Low Photosensitizer Dose and Early Radiotherapy Enhance Antitumor Immune Response of Photodynamic Therapy-Based Dendritic Cell Vaccination

Structure-Activity Relationship of Benzophenazine Derivatives for Homogeneous and Heterogenized Photooxygenation Catalysis

Singlet oxygen is a powerful oxidant used in various applications, such as organic synthesis, medicine, and environmental remediation. Organic and inorganic photosensitizers are commonly used to generate this reactive species through energy transfer with the triplet ground state of oxygen. We describe here a series of novel benzophenazine derivatives as a promising class of photosensitizers for singlet oxygen photosensitization. In this study, we investigated the structure-activity relationship of these benzophenazine derivatives. Akin to a molecular compass, the southern fragment was first functionalized with either aromatic tertiary amines, alkyl tertiary amines, aromatic sulfur groups, alkyl sulfur groups, or cyclic ethers. Enhanced photophysical properties (in terms of triplet excited-state lifetime, absorption wavelength, triplet state energy, and O2 quenching capabilities) were obtained with cyclic ether and sulfur groups. Conversely, the presence of an amine moiety was detrimental to the photocatalysts. The western and northern fragments were also investigated and slightly undesirable to negligible changes in photophysical properties were observed. The most promising candidate was then immobilized on silica nanoparticles and its photoactivity was evaluated in the citronellol photooxidation reaction. A high NMR yield of 97 % in desired product was obtained, with only a slight decrease over several recycling runs (85 % in the fourth run). These results provide insights into the design of efficient photosensitizers for singlet oxygen generation and the development of heterogeneous systems.

De novo design of a nanoregulator for the dynamic restoration of ovarian tissue in cryopreservation and transplantation

The cryopreservation and transplantation of ovarian tissue underscore its paramount importance in safeguarding reproductive capacity and ameliorating reproductive disorders. However, challenges persist in ovarian tissue cryopreservation and transplantation (OTC-T), including the risk of tissue damage and dysfunction. Consequently, there has been a compelling exploration into the realm of nanoregulators to refine and enhance these procedures. This review embarks on a meticulous examination of the intricate anatomical structure of the ovary and its microenvironment, thereby establishing a robust groundwork for the development of nanomodulators. It systematically categorizes nanoregulators and delves deeply into their functions and mechanisms, meticulously tailored for optimizing ovarian tissue cryopreservation and transplantation. Furthermore, the review imparts valuable insights into the practical applications and obstacles encountered in clinical settings associated with OTC-T. Moreover, the review advocates for the utilization of microbially derived nanomodulators as a potent therapeutic intervention in ovarian tissue cryopreservation. The progression of these approaches holds the promise of seamlessly integrating nanoregulators into OTC-T practices, thereby heralding a new era of expansive applications and auspicious prospects in this pivotal domain.

Modified 5-aminolevulinic acid photodynamic therapy induces cutaneous squamous cell carcinoma cell pyroptosis via the JNK signaling pathway

Modified 5-aminolevulinic acid photodynamic therapy (M-PDT) is a novel therapeutic modality for cutaneous squamous cell carcinoma (cSCC) that is reported to be effective and well tolerated. However, the mechanisms underlying its antitumor effects are not fully understood. In this research, we investigated the effects of M-PDT on pyroptosis, a form of programmed cell death characterized by cell swelling, ruptures of cell membrane, and inflammatory cytokine release, in two human cSCC cell lines, SCL-1 and HSC-5. We found that M-PDT triggered pyroptosis in a dose-dependent manner, as evidenced by increased lactate dehydrogenase release, propidium iodide staining, and expression of pyroptosis-related proteins, such as NLR family pyrin domain containing 3 (NLRP3), N-terminal of gasdermin D (N-GSDMD), cleaved caspase-1, and mature interleukin 1 beta (IL-1B) in both cell lines. This process was inhibited by treatment with MCC950, an NLRP3-specific inhibitor, suggesting the involvement of the NLRP3 inflammasome in M-PDT-induced pyroptosis. We also demonstrated that M-PDT activated c-Jun N-terminal kinase (JNK) signaling, which is required for pyroptosis induction, as treatment with SP600125, a JNK inhibitor, suppressed the expression of pyroptosis-related proteins after M-PDT. JNK activation enhanced M-PDT-induced pyroptosis, highlighting the significance of the JNK pathway in M-PDT. Moreover, M-PDT increased intracellular reactive oxygen species (ROS) levels, which are responsible for JNK activation and pyroptosis induction. In summary, our results revealed that M-PDT triggers pyroptosis through ROS-mediated JNK activation and subsequent NLRP3 inflammasome activation in cSCC cells, providing a better understanding of the molecular mechanism of M-PDT and promoting its clinical application.

Immunotherapies inducing immunogenic cell death in cancer: insight of the innate immune system

Cancer immunotherapies include monoclonal antibodies, cytokines, oncolytic viruses, cellular therapies, and other biological and synthetic immunomodulators. These are traditionally studied for their effect on the immune system's role in eliminating cancer cells. However, some of these therapies have the unique ability to directly induce cytotoxicity in cancer cells by inducing immunogenic cell death (ICD). Unlike general immune stimulation, ICD triggers specific therapy-induced cell death pathways, based on the release of damage-associated molecular patterns (DAMPs) from dying tumour cells. These activate innate pattern recognition receptors (PRRs) and subsequent adaptive immune responses, offering the promise of sustained anticancer drug efficacy and durable antitumour immune memory. Exploring how onco-immunotherapies can trigger ICD, enhances our understanding of their mechanisms and potential for combination strategies. This review explores the complexities of these immunotherapeutic approaches that induce ICD, highlighting their implications for the innate immune system, addressing challenges in cancer treatment, and emphasising the pivotal role of ICD in contemporary cancer research.

