Objectives. Short cytosine-adenine-guanine (CAG) polymorphisms in the androgen receptor (AR) correlate with decreased surgical cytoreducibility and poor survival in women with epithelial ovarian cancers. In prostate cancer cell cultures, AR interacts with the epidermal growth factor (EGF) pathway, which signals through its receptor (EGFR) and the downstream protein MAPK to modulate tumor invasion and metastasis. We hypothesized that length of the CAG repeat polymorphism inversely correlates with AR activity in epithelial ovarian cancer cells, and that androgen modulation of EGFR signaling promotes aggressive ovarian cancer biology. Methods. AR-null SKOV3 epithelial ovarian carcinoma cells were transiently co-transfected with a luciferase reporter plasmid containing AR response elements and one of three AR expression plasmids with short (9), medium (24) and long (45) CAG repeat lengths. We assayed for luciferase after treatment with 2.5 nM dihydrotestosterone (DHT). SKOV3 cells were also stably transfected with ARs with short, medium and long CAG repeats and expression and activation of EGFR and MAPK were examined by Western blot analysis after treatment with 100 ng/ml EGF. Immunoblots were analyzed by densitometry and analysis of variance. Results. In luciferase reporter assays, no luciferase activity was seen in cultures with any AR in the absence of DHT. However, treatment with DHT identified an inverse correlation between AR CAG length and AR activity; cells expressing AR(24) and AR(45) demonstrated 82.1% and 50.3%, respectively, of the activity seen in cells expressing AR(9) (p=0.0002). Western blot analysis did not identify differences in EGFR or MAPK in cell cultures stably transfected with ARs with medium or long CAGs. However, in cells expressing AR(24) and AR(45), 94.4% and 47.6% of the abundance of phosphorylated EGFR was seen compared to those expressing AR(9) (p < 0.01). Concomitant changes in MAPK was also observed whereby cells expressing AR(24) and AR(45) had 15.4% and 7.5% of the phosphorylated MAPK abundance compared to that in cells expressing AR(9) (p < 0.01). Conclusions. Short AR CAG lengths correlate with increased activity of AR, as well as increased activation of EGFR and EGFR downstream proteins in SKOV3 cells. These data suggest combined AR-EGFR antagonism may represent a potential therapeutic target in women with epithelial ovarian cancer. The polarity of this AR/EGFR pathway crosstalk suggests that therapeutics regimens targeting both AR and EGFR may act synergistically to inhibit epithelial ovarian cancer cell growth.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]