PCa cells exhibit dependency on exogenous glutamine, a phenomenon termed glutamine addiction that distinguishes malignant metabolism from normal prostate physiology. This metabolic vulnerability arises from the unique bioenergetic and biosynthetic demands of proliferating tumor cells, which require glutamine not only as a nitrogen donor for nucleotide and amino acid synthesis but also as a carbon source for tricarboxylic acid cycle anaplerosis. PCa cell lines PC-3, DU145 and LNCaP display distinct bioenergetic properties, with mitochondrial adaptations that render them sensitive to glutamine deprivation (16). Targeting alanine-serine-cysteine transporter 2 (ASCT2)-mediated glutamine uptake effectively blocks PCa growth and tumor development, establishing glutamine dependency as a potential therapeutic target (17).

Plasma glutamine levels may serve as prognostic biomarkers in localized PCa, with alterations in circulating glutamine associated with disease outcomes (18). The degree of glutamine dependency varies across disease states: CRPCa cells exhibit heightened reliance on glutamine metabolism compared with hormone-naïve (untreated by androgen deprivation therapy) counterparts, suggesting that therapeutic pressure selects for metabolic adaptations that amplify glutamine addiction (19). This evolutionary trajectory positions glutamine metabolism as a key driver of lethal PCa phenotypes, providing a rationale for developing therapeutic strategies that exploit this dependency across the spectrum of disease progression.

The execution of glutamine-dependent metabolic programs requires coordinated action of specialized transporters that mediate glutamine influx and efflux. Among glutamine transporters, ASCT2 (encoded by SLC1A5) is the dominant mediator of glutamine uptake in PCa cells, with elevated expression demonstrated across multiple model systems and clinical specimens (17,20). Mechanistic studies have revealed that ASCT2 expression is directly regulated by multiple oncogenic signaling pathways, positioning this transporter as a nodal point integrating proliferative signals (20,21). The functional importance of ASCT2 is further supported by observations that CRPCa cells exhibit increased ASCT2 expression and glutamine uptake, linking transporter upregulation to therapeutic resistance (21). Beyond ASCT2, the heterodimeric amino acid transporter L-type amino acid transporter 1 (encoded by SLC7A5) participates in glutamine exchange by coupling glutamine efflux with essential amino acid import, which sustains mTOR signaling and protein synthesis (11).

Once internalized, intracellular enzymes channel glutamine into downstream metabolic pathways. Glutamine enters mitochondria where glutaminase (GLS) catalyzes its deamination to glutamate, representing the first committed step of glutaminolysis (22,23). Elevated GLS expression confers enhanced glucose use capacity in PCa cells, linking glutamine catabolism with broader metabolic reprogramming (22). Pharmacological inhibition of GLS suppresses proliferation and promotes apoptosis in PCa models, validating this enzyme as a druggable vulnerability (23,24). The existence of two GLS isoforms, GLS and GLS2, adds regulatory complexity; an isoform switch from GLS to GLS2 is implicated in therapeutic resistance and disease progression, indicating that isoform-specific targeting strategies may be required for optimal efficacy (25). Glutamate dehydrogenase (GLUD) converts glutamate to α-ketoglutarate, feeding carbon into the tricarboxylic acid cycle while releasing ammonium as a byproduct. The coordinated upregulation of these transporters and enzymes establishes a metabolic axis that sustains PCa cell survival and proliferation (26).

Glutamine metabolism in PCa integrates signals from dominant oncogenic pathways that orchestrate metabolic reprogramming in response to extracellular cues and therapeutic pressures. The androgen receptor (AR) pathway, central to PCa biology throughout disease evolution, exerts control over glutamine metabolism. Differential regulation of metabolic pathways by full-length AR vs. its constitutively active splice variant AR-V7 reveals that androgen signaling directs glutamine use patterns, with AR-V7-expressing cells exhibiting distinct metabolic dependency (27). Glutaminolysis itself is regulated by 5α-dihydrotestosterone, establishing direct hormonal control over this key metabolic route (28). The AR coactivator steroid receptor coactivator-2 coordinates metabolic reprogramming that supports PCa survival and metastasis, linking transcriptional coactivation with glutamine-dependent phenotypes (29).

Myc and the PTEN/PI3K/AKT/mTOR pathway further amplify glutamine use through complementary mechanisms. Myc drives glutamine metabolism through transcriptional activation of GLS and suppression of negative regulators; a long non-coding RNA connects c-Myc to tumor metabolism, illustrating the layered regulatory architecture controlling glutamine use (30). c-Myc-driven glycolysis via thioredoxin-interacting protein suppression depends on the GLS-MLX-interacting protein) axis, revealing crosstalk between glucose and glutamine metabolic programs (31). PTEN loss, typically observed in PCa, induces metabolic reprogramming characterized by enhanced glutamine dependency, linking tumor suppressor inactivation with acquired metabolic vulnerability (32). AKT inhibitors elicit metabolic responses detectable by hyperpolarized magnetic resonance spectroscopy, providing tools to monitor pathway engagement (33). The mTOR pathway, serving as a nutrient sensor, integrates amino acid availability with growth signaling; dual mTOR inhibition alters tumor heterogeneity and metabolic profiles in patient-derived xenografts (34). p53 status modulates glutamine metabolism through transcriptional programs that influence mitochondrial function and redox balance. Knockdown of the cochaperone small glutamine-rich tetratricopeptide repeat-containing protein α suppresses both androgen and PI3K/Akt signaling while inhibiting proliferation, illustrating the interconnectedness of these pathways (35). The convergence of these oncogenic signals on glutamine metabolism genes establishes a complex regulatory network that adapts to therapeutic intervention and disease progression (36).

