Which cell death modality wins the contest for photodynamic therapy of cancer?

Albumins constrainting the conformation of mitochondria-targeted photosensitizers for tumor-specific photodynamic therapy

Tumor ablation Preclinical organelle-targeted phototherapies have effectively achieved tumor photoablation for regenerative biomedical applications in cancer therapies. However, engineering effective phototherapy drugs with precise tumor-localization targeting and organelle direction remains challenging. Herein, we report a albumins constrainting mitochondrial-targeted photosensitizer nanoparticles (PSs@BSAs) for tumor-specific photodynamic therapy. X-ray crystallography elucidates the two-stage assembly mechanism of PSs@BSAs. Femtosecond transient absorption spectroscopy and quantum mechanical calculations reveal the implications of conformational dynamics at the excited state. PSs@BSAs can efficiently disable mitochondrial activity, and further disrupt tumor angiogenesis based on the photodynamic effect. This triggers a metabolic and oxidative stress crisis to facilitate photoablation of solid tumor and antitumor metastasis. The study fully elucidates the interdisciplinary issues of chemistry, physics, and biological interfaces, thereby opening new horizons to inspire the engineering of organelle-targeted tumor-specific photosensitizers for biomedical applications.

PANoptosis: A new era for anti-cancer strategies

Cancer cells possess an extraordinary ability to dodge cell death through various pathways, granting them a form of immortality-a key obstacle in oncotherapy. Thus, it's vital to unravel the intricate mechanisms behind newly discovered types of cell death that drive tumor suppression, going beyond apoptosis alone. The emergence of PANoptosis, a form of cell death intertwining necroptosis, pyroptosis, and apoptosis, offers a fresh perspective, integrating these pathways into one cohesive process. When cells detect damage signals, they assemble PANoptosome complexes that disrupt their balance, trigger immune responses, and lead to their eventual collapse. PANoptosis has been associated with multiple cellular pathways, including ferroptosis. Mitochondrial dysfunction also plays a critical role in sparking and advancing PANoptosis. In this review, we map out the molecular machinery and regulatory web controlling PANoptosis. We explore cutting-edge research and future trends in PANoptosis-centered tumor therapies, spotlighting promising innovations that could amplify cancer treatment effectiveness through harnessing this multifaceted cell death pathway. The development of nanomedicines and nanomaterials provides solutions to the therapeutic challenges of clinical drugs. Developing novel tumor nano-PANoptosis inducers by leveraging the advantages of nanomedicine is of research value. Traditional Chinese medicine (TCM) treatment is characterized by multiple targets, and it has distinct advantages in triggering PANoptosis through multiple pathways. Additionally, photodynamic Therapy (PDT) may offer new insights into promoting PANoptosis in tumor cells by increasing oxidative stress and reactive oxygen species levels. These will establish a solid theoretical groundwork for the development of integrated treatment methodologies.

Shift of cell-death mechanisms in primary human neutrophils with a ruthenium photosensitizer

Primary human neutrophils are the most abundant human white blood cells and are central for innate immunity. They act as early responders at inflammation sites, guided by chemotactic gradients to find infection or inflammation sites. Neutrophils can undergo both apoptosis as well as NETosis. NETosis is a form of neutrophil cell death that releases chromatin-based extracellular traps (NETs) to capture and neutralize pathogens. Understanding or controlling the balance between these cell-death mechanisms is crucial. In this study, the chemical synthesis and biologic assessment of a ruthenium complex as a light-activated photosensitizer that creates reactive oxygen species (ROS) in primary human neutrophils is reported. The ruthenium complex remains non-toxic in the dark. However, upon exposure to blue light at 450 nm, it exhibits potent cytotoxic effects in both cancerous and non-cancerous cell lines. Interestingly, the metal complex shifts the cell-death mechanism of primary human neutrophils from NETosis to apoptosis. Cells irradiated directly by the light source immediately undergo apoptosis, whereas those further away from the light source perform NETosis at a slower rate. This indicates that high ROS levels trigger apoptosis and lower ROS levels NETosis. The ability to control the type of cell death undergone in primary human neutrophils could have implications in managing acute and chronic infectious diseases.

A novel cyanine photosensitizer for sequential dual-site GSH depletion and ROS-potentiated cancer photodynamic therapy

The efficacy of photodynamic therapy (PDT) is often limited by the reductive microenvironment in tumor cells due to the high level of glutathione (GSH) and glutathione peroxidase 4 (GPX4), which maintain redox homeostasis. Therefore, designing a GSH-responsive photosensitizer that depletes intracellular GSH is a promising strategy to enhance PDT selectivity and efficacy. Herein, we present a GSH-selective sequentially responsive theranostic photosensitizer, Cy-Res. This cyanine agent targeting mitochondria effectively depletes two GSH molecules, leading to the generation of abundant ROS and exacerbating oxidative stress. Additionally, it achieves an 80-fold fluorescence enhancement upon response to GSH, enabling selective imaging of tumor cells. By mitigating GSH's impact on PDT, Cy-ResNPs achieves synergistic and efficient PDT treatment of invasive melanoma under low-power irradiation (808 nm, 80 mW/cm2). The inhibitory processes downregulate GPX4, increase apoptotic proteins like Bax, and promote mixed cell death involving both ferroptosis and apoptosis. Overall, this study offers new insights and strategies for the development of GSH-responsive theranostic agents, highlighting their potential for application in tumor diagnosis and therapy.

Immunogenicity of cell death and cancer immunotherapy with immune checkpoint inhibitors

While immunotherapy with immune checkpoint inhibitors (ICIs) has revolutionized the clinical management of various malignancies, a large fraction of patients are refractory to ICIs employed as standalone therapeutics, necessitating the development of combinatorial treatment strategies. Immunogenic cell death (ICD) inducers have attracted considerable interest as combinatorial partners for ICIs, at least in part owing to their ability to initiate a tumor-targeting adaptive immune response. However, compared with either approach alone, combinatorial regimens involving ICD inducers and ICIs have not always shown superior clinical activity. Here, we discuss accumulating evidence on the therapeutic interactions between ICD inducers and immunotherapy with ICIs in oncological settings, identify key factors that may explain discrepancies between preclinical and clinical findings, and propose strategies that address existing challenges to increase the efficacy of these combinations in patients with cancer.

Innovative integration of nanomedicines and phototherapy to modulate autophagy for enhanced tumor eradication

Nanomedicines, by significantly enhancing the solubility, stability, and targeted delivery of therapeutic agents, have emerged as transformative tools in light-induced therapies, particularly in the context of oncology. These advancements are attributed to their ability to mediate autophagy through light activation, thereby revolutionizing cancer treatment paradigms. This review provides a comprehensive analysis of the state-of-the-art integration of nanomedicines with phototherapy techniques, emphasizing their role in modulating autophagy within cancer cells. It delineates the potential of light-responsive nanomaterials to induce selective tumor cell death by precisely regulating over-activated autophagy pathways. Additionally, it discusses innovative strategies for combining nanomedicines with phototherapy and other clinical modalities for tumor treatment, as well as integrating autophagy with various forms of programmed cell death to address challenges related to drug resistance and therapeutic efficacy. By synthesizing recent advancements and delineating future research directions, this review offers a thorough perspective on the optimization of light-induced autophagy through nanomedicines, highlighting novel strategies for enhancing cancer treatment efficacy.

Erythronecroptosis: an overview of necroptosis or programmed necrosis in red blood cells

Necroptosis is considered a programmed necrosis that requires receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3), and pore-forming mixed lineage kinase domain-like protein (MLKL) to trigger a regulated cell membrane lysis. Membrane rupture in necroptosis has been shown to fuel innate immune response due to release of damage-associated molecular patterns (DAMPs). Recently published studies indicate that mature erythrocytes can undergo necroptosis as well. In this review, we provide an outline of multiple cell death modes occurring in erythrocytes, discuss possible immunological aspects of diverse erythrocyte cell deaths, summarize available evidence related to the ability of erythrocytes to undergo necroptosis, outline key involved molecular mechanisms, and discuss the potential implication of erythrocyte necroptosis in the physiology and pathophysiology. Furthermore, we aim to highlight the interplay between necroptosis and eryptosis signaling in erythrocytes, emphasizing specific characteristics of these pathways distinct from their counterparts in nucleated cells. Thus, our review provides a comprehensive summary of the current knowledge of necroptosis in erythrocytes. To reflect critical differences between necroptosis of nucleated cells and necroptosis of erythrocytes, we suggest a term erythronecroptosis for necroptosis of enucleated cells.

