Ferroptosis and Photodynamic Therapy Synergism: Enhancing Anticancer Treatment

Selective and iron-independent ferroptosis in cancer cells induced by manipulation of mitochondrial fatty acid oxidation

Despite the promise of ferroptosis in cancer therapy, selectively inducing robust ferroptosis in cancer cells remains a significant challenge. In this study, manipulation of fatty acids β-oxidation (FAO) by combination of mild photodynamic therapy (PDT) and inhibition of triglycerides (TGs) synthesis was found to induce robust and iron-independent ferroptosis in cancer cells with dysregulated lipid metabolism for the first time. To achieve that, TGs synthesis inhibitor of xanthohumol (Xan) and FAO initiator of tetrakis (4-carboxyphenyl) porphyrin (TCPP) were co-delivered by a nanoplexes composed of pH-responsive amphiphilic lipopeptide C18-pHis10 and DSPE-PEG2000. TCPP was found to rapidly increase the intracellular ROS under laser irradiation without inducing antioxidant response and apoptosis, activating the AMPK in cancer cells and accelerating mitochondrial FAO. Xan fueled the mitochondrial FAO with substrates by suppressing the conversion of fatty acids (FAs) to TGs. This also led to augmented intracellular polyunsaturated fatty acids (PUFAs) and PUFAs-phospholipids levels, increasing the intrinsic susceptibility of cancer cells to lipid peroxidization. As a result, the excessive ROS generated from the sustained mitochondrial FAO caused remarkably lipid peroxidation and ultimately ferroptosis. Collectively, our study provides a new approach to selectively induce iron-independent ferroptosis in cancer cells by taking advantage of dysregulated lipid metabolism.

Exosome/liposome hybrid nanovesicles for enhanced phototherapy and boosted anti-tumor immunity against melanoma

Although phototherapy shows great potential as a safe ablative modality for treatment of cutaneous melanoma, there remain serious flaws restricting its therapeutic outcomes, such as cellular resistance against apoptosis, tumor hypoxia, rewritten cellular metabolism and abnormal angiogenesis. To cope with these challenges, this work combines hemin and IR780 (phototherapy agent) and designs an orchestrated liposome/macrophage-derived exosome hybrid delivery system (named IHEL) for tumor-specific delivery of these two drugs and synchronous tumor microenvironment (TME) reprogramming. As the experimental data suggest, by triggering iron overload and up-regulating HMOX-1, hemin drives a shift from an apoptosis-dominant anti-cancer mode to a combined ferroptosis/apoptosis mode of IR780 treatment, which helps to avoid apoptosis resistance. Also, the catalase-like activity of hemin strengthens PDT effect by alleviating hypoxia. In addition to the above-mentioned enhanced direct cell-killing effect, IHEL also provokes anti-cancer immunity by triggering immunogenic cell death (ICD), intervening glycometabolism and polarizing tumor-associated macrophages (TAMs) in TME to M1-type. This work strongly demonstrated the rationality of IR780/hemin combination and delicately designed immunostimulatory nanocarriers for their tumor-specific delivery, providing both theoretical foundation and practical strategies for advanced anti-cancer phototherapy.

Cytoplasmic Vacuolization: A Fascinating Morphological Alteration From Cellular Stress to Cell Death

Cytoplasmic vacuolization is a cellular morphological alteration characterized by the presence of substantial vacuole-like structures originating from various cellular organelles. This phenomenon is often observed in various anticancer treatments, including chemotherapeutic drugs, and photodynamic therapy (PDT), and is frequently linked with cell death. Nevertheless, the precise mechanisms underlying cytoplasmic vacuolization and ensuing cell death remain ambiguous. Cytoplasmic vacuolization associated cell death (CVACD) is a complex process characterized by cellular stress, encompassing ER stress, heightened membrane permeability, ion imbalance, and mitochondrial dysfunction. The MAPK signaling pathway is closely associated with the activation of CVACD. This review provides a thorough examination of contemporary studies on cytoplasmic vacuolization in mammalian cells, elucidating its etiology, origins, and molecular pathways. Additionally, it highlights the potential of CVACD as an innovative therapeutic strategy for cancer.

UCNPs@PVP-Hemin-GOx@CaCO3 Nanoplatform for Ferroptosis Self-Amplification Combined with Calcium Overload

Due to the complexity of the tumor microenvironment (TME), current tumor treatments cannot achieve satisfactory results. A nanocomposite material, UCNPs@PVP-Hemin-GOx@CaCO3 (UPHGC NPs) is developed that responds to the TME and controls release to achieve multimodal synergistic therapy in tumor tissues. UPHGC NPs mediate photodynamic therapy (PDT), chemodynamic therapy (CDT), and starvation therapy (ST) synergistically, ultimately inducing self-amplification of ferroptosis. The Hemin loaded in UPHGC NPs exhibits peroxidase (POD) activity, which can react with H2O2 to produce ·OH (CDT) and generate the maximum amount of ·O2 - (PDT) under UV excitation from upconversion materials. Hemin can also consume glutathione (GSH), downregulate glutathione peroxidase 4 (GPX4), and combine with PDT/CDT to induce lipid peroxidation (LPO), leading to ferroptosis. In addition, Glucose oxidase (GOx) provides sufficient H2O2 for the ·OH production, amplifying ROS generation to further enhance ferroptosis. The gluconic acid produced by GOx during the ST process synergizes with the TME's acidic conditions to promote Ca2+ release, induce intracellular calcium overload, enhance oxidative stress, lead to mitochondrial dysfunction, and ultimately kill tumor cells through mitochondrial damage. Furthermore, the externally mineralized calcium carbonate can prevent premature drug release in normal tissues.

Novel ꞵ-carboline/cyanoisoflavone photosensitizers for ferroptosis-induced efficient chemo-photodynamic synergistic cancer therapy

Photodynamic therapy (PDT) is an emerging therapeutic modality to selectively eradicate pathological cells, such as cancer cells. Hence, we designed and synthesized a series of novel ꞵ-carboline/cyanoisoflavone photosensitizers A1-A3. All compounds possessed potent type-I/-II photodynamic properties. Especially, the optimized compound A2 produced large amounts of •O2-, •OH, and 1O2 under irradiation, and exhibited a higher quantum yield of singlet oxygen (ΦΔ = 0.92) than others. Furthermore, A2 not only exhibited potent cytotoxicity in HT29 cells, but also demonstrated prominent chemo-photodynamic effects with IC50 values of 3.9-4.1 μM under normoxic and hypoxic conditions in HT29 cells, while exhibited minimal toxicity to normal cells, suggesting its tumor-selective and hypoxia-tolerant efficacy. Most importantly, A2 significantly promoted mitochondrial damage and ferroptosis, through depleting GSH/GPX-4 levels and increasing malondialdehyde (MDA) expression. Finally, in vivo studies showed that A2 achieved a high colonic tumor-inhibitory rate of 84.6 % through chemo-photodynamic therapy. These findings provide a promising framework for the development of novel photosensitizers for chemo-photodynamic therapy.

An endoplasmic reticulum and lipid droplets dual-localized strategy to develop small molecular photosensitizers that induce ferroptosis during photodynamic therapy

Organelle-localized photosensitizers have been well-developed to enhance the photodynamic therapy (PDT) efficacy through triggering given cell death. The endoplasmic reticulum (ER) and lipid droplets (LDs) are two key organelles mutually regulating ferroptosis. Thus, in this study, small molecular photosensitizer CAR PSs were developed through fragment integration strategy and the heavy-atom modification. It was showed that the integration strategy did not affect the organelle localization and CAR PSs successfully achieved ER/LDs dual location. Besides, the heavy-atom modification help CAR PSs display good ROS generation efficiency. Importantly, ER/LDs dual-localized CAR PSs exhibited superior photo-toxicity and lower dark-toxicity against multiple breast cancer cell lines than the only ER-targeting Ce6, which further explained the superposition effect of dual organelle targeting. Preliminary studies revealed that CAR PSs induced enhanced ferroptosis via simultaneously triggering the ER stress and lipid peroxidation during PDT. Moreover, CAR-2 demonstrated significant in vivo PDT activity to suppress the tumor growth in 4T1 tumor bearing mice. These findings not only provide a promising photosensitizer CAR-2 exerting excellent in vitro and in vivo PDT effect through stimulating ferroptosis, but also propose a design strategy for the development of ER/LDs dual localized PSs.