Once imported and processed through the glutaminolysis pathway, glutamine-derived carbon is distributed among multiple metabolic fates that support PCa cell survival and proliferation. The most common fate of glutamine carbon is anaplerotic entry into the tricarboxylic acid cycle via conversion to α-ketoglutarate, replenishing intermediates extracted for biosynthetic purposes (37,38). This anaplerotic function is key under conditions of metabolic stress; metformin treatment decreases glucose oxidation and increases the dependency of PCa cells on reductive glutamine metabolism, demonstrating metabolic flexibility that sustains tricarboxylic acid cycle function under pharmacological pressure (37). Pyruvate dehydrogenase E1 subunit α1 knockout in PCa cells results in metabolic reprogramming toward greater glutamine dependence, emphasizing the compensatory association between glucose and glutamine carbon sources (38).

Beyond energy metabolism, glutamine serves as the primary precursor for glutathione synthesis, providing the building blocks required for this notable cellular antioxidant. Glutamine-derived glutathione metabolism is key for survival under chronic cycling hypoxia, where fluctuating oxygen levels generate oxidative stress that must be neutralized to prevent cell death (39). In enzalutamide-resistant PCa, antioxidant programs including glutathione metabolism serve critical roles in sustaining viability under therapeutic pressure (24). The glutamine antagonist JHU083 exerts antitumor effects partly through glutathione depletion, linking pharmacological glutamine interference with redox disruption (40). Glutamine nitrogen supports nucleotide biosynthesis through multiple routes: Amide nitrogen contributes directly to purine and pyrimidine ring synthesis, while amine nitrogen provides nitrogen for non-essential amino acids that feed into nucleotide production. Inhibition of guanosine monophosphate synthetase, which uses glutamine amide nitrogen, blocks glutamine metabolism and PCa growth, validating nucleotide synthesis as a key downstream effector (41).

Glutamine-derived α-ketoglutarate serves as a substrate for epigenetic modifying enzymes including Jumonji C domain-containing histone demethylases and ten-eleven translocation DNA hydroxylases. By modulating the activity of these α-ketoglutarate-dependent dioxygenases, glutamine availability influences histone methylation status and DNA hydroxymethylation patterns, establishing a direct link between nutrient availability and epigenetic regulation (13,42). This metabolic-epigenetic axis allows fluctuations in glutamine supply to translate into heritable changes in gene expression programs that may contribute to phenotypic plasticity and therapy resistance (13,42). The partitioning of glutamine among these competing fates is dynamically regulated in response to microenvironmental conditions and therapeutic interventions, creating metabolic vulnerability that can be exploited for therapeutic benefit (43).

The regulation of glutamine metabolism in PCa is not governed by individual oncogenic pathways acting in isolation, but rather through a network of cross-regulatory interactions between AR/AR-V7, Myc and PI3K/AKT/mTOR signaling. These pathways converge on common downstream effectors while simultaneously modulating their activity, creating a highly integrated and adaptive regulatory system. A key distinction exists between full-length AR and its constitutively active splice variant AR-V7 in regulating glutamine metabolism (30,31). While AR activation increases citrate levels, AR-V7 reduces citrate due to enhanced use rather than impaired synthesis, mirroring the metabolic shifts observed in patients with CRPCa (7). Furthermore, flux assays have demonstrated that compared with AR, AR-V7 exhibits increased dependence on glutaminolysis and reductive carboxylation to generate tricarboxylic acid cycle intermediates, establishing AR-V7 as a driver of distinct metabolic vulnerabilities (7). The activity of AR-V7 is regulated by FOXO1 in a PTEN-PI3K-AKT-dependent manner, positioning AR-V7 as both a downstream effector and a proximal node integrating PI3K/AKT signaling with glutamine metabolic reprogramming (11). AR and Myc exhibit reciprocal regulation that amplifies glutamine metabolic reprogramming. AR directly transactivates Myc expression, and Myc enhances AR transcriptional activity through multiple mechanisms, establishing a positive feed-forward loop that drives GLS expression and glutamine uptake (30,31). This AR-Myc axis is further reinforced by long non-coding RNAs that connect c-Myc to tumor metabolism (30). Concurrently, AR signaling intersects with the PI3K/AKT/mTOR pathway at multiple levels. PTEN loss, which activates PI3K/AKT signaling, enhances AR transcriptional activity and promotes glutamine dependency (32). AKT phosphorylation of AR modulates its stability and transcriptional output, while mTOR activation integrates amino acid availability with AR-dependent metabolic programs (34). Regarding the Myc/PI3K/AKT/mTOR interaction, emerging evidence indicates that mTORC1 positively regulates GLS and glutamine flux through ribosomal protein S6 kinase β-1 (S6K1)-dependent control of c-Myc translation, wherein S6K1 enhances Myc translation efficiency by modulating eukaryotic initiation factor 4B phosphorylation (12). The role of Myc in regulating glutamine transporter expression is context-dependent and influenced by PTEN/PI3K status: Myc is unable to upregulate the glutamine transporters SLC1A4 and SLC1A5 in PTEN wild-type cells, whereas this regulation is enabled by PTEN loss (9,16). mTORC1, in contrast, is required for maximal AR-mediated glutamine transporter expression and cell proliferation independent of PTEN status (9). The convergence of these pathways on common transcriptional targets, including GLS and glutamine transporters such as ASCT2, creates a regulatory hub wherein pathway activation at any node sustains glutamine metabolism when other nodes are inhibited (20,36). This network redundancy explains the limited efficacy of single-pathway inhibitors and provides the rationale for combinatorial strategies targeting multiple nodes simultaneously. The adaptive plasticity of this regulatory network enables PCa cells to maintain glutamine addiction under therapeutic pressure, contributing to the evolution of CR phenotypes (19,25).

