Immune checkpoint inhibitors (ICIs) have limited efficacy in prostate cancer. Radiation therapy (RT) combined with ICIs and PI3K inhibition may enhance anti-tumor immune activity. RT-induced cytosolic double-stranded DNA (dsDNA) was measured in human and mouse prostate cancer cell lines as the surrogate upstream marker consistent with cGAS-STING engagement. In a syngeneic mouse model for castration-resistant prostate cancer (Myc-CaP in FVB mice), triple therapies were studied: (1) anti-CTLA-4, anti-PD-1, and RT, and (2) PIM kinase inhibitor PIM447, anti-PD-1, and RT. Mass cytometry (CyTOF) was used to measure the tumor-immune profile. The peak induction of cytosolic dsDNA was at an RT dose of 13 Gy. In the mouse model, triple therapy with anti-CTLA-4, anti-PD-1, and RT doubled the median survival compared to monotherapy (32 days vs 11 to 22 days, p<0.006). Triple therapy with the PIM kinase inhibitor PIM447, anti-PD-1, and RT nearly tripled the median survival compared to PIM447 monotherapy (82 days vs 29 days, p=0.002). Mass cytometry analysis revealed that the combination of anti-PD-1 and RT reduced myeloid-derived suppressor cells and tissue-associated macrophages and enhanced CD8+ T-cell infiltration. Although prostate cancer is an immunocold entity, RT can trigger immune activation, consistent with engagement of the cGAS-STING signaling pathway (cytosolic dsDNA serving as a surrogate upstream marker). In triple therapy, RT can enhance the efficacy of ICI and PI3K-targeted drug therapy, significantly improving overall survival in a mouse model of CRPC. A combination of RT, ICIs, and PIM kinase inhibition may help overcome immune resistance in prostate cancer. This combination therapy approach supports further preclinical validation and careful clinical evaluation and warrants further clinical investigation to optimize treatment strategies for CRPC.

Co-activating the intrinsic FcRγ/TLR4 signaling axis enhances the antitumor activity of NKG2D CAR-macrophages against prostate cancer.

Chimeric antigen receptor-T (CAR-T) adoptive transfer therapy has shown remarkable efficacy in hematologic malignancies. However, the therapeutic efficacy of CAR-T in treating solid tumors, particularly "cold tumors" such as prostate cancer, is significantly restricted by the cumbersome ex vivo manufacturing, impaired T cell fitness, and an immunosuppressive tumor microenvironment that blunts T cell function. Here, we successfully constructed a nanodelivery system based on zeolitic imidazolate framework-8 (ZIF-8). This system exhibited high CAR-gene encapsulation efficiency, reduced nonspecific hepatic accumulation, targeted delivery to tumor-associated macrophages (TAMs), and efficient intracellular gene transfection efficiency, enabling in situ construction of chimeric antigen receptor macrophage (CAR-M). Co-delivery of IFN-γ and CAR genes not only maintained the specific tumor-killing and phagocytic activity of CAR-Ms against tumor cells but also activated adaptive immunity, inducing excellent antitumor efficacy, as evidenced by the observed 95.54% inhibition of tumor growth in a prostate cancer mouse model. This strategy provides a promising approach for systematic in vivo editing of CAR-Ms.

