Rheumatoid arthritis (RA) is pathologically marked by joint inflammation and damage. Although the association between spermidine and RA has been recognized, the precise contribution of spermine oxidase (SMOX)-the enzyme catalyzing spermidine synthesis-to RA pathogenesis remains undefined. It’s observed in this study that SMOX was responsible for inflammatory stimuli that its expression increased obviously when RA-associated fibroblast-like synoviocytes (FLSs) were challenged by inflammatory factors. Functionally, silencing SMOX could inhibit migration, invasion, and cytokine production, but induced apoptosis of RA-FLS. Moreover, inhibition of SMOX using JNJ-9350 yielded anti-inflammatory effects comparable to those achieved by gene silencing in RA-FLS. In vivo experiments demonstrated that JNJ-9350 could effectively reduce the severity of arthritis, minimize histopathological damage, and prevent bone erosion in collagen antibody-induced arthritis (CAIA) mice. The present results indicate that SMOX is implicated in the development of RA and suggest that targeting SMOX could be a novel treatment strategy.

Background Rheumatoid arthritis (RA) is characterized by synovial hyperplasia driven by fibroblast-like synoviocytes (FLSs), which exhibit resistance to endoplasmic reticulum (ER) stress-induced apoptosis. However, the molecular mechanisms underlying this pathogenic phenotype remain elusive. Methods HECTD2 expression was assessed in the synovial tissue by RT-qPCR and Western blot. Gain or loss of functional analysis was applied to evaluate the biological roles of HECTD2 in RA FLSs. Cell viability, apoptosis, migration and invasion were assessed by EdU staining, CCK-8 assay, flow cytometry and transwell chambers. The effects of HECTD2 in collagen antibody-induced arthritis (CAIA) mouse model were evaluated by scoring synovitis, hyperplasia, cartilage degradation, and bone destruction. The ubiquitination experiments were used to verify the relationship between HECTD2 and p62. Results HECTD2 expression was selectively upregulated when RA FLSs were stimulated by ER stress inducers. Functionally, silencing HECTD2 could inhibit the viability and induce the apoptosis of RA FLSs in the presence of ER stress. Mechanistically, ER stress induces HECTD2 expression, which in turn promotes the ubiquitination and proteasomal degradation of p62, a multifunctional molecule crucial for RA FLSs apoptosis. This HECTD2-mediated p62 degradation sustains the apoptotic-resistant and hyperproliferative phenotype of RA FLSs. Importantly, pharmacological inhibition of HECTD2 with BC-1382 significantly attenuated arthritis severity in CAIA mouse models. Conclusions Our findings reveal a novel HECTD2-p62 axis that drives RA pathogenesis and highlight HECTD2 as a promising therapeutic target for RA.

Emerging evidence highlights that metabolic reprogramming profoundly shapes the tumor microenvironment and immune evasion in prostate cancer. However, the functional role and mechanisms of tryptophan metabolism in prostate cancer progression remain unclear. Through single-cell transcriptomic analysis, we identified one tumor cell subtype characterized by high expression of 3-hydroxyanthranilate 3,4-dioxygenase (HAAO) and enhanced kynurenine pathway activity. This subpopulation leads to the accumulation of quinolinic acid (QA), a metabolic intermediate that could activate the mevalonate (MVA) pathway. Mechanistically, QA directly binds to and stabilizes farnesyl diphosphate synthase (FDPS), a key MVA pathway enzyme, thereby enhancing cholesterol biosynthesis and fueling androgen receptor (AR)-driven transcriptional programs. This HAAO/QA-FDPS axis establishes a metabolic crosstalk that links tryptophan catabolism to lipid metabolism, sustaining prostate tumor progression. Furthermore, an integrated prognostic model incorporating this pathway signatures outperforms other clinical variables alone, and HAAO-high tumors exhibit heightened sensitivity to combined inhibition of the kynurenine and AR pathways. Our study unveils a novel metabolic vulnerability in prostate cancer and provides a mechanistic rationale for targeting the HAAO/QA-FDPS axis for therapy.

