Low density lipoprotein receptor activity in human intracranial tumors and its relation to the cholesterol...

The receptor binding of low density lipoprotein (LDL) was determined in homogenates of surgically removed specimens from primary and metastatic intracranial tumors and in some cases also from surrounding brain. Seventy-one specimens from 63 patients were analyzed. In a subsample of 16 specimens from 13 patients, the activity of 3-hydroxy-3-methylglutaryl-CoA reductase was assayed in parallel. The LDL binding in the tumors varied over a wide range. A significantly higher LDL binding activity was found when all tumor samples were compared to brain (P less than 0.05). In the three patients where LDL receptor and 3-hydroxy-3-methylglutaryl-CoA reductase activities were assayed in both tumor tissue and surrounding brain, it was found that the receptor or the enzyme activity was increased in the tumors. It is suggested that certain intracranial tumors have an increased cholesterol requirement and that this may be fulfilled by an enhanced LDL receptor activity or an increased 3-hydroxy-3-methylglutaryl-CoA reductase activity. The data indicate that the LDL receptor activity may be regulated independently of the reductase in intracranial tumors.