Evaluation of [C-11]SA5845 and [C-11]SA4503 for imaging of sigma receptors in tumors by animal PET

Sigma receptors are expressed in a wide variety of tumor cell lines, and are expressed in proliferating cells. A radioligand for the visualization of sigma receptors could be useful for selective detection of primary tumors and their metastases, and for non-invasive assessment of tumor proliferative status. To this end we evaluated two sigma receptor ligands, [C-11]SA5845 and [C-11]SA4503. in an in vitro study, AH109A hepatoma showed moderate densities of sigma] and sigma(2) receptors, and VX-2 carcinoma showed a high density of sigma(2) receptors: B-max (fmol/mg protein) for sigma(1) vs. sigma(2), 1,700 vs. 1,200 for AH109A hepatoma and 800 vs. 10,000 for VX-2 carcinoma. In a cell growth assay in vitro, neither SA5845 nor SA4503 (