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PSMA expression gradually increases from benign prostatic hyperplasia to adenocarcinoma of the prostate and is therefore used for the development of improved diagnostic (PSMA)-based prostate cancer imaging tools. Pharmacological induction of PSMA is therefore eminent to further improve the detection rate of PSMA-based imaging. Our previous studies have demonstrated that lovastatin (Lova) and dutasteride (Duta) are able to induce PSMA expression. However, the mechanisms by which PSMA is regulated in prostate cancer remain poorly understood. Androgen receptor (AR) and homeobox B13 (HOXB13) are the best known regulators of PSMA, hence in the present study we aimed to explore the PSMA regulation by HOXB13 and AR signaling in LNCaP and VCaP cells following treatments with Lova and Duta. Furthermore, our previous research revealed a growth arrest in prostate cancer cells after Lova, but not after Duta treatment. To understand this discrepancy, we explored the influence of Lova and Duta on well known tumor growth promoters, such as AR, the mTOR/Akt signaling pathways and Cyclin D1. Our results showed that treatment with Lova leads to a significant inhibition of the investigated tumor promoters and results in growth regression of LNCaP and VCaP cells. In contrast, Duta does not show these effects. Furthermore, we confirm the cooperative effect of HOXB13 and AR in regulating PSMA in LNCaP cells, and extend the investigations to an additional prostate cancer cell line (VCaP)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Background: ARN-509 (Apalutamide) is a unique androgen receptor (AR) antagonist for the treatment of castration-resistant (CR) prostate cancer (PC). It inhibits AR nuclear translocation, DNA binding and transcription of AR gene targets. As dysregulation of autophagy has been detected in PC, the targeting of autophagy is a potential approach to overcome early therapeutic resistance. Therefore, we investigated the characteristics of autophagic response to ARN-509 treatment and evaluated the potential effect of a combination with autophagy inhibition., Methods: Human prostate cancer cells (LNCaP) were cultivated in a steroid-free medium. Cells were treated with ARN-509 (50 µM) alone or in combination with the autophagy inhibitors 3-methyladenine (3MA, 5 mM) or chloroquine (Chl, 20 µM) or with ATG5 siRNA knock-down. Cell viability and apoptosis were measured by flow cytometry and fluorescence microscopy. Autophagy was monitored by immunohistochemistry, AUTOdot and immunoblotting (WES)., Results: Treatment with ARN-509 led to cell death of up to 37% with 50 µM and 60% with 100 µM by day 7. The combination of 50 µM ARN-509 with autophagy inhibitors produced a further increase in cell death by day 7. Immunostaining results showed that ARN-509 induced autophagy in LNCaP cells as evidenced by elevated levels of ATG5, Beclin 1 and LC3 punctuation and by an increase in the LC3-II band detected by WES. Autophagic flux was restored by the treatment of cells with Chl, intensifying the LC3-II band. These findings were further supported by an enhanced autophagosome punctuation observed by Autodot staining., Conclusions: These data demonstrate that treatment with ARN-509 leads to increased autophagy levels in LNCaP cells. Furthermore, in combination with autophagy inhibitors, ARN-509 provided a significantly elevated antitumor effect, thus providing a new therapeutic approach potentially translatable to patients., (Copyright © 2020 Elsevier Inc. All rights reserved.)