The next-generation antiandrogen drugs such as enzalutamide and abiraterone extend survival times and improve quality of life in patients with advanced prostate cancer. However, resistance to both drugs occurs frequently through mechanisms that are incompletely understood. Wnt signaling, particularly through Wnt5a, plays vital roles in promoting prostate cancer progression and induction of resistance to enzalutamide and abiraterone. Development of novel strategies targeting Wnt5a to overcome resistance is an urgent need. In this study, we demonstrated that Wnt5a/FZD2-mediated noncanonical Wnt pathway is overexpressed in enzalutamide-resistant prostate cancer. In patient databases, both the levels of Wnt5a and FZD2 expression are upregulated upon the development of enzalutamide resistance and correlate with higher Gleason score, biochemical recurrence, and metastatic status, and with shortened disease-free survival duration. Blocking Wnt5a/FZD2 signal transduction not only diminished the activation of noncanonical Wnt signaling pathway, but also suppressed the constitutively activated androgen receptor (AR) and AR variants. Furthermore, we developed a novel bioengineered BERA-Wnt5a siRNA construct and demonstrated that inhibition of Wnt5a expression by the BERA-Wnt5a siRNA significantly suppressed tumor growth and enhanced enzalutamide treatment in vivo. These results indicate that Wnt5a/FZD2 signal pathway plays a critical role in promoting enzalutamide resistance, and targeting this pathway by BERA-Wnt5a siRNA can be developed as a potential therapy to treat advanced prostate cancer.

The development of resistance to current standard-of-care treatments, such as androgen receptor (AR) targeting therapies, remains a major challenge in the management of advanced prostate cancer. There is an urgent need for new therapeutic strategies targeting key resistant drivers, such as AR variants like AR-V7, and steroidogenic enzymes, such as aldo–keto reductase 1C3 (AKR1C3), to overcome drug resistance and improve outcomes for patients with advanced prostate cancer. Here, we have designed, synthesized, and characterized a novel class of LX compounds targeting both the AR/AR variants and AKR1C3 pathways. Molecular docking and in vitro studies demonstrated that LX compounds bind to the AKR1C3 active sites and inhibit AKR1C3 enzymatic activity. LX compounds were also shown to reduce AR/AR-V7 expression and to inhibit their target gene signaling. LX1 inhibited the conversion of androstenedione into testosterone in tumor-based ex vivo enzyme assays. In addition, LX1 inhibited the growth of cells resistant to antiandrogens including enzalutamide (Enza), abiraterone, apalutamide, and darolutamide in vitro. A synergistic effect was observed when LX1 was combined with antiandrogens and taxanes, indicating the potential for this combination in treating resistant prostate cancer. Treatment with LX1 significantly decreased tumor volume, serum PSA levels, as well as reduced intratumoral testosterone levels, without affecting mouse body weight. Furthermore, LX1 was found to overcome resistance to Enza treatment, and its combination with Enza further suppressed tumor growth in both the CWR22Rv1 xenograft and LuCaP35CR patient-derived xenograft models. Collectively, the dual effect of LX1 in reducing AR signaling and intratumoral testosterone, along with its synergy with standard therapies in resistant models, underscores its potential as a valuable treatment option for advanced prostate cancer. Significance: LX1 simultaneously targets androgen receptor variants and the steroidogenic enzyme AKR1C3, offering a promising approach to combat drug resistance and enhancing therapeutic efficacy in conjunction with standard treatments for advanced prostate cancer.

