Hypoxia In Solid Tumors Research Articles

Light-responsive nanodrugs co-self-assembled from a PEG-Pt(IV) prodrug and doxorubicin for reversing multidrug resistance in the chemotherapy process of hypoxic solid tumors.

Hypoxia-induced multi-drug resistance (MDR) often develops in the chemotherapy process of most anticancer drugs (e.g., doxorubicin, DOX) and results in treatment failure in the clinic. Herein, a PEG-Pt(IV) prodrug was co-self-assembled with DOX into nanodrugs (PEG-Pt(IV)@DOX NPs). They can accumulate in tumor sites due to their longer blood retention half-life. Under light irradiation, the PEG-Pt(IV) prodrug can in situ self-generate oxygen (O2) to reduce the hypoxic zone in tumor tissue effectively and simultaneously release active cis-Pt(II) and DOX. The increasing O2 concentration in the tumor tissue can raise the level of reactive oxygen species (ROS) produced from DOX and significantly enhance the cytotoxicity of DOX to inhibit tumor proliferation by combining with active cis-Pt(II). Finally, the hypoxia-induced MDR of DOX can be alleviated. More importantly, the enhanced cytotoxicity of DOX is limited to the tumor site, which can effectively reduce its side effects on normal tissues. In summary, this would be a promising platform for the combination chemotherapy of hypoxia solid tumors in the clinic.

Hypoxia as a driver of resistance to immunotherapy.

Hypoxia, a hallmark of solid tumors, determines the selection of invasive and aggressive malignant clones displaying resistance to radiotherapy, conventional chemotherapy or targeted therapy. The recent introduction of immunotherapy, based on immune checkpoint inhibitors (ICPIs) and chimeric antigen receptor (CAR) T-cells, has markedly transformed the prognosis in some tumors but also revealed the existence of intrinsic or acquired drug resistance. In the current review we highlight hypoxia as a culprit of immunotherapy failure. Indeed, multiple metabolic cross talks between tumor and stromal cells determine the prevalence of immunosuppressive populations within the hypoxic tumor microenvironment and confer upon tumor cells resistance to ICPIs and CAR T-cells. Notably, hypoxia-triggered angiogenesis causes immunosuppression, adding another piece to the puzzle of hypoxia-induced immunoresistance. If these factors concurrently contribute to the resistance to immunotherapy, they also unveil an unexpected Achille's heel of hypoxic tumors, providing the basis for innovative combination therapies that may rescue the efficacy of ICPIs and CAR T-cells. Although these treatments reveal both a bright side and a dark side in terms of efficacy and safety in clinical trials, they represent the future solution to enhance the efficacy of immunotherapy against hypoxic and therapy-resistant solid tumors.

Targeted photodynamic therapy using reconstituted high-density lipoproteins as rhodamine transporters

Reconstituted high-density lipoprotein (rHDL) nanoparticles are excellent transporters of molecules and very useful for targeted therapy as they specifically recognize the scavenger receptor, class B1 (SR-B1) that is present on the surface of a wide range of tumor cells. However, they have rarely been employed to transport photosensitizers (PS) for photodynamic therapy (PDT). Rhodamine (R) compounds have been dismissed as useful PSs for PDT due to their low 1O2 production, excitation wavelengths with little tissue penetration, and poor selectivity for tumor cells. It was recently demonstrated that when irradiating at 532 nm or with Cerenkov radiation (CR) from a β-emitting radionuclide, R123, R6G, and RB undergo electron transfer reactions (type I reaction) with folic acid. R6G also produces type I reactions with O2. In this work, the photodynamic effects of the rHDL-R system were evaluated in vitro. rHDL nanoparticles loaded with R123, R6G, and RB were synthesized, and the PS was internalized into T47D tumor cells. When cells were irradiated with a 532-nm laser in the presence of an rHDL-R systems, a cytotoxic photodynamic effect was obtained in the order R6G > R123 > RB. In the presence of CR from a 177Lu source, cytotoxicity showed the order R6G > RB > R123. The higher cytotoxicity induced by R6G in both cases corresponds to higher cellular internalization and larger production of type I and II reactions. Thus, in this work, it is proposed that rHDL-R/177Lu system can be applied in theragnostics as a multimodal radiotherapy-PDT-imaging system (imaging by SPECT or Cerenkov) and in hypoxic solid tumors in which external radiation is not effective and 177Lu-CR acts as light source.