Hijacking the hyaluronan assisted iron endocytosis to promote the ferroptosis in anticancer photodynamic therapy

Photodynamic therapy (PDT) eradicates tumor cells by the light-stimulated reactive oxygen species, which also induces lipid peroxidation (LPO) and subsequently ferroptosis, an iron-depended cell death. Ferroptosis has a tremendous therapeutic potential in cancer treatment, however, the ferroptosis efficiency is largely limited by the available iron in cells. Through hijacking the CD44-mediated iron endocytosis of hyaluronan (HA), here PDT with enhanced ferroptosis was realized by a HA@Ce6 nanogel self-assembled from HA, a photosensitizer Chlorin e6 (Ce6) and Fe3+ as cross-linkers. Taking advantages of HA's natural affinity towards CD44, HA@Ce6 enabled a targeted Ce6 delivery in CD44-overexpressed breast cancer cells and meanwhile enhanced iron uptake to "fuel" ferroptosis together with the light-stimulated LPO. Further, HA@Ce6 demonstrated an excellent anticancer PDT efficacy and ferroptosis induction in the murine 4 T1 xenograft model. This HA@Ce6 successfully exploited the role of HA in iron transport to sensitize ferroptosis, providing a potent strategy to facilitate the anticancer PDT.

Applications and enhancement strategies of ROS-based non-invasive therapies in cancer treatment

Reactive oxygen species (ROS) play a crucial role in the pathogenesis of cancer. Non-invasive therapies that promote intracellular ROS generation, including photodynamic therapy (PDT), sonodynamic therapy (SDT), and chemodynamic therapy (CDT), have emerged as novel approaches for cancer treatment. These therapies directly kill tumor cells by generating ROS, and although they show great promise in tumor treatment, many challenges remain to be addressed in practical applications. Firstly, the inherent complexity of the tumor microenvironment (TME), such as hypoxia and elevated glutathione (GSH) levels, hinders ROS generation, thereby significantly diminishing the efficacy of ROS-based therapies. In addition, these therapies are influenced by their intrinsic mechanisms. To overcome these limitations, various nanoparticle (NP) systems have been developed to improve the therapeutic efficacy of non-invasive therapies against tumors. This review first summarizes the mechanisms of ROS generation for each non-invasive therapy and their current limitations, with a particular focus on the enhancement strategies for each therapy based on NP systems. Additionally, various strategies to modulate the TME are highlighted. These strategies aim to amplify ROS generation in non-invasive therapies and enhance their anti-tumor efficiency. Finally, the current challenges and possible solutions for the clinical translation of ROS-based non-invasive therapies are also discussed.

Nanoparticle-Mediated Cuproptosis and Photodynamic Synergistic Strategy: A Novel Horizon for Cancer Therapy

BACKGROUND

Photodynamic therapy (PDT) is a noninvasive cancer treatment that works by using light to stimulate the production of excessive cytotoxic reactive oxygen species (ROS), which effectively eliminates tumor cells. However, the therapeutic effects of PDT are often limited by tumor hypoxia, which prevents effective tumor cell elimination. The oxygen (O2) consumption during PDT can further exacerbate hypoxia, leading to post-treatment adverse events.

OBJECTIVES

This review aims to explore the potential of cuproptosis, a recently discovered copper-dependent form of programmed cell death, to enhance the anticancer effects of PDT. Cuproptosis is highly dependent on mitochondrial respiration, specifically the tricarboxylic acid (TCA) cycle, and can increase O2 and ROS levels or decrease glutathione (GSH) levels, thereby improving PDT outcomes.

METHODS

The review discusses the latest research advancements in the field, detailing the mechanisms that regulate cuproptosis and PDT. It also explores how nanoparticle (NP)-based strategies can be used to exploit the synergistic potential between cuproptosis and PDT. The article examines the prospects of synergistic anticancer activity guided by nanodelivery systems, which could overcome the challenges associated with hypoxia in cancer treatment.

CONCLUSIONS

The combination of cuproptosis and PDT, facilitated by NP-based delivery systems, presents a promising approach to enhance the effectiveness of cancer therapy. The review concludes by discussing the challenges and future research directions for this combination therapy, highlighting the need for further investigation into the mechanisms and optimization of treatment strategies to improve outcomes in cancer treatment.

A Redox-Triggered Polymeric Nanoparticle for Disrupting Redox Homeostasis and Enhanced Ferroptosis

Cancer cells possess an efficient redox system, enabling them to withstand oxidative damage induced by treatments, especially in hypoxia areas and ferroptosis can disrupt redox homeostasis in cancer cell. Herein, GSH-sensitive nanoparticles are constructed that induce ferroptosis by long-lasting GSH depletion and enhanced PDT. Carbonic anhydrase IX inhibitor, protoporphyrin IX (Por) complexed with Fe and epirubicin (EPI) are grafted to hyaluronic acid (HA) via disulfide bonds to obtain HSPFE and loaded xCT inhibitor SAS for fabricating SAS@HSPFE which is actively targeted to deep hypoxic tumor cells, and explosively releasing EPI, Por-Fe complex and SAS due to at high GSH concentration. Specifically, SAS inhibited the GSH biosynthesis, and the generation of ROS by Por and the involvement of Fe2+ in the Fenton reaction jointly facilitates oxidative stress. Besides, Fe2+ reacted with excess H2O2 to produce O2, which continuously fuels PDT. GPX4 and SLC7A11 related to antioxidant defense are down-regulated, while ACSL4 and TFRC promoting lipid peroxidation and ROS accumulation are up-regulated, which enhanced ferroptosis by amplifying oxidative stress and suppressing antioxidant defense. SAS@HSPFE NPs revealed highly efficient antitumor effect in vivo study. This study provides a novel approach to cancer treatment by targeting redox imbalance.

Ferroptosis: A novel cell death modality as a synergistic therapeutic strategy with photodynamic therapy

Although there has been significant progress in current comprehensive anticancer treatments centered on surgery, postoperative recurrence and tumor metastasis still significantly affect both prognosis and quality of life of the patient. Hence, the development of precisely targeted tumor therapies and exploration of immunotherapy represent additional strategies for tumor treatment. Photodynamic therapy (PDT) is a relatively safe treatment modality that not only induces multiple modes of tumor cell death but also mediates the secondary immunological responses against tumor resistance and metastasis. Ferroptosis, an iron-dependent type of programmed cell death characterized by accumulation of reactive oxygen species and lipid peroxidation products to lethal levels, has emerged as an attractive target trigger for tumor therapies. Recent research has revealed a close association between PDT and ferroptosis, suggesting that combining ferroptosis inducers with PDT could strengthen their synergistic anti-tumor efficiency. Here in this review, we discuss the rationale for combining PDT with ferroptosis inducers and highlight the progress of single-molecule photosensitizers to induce ferroptosis, as well as the applications of photosensitizers combined with other therapeutic drugs for collaborative therapy. Furthermore, given the current research dilemma, we propose potential therapeutic strategies to advance the combined usage of PDT and ferroptosis inducers, providing the basis and guidelines for prospective clinical translation and research directionality with regard to PDT.

Cell-Penetrating Peptide Like Anti-Programmed Cell Death-Ligand 1 Peptide Conjugate-Based Self-Assembled Nanoparticles for Immunogenic Photodynamic Therapy

The tumor-specific efficacy of the most current anticancer therapeutic agents, including antibody-drug conjugates (ADCs), oligonucleotides, and photosensitizers, is constrained by limitations such as poor cell penetration and low drug delivery. In this study, we addressed these challenges by developing, a positively charged, amphiphilic Chlorin e6 (Ce6)-conjugated, cell-penetrating anti-PD-L1 peptide nanomedicine (CPPD1) with enhanced cell and tissue permeability. The CPPD1 molecule, a bioconjugate of a hydrophobic photosensitizer and strongly positively charged programmed cell death-ligand 1 (PD-L1) binding cell-penetrating peptide (CPP), is capable of self-assembling into nanoparticles with an average size of 199 nm in aqueous solution without the need for any carriers. These carrier-free nanoparticles possess the ability to penetrate the cell membrane of cancer cells and target tumors expressing PD-L1 on their surface. Notably, CPPD1 nanoparticles effectively blocked programmed cell death-1 (PD-1)/PD-L1 interactions and reduced PD-L1 expression via lysosomal degradation. They also demonstrated the responsiveness of CPPD1 nanoparticles in photodynamic therapy (PDT) to a 635 nm laser, leading to the generation of ROS, and induction of various immunogenic cell deaths (ICD). Highly penetrating CPPD1 nanoparticles could immunogenically modulate the microenvironment of CT26 cancer and were also effective in treating abscopal metastatic tumors, addressing major limitations of traditional PDT.