Immune Checkpoint-Modulating Photosensitizer That Targets BRD4 for Cancer Photoimmunotherapy

Photodynamic therapy is an efficient approach to promote cytotoxic T lymphocyte tumor infiltration to convert immunologically cold tumors into hot tumors through the induction of immunogenic cell death . However, tumors usually overexpress immune checkpoints such as PD-L1 to suppress T lymphocyte antitumor activity and evade immune surveillance. Therefore, the design of efficient photosensitizers to overcome checkpoint-mediated immune evasion is highly necessary. In this work, we report the design of BRD-PS, a BRD4-targeting photosensitizer, as a new class of immunomodulatory photosensitizer termed an immune checkpoint-modulating photosensitizer, to solve this issue. On one hand, BRD-PS induces immunogenic pyroptosis and ferroptosis to promote the activation and tumor infiltration of cytotoxic T cells. On the other hand, BRD-PS suppresses the expression of PD-L1 to avoid immune evasion. This work demonstrated the feasibility of utilizing a single photosensitizer to simultaneously induce immunogenic cell death and PD-L1 downregulation for synergistic cancer photoimmunotherapy.

Advanced 2D Nanomaterials for Phototheranostics of Breast Cancer: A Paradigm Shift

Breast cancer is the leading cause of women's deaths and associated comorbidities. The advanced and targeted strategies against breast cancer have gained considerable attention due to their potential enhanced therapeutic efficacy over conventional therapies. In this context, phototherapies like photodynamic therapy (PDT) and photothermal therapy (PTT) have shown promise as an effective and alternative strategy due to reduced side effects, noninvasiveness, and spatiotemporal specificity. With the advent of nanotechnology, several types of nanomaterials that have shown excellent prospects in increasing the efficacy of photo therapies have been exploited in cancer treatment. In recent years, 2D nanomaterials have stood out promising because of their unique ultrathin planar structure, chemical, physical, tunable characteristics, and corresponding remarkable physiochemical/biological properties. In this review, the potential and the current status of several types of 2D nanomaterials such as graphene-based nanomaterials, Mxenes, Black phosphorous, and Transition Metal Dichalcogenides for photo/thermo and combination-based imaging and therapy of breast cancer have been discussed. The current challenges and prospects in terms of translational potential in future clinical oncology are highlighted.

Treatment of Conjunctival Melanoma Cell Lines With a Light-Activated Virus-Like Drug Conjugate Induces Immunogenic Cell Death

Purpose

Conjunctival melanoma (CJM) is a rare malignant ocular surface tumor, which often leads to local recurrences and metastases. In murine models of subcutaneous tumors, treatment with a novel virus-like drug conjugate (VDC; Bel-sar) showed a dual mechanism of action with direct tumor cell killing as well as stimulation of an antitumoral immune response. Bel-sar is currently being evaluated for the treatment of primary uveal melanoma and indeterminate nevi in a phase III clinical trial. We determined whether Bel-sar also has direct antitumor efficiency and a potential immunostimulatory capacity in CJM cells.

Methods

Three human tumor-derived CJM lines were used. Bel-sar's subcellular and intracellular locations were determined with tracers. Following light activation of Bel-sar, cytotoxicity and exposure of damage-associated molecular patterns (DAMPs) were assessed. Treated tumor cells were co-cultured with THP-1 derived macrophages to assess tumor-cell phagocytosis.

Results

Bel-sar was bound and internalized by CJM cells and subsequently found in the cell membrane, lysosome, Golgi apparatus, and mitochondria. Bel-sar activation induced near complete cell death with half-maximal inhibitory concentration (IC50) values between 30 pM and 60 pM. Finally, light-activated Bel-sar enhanced exposure of DAMPs, including calreticulin, heat shock protein 90, and stimulated phagocytosis by macrophages.

Conclusions

Treatment with a novel VDC (Bel-sar) induced pro-immunogenic cell death in all three CJM cell lines. The in vitro cytotoxicity was accompanied by exposure of DAMPs, suggesting Bel-sar is a potential treatment for CJM by a dual mechanism of action. This dual mechanism may provide a targeted and direct killing of tumor cells and induce an immune response which might decrease local recurrences and metastasis.

Exploring paraptosis as a therapeutic approach in cancer treatment

A variety of cell death pathways play critical roles in the onset and progression of multiple diseases. Paraptosis, a unique form of programmed cell death, has gained significant attention in recent years. Unlike apoptosis and necrosis, paraptosis is characterized by cytoplasmic vacuolization, swelling of the endoplasmic reticulum and mitochondria, and the absence of caspase activation. Numerous natural products, synthetic compounds, and newly launched nanomedicines have been demonstrated to prime cell death through the paraptotic program and may offer novel therapeutic strategies for cancer treatment. This review summarizes recent findings, delineates the intricate network of signaling pathways underlying paraptosis, and discusses the potential therapeutic implications of targeting paraptosis in cancer treatment. The aim of this review is to expand our understanding of this unique cell death process and explore the potential therapeutic implications of targeting paraptosis in cancer treatment.

Ferroptosis Induction Enhances Photodynamic Therapy Efficacy for OLK

Oral leukoplakia (OLK) is the most representative oral potentially malignant disorder, with a high risk of malignant transformation and unclear mechanisms of occurrence. Recently, photodynamic therapy (PDT) has exhibited great potential in the treatment of OLK. However, the efficacy of PDT is difficult to predict and varies from person to person. Ferroptosis-related pathways are upregulated in many cancers, and ferroptosis induction is considered to be a potential synergistic strategy for various antitumor therapies, but its role in OLK treatment remains unclear. This study aimed to determine whether ferroptosis induction can enhance the efficacy of PDT in OLK treatment. Our study revealed that solute carrier family 7 member 11 (SLC7A11), a component of a crucial amino acid transporter and a key negative regulator of ferroptosis, was found to be highly expressed in OLK patients with no response to PDT. 5-Aminolevulinic acid (ALA)-PDT is known to cause apoptosis and necrosis, but ferroptosis also occurred under ALA-PDT in OLK cells in our study. Using erastin to induce ferroptosis enhanced the efficacy of ALA-PDT on OLK cells by disrupting the antioxidant system and further elevating intracellular reactive oxygen species levels, leading to increased apoptosis. Furthermore, this combined modality also enhanced the efficacy of ALA-PDT on 4-nitroquinoline-1-oxide (4NQO)-induced OLK lesions in mice. In summary, ferroptosis induction may serve as a potential strategy to enhance the efficacy of ALA-PDT for OLK treatment.

Necroptosis as a consequence of photodynamic therapy in tumor cells

Photodynamic therapy (PDT) is an alternative to cancer treatment, demonstrating selectivity and significant cytotoxicity on malignant tissues. Such therapy involves two nontoxic components: photosensitizer (PS) and non-ionizing radiation. In optimal dosage combinations, PDT causes cellular and tissue effects by oxygen-dependent processes, leading tumor cells to regulated cell death pathways. Regulated necrosis, called necroptosis, can be triggered by PDT and is characterized by caspase-8 inhibition and RIPK1, RIPK3, and MLKL activities, leading to plasma membrane pores formation with subsequent cellular content release into the extracellular space. For this review, studies accessed by PubMed describing the relation between necroptosis and PDT were summarized. The results showed that PDT can trigger necroptosis mechanisms in different tumor cells. Moreover, a mix of different cell death types can co-occur. It is also important to highlight that necroptosis triggered by PDT is related to damage-associated molecular patterns (DAMPs) release, involving immunogenic cell death and vaccination. The cell death response is directly related to the photosensitizer chemical characteristics, concentration, incubation time, cellular location, and irradiation parameters. The synergism among all cell death types is an excellent advantage for avowing tumor resistance mechanisms and developing new solutions.