RETSAT Mutation Selected for Hypoxia Adaptation Inhibits Tumor Growth.

Hypoxia occurs not only in natural environments including high altitude, underground burrows and deep sea, but also in human pathological conditions, such as hypoxic solid tumors. It has been well documented that hypoxia related signaling pathway is associated with a poor clinical outcome. Our group has recently identified multiple novel genes critical for solid tumor growth comparing the genome-wide convergent/parallel sequence evolution of highland mammals. Among them, a single mutation on the retinol saturase gene (RETSAT) containing amino acid switch from glutamine (Q) to arginine (R) at the position 247 was identified. Here, we demonstrate that RETSAT is mostly downregulated in multiple types of human cancers, whose lower expression correlates with worse clinical outcome. We show that higher expression of RETSAT is positively associated with immune infiltration in different human cancers. Furthermore, we identify that the promoter region of RETSAT is highly methylated, which leads to its decreased expressions in tumor tissues comparing to normal tissues. Furthermore, we show that RETSAT knockdown promotes, while its overexpression inhibits, the cell proliferation ability of mouse embryonic fibroblasts (MEFs) and B16 in vitro. In addition, the mice carrying homozygous Q247R mutation (RETSATR/R) is more resistant to xenograft tumor formation, as well as DMBA/TPA induced cutaneous keratinocyte carcinoma formation, compared to littermate wild-type (RETSATQ/Q) mice. Mechanistic study uncovers that the oncogenic factor, the prolyl isomerase (PPIase) Pin1 and its related downstream signaling pathway, were both markedly repressed in the mutant mice compared to the wild-type mice. In summary, these results suggest that interdisciplinary study between evolution and tumor biology can facilitate identification of novel molecular events essential for hypoxic solid tumor growth in the future.

Inhibition of Carbonic Anhydrase IX Suppresses Breast Cancer Cell Motility at the Single-Cell Level.

Protein Carbonic Anhydrase IX (CA IX), which is expressed in various hypoxic solid tumors in order to maintain proper pH, is also related to cancer cell adhesion, invasion, and metastasis processes. Here, we investigated whether CA IX inhibition by a highly CA IX selective agent benzenesulfonamide VD11-4-2 triggers changes in individual cell motility. We seeded breast cancer cells on an extracellular matrix-coated glass-bottomed dish and in a microfluidic device with a gradient flow of epidermal growth factor (EGF), tracked individual cell movement, calculated their migration speeds, and/or followed movement direction. Our results showed that the inhibitor VD11-4-2 decreased the speed of CA IX positive breast cancer cells by 20–26% while not affecting non-cancerous cell migration. The inhibitor suppressed the cell migration velocity increment and hindered cells from reaching their maximum speed. VD11-4-2 also reduced CA IX, expressing cell movement towards the growth factor as a chemoattractant. Such a single cell-based migration assay enabled the comprehensive investigation of the cell motility and revealed that VD11-4-2 shows the ability to suppress breast cancer cell migration at a lower concentration than previously tested CA IX inhibitors.

Intrinsic nucleus-targeted ultra-small metal\u2013organic framework for the type I sonodynamic treatment of orthotopic pancreatic carcinoma

BackgroundSonodynamic therapy (SDT) strategies exhibit a high tissue penetration depth and can achieve therapeutic efficacy by facilitating the intertumoral release of reactive oxygen species (ROS) with a short lifespan and limited diffusion capabilities. The majority of SDT systems developed to date are of the highly O2-dependent type II variety, limiting their therapeutic utility in pancreatic cancer and other hypoxic solid tumor types.ResultsHerein, a nucleus-targeted ultra-small Ti-tetrakis(4-carboxyphenyl)porphyrin (TCPP) metal–organic framework (MOF) platform was synthesized and shown to be an effective mediator of SDT. This MOF was capable of generating large quantities of ROS in an oxygen-independent manner in response to low-intensity ultrasound (US) irradiation (0.5 W cm−2), thereby facilitating both type I and type II SDT. This approach thus holds great promise for the treatment of highly hypoxic orthotopic pancreatic carcinoma solid tumors. This Ti-TCPP MOF was able to induce in vitro cellular apoptosis by directly destroying DNA and inducing S phase cell cycle arrest following US irradiation. The prolonged circulation, high intratumoral accumulation, and nucleus-targeting attributes of these MOF preparations significantly also served to significantly inhibit orthotopic pancreatic tumor growth and prolong the survival of tumor-bearing mice following Ti-TCPP + US treatment. Moreover, this Ti-TCPP MOF was almost completely cleared from mice within 7 days of treatment, and no apparent treatment-associated toxicity was observed.ConclusionThe nucleus-targeted ultra-small Ti-TCPP MOF developed herein represents an effective approach to the enhanced SDT treatment of tumors in response to low-intensity US irradiation.Graphic abstract

