A Multifunctional Nanoplatform Based on Lactate Depletion and Hydrogen Peroxide Accumulation for MRI-Guided Tumor Therapy.

The depth of light penetration and tumor hypoxia restrict the efficacy of photodynamic therapy (PDT) in triple-negative breast cancer (TNBC), while the overproduction of lactate (LA) facilitates the development, aggressiveness, and therapy resistance of TNBC. To address these issues, a self-acting PDT nanosystem (HL@hMnO2-LOx@HA) is fabricated by loading 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-alpha (HPPH), luminol, and LA oxidase (LOx) in a hyaluronic acid (HA)-coated hollow manganese dioxide (hMnO2) nanoparticle. LOx catalyzes the oxidation of LA into pyruvate and hydrogen peroxide (H2O2), thus depleting the overproduced intratumoral LA. In the acidic tumor microenvironment, H2O2 reacts with luminol and hMnO2 to yield blue luminescence as well as O2 and Mn2+, respectively. Mn2+ could further enhance this chemiluminescence. HPPH is then excited by the chemiluminescence through chemiluminescence resonance energy transfer for self-illuminated PDT. The generated O2 alleviates the hypoxia state of the TNBC tumor to produce sufficient 1O2 for self-oxygenation PDT. The Mn2+ performs T1 magnetic resonance imaging to trace the self-acting PDT process. This work provides a biocompatible strategy to conquer the limits of light penetration and tumor hypoxia on PDT against TNBC as well as LA overproduction.

Copper-doped layered double hydroxides co-deliver proteins/drugs for cascaded chemodynamic/immunotherapy via dual regulation of tumor metabolism.

The immunosuppressive tumor microenvironment (TME) significantly limits the efficacy of cancer immunotherapy. Activation of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) stimulator of interferon genes (STING) pathway and depletion of the tumor metabolic byproduct lactate (LA) represent promising strategies to reverse the immunosuppressive TME and enhance antitumor therapeutic outcomes. Herein, biomineralized engineered bacterial outer membrane vesicles (OMVs@MnCaP-FA) are developed to synergistically activate the cGAS-STING pathway and modulate LA metabolism for antitumor immunotherapy. Upon internalization by 4T1 tumor cells, OMVs@MnCaP-FA undergo acid-responsive degradation, releasing Ca2+, Mn2+, and lactate oxidase (LOX)-expressing OMVs (OMVs-EcL). These components collectively promote mitochondrial DNA (mtDNA) generation, enhance cGAS-mediated mtDNA recognition and cyclic GMP-AMP (cGAMP) production, and potentiate the binding of cGAMP to STING, leading to robust activation of the cGAS-STING signaling pathway. More importantly, OMVs-EcL-mediated LA depletion reprograms the immunosuppressive TME into an immunoresponsive state, revitalizing antitumor immunity. In vivo studies demonstrate that the combined activation of the cGAS-STING pathway and regulation of LA metabolism effectively inhibit primary tumor growth and metastatic progression, highlighting the potential of this synergistic strategy for advancing antitumor immunotherapy.

Lactate is an immunosuppressive molecule that plays an important role in tumor progression. Regulating lactate metabolism to remodel the immunosuppressive microenvironment represents a promising strategy for cancer therapy. However, owing to the hypoxic nature of the tumor microenvironment and single intervention strategies, the effect of lactate oxidase for cancer therapy is not as expected. Therefore, we engineered a self-oxygen-generating nanoplatform by encapsulating lactate oxidase and manganese porphyrin within nanoliposomes (ML@Lip). Lactate depletion via lactate oxidase promoted the polarization of tumor-associated macrophages toward the M1 phenotype in the tumor microenvironment and modulated innate antitumor immunity. Manganese porphyrin-mediated sonodynamic therapy induced not only tumor cell apoptosis but also immunogenic cell death. The release of damage-associated molecular patterns promoted dendritic cell maturation and T-cell activation, leading to immune system activation and the initiation of adaptive immunity. Additionally, manganese catalyzed the decomposition of hydrogen peroxide (derived from lactate breakdown) to generate substantial oxygen. This process established a positive feedback loop via lactate depletion while amplifying sonodynamic therapeutic effects through enhanced oxygen production. Therefore, the strategy of combining lactate depletion-induced starvation therapy, sonodynamic therapy and self-circulating oxygen generation effectively remodeled the immunosuppressive tumor microenvironment and inhibited tumor growth, thereby providing novel insights into targeted lactate metabolism therapy.