Paraptosis-A Distinct Pathway to Cell Death

Cell death is a critical biological process necessary for development, tissue maintenance, and defense against diseases. To date, more than 20 forms of cell death have been identified, each defined by unique molecular pathways. Understanding these different forms of cell death is essential for investigating the pathogenesis of diseases such as cancer, neurodegenerative disorders, and autoimmune conditions and developing appropriate therapies. Paraptosis is a distinct form of regulated cell death characterized by cytoplasmic vacuolation and dilatation of cellular organelles like the mitochondria and endoplasmic reticulum (ER). It is regulated by several signaling pathways, for instance, those associated with ER stress, calcium overload, oxidative stress, and specific cascades such as insulin-like growth factor I receptor (IGF-IR) and its downstream signaling pathways comprising mitogen-activated protein kinases (MAPKs) and Jun N-terminal kinase (JNK). Paraptosis has been observed in diverse biological contexts, including development and cellular stress responses in neuronal, retinal, endothelial, and muscle cells. The induction of paraptosis is increasingly important in anticancer therapy, as it targets non-apoptotic stress responses in tumor cells, which can be utilized to induce cell death. This approach enhances treatment efficacy and addresses drug resistance, particularly in cases where cancer cells are resistant to apoptosis. Combining paraptosis-inducing agents with traditional therapies holds promise for enhancing treatment efficacy and overcoming drug resistance, suggesting a valuable strategy in anticancer therapy.

Immunogenic cell death-based oncolytic virus therapy: A sharp sword of tumor immunotherapy

Tumor immunotherapy, especially immune checkpoint inhibitors (ICIs), has been applied in clinical practice, but low response to immune therapies remains a thorny issue. Oncolytic viruses (OVs) are considered promising for cancer treatment because they can selectively target and destroy tumor cells followed by spreading to nearby tumor tissues for a new round of infection. Immunogenic cell death (ICD), which is the major mechanism of OVs' anticancer effects, is induced by endoplasmic reticulum stress and reactive oxygen species overload after virus infection. Subsequent release of specific damage-associated molecular patterns (DAMPs) from different types of tumor cells can transform the tumor microenvironment from "cold" to "hot". In this paper, we broadly define ICD as those types of cell death that is immunogenic, and describe their signaling pathways respectively. Focusing on ICD, we also elucidate the advantages and disadvantages of recent combination therapies and their future prospects.

Overcoming Barriers in Photodynamic Therapy Harnessing Nanogenerators Strategies

Photodynamic therapy (PDT) represents a targeted approach for cancer treatment that employs light and photosensitizers (PSs) to induce the generation of reactive oxygen species (ROS). However, PDT faces obstacles including insufficient PS localization, limited light penetration, and treatment resistance. A potential solution lies in nanogenerators (NGs), which function as self-powered systems capable of generating electrical energy. Recent progress in piezoelectric and triboelectric NGs showcases promising applications in cancer research and drug delivery. Integration of NGs with PDT holds the promise of enhancing treatment efficacy by ensuring sustained PS illumination, enabling direct electrical control of cancer cells, and facilitating improved drug administration. This comprehensive review aims to augment our comprehension of PDT principles, explore associated challenges, and underscore the transformative capacity of NGs in conjunction with PDT. By harnessing NG technology alongside PDT, significant advancement in cancer treatment can be realized. Herein, we present the principal findings and conclusions of this study, offering valuable insights into the integration of NGs to overcome barriers in PDT.

A dual-state emission luminogen for lipid droplet imaging and photodynamic therapy

Organic luminogens with dual-state emission (DSE) have garnered widespread attention due to their versatility in the forms of both dilute solutions and solids. Despite the growing interest, most research on DSE focuses primarily on molecule design and photophysical investigation, with limited exploration of their practical applications. In this study, we introduce a novel fluorescent molecule, PCT, featuring a distinct D-π(A)-D' electronic structure. PCT exhibited efficient DSE properties, with high quantum yields in both dilute solutions (ΦTHF = 52.3 %) and solid-state (Φsolid = 74.6 %). Taking advantage of PCT's lipophilicity, we demonstrated its potential for targeted lipid droplet (LD) imaging in living cells and its utility in monitoring LD depletion during cellular starvation. To further enhance its applicability in photodynamic therapy (PDT), PCT was encapsulated within the amphiphilic triblock copolymer Pluronic F127, forming PCT@F127 nanoparticles with improved colloidal stability. These nanoparticles efficiently generated singlet oxygen (1O2) under white light irradiation, achieving a 1O2 quantum yield of 57.2 %. In vitro studies on MCF-7 cells revealed significant 1O2 generation and potent phototoxicity, leading to marked cell apoptosis and necrosis. These results underscore PCT's multifunctionality as a DSEgen, with promising applications in both bioimaging and PDT.

Polyphosphoester-stabilized cubosomes encapsulating a Ru(II) complex for the photodynamic treatment of lung adenocarcinoma

The clinical translation of photosensitizers based on ruthenium(II) polypyridyl complexes (RPCs) in photodynamic therapy of cancer faces several challenges. To address these limitations, we conducted an investigation to assess the potential of a cubosome formulation stabilized in water against coalescence utilizing a polyphosphoester analog of Pluronic F127 as a stabilizer and loaded with newly synthesized RPC-based photosensitizer [Ru(dppn)2(bpy-morph)](PF6)2 (bpy-morph = 2,2'-bipyridine-4,4'-diylbis(morpholinomethanone)), PS-Ru. The photophysical characterization of PS-Ru revealed its robust capacity to induce the formation of singlet oxygen (1O2). Furthermore, the physicochemical analysis of the PS-Ru-loaded cubosomes dispersion demonstrated that the encapsulation of the photosensitizer within the nanoparticles did not disrupt the three-dimensional arrangement of the lipid bilayer. The biological tests showed that PS-Ru-loaded cubosomes exhibited significant phototoxic activity when exposed to the light source, in stark contrast to empty cubosomes and to the same formulation without irradiation. This promising outcome suggests the potential of the formulation in overcoming the drawbacks associated with the clinical use of RPCs in photodynamic therapy for anticancer treatments.

Potential of Resveratrol to Combine with Hydrogel for Photodynamic Therapy against Bacteria and Cancer-A Review

Bacterial infections and cancers are important issues in public health around the world. Currently, Western medicine is the most suitable approach when dealing with these issues. "Antibiotics" and "Corticosteroids" are the Western medicines used for bacterial infection. "Chemotherapy drugs", "surgery", and "radiotherapy" are common techniques used to treat cancer. These are conventional treatments with many side effects. PDT is a non-invasive and effective therapy for bacterial infection and cancer diseases.

METHODS

Nine electronic databases, namely WanFang Data, PubMed, Science Direct, Scopus, Web of Science, Springer Link, SciFinder, and China National Knowledge Infrastructure (CNKI), were searched to conduct this literature review, without any regard to language constraints. Studies focusing on the photodynamic actions of hydrogel and Resveratrol were included that evaluated the effect of PDT against bacteria and cancer. All eligible studies were analyzed and summarized in this review.

RESULTS

Resveratrol has antibacterial and anticancer effects. It can also act as PS in PDT or adjuvant but has some limitations. This is much better when combined with a hydrogel to enhance the effectiveness of PDT in the fight against bacteria and cancer.

CONCLUSIONS

Resveratrol combined with hydrogel is possible for PDT treatment in bacteria and cancer. They are compatible and reinforce each other to increase the effectiveness of PDT. However, much more work is required, such as cytotoxicity safety assessments of the human body and further enhancing the effectiveness of PDT in different environments for future investigations.

New substituted benzoxazine derivatives as potent inducers of membrane permeability and cell death

The search for new agents targeting different forms of cell death is an important research focus for developing new and potent antitumor therapies. As a contribution to this endeavor, we have designed and synthesized a series of new substituted 3,4-dihydro-2H-1,4-benzoxazine derivatives. These compounds have been evaluated for their efficacy against MCF-7 breast cancer and HCT-116 colon cancer cell lines. Overall, substituting this heterocycle led to improved antiproliferative activity compared to the unsubstituted derivative 1. The most active compounds, 2b and 4b, showed IC50 values of 2.27 and 3.26 μM against MCF-7 cells and 4.44 and 7.63 μM against HCT-116 cells, respectively. To investigate the mechanism of action of the target compounds, the inhibition profile of 8 kinases involved in cell signaling was studied highlighting residual activity on HER2 and JNK1 kinases. 2b and 4b showed a consistent binding mode to both receptor kinases, establishing significant interactions with known and catalytically important domains and residues. Compounds 2b and 4b exhibit potent cytotoxic activity by disrupting cell membrane permeability, likely triggering both inflammatory and non-inflammatory cell death mechanisms. This dual capability increases their versatility in the treatment of different stages or types of tumors, providing greater flexibility in clinical applications.