Antisense oligonucleotides-Laden UiO-66@Au nanohybrid for enhanced radiotherapy against hypoxic tumor by dual-inhibition of carbonic anhydrase IX

Hypoxia-acquired radioresitance is considered to be a major factor responsible for the clinical failure of radiotherapy. Carbonic anhydrase IX (CA IX), a hypoxia-induced cell-surface enzyme involved in pH regulation of hypoxic solid tumors, has been acknowledged as a desirable target for cancer therapy. Herein, we developed a dual exogenous/endogenous CA IX inhibition strategy using core/satellite-like metal-organic framework (UiO-66)/gold nanoparticles (Au NPs) nanohybrids as a therapeutic platform for hypoxia-relief enhanced RT of triple negative breast cancer. The UiO-66 matrix supported the Au NPs generation in situ and would decompose inside tumor cells by the high-concentration phosphates to release p-phthalic acid (PTA), a original building skeleton of the UiO-66 matrix, to inhibit CA IX, while the decorated Au NPs served as radiosensitizers to potentiate the sensitivity of tumor cells to X-ray and yet provided active sites for CA IX antisense oligonucleotide (ASO) loading via formation of stable Au-S bond to knockdown CA IX. The dual inhibitory manner, exogenous inhibition from PTA and endogenous inhibition from CA IX ASO, largely alleviated the hypoxia-induced resistance and synergized with Au NPs-mediated radiosensitization to afford super therapeutic outcome in vitro and in vivo, supporting the feasibility of our synergistic RT strategy in hypoxic tumor management.

Penetration Enhancing of an Erythrocyte-Mimicking Nanoplatform via Papaverine for Radiosensitization.

PurposeRadiotherapy (RT) is recommended as an extensive therapeutic regimen for cancer patients; however, cancer radio-resistance results from reduced oxygen levels (hypoxia) in the tumor microenvironment. Herein, we report a therapeutic strategy that greatly enhances the treatment effects of RT.MethodsSpecifically, papaverine (ppv), an FDA-approved smooth muscle relaxant, was applied in the strategy. Ppv improved blood flow via vasodilation to deliver sufficient oxygen to the hypoxic solid tumor and further resulted in increased tumor penetration of the radiosensitizer, significantly enhancing the radiosensitization compared with no ppv treatment. Additionally, tantalum oxide nanospheres were cloaked in red blood cell membranes (TaOx@M) to achieve greater biocompatibility, non-immunogenicity, and a longer circulation time.ResultsAs a high-Z element, tantalum provides localized dose enhancement and thereby boosts the efficacy of RT. Vasodilation, the oxygenation of cancer cells, and the improved accumulation and retention of TaOx@M in the tumor region were verified in vivo. Furthermore, compared with RT alone, the combined vasodilation and nanosphere camouflaging strategy more efficiently suppressed the growth of K7M2 tumors in mice.ConclusionThe results of this study suggest that the integration of TaOx@M and ppv has excellent potential for improving RT efficacy.