Lactate, a characteristic metabolite of the tumor microenvironment (TME), drives immunosuppression and promotes tumor progression. Material-engineered strategies for intratumoral lactate modulations demonstrate their promise for tumor immunotherapy. However, understanding of the inherent interconnections of material-enabled lactate regulation, metabolism, and immunity in the TME is scarce. To address this issue, urchin-like catalysts of the encapsulated Gd-doped CeO2 , syrosingopine, and lactate oxidase are used in ZIF-8 (USL, where U, S, and L represent the urchin-like Gd-doped CeO2 @ZIF-8, syrosingopine, and lactate oxidase, respectively) and orthotopic tumor models. The instructive relationships of intratumoral lactate depletion, metabolic reprogramming, and immune activation for catalytic immunotherapy of tumors is illustrated. The catalysts efficiently oxidize intratumoral lactate and significantly promote tumor cell apoptosis by in situ-generated ·OH, thereby reducing glucose supply and inducing mitochondrial damage via lactate depletion, thus reprogramming glycometabolism. Subsequently, such catalytic metabolic reprogramming evokes both local and systemic antitumor immunity by activating M1-polarizaed macrophages and CD8+ T cells, leading to potent antitumor immunity. This study provides valuable mechanistic insights into material-interfered tumor therapy through intratumoral lactate depletion and consequential connection with metabolic reprogramming and immunity remodeling, which is thought to enhance the efficacy of immunotherapy.

The high level of lactate in tumor microenvironment not only promotes tumor development and metastasis, but also induces immune escape, which often leads to failures of various tumor therapy strategies. We here report a sono‐triggered cascade lactate depletion strategy by using semiconducting polymer nanoreactors (SPNLCu) for cancer cuproptosis‐immunotherapy. The SPNLCu mainly contain a semiconducting polymer as sonosensitizer, lactate oxidase (LOx) conjugated via a reactive oxygen species (ROS)‐cleavable linker and chelated Cu2+. Upon ultrasound (US) irradiation, the semiconducting polymer generates singlet oxygen (1O2) to cut ROS‐cleavable linker to allow the release of LOx that catalyzes lactate depletion to produce hydrogen peroxide (H2O2). The Cu2+ will be reduced to Cu+ in tumor microenvironment, which reacts with the produced H2O2 to obtain hydroxyl radical (⋅OH) that further improves LOx release via destroying ROS‐cleavable linkers. As such, sono‐triggered cascade release of LOx achieves effective lactate depletion, thus relieving immunosuppressive roles of lactate. Moreover, the toxic Cu+ induces cuproptosis to cause immunogenic cell death (ICD) for activating antitumor immunological effect. SPNLCu are used to treat both subcutaneous and deep‐tissue orthotopic pancreatic cancer with observably enhanced efficacy in restricting the tumor growths. This study thus provides a precise and effective lactate depletion tactic for cancer therapy.

The high level of lactate in tumor microenvironment not only promotes tumor development and metastasis, but also induces immune escape, which often leads to failures of various tumor therapy strategies. We here report a sono-triggered cascade lactate depletion strategy by using semiconducting polymer nanoreactors (SPNLCu) for cancer cuproptosis-immunotherapy. The SPNLCu mainly contain a semiconducting polymer as sonosensitizer, lactate oxidase (LOx) conjugated via a reactive oxygen species (ROS)-cleavable linker and chelated Cu2+. Upon ultrasound (US) irradiation, the semiconducting polymer generates singlet oxygen (1O2) to cut ROS-cleavable linker to allow the release of LOx that catalyzes lactate depletion to produce hydrogen peroxide (H2O2). The Cu2+ will be reduced to Cu+ in tumor microenvironment, which reacts with the produced H2O2 to obtain hydroxyl radical (⋅OH) that further improves LOx release via destroying ROS-cleavable linkers. As such, sono-triggered cascade release of LOx achieves effective lactate depletion, thus relieving immunosuppressive roles of lactate. Moreover, the toxic Cu+ induces cuproptosis to cause immunogenic cell death (ICD) for activating antitumor immunological effect. SPNLCu are used to treat both subcutaneous and deep-tissue orthotopic pancreatic cancer with observably enhanced efficacy in restricting the tumor growths. This study thus provides a precise and effective lactate depletion tactic for cancer therapy.

