENKTL and further identified dysregulated signaling pathways such as Janus associated kinase (/Signal Transducer and activation of transcription (JAK/STAT), Platelet derived growth factor (PDGF), Aurora Kinase and NF-κB, which are under evaluation as therapeutic targets. Copy number analyses have highlighted potential tumor suppressor genes such as PR Domain Zinc Finger Protein 1 (PRDM1) and protein tyrosine phosphatase kappa (PTPRK) while next generation sequencing studies have identified recurrently mutated genes in pro-survival and anti-apoptotic pathways. The discovery of epigenetic dysregulation and aberrant microRNA activity has broadened our understanding of the biology of ENKTL. Importantly, immunotherapy via Programmed Cell Death -1 (PD-1) and Programmed Cell Death Ligand1 (PD-L1) checkpoint signaling inhibition is emerging as an attractive therapeutic strategy in ENKTL. Herein, we present an overview of the molecular biology and genomic landscape of ENKTL with a focus on the most promising translational opportunities.

Uncovering and deciphering the pro-invasive role of HACE1 in melanoma cells

HACE1 is an E3 ubiquitin ligase described as a tumour suppressor because HACE1-knockout mice develop multi-organ, late-onset cancers and because HACE1 expression is lost in several neoplasms, such as Wilms' tumours and colorectal cancer. However, a search of public databases indicated that HACE1 expression is maintained in melanomas. We demonstrated that HACE1 promoted melanoma cell migration and adhesion in vitro and was required for mouse lung colonisation by melanoma cells in vivo. Transcriptomic analysis of HACE1-depleted melanoma cells revealed an inhibition of ITGAV and ITGB1 as well changes in other genes involved in cell migration. We revealed that HACE1 promoted the K27 ubiquitination of fibronectin and regulated its secretion. Secreted fibronectin regulated ITGAV and ITGB1 expression, as well as melanoma cell adhesion and migration. Our findings disclose a novel molecular cascade involved in the regulation of fibronectin secretion, integrin expression and melanoma cell adhesion. By controlling this cascade, HACE1 displays pro-tumoural properties and is an important regulator of melanoma cell invasive properties.

Inhibition of sonic hedgehog signaling blocks cell migration and growth but induces apoptosis via suppression of FOXQ1 in natural killer/T-cell lymphoma

The present study explored the effects of Forkhead box Q1 (FOXQ1) on cell proliferation, cell cycle and apoptosis via the Sonic hedgehog (Shh) pathway in Natural killer/T-cell lymphoma (NKTCL). Quantitative real time-polymerase chain reaction (qRT-PCR) was performed to detect FOXQ1 expression in 117 NKTCL patients and 120 healthy controls. Additionally, FOXQ1 expression in NKTCL cell lines (HANK-1, NK-92, SNK-6, SNT-8 and YT) was determined by western blotting and qRT-PCR. SNK-6 cells were transfected with FOXQ1-shRNA or Shh pathway inhibitor Cyclopamine/recombinant protein Shh. Cell counting kit-8 (CCK-8) and 5-bromo-2-deoxy-uridine (BrdU) incorporation assays were conducted to detect cell proliferation, flow cytometry was used to determine the cell cycle and cell apoptosis, and western blotting was used to detect protein expression. FOXQ1 expression was higher in NKTCL patients than in healthy controls, which was related to Ann Arbor stage, bone marrow involvement and the 5year survival rate in NKTCL patients. Moreover, FOXQ1 expression, pathological type, Ann Arbor stage, B symptom and bone marrow involvement were independent risk factors in NKTCL. Shh pathway-related proteins were down-regulated after transfection of SNK-6 cells with FOXQ1-shRNA. Additionally, SNK-6 cell proliferation was greatly reduced, the cell cycle was blocked at the G0/G1 phase, and the expression of CyclinD1 and CyclinE was markedly decreased, while an increase in cell apoptosis with elevated Bcl-2-associated X protein (Bax) and Caspase-3 and reduced B-cell lymphoma/leukemia-2 (Bcl-2) were also observed. However, no significant alterations were observed between the FOXQ1-shRNA+Shh and Blank groups. The inhibition of FOXQ1 restricted NKTCL cell proliferation and growth but induced apoptosis via blocking the Shh signaling pathway.

Tumor-suppressive role of HACE1 in hepatocellular carcinoma and its clinical significance

An increasing body of evidence suggests that downregulation or deletion of HECT domain and ankyrin repeat containing E3 ubiquitin protein ligase 1 (HACE1) gene plays an important role in the occurrence, invasion and metastasis process in many human malignancies and is closely related to prognosis. However, sparse evidence exists concerning the precise function and clinical significance of HACE1 in hepatocellular carcinoma (HCC). In the present study, we investigated the expression pattern of HACE1 in HCC tissues and cell lines, and determined the potential functions of HACE1 in HCC cell lines and evaluated the relationships between HACE1 expression and clinicopathological characteristics. Protein and mRNA expression levels of HACE1 in human HCC tissues and cell lines were examined by western blot analysis, quantitative real‑time polymerase chain reaction and immunohistochemical (IHC) analyses. IHC was used to analyze the correlations between HACE1 expression and clinicopathological features. HACE1 was upregulated in SMCC7721 cells by transfection with pcDNA3.1-HACE1 and Huh7 cells were transfected with siRNA targeting HACE1 for downregulation. Cell Counting Κit-8, Transwell and wound healing assays were performed to investigate the effects of the overexpression and knockdown of HACE1 on cellular proliferation and migration. The results revealed that HACE1 expression was lower in the HCC tissues and cell lines at the mRNA and protein levels compared to levels noted in the matched non‑tumor tissues and the normal liver cell line L02. Knockdown of HACE1 in Huh7 cells accelerated cell proliferation and migration (P<0.05), and overexpression of HACE1 in SMCC7721 cells was found to decrease the capacity for proliferation and migration (P<0.01). The results of IHC suggested that the HACE1 expression level was closely related to the serum AFP level, tumor differentiation and vascular invasion (P<0.05). Patients with low HACE1 expression levels exhibited poorer overall survival and HACE1 was found to be an independent prognostic factor for survival. In conclusion, as a tumor suppressor, HACE1 may be a valuable prognostic biomarker and potential therapeutic target for HCC treatment.

HACE1 Negatively Regulates Virus-Triggered Type I IFN Signaling by Impeding the Formation of the MAVS-TRAF3 Complex

During virus infection, the cascade signaling pathway that leads to the production of proinflammatory cytokines is controlled at multiple levels to avoid detrimental overreaction. HACE1 has been characterized as an important tumor suppressor. Here, we identified HACE1 as an important negative regulator of virus-triggered type I IFN signaling. Overexpression of HACE1 inhibited Sendai virus- or poly (I:C)-induced signaling and resulted in reduced IFNB1 production and enhanced virus replication. Knockdown of HACE1 expression exhibited the opposite effects. Ubiquitin E3 ligase activity of the dead mutant HACE1/C876A had a comparable inhibitory function as WT HACE1, suggesting that the suppressive function of HACE1 on virus-induced signaling is independent of its E3 ligase activity. Further study indicated that HACE1 acted downstream of MAVS and upstream of TBK1. Mechanistic studies showed that HACE1 exerts its inhibitory role on virus-induced signaling by disrupting the MAVS-TRAF3 complex. Therefore, we uncovered a novel function of HACE1 in innate immunity regulation.