Myoung-Kuk Jang

Clinical aspects of tumor necrosis factor-α signaling in hepatocellular carcinoma.

Tumor necrosis factor alpha (TNF-α) is a multi-functional cytokine that regulates a variety of signaling pathways implicated in inflammation, immunity, cell death (apoptosis), cell survival (anti-apoptosis), and even tumorigenesis. TNF-α is predominantly produced by macrophages (or Kupffer cells within the liver), but generated by lymphoid cells, astrocytes, endothelial cells, and smooth muscle cells to some degree. In the liver, TNF-α not only serves as a key mediator of hepatocyte apoptosis resulting in the liver damage, but also plays an important role in cellular proliferation leading to liver regeneration or even hepatocarcinogenesis. TNF-α may indirectly contribute to carcinogenesis via various inflammatory conditions such as alcoholic and non-alcoholic fatty liver diseases and chronic viral hepatitis. On the one hand, in inflammation, TNF-α induces apoptosis repeatedly and subsequently enhances the chance of formation of anomalous cells during the process of regeneration and dysplasia. On the other hand, TNF-α exerts as an anti-angiogenic factor depending on its concentration. It shows an anti-tumorous effect by increasing vascular permeability in the tumors. When it is perfused in combination with chemotherapeutic drugs using isolated hepatic infusion, TNF-α may increase the responsiveness of hepatocellular carcinoma (HCC) or metastatic cancers to anti-cancer agents as isolated limb perfusion methods in an unresectable soft tissue sarcoma or melanoma. This article reviews the TNF-α signaling pathway in hepatocarcinogenesis and the new challenge of TNF-α as a new therapeutic strategy in HCC.

Single nucleotide polymorphisms associated with metastatic tumour antigen 1 overexpression in patients with hepatocellular carcinoma

Metastatic tumour antigen 1 (MTA1) promotes angiogenesis by stabilizing hypoxia‐inducible factor‐1α (HIF‐1α), which is closely associated with frequent postoperative recurrence and poor survival in patients with HCC. In this study, we determined single nucleotide polymorphisms (SNPs) in angiogenesis‐related genes that are associated with MTA1 overexpression in HCC tissues.

SAMHD1 acetylation enhances its deoxynucleotide triphosphohydrolase activity and promotes cancer cell proliferation

SAM domain and HD domain containing protein 1 (SAMHD1) is a deoxynucleotide triphosphohydrolase (dNTPase) that inhibits retroviruses by depleting intracellular deoxynucleotide triphosphates (dNTPs) in non-cycling myeloid cells. Although SAMHD1 is expressed ubiquitously throughout the human body, the molecular mechanisms regulating its enzymatic activity and function in non-immune cells are relatively unexplored. Here, we demonstrate that the dNTPase activity of SAMHD1 is regulated by acetylation, which promotes cell cycle progression in cancer cells. SAMHD1 is acetylated at residue lysine 405 (K405) in vitro and in vivo by an acetylatransferase, arrest defective protein 1 (ARD1). Acetylated SAMHD1 wildtype proteins have enhanced dNTPase activity in vitro, whereas non-acetylated arginine substituted mutants (K405R) do not. K405R mutant expressing cancer cells have reduced G1/S transition and slower proliferation compared to wildtype. SAMHD1 acetylation levels are strongest during the G1 phase, indicating a role during G1 phase. Collectively, these findings suggest that SAMHD1 acetylation enhances its dNTPase activity and promotes cancer cell proliferation. Therefore, SAMHD1 acetylation may be a potent therapeutic target for cancer treatment.

ARD1/NAA10 in hepatocellular carcinoma: pathways and clinical implications

Hepatocellular carcinoma (HCC), a representative example of a malignancy with a poor prognosis, is characterized by high mortality because it is typically in an advanced stage at diagnosis and leaves very little hepatic functional reserve. Despite advances in medical and surgical techniques, there is no omnipotent tool that can diagnose HCC early and then cure it medically or surgically. Several recent studies have shown that a variety of pathways are involved in the development, growth, and even metastasis of HCC. Among a variety of cytokines or molecules, some investigators have suggested that arrest-defective 1 (ARD1), an acetyltransferase, plays a key role in the development of malignancies. Although ARD1 is thought to be centrally involved in the cell cycle, cell migration, apoptosis, differentiation, and proliferation, the role of ARD1 and its potential mechanistic involvement in HCC remain unclear. Here, we review the present literature on ARD1. First, we provide an overview of the essential structure, functions, and molecular mechanisms or pathways of ARD1 in HCC. Next, we discuss potential clinical implications and perspectives. We hope that, by providing new insights into ARD1, this review will help to guide the next steps in the development of markers for the early detection and prognosis of HCC.Liver cancer: The search for an early-stage indicatorA protein that is highly expressed in cancer with extensive blood vessel development may provide a potential biomarker for early-stage liver cancer. Liver cancer is often not diagnosed until it is advanced and is also hard to be cured despite of advances in treatment, meaning patients often die from the disease. No tools for early detection or prognosis prediction exist, and scientists are keen to find useful biomarker molecules. Young-Hwa Chung at the University of Ulsan College of Medicine, Asan Medical Center, Seoul, and co-workers in South Korea reviewed recent research into one possible cancer-related protein, arrest-defective 1 (ARD1), known to be highly expressed in certain cancers and possibly associated with poor prognosis. While ARD1 appears to regulate pathways critical to cancer progression and promote cancer cell invasiveness, further in-depth investigations are needed to clarify its specific role in liver cancer.

Accumulation of citrullinated glial fibrillary acidic protein in a mouse model of bile duct ligation-induced hepatic fibrosis

Hepatic stellate cells (HSCs) play pivotal roles in hepatic fibrosis as they synthesize glial fibrillary acidic protein (GFAP), which is increased in activated HSCs. GFAP-expressing HSCs and myofibroblasts accumulate in and around hepatic fibrosis lesions. Peptidylarginine deiminase 2 (PAD2) is responsible for the citrullination of GFAP (cit-GFAP). However, the involvement of PAD2 and cit-GFAP in hepatic fibrosis remains unclear. To determine the expression of PAD2 and cit-GFAP in hepatic fibrosis, C57BL/6 mice underwent bile duct ligation (BDL) or a sham operation. In BDL livers, the expression of PAD2 and its enzyme activity were significantly increased compared with controls. In addition, PAD2-postitive cells were rarely observed in only the portal vein and the small bile duct in sham-operated livers, whereas an increased number of PAD2-positive cells were detected in the bile duct and Glisson’s sheath in BDL livers. Interestingly, PAD2 was colocalized with α-SMA-positive cells and CK19-positive cells in BDL livers, indicating upregulated PAD2 in activated HSCs and portal fibroblasts of the livers of BDL mice. We also found that citrullinated proteins were highly accumulated in the livers of BDL mice compared with controls. Moreover, the expression level of GFAP and the amount of cit-GFAP were higher in BDL livers than in control livers. In correlation with PAD2 localization, cit-GFAP was observed in α-SMA-positive and CK19-positive cells in the livers of BDL mice. These results suggest that the increased expression and activation of PAD2 along with increased citrullinated proteins, specifically cit-GFAP, may play important roles in the pathogenesis of hepatic fibrosis.

Vesicoileal Fistula in a Patient with Hematochezia and Hematuria

To the Editor: Vesicoenteric fistula usually develops as a complication of colonic diverticulitis, although other conditions, such as colorectal cancer, Crohns disease, and bladder cancer, may be ...