Anti-proliferative Effects of Pinocembrin Isolated From Anomianthus dulcis on Hepatocellular Carcinoma Cells.

BACKGROUND: Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer. Anomianthus dulcis (Dunal) J.Sinclair (syn. Uvaria dulcis) has been used in Thai traditional medicine in various therapeutic indications. Phytochemical constituents of A. dulcis have been isolated and identified. However, their effects on liver cancer and the associated mechanisms have not been elucidated. METHODS: Dry flowers of A. dulcis were extracted using organic solvents, and chromatographic methods were used to purify the secondary metabolites. The chemical structures of the pure compounds were elucidated by analysis of spectroscopic data. Cytotoxicity against HCC cells was examined using SRB assay, and the effects on cell proliferation were determined using flow cytometry. The mechanisms underlying HCC inhibition were examined by molecular docking and verified by Western blot analysis. RESULTS: Among 3 purified flavonoids, pinocembrin, pinostrobin, and chrysin, and 1 indole alkaloid (3-farnesylindole), only pinocembrin showed inhibitory effects on the proliferation of 2 HCC cell lines, HepG2 and Li-7, whereas chrysin showed specific toxicity to HepG2. Pinocembrin was then selected for further study. Flow cytometric analyses revealed that pinocembrin arrested the HCC cell cycle at the G1 phase with a minimal effect on cell death induction. Pinocembrin exerted the suppression of STAT3, as shown by the molecular docking on STAT3 with a better binding affinity than stattic, a known STAT3 inhibitor. Pinocembrin also suppressed STAT3 phosphorylation at both Tyr705 and Ser727. Cell cycle regulatory proteins under the modulation of STAT3, namely cyclin D1, cyclin E, CDK4, and CDK6, are substantially suppressed in their expression levels. CONCLUSION: Pinocembrin extracted from A. dulcis exerted a significant growth inhibition on HCC cells via suppressing STAT3 signaling pathways and its downstream-regulated genes.

γ-aminobutyric acid B2 receptor: A potential therapeutic target for cholangiocarcinoma in patients with diabetes mellitus.

BACKGROUND: The association between diabetes mellitus (DM) and the increased risk and progression of cholangiocarcinoma (CCA) has been reported with unclear underlying mechanisms. Previous studies showed that γ-aminobutyric acid (GABA) B2 receptor (GABBR2) was upregulated in CCA cells cultured in high glucose (HG) conditions. Roles of GABA receptors in CCA progression have also been studied, but their association with DM and hyperglycemia in CCA remains unclarified. AIM: To investigate the effects of hyperglycemia on GABBR2 expression and the potential use of GABBR2 as a CCA therapeutic target. METHODS: CCA cells, KKU-055 and KKU-213A, were cultured in Dulbecco Modified Eagle's Medium supplemented with 5.6 mmol/L (normal glucose, NG) or 25 mmol/L (HG) glucose and assigned as NG and HG cells, respectively. GABBR2 expression in NG and HG cells was investigated using real-time quantitative polymerase chain reaction and western blot. Expression and localization of GABBR2 in CCA cells were determined using immunocytofluorescence. GABBR2 expression in tumor tissues from CCA patients with and without DM was studied using immunohistochemistry, and the correlations of GABBR2 with the clinicopathological characteristics of patients were analyzed using univariate analysis. Effects of baclofen, a GABA-B receptor agonist, on CCA cell proliferation and clonogenicity were tested using the MTT and clonogenic assays. Phospho-kinases arrays were used to screen the affected signaling pathways after baclofen treatment, and the candidate signaling molecules were validated using the public transcriptomic data and western blot. RESULTS: GABBR2 expression in CCA cells was induced by HG in a dose- and time-dependent manner. CCA tissues from patients with DM and hyperglycemia also showed a significantly higher GABBR2 expression compared with tumor tissues from those with euglycemia (P < 0.01). High GABBR2 expression was significantly associated with a poorer non-papillary histological subtype but with smaller sizes of CCA tumors (P < 0.05). HG cells of both tested CCA cell lines were more sensitive to baclofen treatment. Baclofen significantly suppressed the proliferation and clonogenicity of CCA cells in both NG and HG conditions (P < 0.05). Phospho-kinase arrays suggested glycogen synthase kinase 3 (GSK3), ß-catenin, and the signal transducer and activator of transcription 3 (STAT3) as candidate signaling molecules under the regulation of GABBR2, which were verified in NG and HG cells of the individual CCA cell lines. Cyclin D1 and c-Myc, the common downstream targets of GSK3/ß-catenin and STAT3 involving cell proliferation, were accordingly downregulated after baclofen treatment. CONCLUSION: GABBR2 is upregulated by HG and holds a promising role as a therapeutic target for CCA regardless of the glucose condition.