Targeting hypoxic and acidic tumor microenvironment by nanoparticles: A review

Lactate accumulation in the solid tumor is highly relevant to the immunosuppressive tumor microenvironment (TME). Targeting lactate metabolism significantly enhances the efficacy of immunotherapy. However, lactate depletion by lactate oxidase (LOX) consumes oxygen and results in the aggravated hypoxia situation, counteracting the benefit of lactate depletion. Beyond the TME regulation, it is necessary to initiate the effective immunity cycle for therapeutic purposes. In this fashion, dual close-loop of catalyzed lactate depletion and immune response by a rational material design are established to address this issue. Here, we constructed PEG-modified mesoporous polydopamine nanoparticles with Cu2+ chelation and LOX encapsulation (denoted as mCuLP). After mCuLP nanosystems targeting into the tumor sites, released LOX consumes lactate to H2O2. Subsequently, the produced H2O2 is further catalyzed by Cu2+-chelated mPDA to produce oxygen, supplying the oxygen source for the closed-loop of lactate depletion. Meanwhile, the mild PTT caused by the photothermal mPDA induces ICD of tumor cells to promote DC maturation and then T lymphocyte infiltration to kill tumor cells, which forms another closed-loop for cancer immunity. Therefore, this dual closed-loop strategy of mCuLP nanosystems effectively inhibits tumor growth, providing a promising treatment modality to cancer immunotherapy.

Simple SummaryTumor associated macrophages (TAMs) support disease progression by providing tumor cells cytokines and chemokines necessary for malignant growth and nutrient support. In the tumor microenvironment (TME), TAMs often rewire their metabolism to reprogram their functions, which includes changes in the production of angiogenic factors and cytokines. These promote the pro-tumor function of the TAMs as well as the blunt T cell’s effector function, which at least, in part, explains the failure or sub-optimal efficacies of TAM-directed therapeutic approaches and immunotherapies. In recent times, much of these are attributed to the altered metabolism of the TAMs in the TME. Therefore, understanding the metabolic changes of the myeloid cells of the TME is an essential step in developing novel therapeutic approaches targeting immune cell metabolism. This review article aims to summarize the recent findings on the metabolism of TAMs, and how the altered metabolism of these innate immune cells shapes the tumor microenvironment and the anti-tumor immunity.Cancer cells possess a high metabolic demand for their rapid proliferation, survival, and progression and thus create an acidic and hypoxic tumor microenvironment (TME) deprived of nutrients. Moreover, acidity within the TME is the central regulator of tumor immunity that influences the metabolism of the immune cells and orchestrates the local and systemic immunity, thus, the TME has a major impact on tumor progression and resistance to anti-cancer therapy. Specifically, myeloid cells, which include myeloid-derived suppressor cells (MDSC), dendritic cells, and tumor-associated macrophages (TAMs), often reprogram their energy metabolism, resulting in stimulating the angiogenesis and immunosuppression of tumors. This review summarizes the recent findings of glucose, amino acids, and fatty acid metabolism changes of the tumor-associated macrophages (TAMs), and how the altered metabolism shapes the TME and anti-tumor immunity. Multiple proton pumps/transporters are involved in maintaining the alkaline intracellular pH which is necessary for the glycolytic metabolism of the myeloid cells and acidic TME. We highlighted the roles of these proteins in modulating the cellular metabolism of TAMs and their potential as therapeutic targets for improving immune checkpoint therapy.

Artificial multienzyme systems hold promise for tumor catalytic immunotherapy by a cascade catalyzing the generation of reactive oxygen species (ROS). However, the intricate redox homeostasis restricts ROS accumulation coupled with the immunosuppressive tumor microenvironment (TME), resulting in unsatisfactory therapeutic efficacy. Developing multienzyme systems that can overcome multifaceted TME limitations for effective catalytic immunotherapy is still a significant challenge. Inspired by natural metalloenzymes, herein, a synergistic multienzyme nanoplatform (Co3S4@LOx/HA) is constructed by integrating mixed-valent cobalt sulfide (Co3S4) nanozymes as artificial cofactors and lactate oxidase (LOx) as protein scaffolds, encapsulated with hyaluronic acid (HA). Through self-cyclic cascade catalysis involving multienzyme activities (LOx, catalase-like, peroxidase-like, and glutathione peroxidase-like activities), Co3S4@LOx/HA can concurrently facilitate H2O2 and •OH generation and deplete intracellular glutathione (GSH). Moreover, Co3S4@LOx/HA can also inhibit endogenous thioredoxin reductase (TrxR) activity by the acidic TME-responsive release of hydrogen sulfide (H2S), further disrupting intracellular redox homeostasis. As a result, the significantly amplified ROS increased double-stranded DNA damage and leakage, thereby activating the stimulator of interferon genes (STING)-related immune responses. Additionally, lactate consumption and O2 generation during catalytic processes remodeled the immunosuppressive TME. Overall, Co3S4@LOx/HA is the first multienzyme nanoplatform that can simultaneously modulate multiple redox homeostasis and the immunosuppressive TME for precise and efficient tumor catalytic immunotherapy. This biomimetic metalloenzyme strategy will inspire more innovative designs of multienzyme nanoplatforms for ROS-mediated tumor therapies.