Heavy-atom-free π-twisted photosensitizers for fluorescence bioimaging and photodynamic therapy

As the field of preclinical research on photosensitizers (PSs) for anticancer photodynamic therapy (PDT) continues to expand, a focused effort is underway to develop agents with innovative molecular structures that offer enhanced targeting, selectivity, activation, and imaging capabilities. In this context, we introduce two new heavy-atom-free PSs, DBXI and DBAI, characterized by a twisted π-conjugation framework. This innovative approach enhances the spin-orbit coupling (SOC) between the singlet excited state (S1) and the triplet state (T1), resulting in improved and efficient intersystem crossing (ISC). Both PSs are highly effective in producing reactive oxygen species (ROS), including singlet oxygen and/or superoxide species. Additionally, they also demonstrate remarkably strong fluorescence emission. Indeed, in addition to providing exceptional photocytotoxicity, this emissive feature, generally lacking in other reported structures, allows for the precise monitoring of the PSs' distribution within specific cellular organelles even at nanomolar concentrations. These findings underscore the dual functionality of these PSs, serving as both fluorescent imaging probes and light-activated therapeutic agents, emphasizing their potential as versatile and multifunctional tools in the field of PDT.

Rapid Assessment of Bio-distribution and Antitumor Activity of the Photosensitizer Bremachlorin in a Murine PDAC Model: Detection of PDT-induced Tumor Necrosis by IRDye® 800CW Carboxylate, Using Whole-Body Fluorescent Imaging

Photodynamic therapy (PDT) is a light-based anticancer therapy that can induce tumor necrosis and/or apoptosis. Two important factors contributing to the efficacy of PDT are the concentration of the photosensitizer in the tumor tissue and its preferential accumulation in the tumor tissue compared to that in normal tissues. In this study, we investigated the use of optical imaging for monitoring whole-body bio-distribution of the fluorescent (660 nm) photosensitizer Bremachlorin in vivo, in a murine pancreatic ductal adenocarcinoma (PDAC) model. Moreover, we non-invasively, examined the induction of tumor necrosis after PDT treatment using near-infrared fluorescent imaging of the necrosis avid cyanine dye IRDye®-800CW Carboxylate. Using whole-body fluorescence imaging, we observed that Bremachlorin preferentially accumulated in pancreatic tumors. Furthermore, in a longitudinal study we showed that 3 hours after Bremachlorin administration, the fluorescent tumor signal reached its maximum. In addition, the tumor-to-background ratio at all-time points was approximately 1.4. Ex vivo, at 6 hours after Bremachlorin administration, the tumor-to-muscle or -normal pancreas ratio exhibited a greater difference than it did at 24 hours, suggesting that, in terms of efficacy, 6 hours after Bremachlorin administration was an effective time point for PDT treatment of PDAC. In vivo administration of the near infrared fluorescence agent IRDye®-800CW Carboxylate showed that PDT, 6 hours after administration of Bremachlorin, selectively induced necrosis in the tumor tissues, which was subsequently confirmed histologically. In conclusion, by using in vivo fluorescence imaging, we could non-invasively and longitudinally monitor, the whole-body distribution of Bremachlorin. Furthermore, we successfully used IRDye®-800CW Carboxylate, a near-infrared fluorescent necrosis avid agent, to image PDT-induced necrotic cell death as a measure of therapeutic efficacy. This study showed how fluorescence can be applied for optimizing, and assessing the efficacy of, PDT.

β-Galactosidase-Triggered Photodynamic Elimination of Senescent Cells with a Boron Dipyrromethene-Based Photosensitizer

Senescence is a cellular response having physiological and reparative functions to preserve tissue homeostasis and suppress tumor growth. However, the accumulation of senescent cells would cause deleterious effects that lead to age-related dysfunctions and cancer progression. Hence, selective detection and elimination of senescent cells are crucial yet remain a challenge. A β-galactosidase (β-gal)-activated boron dipyrromethene (BODIPY)-based photosensitizer (compound 1) is reported here that can selectively detect and eradicate senescent cells. It contains a galactose moiety connected to a pyridinium BODIPY via a self-immolative nitrophenylene linker, of which the photoactivity is effectively quenched. Upon interactions with the senescence-associated β-gal, it undergoes enzymatic hydrolysis followed by self-immolation, leading to the release of an activated BODIPY moiety by which the fluorescence emission and singlet oxygen generation are restored. The ability of 1 to detect and eliminate senescent cells is demonstrated in vitro and in vivo, using SK-Mel-103 tumor-bearing mice treated with senescence-inducing therapy. The results demonstrate that 1 can be selectively activated in senescent cells to trigger a robust senolytic effect upon irradiation. This study breaks new ground in the design and application of new senolytic agents based on photodynamic therapy.

A Cyclometalated Ruthenium(II) Complex Induces Oncosis for Synergistic Activation of Innate and Adaptive Immunity

An optimal cancer chemotherapy regimen should effectively address the drug resistance of tumors while eliciting antitumor-immune responses. Research has shown that non-apoptotic cell death, such as pyroptosis and ferroptosis, can enhance the immune response. Despite this, there has been limited investigation and reporting on the mechanisms of oncosis and its correlation with immune response. Herein, we designed and synthesized a Ru(II) complex that targeted the nucleus and mitochondria to induce cell oncosis. Briefly, the Ru(II) complex disrupts the nucleus and mitochondria DNA, which active polyADP-ribose polymerase 1, accompanied by ATP consumption and porimin activation. Concurrently, mitochondrial damage and endoplasmic reticulum stress result in the release of Ca2+ ions and increased expression of Calpain 1. Subsequently, specific pore proteins porimin and Calpain 1 promote cristae destruction or vacuolation, ultimately leading to cell membrane rupture. The analysis of RNA sequencing demonstrates that the Ru(II) complex can initiate the oncosis-associated pathway and activate both innate and adaptive immunity. In vivo experiments have confirmed that oncosis promotes dendritic cell maturation and awakens adaptive cytotoxic T lymphocytes but also activates the innate immune by inducing the polarization of macrophages towards an M1 phenotype.

Photodynamic Therapy in the Treatment of Cancer-The Selection of Synthetic Photosensitizers

Photodynamic therapy (PDT) is a promising cancer treatment method that uses photosensitizing (PS) compounds to selectively destroy tumor cells using laser light. This review discusses the main advantages of PDT, such as its low invasiveness, minimal systemic toxicity and low risk of complications. Special attention is paid to photosensitizers obtained by chemical synthesis. Three generations of photosensitizers are presented, starting with the first, based on porphyrins, through the second generation, including modified porphyrins, chlorins, 5-aminolevulinic acid (ALA) and its derivative hexyl aminolevulinate (HAL), to the third generation, which is based on the use of nanotechnology to increase the selectivity of therapy. In addition, current research trends are highlighted, including the search for new photosensitizers that can overcome the limitations of existing therapies, such as heavy-atom-free nonporphyrinoid photosensitizers, antibody-drug conjugates (ADCs) or photosensitizers with a near-infrared (NIR) absorption peak. Finally, the prospects for the development of PDTs are presented, taking into account advances in nanotechnology and biomedical engineering. The references include both older and newer works. In many cases, when writing about a given group of first- or second-generation photosensitizers, older publications are used because the properties of the compounds described therein have not changed over the years. Moreover, older articles provide information that serves as an introduction to a given group of drugs.

