Deciphering the Significance of Lipoylation in Prostate Cancer Bone Metastasis to Develop Innovative Therapeutics - Abstract Most patients with advanced Prostate cancer (PCa) often develop bone metastases (BoM), leading to bone pain, skeletal fracture, and increased mortality rates. The underlying pathophysiology of PCa-BoM is complex, primarily due to a limited understanding of the bone microenvironment’s role in promoting metastatic progression. Cuproptosis, a newly identified copper-dependent cell death mechanism, depends on protein lipoylation and is regulated by Ferredoxin 1 (FDX1), a critical modulator of this process. However, no experimental/clinical studies have been reported showing the effect of protein lipoylation in metastasis, especially the effect of the bone microenvironment of protein lipoylation. Our preliminary data showed that the FDX1 expression is appreciably higher in bone metastatic patients, coupled with a marked reduction in lipoylated protein levels. Mechanistically, we found that androgen receptor (AR)-targeted therapies and osteoblast interactions suppress lipoylation, thereby promoting bone metastasis through the MID1-AR signaling axis. Furthermore, despite increased LIAS (lipoic acid synthetase) expression, endogenous lipoic acid (a key substrate for lipoylation) is downregulated in PCa, impairing lipoylation efficiency and hindering cuproptosis. This imbalance suggests a tumor-promoting role for FDX1 in the absence of sufficient lipoic acid, facilitating metastatic progression. These observations provide a rationale for further exploring the lipoylation process in PCa-BoM and suggest a novel therapeutic strategy to target PCa-driven BoM. Based on these background and preliminary data, we hypothesize that FDX1, via the FDX1-MID1 axis, drives BoM by modulating AR signaling. Enhancing lipoylation can restore the FDX1-LIAS-mediated lipoylation process in PCa, counteracting its impairment and promoting therapeutic efficacy. Disrupting the BoM vicious cycle by therapeutically inducing cuproptosis with α-lipoic acid and the Cu ionophore disulfiram (DSF) offers a promising approach to treat PCa- BoM effectively. We will test our hypothesis using two specific aims using relevant experimental and clinical settings. In Aim 1, we will define the role of the FDX1-LIAS-MID1 axis in regulating lipoylation, metastatic niche formation, and AR therapy resistance and will establish the significance of lipoylation in PCa-BoM. In Aim 2, we will evaluate the therapeutic effectiveness of α-lipoic acid (α-LA) and DSF in a preclinical syngeneic mouse model of BoM, focusing on cuproptosis. The proposed novel mouse models and therapeutic preclinical studies, including extensive bone microenvironment analysis, and spatial transcriptomics will define lethal PCa and BoM biology. The outcome of preclinical studies targeting the BoM with α-LA and DSF/Cu has the potential to directly go for clinical trial as both are supplementation/FDA-approved drugs with known tolerance and pharmacology with the minimum side effect. The successful completion of the proposed study holds the potential to benefit millions of PCa patients suffering from bone metastasis.
