Androgen receptor cytosine-adenine-guanine repeat polymorphisms modulate EGFR signaling in epithelial ovarian carcinomas

Length of a polymorphic cytosine-adenine-guanine (CAG) repeat in the androgen receptor (AR) may inversely correlate with AR activity. We have identified an association between short AR allelotypes and decreased survival in women with epithelial ovarian cancer. We hypothesize short AR allelotypes promote aggressive ovarian cancer phenotype through modulation of epidermal growth factor receptor (EGFR) signaling.

SKOV-3 cells were transfected with AR plasmids containing variable CAG repeat lengths, and AR activity was assessed through co-transfection with a luciferase plasmid. EGFR signaling was studied with Western blot analysis of EGFR, EGFR-p (phosphorylated), MAPK, and MAPK-p, and cellular proliferation examined by MTT assays. Data were analyzed using analysis of variance, Tukey-Kramer multiple comparison test, and Student's t test.

We confirmed AR allelotype length inversely correlates with AR activity in epithelial ovarian cells; a 2.5% decrease in luciferase-fold activation was seen with each CAG unit increase (p=0.0002). We observed inhibition of EGFR-p abundance with increasing abundance of transfected AR cDNA (89.2% and 39.9% for 3.0 and 6.0 mug, compared to 1.5 microg, p=0.03). After transfection with short (CAG=14), median (CAG=21), and long (CAG=24) AR allelotypes, an inverse correlation was identified between abundance of MAPK-p and CAG repeat length (p=0.002). Decrease in cellular abundance was also seen in cultures transfected with ARs of increasing CAG repeat length (p<0.0001).

These data identify an inhibitory action of AR on EGFR signaling, and support research investigating AR/EGFR antagonism in the treatment of ovarian cancers.