OBJECTIVES: a) To elucidate the chemical composition of protein-lipid complexes of a proteolipid type, tentatively called neoproteolipids, isolated from malignant tumors; b) To determine the degree of specificity of association of these complexes with malignant growth; c) To investigate the appearance (or raised level) of these complexes in blood sera in order to serve as a potential diagnostic cancer test and/or as a test of the efficacy of the medical treatment of cancer. APPROACH AND PROGRESS: From the lower phase of Folch-partitions of lipid extracts from tumors, protein-lipid complexes, neoproteolipids (NPL), have been isolated on systems of silicic acid chromatography columns. There are two types of NPL: neoproteolipid-W (NPL-W), originally isolated from Walker carcinosarcoma 256 (W256), and neoproteolipid-S (NPL-S), originally isolated from Sarcoma 180. Around 20 different transplanted, chemically-induced and spontaneous tumors (including human tumors) were tested, and all of them contained either NPL-W or NPL-S. Both neoproteolipids are complexes of glycosphingolipids with other lipids (phospholipids, cholesterol) and proteins (or polypeptides). NPL-W contains neutral glycosphingolipids (which contain fucose), whereas NPL-S contains sialoglycosphingolipids as has been determined by gas-liquid chromatography. Blood sera of normal rats do not contain NPL-W, whereas the sera of W256-bearing rats do contain around 16 micron g NPL-W/100 mg lipid. Blood sera from Morris hepatoma 5123-bearing rats contain 5-7 times more NPL-S than sera from normal rats. The presence of NPL (without identification of its type) was demonstrated also in sera of cancer patients with advanced forms of cancer. BIBLIOGRAPHIC REFERENCES: V. P. Skipski, N. Katopodis, J. S. Prendergast and C. C. Stock. Gangliosides in Blood serum of normal rats and Morris hepatoma 513tc-bearing rats. Biochem. Biophys. Res. Commun. 67:1122-1127, 1975. V.P. Skipski, M. Barclay, F. M. Archibald and C.C. Stock. Tumor Proteolipids. Prog. Biochem. Pharmacol. 10:112-134, 1975.