Photodynamic Therapy-Induced Anti-Tumor Immunity: Influence Factors and Synergistic Enhancement Strategies

Photodynamic therapy (PDT) is an approved therapeutic procedure that exerts cytotoxic activity towards tumor cells by activating photosensitizers (PSs) with light exposure to produce reactive oxygen species (ROS). Compared to traditional treatment strategies such as surgery, chemotherapy, and radiation therapy, PDT not only kills the primary tumors, but also effectively suppresses metastatic tumors by activating the immune response. However, the anti-tumor immune effects induced by PDT are influenced by several factors, including the localization of PSs in cells, PSs concentration, fluence rate of light, oxygen concentration, and the integrity of immune function. In this review, we systematically summarize the influence factors of anti-tumor immune effects mediated by PDT. Furthermore, an update on the combination of PDT and other immunotherapy strategies are provided. Finally, the future directions and challenges of anti-tumor immunity induced by PDT are discussed.

Nanodrugs Reprogram Cancer-Associated Fibroblasts and Normalize Tumor Vasculatures for Sequentially Enhancing Photodynamic Therapy of Hepatocellular Carcinoma

Background

The failure of cancer photodynamic therapy (PDT) is largely ascribed to excessive stroma and defective vasculatures that restrain the photosensitizer permeation and the oxygen perfusion in tumors.

Method and Results

In this study, a nanodrug that integrated the cancer-associated fibroblast (CAF) regulation with tumor vessel normalization was tailored to sequentially sensitize PDT. The nanodrug exhibited high targeting towards CAFs and efficiently reversed the activated CAFs into quiescence, thus decreasing collagen deposition in the tumor microenvironment (TME), which overcame the protective physical barrier. Furthermore, the nanodrug regulated vascular endothelial cells and restored the tumor vasculatures, thereby improving vascular permeability. Based on the combined effects of reprogramming the TME, the nanodrug improved tumor accumulation of photosensitizers and alleviated hypoxia in the TME, which facilitated the subsequent PDT. Importantly, the nanodrug regulated the immunosuppressive TME by favoring the infiltration of immunostimulatory cells over immunosuppressive cells, which potentiated the PDT-induced immune response.

Conclusion

Our work demonstrates a sequential treatment strategy in which the combination of the CAF regulation and tumor vasculature normalization, followed by PDT, could be a promising modality for sensitizing tumor to PDT.

Photodynamic Therapy for Inflammatory and Cancerous Diseases of the Intestines: Molecular Mechanisms and Prospects for Application

Photodynamic therapy (PDT) is a minimally invasive treatment that effectively targets cancer and inflammatory diseases. It has gained recognition for its efficacy, low toxicity, and potential for repeated use. Colorectal cancer (CRC) and inflammatory bowel diseases (IBD), including Crohn's disease (CD), and ulcerative colitis (UC), impose a significant burden on global intestinal health, with increasing incidence and prevalence rates. PDT shows promise as an emerging approach for gastrointestinal disease treatment, particularly IBD and CRC. Extensive preclinical research has demonstrated the safety and effectiveness of PDT for IBD and CRC, while clinical studies are currently underway. This review provides an overview of the underlying mechanisms responsible for the anti-inflammatory and anti-tumor effects of PDT, offering insights into the clinical application of PDT in IBD and CRC treatment. It is expected that this review will serve as a valuable reference for future research on PDT for CRC and IBD, contributing to advancements in the treatment of inflammatory and cancerous diseases of the intestines.

Reinforcing the immunogenic cell death to enhance cancer immunotherapy efficacy

Immunogenic cell death (ICD) has been a revolutionary modality in cancer treatment since it kills primary tumors and prevents recurrent malignancy simultaneously. ICD represents a particular form of cancer cell death accompanied by production of damage-associated molecular patterns (DAMPs) that can be recognized by pattern recognition receptors (PRRs), which enhances infiltration of effector T cells and potentiates antitumor immune responses. Various treatment methods can elicit ICD involving chemo- and radio-therapy, phototherapy and nanotechnology to efficiently convert dead cancer cells into vaccines and trigger the antigen-specific immune responses. Nevertheless, the efficacy of ICD-induced therapies is restrained due to low accumulation in the tumor sites and damage of normal tissues. Thus, researchers have been devoted to overcoming these problems with novel materials and strategies. In this review, current knowledge on different ICD modalities, various ICD inducers, development and application of novel ICD-inducing strategies are summarized. Moreover, the prospects and challenges are briefly outlined to provide reference for future design of novel immunotherapy based on ICD effect.

Systematic Review of Photodynamic Therapy in Gliomas

Over the last 20 years, gliomas have made up over 89% of malignant CNS tumor cases in the American population (NIH SEER). Within this, glioblastoma is the most common subtype, comprising 57% of all glioma cases. Being highly aggressive, this deadly disease is known for its high genetic and phenotypic heterogeneity, rendering a complicated disease course. The current standard of care consists of maximally safe tumor resection concurrent with chemoradiotherapy. However, despite advances in technology and therapeutic modalities, rates of disease recurrence are still high and survivability remains low. Given the delicate nature of the tumor location, remaining margins following resection often initiate disease recurrence. Photodynamic therapy (PDT) is a therapeutic modality that, following the administration of a non-toxic photosensitizer, induces tumor-specific anti-cancer effects after localized, wavelength-specific illumination. Its effect against malignant glioma has been studied extensively over the last 30 years, in pre-clinical and clinical trials. Here, we provide a comprehensive review of the three generations of photosensitizers alongside their mechanisms of action, limitations, and future directions.

Evaluation of the impacts of photodynamic therapy on the prognosis of patients with hrHPV infection based on BTNL8 expression

Objective

The aim of this study was to evaluate the prognostic value of Butyrophilin-like protein 8 (BTNL8) expression in high-risk HPV (hrHPV) infection treated with photodynamic therapy.