Ammonium within the prostate TME originates from multiple metabolic sources that reflect the heightened catabolic activity of malignant cells. The predominant source is glutaminolysis, wherein GLS catalyzes the deamination of glutamine to glutamate, releasing ammonium as a stoichiometric byproduct. This pathway operates at elevated flux in PCa cells due to glutamine addiction, resulting in constitutive ammonium production that surpasses the rate at which the cells use nitrogen for amino acid and nucleotide biosynthesis, causing ammonium to accumulate and be released into the TME (38).

Beyond glutaminolysis, deamination reactions involving other amino acids contribute to the ammonium pool. Catabolism of serine, threonine and branched-chain amino acids generates ammonium through the action of serine dehydratase, threonine dehydratase and branched-chain amino acid transaminases coupled with GLUD (10,11). Nucleotide catabolism represents an additional source, with adenosine and AMP deaminase releasing ammonium during purine nucleotide degradation (12,13). The relative contribution of each source varies according to metabolic context, nutrient availability and oncogenic driver status. Ye et al (12) reviewed ammonium metabolism rewiring in the PCa ME, emphasizing that the convergence of these pathways creates sustained ammonium flux that distinguishes malignant from benign prostate tissue.

Once generated, ammonium faces several potential fates determined by the expression and activity of nitrogen-handling enzymes within PCa cells. The urea cycle represents the canonical pathway for ammonium detoxification, converting ammonium and bicarbonate to urea through enzymatic reactions distributed between mitochondria and cytoplasm. However, PCa cells exhibit notable urea cycle dysregulation characterized by downregulation of key enzymes including carbamoyl phosphate synthetase I and ornithine transcarbamylase. Bruzzone et al (44) demonstrated using nuclear magnetic resonance-based urine metabolomics that patients with PCa display enhanced carbon and nitrogen recycling, with metabolomic signatures indicating redirection of nitrogen away from urea production toward anabolic pathways. This metabolic rewiring favors nitrogen incorporation into amino acids and nucleotides at the expense of ureagenesis, supporting biosynthetic demands of proliferating tumor cells.

GLUD and glutamine synthetase (GLUL) represent alternative fates for ammonium assimilation. GLUD catalyzes the reversible reductive amination of α-ketoglutarate to glutamate, incorporating ammonium into amino acid pools, while GLUL ligates ammonium with glutamate to form glutamine, recycling nitrogen back into the glutamine pool. Luo et al (45) revealed that PCa stem cells exhibit aberrant urea cycle activity with selective upregulation of specific urea cycle enzymes that support stemness maintenance, suggesting that nitrogen partitioning is dynamically regulated across tumor subpopulations. Labroy et al (46) further demonstrated metabolic crosstalk between the urea cycle and pyrimidine synthesis, identifying dihydroorotate dehydrogenase (DHODH) as a metabolic vulnerability that integrates nitrogen metabolism with nucleotide biosynthesis.

Beyond its role as a metabolic substrate, ammonium serves as an intracellular signaling molecule that modulates key cell processes including pH homeostasis, autophagy and stress adaptation. Ammonium exists in equilibrium with ammonia, which freely diffuses across membranes and accepts protons to form ammonium, thereby serving as a mobile pH buffer. Chatterjee et al (47) demonstrated that membrane AR signaling influences Na+/H+ exchanger activity in PCa cells, establishing a link between hormonal signaling and pH regulatory mechanisms that interface with ammonium partitioning.

Accumulation of intracellular ammonium alkalinizes acidic compartments including lysosomes, disrupting the proton gradient required for optimal lysosomal hydrolase activity and autophagic flux. Yang et al (48) reported that curcumin induces both apoptosis and protective autophagy in CRPCa cells through mechanisms involving iron chelation, highlighting the interconnectedness of metal homeostasis, oxidative stress and autophagic regulation. Ammonium accumulation influences stress adaptation pathways by modulating mTOR signaling and activating stress-responsive transcription factors. Chen et al (49) developed an ammonia-induced calcium phosphate nanostructure that provides insight into how local ammonium concentrations may influence bone metastasis, linking nitrogen metabolism with the establishment of metastatic niches. These signaling functions establish ammonium as a pleiotropic mediator that integrates metabolic state with cell stress responses.