Abstract Background: Prostate cancer (PCa) remains a highly lethal disease due to the rapid emergence of neuroendocrine (NE)-like variants from adenocarcinoma. It is predicted that de novo NEPC will emerge from 17% of localized PCa, while treatment-related NEPC will account for 20% of advanced PCa. Clinically, NEPC patients frequently harbor visceral metastasis (62%, P&amp;lt;0.001) compared with CRPC patients (24%), with poor overall survival of 12-17 months. Thus, exploring the unknown mechanism underlying cell-state transition from adeno to NEPC will help identify new targets to overcome lineage plasticity and improve PCa patient survival. Methods: We developed a novel indolent and metastatic PCa mouse model by overexpressing cMyc and knocking out Pten with/without Mutant p53 (R172H). Global transcriptional profiling was performed in indolent and aggressive mice and ASPORIN (ASPN) knockdown (KD) to identify differential gene expression, biological, and pathway analyses. ASPN ectopic overexpression (OE) and KD clones confirmed ASPN biological function and on-target proteins/genes using RT-PCR and western blot analyses. ASPN in vitro function was analyzed in the Incucyte® live imaging system, colony growth assay, and proliferation assays. Results: The novel Ptenfl/fl; Hi-Myc; Trp53R172H/+; Rosa-26; PB-Cre4+ (PCTPLuc) mouse exhibits phenotypic resemblance to PCa visceral metastasis to the lung, liver, inguinal lymph node, and intestine with poor survival as compared with age-matched indolent Ptenfl/fl; Hi-Myc; Rosa-26Luc; PB-Cre4+ (PCPLuc). Unbiased RNA-Seq analysis of PCa adenocarcinoma tissues from PCTP mice revealed a significant association between unique extracellular matrix (ECM) protein clusters and liver and lung metastasis. Asporin (ASPN) emerged as the top differentially expressed ECM protein among the top 25 genes. Consistently, ASPN knockdown and overexpression were directly associated with PCa cellular phenotypes of proliferation and colony growth. Mechanistically, ASPN modulation impacts pERK, CyclinD3, EMT proteins, and a neuroendocrine-like phenotype, as well as cell differentiation-related transcriptomes such as cellular retinoic acid-binding protein 2 (CRABP2), along with Chromogranin A (CHGA), NeuroD1, and INSM1. Using a publicly available TCGA database, we observed a significant overexpression of ASPN and CRABP2 in PCa tissues (N=497) relative to normal (N=52) (P&amp;lt;0.001). Finally, ASPN ectopic overexpression in immortalized RWPE-1 cells confirmed an aggressive in vitro phenotypes. Conclusion: For the first time, we explored the influence of ASPN/CRABP2 and other signaling involved in luminal epithelial to neuroendocrine differentiation and validated CRABP2 as a novel target to prevent NEPC transdifferentiation. Our findings support ASPN’s new role, mechanism(s) and as a target for PCa and other visceral metastasis disease. Citation Format: Parthasarathy Seshacharyulu, Shobhit Lall, Sushanta Halder, Sakthivel Muniyan, Zahraa Wajih Alsafwani, Ramakanth Chirravuri-Venkata, Moorthy P. Ponnusamy, Surinder K. Batra. Novel ASPORIN/CRABP2 axis drives cell-state plasticity from adenocarcinoma to neuroendocrine-like prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 5573.

Prostate cancer (PCa) is the second most common cancer and second leading cause of cancer death for American men. Chemoprevention by using phytochemicals offers a promising approach to improve outcomes due to their ability to act on cancer cell metabolism and growth while maintaining low toxicity profiles. The goal of this study was to assess the combination of xanthohumol (XAN) and ursolic acid (UA) given in the diet for synergistic efficacy against PCa progression and identify potential mechanisms of action. PCa cells were treated with the combination to evaluate cell survival and colony formation. Two mouse models of PCa were used to evaluate tolerability and efficacy of dietary administration of the combination and to further understand mechanism(s) of action. The combination of XAN + UA reduced PCa cell survival and colony formation. The combination given in the diet significantly and synergistically inhibited growth of HMVP2 PCa allograft tumors and also inhibited PCa progression in HiMyc mice. Mechanistically, inhibition of polyamine synthesis and epithelial-to-mesenchymal transition contributed to the inhibition of HMVP2 allograft tumor growth, while the inhibition of PCa progression in HiMyc mice was associated with activation of the unfolded protein response pathway and apoptosis. Further studies in cultured PCa cells revealed additional effects of the combination on several oncogenic signaling pathways (e.g, phospho-STAT3) and cell cycle regulatory proteins (e.g, cyclin D1, phospho-Rb).