Current common treatments for castration-resistant prostate cancer (CRPC) typically belong to one of three major categories: next-generation anti-androgen therapies (NGAT) including enzalutamide, abiraterone acetate, apalutamide, and darolutamide; taxane therapy represented by docetaxel; and PARP inhibitors (PARPi) like olaparib. Although these treatments have shown efficacy and have improved outcomes for many patients, some do not survive due to the emergence of therapeutic resistance. The clinical landscape is further complicated by limited knowledge about how the sequence of treatments impacts the development of therapeutic cross-resistance in CRPC. We have developed multiple CRPC models of acquired therapeutic resistance cell sublines from C4-2B cells. These include C4-2B MDVR, C4-2B AbiR, C4-2B ApaR, C4-2B DaroR, TaxR, and 2B-olapR, which are resistant to enzalutamide, abiraterone, apalutamide, darolutamide, docetaxel, and olaparib, respectively. These models are instrumental for analyzing gene expression and assessing responses to various treatments. Our findings reveal distinct cross-resistance characteristics among NGAT-resistant cell sublines. Specifically, resistance to enzalutamide induces resistance to abiraterone and vice versa, while maintaining sensitivity to taxanes and olaparib. Conversely, cells with acquired resistance to docetaxel exhibit cross-resistance to both cabazitaxel and olaparib but retain sensitivity to NGATs like enzalutamide and abiraterone. OlapR cells, significantly resistant to olaparib compared to parental cells, are still responsive to NGATs and docetaxel. Moreover, OlapR models display cross-resistance to other clinically relevant PARP inhibitors, including rucaparib, niraparib, and talazoparib. RNA-sequencing analyses have revealed a complex network of altered gene expressions that influence signaling pathways, energy metabolism, and apoptotic signaling, pivotal to cancer’s evolution and progression. The data indicate that resistance mechanisms are distinct among different drug classes. Notably, NGAT-resistant sublines exhibited a significant downregulation of androgen-regulated genes, contrasting to the stable expression noted in olaparib and docetaxel-resistant sublines. These results may have clinical implications by showing that treatments of one class can be sequenced with those from another class, but caution should be taken when sequencing drugs of the same class.

Olaparib, a PARP inhibitor, is a targeted therapy used in treating various cancers, including castration-resistant prostate cancer. Despite its efficacy, resistance to olaparib remains a significant challenge. Understanding the molecular mechanisms underpinning this resistance is crucial for developing more effective treatment strategies. This study focuses on elucidating the role of mitochondrial alterations and the PTEN-induced kinase 1 (PINK1) gene in conferring olaparib resistance in castration-resistant prostate cancer cells. We investigated the transcriptomic and functional differences in mitochondrial activity between olaparib-resistant (2B-OlapR, LN-OlapR) and treatment-naïve prostate cancer cells (C4-2B, LNCaP) in both castration-sensitive and -resistant settings. Through RNA sequencing and gene set enrichment analysis, we identified significant enrichment of mitochondrial activity– and oxidative phosphorylation–related gene sets in olaparib-resistant derived cell lines. Resistant lines exhibited enhanced mitochondrial functionality, including increased basal and maximal respiration rates, as well as elevated ATP production and spare respiratory capacity, compared with parental cells. Subsequent investigations revealed a substantial increase in mitochondrial mass and electron transport chain complex I activity in olaparib-resistant cells. Furthermore, overexpression of the PINK1 gene was observed in resistant cells, which was correlated with resistance to olaparib and poor clinical outcomes in patients with prostate cancer. Inhibition of PINK1 expression significantly reduced mitochondrial function and mass, impaired cell growth, and decreased resistance to olaparib. These findings suggest that PINK1 plays a crucial role in modulating mitochondrial dynamics that confer therapeutic resistance, highlighting its potential as a therapeutic target for overcoming olaparib resistance in prostate cancer. Significance: Olaparib, a PARP inhibitor, is effective against various cancers, including prostate cancer. However, resistance to olaparib poses a significant challenge. This study uncovers that mitochondrial alterations and PINK1 gene overexpression contribute to this resistance in prostate cancer cells. Enhanced mitochondrial functionality and increased PINK1 expression in olaparib-resistant cells underscore the importance of targeting mitochondrial dynamics and PINK1 to develop more effective treatments for overcoming olaparib resistance in prostate cancer.

