Difference in uptake of 3H-estramustine in two human prostatic carcinoma cell lines, LNCaP and LNCaP-r

Estramustine, estradiol-3-N-bis(2-chloroethyl)carbamate (EM), has been shown to inhibit growth of the human prostatic carcinoma cell line LNCaP as well as its subline LNCaP-r. The hormone sensitive LNCaP showed greater sensitivity to the drug than the hormoneresistant LNCaP-r. LNCaP has also shown an increasing sensitivity to 10(-7) M EM, when incubated with different concentrations of steroid hormones. We studied whether the increasing sensitivity was caused by increased uptake of EM. 3H-estramustine was added to medium and the cells were incubated 15 min, 30 min, 45 min, 1 h, 1.5 h, 2 h, and 4 h, or 2 h, 4 h, 6 h, and 8 h. No effect of steroids on the uptake of EM was noted, but LNCaP showed a higher uptake of EM compared to LNCaP-r. The uptake of EM in LNCaP increased for eight hours, whereas LNCaP-r reached its maximum uptake after six hours of incubation.