The clinical standard practice of [177Lu]Lu-PSMA-617 therapy is a single injection per treatment cycle, with 6 weeks between cycles. While clinical schedules currently utilize single-bolus cycles, splitting a treatment cycle into multiple smaller injections has demonstrated benefits in other radionuclide therapies, preclinically and in clinical studies. Potential mechanisms for improved therapeutic efficacy include receptor recycling, receptor upregulation, or targeting new cell growth between fractions. This study aims to investigate the effects on tumor size and animal survival, in a mouse model of prostate cancer, of fractionating [177Lu]Lu-PSMA-617 therapy compared to the same total activity in a single injection. BALB/c mice bearing subcutaneous LNCaP prostate cancer tumors, below 650 mm3 in volume, were treated with either 1 × 30 MBq, 2 × 15 MBq (24-hour window), or 2 × 15 MBq (6-day window). SPECT/CT imaging showed a higher, but not significantly so, tumor uptake in the 24-hour window group than in the unfractionated one. Differences in tumor sizes were primarily visible during regrowth after therapy, with significantly smaller relative tumor sizes in the 24-hour window group compared to the unfractionated group day 89–95 post inoculation. The median survival for the 24-hour group (71.5 days) was significantly longer than that of the unfractionated group (46 days; p = 0.024). The 6-day group tumor sizes and survival came close to the 24-hour one, but was not significantly better than the unfractionated group. This study demonstrates that fractionation gives therapeutic benefit in an animal model of [177Lu]Lu-PSMA-617 therapy of prostate cancer for tumors in this size range. A shorter 24-hour window outperformed a longer of 6 d between fractions. The outlook for clinical translation will depend on if the mechanism is relevant at conditions, blood ligand concentration etc., that differs between the animal model and human patients.

Prostate cancer (PCa) is a leading malignancy in men, particularly challenging in its advanced stages due to treatment resistance and immune evasion. MicroRNA-1290 (miR-1290) was identified to be implicated in tumor progression, but its role in PCa remains insufficiently characterized. Recent advances in exosome-based delivery systems provide opportunities to target oncogenic miRNAs in vivo. This study aimed to evaluate the therapeutic efficacy and immunomodulatory mechanism of exosome-delivered miR-1290 inhibitor in a PCa mouse model. Exosomes derived from RM-1 cells were loaded with miR-1290 inhibitor and intratumorally administered into TRAMP mice. Tumor volume, body weight, and overall survival were monitored. Safety profiles were evaluated through liver and kidney function tests. Single-cell RNA sequencing (scRNA-seq) and flow cytometry were used to profile intratumoral immune cells, particularly CD8⁺ tissue-resident memory T cells (Trm). Cytokine levels and MAPK signaling activity were assessed, JNK, ERK, and p38 signaling pathways were selectively inhibited to identify immune mechanisms. MiR-1290 expression was elevated in prostate tumor tissues and was significantly suppressed by exosome-delivered miR-1290 inhibitor. Treated mice exhibited reduced tumor growth, improved body weight, and prolonged survival compared with controls, without evident systemic toxicity. scRNA-seq revealed a marked increase of CD8⁺ Trm cells in the prostate tumor tissues of treated mice, with enrichment of inflammatory and immune response pathways, particularly MAPK signaling. The results of the flow cytometry experiment also indicated a marked increase of T cells, CD8 T cells, and CD8 Trm cells in the tumor tissues of miR-1290 inhibitor treated mice. Inhibiting JNK, but not ERK or p38, suppressed IFN-γ and TNF-α production by Trm. Exosome-mediated delivery of a miRNA-1290 inhibitor effectively remodels the prostate tumor microenvironment by enhancing JNK-dependent Trm activation, resulting in efficient and durable antitumor immunity. These findings support miRNA-1290 as a promising therapeutic target and highlight exosome-based RNA therapeutics as a novel strategy for prostate cancer management, warranting further translational development.

