Figure 6: Tumor cells derived from RSP-K12V cells had enhanced transcriptional activity of the ER and the capacity for estrogen-independent proliferation.
A) The level of ERα expression was enhanced in RSP-K12V-tumor cells compared with that in RNSP-K12V-tumor cells. GAPDH served as the internal control. Representative data are shown. Similar results were obtained in three independent experiments.
B) The levels and transcriptional activity of the ER in RSP-K12V-tumor cells and RNSP-K12V-tumor cells were analyzed by a luciferase reporter assay. The luciferase activity of RSP-K12V-tumor cells was enhanced by stimulation of E2 (3.8-fold) or serum (8-fold) over the level in RNSP-K12Vtumor cells (p < 0.01).
C) The cell growth rate of RSP-K12V cells and RSP-K12V tumor cells was investigated in the E2 present or E2 deprived condition. Cells were cultured with phenol red free DMEM containing 10% ordinary FBS (E2 present condition) or 10% charcoal treated FBS (E2 deprived condition) for three weeks. Cell growth of RSP cells and RSP-K12V cells was suppressed in the E2 deprived condition compared with that in the E2 present condition. In contrast, growth of RSP-K12V tumor cells was not influenced by estrogen. Data of cell numbers were represented as the means ±SEM from three independent experiments. * p < 0.05