Emerging evidence highlights that metabolic reprogramming profoundly shapes the tumor microenvironment and immune evasion in prostate cancer. However, the functional role and mechanisms of tryptophan metabolism in prostate cancer progression remain unclear. Through single-cell transcriptomic analysis, we identified one tumor cell subtype characterized by high expression of 3-hydroxyanthranilate 3,4-dioxygenase (HAAO) and enhanced kynurenine pathway activity. This subpopulation leads to the accumulation of quinolinic acid (QA), a metabolic intermediate that could activate the mevalonate (MVA) pathway. Mechanistically, QA directly binds to and stabilizes farnesyl diphosphate synthase (FDPS), a key MVA pathway enzyme, thereby enhancing cholesterol biosynthesis and fueling androgen receptor (AR)-driven transcriptional programs. This HAAO/QA-FDPS axis establishes a metabolic crosstalk that links tryptophan catabolism to lipid metabolism, sustaining prostate tumor progression. Furthermore, an integrated prognostic model incorporating this pathway signatures outperforms other clinical variables alone, and HAAO-high tumors exhibit heightened sensitivity to combined inhibition of the kynurenine and AR pathways. Our study unveils a novel metabolic vulnerability in prostate cancer and provides a mechanistic rationale for targeting the HAAO/QA-FDPS axis for therapy.

The clinical paradox of local estrogen therapy in pelvic organ prolapse—its widespread application juxtaposed with inconsistent therapeutic outcomes—highlights a critical gap in our understanding of its actions within the native tissue architecture. To resolve this, we employed high-definition spatial transcriptomics, achieving a near-cellular resolution map of the postmenopausal vaginal wall. This spatial atlas directly visualized estrogen’s core mechanism: the orchestration of a structured HAS1 + fibroblast-pericyte reparative niche around vasculature. Estrogen directs the recruitment of POLR3G-driven, HAS1 + fibroblasts into this precise micro-anatomical location, enabling their functional coupling with pericytes. This co-localization facilitates a rewired fibroblast-pericyte signaling axis, enhancing pro-repair communication. Computational pharmacology further affirms this niche as a druggable functional unit. Our findings establish a new paradigm: estrogen's efficacy is not mediated by broad tissue stimulation, but through the precise spatial engineering of a multicellular repair unit, a mechanism unveiled only through high-definition spatial mapping and one that redefines the future of targeted therapeutic strategies.

The aggressive phenotype of prostate cancer (PCa) requires adaptation to androgen deprivation (AD) to progress into castration-resistant PCa (CRPC), including adaptation to AD-induced oxidative stress. However, our understanding of the oncogenes that maintain the redox balance during CRPC progression is limited. Here, we identified Bromodomain-containing protein 9 (BRD9) as a metabolic checkpoint for reprogramming cell metabolism to support tumor growth and impart a castration-resistant phenotype under metabolic and oxidative stress. Following oxidation, BRD9 recruited the nuclear transcription factor-Y A-subunit (NFYA) to induce glycogen phosphorylase L (PYGL) expression, which directed glucose utilization through the pentose phosphate pathway, generating NADPH, and promoting clearance of reactive oxygen species (ROS), thus maintaining redox balance. By disturbing redox homeostasis, BRD9 inhibition exerted oxidative pressure on PCa cells, sensitizing them to radiotherapy. This work identified BRD9 as a novel component in antioxidant reprogramming and indicates BRD9 targeting as a promising treatment strategy for PCa therapy.

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by chronic synovitis and skeletal joint deformities, often accompanied by systemic symptoms. Over the past few decades, various susceptibility factors for RA have been revealed, and numerous therapeutic drugs have been developed, including analgesics, glucocorticoids, non-steroidal anti-inflammatory drugs (NSAIDs), disease-modifying antirheumatic drugs (DMARDs), and biological agents (bDMARDs). Despite the availability of multiple treatment options, the therapeutic outcomes for some patients remain suboptimal due to the complex pathogenesis of RA. As a key pathological mechanism, programmed cell death (PCD) in RA has received extensive attention. Dysregulation of PCD in RA impacts the progression of the disease. This article systematically reviews the roles of various cell death modalities, including apoptosis, necroptosis, ferroptosis, pyroptosis, and autophagy in the pathophysiology of RA, aiming to provide a theoretical basis and direction for the discovery of new therapeutic targets and drug development.

