We studied the effects of 17beta-estradiol, progesterone, and dihydrotestosterone on in vitro growth of human metastatic melanoma. Each sex hormone inhibited the growth of melanoma receptor-dependently; 17beta-estradiol inhibited 3H-thymidine uptake of estrogen receptor-positive WM266-4 and NM26, but not that of the receptor-negative HS15. Progesterone inhibited 3H-thymidine uptake of progesterone receptor-positive WM266-4 and HS15, but not that of the receptor-negative NM26. Dihydrotestosterone inhibited 3H-thymidine uptake of androgen receptor-positive HS15 and NM26, but not that of the receptor-negative WM266-4. The growth inhibition by each hormone was counteracted by the respective hormone receptor antagonist. The combination of more than two hormones neither gave additive nor synergistic growth inhibition. The growth inhibition by each sex hormone was counteracted by interleukin-8 but not by the other growth factors. Each sex hormone reduced the constitutive interleukin-8 secretion and mRNA levels in the respective receptor-positive melanoma but not in the receptor-negative melanoma. Transient transfection showed that each sex hormone inhibited the constitutive chloramphenicol acetyltransferase expression driven by interleukin-8 promoter in the respective receptor-positive melanoma but not in the receptor-negative melanoma. Transfection with a series of 5'-deleted interleukin-8 promoter/chloramphenicol acetyltransferase reporter constructs demonstrated that the sequences between -98 and -63 bp on interleukin-8 promoter may be involved in the transcriptional repression. These data suggest that 17beta-estradiol, progesterone, and dihydrotestosterone suppress the growth of melanoma by inhibiting interleukin-8 production in a receptor-dependent manner.