Methods

A total of 93 patients with hrHPV infection were enrolled as research study subjects, along with 69 healthy women who served as controls. Serum samples were obtained from each participant, and BTNL8 levels were quantified. The patients were divided into high- and low-expression groups (n = 45 and n = 48, respectively), and both groups underwent photodynamic therapy. We recorded the following data: BTNL8 expression pre-treatment and at 3/6 months post-treatment, HPV negative conversion ratio, regression rate of low-grade squamous intraepithelial lesions (LSIL), incidence of adverse reactions, complication rate, serum inflammatory factors, persistence of HPV positivity, LSIL residue or recurrence, and incidence of high-grade cervical intraepithelial lesions (HCIL).

Results

Patients with HPV infection exhibited higher BTNL8 expression than healthy individuals. Compared to the low-expression group, the high-expression group showed increased HPV negative conversion ratios, LSIL regression rates, and levels of IL-17 and IL-23. This group also demonstrated decreased total complication rate, HPV positivity persistence, LSIL residue or recurrence, and IL-10 levels. Additionally, there was no significant difference between the two groups in terms of the number of adverse reactions and cases with LSIL residue/recurrence.

Conclusion

Serum BTNL8 expression may serve as a valuable tool for early screening and prognosis monitoring of patients with hrHPV infection.

Identification of a novel peptide targeting TIGIT to evaluate immunomodulation of 125I seed brachytherapy in HCC by near-infrared fluorescence

Introduction

Hepatocellular carcinoma (HCC) has very poor prognosis due to its immunosuppressive properties. An effective measure to regulate tumor immunity is brachytherapy, which uses 125I seeds planted into tumor. T cell immune receptors with immunoglobulin and ITIM domains (TIGIT) is highly expressed in HCC. The TIGIT-targeted probe is expected to be an effective tool for indicating immunomodulation of 125I seed brachytherapy in HCC. In this study, We constructed a novel peptide targeting TIGIT to evaluate the immune regulation of 125I seed brachytherapy for HCC by near-infrared fluorescence (NIRF).

Methods

Expression of TIGIT by immunofluorescence (IF) and flow cytometry (FCM) in different part and different differentiated human liver cancer tissues was verified. An optical fluorescence probe (Po-12) containing a NIRF dye and TIGIT peptide was synthesized for evaluating the modulatory effect of 125I seed brachytherapy. Lymphocytes uptake by Po-12 were detected by FCM and confocal microscopy. The distribution and accumulation of Po-12 in vivo were explored by NIRF imaging in subcutaneous and orthotopic tumors. IHC and IF staining were used to verify the expression of TIGIT in the tumors.

Results

TIGIT was highly expressed in HCC and increased with tumor differentiation. The dye-labeled peptide (Po-12) retained a stable binding affinity for the TIGIT protein in vitro. Accumulation of fluorescence intensity (FI) increased with time extended in subcutaneous H22 tumors, and the optimal point is 1 h. TIGIT was highly expressed on lymphocytes infiltrated in tumors and could be suppressed by 125I seed brachytherapy. Accumulation of Po-12-Cy5 was increased in tumor-bearing groups while declined in 125I radiation group.

5-ALA mediated photodynamic therapy with combined treatment improves anti-tumor efficacy of immunotherapy through boosting immunogenic cell death

Photodynamic therapy (PDT) is clinically promising in destructing primary tumors and immunotherapy awakes host immunity to control distant metastases. 5-aminolevulinic acid (5-ALA), a smart photosensitizer, converts into a physiological PDT agent with no dark toxicity in vivo. In this study, we found for the first time 5-ALA-PDT induced colorectal cancer (CRC) cells death by immunogenic cell death (ICD) upon AKT inhibition. Dying cancer cells induced by 5-ALA-PDT efficiently activated bone-marrow derived dendritic cells (BMDCs). Simultaneously, autophagy was observed after AKT inhibition by 5-ALA-PDT. Besides, we found cells died more remarkable by ICD under a circumstance of low occurrence of autophagy. To evaluate the effects of 5-ALA-PDT in vivo, we applied subcutaneous tumor mouse model and delightedly found 5-ALA-PDT induced a systemic antitumor immune response to control both primary tumors and distant metastases. Meanwhile, 5-ALA-PDT enhanced Th1 immunity, leading cytotoxic T lymphocyte response, and raised tumor-specific T cells. Combining with Chloroquine (CQ), 5-ALA-PDT further augmented tumor-specific immunity effects indicating protective role of autophagy. Together, the combination therapy of 5-ALA-PDT and autophagy inhibitor synergistically led to a novel clinical approach and potential ICD-based tumor vaccine for CRC patients.

Ex vivo purging of cancer cells from ovarian tissue using photodynamic therapy: a novel strategy to restore fertility in leukemia patients

STUDY QUESTION

Is it possible to purge leukemia cells from ovarian tissue (OT) fragments before transplantation?

SUMMARY ANSWER

Our photodynamic therapy (PDT) approach has been shown to efficiently destroy leukemia cells from tumor-infiltration mimicking models (TIMs), indicating the feasibility of this technique to purge OT samples.

WHAT IS KNOWN ALREADY

Autotransplantation of cryopreserved OT is the most suitable option to preserve fertility for prepubertal girls and women who require immediate cancer treatment. Up until now, more than 200 live births have already been reported after OT cryopreservation and transplantation. Leukemia is the 12th most common cancer in Europe among prepubertal girls and women of reproductive age and in 2020, the estimated number of new leukemia cases was higher than 33 000 in girls between 0 and 19 years old. Unfortunately, once their health has been restored, autotransplantation of cryopreserved OT for leukemia patients is not advised due to the high risk of transferring malignant cells back to the patient leading to leukemia recurrence.

