Epigenetic modulation of PTEN expression during antiandrogenic therapies in human prostate cancer

Although the tumor-suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is frequently mutated or deleted in a wide variety of solid tumors, some malignancies, including prostate cancer, exhibit undetectable PTEN protein without loss of PTEN gene. Aim of this study was to evaluate whether the PTEN downmodulation, observed during bicalutamide treatment, was due to epigentic events. We analyzed the expression of PTEN in presence or absence of azacitidine or valproic acid in a panel of 50 primary cultures derived from naive (UNT, 23 ptz) and bicalutamide-based neoadjuvant hormone therapy-treated patients (NHT, 27 pts). Results showed that Western blot and PCR analyses showed that 54 and 68% of primary cultures displayed detectable amounts of PTEN protein and mRNA, respectively. Treatment with azacitidine increased the percentage of PTEN-positive cultures up to 72 and 80% for PTEN protein and mRNA determination, respectively. Treatment with valproic acid was able to increase the percentage of PTEN-positive cultures up to 80 and 74% for PTEN protein and mRNA determination, respectively. The percentage of cultures with undetectable levels of PTEN protein was significatively higher in cultures derived NHT patients respect to cultures derived from UNT men (P=0.020). Valproic acid reduced significantly the percentage of cultures PTEN-negative only at protein level and only in NHT (P=0.029) group. In conclusion, our data suggests that antiandrogenic therapy reduced PTEN expression by epigenetic mechanisms suggesting that epigenetic drugs, upmodulating PTEN expression, can reduce Akt activity and probably enhance the efficacy of antiandrogenic therapy.