Benign prostatic hyperplasia (BPH) is an age-related debilitating prostatic disease that is frequently associated with prostatic inflammation and bothersome lower urinary tract symptoms (LUTS). Animal models have shown that formalin- and bacterial-induced prostatic inflammation can induce bladder dysfunction; however, the underlying mechanisms contributing to prostatic inflammation in BPH and bladder dysfunction are not clear. We previously reported that E-cadherin expression in BPH is downregulated in hyperplastic nodules compared with expression in adjacent normal tissues. Here, we explored the potential consequences of prostatic E-cadherin downregulation on the prostate and bladder in vivo using an inducible murine model of prostate luminal epithelial-specific deletion of Cdh1. The prostate-specific antigen (PSA)-CreERT2 transgenic mouse strain expressing tamoxifen-inducible CreERT2 recombinase driven by a 6-kb human PSA promoter/enhancer was crossed with the B6.129-Cdh1tm2Kem/J mouse to generate bigenic PSA-CreERT2/Cdh1-/- mice. Deletion of E-cadherin was induced by transient administration of tamoxifen when mice reached sexual maturity (7 weeks of age). At 21 to 23 weeks of age, the prostate, bladder, and prostatic urethra were examined histologically, and bladder function was assessed using void spot assays and cystometry. Mice with Cdh1 deletion had increased prostatic inflammation, prostatic epithelial hyperplasia, and stromal changes at 21 to 23 weeks of age, as well as changes in bladder voiding function compared with age-matched controls. Thus, loss of E-cadherin in the murine prostate could result in prostatic defects that are characteristic of BPH and LUTS, suggesting that E-cadherin downregulation could be a driving force in human BPH development and progression.

The androgen receptor (AR) plays a critical role in the development of castration-resistant prostate cancer (CRPC) as well as in the resistance to the second-generation AR antagonist enzalutamide and the selective inhibitor of cytochrome P450 17A1 (CYP17A1) abiraterone. Novel agents targeting AR may inhibit the growth of prostate cancer cells resistant to enzalutamide and/or abiraterone. Through a high-throughput/high-content screening of a 220,000-member small molecule library, we have previously identified 2-[(isoxazol-4-ylmethyl)thio]-1-(4-phenylpiperazin-1-yl)ethanone (IMTPPE) (SID 3712502) as a novel small molecule capable of inhibiting AR transcriptional activity and protein level in C4-2 prostate cancer cells. In this study, we show that IMTPPE inhibits AR-target gene expression using real-time polymerase chain reaction, Western blot, and luciferase assays. IMTPPE inhibited proliferation of AR-positive, but not AR-negative, prostate cancer cells in culture. IMTPPE inhibited the transcriptional activity of a mutant AR lacking the ligand-binding domain (LBD), indicating that IMTPPE inhibition of AR is independent of the LBD. Furthermore, animal studies showed that IMTPPE inhibited the growth of 22Rv1 xenograft tumor, a model for enzalutamide-resistant prostate cancer. These findings suggest that IMTPPE is a potential lead compound for developing clinical candidates for the treatment of CRPC, including those resistant to enzalutamide.

Mutations in the p53 tumor suppressor are frequent in patients with castration-resistant prostate cancer but less so in patients with localized disease, and patients who have Li-Fraumeni with germline p53 mutations do not have an increased incidence of prostate cancer, suggesting that additional molecular and/or genetic changes are required for p53 to promote prostate carcinogenesis. ELL-associated factor 2 (EAF2) is a tumor suppressor that is frequently downregulated in advanced prostate cancer. Previous studies have suggested that p53 binds to EAF2, providing a potential mechanism for their functional interactions. In this study, we tested whether p53 and EAF2 could functionally interact in prostate cancer cells and whether concurrent inactivation of p53 and EAF2 could promote prostate carcinogenesis in a murine knockout model. Endogenous p53 coprecipitated with EAF2 in prostate cancer cells, and deletion mutagenesis indicated that this interaction was mediated through the C terminus of EAF2 and the DNA binding domain of p53. Concurrent knockdown of p53 and EAF2 induced an increase in proliferation and migration in cultured prostate cancer cells, and conventional p53 and EAF2 knockout mice developed prostate cancer. In human prostate cancer specimens, concurrent p53 nuclear staining and EAF2 downregulation was associated with high Gleason score. These findings suggest that EAF2 and p53 functionally interact in prostate tumor suppression and that simultaneous inactivation of EAF2 and p53 can drive prostate carcinogenesis.