Ammonium accumulation within the prostate TME exerts paradoxical effects, simultaneously supporting tumor metabolic adaptation while suppressing antitumor immune responses. For cancer cells, ammonium serves as a nitrogen reservoir that can be assimilated into amino acids and nucleotides via GLUD and GLUL, supporting biosynthetic capacity under nutrient-limited conditions. Metabolomic profiling by Yu et al (50) identified distinct metabolic signatures in plasma and urine from patients with PCa, revealing alterations in nitrogenous compounds that reflect systemic metabolic reprogramming.

However, the ammonium accumulation that supports tumor metabolism imposes immunosuppressive consequences on infiltrating immune cells. Ye et al (12) reviewed how ammonium metabolic reprogramming drives immunosuppression within the prostate TME through multiple mechanisms including polarization of tumor-associated macrophages (TAMs) toward the M2 phenotype, induction of T cell dysfunction and promotion of myeloid-derived suppressor cell (MDSC) accumulation; direct primary evidence for ammonium-induced T cell dysfunction has been reported in colorectal cancer and effector T cell models (51,52). Ammonium impairs T cell proliferation and effector function by interfering with T cell receptor signaling and inducing metabolic stress, while simultaneously promoting macrophage arginase activity and anti-inflammatory cytokine production. The dual nature of ammonium accumulation creates a therapeutic paradox: Interventions that block ammonium production may deprive tumors of nitrogen for biosynthesis, but interventions that promote ammonium accumulation may reinforce immunosuppression. Understanding this duality is key for developing therapeutic strategies that target nitrogen metabolism without compromising antitumor immunity, positioning ammonium metabolism as a key node connecting tumor biology with immune evasion in PCa (51,52).

The prostate TME is characterized by metabolic alterations that create a hostile landscape for infiltrating immune cells while supporting tumor growth. Hypoxia is a dominant feature, arising from aberrant vascularization and elevated oxygen consumption by proliferating tumor cells. Bharti et al (53) demonstrated distinct hypoxia patterns in primary and metastatic PCa environments, revealing that oxygen gradients shape regional metabolic heterogeneity and influence therapeutic responses. Arocena et al (54) developed a variant of coverslip hypoxia to visualize tumor cell alterations at increasing distances from an oxygen source, providing mechanistic insight into how oxygen tension gradients drive metabolic adaptation. Bery et al (55) demonstrated that hypoxia promotes PCa aggressiveness by upregulating epithelial-mesenchymal transition activator zinc finger E-box binding homeobox 1 and potassium channel expression, linking oxygen deprivation with enhanced metastatic potential.

Lactate accumulation is a defining feature of the PCa TME, resulting from elevated glycolytic flux and the Warburg effect in cancer cells. Bok et al (56) used dual-agent hyperpolarized carbon-13 magnetic resonance spectroscopic imaging to reveal the role of lactate metabolism in PCa progression and metastases, demonstrating that lactate serves not only as a waste product but as a critical metabolic fuel and signaling molecule. Comito et al (57) demonstrated that lactate modulates CD4⁺ T cell polarization and induces an immunosuppressive environment through the TLR8/microRNA21 pathway, sustaining prostate carcinoma progression. Chetta et al (58) recently reviewed the clinical implications of lactate as a key metabolite in PCa progression, emphasizing its multifaceted roles in promoting angiogenesis, suppressing antitumor immunity and driving therapy resistance. The convergence of hypoxia, nutrient competition and lactate accumulation establishes a metabolic milieu that influences immune cell function and polarization.

TAMs represent the most abundant immune population within the prostate TME and exhibit metabolic plasticity that enables adaptation to microenvironmental cues. El-Kenawi et al (59) demonstrated that acidity promotes tumor progression by altering macrophage phenotype in PCa, establishing a direct link between extracellular pH and TAM polarization toward immunosuppressive states. Banerjee et al (60) examined differential expression of efferocytosis- and phagocytosis-associated genes in TAMs exposed to patient-derived PCa ME, revealing context-dependent transcriptional programs that shape macrophage function. Han et al (61) demonstrated that IL-6 produced by prostate epithelial cells stimulated with Trichomonas vaginalis promotes proliferation of PCa cells by inducing M2 polarization of human monocytic leukemia cell line THP-1-derived macrophages, highlighting the role of infectious agents in shaping TAM phenotypes.

Glutamine metabolism serves a key role in driving TAM polarization and function. Praharaj et al (14) demonstrated that metabolic reprogramming of TAMs using the glutamine antagonist JHU083 drives tumor immunity in myeloid-rich PCa and bladder cancer: JHU083 treatment reprogrammed immunosuppressive TAMs toward a pro-inflammatory phenotype, increasing tumor cell phagocytosis, diminishing pro-angiogenic capacity and promoting inflammatory signaling. Masetti et al (62) identified lipid-loaded TAMs as key sustainers of tumor growth and invasiveness in PCa, revealing that metabolic substrate availability shapes macrophage effector functions. Li et al (63) demonstrated that dauricine regulates PCa progression by inhibiting PI3K/AKT-dependent M2 polarization of macrophages, providing pharmacological evidence for targeting macrophage metabolism. The metabolic plasticity of TAMs represents both a vulnerability and a therapeutic opportunity in PCa.