The effect of light irradiation on a nitro-ruthenium porphyrin complex in the induced death of lung cancer cells in two- and three-dimensional cultures: Insights into the effect of nitric oxide

Efforts to find compounds selectively affecting cancer cells while sparing normal ones have continued to grow. Nitric oxide (NO) is critical in physiology and pathology, including cancer. It influences cellular processes like proliferation, apoptosis, and angiogenesis. The intricate interaction of NO with cancer cells offers innovative treatment possibilities, but its effects can vary by concentration and site. Ruthenium complexes capable of releasing NO upon stimulation show for this purpose. These versatile compounds can also enhance photodynamic therapy (PDT), a light-activated approach, which induces cellular damage. Ruthenium-based photosensitizers (PSs), delivering NO and producing reactive oxygen species (ROS), offer a novel strategy for improved cancer treatments. In this study, a nitro-ruthenium porphyrin conjugate: {TPyP[Ru(NO2)(bpy)2]4}(PF6)4, designated RuNO2TPyP, which releases NO upon irradiation, was investigated for its effects on lung cells (non-tumor MRC-5 and tumor A549) in 2D and 3D cell cultures. The findings suggest that this complex has potential for PDT treatment in lung cancer, as it exhibits photocytotoxicity at low concentrations without causing cytotoxicity to normal lung cells. Moreover, treatment of cells with RuNO2TPyP followed by light irradiation (4 J cm-2) can induce apoptosis, generate ROS, promote intracellular NO formation, and has anti-migratory effects. Additionally, the complex can modify tumor cell structures and induce photocytotoxicity and apoptosis in a 3D culture. These outcomes are attributed to the internalization of the complex and its subsequent activation upon light irradiation, resulting in NO release and singlet oxygen production.

Photodynamic Therapy Derived Personalized Whole Cell Tumor Vaccine Prevents Postsurgery Tumor Recurrence and Metastasis

In order to avoid the time-consuming and laborious identification of tumor-specific antigens (TSAs) during the traditional vaccine fabrication process, a versatile photodynamic therapy (PDT)-based method is developed to construct a whole-tumor antigen tumor vaccine (TV) from surgically resected tumor tissues for personalized immunotherapy. Mucoadhesive nanoparticles containing small-molecular photosensitizer are fabricated and directly co-incubated with suspended tumor cells obtained after cytoreduction surgery. After irradiation with a 405 nm laser, potent immunogenic cell death of cancer cells could be induced. Along with the release of TSAs, the as-prepared TV could activate safe and robust tumor-specific immune responses, leading to efficient suppression of postsurgery tumor recurrence and metastasis. The as-prepared TV cannot only be applied alone through various administration routes but also synergize with immunoadjuvant, chemotherapeutics, and immune checkpoint blockers to exert more potent immune responses. This work provides an alternative way to promote the clinical translation of PDT, which is generally restricted by the limited penetration of light. Moreover, the versatile strategy of vaccine fabrication also facilitates the clinical application of personalized whole-cell tumor vaccines.

Isolation, Identification, and Biological Activities of a New Chlorin e6 Derivative

Chlorin e6 is a well-known photosensitizer used in photodynamic diagnosis and therapy. A method for identifying and purifying a novel process-related impurity during the synthesis of chlorin e6 has been developed. Its structure was elucidated using NMR and HRMS. This new impurity is formed from chlorophyll b rather than chlorophyll a, which is the source of chlorin e6. The intermediates formed during chlorin e6 synthesis were monitored using HPLC-mass spectrometry. This new impurity was identified as rhodin g7 71-ethyl ester, the structure of which remains unknown to date. The cytotoxic effects of this novel compound in both dark and light conditions were studied against five cancer cell lines (HT29, MIA-PaCa-2, PANC-1, AsPC-1, and B16F10) and a normal cell line (RAW264.7) and compared to those of chlorin e6. Upon irradiation using a laser at 0.5 J/cm2, rhodin g7 71-ethyl ester demonstrated higher cytotoxicity (2-fold) compared to chlorin e6 in the majority of the cancer cell lines. Furthermore, this new compound exhibited higher dark cytotoxicity compared to chlorin e6. Studies on singlet oxygen generation, the accumulation in highly vascular liver tissue, and the production of reactive oxygen species in MIA-PaCa-2 cancer cells via rhodin g7 71-ethyl ester correspond to its higher cytotoxicity as a newly developed photosensitizer. Therefore, rhodin g7 71-ethyl ester could be employed as an alternative or complementary agent to chlorin e6 in the photodynamic therapy for treating cancer cells.

Graphene-Based Photodynamic Therapy and Overcoming Cancer Resistance Mechanisms: A Comprehensive Review

Photodynamic therapy (PDT) is a non-invasive therapy that has made significant progress in treating different diseases, including cancer, by utilizing new nanotechnology products such as graphene and its derivatives. Graphene-based materials have large surface area and photothermal effects thereby making them suitable candidates for PDT or photo-active drug carriers. The remarkable photophysical properties of graphene derivates facilitate the efficient generation of reactive oxygen species (ROS) upon light irradiation, which destroys cancer cells. Surface functionalization of graphene and its materials can also enhance their biocompatibility and anticancer activity. The paper delves into the distinct roles played by graphene-based materials in PDT such as photosensitizers (PS) and drug carriers while at the same time considers how these materials could be used to circumvent cancer resistance. This will provide readers with an extensive discussion of various pathways contributing to PDT inefficiency. Consequently, this comprehensive review underscores the vital roles that graphene and its derivatives may play in emerging PDT strategies for cancer treatment and other medical purposes. With a better comprehension of the current state of research and the existing challenges, the integration of graphene-based materials in PDT holds great promise for developing targeted, effective, and personalized cancer treatments.

Miniature wireless LED-device for photodynamic-induced cell pyroptosis

The inability of visible light to penetrate far through biological tissue limits its use for phototherapy and photodiagnosis of deep-tissue sites of disease. This is unfortunate because many visible dyes are excellent photosensitizers and photocatalysts that can induce a wide range of photochemical processes, including photogeneration of reactive oxygen species. One potential solution is to bring the light source closer to the site of disease by using a miniature implantable LED. With this goal in mind, we fabricated a wireless LED-based device (volume of 23 mm3) that is powered by RF energy and emits light with a wavelength of 573 nm. It has the capacity to excite the green absorbing dye Rose Bengal, which is an efficient type II photosensitizer. The wireless transfer of RF power is effective even when the device is buried in chicken breast and located 6 cm from the transmitting antenna. The combination of a wireless device as light source and Rose Bengal as photosensitizer was found to induce cell death of cultured HT-29 human colorectal adenocarcinoma cells. Time-dependent generation of protruding bubbles was observed in the photoactivated cells suggesting cell death by light-induced pyroptosis and supporting evidence was gained by cell staining with the fluorescence probes Annexin-V FITC and Propidium Iodide. The results reveal a future path towards a wireless implanted LED-based device that can trigger photodynamic immunogenic cell death in deep-seated cancerous tissue.

Two-Photon Photodegradation of E3 Ubiquitin Ligase Cereblon by a Ru(II) Complex: Inducing Ferroptosis in Cisplatin-Resistant Tumor Cells

Using photodynamic therapy (PDT) to trigger nonconventional cell death pathways has provided a new scheme for highly efficient and non-side effects to drug-resistant cancer therapies. Nonetheless, the unclear targets of available photosensitizers leave the manner of PDT-induced tumor cell death relatively unpredictable. Herein, we developed a novel Ru(II)-based photosensitizer, Ru-Poma. Possessing the E3 ubiquitin ligase CRBN-targeting moiety and high singlet oxygen yield of 0.96, Ru-Poma was demonstrated to specifically photodegrade endogenous CRBN, increase lipid peroxide, downregulate GPX4 and GAPDH expression, and consequently induce ferroptosis in cisplatin-resistant cancerous cells. Furthermore, with the deep penetration of two-photon excitation, Ru-Poma achieved drug-resistant circumvention in a 3D tumor cell model. Thus, we describe the first sample of the CRBN-targeting Ru(II) complex active in PDT.

Iron metabolism: backfire of cancer cell stemness and therapeutic modalities

Cancer stem cells (CSCs), with their ability of self-renewal, unlimited proliferation, and multi-directional differentiation, contribute to tumorigenesis, metastasis, recurrence, and resistance to conventional therapy and immunotherapy. Eliminating CSCs has long been thought to prevent tumorigenesis. Although known to negatively impact tumor prognosis, research revealed the unexpected role of iron metabolism as a key regulator of CSCs. This review explores recent advances in iron metabolism in CSCs, conventional cancer therapies targeting iron biochemistry, therapeutic resistance in these cells, and potential treatment options that could overcome them. These findings provide important insights into therapeutic modalities against intractable cancers.

