CP and glioma: In marked contrast (and unexpectedly), when using membranes prepared from all cancer cell lines examined (C6-glioma, PC-12, HeLa, PC-3, and DU-145), neither the non-selective CBR ligand CP-55,940 nor WIN-55,212-2 produced significant displacement of [3H]CP-55,940 (Figure 1A; right 5 panels).