Effects of 17β-estradiol (E) and human placental lactogen (HPL) on DNA synthesis in organ culture of benign human breast tumors

The technique of organ culture for studying hormone dependence has been successfully used in experimental mammary tumors and human breast tumors. These tumors respond to certain hormonal stimuli such as some steroid and polypeptide hormones which enhance DNA synthesis. Various methods have been developed for the purpose of defining the hormone dependence of a given tumor by in vitro studies. Organ culture would seem appropriate since it permits assessment of the direct effects of hormones on growth without interfering with the multiple endocrine interactions that prevail within the whole organism. The purpose of the present study was to analyze the effects of estrogen (E) and human placental lactogen (HPL) alone and in combination on DNA synthesis in 5 day organ culture. Biopsy specimens obtained from 18 benign human breast tumors were processed into explants and individually cultured at 37°C (95% O₂, 5% CO₂) in Medium 199 (M199) which contained penicillin G (50 IU/ml), hydrocortisone (1.0 μg/ml) and insulin (5.0 μg/ml). All tissue was grown under the following conditions a) Controls, only M199 b) M199 with E (1.0 μg/ml) c) M199 with HPL (10.0 μg/ml) and d) M199 with E and HPL. Results of such studies indicated that E and/or HPL alone or in combination significantly (P < 0.05) stimulated the (3H)-thymidine incorporation into DNA of benign human breast tumors after 5 days in culture. Thus, the direct capacity of these two hormones to promote DNA synthesis in organ culture was demonstrated in these studies.