Expression of alpha(2) macroglobulin receptor low density lipoprotein receptor-related protein is cell culture density-dependent in human breast cancer cell line BT-20

alpha(2)Macroglobulin receptor/low density lipoprotein receptor-related protein (alpha(2)MR/LRP) is a multifunctional cell plasma membrane receptor that binds and facilitates the endocytosis of a number of ligands involved in protease regulation and lipoprotein metabolism. In the invasive breast cancer cell line BT-20 we show that the expression of alpha(2)MR/LRP can be strongly affected by cell culture density. By comparing measurements of mRNA total cellular alpha(2)MR/LRP antigen, and cell surface alpha(2)MR/LRP expression Fee have demonstrated a marked cell density-dependent regulation of this receptor expression. Increasing the cell density results in a 3.4-fold increase in cell surface alpha(2)MR/LRP expression. This corresponds to a marked increase in alpha MR/LRP mRNA in Northern blots of total RNA from cells cultured at high density and to consistent increases in alpha(2)MR/LRP heavy chain in Western blots of cell lysates from high density cultures. These studies together demonstrate the significant up-regulation of alpha(2)MR/LRP expression in BT-20 by increased cell density. (C) 1997 Academic Press.