Near-infrared-driven upconversion nanoparticles with photocatalysts through water-splitting towards cancer treatment

Water splitting is promising, especially for energy and environmental applications; however, there are limited studies on the link between water splitting and cancer treatment. Upconversion nanoparticles (UCNPs) can be used to convert near-infrared (NIR) light to ultraviolet (UV) or visible (Vis) light and have great potential for biomedical applications because of their profound penetration ability, theranostic approaches, low self-fluorescence background, reduced damage to biological tissue, and low toxicity. UCNPs with photocatalytic materials can enhance the photocatalytic activities that generate a shorter wavelength to increase the tissue penetration depth in the biological microenvironment under NIR light irradiation. Moreover, UCNPs with a photosensitizer can absorb NIR light and convert it into UV/vis light and emit upconverted photons, which excite the photoinitiator to create H2, O2, and/or OH˙ via water splitting processes when exposed to NIR irradiation. Therefore, combining UCNPs with intensified photocatalytic and photoinitiator materials may be a promising therapeutic approach for cancer treatment. This review provides a novel strategy for explaining the principles and mechanisms of UCNPs and NIR-driven UCNPs with photocatalytic materials through water splitting to achieve therapeutic outcomes for clinical applications. Moreover, the challenges and future perspectives of UCNP-based photocatalytic materials for water splitting for cancer treatment are discussed in this review.

Photodynamic Therapy with Targeted Release of Boron-Dipyrromethene Dye from Cobalt(III) Prodrugs in Red Light

Boron-dipyrromethene (BODIPY) dyes are promising photosensitizers for cellular imaging and photodynamic therapy (PDT) owing to their excellent photophysical properties and the synthetically tunable core. Metalation provides a convenient way to overcome the drawbacks arising from their low aqueous solubility. New photo-/redox-responsive Co(III) prodrug chaperones are developed as anticancer PDT agents for efficient cellular delivery of red-light-active BODIPY dyes. The photobiological activity of heteroleptic Co(III) complexes derived from tris(2-pyridylmethyl)amine (TPA) and acetylacetone-conjugated PEGylated distyryl BODIPY (HL1) or its dibromo analogue (HL2), [CoIII(TPA)(L1/L2)](ClO4)2 (1 and 2), are investigated. The Co(III)/Co(II) redox potential is tuned using the Co(III)-TPA scaffold. Complex 1 displays the in vitro release of BODIPY on red light irradiation. Complex 2, having good singlet oxygen quantum yield (ΦΔ ∼ 0.28 in DMSO), demonstrates submicromolar photocytotoxicity to HeLa cancer cells (IC50 ≈ 0.23 μM) while being less toxic to HPL1D normal cells in red light. Cellular imaging using the emissive complex 1 shows mitochondrial localization and significant penetration into the HeLa tumor spheroids. Complex 2 shows supercoiled DNA photocleavage activity and apoptotic cell death through phototriggered generation of reactive oxygen species. The Co(III)-BODIPY prodrug conjugates exemplify new type of phototherapeutic agents with better efficacy than the organic dyes alone in the phototherapeutic window.

A first-in-class β-glucuronidase responsive conjugate for selective dual targeted and photodynamic therapy of bladder cancer

In this report, we present a novel prodrug strategy that can significantly improve the efficiency and selectivity of combined therapy for bladder cancer. Our approach involved the synthesis of a conjugate based on a chlorin-e6 photosensitizer and a derivative of the tyrosine kinase inhibitor cabozantinib, linked by a β-glucuronidase-responsive linker. Upon activation by β-glucuronidase, which is overproduced in various tumors and localized in lysosomes, this conjugate released both therapeutic modules within targeted cells. This activation was accompanied by the recovery of its fluorescence and the generation of reactive oxygen species. Investigation of photodynamic and dark toxicity in vitro revealed that the novel conjugate had an excellent safety profile and was able to inhibit tumor cells proliferation at submicromolar concentrations. Additionally, combined therapy effects were also observed in 3D models of tumor growth, demonstrating synergistic suppression through the activation of both photodynamic and targeted therapy.

Advances in photodynamic therapy of pathologic scar

Pathologic scars include keloids and hypertrophic scars due to abnormal wound healing. Both cause symptoms of itching and pain; they also affect one's appearance and may even constrain movement. Such scars place a heavy burden on the individual's physical and mental health; moreover, treatment with surgery alone is highly likely to leave more scarring. Therefore, there is an urgent need for a treatment that is both minimally invasive and convenient. Photodynamic therapy (PDT) is an emerging safe and noninvasive technology wherein photosensitizers and specific light sources are used to treat malignant tumors and skin diseases. Research on PDT from both the laboratory and clinic has been reported. These findings on the treatment of pathologic scars using photosensitizers, light sources, and other mechanisms are reviewed in the present article.

A NRF2 Regulated and the Immunosuppressive Microenvironment Reversed Nanoplatform for Cholangiocarcinoma Photodynamic-Gas Therapy

Photodynamic therapy (PDT) is a minimally invasive and controllable local cancer treatment for cholangiocarcinoma (CCA). However, the efficacy of PDT is hindered by intratumoral hypoxia and the presence of an antioxidant microenvironment. To address these limitations, combining PDT with gas therapy may be a promising strategy to enhance tumor oxygenation. Moreover, the augmentation of oxidative damage induced by PDT and gas therapy can be achieved by inhibiting NRF2, a core regulatory molecule involved in the antioxidant response. In this study, an integrated nanotherapeutic platform called CMArg@Lip, incorporating PDT and gas therapies using ROS-responsive liposomes encapsulating the photosensitizer Ce6, the NO gas-generating agent L-arginine, and the NRF2 inhibitor ML385, is successfully developed. The utilization of CMArg@Lip effectively deals with challenges posed by tumor hypoxia and antioxidant microenvironment, resulting in elevated levels of oxidative damage and subsequent induction of ferroptosis in CCA. Additionally, these findings suggest that CMArg@Lip exhibits notable immunomodulatory effects, including the promotion of immunogenic cell death and facilitation of dendritic cell maturation. Furthermore, it contributes to the anti-tumor function of cytotoxic T lymphocytes through the downregulation of PD-L1 expression in tumor cells and the activation of the STING signaling pathway in myeloid-derived suppressor cells, thereby reprogramming the immunosuppressive microenvironment via various mechanisms.

Enhancing Precision in Photodynamic Therapy: Innovations in Light-Driven and Bioorthogonal Activation

Over the past few decades, photodynamic therapy (PDT) has evolved as a minimally invasive treatment modality offering precise control over cancer and various other diseases. To address inherent challenges associated with PDT, researchers have been exploring two promising avenues: the development of intelligent photosensitizers activated through light-induced energy transfers, charges, or electron transfers, and the disruption of photosensitive bonds. Moreover, there is a growing emphasis on the bioorthogonal delivery or activation of photosensitizers within tumors, enabling targeted deployment and activation of these intelligent photosensitive systems in specific tissues, thus achieving highly precise PDT. This concise review highlights advancements made over the last decade in the realm of light-activated or bioorthogonal photosensitizers, comparing their efficacy and shaping future directions in the advancement of photodynamic therapy.

PEGylated Molybdenum-Iodine Nanocluster as a Promising Radiodynamic Agent against Prostatic Adenocarcinoma

The combination of photodynamic therapy and radiotherapy has given rise to a modality called radiodynamic therapy (RDT), based on reactive oxygen species-producing radiosensitizers. The production of singlet oxygen, O2(1Δg), by octahedral molybdenum (Mo6) clusters upon X-ray irradiation allows for simplification of the architecture of radiosensitizing systems. In this context, we prepared a radiosensitizing system using copper-free click chemistry between a Mo6 cluster bearing azido ligands and the homo-bifunctional linker bis-dPEG11-DBCO. The resulting compound formed nanoparticles, which featured production of O2(1Δg) and efficient cellular uptake, leading to remarkable photo- and radiotoxic effects against the prostatic adenocarcinoma TRAMP-C2 cell line. Spheroids of TRAMP-C2 cells were also used for evaluation of toxicity and phototoxicity. In vivo experiments on a mouse model demonstrated that subcutaneous injection of the nanoparticles is a safe administration mode at a dose of up to 0.08 g kg-1. The reported results confirm the relevancy of Mo6-based radiosensitizing nanosystems for RDT.