Photodynamic Therapy in Cancer: Principles, State of the Art, and Future Directions

Since its discovery more than 100 years ago, photodynamic therapy (PDT) has become a potent strategy for the treatment of many types of cancer [...].

Platelet membrane biomimetic nanomedicine induces dual glutathione consumption for enhancing cancer radioimmunotherapy

Radiotherapy (RT) is one of the most common treatments for cancer. However, intracellular glutathione (GSH) plays a key role in protecting cancer from radiation damage. Herein, we have developed a platelet membrane biomimetic nanomedicine (PMD) that induces double GSH consumption to enhance tumor radioimmunotherapy. This biomimetic nanomedicine consists of an external platelet membrane and internal organic mesoporous silica nanoparticles (MON) loaded with 2-deoxy-D-glucose (2-DG). Thanks to the tumor-targeting ability of the platelet membranes, PMD can target and aggregate to the tumor site, which is internalized by tumor cells. Within tumor cells overexpressing GSH, MON reacts with GSH to degrade and release 2-DG. This step initially depletes the intracellular GSH content. The subsequent release of 2-DG inhibits glycolysis and adenosine triphosphate (ATP) production, ultimately leading to secondary GSH consumption. This nanodrug combines dual GSH depletion, starvation therapy, and RT to promote immunogenic cell death and stimulate the systemic immune response. In the bilateral tumor model in vivo, distal tumor growth was also well suppressed. The proportion of mature dendritic cells (DC) and CD8+ T cells in the mice was increased. This indicates that PMD can promote anti-tumor radioimmunotherapy and has good prospects for clinical application.

In situ endoscopic photodynamic therapy combined with immature DC vaccination induces a robust T cell response against peritoneal carcinomatosis

BACKGROUND

Immunogenic cell death (ICD) and ferroptosis have recently emerged as key factors in the anticancer immune response. Among the treatments able to induce ICD and the associated release of danger signals is photodynamic therapy (PDT). Ferroptosis for its part results from lipid peroxidation and is induced by CD8+ T cells to kill nearby cancer cells on IFN-γ production. We aimed to combine the two concepts, that is, to evaluate whether the strong pro-oxidant effects of PDT may promote ferroptosis and antigen release and to develop a procedure for in situ PDT to prepare the soil for highly endocytotic immature dendritic cell (iDC) adoptive transfer. This approach was implemented for managing peritoneal carcinomatosis, a lesion often associated with poor outcomes.

METHODS

We used three-dimensional (3D) heterotypic spheroids made of cancer cells, exposed them to a white light-activated OR141 photosensitizer (PS), and subsequently complexified them by adding iDC and naive lymphocytes. We next used a model of mouse peritoneal carcinomatosis and administered PDT using laparoscopy to locally induce photoactivation using the endoscope light. The immune response following adoptive transfer of iDC was tracked both in vivo and ex vivo using isolated immune cells from in situ vaccinated mice.

RESULTS

Cancer cells undergoing PDT-induced cell death significantly increased ICD markers and the infiltration of iDCs in spheroids, relying on ferroptosis. These actions induced the sequential activation of CD8+ and CD4+ T cells as revealed by a significant spheroid 3D structure deterioration and, remarkably, were not recapitulated by conventional ferroptosis inducer RSL3. Using LED light from an endoscope for in situ photoactivation of PS enabled us to apply the vaccination modality in mice with peritoneal tumors. Consecutive intraperitoneal injection of iDCs resulted in delayed tumor growth, increased survival rates, and prevented tumor relapse on rechallenge. CD8+ T cell response was supported by depletion experiments, nodal detection of early activated T cells, and ex vivo T cell-induced cytotoxicity toward spheroids.

CONCLUSIONS

The combination of in situ PDT locally delivered by an endoscope light and iDC administration induces a durable memory immune response against peritoneal carcinomatosis thereby opening new perspectives for the treatment of a life-threatening condition.

Bionic aggregation-induced emission photosensitizer for enhanced cancer immunotherapy

Cold exposure therapy (CE), as an inexpensive method, has shown great potential in cancer therapy. Exploring the combined anti-tumor mechanism of CE and traditional therapies (such as photodynamic therapy (PDT)) is exciting and promising. Here, a bionic aggregation-induced emission photosensitizer system (named THL) is designed for combined CE to enhance anti-tumor immunotherapy. THL inherits the homologous targeting ability of tumor derived exosomes, promoting the enrichment of THL at the tumor site. Under external illumination, THL generates hydroxyl radicals and superoxide anions through type I PDT. In addition, mice are pretreated with cold exposure, which promotes THL mediated PDT and reactive oxygen species (ROS) generation by reducing the production of ATP and GSH in tumor tissue. This combination therapy increases production of ROS within the tumor, inhibits the growth of distant tumors, recurrent and rechallenged tumors and increases the number of cytotoxic CD8+T cells and memory T cells. Compared to PDT alone, combination therapy shows greater advantages in tumor immunotherapy. The combination therapy strategy provides new ideas for cancer immunotherapy.

Platelet membrane-coated oncolytic vaccinia virus with indocyanine green for the second near-infrared imaging guided multi-modal therapy of colorectal cancer

Colorectal cancer (CRC) is a prevalent malignancy with insidious onset and diagnostic challenges, highlighting the need for therapeutic approaches to enhance theranostic outcomes. In this study, we elucidated the unique temperature-resistant properties of the oncolytic vaccinia virus (OVV), which can synergistically target tumors under photothermal conditions. To capitalize on this characteristic, we harnessed the potential of the OVV by surface-loading it with indocyanine green (ICG) and encapsulating it within a platelet membrane (PLTM), resulting in the creation of PLTM-ICG-OVV (PIOVV). This complex seamlessly integrates virotherapy, photodynamic therapy (PDT), and photothermal therapy (PTT). The morphology, size, dispersion stability, optical properties, and cellular uptake of PIOVV were evaluated using transmission electron microscopy (TEM). In vitro and in vivo experiments revealed specificity of PIOVV for cancer cells; it effectively induced apoptosis and suppressed CT26 cell proliferation. In mouse models, PIOVV exhibits enhanced fluorescence at tumor sites, accompanied by prolonged blood circulation. Under 808 nm laser irradiation, PIOVV significantly inhibited tumor growth. This strategy holds the potential for advancing phototherapy, oncolytic virology, drug delivery, and tumor-specific targeting, particularly in the context of CRC theranostics.

Sequential dual-locking strategy using photoactivated Pt(IV)-based metallo-nano prodrug for enhanced chemotherapy and photodynamic efficacy by triggering ferroptosis and macrophage polarization

Selective activation of Pt(IV) prodrugs within tumors has emerged as a promising strategy in tumor treatment. Although progress has been made with photo- and ultrasound-activated Pt(IV) prodrugs, concerns remain over the non-specific activation of photosensitizers (PS) and the potential for phototoxicity and chemical toxicity. In this study, a sequential dual-locked Pt(IV) nano-prodrug that can be activated by both the acidic tumor microenvironment and light was developed. The Pt(IV) prodrug was prepared by conjugating PS-locked Pt(IV) to a polymeric core, which was then chelated with metallo iron to lock its photoactivity and form a metallo-nano prodrug. Under acidic tumor microenvironment conditions, the metallo-nano prodrug undergoes dissociation of iron, triggering a reduction process in oxaliplatin under light irradiation, resulting in the activation of both chemotherapy and photodynamic therapy (PDT). Additionally, the prodrug could induce metallo-triggered ferroptosis and polarization of tumor-associated macrophages (TAM), thereby enhancing tumor inhibition. The dual-lock strategy employed in a nanoparticle delivery system represents an expansion in the application of platinum-based anticancer drugs, making it a promising new direction in cancer treatment.

Ferroptosis in Cancer Therapy: Mechanisms, Small Molecule Inducers, and Novel Approaches

Ferroptosis, a unique form of programmed cell death, is initiated by an excess of iron accumulation and lipid peroxidation-induced damage. There is a growing body of evidence indicating that ferroptosis plays a critical role in the advancement of tumors. The increased metabolic activity and higher iron levels in tumor cells make them particularly vulnerable to ferroptosis. As a result, the targeted induction of ferroptosis is becoming an increasingly promising approach for cancer treatment. This review offers an overview of the regulatory mechanisms of ferroptosis, delves into the mechanism of action of traditional small molecule ferroptosis inducers and their effects on various tumors. In addition, the latest progress in inducing ferroptosis using new means such as proteolysis-targeting chimeras (PROTACs), photodynamic therapy (PDT), sonodynamic therapy (SDT) and nanomaterials is summarized. Finally, this review discusses the challenges and opportunities in the development of ferroptosis-inducing agents, focusing on discovering new targets, improving selectivity, and reducing toxic and side effects.