High glucose enhances the aggressiveness of lung adenocarcinoma via activating epidermal growth factor receptor/signal transducer and activator of transcription 3 pathways.

Epidemiological studies revealed hyperglycemia as a poor prognostic factor for lung adenocarcinoma with unclear molecular mechanisms. The present study thus aimed to investigate the effects of high glucose on the progression of lung adenocarcinoma and its underlying mechanisms. Lung adenocarcinoma cell lines, A549 and RERF-LC-KJ, were cultured in 5.6 mM glucose (normal glucose; NG) or 25 mM glucose (high glucose; HG) resembling euglycemia and hyperglycemia. Cells were examined for proliferation by the MTT assay, and migration-invasion using Transwell. The expressions of signaling proteins in epidermal growth factor receptor (EGFR) pathways and their downstream targets were investigated using Western blots. The effects of diabetes mellitus (DM) and hyperglycemia on lung adenocarcinoma growth in vivo were studied in streptozotocin-induced diabetic BALB/cAJcl-Nu/Nu mice and their nondiabetic counterparts. High glucose significantly promoted proliferation, migration, and invasion of lung adenocarcinoma cells compared with those in normal glucose (P<.05). Western blot analyses showed the increased ratio of pEGFR/EGFR in cells cultured in high glucose and subsequently activated the signal transducer and activator of transcription 3 (STAT3). Epithelial-mesenchymal (EMT) markers were also altered in lung adenocarcinoma cells in high glucose conditions, corresponding with increased migration and invasion abilities. Erlotinib, an EGFR inhibitor, significantly reversed high glucose-induced aggressive phenotypes confirming high glucose-enhancing lung adenocarcinoma progression via the activation of EGFR. DM and hyperglycemia also promoted the growth of lung adenocarcinoma xenografts in vivo in which erlotinib significantly suppressed the growth of tumors (P<.05) suggesting EGFR inhibitor as an effective therapeutic agent for lung adenocarcinoma with DM.

Hyperglycemia Alters O-GlcNAcylation Patterns of Hepatocytes in Mice Treated With Hepatoxic Carcinogen.

BACKGROUND/AIM: Diabetes mellitus (DM) is an established risk for hepatocellular carcinoma (HCC), with unclarified mechanisms. This study investigated the effects of hyperglycemia on O-GlcNacylation in hepatocytes and its associations with hepatocarcinogenesis. MATERIALS AND METHODS: Mouse and human HCC cell lines were used in an in vitro model of hyperglycemia. Western blotting was used to determine the effects of high glucose on O-GlcNacylation in HCC cells. Twenty 4-week-old C3H/HeNJcl mice were randomized into four groups: non-DM control, non-DM plus diethylnitrosamine (DEN), DM, and DM plus DEN. DM was induced using intraperitoneal injection of a single high dose of streptozotocin. DEN was used to induce HCC. All mice were euthanized at week 16 after DM induction, and the liver tissues were histologically examined using hematoxylin and eosin, and immunohistochemistry. RESULTS: High glucose increased O-GlcNacylated proteins in mouse and human HCC cell lines compared with those cultured at normal glucose concentration. Mice with hyperglycemia or DEN treatment had increased O-GlcNacylated proteins in hepatocytes. No gross tumors were evident at the end of the experiment but hepatic morbidity was observed. Mice with hyperglycemia and DEN treatment showed greater histological morbidity in their livers, i.e. increased nuclear size, hepatocellular swelling and sinusoidal dilatation, compared with mice in the DM group or treated with DEN alone. CONCLUSION: Hyperglycemia increased O-GlcNAcylation in both in vitro and animal models. Increased O-GlcNAcylated proteins may be associated with hepatic histological morbidities which then promote HCC development in carcinogen-induced tumorigenesis.