Genetically light-enhanced immunotherapy mediated by a fluorinated reduction-sensitive delivery system

The lack of safe and efficient therapeutic agent delivery platforms restricts combined therapy's effect, and combined cancer therapy's multi-component delivery effect needs improvement. The novel gene delivery system SS-HPT-F/pMIP-3β-KR was proposed to construct fluorine-containing degradable cationic polymers SS-HPT-F by a mild and simple amino-epoxy ring-opening reaction. By modifying the fluorinated alkyl chain, the delivery efficiency of the plasmid was greatly improved, and the cytoplasmic transport of biomolecules was completed. At the same time, a combination plasmid (MIP-3β-KillerRed) was innovatively designed for the independent expression of immune and photodynamic proteins. Which was efficiently transported to the tumor site by SS-HPT-F. The MIP-3β is expressed as an immune chemokine realize the immune mobilization behavior. The photosensitive protein KillerRed expressed in the tumor killed cancer cells under irradiation and released the exocrine immune factor MIP-3β. The immunogenic cell death (ICD) produced by photodynamic therapy (PDT) also induced the immune response of the organism. The synergistic effect of PDT and MIP-3β mobilized the immune properties of the organism, providing light-enhanced immune combination therapy against malignant tumors. Therefore, in subcutaneous tumor-bearing and metastatic animal models, the carrier tumor growth and mobilize organism produce an immune response without systemic toxicity. This work reports the first efficient gene delivery system that achieves light-enhanced immunotherapy.

A Bioorthogonal Antidote Against the Photosensitivity after Photodynamic Therapy

As an effective and non-invasive treatment modality for cancer, photodynamic therapy (PDT) has attracted considerable interest. With the recent advances in the photosensitizing agents, the fiber-optic systems, and other aspects, its application is extended to a wide range of superficial and localized cancers. However, for the few clinically used photosensitizers, most of them suffer from the drawback of causing prolonged photosensitivity after the treatment. As a result, post-PDT management is also a crucial issue. Herein, a facile bioorthogonal approach is reported that can effectively suppress this common side effect of PDT in nude mice. It involves the use of an antidote that contains a black-hole quencher BHQ-3 conjugated with a bicyclo[6.1.0]non-4-yne (BCN) moiety and a tetrazine-substituted boron dipyrromethene-based photosensitizer. By using tumor-bearing nude mice as an animal model, it is demonstrated that after PDT with this photosensitizer, the administration of the antidote can effectively quench the photodynamic activity of the residual photosensitizer by bringing the BHQ-3 quencher close to the photosensitizing unit through a rapid click reaction. It results in substantial reduction in skin damage upon light irradiation. The overall results demonstrate that this simple and facile strategy can provide an effective means for minimizing the photosensitivity after PDT.

Mitochondria-targeted photodynamic therapy triggers GSDME-mediated pyroptosis and sensitizes anti-PD-1 therapy in colorectal cancer

BACKGROUND

The effectiveness of immune checkpoint inhibitors in colorectal cancer (CRC) is limited due to the low tumor neoantigen load and low immune infiltration in most microsatellite-stable (MSS) tumors. This study aimed to develop a mitochondria-targeted photodynamic therapy (PDT) approach to provoke host antitumor immunity of MSS-CRC and elucidate the underlying molecular mechanisms.

METHODS

The role and mechanism of mitochondria-targeted PDT in inhibiting CRC progression and inducing pyroptosis were evaluated both in vitro and in vivo. The immune effects of PDT sensitization on PD-1 blockade were also assessed in CT26 and 4T1 tumor-bearing mouse models.

RESULTS

Here, we report that PDT using IR700DX-6T, a photosensitizer targeting the mitochondrial translocation protein, may trigger an antitumor immune response initiated by pyroptosis in CRC. Mechanistically, IR700DX-6T-PDT produced reactive oxygen species on light irradiation and promoted downstream p38 phosphorylation and active caspase3 (CASP3)-mediated cleavage of gasdermin E (GSDME), subsequently inducing pyroptosis. Furthermore, IR700DX-6T-PDT enhanced the sensitivity of MSS-CRC cells to PD-1 blockade. Decitabine, a demethylation drug used to treat hematologic neoplasms, disrupted the abnormal methylation pattern of GSDME in tumor cells, enhanced the efficacy of IR700DX-6T-PDT, and elicited a potent antitumor immune response in combination with PD-1 blockade and IR700DX-6T-PDT.

CONCLUSION

Our work provides clear a understanding of immunogenic cell death triggered by mitochondria-targeted PDT, offering a new approach for enhancing the efficacy of PD-1 blockade in CRC.

Photosensitizing effects and physicochemical properties of chlorophyll a derivatives with hydrophilic oligoethylene glycol fragments at the macrocycle periphery

In this work, screening studies of the cytotoxic effect of chlorins with fragments of di-, tri-, and pentaethylene glycol at the macrocycle periphery in relation to HeLa, A549, and HT29 cells were performed. It is shown that, despite different hydrophobicity, all the compounds studied have a comparable photodynamic effect. The conjugate of chlorin e6 with pentaethylene glycol, which has the lowest tendency to association among the studied compounds with tropism for low density lipoproteins and the best characteristics of the formation of molecular complexes with Tween 80, has a significant difference in dark and photoinduced toxicity (ratio IC50(dark)/IC50(photo) approximately 2 orders of magnitude for all cell lines), which allows to hope for a sufficiently large "therapeutic window". A study of the interaction of this compound with HeLa cells shows that the substance penetrates the cell and, after red light irradiation induces ROS appearance inside the cell, associated, apparently, with the photogeneration of singlet oxygen. These data indicate that photoinduced toxic effects are caused by damage to intracellular structures as a result of oxidative stress. Programmed type of cell death characterized with caspase-3 induction is prevailing. So, the conjugate of chlorin e6 with pentaethylene glycol is a promising antitumor PS that can be successfully solubilized with Tween 80, which makes it suitable for further in vivo studies.

An immunogenic cell death-related gene expression signature in predicting prognosis of pancreatic ductal adenocarcinoma

BACKGROUND

Immunogenic cell death (ICD) has been identified as regulated cell death, which is sufficient to activate the adaptive immune response. This study aimed to research ICD-related genes and create a gene model to predict pancreatic ductal adenocarcinoma (PAAD) patients' prognosis.

METHODS

The RNA sequencing and clinical data were downloaded from the TGCA and GEO databases. The PAAD samples were classified into two subtypes based on the expression levels of ICD-related genes using consensus clustering. Based on the differentially expressed genes (DEGs), a prognostic scoring model was constructed using LASSO regression and Cox regression, and the scoring model was used to predict the prognosis of PAAD patients. Moreover, colony formation assay was performed to confirm the prognostic value of those genes.

RESULTS

We identified two ICD cluster by consensus clustering, and found that the the ICD-high group was closely associated with immune-hot phenotype, favorable clinical outcomes. We established an ICD-related prognostic model which can predict the prognosis of pancreatic ductal adenocarcinoma. Moreover, depletion of NT5E, ATG5, FOXP3, and IFNG inhibited the colony formation ability of pancreatic cancer cell.

CONCLUSION

We identified a novel classification for PAAD based on the expression of ICD-related genes, which may provide a potential strategy for therapeutics against PAAD.