Metastatic prostate cancer (PCa), especially when it involves the bone, remains a significant clinical challenge with limited therapeutic options. Our recent research identified Myeloid Differentiation Protein-2 (MD2/LY96) as a potential biomarker associated with poor prognosis and higher metastatic potential in PCa. In this Research Perspective, we build on those findings and present new preclinical data showing that pharmacological inhibition of MD2 markedly reduces tumor growth in a PCa mouse model of bone metastasis. Analysis of patient tumor tissues demonstrated that high MD2 expression is associated not only with metastasis but also with increased infiltration of T regulatory cells (Tregs) and myeloid-derived suppressor cells (MDSCs), indicating a role in promoting an immunosuppressive environment. Additionally, we show that soluble MD2 (sMD2) may serve as a non-invasive biomarker of metastatic burden and help predict resistance to poly ADP-ribose polymerase (PARP) inhibitor therapy.This Research Perspective aims to consolidate mechanistic and preclinical evidence supporting MD2 as a driver of prostate cancer metastasis and to evaluate the therapeutic potential of pharmacological MD2 inhibition in a bone metastasis model.These findings support MD2 as a novel therapeutic target and identify soluble MD2 as a promising predictive and prognostic biomarker in metastatic PCa, with mechanistic links to immune evasion and inflammatory signaling.

Prostate cancer is the most common non-cutaneous cancer in men in the United States. Oxidative stress, induced by chronic prostatic inflammation, impairs normal protective mechanisms in the prostate and increases the risk for cancer progression. We reported that Phellodendron amurense extract (Nexrutine) had similar effects as exercise in reducing highly aggressive tumors in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Here, we examined changes in the transcriptome to understand how these two interventions affect prostate cancer. Twenty-four, 8-10 weeks old male TRAMP mice, were randomized to control, exercise, and Phellodendron amurense extract intervention. At the end of the study, prostate tumors were excised, weighed, and processed for immunohistochemistry and transcriptome analysis. Changes in gene expression (≥ 1.5-fold change, adjusted p < 0.05), gene ontology and pathway analyses were carried out. No significant difference was observed in body or genitourinary weight between groups. There was differential response to interventions with greater percentage of high-grade tumors in the control group. Triglyceride, metabolic processes and localization, transport processes were affected by exercise and Phellodendron amurense extract, respectively. At the transcriptome level, our results suggest that both interventions differentially affect pathways that allow them to overcome high oxidative stress threshold and protect against high-grade tumors.

Prostate cancer (PCa) is a prevalent malignancy with limited treatment options for advanced stages. Oncolytic virotherapy represents a promising immunotherapeutic approach, but its efficacy and underlying mechanisms in PCa, particularly concerning immune checkpoint regulation, remain unclear. The antitumor effects of the oncolytic virus oncolytic herpes simplex virus type 2 (OH2) were evaluated in PCa cell lines and mouse models. Transcriptome sequencing, western blot, chromatin immunoprecipitation-sequencing-quantitative PCR, and flow cytometry were employed to investigate the mechanism of programmed death 1 ligand 1 (PD-L1) regulation. A targeted delivery system, reactive oxygen species (ROS)-responsive aptamer-conjugated anti-prostate-specific membrane antigen (PSMA) extracellular vesicles (RRA-AP-EVs), was engineered from anti-PSMA single chain variable fragment (scFv)-modified extracellular vesicles and an ROS-responsive PD-L1 blocking aptamer. OH2 was loaded via membrane extrusion, and the resulting OH2@RRA-AP-EVs were tested for targeting and therapeutic efficacy following intravenous administration. OH2 effectively killed PCa cells but simultaneously activated the IKK/I-κBα/p65 pathway, leading to PD-L1 upregulation and adaptive immune resistance. While combining OH2 with anti-PD-L1 improved outcomes, clinical translation was hindered by delivery challenges. The novel OH2@RRA-AP-EVs system demonstrated precise tumor targeting and ROS-triggered local PD-L1 blockade. Intravenous injection of OH2@RRA-AP-EVs showed superior tumor control (inhibiting tumor growth by 70% vs free OH2) and enhanced CD8+T cell infiltration and function compared with free OH2 (greater than twofold increase in intratumoral CD8+T cell infiltration along with over twofold upregulation of key effector molecules). This study identifies a mechanism of OH2-induced PD-L1 expression in PCa and provides a versatile, targeted delivery platform that enables effective intravenous viro-immunotherapy, overcoming key translational barriers.

