Plasma lipoproteins of leukemic guinea pigs (L2C) can regulate cholesterol biosynthesis by lymphocytes of normal guinea pigs. A comparative study of plasma lipoproteins of normal and neoplastic animals.

The defect of regulation of cholesterol biosynthesis by leukemic (L2C) guinea pig lymphocytes is not a consequence of serum lipoprotein modifications which would make them unable to participate in the regulatory process. Low density lipoprotein of leukemic animals, in parallel to normal low density lipoprotein, can inhibit the cholesterol biosynthesis by normal cells. Surprisingly, very low density lipoprotein of leukemic animals have the same inhibitory property. Analyses of serum of leukemic animals showed a larger amount of the different lipoprotein fractions (+323% very low density, +27% low density lipoproteins, the high density lipoprotein staying undetectable in control and leukemic sera) than in normal serum. L2C leukemia produces low density lipoprotein slightly richer in unesterified cholesterol and very low density lipoprotein markedly modified by an increased proportion of unesterified cholesterol, phospholipids and apoprotein B. The inhibitory power of leukemic very low density lipoprotein is discussed by analogy with corresponding power of normal low density lipoprotein which can operate either by the way of binding to the low density lipoprotein receptor or by exchange of unesterified cholesterol between the lipoprotein and the cell.