Immunotherapy of prostate cancer (PCa) remains challenging due to the immunosuppressive nature of the tumor microenvironment (TME). Oxidative damage enhances immunogenic cell death (ICD) to counteract immunotherapy resistance in PCa, but is limited by tumor antioxidant defenses and single-modality reactive oxygen species (ROS) generation in the TME. Herein, we report an innovative polyamine-based strategy that overproduces hydrogen peroxide and acrolein to simultaneously induce oxidative/carbonyl stress while suppressing endogenous antioxidant systems, thereby synergistically amplifying oxidative/carbonyl damage, which triggers robust ICD and achieves potent antitumor efficacy. Both in vitro and in vivo assays demonstrated that the nanoparticles, modified with a PCa-targeting peptide, could generate acrolein to induce mitochondrial destruction, DNA damage, and accumulate lipid peroxidation. In addition, they enhanced the recruitment of mature dendritic cells and T cells within the TME, thus inhibiting lung metastasis and tumor rechallenge. This work proposes an immunotherapy strategy using polyamine metabolism to induce combined carbonyl and oxidative stress, providing a novel approach for overcoming cold TME resistance in advanced PCa.

BACKGROUND:Signal-induced proliferation-associated 1 like 3 (SIPA1L3) is a member of the protein family. Very limited data are currently available regarding the role of SIPA1L3 in human carcinoma. Therefore, in this study, we investigated the expression pattern and function of SIPA1L3 in non-small cell lung cancer (NSCLC). METHODS:We analyzed the distribution of SIPA1L3 in NSCLC specimens by immunohistochemistry, the relationship between SIPA1L3 expression and patient clinicopathological features, and investigated the effect of SIPA1L3 on cell growth and invasion in vivo and in vitro using small interfering RNA. Western blotting and immunoprecipitation were performed to demonstrate the interaction between SIPA1L3 and tight junction-associated angiomotin (AMOT) and Pals1-associtated tight junction protein. RESULTS:We found that SIPA1L3 was overexpressed in NSCLC clinical tissue samples and was associated with several clinicopathological factors. SIPA1L3 affects the proliferation and invasion of cancer cells both in vivo and in vitro. Using a SIPA1L3 mutant, we found that SIPA1L3 interacts with AMOT through its PDZ domain, which inhibits the binding of AMOT to Pals1-associtated tight junction protein and further decreases AMOT anchoring to tight junctions. CONCLUSION:Our findings suggested that SIPA1L3 promotes tumorigenesis in lung cancer cells through its PDZ domain-mediated interaction with AMOT, suggesting that SIPA1L3 is a novel candidate gene that contributes to the malignant phenotype of lung cancer.

Background T-cell exhaustion induced by the tumor microenvironment is an important factor in posing a major challenge to effective cancer immunotherapy. Immune checkpoint inhibitors aim to reverse T-cell exhaustion. However, the effectiveness of immune checkpoint inhibitors is often limited due to their off-target effects and single targets. Herein, we attempt to identify molecular targets that can regulate the expression of multiple immune checkpoints to reverse T-cell exhaustion.Methods NSG mice with xenotransplantation of human bladder cancer cells were used to investigate the function of nuclear paraspeckle assembly transcript 1 (NEAT1) in T-cell exhaustion. Chromatin isolation by RNA purification, chromatin immunoprecipitation, and luciferase assays was employed to investigate the molecular mechanisms by which NEAT1 regulates expression of target genes.Results NEAT1, a bladder cancer-related long non-coding RNA (lncRNA), promotes lactate production in tumor cells by binding to the lactate dehydrogenase A gene. This lactate production subsequently inhibits NEAT1 expression in CD8+T cells. Furthermore, NEAT1 in CD8+T cells plays a crucial role in modulating the immune response of CD8+T cells against tumor cells. Our findings indicate that NEAT1 regulates the expression of multiple immune checkpoint genes by directly binding to them and inhibiting transcription through the alteration of histone lactylation near transcriptional start sites, which affects RNA polymerase II recruitment.Conclusions lncRNA NEAT1 serves as a modulator of the antitumor response of CD8+T cells in the bladder tumor microenvironment and may represent a therapeutic target for reversing T-cell exhaustion.

Androgen deprivation therapy is the primary treatment for advanced prostate tumors. While initially effective, tumor progression to the therapy-resistant stage is inevitable. Paradoxically, UDP glucuronosyltransferase family 2 member B17 (UGT2B17), the key enzyme responsible for androgen catabolism in prostate tumor cells, is upregulated in therapy-resistant tumors, though its role in tumor progression remains unclear. Here, we demonstrate that UGT2B17 possesses multiple oncogenic functions independent of androgen catabolism. It modulates protein-folding pathways, allowing tumor cells to endure therapy-induced stress. UGT2B17 also regulates transcription associated with cell division and the DNA damage response, enabling unchecked cell proliferation. Targeting the newly identified UGT2B17 functions using a combination of inhibitors reduced tumor growth in therapy-resistant tumor models, highlighting a promising therapeutic strategy. Collectively, these findings reveal a mechanism by which prostate tumors exploit UGT2B17 to evade therapy and highlight its potential as a therapeutic target in advanced prostate cancer.