Surufatinib combined with photodynamic therapy induces ferroptosis to inhibit cholangiocarcinoma in vitro and in tumor models

The curative effect of single therapy for advanced cholangiocarcinoma (CCA) is poor, thus investigating combined treatment strategies holds promise for improving prognosis. Surufatinib (SUR) is a novel multikinase inhibitor that has been confirmed to prolong survival of patients with advanced CCA. Photodynamic therapy (PDT) can also ablate advanced CCA and relieve biliary obstruction. In this study, we explored the anti-CCA effect of SUR combined with PDT, and explored the underlying mechanism. We found that SUR could effectively inhibit the abilities of proliferation, migration and metastasis in CCA cells (HUCCT-1, RBE). The ability of SUR to inhibit CCA was also confirmed by the HUCCT-1 cell xenograft model in Balb/c nude mice and CCA patient-derived organoids. SUR combined with PDT can significantly enhance the inhibitory effect on CCA, and can be alleviated by two ferroptosis inhibitors (Ferrostatin-1, Deferoxamine). By detecting the level of reactive oxygen species, lipid peroxides, malondialdehyde and glutathione, we further confirmed that SUR combined with PDT can inhibit CCA cells by inducing ferroptosis. Glutathione peroxidase 4 (GPX4) belongs to the glutathione peroxidase family and is mainly responsible for the metabolism of intracellular hydrogen peroxide. GPX4 inhibits ferroptosis by reducing cytotoxic lipid peroxides (L-OOH) to the corresponding alcohols (L-OH). Acyl-CoA synthetase long-chain family member 4 (ACSL4) is a member of the long-chain fatty acid coenzyme a synthetase family and is mainly involved in the biosynthesis and catabolism of fatty acids. ACSL4 induces ferroptosis by promoting the accumulation of lipid peroxides. Both SUR and PDT can induce ferroptosis by promoting ACSL4 and inhibiting GPX4. The regulation effect is found to be more significant in combined treatment group. In conclusion, SUR combined with PDT exerted an anti-CCA effect by inducing ferroptosis. Combination therapy provides a new idea for the clinical treatment of CCA.

A carrier-free tri-component nanoreactor for multi-pronged synergistic cancer therapy

Non-invasive therapies such as photodynamic therapy (PDT) and chemodynamic therapy (CDT) have received wide attention due to their low toxicity and side effects, but their efficacy is limited by the tumor microenvironment (TME), and monotherapy cannot achieve satisfactory efficacy. In this work, a multifunctional nanoparticle co-assembled from oleanolic acid (OA), chlorin e6 (Ce6) and hemin was developed. The as-constructed nanoparticle named OCH with diameters of around 130 nm possessed good biostability, pH/GSH dual-responsive drug release properties, and remarkable cellular internalization and tumor accumulation capabilities. OCH exhibited prominent catalytic activities to generate •OH, deplete GSH, and produce O2 to overcome the hypoxia TME, thus potentiating the photodynamic and chemodynamic effect. In addition, OCH can induce the occurrence of ferroptosis in both ferroptosis-sensitive and ferroptosis-resistant cancer cells. The multi-pronged effects of OCH including hypoxia alleviation, GSH depletion, ferroptosis induction, CDT and PDT effects jointly facilitate excellent anticancer effects in vitro and in vivo. Hence, this work will advance the development of safe and effective clinically transformable nanomedicine by employing clinically-applied agents to form drug combinations for efficient multi-pronged combination cancer therapy.

Ce6-modified Fe ions-doped carbon dots as multifunctional nanoplatform for ferroptosis and photodynamic synergistic therapy of melanoma

BACKGROUND

Despite the higher sensitivity of melanoma towards ferroptosis and photodynamic therapy (PDT), the lack of efficient ferroptosis inducers and the poor solubility of photosensitizers restrict their synergistic strategies. With unique advantages, carbon dots (CDs) are expected to serve as innovative building blocks for combination therapy of cancers.

RESULTS

Herein, an ferroptosis/PDT integrated nanoplatform for melanoma therapy is constructed based on chlorin e6-modified Fe ions-doped carbon dots (Fe-CDs@Ce6). As a novel type of iron-carbon hybrid nanoparticles, the as-prepared Fe-CDs can selectively activate ferroptosis, prevent angiogenesis and inhibit the migration of mouse skin melanoma cells (B16), but have no toxicity to normal cells. The nano-conjugated structures facilitate not only the aqueous dispersibility of Ce6, but also the self-accumulation ability of Fe-CDs@Ce6 within melanoma area without requiring extra targets. Moreover, the therapeutic effects of Fe-CDs@Ce6 are synergistically enhanced due to the increased GSH depletion by PDT and the elevated singlet oxygen (1O2) production efficiency by Fe-CDs. When combined with laser irradiation, the tumor growth can be significantly suppressed by Fe-CDs@Ce6 through cyclic administration. The T2-weighted magnetic resonance imaging (MRI) capability of Fe-CDs@Ce6 also reveals their potentials for cancer diagnosis and navigation therapy.

CONCLUSIONS

Our findings indicate the multifunctionality of Fe-CDs@Ce6 in effectively combining ferroptosis/PDT therapy, tumor targeting and MRI imaging, which enables Fe-CDs@Ce6 to become promising biocompatible nanoplatform for the treatment of melanoma.

The application of nanoparticles-based ferroptosis, pyroptosis and autophagy in cancer immunotherapy

Immune checkpoint blockers (ICBs) have been applied for cancer therapy and achieved great success in the field of cancer immunotherapy. Nevertheless, the broad application of ICBs is limited by the low response rate. To address this issue, increasing studies have found that the induction of immunogenic cell death (ICD) in tumor cells is becoming an emerging therapeutic strategy in cancer treatment, not only straightly killing tumor cells but also enhancing dying cells immunogenicity and activating antitumor immunity. ICD is a generic term representing different cell death modes containing ferroptosis, pyroptosis, autophagy and apoptosis. Traditional chemotherapeutic agents usually inhibit tumor growth based on the apoptotic ICD, but most tumor cells are resistant to the apoptosis. Thus, the induction of non-apoptotic ICD is considered to be a more efficient approach for cancer therapy. In addition, due to the ineffective localization of ICD inducers, various types of nanomaterials have been being developed to achieve targeted delivery of therapeutic agents and improved immunotherapeutic efficiency. In this review, we briefly outline molecular mechanisms of ferroptosis, pyroptosis and autophagy, as well as their reciprocal interactions with antitumor immunity, and then summarize the current progress of ICD-induced nanoparticles based on different strategies and illustrate their applications in the cancer therapy.

Lipid peroxidation of immune cells in cancer

Growing evidence indicates that cellular metabolism is a critical determinant of immune cell viability and function in antitumor immunity and lipid metabolism is important for immune cell activation and adaptation to the tumor microenvironment (TME). Lipid peroxidation is a process in which oxidants attack lipid-containing carbon-carbon double bonds and is an important part of lipid metabolism. In the past decades, studies have shown that lipid peroxidation participates in signal transduction to control cell proliferation, differentiation, and cell death, which is essential for cell function execution and human health. More importantly, recent studies have shown that lipid peroxidation affects immune cell function to modulate tumor immunity and antitumor ability. In this review, we briefly overview the effect of lipid peroxidation on the adaptive and innate immune cell activation and function in TME and discuss the effectiveness and sensitivity of the antitumor ability of immune cells by regulating lipid peroxidation.

Metal-based nanoparticles in cancer therapy: Exploring photodynamic therapy and its interplay with regulated cell death pathways

Photodynamic therapy (PDT) represents a non-invasive treatment strategy currently utilized in the clinical management of selected cancers and infections. This technique is predicated on the administration of a photosensitizer (PS) and subsequent irradiation with light of specific wavelengths, thereby generating reactive oxygen species (ROS) within targeted cells. The cellular effects of PDT are dependent on both the localization of the PS and the severity of ROS challenge, potentially leading to the stimulation of various cell death modalities. For many years, the concept of regulated cell death (RCD) triggered by photodynamic reactions predominantly encompassed apoptosis, necrosis, and autophagy. However, in recent decades, further explorations have unveiled additional cell death modalities, such as necroptosis, ferroptosis, cuproptosis, pyroptosis, parthanatos, and immunogenic cell death (ICD), which helps to achieve tumor cell elimination. Recently, nanoparticles (NPs) have demonstrated substantial advantages over traditional PSs and become important components of PDT, due to their improved physicochemical properties, such as enhanced solubility and superior specificity for targeted cells. This review aims to summarize recent advancements in the applications of different metal-based NPs as PSs or delivery systems for optimized PDT in cancer treatment. Furthermore, it mechanistically highlights the contribution of RCD pathways during PDT with metal NPs and how these forms of cell death can improve specific PDT regimens in cancer therapy.

