TY - JOUR
T1 - Cholesterol metabolism in cancer cells in monolayer culture. VI. Metabolism of high-density lipoprotein
AU - Gal, David
AU - MacDonald, Paul C.
AU - Porter, John C.
AU - Simpson, Evan R.
N1 - Funding Information:
2Postdoctoral Trainee supported, in part, by USPHS Grant l-T32-HD07190. ‘Author to whom all correspondence should be addressed.
Funding Information:
1 Supported, in part, by USPHS Grant 5-POl-AGOO306.
PY - 1982/4/1
Y1 - 1982/4/1
N2 - The metabolism of high-density lipoprotein (HDL) in cells of five human cancer cell lines maintained in monolayer culture was investigated. In cells of some of the lines there was evidence of high-affinity binding sites for HDL, whereas in others this could not be demonstrated. However, in one cell line, viz., HEC-B-296 (human endometrial carcinoma), degradation of the protein component of HDL was demonstrated. The proteolytic activity was specific for HDL in so far as human serum albumin was not degraded by these cells. However, this degradative process did not involve internalization of the HDL molecule and degradation was not mediated by lysosomal proteolytic enzymes. HDL, when present in the medium, did not affect the degradation of low-density lipoprotein and low-density lipoprotein did not affect the degradation of HDL. HDL did not affect significantly cholesterol biosynthesis or cholesteryl ester biosynthesis as estimated from the activity of the regulatory enzymes, 3-hydroxy-3-methylglutaryl coenzyme A reductase and acyl-CoA:cholesterol acyltransferase. The degradation of HDL by HEC-B-296 cells was inhibited, to various degrees, when trypsin inhibitor or a protease inhibitor such as leupeptin, was present in the culture medium. It is concluded that degradation of the protein component of HDL by human neoplastic cells of the HEC-B-296 line was the result of activity of a proteolytic enzyme that is present on the external surface of the cells.
AB - The metabolism of high-density lipoprotein (HDL) in cells of five human cancer cell lines maintained in monolayer culture was investigated. In cells of some of the lines there was evidence of high-affinity binding sites for HDL, whereas in others this could not be demonstrated. However, in one cell line, viz., HEC-B-296 (human endometrial carcinoma), degradation of the protein component of HDL was demonstrated. The proteolytic activity was specific for HDL in so far as human serum albumin was not degraded by these cells. However, this degradative process did not involve internalization of the HDL molecule and degradation was not mediated by lysosomal proteolytic enzymes. HDL, when present in the medium, did not affect the degradation of low-density lipoprotein and low-density lipoprotein did not affect the degradation of HDL. HDL did not affect significantly cholesterol biosynthesis or cholesteryl ester biosynthesis as estimated from the activity of the regulatory enzymes, 3-hydroxy-3-methylglutaryl coenzyme A reductase and acyl-CoA:cholesterol acyltransferase. The degradation of HDL by HEC-B-296 cells was inhibited, to various degrees, when trypsin inhibitor or a protease inhibitor such as leupeptin, was present in the culture medium. It is concluded that degradation of the protein component of HDL by human neoplastic cells of the HEC-B-296 line was the result of activity of a proteolytic enzyme that is present on the external surface of the cells.
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U2 - 10.1016/0003-9861(82)90079-0
DO - 10.1016/0003-9861(82)90079-0
M3 - Article
C2 - 7092218
AN - SCOPUS:0020463684
SN - 0003-9861
VL - 214
SP - 726
EP - 733
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 2
ER -