Photoacoustic nanodroplets for oxygen enhanced photodynamic therapy of cancer

Photodynamic therapy (PDT) is a well-known cancer therapy that utilizes light to excite a photosensitizer and generate cytotoxic reactive oxygen species (ROS). The efficacy of PDT primarily depends on the photosensitizer and oxygen concentration in the tumor. Hypoxia in solid tumors promotes treatment resistance, resulting in poor PDT outcomes. Hence, there is a need to combat hypoxia while delivering sufficient photosensitizer to the tumor for ROS generation. Here we showcase our unique theranostic perfluorocarbon nanodroplets as a triple agent carrier for oxygen, photosensitizer, and indocyanine green that enables light triggered spatiotemporal delivery of oxygen to the tumors. We evaluated the characteristics of the nanodroplets and validated their ability to deliver oxygen via photoacoustic monitoring of blood oxygen saturation and subsequent PDT efficacy in a murine subcutaneous tumor model. The imaging results were validated with an oxygen sensing probe, which showed a 9.1 fold increase in oxygen content inside the tumor, following systemic administration of the nanodroplets. These results were also confirmed with immunofluorescence. In vivo studies showed that nanodroplets held higher rates of treatment efficacy than a clinically available benzoporphyrin derivative formulation. Histological analysis showed higher necrotic area within the tumor with perfluoropentane nanodroplets. Overall, the photoacoustic nanodroplets can significantly enhance image-guided PDT and has demonstrated substantial potential as a valid theranostic option for patient-specific photodynamic therapy-based treatments.

Hypoxia in Solid Tumors: How Low Oxygenation Impacts the "Six Rs" of Radiotherapy.

Radiotherapy is an important component of cancer treatment, with approximately 50% of all cancer patients receiving radiation therapy during their course of illness. Nevertheless, solid tumors frequently exhibit hypoxic areas, which can hinder therapies efficacy, especially radiotherapy one. Indeed, hypoxia impacts the six parameters governing the radiotherapy response, called the « six Rs of radiation biology » (for Radiosensitivity, Repair, Repopulation, Redistribution, Reoxygenation, and Reactivation of anti-tumor immune response), by inducing pleiotropic cellular adaptions, such as cell metabolism rewiring, epigenetic landscape remodeling, and cell death weakening, with significant clinical repercussions. In this review, according to the six Rs, we detail how hypoxia, and associated mechanisms and pathways, impact the radiotherapy response of solid tumors and the resulting clinical implications. We finally illustrate it in hypoxic endocrine cancers through a focus on anaplastic thyroid carcinomas.

Genome-wide synthetic lethal screen unveils novel CAIX-NFS1/xCT axis as a targetable vulnerability in hypoxic solid tumors.

The metabolic mechanisms involved in the survival of tumor cells within the hypoxic niche remain unclear. We carried out a synthetic lethal CRISPR screen to identify survival mechanisms governed by the tumor hypoxia-induced pH regulator carbonic anhydrase IX (CAIX). We identified a redox homeostasis network containing the iron-sulfur cluster enzyme, NFS1. Depletion of NFS1 or blocking cyst(e)ine availability by inhibiting xCT, while targeting CAIX, enhanced ferroptosis and significantly inhibited tumor growth. Suppression of CAIX activity acidified intracellular pH, increased cellular reactive oxygen species accumulation, and induced susceptibility to alterations in iron homeostasis. Mechanistically, inhibiting bicarbonate production by CAIX or sodium-driven bicarbonate transport, while targeting xCT, decreased adenosine 5'-monophosphate-activated protein kinase activation and increased acetyl-coenzyme A carboxylase 1 activation. Thus, an alkaline intracellular pH plays a critical role in suppressing ferroptosis, a finding that may lead to the development of innovative therapeutic strategies for solid tumors to overcome hypoxia- and acidosis-mediated tumor progression and therapeutic resistance.

Advanced Cancer Starvation Therapy by Simultaneous Deprivation of Lactate and Glucose Using a MOF Nanoplatform.

Recent investigations reveal that lactate is not a waste product but a major energy source for cells, especially in the mitochondria, which can support cellular survival under glucose shortage. Accordingly, the new understanding of lactate prompts to target it together with glucose to pursue a more efficient cancer starvation therapy. Herein, zeolitic imidazolate framework‐8 (ZIF‐8) nanoplatforms are used to co‐deliver α‐cyano‐4‐hydroxycinnamate (CHC) and glucose oxidase (GOx) and fulfill the task of simultaneous depriving of lactate and glucose, resulting in a new nanomedicine CHC/GOx@ZIF‐8. The synthesis conditions are carefully optimized in order to yield monodisperse and uniform nanomedicines, which will ensure reliable and steady therapeutic properties. Compared with the strategies aiming at a single carbon source, improved starvation therapy efficacy is observed. Besides, more than boosting the energy shortage, CHC/GOx@ZIF‐8 can block the lactate‐fueled respiration and relieve solid tumor hypoxia, which will enhance GOx catalysis activity, depleting extra glucose, and producing more cytotoxic H2O2. By the synergistically enhanced anti‐tumor effect, both in vitro and in vivo cancer‐killing efficacies of CHC/GOx@ZIF‐8 show twice enhancements than the GOx mediated therapy. The results demonstrate that the dual‐depriving of lactate and glucose is a more advanced strategy for strengthening cancer starvation therapy.

