RECEPTOR FOR GLUCOCORTICOIDS IN RPMI 3460 MELANOMA-CELLS

Abstract

The role of steroid hormones in the biological behavior of malignant melanoma was studied. The growth of RPMI 3460 Syrian hamster melanoma cells in monolayer culture is retarded by the synthetic glucocorticoid dexamethasone. A macromolecule with properties of a glucocorticoid receptor was identified in cytosols prepared from these cells. Sucrose density gradient analyses on 6 separate cell batches consistently demonstrated substantial levels of saturable [3H]dexamethasone binding [concentration = 195 .+-. 47 (SE) femtomol/mg cytosol protein] in the 7S region of the gradients. Similar analyses failed to detect saturable binding for other classes of steroid hormones. Scatchard plots of [3H]dexamethasone binding to the receptor were linear, indicating a single class of high-affinity sites (Kd = 2.3 .+-. 0.78 .times. 10-9 M for 3 cell batches). Steroid competition experiments confirmed the glucocorticoid specificity of the binding molecule; competitors in descending order of effectiveness were glucocorticoids, mineralocorticoid, progestins, estrogen and androgen. Combined hormone receptor and growth studies with RPMI 3460 cells can help to define the mechanism of glucocorticoid action in malignant melanoma and may ultimately help establish the value of steroid hormones as therapeutic agents for this disease.