Azolato-Bridged Dinuclear Platinum(II) Complexes Exhibit Androgen Receptor-Mediated Anti-Prostate Cancer Activity

Prostate cancer is an androgen-dependent malignancy that presents a marked treatment challenge, particularly after progression to the castration-resistant stage. Traditional treatments such as androgen deprivation therapy often lead to resistance, necessitating novel therapeutic approaches. Previous studies have indicated that some of the azolato-bridged dinuclear platinum(II) complexes (general formula: [{cis-Pt(NH₃)₂}₂(μ-OH)(μ-azolato)]X₂, where azolato = pyrazolato, 1,2,3-triazolato, or tetrazolato and X = nitrate or perchlorate) inhibit androgen receptor (AR) signaling. Therefore, here we investigated the potential of 14 such complexes as agents for the treatment of prostate cancer by examining their antiproliferative activity in the human prostate adenocarcinoma cell line LNCaP. Several of the complexes, particularly 5-H-Y ([{cis-Pt(NH₃)₂}₂(μ-OH)(μ-tetrazolato-N2,N3)](ClO₄)₂), effectively inhibited LNCaP cell growth, even at low concentrations, by direct modulation of AR signaling, and by binding to DNA and inducing apoptosis, which is a common mechanism of action of Pt-based drugs such as cisplatin (cis-diamminedichloridoplatinum(II)). Comparative analysis with cisplatin revealed superior inhibitory effects of these complexes. Further investigation revealed that 5-H-Y suppressed mRNA expression of genes downstream from AR and induced apoptosis, particularly in cells overexpressing AR, highlighting its potential as an AR antagonist. Thus, we provide here insights into the mechanisms underlying the antiproliferative effects of azolato-bridged complexes in prostate cancer.