Hyperbaric oxygen regulates tumor microenvironment and boosts commercialized nanomedicine delivery for potent eradication of cancer stem-like cells

Cancer stem-like cells (CSCs) depend highly on hypoxia in solid tumors and represent an intractable challenge for marketed nanomedicines. Herein, we for the first time leveraged hyperbaric oxygen (HBO) therapy to help commercialized nanomedicines, including Doxil and Abraxane, eliminate CSCs in stroma-rich solid tumors, e.g., triple negative breast cancer (TNBC) and pancreatic ductal adenocarcinoma (PDAC), for efficient cancer therapy. Mechanistically, we revealed that HBO disrupted hypoxia in solid tumors, thereby directly suppressing CSCs and cancer metastasis. More importantly, we found that HBO depleted excessive extracellular matrix, such as collagen and fibronectin, and thus normalized tumor blood vessels both structurally and functionally. As a consequence, HBO augmented the delivery of commercialized nanomedicines, but not small molecule drug, into solid tumors, in terms of tumor accumulation, deep penetration and cellular internalization, leading to efficient CSCs eradication and tumor inhibition. These results demonstrate that HBO enables commercialized nanomedicines to eliminate CSCs in stroma-rich solid tumors and suggest that the combination of HBO with commercialized nanomedicines is promising for the treatment of hypoxic solid tumors in the clinics.

Sclareol Inhibits Hypoxia-Inducible Factor-1α Accumulation and Induces Apoptosis in Hypoxic Cancer Cells.

Purpose: The hypoxia in solid tumors is associated with the resistance to chemo/radiotherapy. Hypoxia-inducible factor-1 (HIF-1) plays a key role in cell remodeling to hypoxia. Therefore, the inhibition of HIF-1 accumulation is considered a hopeful strategy for the treatment of cancer. Here, we aimed to evaluate the geno- and cytotoxicity properties of sclareol, a natural bicyclic diterpene alcohol, on A549 cells in CoCl2-induced hypoxia. Methods: The cytotoxicity and apoptosis-inducing properties of sclareol on the A549 cell were evaluated using MTT assay and Annexin V/PI staining, respectively in hypoxia. DAPI staining, DNA ladder, and comet assay were used to evaluate the genotoxicity. Further, the qPCR technique was employed to assess the expression of HIF-1α, HIF-1β, and downstream target genes (GluT1, and Eno1). Finally, the level of HIF-1α protein was evaluated through Western blotting in sclareol-treated cells in hypoxia. Results: The inhibitory concentration (IC50) of sclareol against A549 cells was 8 μg/mL at 48 hours in hypoxia. The genotoxicity of sclareol was confirmed in the cells treated with sclareol in hypoxia. Sclareol induced ~46% apoptosis and also necrosis in the hypoxic condition. The qPCR analyses showed an enhanced suppression of HIF-1α, HIF-1β, GluT1, and Eno1 due to the sclareol treatment in the hypoxia. Moreover, protein quantification analysis showed dose-dependently degradation of HIF-1α in hypoxia upon treatment with sclareol. Conclusion: The results obtained here indicate that sclareol possesses dose-dependent cytotoxicity effects against A549 cells in hypoxia through inhibition of HIF-1α protein accumulation, increasing cell sensitivity to intracellular oxygen levels, and disruption of cell adaptation to hypoxia.

Glutathione-Activated NO-/ROS-Generation Nanoparticles to Modulate the Tumor Hypoxic Microenvironment for Enhancing the Effect of HIFU-Combined Chemotherapy.

