Dexamethasone, Prostaglandin A, and Retinoic Acid Modulation of Murine and Human Melanoma Cells

ABSTRACT-The cloning efficiencies of a murine melanoma cell line (S91 CCl 53.1) and a human melanoma cell strain (C8146c) were inhibited by dexamethasone (DEX), prostaglandin A1 (PGA1) , and {3-aIl-trans-retinoic acid (RA) in a dose-dependent manner. Murine melanoma tumor colony-forming units (MTCFU) were inhibited more than 99 % by DEX (1xt 0- 7 M) and RA (1xt 0- 7 M) with a concentration needed to produce a 50 % reduction in colony formation for both hormones of 5X10-9 M. Combinations of DEX and RA effected a synergistic inhibition on colony formation, which was reflected by a 1V2 log reduction in the hormone concentration needed to produce a greater than 99 % inhibition of colony formation. When PGA1 was added to DEX and RA, a greater than additive reduction in colony formation was observed. Human MTCFU from cell strain C8146c were inhibited more than 85 % at an RA concentration of 1xt 0- 7 M, but they were reduced only to 40 % of control at a DEX concentration of 1x10-6 M. DEX-RA produced an additiv