Abstract 5492: Effect of GnRH analogues and pharmacoperone IN3 treatment in survival of prostatic cancer cells to radiation

Abstract

Abstract Prostate cancer (PCa) is the second cause of cancer related death in men. Radiotherapy of localized tumours is highly effective and reduces the risk of urinary incontinence and impotence compared with radical surgery. Radiotherapy is more effective when associated with GnRH analogues (as leuprolide), which has been related with decreased circulating androgens due to hypophysis-testis axis blockade. We propose that GnRH analogues increase the cytotoxic effect of radiotherapy in PCa cells, effect that can be potentiated with IN3, a pharmacoperone that increases GnRH receptor (GnRHR) expression in cell membrane. To demonstrate our hypothesis, we stablished primary cell cultures from PCa samples from patients of our Institutional Hospital (n=12). Cells were treated during 24 hr with 1 ug/ml IN3 (Merck Sharp & Dohme Corp., USA,) and then with different concentrations (20-80 ng/ml) of leuprolide (Sigma-Aldrich Co., USA) for 24 hr. Later, cells were irradiated at 3 Gy and we evaluated cell survival at 24 hr (through MTT), changes in cell cycle at 24 hr and apoptosis at 6 hr (through FACS). GnRHR expression in cell membrane after 24 hr of IN3 treatment was evaluated trough fluorescence microscopy. Results were evaluated using Anova and Kruskal-Wallis tests, followed by post-test of Dunn. P <0.05. As we previously described, we observed that leuprolide decreased PCa cell survival. When cells were pre-treated with IN3, GnRHR expression in cell membrane increased in about 60% and the effect of leuprolide treatment was higher. When cells were irradiated, cell survival decreased in 10%, this effect was higher when cells were previously treated with leuprolide (15%) and IN3/leuprolide (20%). This was related with an increase of 10% in apoptosis and cell cycle arrest in G2. The effect was dependant of leuprolide dose. At the dose used, IN3 had no effect in cell survival. We concluded that leuprolide sensitizes cells from PCa to radiation, and this effect was increased with pretreatment with IN3 due, at least in part, for the increase of GnRHR expression in cell membrane, a receptor that decreases its expression during PCa progression. In clinical practice, leuprolide has direct effect over PCa cells, decreasing cancer cell survival and improving the cytotoxic effect of radiation. The utility of IN3 as a potential adjuvant therapy needs to be addressed. Citation Format: Catherine A. Sanchez, Apolo Salgado, Enrique A. Castellon. Effect of GnRH analogues and pharmacoperone IN3 treatment in survival of prostatic cancer cells to radiation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5492. doi:10.1158/1538-7445.AM2014-5492