The application of nanoparticles based on ferroptosis in cancer therapy

Ferroptosis is a new form of non-apoptotic programmed cell death. Due to its effectiveness in cancer treatment, there are increasing studies on the application of nanoparticles based on ferroptosis in cancer therapy. In this paper, we present a summary of the latest progress in nanoparticles based on ferroptosis for effective tumor therapy. We also describe the combined treatment of ferroptosis with other therapies, including chemotherapy, radiotherapy, phototherapy, immunotherapy, and gene therapy. This summary of drug delivery systems based on ferroptosis aims to provide a basis and inspire opinions for researchers concentrating on exploring this field. Finally, we present some prospects and challenges for the application of nanotherapies to clinical treatment by promoting ferroptosis in cancer cells.

BASHY Dyes Are Highly Efficient Lipid Droplet-Targeting Photosensitizers that Induce Ferroptosis through Lipid Peroxidation

Ferroptosis is an iron-dependent lipid-peroxidation-driven mechanism of cell death and a promising therapeutic target to eradicate cancer cells. In this study, we discovered that boronic acid-derived salicylidenehydrazone (BASHY) dyes are highly efficient singlet-oxygen photosensitizers (PSs; ΦΔ up to 0.8) that induce ferroptosis triggered by photodynamic therapy. The best-performing BASHY dye displayed a high phototoxicity against the human glioblastoma multiform U87 cell line, with an IC50 value in the low nanomolar range (4.40 nM) and a remarkable phototoxicity index (PI > 22,700). Importantly, BASHY dyes were shown to accumulate in lipid droplets (LDs) and this intracellular partition was found to be essential for the enhanced phototoxicity and the induction of ferroptosis through lipid peroxidation. The safety and phototoxicity of this platform were validated using an in vivo zebrafish model (Danio rerio).

Gold standard assessment of immunogenic cell death induced by photodynamic therapy: From in vitro to tumor mouse models and anti-cancer vaccination strategies

The discovery of the concept of immunogenic cell death (ICD) is a cornerstone in the development of novel anti-cancer immunotherapeutic approaches. Induction of the ICD pathway by specific anti-cancer therapeutic regimens can eliminate cancer cells by directly killing them during therapy and by activation of strong and specific anti-cancer immunity, leading to a long-lasting immunological memory that prevents cancer recurrence. ICD encompasses different forms of regulated cell death and can be triggered by many anti-cancer treatment modalities, including photodynamic therapy (PDT). PDT is a multistep procedure involving the accumulation of a light-sensitive dye known as a photosensitizer (PS) in tumor cells, followed by its activation by irradiation with a light of an appropriate wavelength. In the presence of molecular oxygen, the irradiated PS leads to the generation of cytotoxic reactive oxygen species, which can lead to ICD induction in the cancer cells. Here, we first describe in vitro methods to help optimize the PDT procedure for a specific PS. We also provide a collection of protocols and techniques for assessing ICD in vitro, including analysis of the emission of damage associated molecular patterns (DAMPs), efferocytosis, and the maturation and activation state of antigen presenting cells. Next, we describe in detail protocols for diverse tumor mouse models for assessing and characterizing ICD in vivo, such as murine tumor vaccination models. Finally, as an immunotherapeutic vaccine, we suggest using either PDT-induced dead cancer cells, preferably undergoing ICD, or dendritic cells loaded with lysates of PDT-induced cancer cells in a syngeneic orthotopic glioma model. Overall, this methodological article provides a quantitative, comprehensive set of validated tools that can be successfully used, with some adaptations, to identify, optimize and validate novel PSs in vitro and in vivo for the efficient induction of ICD during photodynamic treatment.

Photodynamic Therapy Combined with Ferroptosis Is a Synergistic Antitumor Therapy Strategy

Ferroptosis is a programmed death mode that regulates redox homeostasis in cells, and recent studies suggest that it is a promising mode of tumor cell death. Ferroptosis is regulated by iron metabolism, lipid metabolism, and intracellular reducing substances, which is the mechanism basis of its combination with photodynamic therapy (PDT). PDT generates reactive oxygen species (ROS) and 1O2 through type I and type II photochemical reactions, and subsequently induces ferroptosis through the Fenton reaction and the peroxidation of cell membrane lipids. PDT kills tumor cells by generating excessive cytotoxic ROS. Due to the limited laser depth and photosensitizer enrichment, the systemic treatment effect of PDT is not good. Combining PDT with ferroptosis can compensate for these shortcomings. Nanoparticles constructed by photosensitizers and ferroptosis agonists are widely used in the field of combination therapy, and their targeting and biological safety can be improved through modification. These nanoparticles not only directly kill tumor cells but also further exert the synergistic effect of PDT and ferroptosis by activating antitumor immunity, improving the hypoxia microenvironment, and inhibiting the tumor angiogenesis. Ferroptosis-agonist-induced chemotherapy and PDT-induced ablation also have good clinical application prospects. In this review, we summarize the current research progress on PDT and ferroptosis and how PDT and ferroptosis promote each other.

Application of singlet oxygen-activatable nanocarriers to boost X-ray-induced photodynamic therapy and cascaded ferroptosis for breast cancer treatment

Ferroptosis has appealing antitumor potential that is mainly based on the accumulation of lipid peroxide to a lethal level. The cytotoxic singlet oxygen (1O2) generated from nanoscale X-ray-induced photodynamic therapy (X-PDT) may facilitate glutathione (GSH) depletion and further activate ferroptosis. To realize combined X-PDT and ferroptosis, a nanocarrier (D-NPVR) was engineered with a hyperbranched copolymer with 1O2-sensitive linkers, where both the photosensitizer (verteporfin) and ferroptosis inducer RAS-selective lethal small molecule 3 (RSL3) were encapsulated. Upon X-ray radiation, D-NPVR could produce a large amount of 1O2 for apoptosis. Subsequently, 1O2 triggered D-NP dissociation by cleavage of 1,2-bis(2-hydroxyethylthio)ethylene bonds to boost payload release and decrease levels of intracellular GSH via thiol oxidation. Liberated RSL3 is a covalent inhibitor for glutathione peroxide 4 (GPX4), which is responsible for detoxifying lipid peroxides to lipid alcohols with GSH assistance, and both 1O2-induced GSH depletion and GPX4 inactivation thereby produced ferroptotic cell death. Tumor growth inhibition in murine 4T1 tumor-bearing mice demonstrated that D-NPVR produced pronounced therapeutic efficiency where ferroptosis induction was supported by the GPX4 content and expression. This study highlights the contribution of 1O2-sensitive nanocarriers for promoting the potency of combined X-PDT and ferroptosis.

Exosome camouflaged coordination-assembled Iridium(III) photosensitizers for apoptosis-autophagy-ferroptosis induced combination therapy against melanoma

Melanoma represents the most fatal form of skin cancer due to its resistance mechanisms and high capacity for the development of metastases. Among other medicinal techniques, photodynamic therapy is receiving increasing attention. Despite promising results, the application of photodynamic therapy is inherently limited due to interference from melanin, poor tissue penetration of photosensitizers, low loading into drug delivery systems, and a lack of tumor selectivity. To overcome these limitations, herein, the coordination-driven assembly of Ir(III) complex photosensitizers with Fe(III) ions into nanopolymers for combined photodynamic therapy and chemodynamic therapy is reported. While remaining stable under physiological conditions, the nanopolymers dissociated in the tumor microenvironment. Upon exposure to light, the Ir(III) complexes produced singlet oxygen and superoxide anion radicals, inducing cell death by apoptosis and autophagy. The Fe(III) ions were reduced to Fe(II) upon depletion of glutathione and reduction of the GPX4 levels, triggering cell death by ferroptosis. To provide tumor selectivity, the nanopolymers were further camouflaged with exosomes. The generated nanoparticles were found to eradicate a melanoma tumor as well as inhibit the formation of metastases inside a mouse model.

