Pui-Kai Li

Resistance to poly(ADP-ribose) polymerase inhibitors (PARPi) remains a major challenge in the treatment of advanced prostate cancer. Although metabolic rewiring has been implicated in this process, the molecular drivers and therapeutic vulnerabilities underlying this adaptation remain poorly defined. We integrated transcriptomic, functional, and clinical analyses to identify mitochondrial regulators of PARPi resistance. RNA sequencing and gene set enrichment analysis revealed robust enrichment of oxidative phosphorylation (OxPhos) pathways in PARPi-resistant prostate cancer cells, with consistent upregulation of NDUFS4, a nuclear-encoded subunit of electron transport chain complex I. Elevated NDUFS4 expression correlated with poor survival in patient cohorts from The Cancer Genome Atlas and SU2C/PCF. Functional analyses demonstrated that genetic knockdown of NDUFS4 impaired complex I activity, reduced mitochondrial mass, and resensitized resistant cells to olaparib. Pharmacologic targeting of NDUFS4 using the niclosamide analog ARVib-7 phenocopied genetic depletion, suppressing mitochondrial respiration and enhancing olaparib efficacy to inhibit the growth of resistant spheroids. Both NDUFS4 silencing and ARVib-7 treatment induced ferroptotic stress, as evidenced by intracellular iron accumulation and altered expression of ferroptosis-associated markers, including COX2, CHAC1, NRF2, and GPX4. These findings identify NDUFS4 as a key mediator of PARPi resistance and a therapeutic vulnerability in advanced prostate cancer. Targeting NDUFS4 disrupts OxPhos and induces ferroptosis, providing a strong rationale for combination strategies with PARPis to overcome drug resistance.

Suppl. Figure 1-10, Table 1-2.

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.

Resistance to poly(ADP-ribose) polymerase inhibitors (PARPi) remains a major challenge in the treatment of advanced prostate cancer. Although metabolic rewiring has been implicated in this process, the molecular drivers and therapeutic vulnerabilities underlying this adaptation remain poorly defined. We integrated transcriptomic, functional, and clinical analyses to identify mitochondrial regulators of PARPi resistance. RNA sequencing and gene set enrichment analysis revealed robust enrichment of oxidative phosphorylation (OxPhos) pathways in PARPi-resistant prostate cancer cells, with consistent upregulation of NDUFS4, a nuclear-encoded subunit of electron transport chain complex I. Elevated NDUFS4 expression correlated with poor survival in patient cohorts from The Cancer Genome Atlas and SU2C/PCF. Functional analyses demonstrated that genetic knockdown of NDUFS4 impaired complex I activity, reduced mitochondrial mass, and resensitized resistant cells to olaparib. Pharmacologic targeting of NDUFS4 using the niclosamide analog ARVib-7 phenocopied genetic depletion, suppressing mitochondrial respiration and enhancing olaparib efficacy to inhibit the growth of resistant spheroids. Both NDUFS4 silencing and ARVib-7 treatment induced ferroptotic stress, as evidenced by intracellular iron accumulation and altered expression of ferroptosis-associated markers, including COX2, CHAC1, NRF2, and GPX4. These findings identify NDUFS4 as a key mediator of PARPi resistance and a therapeutic vulnerability in advanced prostate cancer. Targeting NDUFS4 disrupts OxPhos and induces ferroptosis, providing a strong rationale for combination strategies with PARPis to overcome drug resistance.

Background/Objectives: Hepatocellular carcinoma (HCC) is the predominant form of liver cancer and currently is the second-leading cause of cancer-related mortality globally. Current front-line systemic therapies for advanced HCC offer only modest improvements in patient overall survival. HCC is a sexually dimorphic disease, and cancer progression is driven in part by AR activity. Here, we present novel niclosamide pro-drugs for use in advanced HCC based upon niclosamide’s known anti-AR activity and additional anti-cancer pathway efficacy. Methods: Niclosamide analogs were evaluated for their impacts on the AR protein in two HCC cell lines with different AR phenotypes. Amino acid conjugates of niclosamide were developed, and pharmacokinetic (PK) analyses were conducted to determine improvements in clearance and oral exposure. Finally, niclosamide analogs and amino acid conjugates were evaluated in an in vivo model of HCC. Results: Niclosamide analogs maintained anti-AR properties in HCC. Valine-conjugated niclosamide showed improved oral exposure, positioning it as a potential therapeutic in advanced HCC. Conclusions: Valine–niclosamide improves upon niclosamide’s poor solubility and oral bioavailability, increasing its utility for a variety of therapeutic uses. Further study of valine–niclosamide in advanced HCC and in other cancers or diseases is warranted.

Mitochondrial uncouplers have shown clinical potential across various diseases, including cancer. Niclosamide, an FDA-approved anthelmintic drug, acts as a mild mitochondrial uncoupler and has demonstrated anticancer activity in multiple preclinical cancer models. However, its clinical application remains limited, with some attributing this to poor bioavailability, while the underlying mechanisms are still unclear. Here, we demonstrate that niclosamide exhibits a dose-dependent biphasic effect, promoting uncoupling at low concentration while acting as a mitochondrial inhibitor at high concentration, which could restrict its therapeutic window and limit efficacy. To overcome this challenge, we aimed to develop next-generation mitochondrial uncouplers (MUs) by synthesizing and evaluating novel Niclosamide derivatives with enhanced therapeutic potential. Through structural modifications, we optimized uncoupling activity while reducing inhibitory toxicity, thereby expanding the pharmacological window. Our findings suggest that fine-tuning the molecular structure of mitochondrial uncouplers could provide a safer and more effective metabolic reprogramming strategy for cancer treatment.