Isolation and Characterization of a Cellular Protein-Lipid Complex from Ascites Fluid Caused by Various Neoplasms

High concentrations of lipids in ascites fluid caused by peritoneal
carcinomatosis have been described recently. Since their nature has
not yet been clarified, we isolated ascitic lipids from 25 patients
with various neoplasms for further characterization. After
chromatography on Sephadex G-100 gels, the ascitic lipids were
fractionated on a Biogel A-5m column in three peaks. The second and
third peaks were identified as low and high density lipoproteins,
which were most likely of plasmatic origin, and represented the
major amounts of ascitic lipids. The first peak was eluted in the
void volume, indicating a molecular weight over 5 million. It
consisted, on the average, of 65.3% protein, 16.2% triglycerides,
7.4% phospholipids, and 7.0% cholesterol. In a CsCl gradient, this
protein-lipid complex floated in the density range from 1.128 to
1.181 g/ml. Sodium dodecyl sulfate: polyacrylamide gel
electrophoresis separated up to 11 protein subunits (Mr 29,000 to
97,000), and electron microscopy revealed globular particles of 36
to 64 nm in diameter. The macromolecular complex showed no
immunological reaction against anti-{alpha}- and
anti-ß-lipoproteins, but a single precipitation line against
anti-liver-specific lipoprotein was seen. The biochemical
characteristics of this protein-lipid complex proved to have a
close relationship to liver-specific lipoprotein. It is most likely
derived from cell membranes of the peritoneum detached by
carcinomatosis.