Abstract Introduction High-risk prostate cancer (PCa) with loss of the tumour suppressor gene phosphatase and tensin homolog (PTEN) remains clinically challenging, often progressing despite radiotherapy (RT) and androgen receptor (AR) pathway inhibition. PTEN loss contributes to immune-mediated radioresistance, in part through pro-inflammatory cytokine tumour necrosis alpha (TNF-α)–induced upregulation of cellular inhibitor of apoptosis proteins (cIAP1/2 and XIAP), promoting survival and treatment resistance. This study investigated the efficacy of inhibition of IAPs using tolinapant as a radiosensitiser in PTEN-deficient PCa models and explored its potential synergy with AR inhibition using enzalutamide. We hypothesised that pharmacological inhibition of IAPs would overcome RT resistance in PTEN-deficient PCa and augment apoptotic signalling. Methods Quantitative cell-based assays, immunofluorescence and Western blotting were used to evaluate tolinapant-mediated inhibition of IAP related proteins in PTEN-deficient and wildtype (WT) PCa cell lines both alone and in combination with radiation and enzalutamide, and the impact of these treatments on cell viability, survival and apoptosis. Xenograft mouse models of PTEN-deficient PCa were employed to assess tolinapant’s radio-sensitizing effects in vivo both as a single agent and in combination with RT, whilst ex vivo mechanistic studies focused on apoptotic signalling pathways. Results Tolinapant significantly enhanced the radiosensitivity of PTEN-deficient PCa cells, reducing cell viability and colony formation, with minimal impact in PTEN-WT cells. In xenograft models, tolinapant significantly delayed tumour progression, reduced proliferation (Ki67) expression and increased apoptosis (cleaved caspase-3) compared to RT alone. Ex vivo analyses confirmed on-target IAP suppression and activation of apoptosis pathway. Preliminary in vitro data suggest that adding enzalutamide further enhances radiosensitivity in PCa models, warranting further evaluation. Conclusion Our findings support tolinapant as a radiosensitiser in PTEN-deficient PCa, offering a promising therapeutic pathway for patients with high-risk or castration-resistant disease. By targeting anti-apoptotic signalling, tolinapant may enhance standard-of-care RT and delay disease progression. Ongoing studies aim to define optimal combinatorial strategies for clinical translation. Citation Format: Letitia Mohamed-Smith, Dimitra Kalamida, Suneil Jain, David J. Waugh, Melissa J. LaBonte-Wilson. Tolinapant sensitizes PTEN-deficient prostate cancer to radiotherapy by targeting anti-apoptotic pathways [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr B048.

Abstract MYC overexpression, often associated with chromosome 8q24 amplification, is a well identified genetic alteration in aggressive prostate cancer, especially in metastatic castration-resistant prostate cancer (mCRPC). It has been reported that MYC amplification counteracts with androgen receptor (AR) signaling, which has significant impacts on androgen deprivation therapy efficacy. In this study, we developed a prostate cancer mouse model in which MYC overexpression is initially induced by AR but AR-independent during tumorigenesis and progression. We employed the Multiome technology integrating single-cell RNA-sequencing (scRNA-seq) and ATAC-sequencing (scATAC-seq) to profile late-stage MYC-driven non-metastatic and metastatic prostate cancers. Consistent with previous studies using AR-dependent MYC-driven models, we identified that primary tumors are composed of a large quantity of luminal cells. We have also observed a higher proportion of luminal cells in the tumors that developed metastasis, while localized primary tumors were more abundant in basal cells, and transitional cell types. Interestingly, we uncovered heterogeneous transitional populations featured by different cell cycle profiles and cell-type gene signatures. With gene set enrichment analysis (GSEA), we identified differential enrichment of inflammatory pathways in luminal cells in metastatic primary tumors relative to localized primary tumors. By integrating with scATAC-seq analysis, we also identified new differential transcriptional and epigenetic regulators that may drive the aggressiveness of these MYC-driven cancers in a tissue specific manner. In addition, we applied inferred copy number variation (CNV) analysis and showed that aggressive tumors and metastasis harbor higher levels of CNVs. Together, these findings reveal how MYC overexpression reshapes prostate epithelial lineage, chromatin landscape and genomic instability to promote AR-independent aggressiveness, providing mechanistic insights and a foundation for future therapeutic targeting of MYC-driven malignancies. Citation Format: Kathryn Echandía-Monroe, Sofia Hu, Daniel R. Schmidt, Kun-Lin Ho, Duanduan Ma, Elise G. DeArment, Faith Kim, Chloe Springer, Savannah Washburn, Madeline M. Wong, Kate Lu, Marianna Trakala, William D. Figg, Matthew G. Vander Heiden, Xiaofeng A. Su. Multiomic single-cell profiling of a novel MYC-driven mouse prostate cancer model [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr B017.