STUDY DESIGN SIZE DURATION

To safely transplant the OT from leukemia patients and restore their fertility, our goal was to develop a PDT strategy to eliminate leukemia ex vivo. To this end, we designed OR141-loaded niosomes (ORN) to create the most effective formulation for ex vivo purging of acute myelogenous leukemia cells from OT fragments (n = 4). Moreover, to ensure that such treatments are not harmful to follicle survival and development so they can be deemed a potential fertility restoration alternative, the effect of the ORN-based PDT purging procedure on follicles was assessed after xenografting the photodynamic-treated OT in SCID mice (n = 5). The work was carried out between September 2020 and April 2022 at the Catholic University of Louvain.

PARTICIPANTS/MATERIALS SETTING METHODS

After establishing the best ORN formulation, our PDT approach was used to eradicate HL60 cells from ex vivo TIMs prepared by microinjection of a cancer cell suspension into OT fragments. The purging efficiency was analyzed by droplet digital polymerase chain reaction and immunohistochemical analyses. Additionally, we evaluated the effect of ORN-based PDT on follicle density, survival and development, and tissue quality in terms of fibrotic areas and vascularization after 7-day xenotransplantation to immunodeficient mice.

MAIN RESULTS AND THE ROLE OF CHANCE

The ex vivo purging of TIMs demonstrated that our PDT strategy could selectively eradicate the malignant cells from tissue fragments without affecting OT normal cells, as evidenced by PCR and immunohistochemical analysis. Regarding the effect of our PDT approach on follicle population and OT quality, our results after xenotransplantation revealed no significant difference between the follicle density of control (non-treated, grafted OT) and PDT-treated groups (2.38 ± 0.63 and 3.21 ± 1.94 morphologically normal follicles/mm², respectively). In addition, our findings showed that the control and PDT-treated OT could be equally vascularized (7.65 ± 1.45% and 9.89 ± 2.21%, respectively). Similarly, the proportions of fibrotic area did not differ between the control (15.96 ± 5.94%) and PDT-treated groups (13.32 ± 3.05%).

LARGE SCALE DATA

N/A.

LIMITATIONS REASONS FOR CAUTION

This study did not use OT fragments from leukemia patients, but TIMs created after injection of HL60 cells into OT from healthy patients. Therefore, while the results are promising, whether our PDT approach will be equally successful in eliminating malignant cells from leukemia patients remains to be assessed.

WIDER IMPLICATIONS OF THE FINDINGS

Our results showed that the purging procedure causes no significant impairment effect on follicle development and tissue quality, suggesting that our novel PDT procedure could be a promising strategy to destroy leukemia cells in fragments of OT, allowing safe transplantation in cancer survivors.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (FNRS-PDR Convention grant number T.0004.20 awarded to C.A.A.); Fondation Louvain (awarded to C.A.A.; a Ph.D. scholarship awarded to S.M., as part of a legacy from Mr Frans Heyes, and a Ph.D. scholarship awarded to A.D. as part of a legacy from Mrs. Ilse Schirmer); and Foundation Against Cancer (grant number 2018-042 awarded to A.C.). The authors declare no competing interests.

From targeted therapy to a novel way: Immunogenic cell death in lung cancer

Lung cancer (LC) is one of the most incident malignancies and a leading cause of cancer mortality worldwide. Common tumorigenic drivers of LC mainly include genetic alterations of EGFR, ALK, KRAS, BRAF, ROS1, and MET. Small inhibitory molecules and antibodies selectively targeting these alterations or/and their downstream signaling pathways have been approved for treatment of LC. Unfortunately, following initial positive responses to these targeted therapies, a large number of patients show dismal prognosis due to the occurrence of resistance mechanisms, such as novel mutations of these genes and activation of alternative signaling pathways. Over the past decade, it has become clear that there is no possible cure for LC unless potent antitumor immune responses are induced by therapeutic intervention. Immunogenic cell death (ICD) is a newly emerged concept, a form of regulated cell death that is sufficient to activate adaptive immune responses against tumor cells. It transforms dying cancer cells into a therapeutic vaccine and stimulates long-lasting protective antitumor immunity. In this review, we discuss the key targetable genetic aberrations and the underlying mechanism of ICD in LC. Various agents inducing ICD are summarized and the possibility of harnessing ICD in LC immunotherapy is further explored.

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.

Combined Photodynamic and Photothermal Therapy and Immunotherapy for Cancer Treatment: A Review

Photoactivation therapy based on photodynamic therapy (PDT) and photothermal therapy (PTT) has been identified as a tumour ablation modality for numerous cancer indications, with photosensitisers and photothermal conversion agents playing important roles in the phototherapy process, especially in recent decades. In addition, the iteration of nanotechnology has strongly promoted the development of phototherapy in tumour treatment. PDT can increase the sensitivity of tumour cells to PTT by interfering with the tumour microenvironment, whereas the heat generated by PTT can increase blood flow, improve oxygen supply and enhance the PDT therapeutic effect. In addition, tumour cell debris generated by phototherapy can serve as tumour-associated antigens, evoking antitumor immune responses. In this review, the research progress of phototherapy, and its research effects in combination with immunotherapy on the treatment of tumours are mainly outlined, and issues that may need continued attention in the future are raised.