Metal-Based Photosensitizers as Inducers of Regulated Cell Death Mechanisms

Over the last few decades, various forms of regulated cell death (RCD) have been discovered and were found to improve cancer treatment. Although there are several reviews on RCD induced by photodynamic therapy (PDT), a comprehensive summary covering metal-based photosensitizers (PSs) as RCD inducers has not yet been presented. In this review, we systematically summarize the works on metal-based PSs that induce different types of RCD, including ferroptosis, immunogenic cell death (ICD), and pyroptosis. The characteristics and mechanisms of each RCD are explained. At the end of each section, a summary of the reported commonalities between different metal-based PSs inducing the same RCD is emphasized, and future perspectives on metal-based PSs inducing novel forms of RCD are discussed at the end of the review. Considering the essential roles of metal-based PSs and RCD in cancer therapy, we hope that this review will provide the stage for future advances in metal-based PSs as RCD inducers.

Hydrazide/Metal/Indocyanine Green Coordinated Nanoplatform for Potentiating Reciprocal Ferroptosis and Immunity against Melanoma

Ferroptosis holds great potential in cancer treatment, but its efficacy is severely limited by a low Fenton reaction efficacy. Meanwhile, the interactive relationship between Ferroptosis and the PD-1 blockade is still vague. Herein, a hydrazide/Cu/Fe/indocyanine green coordinated nanoplatform (TCFI) is constructed by a hydrazide-metal-sulfonate coordination process. The TCFI nanoplatform exhibits Fenton-/catalase-/glutathione oxidase-like triple activities and accordingly can trigger lipid peroxidation, relieve hypoxia, and downregulate the glutathione/glutathione peroxidase 4 axis, thus achieving positively and negatively dually enhanced Ferroptosis in B16F10 cancer cells. Under near-infrared laser irradiation, the TCFI nanoplatform induces robust immunogenic cancer cell death by elevating the intracellular reactive oxygen species level through synergistic photodynamic therapy/Ferroptosis, which significantly potentiates CD8+ T cell infiltration into tumors and interferon-γ secretion. Moreover, upregulated interferon-γ efficiently inhibits system xc- activity and sensitizes cancer cells to Ferroptosis. Interestingly, the PD-1 blockade may strengthen the reciprocal process. The combination of the TCFI nanoplatform and αPD-1 can eliminate primary tumors and inhibit distant tumor growth, lung metastasis, and tumor recurrence. This study presents a simple and novel coordination strategy to fabricate tumor microenvironment-responsive nanodrugs and highlights the enhancement effect of photodynamic therapy on reciprocal Ferroptosis and antitumor immunity.

Nanoparticle-mediated synergistic anticancer effect of ferroptosis and photodynamic therapy: Novel insights and perspectives

Current antitumor monotherapy has many limitations, highlighting the need for novel synergistic anticancer strategies. Ferroptosis is an iron-dependent form of nonapoptotic cell death that plays a pivotal regulatory role in tumorigenesis and treatment. Photodynamic therapy (PDT) causes irreversible chemical damage to target lesions and is widely used in antitumor therapy. However, PDT's effectiveness is usually hindered by several obstacles, such as hypoxia, excess glutathione (GSH), and tumor resistance. Ferroptosis improves the anticancer efficacy of PDT by increasing oxygen and reactive oxygen species (ROS) or reducing GSH levels, and PDT also enhances ferroptosis induction due to the ROS effect in the tumor microenvironment (TME). Strategies based on nanoparticles (NPs) can subtly exploit the potential synergy of ferroptosis and PDT. This review explores recent advances and current challenges in the landscape of the underlying mechanisms regulating ferroptosis and PDT, as well as nano delivery system-mediated synergistic anticancer activity. These include polymers, biomimetic materials, metal organic frameworks (MOFs), inorganics, and carrier-free NPs. Finally, we highlight future perspectives of this novel emerging paradigm in targeted cancer therapies.

Autophagy Regulation Using Multimodal Chlorin e6-Loaded Polysilsesquioxane Nanoparticles to Improve Photodynamic Therapy

Photodynamic therapy (PDT) is a promising anticancer noninvasive technique that relies on the generation of reactive oxygen species (ROS). Unfortunately, PDT still has many limitations, including the resistance developed by cancer cells to the cytotoxic effect of ROS. Autophagy, which is a stress response mechanism, has been reported as a cellular pathway that reduces cell death following PDT. Recent studies have demonstrated that PDT in combination with other therapies can eliminate anticancer resistance. However, combination therapy is usually challenged by the differences in the pharmacokinetics of the drugs. Nanomaterials are excellent delivery systems for the efficient codelivery of two or more therapeutic agents. In this work, we report on the use of polysilsesquioxane (PSilQ) nanoparticles for the codelivery of chlorin-e6 (Ce6) and an autophagy inhibitor for early- or late-stage autophagy. Our results, obtained from a reactive oxygen species (ROS) generation assay and apoptosis and autophagy flux analyses, demonstrate that the reduced autophagy flux mediated by the combination approach afforded an increase in the phototherapeutic efficacy of Ce6-PSilQ nanoparticles. We envision that the promising results in the use of multimodal Ce6-PSilQ material as a codelivery system against cancer pave the way for its future application with other clinically relevant combinations.

Recent Organic Photosensitizer Designs for Evoking Proinflammatory Regulated Cell Death in Antitumor Immunotherapy

In the past decades, immunotherapy has achieved a series of clinical successes in the field of cancer. However, existing therapeutic options usually show a low immune response to solid tumors caused by immunosuppressive "cold" tumor microenvironment (TME). Several types of proinflammatory regulated cell death (RCD), mainly including ferroptosis and pyroptosis, have been studied recently, which can provide proinflammatory signals and immunogenicity necessary for remodeling TME and activating an antitumor immune response. A variety of chemotherapeutic drugs are proven to be effective in the proinflammatory RCD induction of tumor cells, but several adverse effects and intrinsic drug resistance usually occur in the therapeutic process, greatly hindering their further clinical application. The emerging organic photosensitizer (PS)-based materials open new possibilities to effectively activate proinflammatory RCD through precise spatiotemporal regulation of intracellular reactive oxygen species-associated signaling pathways, which can overcome many challenges encountered in current proinflammatory RCD-mediated immunotherapy. In this review, the recent design strategies of PS probes are detailly summarized and their potential advantages for tumor-specific proinflammatory RCD induction are discussed. Moreover, the representative examples in cancer immunotherapy are highlighted and future perspectives in this emerging field are proposed.

Mitochondria-Targeted Nanosystem with Reactive Oxygen Species-Controlled Release of CO to Enhance Photodynamic Therapy of PCN-224 by Sensitizing Ferroptosis

The apoptosis-resistant mechanism of photodynamic therapy (PDT) usually results in limited therapeutic efficacy. The development of new strategies for sensitizing targeted ferroptosis that bypass apoptosis resistance is of great significance to improve the antitumor efficacy of PDT. In this study, a novel amphiphilic copolymer whose main chain contains reactive oxygen species (ROS)-responsive groups and the end of side chains contains triphenylphosphine is synthesized, to encapsulate porphyrinic metal-organic framework PCN-224 via self-assembly which are hydrothermally synthesized by coordination of zirconium (IV) with tetra-kis(4-caboxyphenyl) porphyrin, and loaded carbon monoxide releasing molecule 401 (CORM-401) by their hollow structures (PCN-CORM), and finally, surface-coated with hyaluronic acid. The nanosystem can sequentially localize to mitochondria which is an important target to induce apoptosis and ferroptosis in cancer cells. Upon excitation with near-infrared light, PCN-224 is activated to produce amounts of ROS, and simultaneously triggers the rapid intracellular release of CO. More importantly, the released CO can sensitize ferroptosis and promote apoptosis to significantly enhance the antitumor efficacy of PCN-224 both in vitro and in vivo. These results illustrate that the mitochondria-targeted drug delivery system combined PDT with CO leads to an effective antitumor efficacy, which maybe a promising way to enhance the treatment efficiency of PDT.