Diabetic nephropathy (DN) is one of the most serious microvascular complications of diabetes mellitus. It is characterized by progressive tubulointerstitial fibrosis. The aim of this study was to investigate the role of exosomal circular RNA (circRNAs) in regulating fibroblast growth factor 9 (FGF9) expression in DN through a competitive endogenous RNA (ceRNA) mechanism, and to reveal its potential therapeutic targets. Exosomes were isolated from serum of 3 healthy people and 3 patients with DN by ultra-fast centrifugation method, and the circRNA-miRNA-FGF9 regulatory network was constructed by combining high-throughput circRNA sequencing, bioinformatics analysis and weighted co-expression network (WGCNA). The results showed that the expression of circRNAs in serum exosomes of DN patients was significantly down-regulated, and hsa_circ_0006382 and hsa_circ_0019539 targeted the expression of FGF9 by binding to miR-34a-5p, miR-766-3p, miR-147a and miR-27a-3p. Further verification showed that the expression of FGF9 was decreased in renal tissues of DN patients (AUC = 0.902), and its recombinant protein could inhibit the expression of α-SMA and vimentin in high glucose-induced NRK-52E cells, indicating that activation of the circRNA/miRNA-FGF9 network promotes the EMT of renal tubular epithelial cells. This study revealed for the first time the mechanism of the circRNA-miRNA-FGF9 regulatory network in DN fibrosis, providing a theoretical basis for the development of diagnostic markers and targeted therapy strategies based on exosomal circRNA.

The production of type I interferon (IFN) is precisely modulated by host to protect against viral infection efficiently without obvious immune disorders. Elucidating the tight control towards type I IFN production would be helpful to get insight into natural immunity and inflammatory diseases. As yet, however, the mechanisms that regulate IFN-β production, especially the epigenetic regulatory mechanisms, remain poorly explored. This study elucidated the potential function of Peptidylarginine deiminases (PADIs)-mediated citrullination in innate immunity. We identified PADI4, a PADIs family member that can act as an epigenetic coactivator, could repress IFN-β production upon RNA virus infection. Detailed experiments showed that PADI4 deficiency increased IFN-β production and promoted antiviral immune activities against RNA viruses. Mechanistically, the increased PADI4 following viral infection translocated to nucleus and recruited HDAC1 upon binding to Ifnb1 promoter, which then led to the deacetylation of histone H3 and histone H4 for repressing Ifnb1 transcription. Taken together, we identify a novel non-classical role for PADI4 in the regulation of IFN-β production, suggesting its potential as treatment target in inflammatory or autoimmune diseases.

BackgroundThis study introduces a novel prognostic tool, the Disulfidoptosis-Related lncRNA Index (DRLI), integrating the molecular signatures of disulfidoptosis and long non-coding RNAs (lncRNAs) with the cellular heterogeneity of the tumor microenvironment, to predict clinical outcomes in patients with clear cell renal cell carcinoma (ccRCC).MethodsWe analyzed 530 tumor and 72 normal samples from The Cancer Genome Atlas (TCGA), employing k-means clustering based on disulfidoptosis-associated gene expression to stratify ccRCC samples into prognostic groups. lncRNAs correlated with disulfidoptosis were identified and used to construct the DRLI, which was validated by Kaplan-Meier and receiver operating characteristic curves. We utilized single-cell deconvolution analysis to estimate the proportion of immune cell types within the tumor microenvironment, while the ESTIMATE and TIDE algorithms were employed to assess immune infiltration and potential response to immunotherapy.ResultsThe Disulfidoptosis-Related lncRNA Index (DRLI) effectively stratified ccRCC patients into high and low-risk groups, significantly impacting survival outcomes (P<0.001). High-risk patients, marked by a unique lncRNA profile associated with disulfidoptosis, faced worse prognoses. Single-cell analysis revealed marked tumor microenvironment heterogeneity, especially in immune cell makeup, correlating with patient risk levels. In prognostic predictions, DRLI outperformed traditional clinical indicators, achieving AUC values of 0.779, 0.757, and 0.779 for 1-year, 3-year, and 5-year survival in the training set, and 0.746, 0.734, and 0.750 in the validation set. Notably, while the constructed nomogram showed exceptional predictive capability for short-term prognosis (AUC=0.877), the DRLI displayed remarkable long-term predictive accuracy, with its AUC value reaching 0.823 for 10-year survival, closely approaching the nomogram’s performance.ConclusionsThe study introduces the DRLI as a groundbreaking molecular stratification tool for ccRCC, enhancing prognostic precision and potentially guiding personalized treatment strategies. This advancement is particularly significant in the context of long-term survival predictions. Our findings also elucidate the complex interplay between disulfidoptosis, lncRNAs, and the immune microenvironment in ccRCC, offering a comprehensive perspective on its pathogenesis and progression. The DRLI and the nomogram together represent significant strides in ccRCC research, highlighting the importance of molecular-based assessments in predicting patient outcomes.