Photodynamic therapy using OR141-loaded nanovesicles for eradication of leukemic cells from ovarian tissue

In 2020, the estimated number of new leukemia cases was higher than 30,000 in girls between 0 and 19 years old. Due to cancer treatment, some of these patients may lose both endocrine and reproductive functions. Transplantation of cryopreserved ovarian tissue is not advised after cancer remission because it has a high risk of reintroducing malignant cells in the patient, potentially leading to leukemia recurrence. To safely transplant the ovarian tissue from these patients and restore their fertility, our goal was to develop a photodynamic therapy (PDT) strategy to eliminate leukemia ex vivo. To this end, we designed, optimized, and characterized OR141-loaded niosomes (ORN) to develop the most effective formulation for ex vivo purging ovarian fragments from chronic myelogenous leukemia cells. After establishing the best ORN formulation, the PDT efficiency of optimized ORN was determined for human ovarian stromal cells and acute myeloid leukemia cell line (HL60). Blank niosomes treatment on ovarian stromal cells causes no significant toxicity, showing that the composition of the nanoparticle is not toxic. On the other hand, the in vitro studies showed that while ovarian stromal cells were still viable (82.04 ± 2.79%) after the treatment by 0.5 µM ORN, the same treatment yielded 95.43 ± 3.89% toxicity and cell death in the cancer cells. In conclusion, our results showed that our novel PDT procedure could be a promising strategy to destroy leukemia cells in ovarian tissue fragments allowing safe transplantation in cancer survivors.

Recent Insights into NIR-Light-Responsive Materials for Photothermal Cell Treatments

Controlling cells using photo-responsive materials is highly indispensable in the current biomedical sector. Considering the potential side effects of nanoparticles, it has become a challenge to control cells with photo-responsive materials. Recent studies have described several methods for controlling cell behavior using nanoparticles subjected to the near-infrared (NIR) laser light operating at the wavelength of 808 nm to 980 nm and at the power densities of 0.33 to 0.72 W·cm^-2. The challenge here is the preparation of biocompatible nanoparticles for both in vivo and in vitro studies and understanding cell behavior with an external light source recommended for biological application. Earlier studies have well documented many approaches and associated mechanisms for controlling cell behavior and the interaction between nanoparticles, cells, and appropriate external light sources. In this review, various nanomaterials such as metal nanomaterials and carbon-based nanomaterials are compared systematically regarding the effects of controlling cell behavior and inflammation by studying their mechanisms, route of administration, dose, and adverse effects such as toxicity and the interaction of nanoparticles with a specific wavelength of the light. Future directions should focus on stable and efficient light-responsive materials with minimal cytotoxicity.

Secure transplantation by tissue purging using photodynamic therapy to eradicate malignant cells

The field of photodynamic therapy (PDT) for treating various malignant neoplasms has been given researchers' attention due to its ability to be a selective and minimally invasive cancer therapy strategy. The possibility of tumor cell infection and hence high recurrence rates in cancer patients tends to restrict autologous transplantation. So, the photodynamic tissue purging process, which consists of selective photoinactivation of the malignant cells in the graft, is defined as a compromising strategy to purify contaminated tissues before transplantation. In this strategy, the direct malignant cells' death results from the reactive oxygen species (ROS) generation through the activation of a photosensitizer (PS) by light exposure in the presence of oxygen. Since new PS generations can effectively penetrate the tissue, PDT could be an ideal ex vivo tissue purging protocol that eradicates cancer cells derived from various malignancies. The challenge is that the applied pharmacologic ex vivo tissue purging should efficiently induce tumor cells with minor influence on normal tissue cells. This review aims to provide an overview of the current status of the most effective PDT strategies and PS development concerning their potential application in ex vivo purging before hematopoietic stem cell or ovarian tissue transplantation.

An Overview on Immunogenic Cell Death in Cancer Biology and Therapy

Immunogenic cell death (ICD) is a modality of regulated cell death that is sufficient to promote an adaptive immune response against antigens of the dying cell in an immunocompetent host. An important characteristic of ICD is the release and exposure of damage-associated molecular patterns, which are potent endogenous immune adjuvants. As the induction of ICD can be achieved with conventional cytotoxic agents, it represents a potential approach for the immunotherapy of cancer. Here, different aspects of ICD in cancer biology and treatment are reviewed.

Cancer Targeting and Diagnosis: Recent Trends with Carbon Nanotubes

Cancer belongs to a category of disorders characterized by uncontrolled cell development with the potential to invade other bodily organs, resulting in an estimated 10 million deaths globally in 2020. With advancements in nanotechnology-based systems, biomedical applications of nanomaterials are attracting increasing interest as prospective vehicles for targeted cancer therapy and enhancing treatment results. In this context, carbon nanotubes (CNTs) have recently garnered a great deal of interest in the field of cancer diagnosis and treatment due to various factors such as biocompatibility, thermodynamic properties, and varied functionalization. In the present review, we will discuss recent advancements regarding CNT contributions to cancer diagnosis and therapy. Various sensing strategies like electrochemical, colorimetric, plasmonic, and immunosensing are discussed in detail. In the next section, therapy techniques like photothermal therapy, photodynamic therapy, drug targeting, gene therapy, and immunotherapy are also explained in-depth. The toxicological aspect of CNTs for biomedical application will also be discussed in order to ensure the safe real-life and clinical use of CNTs.

Prostate Cancer Survivors Present Long-Term, Residual Systemic Immune Alterations

BACKGROUND

The development of cancer and anti-tumor therapies can lead to systemic immune alterations but little is known about how long immune dysfunction persists in cancer survivors.

METHODS

We followed changes in the cellular immune parameters of prostate cancer patients with good prognostic criteria treated with low dose rate brachytherapy before and up to 3 years after the initiation of therapy.

RESULTS

Patients before therapy had a reduced CD4+ T cell pool and increased regulatory T cell fraction and these alterations persisted or got amplified during the 36-month follow-up. A significant decrease in the total NK cell number and a redistribution of the circulating NK cells in favor of a less functional anergic subpopulation was seen in patients before therapy but tumor regression led to the regeneration of the NK cell pool and functional integrity. The fraction of lymphoid DCs was increased in patients both before therapy and throughout the whole follow-up. Increased PDGF-AA, BB, CCL5 and CXCL5 levels were measured in patients before treatment but protein levels rapidly normalized.

CONCLUSIONS

while NK cell dysfunction recovered, long-term, residual alterations persisted in the adaptive and partly in the innate immune system.