The combination of high-intensity focused ultrasound (HIFU) and chemotherapy has promising potential in the synergistic treatment of various types of solid tumors. However, the clinical efficacy of HIFU in combination chemotherapy is often impeded by the pre-existing hypoxia tumor microenvironment-induced multidrug resistance (MDR). Therefore, it is imperative for HIFU combined with chemotherapy to overcome MDR by improving the tumor hypoxic microenvironment. Hence, we developed highly stable nanoparticles (P@BDOX/β-lapachone-NO-NPs) with intracellular nitric oxide (NO)- and reactive oxygen species (ROS)-generating capabilities at the tumor site to relieve the hypoxic tumor microenvironment in solid tumors. Doxorubicin prodrug (boronate-DOX, BDOX) and β-lapachone were concurrently loaded onto actively targeted pH (low) insertion peptides (pHLIPs)-poly(ethylene glycol) and nitrated gluconic acid copolymers. Our results showed that the ability of P@BDOX/β-lapachone-NO-NPs to generate NO and ROS simultaneously is vital for the sensitization of hypoxic solid tumors for chemotherapy, as evidenced by the suppression of tumor cells and tissues (in vitro and in the nude mice model). Thus, this combined therapy holds considerable potential in the management of hypoxic solid tumors.

Tablet-like TiO2/C nanocomposites for repeated type I sonodynamic therapy of pancreatic cancer

Sonodynamic therapy (SDT) represents a viable approach to overcoming the limited ability of photodynamic therapy to penetrate biological barriers. However, pancreatic tumors contain a hypoxic microenvironment that limits the efficacy of oxygen-dependent type II SDT, complicating efforts to develop reliable, stable, and hypoxia-tolerant sonosensitizer. Herein, a tablet-like TiO2/C nanocomposite with a metal-organic-framework (MOF)-derived carbon structure was designed and found to be hypoxia-tolerant and stable in response to repeated ultrasound irradiation, enabling the TiO2/C-mediated generation of large quantities of reactive oxygen species (ROS) and thereby achieving efficacious type I SDT. Importantly, this nanocomposite continued to generate ROS in response to repeated ultrasound irradiation, and was able to induce tumor cell apoptosis via SDT-induced DNA damage in vitro and in vivo. This TiO2/C nanocomposite also exhibited good biocompatibility and did not induce any apparent toxicity in vitro and in vivo. Together, these data highlight TiO2/C as a valuable nanocomposite capable of facilitating repeated type I SDT, making it a promising tool for the treatment of hypoxic solid pancreatic tumors. Statement of significanceIn this research, a tablet-like TiO2/C nanocomposite with a metal-organic-framework (MOF)-derived carbon structure was designed, which exhibited great stability upon repeated ultrasound irradiation, hypoxic-tolerant ability and good biocompatibility. After ultrasound irradiation, TiO2/C could efficiently generate reactive oxygen species in an oxygen-independent manner, which overcame the limitation of pure TiO2 nanoparticles. Therefore, it was applied to repeated type I sonodynamic therapy of hypoxic pancreatic tumor.

Biomimetic sonodynamic therapy-nanovaccine integration platform potentiates Anti-PD-1 therapy in hypoxic tumors

Immune checkpoint blockade (ICB) therapy has emerged as novel therapeutic modality for hard-to-treat solid tumors. However, inadequate T cell infiltration in hypoxic solid tumors limits its anticancer efficacy. Here we develop a sonodynamic therapy (SDT)-nanovaccine integration platform constructed by binding a manganese porphyrin-based metal-organic frameworks (Mn-MOF) with an immune adjuvant CpG and then coating with cell membranes derived from ovalbumin (OVA)-overexpressing melanoma B16 cells (cMn-MOF@CM) for potentiating anti-programmed death receptor 1 (PD-1) antibody in malignant melanoma therapy. cMn-MOF@CM with prolonged blood circulation and enhanced tumor targeting efficiently relieves tumor hypoxia and generates strong SDT effects and immunogenic cell death. The tumor-associated antigens both in situ derived from SDT and OVA exhibit vaccine-like functions together with the immune adjuvant CpG, eliciting a strong tumor-specific immune response by promoting DC maturation and T cell activation. Importantly, the combination of cMn-MOF@CM-triggered SDT and anti-PD-1 antibody induces stronger systemic immune response and long-term immunological memory function to prevent tumor growth and recurrence. These findings reveal that cMn-MOF@CM with US irradiation may be a potential candidate to potentiate ICB therapy for hypoxic cancer therapy.