Novel indocyanine green-loaded photothermal nanoparticles targeting TRPV1 for thermal ablation treatment of severe murine asthma induced by ovalbumin and lipopolysaccharide

To identify a replacement strategy for bronchial thermoplasty (BT) with non-invasive and free-of-severe side effect is urgently needed in the clinic for severe asthma treatment. In this study, PLGA-PEG@ICG@TRPV1 pAb (PIT) photothermal nanoparticles targeting bronchial TRPV1 were designed for photothermal therapy (PTT) against severe murine asthma induced by ovalbumin and lipopolysaccharide. PIT was formulated with a polyethylene glycol (PEG)-grafted poly (lactic-co-glycolic) acid (PLGA) coating as a skeleton structure to encapsulate indocyanine green (ICG) and was conjugated to the polyclonal antibody against transient receptor potential vanilloid 1 (TRPV1 pAb). The results revealed that PIT held good druggability due to its electronegativity and small diameter. PIT demonstrated great photothermal effects both in vivo and in vitro and exhibited good ability to target TRPV1 in vitro because of its selective cell uptake and specific cell toxicity toward TRPV1-overexpressing cells. The PIT treatment effectively reduced asthma symptoms in mice. This is evident from improvements in expiratory airflow limitation, significant decreases in inflammatory cell infiltration in the airways, and increases in goblet cell and columnar epithelial cell proliferation. In conclusion, PIT alleviates severe murine asthma symptoms through a combination of TRPV1 targeting and photothermal effects.

Self-assembled porphyrin-peptide cages for photodynamic therapy

The development of photodynamic therapy requires access to smart photosensitizers which combine appropriate photophysical and biological properties. Interestingly, supramolecular and dynamic covalent chemistries have recently shown their ability to produce novel architectures and responsive systems through simple self-assembly approaches. Herein, we report the straightforward formation of porphyrin-peptide conjugates and cage compounds which feature on their surface chemical groups promoting cell uptake and specific organelle targeting. We show that they self-assemble, in aqueous media, into positively-charged nanoparticles which generate singlet oxygen upon green light irradiation, while also undergoing a chemically-controlled disassembly due to the presence of reversible covalent linkages. Finally, the biological evaluation in cells revealed that they act as effective photosensitizers and promote synergistic effects in combination with Doxorubicin.

Theranostic Uses of the Heme Pathway in Neuro-Oncology: Protoporphyrin IX (PpIX) and Its Journey from Photodynamic Therapy (PDT) through Photodynamic Diagnosis (PDD) to Sonodynamic Therapy (SDT)

ALA PDT, first approved as a topical therapy to treat precancerous skin lesions in 1999, targets the heme pathway selectively in cancers. When provided with excess ALA, the fluorescent photosensitizer PpIX accumulates primarily in cancer tissue, and ALA PDD is used to identify bladder and brain cancers as a visual aid for surgical resection. ALA PDT has shown promising anecdotal clinical results in recurrent glioblastoma multiforme. ALA SDT represents a noninvasive way to activate ALA PDT and has the potential to achieve clinical success in the treatment of both intracranial and extracranial cancers. This review describes the creation and evolution of ALA PDT, from the treatment of skin cancers to PDD and PDT of malignant brain tumors and, most recently, into a noninvasive form of PDT, ALA SDT. Current clinical trials of ALA SDT for recurrent glioblastoma and high-grade gliomas in adults, and the first pediatric ALA SDT clinical trial for a lethal brainstem cancer, diffuse intrinsic pontine glioma (DIPG), are also described.

Modifications of DAMPs levels in extracellular environment induced by aminolevulinic acid-based photodynamic therapy of esophageal cancer cells

PURPOSE

Immunogenic cell death plays an important role in anticancer treatment because it combines cell death with appearance of damage associated molecular patterns that have the potential to activate anticancer immunity. Effects of damage associated molecular patterns induced by aminolevulinic acid-based photodynamic therapy were studied mainly on dendritic cells. They have not been deeply studied on macrophages that constitute the essential component of the tumor microenvironment. The aim of this study was to analyze features of esophageal cancer cell death in relation to release capacity of damage associated molecular pattern species, and to test the effect of related extracellular environmental alterations on macrophages.

MATERIAL AND METHODS

Esophageal Kyse 450 carcinoma cells were subjected to aminolevulinic acid-based photodynamic therapy at different concentrations of aminolevulinic acid. Resting, IFN/LPS and IL-4 macrophage subtypes were prepared from monocytic THP-1 cell line. Cell death features and macrophage modifications were analyzed by fluorescence-based live cell imaging. ATP and HMGB1 levels in cell culture media were determined by ELISA assays. The presence of lipid peroxidation products in culture media was assessed by spectrophotometric detection of thiobarbituric acid reactive substances.

RESULTS

Aminolevulinic acid-based photodynamic therapy induced various death pathways in Kyse 450 cells that included features of apoptosis, necrosis and ferroptosis. ATP amounts in extracellular environment of treated Kyse 450 cells increased with increasing aminolevulinic acid concentration. Levels of HMGB1, detectable by ELISA assay in culture media, were decreased after the treatment. Aminolevulinic acid-based photodynamic therapy induced lipid peroxidation of cellular structures and increased levels of extracellular lipid peroxidation products. Incubation of resting and IL-4 macrophages in conditioned medium from Kyse 450 cells treated by aminolevulinic acid-based photodynamic therapy induced morphological changes in macrophages, however, comparable alterations were induced also by conditioned medium from untreated cancer cells.

CONCLUSION

Aminolevulinic acid-based photodynamic therapy leads to alterations in local extracellular levels of damage associated molecular patterns, however, comprehensive studies are needed to find whether they can be responsible for macrophage phenotype modifications.

Targeting PERK-ATF4-P21 axis enhances the sensitivity of osteosarcoma HOS cells to Mppα-PDT

Osteosarcoma (OS) is the most prevalent type of malignant bone tumor in adolescents. The overall survival of OS patients has reached a plateau recently. Thus, there is an urgent need to develop approaches to improve the sensitivity of OS to therapies. Pyropheophorbide-α methyl ester-mediated photodynamic therapy (MPPα-PDT) is a new type of tumor therapy, and elucidating its mechanism is helpful to improve its anti-tumor efficacy. Here, we investigated how PERK signaling promotes the human OS (HOS) cell survival induced by MPPα-PDT, as overcoming this may enhance sensitivity to MPPα-PDT. We found that MPPα-PDT combined with PERK inhibitor GSK2656157 enhanced HOS cell apoptosis by suppressing autophagy and p21. Autophagy inhibition and p21 depletion enhanced cell death, indicating pro-survival effects in MPPα-PDT. Notably, p21 was found to be an effector of the PERK-Atf4 pathway, which could positively regulate autophagy mediated by MPPα-PDT. In conclusion, we found that the combination of MPPα-PDT and GSK2656157 enhanced apoptosis in HOS cells by inhibiting autophagy. Mechanistically, this autophagy is p21-dependent and can be suppressed by GSK2656157, thereby enhancing sensitivity to MPPα-PDT.

Painless photodynamic therapy for facial actinic keratoses: A retrospective cohort study of the post-treatment inflammatory response

INTRODUCTION

Photodynamic therapy (PDT) is a safe, non-mutagenic, and non-scarring treatment for actinic keratoses (AK).

BACKGROUND

'Painless' photodynamic therapy (p-PDT) is a regimen for AK that employs simultaneous aminolevulinate incubation and blue light illumination. The efficacy of p-PDT resembles that of traditional PDT, but detailed mechanisms of action for p-PDT are not well understood.

METHODS

To characterize the inflammatory effects of the p-PDT procedure 48 h following treatment and determine the association of inflammation with precancer burden, we performed a retrospective cohort study of 104 patients with AK of face or scalp treated with p-PDT between 2017 and 2019. Patients self-reported their side effects 48 h following p-PDT and took photographs of their face and scalp. Photographs were edited to define seven anatomic regions, and erythema was scored by four investigators.

RESULTS

Ninety-eight patients provided photographs suitable for erythema evaluation. Most patients experienced 2 or more side effects and some pain 48 h post-procedure. Females experienced more pain (p = 0.01) and side effects (p = 0.002) compared to males. AK burden was positively associated with post p-PDT erythema response (p < 0.0001) at all sites, but particularly in the temples (p = 0.002) and supralabial area (p = 0.009).

DISCUSSION

This study confirms a strong clinical inflammatory response after p-PDT. Severity of inflammation is positively associated with AK tumor burden, suggesting that post-treatment inflammation may be a pre-requisite for p-PDT efficacy. Interestingly, the results also identify certain gender-related differences in the severity of side effects experienced by patients post-PDT.