Enzalutamide resistance remains a significant challenge in the treatment of advanced prostate cancer. Identifying molecular drivers of enzalutamide resistance is crucial for developing effective therapeutic strategies. In this study, we identify insulin-like growth factor–binding protein 3 (IGFBP3) as a key driver of enzalutamide resistance in castration-resistant prostate cancer (CRPC). We demonstrate that IGFBP3 expression is significantly upregulated in enzalutamide-resistant C4-2B MDVR cells compared with parental C4-2B cells. This upregulation was consistently observed across multiple enzalutamide-resistant CRPC models, including LNCaP-derived 42D and 42F cells, as well as long-term enzalutamide-resistant cell lines derived from LNCaP, VCaP, LAPC-4, and CWR-R1 cells. Additionally, enzalutamide treatment directly induced IGFBP3 expression in sensitive cells. Elevated IGFBP3 expression was also observed in CRPC patient samples after enzalutamide treatment and was associated with higher Gleason scores and reduced disease-free survival. Mechanistically, IGFBP3 activates the sphingosine kinase 1 (SphK1)/sphingosine-1-phosphate (S1P) signaling pathway, which promotes cell survival and resistance to enzalutamide. IGFBP3 knockdown decreased SphK1 expression, reduced S1P secretion, and enhanced enzalutamide sensitivity, whereas IGFBP3 overexpression induced SphK1 expression and S1P production, conferring enzalutamide resistance. Inhibition of IGFBP3 via siRNA reduced cell viability, induced apoptosis, and resensitized resistant models to enzalutamide. Similarly, targeting SphK1 with the inhibitor SKI-II suppressed SphK1 activity, reduced S1P production, enhanced enzalutamide sensitivity, and significantly inhibited resistant tumor growth while enhancing enzalutamide sensitivity. Collectively, these findings highlight IGFBP3-mediated SphK1 signaling as a critical mediator of enzalutamide resistance and suggest that targeting the IGFBP3/SphK1/S1P axis represents a promising therapeutic strategy to overcome resistance in advanced prostate cancer.

Background/Objective: The expression of human steroid sulfatase (STS) is upregulated in castration-resistant prostate cancer (CRPC) and is associated with resistance to anti-androgen drugs, such as enzalutamide (Enza) and abiraterone (Abi). Despite the known link between STS overexpression and therapeutic unresponsiveness, the mechanism by which STS confers this phenotype remains incompletely understood. In this study, we sought to understand how STS induces treatment resistance in advanced prostate cancer (PCa) cells by exploring its role in altering mitochondrial activity. Methods: To examine the effects of increased STS expression on mitochondrial respiration and programming, we performed RNA sequencing (RNA-seq) analysis, the Seahorse XF Mito Stress Test, and a mitochondrial Complex I enzyme activity assay in STS-overexpressing cells (C4-2B STS) and in enzalutamide-resistant CPRC cells (C4-2B MDVR). We employed SI-2, the specific chemical inhibitor of STS, on C4-2B STS and C4-2B MDVR cells and evaluated STS activity inhibition on mitochondrial molecular pathways and mitochondrial respiration. Lastly, we examined the effects of dehydroepiandrosterone sulfate (DHEAS) supplementation on C4-2B STS organoids. Results: We present evidence from the transcriptomic profiling of C4-2B STS cells that there are enriched metabolic pathway signatures involved in oxidative phosphorylation, the electron transport chain, and mitochondrial organization. Moreover, upon STS inhibition, signaling in the electron transport chain and mitochondrial organization pathways is markedly attenuated. Findings from the Seahorse XF Mito Stress Test and mitochondrial Complex I enzyme activity assay demonstrate that STS overexpression increases mitochondrial respiration, whereas the inhibition of STS by SI-2 significantly reduces the oxygen consumption rate (OCR) and Complex I enzyme activity in C4-2B STS cells. Similarly, an increased OCR and electron transport chain Complex I enzymatic activity are observed in C4-2B MDVR cells and a decreased OCR upon SI-2 inhibition. Lastly, we show that STS overexpression promotes organoid growth upon DHEAS treatment. Conclusions: Our study demonstrates STS as a key driver of metabolic reprogramming and flexibility in advanced prostate cancer. Disrupting enhanced mitochondrial respiration via STS presents a promising strategy in improving CRPC treatment.