Good Steel Used in the Blade: Well‐Tailored Type‐I Photosensitizers with Aggregation‐Induced Emission Characteristics for Precise Nuclear Targeting Photodynamic Therapy

Photodynamic therapy (PDT) has long been recognized to be a promising approach for cancer treatment. However, the high oxygen dependency of conventional PDT dramatically impairs its overall therapeutic efficacy, especially in hypoxic solid tumors. Exploration of distinctive PDT strategy involving both high‐performance less‐oxygen‐dependent photosensitizers (PSs) and prominent drug delivery system is an appealing yet significantly challenging task. Herein, a precise nuclear targeting PDT protocol based on type‐I PSs with aggregation‐induced emission (AIE) characteristics is fabricated for the first time. Of the two synthesized AIE PSs, TTFMN is demonstrated to exhibit superior AIE property and stronger type‐I reactive oxygen species (ROS) generation efficiency owing to the introduction of tetraphenylethylene and smaller singlet–triplet energy gap, respectively. With the aid of a lysosomal acid‐activated TAT‐peptide‐modified amphiphilic polymer poly(lactic acid)12k–poly(ethylene glycol)5k–succinic anhydride‐modified TAT, the corresponding TTFMN‐loaded nanoparticles accompanied with acid‐triggered nuclear targeting peculiarity can quickly accumulate in the tumor site, effectively generate type‐I ROS in the nuclear region and significantly suppress the tumor growth under white light irradiation with minimized systematic toxicity. This delicate “Good Steel Used in the Blade” tactic significantly maximizes the PDT efficacy and offers a conceptual while practical paradigm for optimized cancer treatment in further translational medicine.

Rational construction of a reversible arylazo-based NIR probe for cycling hypoxia imaging in vivo

Reversible NIR luminescent probes with negligible photocytotoxicity are required for long-term tracking of cycling hypoxia in vivo. However, almost all of the reported organic fluorescent hypoxia probes reported until now were irreversible. Here we report a reversible arylazo-conjugated fluorescent probe (HDSF) for cycling hypoxia imaging. HDSF displays an off-on fluorescence switch at 705 nm in normoxia-hypoxia cycles. Mass spectroscopic and theoretical studies confirm that the reversible sensing behavior is attributed to the two electron-withdrawing trifluoromethyl groups, which stabilizes the reduction intermediate phenylhydrazine and blocks the further reductive decomposition. Cycling hypoxia monitoring in cells and zebrafish embryos is realized by HDSF using confocal imaging. Moreover, hypoxic solid tumors are visualized and the ischemia-reperfusion process in mice is monitored in real-time. This work provides an effective strategy to construct organic fluorescent probes for cycling hypoxia imaging and paves the way for the study of cycling hypoxia biology.

A smart O2-generating nanocarrier optimizes drug transportation comprehensively for chemotherapy improving

Drug transportation is impeded by various barriers in the hypoxic solid tumor, resulting in compromised anticancer efficacy. Herein, a solid lipid monostearin (MS)-coated CaO2/MnO2 nanocarrier was designed to optimize doxorubicin (DOX) transportation comprehensively for chemotherapy enhancement. The MS shell of nanoparticles could be destroyed selectively by highly-expressed lipase within cancer cells, exposing water-sensitive cores to release DOX and produce O2. After the cancer cell death, the core-exposed nanoparticles could be further liberated and continue to react with water in the tumor extracellular matrix (ECM) and thoroughly release O2 and DOX, which exhibited cytotoxicity to neighboring cells. Small DOX molecules could readily diffuse through ECM, in which the collagen deposition was decreased by O2-mediated hypoxia-inducible factor-1 inhibition, leading to synergistically improved drug penetration. Concurrently, DOX-efflux-associated P-glycoprotein was also inhibited by O2, prolonging drug retention in cancer cells. Overall, the DOX transporting processes from nanoparticles to deep tumor cells including drug release, penetration, and retention were optimized comprehensively, which significantly boosted antitumor benefits.