The effect of tamoxifen on the growth of human malignant melanoma in vitro.

The effect of tamoxifen on the growth of malignant melanoma was investigated using human cell lines and single-cell suspensions prepared from patients' tumours cultured in soft agar. Tamoxifen stimulated both [3H]-thymidine incorporation and cell numbers in all of the cell lines tested. Cytoplasmic oestrogen receptor (ER) was detected in one of the responding lines and progesterone receptor (PR) in another. Tumour colony formation in soft agar culture was satisfactorily established from tumour cell suspensions from 13 of 21 patients, only one of which had detectable cytoplasmic ER. Greater than 50% reduction in colony formation with 5 X 10(-7) M tamoxifen occurred in two tumours, neither of which contained ER. These results indicate that tamoxifen has the potential to either retard or accelerate the growth of human malignant melanoma.