RECEPTORS AS POTENTIAL BIOMARKERS OF PROLIFERATION IN BREAST-CANCER

sigma(1) and sigma(2) receptors have been shown to exist in a number o f rodent and human tumor cell lines, Although their expression is hete rogeneous and their function is unknown, sigma receptors have been pro posed as potential targets far diagnostic tumor-imaging agents. In thi s study, the density of sigma(2) receptors in proliferative (P) and qu iescent (Q) cells of the mouse mammary adenocarcinoma, line 66, was ex amined. Scatchard analyses of sigma(2) receptors mere performed on mem brane preparations of 66 P cells from 3-day cultures and 66 Q cells fr om 7-, 10-, and 12-day cultures. The Scatchard studies revealed that 6 6 P cells had similar to 10 times more sigma(2) receptors/cell than th e 66 Q cells from 10-day cultures, Although >97% of the cells were qui escent after 7 days in culture, the maximum differential in the sigma( 2) expression between 66 P and 66 Q cells was not attained until these cells had been in culture for 10 days, These data suggest that ligand s labeled with positron-emitting or single photon emitting radionuclid es, which selectively bind sigma(2) receptors, have the potential to n oninavasively assess the proliferative status of human breast tumors.