Photon-Controlled Pyroptosis Activation (PhotoPyro): An Emerging Trigger for Antitumor Immune Response

Pyroptosis refers to the process of gasdermin-mediated lytic programmed cell death (PCD) characterized by the release of pro-inflammatory cytokines. Our knowledge of pyroptosis has expanded beyond the cellular level and now includes extracellular responses. In recent years, pyroptosis has attracted considerable attention due to its potential to induce host immunity. For instance, at the 2022 International Medicinal Chemistry of Natural Active Ligand Metal-Based Drugs (MCNALMD) conference, numerous researchers demonstrated an interest in photon-controlled pyroptosis activation ("PhotoPyro"), an emerging pyroptosis-engineered approach for activating systemic immunity via photoirradiation. Given this enthusiasm, we share in this Perspective our views on this emerging area and expound on how and why "PhotoPyro" could trigger antitumor immunity (i.e., turning so-called "cold" tumors "hot"). In doing so, we have tried to highlight cutting-edge breakthroughs in PhotoPyro while suggesting areas for future contributions. By providing insights into the current state of the art and serving as a resource for individuals interested in working in this area, it is hoped that this Perspective will set the stage for PhotoPyro to evolve into a broadly applicable cancer treatment strategy.

Nanomedicine-mediated ferroptosis targeting strategies for synergistic cancer therapy

Apoptosis-based treatment plays an important role in regulating the death of tumor cells (e.g., chemotherapy, radiotherapy, and immunotherapy). Nevertheless, cancer cells can escape surveillance from apoptosis-associated signaling by bypassing other biological pathways and thus result in considerable resistance to therapies. Significantly, ferroptosis, a newly identified type of regulated cell death that is characterized by iron-dependent and lipid peroxidation accumulation, has aroused great research interest in cancer therapy. Increasing approaches have been developed to induce ferroptosis of tumor cells, including using clinically approved drugs, experimentally used compounds, and nanomedicine formulations. More importantly, the emerging nanomedicine-based strategy has made great advances in tumor treatment because of the promising targeting efficacy and enhanced therapeutic effects. In this review, we mainly overview state-of-the-art research on nanomedicine-mediated ferroptosis targeting strategies for synergistic cancer therapies, such as immunotherapy, chemotherapy, radiotherapy, and photothermal therapy. The potential targeting mechanism of nanomedicine for ferroptosis induction was also included. Finally, the future development of nanomedicine in the field of ferroptosis-based cell death in tumor treatment will be envisioned, aiming to provide new insight for tumor treatment in the clinic.

Ferroptosis: challenges and opportunities for nanomaterials in cancer therapy

Ferroptosis, a completely new form of regulated cell death, is mainly caused by an imbalance between oxidative damage and reductive protection and has shown great anti-cancer potential. However, existing small-molecule ferroptosis inducers have various limitations, such as poor water solubility, drug resistance and low targeting ability, hindering their clinical applications. Nanotechnology provides new opportunities for ferroptosis-driven tumor therapy. Especially, stimuli-responsive nanomaterials stand out among others and have been widely researched because of their unique spatiotemporal control advantages. Therefore, it's necessary to summarize the application of those stimuli-responsive nanomaterials in ferroptosis. Here, we describe the physiological feature of ferroptosis and illustrate the current challenges to induce ferroptosis for cancer therapy. Then, nanomaterials that induce ferroptosis are classified and elaborated according to the external and internal stimuli. Finally, the future perspectives in the field are proposed. We hope this review facilitates paving the way for the design of intelligent nano-ferroptosis inducers.

DC vaccines loaded with glioma cells killed by photodynamic therapy induce Th17 anti-tumor immunity and provide a four-gene signature for glioma prognosis

Gliomas, the most frequent type of primary tumor of the central nervous system in adults, results in significant morbidity and mortality. Despite the development of novel, complex, multidisciplinary, and targeted therapies, glioma therapy has not progressed much over the last decades. Therefore, there is an urgent need to develop novel patient-adjusted immunotherapies that actively stimulate antitumor T cells, generate long-term memory, and result in significant clinical benefits. This work aimed to investigate the efficacy and molecular mechanism of dendritic cell (DC) vaccines loaded with glioma cells undergoing immunogenic cell death (ICD) induced by photosens-based photodynamic therapy (PS-PDT) and to identify reliable prognostic gene signatures for predicting the overall survival of patients. Analysis of the transcriptional program of the ICD-based DC vaccine led to the identification of robust induction of Th17 signature when used as a vaccine. These DCs demonstrate retinoic acid receptor-related orphan receptor-γt dependent efficacy in an orthotopic mouse model. Moreover, comparative analysis of the transcriptome program of the ICD-based DC vaccine with transcriptome data from the TCGA-LGG dataset identified a four-gene signature (CFH, GALNT3, SMC4, VAV3) associated with overall survival of glioma patients. This model was validated on overall survival of CGGA-LGG, TCGA-GBM, and CGGA-GBM datasets to determine whether it has a similar prognostic value. To that end, the sensitivity and specificity of the prognostic model for predicting overall survival were evaluated by calculating the area under the curve of the time-dependent receiver operating characteristic curve. The values of area under the curve for TCGA-LGG, CGGA-LGG, TCGA-GBM, and CGGA-GBM for predicting five-year survival rates were, respectively, 0.75, 0.73, 0.9, and 0.69. These data open attractive prospects for improving glioma therapy by employing ICD and PS-PDT-based DC vaccines to induce Th17 immunity and to use this prognostic model to predict the overall survival of glioma patients.

Activation of ALOX12 by a multi-organelle-orienting photosensitizer drives ACSL4-independent cell ferroptosis

Ferroptosis is a recently-defined tumor suppression mechanism, but the sensitivity of many tumorigenic cells to ferroptosis is limited by their deficient expression of acyl-CoA synthetase long-chain family member 4 (ACSL4). Here, we report the discovery of a photosensitizer, namely TPCI, which can evoke ACSL4-independent ferroptosis of cancer cells in photodynamic therapy. Through co-localization with 12-lipoxygenase (ALOX12) in multiple subcellular organelles, TPCI activates ALOX12 to generate lipid reactive oxygen species in large quantity and trigger cell ferroptosis. Intriguingly, confining TPCI exclusively in lysosomes switches the cell death from ferroptosis to apoptosis. More strikingly, the ferroptosis mediated by TPCI-induced ALOX12 activation does not require the participation of ACSL4. Therefore, our study identifies TPCI as the first ALOX12 activator to induce ferroptosis independent of ACSL4, which renders a viable therapeutic approach on the basis of distinct ferroptosis of cancer cells, regardless their ACSL4 expressions.

Identification of a signature based on non‐apoptotic regulatory cell death to improve prognosis prediction in acute myeloid leukaemia

Although anti-apoptotic cell death is a common feature of cancer and non-apoptotic regulatory cell death (RCD) is highly correlated with cancer progression and response to therapy, its prognostic role in patients with acute myeloid leukaemia (AML) is unknown. The RNA sequence and clinical data from AML patients were downloaded from the TCGA and GEO databases. The prognostic characteristics of non-apoptotic RCD-related genes (NRGs) were determined by Cox and LASSO regression analysis. Thirteen NRG signatures were identified as independent prognostic parameters in patients with AML that outperformed other prognostic models. Higher NRG scores were associated with shorter survival and less retention of tumour mutations. Although patients with high NRG risk have abundant signalling pathways for cell adhesion, cytokine upregulation, and cellular defence responses, patients with low NRG risk may benefit the most from immunotherapy. Specifically, patients with high NRG score may benefit from treatment with anti-EGFR and CDK2 inhibitors, including erlotinib and roscovitine. The NPM1 and FLT3 mutant cell lines undergo alterations after multiple drug treatments. Our established NRG signature and scoring highlight its vital clinical significance, emphasize the inevitability of stratifying treatment for different mutation subtypes and provide new ideas to guide personalized immunotherapy strategies for AML patients.

Ferritin-Hijacking Nanoparticles Spatiotemporally Directing Endogenous Ferroptosis for Synergistic Anticancer Therapy

Existing ferroptosis as an iron-dependent form of regulated cell death primarily relies on importing exogenous iron. However, the excessive employment of toxic materials may cause potential adverse effects on human health. Herein, a ferritin-hijacking nanoparticle (Ce6-PEG-HKN₁₅ ) is fabricated, by conjugating the ferritin-homing peptide HKN₁₅ with the photosensitizer chlorin e6 (Ce6) for endogenous ferroptosis without introducing Fenton-reactive metals. Once internalized, the designed Ce6-PEG-HKN₁₅ NPs can specifically accumulate around ferritin. With laser irradiation, the activated Ce6 in nanoparticles potently generates reactive oxygen species (ROS) surrounding ferritin. Abundant ROS not only helps to destroy the iron storage protein and activate endogenous ferroptosis but also directly kill tumor cells. In turn, the released iron partially interacts with intracellular excess H₂ O₂ to produce O₂ , thereby enhancing photodynamic therapy and further amplifying oxidative stress. Overall, this work highlights the possibility of endogenous ferroptosis via spatiotemporally destroying ferritin, offering a paradigm for synergistic ferroptosis-photodynamic antitumor therapy.

