The tumour-associated antigen L6 (L6-Ag) is recruited to the tetraspanin-enriched microdomains: implication for tumour cell motility

Tumour-associated antigen L6 (L6-Ag, also known as TM4SF1) regulates tumour cell motility and invasiveness. We found that L6-Ag is abundant on the plasma membrane and on intracellular vesicles, on which it is co-localised with the markers for late endosomal/lysosomal compartments, including Lamp1/Lamp2 proteins and LBPA. Antibody internalisation and live-imaging experiments suggested that L6-Ag is targeted to late endocytic organelles (LEO) predominantly via a biosynthetic pathway. Mapping experiments showed that the presence of transmembrane regions is sufficient for directing L6-Ag to LEO. On the plasma membrane, L6-Ag is associated with tetraspanin-enriched microdomains (TERM). All three predicted cytoplasmic regions of L6-Ag are crucial for the effective recruitment of the protein to TERM. Recruitment to TERM correlated with the pro-migratory activity of L6-Ag. Depletion of L6-Ag with siRNA has a selective effect on the surface expression of tetraspanins CD63 and CD82. By contrast, the expression levels of other tetraspanins and β1 integrins was not affected. We found that L6-Ag is ubiquitylated and that ubiquitylation is essential for its function in cell migration. These data suggest that L6-Ag influences cell motility via TERM by regulating the surface presentation and endocytosis of some of their components

Computed Tomography Measurement of Hepatic Steatosis: Prevalence of Hepatic Steatosis in a Canadian Population

Background/Aims. Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease that can progress to cirrhosis and hepatocellular carcinoma. This retrospective chart review investigated the incidence of hepatic steatosis in London, Ontario, Canada. Methods. A retrospective chart review was performed on emergency room (ER) patients undergoing nonscheduled computed tomography (CT) imaging over a six-month period in London, Ontario. CT images and reports were examined to determine presence of steatosis. Analyses of the electronic chart for a period of six months following the CT and communication with the patients’ family doctors were used to determine if there was follow-up. Waist circumference, subcutaneous fat depth, and abdominal fat volumes were calculated. Results. 48/450 patients meeting inclusion criteria were identified by radiology as having steatosis, with 34/40 (85%) family physicians unaware of the finding. 24.7% (100/405) of patients met standard CT criteria for steatosis, 40 of which were reported by the radiologist. Waist circumference, subcutaneous adipose tissue depth, subcutaneous adipose tissue volume, and visceral adipose tissue volume were significantly associated with steatosis. Conclusions. The hepatic steatosis prevalence we report is the first reported in a Canadian population. Early identification of steatosis will become more important as new pharmacologic therapies arise

Adenosine A2A and A2B receptor expression in neuroendocrine tumours: potential targets for therapy

The clinical management of neuroendocrine tumours is complex. Such tumours are highly vascular suggesting tumour-related angiogenesis. Adenosine, released during cellular stress, damage and hypoxia, is a major regulator of angiogenesis. Herein, we describe the expression and function of adenosine receptors (A1, A2A, A2B and A3) in neuroendocrine tumours. Expression of adenosine receptors was investigated in archival human neuroendocrine tumour sections and in two human tumour cell lines, BON-1 (pancreatic) and KRJ-I (intestinal). Their function, with respect to growth and chromogranin A secretion was carried out in vitro. Immunocytochemical data showed that A2A and A2B receptors were strongly expressed in 15/15 and 13/18 archival tumour sections. Staining for A1 (4/18) and A3 (6/18) receptors was either very weak or absent. In vitro data showed that adenosine stimulated a three- to fourfold increase in cAMP levels in BON-1 and KRJ-1 cells. The non-selective adenosine receptor agonist (adenosine-5′N-ethylcarboxamide, NECA) and the A2AR agonist (CGS21680) stimulated cell proliferation by up to 20–40% which was attenuated by A2B (PSB603 and MRS1754) and A2A (SCH442416) receptor selective antagonists but not by the A1 receptor antagonist (PSB36). Adenosine and NECA stimulated a twofold increase in chromogranin A secretion in BON-1 cells. Our data suggest that neuroendocrine tumours predominantly express A2A and A2B adenosine receptors; their activation leads to increased proliferation and secretion of chromogranin A. Targeting adenosine signal pathways, specifically inhibition of A2 receptors, may thus be a useful addition to the therapeutic management of neuroendocrine tumours