How endogenous retroviral elements (ERVs), a family of transposable elements, may promote tumor progression is not well understood. Tripartite motif-containing 28 (TRIM28/TIF1b/KAP1) is a key transcriptional co-repressor protein that represses ERV expression in many cell types including embryonic stem cells, neural progenitor cells, differentiated adult cells, and cancer cells. In this study, we investigated the effect of Trim28 deletion on the expression of ERVs using an immune competent genetically engineered mouse model for prostate cancer. We found Trim28 deletion in prostate tumors led to the expression of ERVs in prostates from both hormonally intact and castrated mice. ERVs can regulate the expression of neighboring genes, and we detected increased expression of several protein-coding genes near overexpressed ERVs. Our data suggest that Trim28 deletion in prostate tumor epithelial cells may promote an innate immune response. However, Trim28 deletion also led to excessive deposition of tumor extracellular matrix (ECM). Our findings suggest that ECM alterations downstream of ERV derepression could affect immune cells in the tumor microenvironment and may promote tumor progression.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13100-025-00382-9.

BackgroundAlthough immunotherapy has revolutionized cancer treatment, its efficacy in castration-resistant prostate cancer (CRPC) remains limited, largely due to an immunologically “cold” tumor microenvironment with scarce T-cell infiltration. Unraveling the molecular mechanisms underlying immune evasion and developing novel strategies to activate innate antitumor immunity are therefore critical to overcoming immunotherapy resistance in CRPC.MethodsUsing bioinformatic approaches, we analyzed the protein kinase membrane-associated tyrosine/threonine 1 (PKMYT1) expression and its correlation with immune cell infiltration and response to immune checkpoint blockade (ICB) in public databases. PKMYT1 protein expression was further evaluated via immunohistochemistry in a clinical cohort of prostate cancer (PCa) specimens. Mechanistic investigations were conducted in PCa cell lines and mouse models. The immunological impact of PKMYT1 inhibition was delineated using single-cell RNA sequencing, and the therapeutic efficacy of RP-6306, either as monotherapy or in combination with programmed death-ligand 1 (PD-L1) blockade, was evaluated in syngeneic mouse models.ResultsPKMYT1 expression was significantly overexpressed in CRPC compared with primary PCa. High PKMYT1 expression correlated with a suppressed antitumor immunity and poor clinical response to ICB. Mechanistically, PKMYT1 inhibition activated the cyclic guanosine monophosphate-adenosine monophosphate adenosine synthase (cGAS)-stimulator of interferon genes (STING) pathway, potentiated both type I and II interferon signaling, and upregulated chemokines, including CCL5 and CXCL10. The selective PKMYT1 inhibitor, RP-6306, enhanced the efficacy of ICB in the presence of CD8+ T cells. Treatment with a PKMYT1 inhibitor alone or in combination with PD-L1 blockade significantly increased the infiltration of activated CD8+ T cells and induced significant tumor suppression in vivo.ConclusionPKMYT1 is a pivotal dual regulator of tumor progression and immune evasion in CRPC. Our findings provide a compelling preclinical rationale for targeting PKMYT1 as a novel strategy to reprogram the tumor immune microenvironment and overcome resistance to immunotherapy.

