Androgen-Dependent Regulation Of Her-2/Neu In Prostate Cancer Cells.

10099 Background: The mechanisms underlying the progression of prostate cancer to androgen independence remain poorly understood. Overexpression of Her-2/neu (c-ErbB2) activates the androgen receptor pathway and confers a survival and growth advantage to prostate cancer cells in an androgen-deficient milieu. Methods: Androgen-sensitive prostate cancer cell line LNCaP was used as a model system in vitro and in vivo. Experiments in mice were undertaken by injecting cells orthotopically into the ventral lobe of the mice prostate. Results: Here, we report that androgen receptor (AR) and Her-2/neu reciprocally regulate each other in LNCaP human prostate cancer cells. Absence of androgens, AR blockade with Casodex (bicalutamide) or suppression of AR with RNAi induced Her-2/neu protein expression and phosphorylation in vitro and in vivo. Similarly, suppression of Her-2-neu expression resulted in AR upregulation. In contrast, upon re-administration of androgens, Her-2/neu mRNA, protein and phosphorylation levels decreased linearly with increasing concentrations of androgens as LNCaP cells re-entered the cell cycle. Conclusions: Thus, induction and activation of Her-2/neu occurs in an androgen-depleted environment or as a result of AR inactivation, promoting androgen-independent survival of prostate cancer cells. No significant financial relationships to disclose.