T cells infiltrating the prostate TME face metabolic challenges that compromise their antitumor effector function and promote exhaustion. Nutrient competition between rapidly proliferating cancer and T cells creates an environment of glutamine deprivation that impairs T cell activation and proliferation. Guan et al (64) demonstrated that AR activity in T cells limits checkpoint blockade efficacy, revealing that hormonal signaling directly influences T cell metabolism and function within the prostate TME. Chang et al (65) recently demonstrated that 1-pyrroline-5-carboxylate inhibits T cell glycolysis in the PCa microenvironment through the Src homology region 2 domain-containing phosphatase 1/pyruvate kinase M2/lactate dehydrogenase B pathway, identifying a novel metabolite-driven immunosuppressive mechanism.

Memory T cell differentiation and maintenance are influenced by the metabolic landscape. Rastogi and McNeel (66) characterized prostate tumor immune ME changes following immunotherapy, revealing shared features between patients who developed antitumor responses and those experiencing immune-associated adverse events. Zhou et al (67) demonstrated that upregulation of E-prostanoid receptor 4 attenuates the killing ability of CD8⁺ T cells against PCa cells via the PI3K/AKT signaling pathway, identifying a potential target for restoring T cell cytotoxicity. The metabolic competition between tumors and T cells for glutamine and other nutrients shapes the outcome of antitumor immune responses. Molina et al (68) demonstrated that regulatory and memory T lymphocytes infiltrating prostate tumors predict long-term clinical outcomes, emphasizing the prognostic value of T cell subset distribution.

MDSCs and DCs represent complementary arms of the myeloid compartment that orchestrate immunosuppression within the prostate TME. MDSCs expand in patients with PCa and suppress T cell responses through multiple mechanisms including arginase-1 expression, reactive oxygen species production and nutrient depletion. Hellsten et al (69) demonstrated the STAT3 inhibitor galiellalactone inhibits the generation of MDSC-like monocytes by PCa cells and decreases immunosuppressive and tumorigenic factors, validating MDSC targeting as a therapeutic strategy. Fu et al (70) examined the role of MDSCs in high-dose-irradiated transgenic adenocarcinoma of the mouse prostate cell line c1 tumors, identifying them as both a therapeutic target and an index for assessing TME status. Koinis et al (71) reviewed MDSCs in PCa, emphasizing their key role in immune evasion. Siemińska and Baran (72) further positioned MDSCs as key players and promising therapy targets in PCa, reviewing strategies for MDSC depletion and functional inhibition.

DCs, key for priming antitumor T cell responses, exhibit metabolic and functional alterations within the prostate TME. Feriz et al (73) used single-cell RNA sequencing to demonstrate heterogeneous transcriptional signatures in tumor-infiltrating DCs in PCa, revealing distinct DC subsets with differential immunostimulatory capacities. Hawlina et al (74) demonstrated that DC-based vaccines prolong survival and time to next therapy independently of vaccine cell number, providing clinical evidence for DC-based immunotherapy. Hensler et al (75) identified peripheral gene signatures that distinguish distinct immunotypes of patients with cancer with therapeutic implications for autologous DC-based vaccines, offering biomarkers for patient selection. The metabolic adaptation of MDSCs and DCs to the glutamine-depleted, ammonium-accumulating prostate TME shapes their immunosuppressive vs. immunostimulatory functions. Li et al (76) demonstrated that AT-rich interactive domain-containing protein 1A loss induces polymorphonuclear MDSC chemotaxis and promotes PCa progression, revealing genetic determinants of myeloid cell recruitment. The immunosuppressive effects of MDSCs and DCs, coupled with their metabolic reprogramming, establishes a-barrier to antitumor immunity that must be overcome for successful immunotherapy.

PCa cells actively remodel the metabolic landscape of the TME through secretion of metabolites, enzymes and extracellular vesicles that directly modulate immune cell function. Lactate, long considered a metabolic waste product, has emerged as a potent signaling molecule that reprograms immune cell metabolism and polarization (77). Stepka et al (77) reviewed metabolic and amino acid alterations in the TME, emphasizing that lactate accumulation suppresses T cell proliferation and promotes regulatory T cell differentiation while driving macrophage polarization toward immunosuppressive M2 phenotypes.

Extracellular vesicles represent an additional mechanism for metabolic communication between tumor cells and immune populations. Mo et al (78) demonstrated that long non-coding RNA nuclear-enriched abundant transcript 1 shuttled by PCa cell-secreted exosomes initiates osteoblastic phenotypes in the bone metastatic ME through the microRNA-205-5p/runt-related transcription factor 2/splicing factor proline- and glutamine-rich pathway, revealing that exosomal cargo shapes distant ME niches. Lee et al (79) demonstrated that extracellular vesicles derived from PCa cells induce metabolic reprogramming toward a glycolysis phenotype in recipient cells, suggesting vesicle-mediated transfer of metabolic regulators contributes to the establishment of a glycolytic, immunosuppressive ME. Ippolito et al (80) showed that extracellular pH modulates neuroendocrine PCa cell metabolism and susceptibility to mitochondrial inhibitors, indicating that the acidic ME resulting from tumor metabolism further influences immune cell function. These tumor-derived signals establish a metabolic landscape that favors immunosuppression while supporting tumor progression.