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

Photodynamic therapy (PDT) was discovered more than 100 years ago. Since then, many protocols and agents for PDT have been proposed for the treatment of several types of cancer. Traditionally, cell death induced by PDT was categorized into three types: apoptosis, cell death associated with autophagy, and necrosis. However, with the discovery of several other regulated cell death modalities in recent years, it has become clear that this is a rather simple understanding of the mechanisms of action of PDT. New observations revealed that cancer cells exposed to PDT can pass through various non-conventional cell death pathways, such as paraptosis, parthanatos, mitotic catastrophe, pyroptosis, necroptosis, and ferroptosis. Nowadays, immunogenic cell death (ICD) has become one of the most promising ways to eradicate tumor cells by activation of the T-cell adaptive immune response and induction of long-term immunological memory. ICD can be triggered by many anti-cancer treatment methods, including PDT. In this review, we critically discuss recent findings on the non-conventional cell death mechanisms triggered by PDT. Next, we emphasize the role and contribution of ICD in these PDT-induced non-conventional cell death modalities. Finally, we discuss the obstacles and propose several areas of research that will help to overcome these challenges and lead to the development of highly effective anti-cancer therapy based on PDT.

Multifunctional Nanosystems Powered Photodynamic Immunotherapy

Photodynamic Therapy (PDT) with the intrinsic advantages including non-invasiveness, spatiotemporal selectivity, low side-effects, and immune activation ability has been clinically approved for the treatment of head and neck cancer, esophageal cancer, pancreatic cancer, prostate cancer, and esophageal squamous cell carcinoma. Nevertheless, the PDT is only a strategy for local control of primary tumor, that it is hard to remove the residual tumor cells and inhibit the tumor metastasis. Recently, various smart nanomedicine-based strategies are developed to overcome the barriers of traditional PDT including the drawbacks of traditional photosensitizers, limited tissue penetrability of light, inefficient induction of tumor cell death and tumor resistance to the therapy. More notably, a growing number of studies have focused on improving the therapeutic efficiency by eliciting host immune system with versatile nanoplatforms, which heralds a broader clinical application prospect of PDT in the future. Herein, the pathways of PDT induced-tumor destruction, especially the host immune response is summarized, and focusing on the recent progress of nanosystems-enhanced PDT through eliciting innate immunity and adaptive immunity. We expect it will provide some insights for conquering the drawbacks current PDT and expand the range of clinical application through this review.

Induction of Immunogenic Cell Death by Photodynamic Therapy Mediated by Aluminum-Phthalocyanine in Nanoemulsion

Photodynamic therapy (PDT) has been clinically employed to treat mainly superficial cancer, such as basal cell carcinoma. This approach can eliminate tumors by direct cytotoxicity, tumor ischemia, or by triggering an immune response against tumor cells. Among the immune-related mechanisms of PDT, the induction of immunogenic cell death (ICD) in target cells is to be cited. ICD is an apoptosis modality distinguished by the emission of damage-associated molecular patterns (DAMP). Therefore, this study aimed to analyze the immunogenicity of CT26 and 4T1 treated with PDT mediated by aluminum-phthalocyanine in nanoemulsion (PDT-AlPc-NE). Different PDT-AlPc-NE protocols with varying doses of energy and AlPc concentrations were tested. The death mechanism and the emission of DAMPs-CRT, HSP70, HSP90, HMGB1, and IL-1β-were analyzed in cells treated in vitro with PDT. Then, the immunogenicity of these cells was assessed in an in vivo vaccination-challenge model with BALB/c mice. CT26 and 4T1 cells treated in vitro with PDT mediated by AlPc IC₅₀ and a light dose of 25 J/cm² exhibited the hallmarks of ICD, i.e., these cells died by apoptosis and exposed DAMPs. Mice injected with these IC₅₀ PDT-treated cells showed, in comparison to the control, increased resistance to the development of tumors in a subsequent challenge with viable cells. Mice injected with 4T1 and CT26 cells treated with higher or lower concentrations of photosensitizer and light doses exhibited a significantly lower resistance to tumor development than those injected with IC₅₀ PDT-treated cells. The results presented in this study suggest that both the photosensitizer concentration and light dose affect the immunogenicity of the PDT-treated cells. This event can affect the therapy outcomes in vivo.

A Facile Low-Dose Photosensitizer-Incorporated Dissolving Microneedles-Based Composite System for Eliciting Antitumor Immunity and the Abscopal Effect

Nanomedicine-based photodynamic therapy (PDT) for melanoma treatment has attracted great attention. However, the complex design of polymer nanoparticles and high doses of photosensitizers used in intravenous injections (for sufficient accumulation of drugs in tumor lesions) pose a huge challenge to the commercialization and further clinical application. Herein, we fabricated the carrier-free nanoassemblies of a chlorin e6 (L-Ce6 NAs)-integrated fast-dissolving microneedles patch (L-Ce6 MNs) enriching only about 3 μg of Ce6 in the needle tips via a facile fabrication method. The L-Ce6 MNs had sufficient mechanical strength to penetrate the skin and facilitated the transportation of L-Ce6 NAs to a depth of 200-500 μm under the skin, thereby achieving efficient and accurate drug delivery to tumor lesions. In a xenograft mouse melanoma model, the L-Ce6 MNs-based PDT with low dose of Ce6 (0.12 mg/kg) exerted efficient ablation of the primary lesions in situ through reactive oxygen species (ROS) generation. More importantly, a significant abscopal effect was also elicited by activating immunogenic cell death (ICD) and releasing danger-associated molecular patterns (DAMPs), which in turn promoted dendritic cells (DCs) maturation and the subsequent antigen presentation, thereby facilitating the T-cell-mediated immune response without synergetic immunotherapies. Collectively, our findings indicate the facile, controllable, and fast-dissolving microneedles patch with a low dose of photosensitizers presented great therapeutic potential for enhanced photoimmunotherapy.