Legends for Supplementary Figures and Tables.

Objective: Androgen deprivation therapy (ADT) is still the principal treatment option for prostate cancer (PCa). In addition to reactivation of androgen receptor signaling, the resistance of PCa to apoptosis during ADT also contributes to castration resistant PCa (CRPC). A previous study reported that gene transfer of IL-13Rα2 into PCa cells sensitized the cells to the IL-13R-targeted cytotoxin IL13Rα1, leading to apoptosis. Compared with IL-13Rα2, IL13Rα1 is more constitutively expressed in PCa cells, but its function in PCa remains to be established.Methods: We determined the role and expression of IL13Rα1 in PCa cancer cells using western blotting, flow cytometry, and cell proliferation assays. Co-immunoprecipitation and mass spectrometry were used to identify the proteins that interacted with IL13Rα1, to elucidate its function. Results: In this study, we showed that IL13Rα1 was selectively suppressed in androgen-deprived PCa cells and that its suppression tended to be associated with poor prognoses of PCa patients. IL13Rα1 overexpression promoted apoptosis and inhibited tumor growth under androgen-deprived or castrated conditions (P < 0.01). Mechanistically, IL13Rα1 recruited and facilitated ubiquitin protein ligase E3C-mediated ubiquitination and degradation of hexokinase 2 (HK2), resulting in glycolytic inhibition and eventually leading to PCa cell apoptosis. Furthermore, our data revealed that mutated ataxia-telangiectasia kinase phosphorylated and facilitated the selective ubiquitin proteasome-mediated degradation of HK2. Notably, IL13Rα1-overexpressing PCa cells were more susceptible to apoptosis and exhibited reduced tumor growth after exposure to the HK2 inhibitor, 2-deoxy-D-glucose (P < 0.01). Conclusions: Our data identified a tumor suppressor role for IL13Rα1 in preventing the resistance of PCa cells to apoptosis during androgen deprivation by inhibiting glycolysis. IL13Rα1-mediated signaling involving HK2 may therefore provide a novel treatment target and strategy for CRPC.

BACKGROUND:Despite the clinical success of androgen receptor (AR)-targeted therapies, prostate cancer (PCa) inevitably progresses to castration-resistant prostate cancer (CRPC). Transcription factor 6 α (ATF6α), an effector of the unfolded protein response (UPR) that modulates the cellular response to endoplasmic reticulum (ER) stress, has been linked to tumor development, metastasis, and relapse. However, the role of ATF6α in CRPC remains unclear. METHODS:The effect of ATF6α on the CRPC-like phenotype in PCa cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carb-Oxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS), 5-Bromo-2-deoxyUridine (BrdU) incorporation analysis, and cell death assay. Mechanistically, bioinformatic analysis was utilized to evaluate the potential of PLA2G4A as the target of ATF6α. Moreover, Western blot analysis, real-time polymerase chain reaction, chromatin immunoprecipitation, arachidonic acid (AA), and prostaglandin E2 (PGE2) assays were performed to identify the regulatory effect of ATF6α on PLA2G4A. RESULTS:In this study, we found that the increase of ATF6α expression in response to androgen deprivation generates PCa cells with a CRPC-like phenotype. PCa cells with high levels of ATF6α expression are resistant to ferroptosis, and genetic and pharmacological inhibition of ATF6α could, therefore, promote the ferroptotic death of tumor cells and delay PCa progression. Molecular analyses linked ATF6α regulation of ferroptosis to the PLA2G4A-mediated release of AA and the resulting increase in PGE2 production, the latter of which acts as an antiferroptotic factor. CONCLUSIONS:This study defines ATF6α as a novel antiferroptotic regulator that exacerbates PCa progression. In addition, our data establish ATF6α-PLA2G4A signaling as an important pathological pathway in PCa, and targeting this pathway may be a novel treatment strategy.

