In vitro effects of asPR on primary cultures of progestin-independent tumors. Effect of (a) antiprogestins (RU 486, ZK 299) or (b) oligodeoxynucleotides to PR (asPR or scPR) on [3H]thymidine uptake index on primary cultures of responsive progestin-independent tumor cells. The cells were incubated in Dulbecco's modifeid Eagle medium-F12 without phenol red, in the presence of 2.5% ssFCS and different drug concentrations for 48 hours. [3H]thymidine was added in the last 18 hours. These are representative experiments from at least three using three different tumors, with each value corresponding to the mean ± SD cpm of octuplicates. [3H]thymidine uptake index was calculated as the experimental cpm/control cpm. *P < 0.05, **P < 0.01, ***P < 0.001. (c) PR binding was evaluated in vitro using the whole cell binding assay in primary cultures from a responsive progestin-independent tumor in the presence of 2.5% ssFCS (control), scPR (5 μg/ml) or asPR (5 μg/ml; **P < 0.01, *P < 0.05). (d) PR Western blot analysis of cell extracts from the primary cultures grown in the presence of 2.5% ssFCS (-) or asPR (5 μg/ml). Primary antibody: Ab-7 (mouse monoclonal; Neomarkers). NMuMG cell line and uterus were used as negative and positive controls, respectively. Experimental details are explained in Materials and method. asPR, antisense oligodeoxynucleotides to progesterone receptors; PR, progesterone receptor; scPR, scrambled oligodeoxynucleotides to progesterone receptors; SD, standard deviation; ssFCS, steroid stripped fetal calf serum.