Oxidative Damage Induced by Phototoxic Pheophorbide a 17-Diethylene Glycol Ester Encapsulated in PLGA Nanoparticles

Pheophorbide a 17-diethylene glycol ester (XL-8), is a promising high-active derivative of known photosensitizer chlorin e6 used in photodynamic therapy. However, high lipophilicity and poor tumor accumulation limit XL-8 therapeutic application. We developed a novel XL-8 loaded with poly(D,L-lactide-co-glycolide) nanoparticles using the single emulsion-solvent evaporation method. The nanoparticles possessed high XL-8 loading content (4.6%) and encapsulation efficiency (87.7%) and a small size (182 ± 19 nm), and negative surface charge (-22.2 ± 3.8 mV) contributed to a specific intracellular accumulation. Sustained biphasic XL-8 release from nanoparticles enhanced the photosensitizer photostability upon irradiation that could potentially reduce the quantity of the drug applied. Additionally, the encapsulation of XL-8 in the polymer matrix preserved phototoxic activity of the payload. The nanoparticles displayed enhanced cellular internalization. Flow cytometry and confocal laser-scanning microscopy studies revealed rapid XL-8 loaded nanoparticles distribution throughout the cell and initiation of DNA damage, glutathione depletion, and lipid peroxidation via reactive oxygen species formation. The novel nanoformulated XL-8 simultaneously revealed a significant phototoxicity accompanied with enhanced photostability, in contrast with traditional photosensitizers, and demonstrated a great potential for further in vivo studies.

Photodynamic Therapy-Mediated Immune Responses in Three-Dimensional Tumor Models

Photodynamic therapy (PDT) is a promising non-invasive phototherapeutic approach for cancer therapy that can eliminate local tumor cells and produce systemic antitumor immune responses. In recent years, significant efforts have been made in developing strategies to further investigate the immune mechanisms triggered by PDT. The majority of in vitro experimental models still rely on the two-dimensional (2D) cell cultures that do not mimic a three-dimensional (3D) cellular environment in the human body, such as cellular heterogeneity, nutrient gradient, growth mechanisms, and the interaction between cells as well as the extracellular matrix (ECM) and therapeutic resistance to anticancer treatments. In addition, in vivo animal studies are highly expensive and time consuming, which may also show physiological discrepancies between animals and humans. In this sense, there is growing interest in the utilization of 3D tumor models, since they precisely mimic different features of solid tumors. This review summarizes the characteristics and techniques for 3D tumor model generation. Furthermore, we provide an overview of innate and adaptive immune responses induced by PDT in several in vitro and in vivo tumor models. Future perspectives are highlighted for further enhancing PDT immune responses as well as ideal experimental models for antitumor immune response studies.

Cyanoarylporphyrazines with High Viscosity Sensitivity: A Step towards Dosimetry-Assisted Photodynamic Cancer Treatment

Despite the significant relevance of photodynamic therapy (PDT) as an efficient strategy for primary and adjuvant anticancer treatment, several challenges compromise its efficiency. In order to develop an "ideal photosensitizer" and the requirements applied to photosensitizers for PDT, there is still a need for new photodynamic agents with improved photophysical and photobiological properties. In this study, we performed a detailed characterization of two tetracyanotetra(aryl)porphyrazine dyes with 4-biphenyl (pz II) and 4-diethylaminophenyl (pz IV) groups in the periphery of the porphyrazine macrocycle. Photophysical properties, namely, fluorescence quantum yield and lifetime of both photosensitizers, demonstrate extremely high dependence on the viscosity of the environment, which enables them to be used as viscosity sensors. PzII and pz IV easily enter cancer cells and efficiently induce cell death under light irradiation. Using fluorescence lifetime imaging microscopy, we demonstrated the possibility of assessing local intracellular viscosity and visualizing viscosity changes driven by PDT treatment with the compounds. Thus, pz II and pz IV combine the features of potent photodynamic agents and viscosity sensors. These data suggest that the unique properties of the compounds provide a tool for PDT dosimetry and tailoring the PDT treatment regimen to the individual characteristics of each patient.

Photodynamic Therapy for the Treatment and Diagnosis of Cancer-A Review of the Current Clinical Status

Photodynamic therapy (PDT) has been used as an anti-tumor treatment method for a long time and photosensitizers (PS) can be used in various types of tumors. Originally, light is an effective tool that has been used in the treatment of diseases for ages. The effects of combination of specific dyes with light illumination was demonstrated at the beginning of 20th century and novel PDT approaches have been developed ever since. Main strategies of current studies are to reduce off-target effects and improve pharmacokinetic properties. Given the high interest and vast literature about the topic, approval of PDT as the first drug/device combination by the FDA should come as no surprise. PDT consists of two stages of treatment, combining light energy with a PS in order to destruct tumor cells after activation by light. In general, PDT has fewer side effects and toxicity than chemotherapy and/or radiotherapy. In addition to the purpose of treatment, several types of PSs can be used for diagnostic purposes for tumors. Such approaches are called photodynamic diagnosis (PDD). In this Review, we provide a general overview of the clinical applications of PDT in cancer, including the diagnostic and therapeutic approaches. Assessment of PDT therapeutic efficacy in the clinic will be discussed, since identifying predictors to determine the response to treatment is crucial. In addition, examples of PDT in various types of tumors will be discussed. Furthermore, combination of PDT with other therapy modalities such as chemotherapy, radiotherapy, surgery and immunotherapy will be emphasized, since such approaches seem to be promising in terms of enhancing effectiveness against tumor. The combination of PDT with other treatments may yield better results than by single treatments. Moreover, the utilization of lower doses in a combination therapy setting may cause less side effects and better results than single therapy. A better understanding of the effectiveness of PDT in a combination setting in the clinic as well as the optimization of such complex multimodal treatments may expand the clinical applications of PDT.