The abundant tumor extracellular matrix (ECM) could result in insufficient tumor retention and ineffective intratumor penetration of therapeutic agents as well as an acidic and hypoxic tumor microenvironment (TME), leading to unsatisfactory therapeutic outcomes for many types of therapies. Therefore, developing strategies to modulate the TME by selectively degrading the condensed ECM may be helpful to improve existing cancer therapies. Herein, collagenase (CLG)-encapsulated nanoscale coordination polymers (NCPs) are synthesized based on Mn2+ and an acid-sensitive benzoic-imine organic linker and then modified by polyethylene glycol (PEG). Upon intravenous (iv) injection, these CLG@NCP-PEG nanoparticles show efficient accumulation within the tumor, in which CLG would be released because of the collapse of NCP structures within the acidic TME. The released CLG enzyme could then specifically degrade collagens, the major component of ECM, leading to a loosened ECM structure, enhanced tumor perfusion, and relieved hypoxia. As a result, the second wave of nanoparticles, chlorin e6 (Ce6)-loaded liposomes (liposome@Ce6), would exhibit enhanced retention and penetration within the tumor. Such phenomena together with relieved tumor hypoxia could then lead to greatly enhanced photodynamic therapeutic effect of liposome@Ce6 for mice pretreated with CLG@NCP-PEG. Our work thus presents a unique strategy for TME modulation using pH-responsive NCPs as smart enzyme carriers.

This study applied a dual-agent, 13C-pyruvate and 13C-urea, hyperpolarized 13C magnetic resonance spectroscopic imaging (MRSI) and multi-parametric (mp) 1H magnetic resonance imaging (MRI) approach in the transgenic adenocarcinoma of mouse prostate (TRAMP) model to investigate changes in tumor perfusion and lactate metabolism during prostate cancer development, progression and metastases, and after lactate dehydrogenase-A (LDHA) knock-out. An increased Warburg effect, as measured by an elevated hyperpolarized (HP) Lactate/Pyruvate (Lac/Pyr) ratio, and associated Ldha expression and LDH activity were significantly higher in high- versus low-grade TRAMP tumors and normal prostates. The hypoxic tumor microenvironment in high-grade tumors, as measured by significantly decreased HP 13C-urea perfusion and increased PIM staining, played a key role in increasing lactate production through increased Hif1α and then Ldha expression. Increased lactate induced Mct4 expression and an acidic tumor microenvironment that provided a potential mechanism for the observed high rate of lymph node (86%) and liver (33%) metastases. The Ldha knockdown in the triple-transgenic mouse model of prostate cancer resulted in a significant reduction in HP Lac/Pyr, which preceded a reduction in tumor volume or apparent water diffusion coefficient (ADC). The Ldha gene knockdown significantly reduced primary tumor growth and reduced lymph node and visceral metastases. These data suggested a metabolic transformation from low- to high-grade prostate cancer including an increased Warburg effect, decreased perfusion, and increased metastatic potential. Moreover, these data suggested that LDH activity and lactate are required for tumor progression. The lactate metabolism changes during prostate cancer provided the motivation for applying hyperpolarized 13C MRSI to detect aggressive disease at diagnosis and predict early therapeutic response.

Streptococcus pyogenes strains can be divided into two classes, one capable and the other incapable of producing H2O2 (M. Saito, S. Ohga, M. Endoh, H. Nakayama, Y. Mizunoe, T. Hara, and S. Yoshida, Microbiology 147:2469-2477, 2001). In the present study, this dichotomy was shown to parallel the presence or absence of H2O2-producing lactate oxidase activity in permeabilized cells. Both lactate oxidase activity and H2O2 production under aerobic conditions were detectable only after glucose in the medium was exhausted. Thus, the glucose-repressible lactate oxidase is likely responsible for H2O2 production in S. pyogenes. Of the other two potential H2O2-producing enzymes of this bacterium, NADH and alpha-glycerophosphate oxidase, only the former exhibited low but significant activity in either class of strains. This activity was independent of the growth phase, suggesting that the protein may serve in vivo as a subunit of the H2O2-scavenging enzyme NAD(P)H-linked alkylhydroperoxide reductase. The activity of lactate oxidase was associated with the membrane while that of NADH oxidase was in the soluble fraction, findings consistent with their respective physiological roles, i.e., the production and scavenging of H2O2. Analyses of fermentation end products revealed that the concentration of lactate initially increased with time and decreased on glucose exhaustion, while that of acetate increased during the culture. These results suggest that the lactate oxidase activity of H2O2-producing cells oxidizes lactate to pyruvate, which is in turn converted to acetate. This latter process proceeds presumably via acetyl coenzyme A and acetyl phosphate with formation of extra ATP.

Tumor microenvironment-responsive nanozymes achieve photothermal-enhanced multiple catalysis against tumor hypoxia