Cabazitaxel (CTX) is primarily used in the clinical treatment of prostate cancer. The clinical CTX injection (Jevtana®) contains the solubilizer Tween 80, which can lead to serious toxic side effects during intravenous injection. This study developed a novel nanodelivery system for encapsulating CTX, eliminating the need for Tween 80 and addressing current clinical challenges associated with CTX use. The nanodelivery system uses the hydrophilic polymer polyvinylpyrrolidone K12 (PVP K12) as a dispersing agent and a small amount of highly biocompatible sodium cholesteryl sulfate (SCS) as a stabilizer, forming a cabazitaxel nanodispersion (CTX-NP) through the water dispersion method. The CTX-NP exhibited a spherical shape, uniform distribution, a particle size of 128.90 ± 0.42nm, a PDI of 0.14 ± 0.01, a zeta potential of -65.88 ± 1.23mV, and a drug encapsulation efficiency of 97.58 ± 0.58%. Furthermore, hemolysis, vascular irritation, and maximum tolerated dose (MTD) experiments indicated that CTX-NP has good biocompatibility compared to cabazitaxel-Tween injection (CTX-TW). The pharmacokinetic studies in rats revealed that, compared to CTX-TW, CTX-NP had an extended half-life (T1/2), mean residence time (MRT), and a larger area under the drug concentration-time curve (AUC). In the RM-1 prostate cancer mouse model, compared with CTX-TW, the high-dose CTX-NP group showed better tumor inhibition with an inhibition rate of 79.48%, indicating that CTX-NP could achieve superior anti-tumor effects by increasing the administered dose.

Enhanced Antitumor Efficacy of 225Ac-NM600 Compared to 177Lu-NM600 in Murine Prostate Cancer Models

Prostate cancer remains one of the most prevalent solid tumors in men worldwide and poses a major therapeutic challenge due to its immunologically “cold” tumor microenvironment (TME), which is characterized by low T cell infiltration, limited antigen presentation, and high levels of immunosuppressive factors. While chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of hematologic malignancies, it has yielded limited success in solid tumors such as prostate cancer. Macrophage-based CAR (CAR-M) therapies have emerged as promising alternatives, owing to macrophages’ natural tumor-infiltrating capacity, phagocytic activity, and ability to modulate the TME. However, conventional CAR-Ms exhibit limited capacity to prime adaptive immunity due to insufficient co-stimulatory signaling. To address this limitation, we engineered two novel NKG2D-targeted CAR constructs for macrophages: one containing the intracellular Fc receptor common γ chain (FcRγ) alone (CAR-M), and another incorporating both FcRγ and the intracellular domain of the co-stimulatory molecule CD86 (CD86-CAR-M). These constructs were expressed in Raw264.7 macrophages or and evaluated for antigen-specific phagocytosis, tumor cell cytotoxicity, cytokine secretion, and T cell activation in vitro. In vivo efficacy and safety were assessed using both xenograft and syngeneic mouse models of prostate cancer, including combination therapy with anti-PD-L1 checkpoint blockade. Both CAR-M and CD86-CAR-M exhibited robust, antigen-specific phagocytosis and cytotoxicity against NKG2D ligand-expressing prostate cancer cells in vitro. CD86-CAR-Ms demonstrated enhanced M1 polarization, higher expression of CD86 and superior activation of cytotoxic T lymphocytes, accompanied by increased secretion of IFN-γ and TNF-α. This interaction triggers the phosphorylation of ERK, a central mediator of M1 macrophage polarization and inflammatory responses. In vivo, CD86-CAR-Ms achieved greater tumor suppression and survival benefit than CAR-Ms in immunocompetent models and significantly enhanced the efficacy of anti-PD-L1 antibody therapy without systemic toxicity. The improved anti-tumor effect was associated with increased T cell, NK cell infiltration and macrophages MHC-II expression, indicating TME reprogramming from cold to hot one. This study presents the first demonstration of CD86-enhanced CAR-macrophages targeting NKG2D ligands in prostate cancer. By integrating innate and adaptive immune activation, CD86-CAR-Ms represent a novel and potent strategy for overcoming immunosuppression and improving the therapeutic efficacy of immune checkpoint inhibitors in solid tumors.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12964-025-02548-7.