Glutamine is a key nutrient for both proliferating tumor cells and activated lymphocytes, creating a metabolic competition within the prostate TME that shapes antitumor immunity. Alhallaq and Sultan (9) positioned glutamine and glutamate metabolic reprogramming at the center of PCa pathogenesis, describing the dynamic competition between tumor and immune cells for this essential amino acid. This competition deprives infiltrating T cells of the glutamine required for activation, proliferation and effector function, contributing to the exhausted T cell phenotype characteristic of advanced PCa. Matos et al (81) examined the role of arginine and arginases in modulating metabolism, TME and PCa progression, demonstrating that competition for amino acid substrates extends beyond glutamine to encompass multiple nitrogenous nutrients.

Bhowmick et al (10) reviewed strategies for targeting glutamine metabolism in PCa, emphasizing that therapeutic interventions should consider the differential glutamine requirements of tumor cells vs. antitumor immune populations. This dual benefit arises from differential sensitivity to glutamine antagonism, with tumor-associated macrophages being susceptible to metabolic reprogramming toward pro-inflammatory phenotypes.

Beyond its role as a nitrogenous waste product, ammonium serves as an active immunosuppressive metabolite that directly impairs T cell function and promotes macrophage polarization toward tumor-supportive phenotypes. Ye et al (12) reviewed ammonium metabolism rewiring in the PCa ME, demonstrating that ammonium accumulation drives immunosuppression through multiple mechanisms including polarization of TAMs toward the M2 phenotype, induction of T cell dysfunction and promotion of MDSC accumulation. Primary studies have shown that ammonia directly impairs T cell proliferation and effector function through lysosomal alkalization, mitochondrial swelling and impaired autophagic flux (51,52): Ammonium impairs T cell proliferation and effector function by interfering with T cell receptor signaling and inducing metabolic stress, while simultaneously promoting macrophage arginase activity and anti-inflammatory cytokine production. Elia et al (13) demonstrated that nitrogen handling varies between tumor types, with PCa exhibiting unique adaptations that favor ammonium accumulation and recycling. Yang et al (82) reviewed TME-driven drug resistance in urological cancers, highlighting that ammonium-mediated immunosuppression contributes to the failure of immunotherapeutic approaches and represents a potential therapeutic target. The immunosuppressive consequences of ammonium accumulation create a therapeutic paradox: Interventions that block ammonium production may deprive tumors of nitrogen for biosynthesis, but interventions that promote ammonium accumulation may reinforce immunosuppression. This duality positions ammonium metabolism as a key node connecting tumor biology with immune evasion in PCa.

Glutathione metabolism represents a key intersection where tumor antioxidant defense mechanisms directly influence immune cell function within the prostate microenvironment. Wang et al (83) reviewed the integrated regulation of ferroptosis in PCa, demonstrating that glutathione peroxidase 4 and glutathione metabolism protect tumor cells from oxidative stress while simultaneously depleting the antioxidant capacity available to infiltrating immune cells. Linares et al (84) demonstrated that activating transcription factor 4-induced metabolic reprogramming represents a synthetic vulnerability of p62-deficient tumor stroma, revealing that oxidative stress responses in the TME are coordinately regulated and influence both cancer cells and supporting stromal elements. Zhang et al (15) showed that improved antitumor activity against PCa can be achieved through combined targeting of Myc and GFAT-1, the rate-limiting enzyme in the hexosamine biosynthetic pathway that branches from glutamine metabolism and influences protein glycosylation and redox balance. The glutathione synthesis pathway directly competes with other glutamine-using pathways for substrate, creating metabolic trade-offs that influence both tumor survival and immune function. Tumor cells with elevated glutathione synthesis capacity exhibit enhanced resistance to oxidative stress induced by inflammatory cytokines, while depleting the local cysteine and glutamate pools required for optimal T cell activation and proliferation. This redox interplay establishes a feedback loop wherein tumor antioxidant defense mechanisms actively suppress the oxidative burst required for effective antitumor immunity (15,24).

The bidirectional nature of metabolic-immune crosstalk is evident in the feedback loops wherein immune-derived cytokines directly modulate tumor cell glutamine and ammonium metabolism. Hönscheid et al (11) demonstrated that PCa-associated fibroblasts manipulate glutamine metabolism in cancer cells through paracrine signaling, revealing that non-immune stromal elements also participate in this metabolic interaction. Lasorsa et al (7) demonstrated that inflammatory cytokines including interferon-γ and tumor necrosis factor-α produced by infiltrating lymphocytes feedback to modulate glutamine transporter expression, GLS activity and urea cycle enzyme expression in cancer cells. These immune-derived signals constrain or enhance tumor metabolic capacity depending on the context and duration of exposure. Acute exposure to inflammatory cytokines may suppress glutamine uptake and metabolism, contributing to the anti-proliferative effects of immune activation (7). However, chronic exposure to low-level inflammatory signals, characteristic of the TME, may select for tumor cells with adaptive metabolic programs that maintain glutamine flux despite cytokine-mediated stress. By intervening at the metabolic level, it is possible to simultaneously disrupt tumor metabolic adaptation and enhance the immunostimulatory capacity of TAMs, creating a cycle of antitumor immunity (7). Understanding these complex feedback associations is key for developing combination therapies that maximize therapeutic benefit while minimizing resistance mechanisms.

