The effect of estramustine phosphate (Estracyt) on the growth of murine aplastic mammary carcinoma, Ehrlich carcinoma, melanoma B-16, and five cell lines: L929 (mouse fibroblasts), BHK (baby hamster kidney), HeLa (human cervical carcinoma), HEp-2 (human laryngeal carcinoma), and K562 (human granulocytic leukemia) was investigated. In vivo, estramustine phosphate inhibits the growth of aplastic mammary carcinoma and Ehrlich carcinoma, but has no effect on melanoma B-16. In cultured aplastic mammary carcinoma, estramustine phosphate decreased the incorporation of 3H-thymidine into DNA. This drug inhibits the population growth of L929, BHK, HEp-2, and K562 cultures, but stimulates the growth of HeLa cells. We conclude that estramustine phosphate retards the growth of various cells, and that studies of other potential fields of application of the drug (aside from prostatic carcinoma) is justified.

Incubation with estramustine phosphate for 24 h inhibited DNA, RNA and protein synthesis in primary cultures of human kidney, mammary, prostatic, cervical and endometrial carcinoma. Not only the presence, but also the concentration of oestrogen receptors correlated with estramustine phosphate effects on tumour cell proliferation.