Comparative Analysis of Tetra(2-naphthyl)tetracyano-porphyrazine and Its Iron Complex as Photosensitizers for Anticancer Photodynamic Therapy

Photodynamic therapy (PDT) is a rapidly developing modality of primary and adjuvant anticancer treatment. The main trends today are the search for new effective photodynamic agents and the creation of targeted delivery systems with the function of controlling the release of the agent in the tumor. Recently, the new group of cyanoarylporphyrazine dyes was reported, which combine the properties of photosensitizers and sensors of the local microenvironment. Such unique characteristics allow the release of the photosensitizer from the transport carrier to be assessed in real time in vivo. The aim of the present work was to compare the photophysical and photobiological properties of tetra(2-naphthyl)tetracyanoporphyrazine and its newly synthesized Fe(II) complex. We have shown that the chelation of the Fe(II) cation with the porphyrazine macrocycle leads to a decrease in molar extinction and an increase in the quantum yield of fluorescence and photostability. We demonstrate that the iron cation significantly affects the rate of dye accumulation in cells, the dark toxicity and photodynamic activity, and the direction of the changes depends on the particular cell line. However, in all the cases, the photodynamic index of a metal complex was higher than that of a metal-free base. In general, both of the compounds were found to be very promising for PDT, including for the use with transport delivery systems, and can be recommended for further in vivo studies.

Bioactive Iridium Nanoclusters with Glutathione Depletion Ability for Enhanced Sonodynamic-Triggered Ferroptosis-Like Cancer Cell Death

Ferroptosis is a regulated form of necrotic cell death that involves the accumulation of lipid peroxide (LPO) species in an iron- and reactive oxygen species (ROS)-dependent manner. Previous investigations have reported that ferroptosis-based cancer therapy can overcome the limitations of traditional therapeutics targeting the apoptosis pathway. However, it is still challenging to enhance the antitumor efficacy of ferroptosis due to intrinsic cellular regulation. In this study, a ferroptosis-inducing agent, i.e., chlorin e6 (Ce6)-conjugated human serum albumin-iridium oxide (HSA-Ce6-IrO₂ , HCIr) nanoclusters, is developed to achieve sonodynamic therapy (SDT)-triggered ferroptosis-like cancer cell death. The sonosensitizing role of both Ce6 and IrO₂ within the HCIr nanoclusters exhibits highly efficient ¹ O₂ generation capacity upon ultrasound stimulation, which promotes the accumulation of LPO and subsequently induces ferroptosis. Meanwhile, the HCIr can deplete glutathione (GSH) by accelerating Ir (IV)-Ir (III) transition, which further suppresses the activity of glutathione peroxidase 4 (GPX4) to enhance the ferroptosis efficacy. Through in vitro and in vivo experiments, it is demonstrated that HCIr possesses tremendous capacity to reduce the intracellular GSH content, which enhances SDT-triggered ferroptosis-like cancer cell death. Thus, an iridium-nanoclusters-based ferroptosis-inducing agent is developed, providing a promising strategy for inducing ferroptosis-like cancer cell death.

Oxygen-boosted biomimetic nanoplatform for synergetic phototherapy/ferroptosis activation and reversal of immune-suppressed tumor microenvironment

Photodynamic therapy (PDT) induces apoptosis of cancer cells by generating cytotoxic reactive oxygen species, the therapeutic effect of which, however, is impeded by intrinsic/inducible apoptosis-resistant mechanisms in cancer cells and hypoxia of tumor microenvironment (TME); also, PDT-induced anti-tumor immunity activation is insufficient. To deal with these obstacles, a novel biomimetic nanoplatform is fabricated for the precise delivery of photosensitizer chlorin e6 (Ce6), hemin and PEP20 (CD47 inhibitory peptide), integrating oxygen-boosted PDT, ferroptosis activation and CD47-SIRPα blockade. Hemin's catalase-mimetic activity alleviates TME hypoxia and enhances PDT. The nanoplatform activates ferroptosis via both classical (down-regulating glutathione peroxidase 4 pathway) and non-classical (inducing Fe²⁺ overload) modes. Besides the role of hemin in consuming glutathione and up-regulating heme oxygenase-1 expression, interestingly, we observe that Ce6 enhance ferroptosis activation via both classical and non-classical modes. The anti-cancer immunity is reinforced by combining PEP20-mediated CD47-SIRPα blockade and PDT-mediated T cell activation, efficiently suppressing primary tumor growth and metastasis. PEP20 has been revealed for the first time to sensitize ferroptosis by down-regulating system Xc^-. This work sheds new light on the mechanisms of PDT-ferroptosis activation interplay and bridges immunotherapy and ferroptosis activation, laying the theoretical foundation for novel combinational modes of cancer treatment.

A Triple Therapeutic Strategy with Antiexosomal Iron Efflux for Enhanced Ferroptosis Therapy and Immunotherapy

Ferroptosis is a form of regulated cell death which can not only kill tumor cells but also enhance immunogenicity of tumor cells, and it is evidenced to be involved in a variety of tumor treatments, especially in cancer immunotherapy. Tumor cell-derived exosomes are reported to influence the progression and metastasis process of tumors. In the process of ferroptosis, exosomes are also demonstrated as mediators to export iron under high intracellular iron concentration and resist ferroptosis. Under this regard, the combined application of ferroptosis inducer and the inhibitor of iron-containing exosomes may enhance the ferroptosis. Herein, biocompatible hybrid nanoparticles composed of the iron oxide nanoparticles, polymers with oxaliplatin attached, and siProminin2 are constructed. The siProminin2 mediated exosomal inhibition can restore the intracellular iron concentration, which can also inhibit the secretion of tumor cell-derived exosomes. The combination of immunotherapy with oxaliplatin, ferroptosis-based cancer therapy and inhibition of tumor cell-derived exosomes can enhance the immune activation effects. The nanoparticles represent an excellent triple therapeutic strategy for enhancing ferroptosis-based cancer therapy and immunotherapy.

pH-activated nanoplatform for visualized photodynamic and ferroptosis synergistic therapy of tumors

To overcome drug resistance and improve precision theranostics for hepatocellular carcinoma (HCC), a nanoplatform with an "off/on" function for multimodality imaging (near-infrared-II (NIR-II) fluorescence imaging, magnetic resonance imaging (MRI), and photoacoustic imaging) and synergistic therapy (photodynamic therapy and ferroptosis) activated by an acidic pH in the tumor microenvironment is proposed. Although many photosensitizers with photodynamic effects have been reported, very few of them have outstanding photodynamic effect and high stability with response to endogenous stimuli capable of NIR-II imaging. Herein, a new amphiphilic photosensitizer SR780 derived from croconaine dye, was developed with satisfactory photodynamic effects and pH-responsive NIR-II imaging. Interestingly, it was deactivated by coordination with Fe³⁺ (SR780@Fe) and activated during their release under mild acidic condition. Ferroptosis can generate hydroxyl free radical and lipid peroxide, which aggravate the oxidative stress of tumor cells and mediate their death while depleting glutathione (GSH) to enhance photodynamic effect. In situ pH-activatable theranostic nanoplatform, SR780@Fe-PAE-GP, was thus developed by loading SR780@Fe with pH-responsive polymers, modified by a glypican-3 (GPC-3) receptor-targeting peptide. The synergistic antitumor effects were confirmed both in vitro and in vivo, and the tumor inhibition rate of the SR780@Fe-PAE-GP + L treatment group reached 98%.

Ferroptosis-based nano delivery systems targeted therapy for colorectal cancer: Insights and future perspectives

There are limited options for patients who develop liver metastasis from colorectal cancer (CRC), the leading cause of cancer-related mortality worldwide. Emerging evidence has provided insights into iron deficiency and excess in CRC. Ferroptosis is an iron-dependent form of programmed cell death characterized by aberrant iron and lipid metabolism, which play crucial roles in tumorigenesis, tumor progression, and treatment options. A better understanding of the underlying molecular mechanism of ferroptosis has shed light on the current findings of ferroptosis-based nanodrug targeting strategies, such as driving ferroptosis in tumor cells and the tumor microenvironment, emerging combination therapy and against multidrug resistance. Furthermore, this review highlights the challenge and perspective of a ferroptosis-driven nanodrug delivery system for CRC-targeted therapy.