Yutaka Yamanaka

15-Deoxy-Δ-12-14-PGJ2 regulates apoptosis induction and nuclear factor-κB activation via a peroxisome proliferator-activated receptor-γ-independent mechanism in hepatocellular carcinoma

The peroxisome proliferator-activated receptor-γ (PPARγ) high-affinity ligand, 15-deoxy-Δ-12,14-PGJ2 (15d-PGJ2), is toxic to malignant cells through cell cycle arrest and apoptosis induction. In this study, we investigated the effects of 15d-PGJ2 on apoptosis induction and expression of apoptosis-related proteins in hepatocellular carcinoma (HCC) cells. 15d-PGJ2 induced apoptosis in SK-Hep1 and HepG2 cells at a 50 μm concentration. Pretreatment with the pan-caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone (2-VAD-fmk), only partially blocked apoptosis induced by 40 μm 15d-PGJ2. This indicated that 15d-PGJ2 induction of apoptosis was associated with a caspase-3–independent pathway. 15d-PGJ2 also induced down-regulation of the X chromosome-linked inhibitor of apoptosis (XIAP), Bclx, and apoptotic protease-activating factor-1 in SK-Hep1 cells but not in HepG2 cells. However, 15d-PGJ2 sensitized both HCC cell lines to TNF-related apoptosis-induced ligand–induced apoptosis. In SK-Hep1 cells, cell toxicity, nuclear factor-κB (NF-κB) suppression, and XIAP down-regulation were induced by 15d-PGJ2 treatment under conditions in which PPARγ was down-regulated. These results suggest that the effect of 15d-PGJ2 was through a PPARγ-independent mechanism. Although cell toxicity was induced when PPARγ was down-regulated in HepG2 cells, NF-κB suppression and XIAP down-regulation were not induced. In conclusion, 15d-PGJ2 induces apoptosis of HCC cell lines via caspase-dependent and -independent pathways. In SK-Hep1 cells, the ability of 15d-PGJ2 to induce cell toxicity, NF-κB suppression, or XIAP down-regulation seemed to occur via a PPARγ-independent mechanism, but in HepG2 cells, NF-κB suppression by 15d-PGJ2 was dependent on PPARγ.

Proteasome inhibition sensitizes hepatocellular carcinoma cells to TRAIL by suppressing caspase inhibitors and AKT pathway.

The ubiquitin–proteasome pathway is responsible for regulating cell cycle proteins, tumor-suppressor molecules, oncogenes, transcription factors, and pro- and anti-apoptotic proteins. The aim of this study is to evaluate the effects of proteasome inhibitors on human hepatocellular carcinoma (HCC) cells. HCC cells SK-Hep1, HLE and HepG2 were treated with the proteasome inhibitors MG132 and MG115. Our data showed that both inhibitors induce apoptosis in the three cell types tested in a dose-dependent manner. Moreover, subtoxic levels of MG132 and MG115 sensitized HCC cells to TRAIL-induced apoptosis. To investigate the mechanism of increased TRAIL sensitivity in HCC cells, we first examined surface expression of TRAIL and its receptors. MG132 upregulated TRAIL and its receptors (TRAIL-R1 and -R2) in SK-Hep1 and HLE, whereas MG115 upregulated them in SK-Hep1. MG132 downregulated expression of X-linked inhibitor of apoptosis protein (XIAP) in SK-Hep1 and HLE, and of survivin in all three cell-types. MG115 downregulated expression of XIAP in SK-Hep1, and survivin in SK-Hep1 and HepG2. Furthermore, MG132 downregulated phospho-AKT and its downstream target phospho-BAD, indicating that MG132 activated the mitochondrial apoptosis pathway by inhibiting phosphorylation of AKT and BAD. In conclusion, proteasome inhibitors induced apoptosis and augmented TRAIL sensitivity via both the IAP family and AKT pathways. Thus, combining proteasome inhibitors with a TRAIL agonist may provide a new therapeutic strategy for HCC.

