Heterogeneity of prostaglandin E2 binding in murine mammary tumor cells differing in metastatic potential

The metastatic murine mammary tumor cell line 410.4 and its nonmetastatic counterpart tumor line 410 were examined for the presence of prostaglandin E2 (PGE2) binding using a 3H-PGE2 ligand binding assay. Inhibition of endogenous prostaglandin synthesis with indomethacin was shown to increase markedly binding of 3H-PGE2. Equilibrium binding data for tumor 410.4 show that specific binding is saturable, reversible by unlabeled PGE2, temperature-dependent and specific. PGE1, PGE2 or 16-16-dimethyl PGE2 compete well with 3H-PGE2 for binding. PGD2 partially inhibits 3H-PGE2 binding, whereas PGA2 does not compete. Scatchard analysis of equilibrium binding data reveals a high affinity (Kd = 3.9 X 10(-9) M) and an average of 33,785 binding sites/cell. In contrast, binding of 3H-PGE2 to nonmetastatic line 410 has a slightly lower affinity (Kd = 8.8 X 10(-9) M) and an average of 368,857 binding sites/cell. 3H-PGE binding to line 410 cells is comparatively nonspecific as PGD2 is nearly as effective as PGE1, PGE2 and an analogue of PGE2 in competing with 3H-PGE2 and PGA2 also inhibits 3H-PGE2 binding.