Effects of orchiectomy, alone or in combination with testosterone, and cyproterone acetate on exocrine pancreatic carcinogenesis in rats and hamsters

AR-Signaling in Human Malignancies: Prostate Cancer and Beyond

In the 1940s Charles Huggins reported remarkable palliative benefits following surgical castration in men with advanced prostate cancer, and since then the androgen receptor (AR) has remained the main therapeutic target in this disease. Over the past couple of decades, our understanding of AR-signaling biology has dramatically improved, and it has become apparent that the AR can modulate a number of other well-described oncogenic signaling pathways. Not surprisingly, mounting preclinical and epidemiologic data now supports a role for AR-signaling in promoting the growth and progression of several cancers other than prostate, and early phase clinical trials have documented preliminary signs of efficacy when AR-signaling inhibitors are used in several of these malignancies. In this article, we provide an overview of the evidence supporting the use of AR-directed therapies in prostate as well as other cancers, with an emphasis on the rationale for targeting AR-signaling across tumor types.

Androgen receptor blockade in experimental combination therapy of pancreatic cancer

BACKGROUND

Reports on hormone receptor expression of pancreatic cancer (PaCa) cells and treatment responses to antihormonal therapy are still conflicting.

METHODS

Eight human PaCa cell lines were tested for androgen receptor (AR) protein levels by Western blot analysis. Cell proliferation in vitro was measured by sulforhodamine B analysis. AR agonists and inhibitors included dihydrotestosterone (DHT), testosterone (T), and flutamide (Flu). In vivo therapy of nude mouse xenografts tested Flu with gemcitabine (Gem) and/or bevacizumab (Bev).

RESULTS

Seven of eight human PaCa cell lines expressed detectable AR protein. Median relative expression compared with the AR positive control LnCaP was 21% (range: 16 to 63). Growth stimulation by DHT or T was minor (<20%); inhibition by Flu varied greatly and did not correlate to AR levels. Even in the sensitive cell line Panc1, Flu failed to increase Gem toxicity in vitro. However, in vivo Flu therapy resulted in significant growth inhibition of Panc-1 tumors. Flu/Gem treatment did not enhance the effect; Bev/Flu/Gem triple therapy had the greatest effect (P = 0.06 compared to Flu/Gem). Flu alone did not affect apoptotic activity, but decreased the tumor cell proliferative index (P = 0.04); in combination with Gem, Flu reduced the tumor cell density (P = 0.02).

CONCLUSIONS

The majority of PaCa cell lines express AR at various levels, but most fail to show an in vitro antiproliferative response to AR inhibition. The strong antitumor effect of flutamide in vivo is not significantly enhanced in combination with gemcitabine or bevacizumab, suggesting primarily monotherapy benefit potential of AR blockade in susceptible PaCa.

Lack of influence of diethylstilbestrol on induced pancreatic ductal carcinomas in Syrian hamsters

Syrian golden hamsters were treated with N-nitrosobis-(2-oxopropyl)amine (BOP) and/or diethylstilbestrol (DES) for lifetime. After BOP treatment the hamsters developed high incidences of pancreatic neoplasms, but DES failed to show any effect on these or other tumours.