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Background: Prostate-specific membrane antigen (PSMA)-based imaging and therapy are increasingly used in the management of prostate cancer. However, low PSMA surface expression in certain patients is a limitation for PSMA-based technologies. We have previously shown that high doses of dutasteride, a 5α-reductase inhibitor generally used for the treatment of benign prostatic enlargement, increase the PSMA expression in vitro. We now further analyzed the concentration- and time-dependent effects of dutasteride in LNCaP cells., Methods: Androgen receptor (AR) expressing prostate cancer cells (LNCaP) were treated for 7 to 14 days with vehicle control (0.1% dimethyl sulfoxide) or different concentrations of dutasteride (0.25 , 0.5 , 1 , and 5  μM). In addition to cell proliferation, PSMA surface expression was assessed using flow cytometry (FACS) and immunocytochemistry. Total PSMA and AR expression was analyzed by capillary western immunoassay (WES). In addition, tumor cell uptake and internalization assays of 177 Lu-PSMA-617 were performed., Results: Dutasteride treatment resulted in a significant upregulation of PSMA surface expression compared to vehicle control after 7 days in all tested concentrations. After 14 days a further, concentration-dependent increase of PSMA surface expression was detectable. Total PSMA protein expression significantly increased after treatment of cells with high concentrations of dutasteride using 5  μM for 7 or 14 days. However, when lower concentrations were used total PSMA expression was not significantly altered compared to vehicle control. Further testing revealed a dose-dependent increase in uptake and internalization of 177Lu -PSMA-617 after 7 and 14 days. Though, a significantly increased uptake was only observed using a 5  μM dutasteride concentration for 7 days as well as 1  and 5  μM for 14 days., Conclusion: Our investigations revealed a concentration- and time-dependent effect of dutasteride on PSMA expression and uptake of 177Lu -PSMA-617 in LNCaP cells. A short-term treatment of patients with high doses of dutasteride might increase the detection rate of PSMA-based imaging and increase the effect of 177Lu -PSMA-617 therapy via upregulation of PSMA expression., (© 2019 Wiley Periodicals, Inc.)

Introduction and Objectives: Multiple androgen receptor (AR)-dependent and -independent resistance mechanisms limit the efficacy of current castration-resistant prostate cancer (CRPC) treatment. Novel N-terminal domain (NTD) binding AR-targeting compounds, including EPI-001 (EPI), have the promising ability to block constitutively active splice variants, which represent a major resistance mechanism in CRPC. Autophagy is a conserved lysosomal degradation pathway that acts as survival mechanism in cells exposed to anticancer treatments. We hypothesized, that promising NTD-AR treatment may upregulate autophagy and that a combination of NTD-AR and autophagy inhibition might therefore increase antitumor effects., Methods: AR-expressing prostate cancer cell lines (LNCaP, LNCaP-EnzR) were treated with different concentrations of EPI (10, 25, 50 μM) and in combination with the autophagy inhibitors chloroquine (CHQ, 20 μM) or 3-methyladenine (3-MA, 5 mM). Cell proliferation was assessed by WST-1-assays after 1 and 7 days. Ethidium bromide and Annexin V were used to measure viability and apoptosis on day 7 after treatment. Autophagosome formation was detected by AUTOdot staining. In addition, autophagic activity was monitored by immunocytochemistry and Western blot (WES) for the expression of ATG5, Beclin1, LC3-I/II and p62., Results: Treatment with EPI resulted in a dose-dependent reduction of cell growth and increased apoptosis in both cancer cell lines on day 7. In addition, EPI treatment demonstrated an upregulated autophagosome formation in LNCaP and LNCaP-EnzR cells. Assessment of autophagic activity by immunocytochemistry and WES revealed an increase of ATG5 and LC3-II expression and a decreased p62 expression in all EPI-treated cells. A combined treatment of EPI with autophagy inhibitors led to a further significant reduction of cell viability in both cell lines., Conclusions: Our results demonstrate that NTD targeting AR inhibition using EPI leads to an increased autophagic activity in LNCaP and LNCaP-EnzR prostate cancer cells. A combination of NTD AR blockage with simultaneous autophagy inhibition increases the antitumor effect of EPI in prostate cancer cells. Double treatment may offer a promising strategy to overcome resistance mechanisms in advanced prostate cancer., (© 2018 Wiley Periodicals, Inc.)

Background: Prostate-specific membrane antigen (PSMA)-based imaging and therapy are increasingly used for prostate cancer management. However, limitations are a low PSMA expression in certain patients. Androgen receptor axis inhibition can induce PSMA expression in vitro. We hypothesized that different approved compounds upregulate PSMA expression and tested their effect in vitro., Methods: Androgen receptor (AR) expressing prostate cancer (LNCaP) and epithelial prostate cells (PNT1A) were treated for 7 days with enzalutamide, dutasteride, rapamycin, metformin, lovastatin, and acetylsalicylic acid (ASA). PSMA and AR protein expression was assessed using flow cytometry, immunocytochemistry and immunoblotting. Furthermore, uptake and internalization of 177 Lu-PSMA-617 was performed., Results: Enzalutamide and dutasteride led to a significant (both P < 0.05) upregulation of PSMA surface levels in LNCaP cells. In addition, treatment with rapamycin showed a non-significant trend toward PSMA upregulation. No changes were detected after treatment with vehicle, metformin, lovastatin, and ASA. Total PSMA protein expression was significantly enhanced after treatment with enzalutamide and rapamycin (both P < 0.05), whereas dutasteride led to a non-significant upregulation. Uptake of 177 Lu-PSMA-617 was significantly increased after treatment of LNCaP with enzalutamide, dutasteride, and rapamycin (P < 0.05). In addition, internalization was significantly increased by enzalutamide and rapamycin (P < 0.05), and non-significantly increased by dutasteride., Conclusion: In conclusion, our data provide new insights into the effect of different approved pharmacological compounds that can markedly upregulate PSMA expression and radioligand uptake in vitro. Pharmacologically induced PSMA expression may prove useful to improve prostate cancer detection and to enhance anticancer effects in PSMA-based therapy., (© 2018 Wiley Periodicals, Inc.)