Background and PurposeAzithromycin is a macrolide antibiotic with anti‐inflammatory properties. We aim to substantiate the treatment potential of azithromycin in rheumatoid arthritis.Experimental ApproachGene expression profiles were collected by RNA sequencing and the effects of azithromycin were assessed by in vitro and in vivo assays on the effects of azithromycin‐mediated blockade of glucose‐regulated protein 78 (GRP78). Anti‐inflammatory activity of azithromycin was measured in fibroblast‐like synoviocytes from rheumatoid arthritis patients and in collagen‐induced arthritis in DBA/1 mice. Characterization of the binding of azithromycin to GRP78 was performed using drug affinity responsive target stability, proteomics and cellular thermal shift assays. Azithromycin‐mediated inhibition of GRP78 and its relationship to its anti‐arthritic activity was assessed.Key ResultsAzithromycin reduced proinflammatory factor production, cell migration, invasion and chemoattraction and enhanced apoptosis, reducing the deleterious inflammatory response of rheumatoid arthritis fibroblast‐like synoviocytes in vitro. Azithromycin ameliorated the severity of collagen‐induced arthritis lesions as efficiently as the TNFα inhibitor etanercept. Transcriptional analyses suggested that azithromycin treatment impairs signalling cascades associated with cholesterol and lipid biosynthesis. GRP78 was identified as a novel target of azithromycin. Azithromycin‐mediated activation of the unfolded protein response via the inhibition of GRP78 activity is required not only for inducing the expression of C/EBP‐homologous protein (ChOP) but also for the activating sterol‐regulatory element binding protein (SREBP) and its targeted genes involved in cholesterol and lipid biosynthetic processes. Furthermore, deletion of GRP78 abolished the anti‐arthritic activity of azithromycin.Conclusion and ImplicationsThese findings indicate that azithromycin can used to treat rheumatoid arthritis.

Background The development of castration-resistant prostate cancer (CRPC) remains a major obstacle in the treatment of prostate cancer (PCa). Dysregulated mitochondrial function has been linked to the initiation and progression of diverse human cancers. Deciphering the novel molecular mechanisms underlying mitochondrial function may provide important insights for developing novel therapeutics for CRPC. Methods We investigate the expression of the protein tyrosine phosphatase receptor type F polypeptide interacting protein alpha 4 (PPFIA4) using public datasets and tumor specimens from PCa cases by immunohistochemistry. Gain- and loss-of-function studies are performed in PCa cell lines and mouse models of subcutaneous xenograft to characterize the role of PPFIA4 in CRPC. Gene expression regulation is evaluated by a series of molecular and biochemical experiments in PCa cell lines. The therapeutic effects of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) inhibitor combined enzalutamide are assessed using in vitro functional assays and in vivo mouse models. Results We show that the increase of PPFIA4 exacerbates aggressive phenotype resembling CRPC. A fraction of PPFIA4 localizes to mitochondria and interacts with MTHFD2, a key enzyme for one-carbon metabolism. Androgen deprivation increases the translocation of PPFIA4 into mitochondria and increases the interaction between PPFIA4 and MTHFD2, which result in the elevation of tyrosine phosphorylated MTHFD2. Consequently, the levels of NADPH synthesis increase, resulting in protection against androgen deprivation-induced mitochondrial dysfunction, as well as promotion of tumor growth. Clinically, PPFIA4 expression is significantly increased in CRPC tissues compared with localized PCa ones. Importantly, an MTHFD2 inhibitor, DS18561882, combined with enzalutamide can significantly inhibit CRPC cell proliferation in vitro and tumor growth in vivo . Conclusion Overall, our findings reveal a PPFIA4-MTHFD2 complex in mitochondria that links androgen deprivation to mitochondrial metabolism and mitochondrial dysfunction, which suggest a potential strategy to inhibit CRPC progression.