Hepatobiliary and pancreatic: Cholangiocarcinoma with chylous ascites

Chylous ascites is ascitic fluid with a milky appearance that is rich in triglycerides. The disorder is rare, with a reported frequency of 1 in 20 000 hospital admissions. The most common cause is an intra-abdominal malignancy, usually advanced gastric or pancreatic cancer. The typical mechanism involves obstruction or malignant infiltration of lymphatic channels with the subsequent development of a lymphatic fistula that communicates with the peritoneal cavity. Non-malignant causes of chylous ascites include cirrhosis, tuberculosis, filariasis, abdominal trauma, abdominal surgery and abdominal irradiation. In cirrhosis, the mechanism for chylous ascites might involve increases in lymphatic flow leading to increases in pressure and the rupture of small lymphatic channels. The investigations illustrated below were from a 60-year-old woman who presented with epigastric pain, abdominal fullness and weight loss. She had hepatitis C and had previously had a cholecystectomy. A computed tomography scan showed ascites and a mass near the hilum of the liver consistent with cholangiocarcinoma. An ascitic tap revealed milky fluid with a triglyceride level of 285 mg/dL (3.2 mmol/L). Ascitic fluid cytology was positive for malignant cells. Her serum triglyceride level was 60 mg/dL (0.7 mmol/L) and she had an elevated serum concentration of the tumor marker, Ca19.9. An upper gastrointestinal endoscopy showed multiple white dots in the second part of the duodenum (Fig. 1). Histological evaluation of duodenal biopsies revealed mild inflammation and dilated submucosal lymphatics. A lymphangiogram was performed by injecting 99mTc-labeled human serum albumin into both feet. At 10 min, the label was detected in the mid-abdomen (anterior and posterior views) and, at 4 h, there was partial obstruction of abdominal lymphatic channels (Fig. 2). Some of the label leaked into the peritoneal cavity and was subsequently absorbed into the general circulation. An autopsy at 5 months after the initial presentation confirmed the presence of widespread cholangiocarcinoma.

Second‑line triple therapy in failures with vonoprazan‑based triple therapy for eradication of Helicobacter pylori

Gastric acid inhibition during treatment is important for the eradication of Helicobacter pylori (H. pylori) infection. A novel potassium-competitive acid blocker, vonoprazan (VPZ), has been demonstrated to achieve high eradication rates; however, the efficacy of second-line treatment in failures of VPZ-based triple therapy has not been well studied. The aim of the current study was to determine the efficacy of VPZ in a first-line regimen for H. pylori eradication, and the efficacy of a second-line regimen using metronidazole (MTZ) in failures with the first-line regimen. Of 580 subjects enrolled in the study, 524 patients completed first-line treatment (275 patients who received VPZ and 249 patients who received LPZ). First-line regimens consisted of a combination of clarithromycin (CAM) 200 or 400 mg twice a day, amoxicillin (AMPC) 750 mg twice a day, and either LPZ 30 mg or VPZ 20 mg twice a day, administered orally for 7 days. CAM and VPZ/LPZ were replaced with metronidazole (MTZ) 250 mg and rabeprazole 10 mg in the second-line regimens. The eradication of H. pylori was assessed by the H. pylori stool antigen test. The overall first-line eradication rate with VPZ was significantly higher than that with LPZ [91.0% (250/275) vs. 84.7% (211/249), respectively, P=0.030]. The dose of CAM (400 vs. 800 mg) did not affect the eradication rate in either the VPZ or LPZ regimens. The overall eradication rates of the second-line regimens with MTZ did not differ significantly between the VPZ-failure and LPZ-failure groups [87.0% (20/23) vs. 87.9% (29/33), respectively, P=0.700]. Therefore, VPZ was significantly more effective than LPZ for first-line treatment. In patients with failure of first-line eradication therapy, successful results of second-line eradication therapy did not differ between the VPZ- and LPZ-failure groups. In conclusion, VPZ-based triple therapy should be recommended for eradication of H. pylori.

Hepatobiliary and pancreatic: Tumor thrombi in esophageal varices

The patient whose investigations are shown below had cirrhosis caused by hepatitis C and multiple hepatocellular carcinomas. He was treated with 10 courses of arterial infusion chemotherapy using cisplatin and 5-fluorouracil. After the last course of chemotherapy, the patient’s esophageal varices increased in size (Fig. 1). One week later, he had hematemesis as a result of bleeding varices and was treated by endoscopic injection sclerotherapy. The episodes of bleeding continued despite several further courses of endoscopic therapy. He subsequently died from liver failure. At autopsy, he had several tumors within the liver and tumor invasion of the intrahepatic portal veins. Histological evaluation revealed moderately to poorly differentiated hepatocellular carcinomas and tumor thrombi in esophageal varices (Fig. 2). At autopsy, only a minority of patients with hepatocellular cancer have tumors restricted to the liver. The majority have metastases, particularly metastases in the lungs, abdominal lymph nodes and in contiguous areas in the upper abdomen. It is also common for hepatocellular cancers to invade the hepatic vasculature. For example, tumors are often found in intrahepatic portal veins and this extends into the main trunk of the portal vein in approximately onethird of patients. Invasion of the main trunk of the hepatic vein may be less frequent but spread to the inferior vena cava and right atrium has been described. In the present patient, it seems likely that tumor thrombi in esophageal varices resulted from retrograde flow within the portal vein. This would permit tumor thrombi to pass from the portal vein into the left gastric vein and become lodged in esophageal varices. Other explanations such as the systemic spread of neoplastic cells to esophageal varices seem unlikely. Whether difficulties with endoscopic control of bleeding were related to tumor thrombi in esophageal varices or to high portal pressures remains unclear.