The bidirectional crosstalk between tumor metabolism and antitumor immunity in PCa operates through an integrated regulatory network organized across three interconnected levels. At the transcriptional level, oncogenic drivers including AR, Myc and mutant p53 coordinate glutamine metabolic gene expression through direct transcriptional activation and epigenetic modulation (9,13). AR differentially regulates metabolic pathways via full-length AR vs. AR-V7, while Myc drives GLS expression and glutamine uptake through transcriptional programs (64). PTEN loss enhances glutamine dependency via PI3K/AKT/mTOR pathway activation, and p53 status modulates mitochondrial glutamine use. At the metabolite signaling level, glutamine-derived ammonium directly impairs T cell receptor signaling and promotes macrophage arginase activity, establishing metabolite-driven immunosuppression (12,65). Simultaneously, glutamine-derived glutathione metabolism links tumor antioxidant defense with immune suppression through depletion of local antioxidant capacity (77). At the cell interaction level, feedback loops complete the bidirectional circuit: Immune-derived cytokines including interferon-γ and tumor necrosis factor-α modulate glutamine transporter expression, GLS activity and urea cycle enzyme expression in cancer cells, while tumor-secreted lactate, kynurenine and extracellular vesicles reshape immune cell metabolism and polarization (11,13,77). This multi-level network exhibits redundancy and adaptive plasticity, wherein pathway inhibition at one node typically triggers compensatory activation at alternative nodes, explaining the limited efficacy of monotherapy and providing the rationale for combinatorial strategies targeting multiple network nodes simultaneously.

Pharmacological targeting of glutamine metabolism has emerged as a promising therapeutic strategy, with multiple agents advancing through preclinical and clinical development for PCa. The GLS inhibitor CB-839 (telaglenastat) is the most clinically advanced agent, having demonstrated the ability to enhance PCa radiosensitivity by regulating redox state, stemness and autophagy (85). Bhowmick et al (10) reviewed strategies for targeting glutamine metabolism in PCa, emphasizing that therapeutic interventions should consider the differential glutamine requirements of tumor cells vs. antitumor immune populations. The glutamine antagonist JHU083, a prodrug that selectively activates within the TME, has shown promise in a preclinical study by reprogramming tumor-associated macrophages and enhancing antitumor immunity (14). Moon et al (40) demonstrated that targeting glutamine dependence with DRP-104, a novel glutamine antagonist, inhibits proliferation and tumor growth of CRPCa, validating glutamine metabolism as a therapeutic vulnerability in advanced disease. Beyond enzyme inhibition, transporter blockade targeting ASCT2 has shown efficacy in a preclinical model with Ono et al (21) demonstrating that fluciclovine uptake is associated with ASCT2 expression in CRPCa cells, providing both a therapeutic target and an imaging biomarker.

GLS inhibitor CB-839, glutamine antagonist prodrug JHU083 and glutamine antagonist DRP-104, exhibit distinct advantages and limitations that inform their therapeutic applicability. CB-839 offers the advantage of selective GLS inhibition with an established safety profile in clinical trials, being well-tolerated with mostly mild adverse effects including nausea, fatigue and photophobia (6,86). However, its clinical efficacy as monotherapy in PCa is limited; single-drug trials do not demonstrate notable clinical benefits, and combination studies with talazoparib were terminated due to challenges in demonstrating efficacy and slow recruitment (6). Furthermore, residual glutamine metabolism via GLS2 or other pathways may circumvent CB-839-mediated blockade (25). By contrast, JHU083 and DRP-104, as prodrugs of the broad glutamine antagonist 6-diazo-5-oxo-L-norleucine, provide broader metabolic inhibition by targeting multiple glutamine-utilizing enzymes beyond GLS, including amidotransferases involved in nucleotide biosynthesis (10). JHU083 offers the advantage of TME-selective activation, which reduces systemic toxicity while achieving potent local glutamine antagonism (14). DRP-104 exhibits broader metabolic inhibition compared with CB-839, further suppressing glycolysis and glutamine-dependent nucleotide biosynthesis (3). However, the broad-spectrum nature of these antagonists raises concerns regarding off-target effects and potential toxicity and their clinical development remains at earlier stages compared with CB-839 (6). The differential mechanisms of these agents and selective GLS inhibition vs. broad glutamine antagonism suggest that patient stratification based on tumor metabolic dependency may be key for optimizing therapeutic benefit.

The recognition that ammonium metabolism represents a potential therapeutic axis has spurred investigation into strategies targeting nitrogen handling in PCa. Ye et al (12) reviewed ammonium metabolism rewiring in the PCa ME, highlighting that urea cycle dysregulation creates tumor-specific vulnerabilities that can be exploited therapeutically. Targeting urea cycle enzymes, GLUD and ammonia scavengers represents an emerging therapeutic frontier with potential to disrupt nitrogen recycling while alleviating ammonium-mediated immunosuppression. Labroy et al (46) demonstrated metabolic crosstalk between the urea cycle and pyrimidine synthesis, identifying DHODH as a metabolic vulnerability that integrates nitrogen metabolism with nucleotide biosynthesis in both AR-positive and -negative PCa cells. This finding suggests that targeting nitrogen handling may be effective across PCa subtypes. Luo et al (45) revealed that PCa stem cells exhibit aberrant urea cycle activity with selective upregulation of specific urea cycle enzymes that support stemness maintenance, indicating that nitrogen partitioning is dynamically regulated across tumor subpopulations and may require combination strategies for effective targeting. The therapeutic potential of targeting ammonium metabolism extends beyond direct enzyme inhibition to include ammonia scavengers that may alleviate immunosuppression while depriving tumors of recyclable nitrogen.

