Expression of two isozymes of acyl‐coenzyme A: Cholesterol acyltransferase‐1 and ‐2 in clear cell type renal cell carcinoma

Abstract

The present study investigated the expression of acyl-coenzyme A: cholesterol acyltransferase-1 (ACAT-1) and -2 in clear cell type renal cell carcinoma (RCC). Clear cell type RCC and corresponding normal kidney tissue samples were obtained from 19 surgical cases (28-85 years of age). Tissue extracts were assayed for ACAT activity and protein expression by immunoblotting with anti-ACAT-1 and anti-ACAT-2 antibodies. Frozen sections were subjected to Oil red O staining for lipids, and were immunostained with ACAT-specific antibodies. Acyl-coenzyme A cholesterol acyltransferase activity was 5.7-fold higher (P < 0.01) in clear cell carcinoma (23.52 +/- 4.90 pmol/mg protein/min) than in normal kidney (4.12 +/- 0.36). Consistent with this, immunoblotting and immunohistochemical staining revealed strong expression of ACAT-1 in clear cell type RCC. Densitometric analysis showed that ACAT-1 expression was 2.9-fold higher in clear cell type RCC than in normal kidney. In contrast, ACAT-2 expression was negative in clear cell type RCC and normal kidney. Oil red O staining showed massive deposits of lipid in RCC cells. We identified strong expression of ACAT-1 in clear cell type RCC. Upregulation of ACAT-1 leads to high ACAT enzymatic activity, which accelerates the accumulation of cholesterol ester in clear cell type RCC.