Basal-like (also known as double-negative) prostate cancers are aggressive tumors that lack effective targeted therapies. We aimed to delineate the role of CDH3 (P-cadherin) in basal-like prostate cancer and evaluate CDH3-directed therapeutic strategies. We integrated genetically engineered mouse models (GEMMs) of prostate cancer, bulk and single-cell transcriptomic analyses, and a suite of in vitro and in vivo experiments. CDH3 expression and associated signaling pathways were examined in Pten/Apc double-knockout mouse prostates and human datasets. Functional studies included antibody-drug conjugate (ADC) cytotoxicity assays and the development of chimeric antigen receptor (CAR) T cells targeting CDH3, tested in prostate cancer cell lines and xenograft models. Pten/Apc double deletion in prostate GEMMs led to highly aggressive tumors with markedly elevated CDH3 expression and enrichment of non-canonical WNT signaling components. Transcriptomic analyses of patient-derived prostate tumors confirmed that CDH3 is significantly upregulated in basal-like prostate cancer subtypes relative to luminal subtypes. Single-cell RNA sequencing revealed CDH3 expression predominantly in basal epithelial cells. Mechanistically, we found that active YAP1 signaling and a WNT5A-ROR2 non-canonical WNT axis drive CDH3 expression. Targeting CDH3 with a CDH3-specific ADC induced potent, antigen-dependent killing of CDH3⁺ prostate cancer cells in vitro and significantly suppressed tumor growth in in vivo metastatic prostate cancer models. Likewise, CDH3-targeted CAR T cells specifically recognized and lysed CDH3-expressing prostate tumor cells while sparing CDH3-negative cells, leading to tumor regression and improved survival in mouse models, especially when combined with PD-1 checkpoint blockade. CDH3 is a key marker and functional driver of basal-like prostate cancer. Therapeutic strategies leveraging CDH3, including ADCs and CAR T cells, demonstrate strong preclinical efficacy, supporting the development of CDH3-targeted treatments to overcome resistance in aggressive prostate cancer.

Prostate cancer (PCa) exhibits low sensitivity to immune checkpoint inhibitors due to insufficient T cell infiltration and the dominance of immunosuppressive cells in the tumor immune microenvironment (TIME). Immunotherapy-based combination therapy proves to be an effective strategy in overcoming immune resistance. However, the development and optimization of such therapies necessitate an accurate preclinical model capable of replicating the complex TIME of PCa. To address this need, we developed a humanized mouse model that closely mimics the TIME of PCa patients. This model was created by transplanting human peripheral blood mononuclear cells (PBMCs) into severe combined immunodeficient mice. We systematically investigated factors influencing immune reconstitution, including donor variability, cell dosage, and recipient characteristics. Furthermore, the model was employed to establish a human PCa xenograft, which enabled us to assess the therapeutic efficacy and explore the underlying mechanisms of the combination therapy involving docetaxel and pembrolizumab. The results revealed that both the donor origin and the quantity of transplanted PBMCs had a significant impact on immune reconstitution. In our preclinical evaluations, the combination therapy of docetaxel with immunotherapy showed superior efficacy in both cell line-derived and patient-derived xenograft models when compared to monotherapy approaches. This enhanced efficacy is attributed to the increased infiltration of CD8+ T cells within the TIME. Our study successfully establishes a reliable humanized mouse model for PCa. The promising outcomes of the combination therapy observed in this model could potentially lay the groundwork for innovative clinical applications designed to overcome immune resistance in PCa.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00262-025-04225-7.

SummaryTargeting anti-apoptotic BCL2 family proteins is an attractive therapeutic strategy to drive prostate cancer (PCa) cell death. Here, we show that MCL1 is highly expressed in castration-resistant PCa, associating with worse clinical outcome. We demonstrate that targeting MCL1 with BH3 mimetics triggers apoptotic cell death in a subset of PCa cell line models. Furthermore, siRNA targeting of UCHL3, a deubiquitinating enzyme, downregulates MCL1 expression to synergize with BCLXL blockade; however, its impact on MCL1 is driven through an off-target effect, raising an important methodological consideration when studying MCL1 biology. Finally, we demonstrate that co-targeting MCL1 and BCLXL in patient-derived and mouse PCa models drives apoptotic PCa cell death. Taken together, targeting the intrinsic apoptosis pathway remains an attractive therapeutic strategy for lethal PCa. Future studies should focus on identifying strategies and technologies that can deliver cancer specific kill, to improve the outcome for men with this lethal disease.