Ammonium-targeting strategies are categorized into three principal approaches with distinct translational profiles. Urea cycle enzyme modulation is the most mechanistically direct strategy, aiming to restore ureagenesis and redirect nitrogen away from anabolic pathways, however, the multi-enzyme nature of the urea cycle creates pharmacological complexity, and, to the best of our knowledge, no urea cycle-activating agent has entered PCa clinical development (12,44). GLUD and GLUL inhibition offers a more pharmacologically tractable single-target approach to block nitrogen recycling within tumor cells, but creates a key immunological paradox: Inhibiting these enzymes may local ammonium concentrations, potentially exacerbating T cell dysfunction and macrophage M2 polarization (51,52). Ammonia scavengers, such as sodium phenylbutyrate, are the most translationally attractive strategy due to their US Food and Drug Administration-approved status for urea cycle disorders, yet their efficacy in the PCa TME remains unproven and systemic ammonia scavenging may affect nitrogen homeostasis (12).

To the best of our knowledge, none of the aforementioned ammonium-targeting strategies has been evaluated in combination with immune checkpoint blockade in PCa, representing a translational gap (12). The selection of optimal strategy will likely depend on balancing tumor metabolic disruption against the preservation of antitumor immunity: Urea cycle modulation and ammonia scavengers may alleviate ammonium-mediated immunosuppression but may support tumor nitrogen recycling, whereas GLUD/GLUL inhibition may starve tumors of nitrogen at the cost of worsening the immunosuppressive TME. Future research should prioritize combinatorial regimens that simultaneously target multiple nodes of ammonium metabolism, though such approaches remain hypothetical (12,82).

The limited efficacy of immune checkpoint inhibitors as monotherapy in PCa has driven investigation into combination strategies that sensitize tumors to immunotherapy. Sharma et al (87) reported preliminary analysis of patients in the CheckMate 650 trial, demonstrating that nivolumab + ipilimumab exhibits clinical activity in metastatic CRPCa, with response rates associated with tumor mutational burden and immune infiltration. Shenderov et al (88) conducted a phase 2 non-randomized clinical trial of nivolumab + ipilimumab, with or without enzalutamide, in AR-V7-expressing metastatic CRPCa, revealing that combination immunotherapy overcomes some mechanisms of treatment resistance. Powles et al (89) reported results from a randomized phase 3 trial of atezolizumab with enzalutamide vs. enzalutamide alone in metastatic CRPCa, demonstrating that while the addition of immunotherapy did not improve outcomes in unselected patients, biomarker-defined subgroups may derive benefit. Hegde et al (90) conducted a phase 1 dose-escalation study evaluating the safety and tolerability of evofosfamide, a hypoxia-activated prodrug, in combination with ipilimumab in advanced solid malignancy, providing proof-of-concept for combining ME-targeted metabolic agents with immune checkpoint blockade. These studies suggest that metabolic inhibitors targeting glutamine and ammonium metabolism may enhance the efficacy of immune checkpoint blockade by alleviating metabolic competition and immunosuppression within the TME.

The combination of metabolic inhibitors with immune checkpoint blockade presents both opportunities and challenges. Preclinical evidence demonstrates that combining glutamine antagonism (via JHU083 or DRP-104) or GLS inhibition (via CB-839) with PD-1/PD-L1 blockade enhances antitumor immunity in mouse models (3,14). However, metabolic inhibition can paradoxically impair CD8+ T cell function by upregulating PD-L1 expression on tumor cells via a reactive oxygen species-dependent EGFR/ERK1/2/c-Jun pathway, necessitating concurrent checkpoint blockade to restore T cell function (9). The differential effects of GLS inhibition vs. broad glutamine antagonism on immune cell populations remain incompletely characterized, representing a key knowledge gap for optimizing combination strategies.

The clinical translation of metabolic-immune therapies requires parallel development of imaging biomarkers for patient selection and response monitoring. Ono et al (21) demonstrated that fluciclovine uptake is associated with ASCT2 expression in CRPCa cells, validating amino acid positron emission tomography (PET) imaging as a non-invasive approach to assess glutamine transporter expression and target engagement. Lowentritt and Kipper (91) provided a guide for treating patients with biochemical recurrence of PCa using fluciclovine PET/computed tomography, emphasizing the clinical utility of metabolic imaging for detecting recurrent disease. Bhowmick et al (10) reviewed strategies for targeting glutamine metabolism in PCa, highlighting the need for predictive biomarkers to identify patients most likely to benefit from metabolic interventions. Smith et al (18) demonstrated that plasma glutamine levels may serve as prognostic biomarkers in localized PCa, with alterations in circulating glutamine associated with disease outcome, suggesting that liquid biopsy approaches may complement imaging for patient stratification. The integration of metabolic imaging with circulating biomarkers may enable precision medicine approaches that match patients with specific metabolic vulnerabilities to targeted therapy, ultimately improving outcomes while minimizing unnecessary toxicity.