Journal of Lipid Research, Vol 28, 1177-1184, Copyright © 1987 by Lipid Research, Inc.
Abnormal cholesterol metabolism in renal clear cell carcinoma
RL Gebhard, RV Clayman, WF Prigge, R Figenshau, NA Staley, C Reesey and A Bear
Department of Medicine, VA Medical Center, Minneapolis, MN.
The clear cell form of renal cell carcinoma is known to derive its
histologic appearance from accumulations of glycogen and lipid. We have
found that the most consistently stored lipid form is cholesteryl ester.
Clear cell cancer tissue contained 8-fold more total cholesterol and
35-fold more esterified cholesterol than found in normal kidney.
Cholesteryl ester appeared to be formed intracellularly since it was not
membrane-bound and since oleate was the predominant form, as opposed to
linoleate in lipoprotein cholesteryl esters. The cholesterol in clear cell
tumors did not appear to be a result of excessive synthesis from acetate
since HMG-CoA reductase (EC 1.1.1.34) activity was lower in cancer tissue
than in normal kidney (2.9 +/- 0.8 vs. 7.2 +/- 1.2 pmol/mg of protein per
min). In contrast, intracellular activity of fatty acyl-coenzyme
A:cholesterol acyl transferase (ACAT, EC 2.3.1.26) was higher in tumor
tissue than in normal kidney (2405 +/- 546 vs. 1326 +/- 301 pmol/mg of
protein per 20 min) while cytosolic cholesteryl ester hydrolase activity
appeared normal. Cholesteryl ester storage in clear cell renal cancer may
be a result of a primary abnormality in ACAT activity or it may be a result
of reduced release of free cholesterol (relative to cell content) with a
secondary elevation in ACAT activity.