ABSTRACT
PET with 18F-fluoro-2-deoxy-glucose (FDG) is well established as an effective imaging modality for evaluating suspected brain tumor recurrence. Use of FDG PET imaging for spinal cord neoplasms has not yet been studied, in large part due to limitations of spatial resolution. One report of FDG PET imaging of brain involvement with primitive neuroectodermal tumor (PNET) demonstrated mild hypometabolism relative to cortical gray matter. We demonstrate with FDG PET imaging the appearance of recurrent intramedullary PNET affecting the cervical spinal cord.
Subject(s)
Fluorine Radioisotopes , Fluorodeoxyglucose F18 , Neoplasm Recurrence, Local/diagnostic imaging , Neuroectodermal Tumors, Primitive/diagnostic imaging , Radiopharmaceuticals , Spinal Cord Neoplasms/diagnostic imaging , Tomography, Emission-Computed , Adult , Feasibility Studies , Humans , MaleABSTRACT
The regulation of cholesterol esterification during cell proliferation was studied. The serum free cholesterol, cholesterol esters and lecithin: cholesterol acyltransferase (LCAT) activity of nude mice with and without pancreatic acinar cell tumours and rats with proliferating tissues were determined. In addition, the apparent activity of acyl-CoA: cholesterol acyltransferase (ACAT) in homogenates of nude mouse tumours and proliferating rat tissues were determined and compared with those of normal nude mouse and rat tissues. Serum cholesterol ester levels were significantly lower in host nude mice with tumours and in rats with regenerating liver, and increased significantly in pregnant rats when compared with respective controls. Circulating LCAT activity levels decreased in host nude mice, in pregnant rats, and in rats with regenerating pancreas and regenerating liver. Apparent ACAT activity levels increased significantly in nude mouse tumours and in foetal and postnatal rat pancreata and also in postnatal liver. At the same time, apparent ACAT activity levels decreased in foetal and regenerating rat livers when compared with respective control tissues. These results suggest that serum cholesterol esters, circulating LCAT and cellular ACAT levels are modulated during cell proliferation.
Subject(s)
Carcinoma/metabolism , Cholesterol Esters/metabolism , Pancreatic Neoplasms/metabolism , Animals , Carcinoma/blood , Carcinoma/enzymology , Cholesterol/blood , Cholesterol Esters/blood , Esterification , Female , Male , Mice , Mice, Nude , Pancreatic Neoplasms/blood , Pancreatic Neoplasms/enzymology , Phosphatidylcholine-Sterol O-Acyltransferase/blood , Rats , Rats, Inbred Strains , Sterol O-Acyltransferase/metabolismABSTRACT
The mechanism of deregulation of cholesterol metabolism was studied in fast and slow growing nude mouse tumors and cancer cells in culture derived from azaserine-induced rat pancreatic acinar cell carcinoma. The tumors showed a loss of feedback control of the de novo synthesis of cholesterol, probably due to a loss of low density lipoprotein (LDL) receptors on plasma membranes or to a defect in the binding and internalization of LDL in the cancer cells. The hexosemonophosphate shunt pathway is stimulated in the cancer cells, presumably because of an increased demand for NADPH in cholesterol synthesis and for ribose phosphate in DNA synthesis. The uncontrolled de novo synthesis of cholesterol is one of the factors responsible for the high rate of cell proliferation in the tumors.
Subject(s)
Cholesterol/biosynthesis , Lovastatin/analogs & derivatives , Pancreatic Neoplasms/metabolism , Animals , Cells, Cultured , Cholesterol, Dietary/metabolism , DNA/biosynthesis , Female , Glucosephosphate Dehydrogenase/metabolism , Injections, Intraperitoneal , Liver/metabolism , Male , Mice , Mice, Inbred BALB C , Naphthalenes/pharmacology , Rats , Rats, Inbred Strains , Receptors, LDL/metabolismABSTRACT
The lipid composition and 3-hydroxy-3-methylglutaryl-CoA reductase activity of subcutaneous transplantable pancreatic acinar cell tumors on nude mice were compared with those of normal, regenerating, fetal and newborn rat pancreata. The tumors and also the fetal tissues showed decreased concentration in total lipids, increased concentration in sphingomyelin and an increase in cholesterol when compared to normal rat pancreas. The regenerating pancreas showed an intermediate elevation in these lipid parameters. Specifically, only tumor showed an increase in phosphatidylethanolamine/phosphatidylcholine ratio. The tumors and also the fetal tissues showed an increase in hydroxymethylglutaryl-CoA reductase activities, suggesting that the de novo synthesis of cholesterol is a requirement for cell proliferation. The cholesterol metabolism in normal tissues is under metabolic regulation as indicated by decreased hydroxymethylglutaryl-CoA reductase activities and decreased cholesterol concentration in postnatal tissues when compared with the fetal tissues. The fast growing AT3A tumor showed higher hydroxymethylglutaryl-CoA reductase activity when compared to the slow growing AT3B tumor, indicating that the differences in growth rate of the tumors may be related at least in part to differences in their cholesterol metabolism.