GROWTH OF PROSTATIC-CANCER CELLS, DU-145, AS MULTICELLULAR SPHEROIDS AND EFFECTS OF ESTRAMUSTINE

The human prostatic carcinoma cell line DU145 was grown as multicellul ar spheroids in vitro. The volume doubling time during the early expon ential growth-phase was about 5 days. The saturation volume, in the pl ateau phase of the growth curve, was in the order of 1.4 mm3. The sphe roids developed a central degenerative region surrounded by a 0.1-0.3 mm layer of viable cells. The DU 145 spheroid system is planned to be used as a model in studies on chemotherapy and targeted radiotherapy o f micrometastases of prostatic cancer. Some effects of the drug estram ustine, EM, a conjugate of estradiol and nornitrogen mustard, were ana lysed in this introductory study. Tritium-labelled estramustine, H-3-E M, bound both in the viable cell layers and in the degenerative region of the spheroid already after 1 hour of incubation which indicated go od penetration. The viable cells bound only low levels of H-3-EM while the degenerative region bound H-3-EM to a higher extent. The amount o f bound H-3-EM increased after incubation for 24 hours. The binding wa s nonspecific since it could not be inhibited by pretreatment with an excess of non-radioactive EM. Furthermore, H-3-EM bound to a similar e xtent in glioma and colon carcinoma spheroids used for comparison. Inc ubation of DU 145 spheroids for 24 hours with EM (20 mg/ml) induced a growth delay of 6-7 days and a transient increase in the volume of the extracellular spaces for a few days following the treatment. The resu lts showed that the binding of EM to prostate DU 145 cells growing as spheroids was not specific and that the toxic action was limited. An i nteresting result was that EM works as an extracellular space expander . This might be exploited in combination treatments with other agents.