MEK5 expression decreases ER signaling and confers endocrine resistance.

<p>(A) MCF-7-vector and MCF-7-MEK5 cells were harvested for total RNA isolation and expression of ER-α mRNA determined using qRT-PCR. Data is represented as mean fold stimulated gene expression normalized to β-actin and vector cells designated as 1. Error bars represent SEM, n = 3. (B) ERE luciferase for MCF-7-vector and –MEK5 cells transiently transfected with pGL2-ERE2X-TK-luciferase plasmid and treated with E2 or vehicle for. Results represent normalized luminescence. Normalization was to vector treated with vehicle and designated as 100 (C) qRT-PCR for MCF-7-vector and –Mek5 cells was performed for E2 responsive genes PgR, SDF-1, c-MYC and Cathepsin-D following E2 treatment. Data is represented as mean fold stimulated gene expression normalized to vehicle treated MCF-7-vcetor cells designnated as 1. Error bars represent SEM, n = 3 independent experiments. (D) MTT ana;ysis of MCF-7-vector and –Mek5 cells following treatment with indicated concentrations of vehicle, ICI or Tam for 24 hours. Data are presented as mean percentage of vehicle treated samples with vehicle normalized to 100. Error bars represent S.E.M., n = 4 independent experiment. (E) Colony assay for MCF-7-vector and –Mek5 cells following treatment with DMSO (vehicle), ICI or Tam. Cells were allowed to grow for 10 days. Colonies of >50 were counted as positive. Results were normalized to percent clonogenic survival of vehicle control cells. Data represented as mean ± S.E.M., n = 4 independent experiments. *, P<0.05; **, P<0.01; ***, P<0.001.