Expression of α2-macroglobulin receptor/low density lipoprotein receptor-related protein on surfaces of tumour ceils: a study using flow cytometry

α2-Macroglobulin receptor/low density lipoprotein receptor-related protein (α2 MR/LRP) is a multifunctional cell surface receptor that binds and endocytoses several structurally and functionally distinct ligands. Very little is known about the expression and function of α2 MR/LRP in tumour cells. The aim of this study was to quantify the number of α2 MR/LRP on surfaces of human tumour cells by flow cytometry. Using human α2 MR/LRP monoclonal antibody 8G1, human peripheral blood lymphocytes (negative control cells), monocytes (positive control cells), human neonatal foreskin fibroblast cells (NFF) (positive control cells), three human breast cancer cell lines (BT-20, T-47D, and MCF-7), two human ovarian tumour cell lines (JAM, and CI80-13S), and five human melanomas (MM418c1, MM253c1, A2058, MM138, MM370) were indirectly labelled with goat anti-mouse IgFITC. The fluorescent signals of stained cells were measured by flow cytometry. Using Quantum Simply Cellular bead standards, the number of α2 MR/LRP binding sites per cell was assessed. The flow cytometric method to quantify of α2 MR/LRP described here is simple and reliable. All the human tumour cell lines so far examined express α2 MR/LRP at different levels from ~300 to ~10000 sites per cell.