Nanomaterials-Based Photodynamic Therapy with Combined Treatment Improves Antitumor Efficacy Through Boosting Immunogenic Cell Death

Benefiting from the rapid development of nanotechnology, photodynamic therapy (PDT) is arising as a novel non-invasive clinical treatment for specific cancers, which exerts direct efficacy in destroying primary tumors by generating excessive cytotoxic reactive oxygen species (ROS). Notably, PDT-induced cell death is related to T cell-mediated antitumor immune responses through induction of immunogenic cell death (ICD). However, ICD elicited via PDT is not strong enough and is limited by immunosuppressive tumor microenvironment (ITM). Therefore, it is necessary to improve PDT efficacy through enhancing ICD with the combination of synergistic tumor therapies. Herein, the recent progress of nanomaterials-based PDT combined with chemotherapy, photothermal therapy, radiotherapy, and immunotherapy, employing ICD-boosted treatments is reviewed. An outlook about the future application in clinics of nanomaterials-based PDT strategies is also mentioned.

Restoring the Immunity in the Tumor Microenvironment: Insights into Immunogenic Cell Death in Onco-Therapies

Immunogenic cell death (ICD) elicited by cancer therapy reshapes the tumor immune microenvironment. A long-term adaptative immune response can be initiated by modulating cell death by therapeutic approaches. Here, the major hallmarks of ICD, endoplasmic reticulum (ER) stress, and damage-associated molecular patterns (DAMPs) are correlated with ICD inducers used in clinical practice to enhance antitumoral activity by suppressing tumor immune evasion. Approaches to monitoring the ICD triggered by antitumoral therapeutics in the tumor microenvironment (TME) and novel perspective in this immune system strategy are also reviewed to give an overview of the relevance of ICD in cancer treatment.

From molecules to nanovectors: Current state of the art and applications of photosensitizers in photodynamic therapy

Photodynamic therapy (PDT) is a concept based on a selective activation by light of drugs called photosensitizers (PS) leading to reactive oxygen species production responsible for cell destruction. Mechanisms of photodynamic reaction and cell photo-destruction following direct or indirect mechanisms will be presented as well as PS classification, from first generation molecules developed in the 1960 s to third generation vectorized PS with improved affinity for tumor cells. Many clinical applications in dermatology, ophthalmology, urology, gastroenterology, gynecology, neurosurgery and pneumology reported encouraging results in human tumor management. However, this interesting technique needs improvements that are currently investigated in the field of PS excitation by the design of new PS intended for two-photon excitation or for X-ray excitation. The former excitation technique is allowing better light penetration and preservation of healthy tissues while the latter is combining PDT and radiotherapy so that external light sources are no longer needed to generate the photodynamic effect. Nanotechnology can also improve the PS to reach the tumor cells by grafting addressing molecule and by increasing its aqueous solubility and consequently its bioavailability by encapsulation in synthetic or biogenic nanovector systems, ensuring good drug protection and targeting. Co-internalization of PS with magnetic nanoparticles in multifunctional vectors or stealth nanoplatforms allows a theranostic anticancer approach. Finally, a new category of inorganic PS will be presented with promising results on cancer cell destruction.

Novel porphyrazine-based photodynamic anti-cancer therapy induces immunogenic cell death

The immunogenicity of dying cancer cells determines the efficacy of anti-cancer therapy. Photodynamic therapy (PDT) can induce immunogenic cell death (ICD), which is characterized by the emission of damage-associated molecular patterns (DAMPs) from dying cells. This emission can trigger effective anti-tumor immunity. Only a few photosensitizers are known to induce ICD and, therefore, there is a need for development of new photosensitizers that can induce ICD. The purpose of this work was to analyze whether photosensitizers developed in-house from porphyrazines (pz I and pz III) can induce ICD in vitro and in vivo when used in PDT. We indetified the optimal concentrations of the photosensitizers and found that, at a light dose of 20 J/cm² (λ_ex 615-635 nm), both pz I and pz III efficiently induced cell death in cancer cells. We demonstrate that pz I localized predominantly in the Golgi apparatus and lysosomes while pz III in the endoplasmic reticulum and lysosomes. The cell death induced by pz I-PDT was inhibited by zVAD-fmk (apoptosis inhibitor) but not by ferrostatin-1 and DFO (ferroptosis inhibitors) or by necrostatin-1 s (necroptosis inhibitor). By contrast, the cell death induced by pz III-PDT was inhibited by z-VAD-fmk and by the necroptosis inhibitor, necrostatin-1 s. Cancer cells induced by pz I-PDT or pz III-PDT released HMGB1 and ATP and were engulfed by bone marrow-derived dendritic cells, which then matured and became activated in vitro. We demonstrate that cancer cells, after induction of cell death by pz I-PDT or pz III-PDT, are protective when used in the mouse model of prophylactic tumor vaccination. By vaccinating immunodeficient mice, we prove the role of the adaptive immune system in protecting against tumours. All together, we have shown that two novel porphyrazines developed in-house are potent ICD inducers that could be effectively applied in PDT of cancer.

Ferroptosis and Photodynamic Therapy Synergism: Enhancing Anticancer Treatment

Photodynamic therapy (PDT) is widely used in cancer treatment; however, several challenges compromise its efficiency. We propose a synergistic action between PDT and ferroptotic cell death. PDT acts as a source of reactive oxygen species for the Fenton reaction, which may reinforce ferroptosis induction and increase PDT efficacy in anticancer therapy.

Tumor cytotoxicity and immunogenicity of a novel V-jet neon plasma source compared to the kINPen

Recent research indicated the potential of cold physical plasma in cancer therapy. The plethora of plasma-derived reactive oxygen and nitrogen species (ROS/RNS) mediate diverse antitumor effects after eliciting oxidative stress in cancer cells. We aimed at exploiting this principle using a newly designed dual-jet neon plasma source (^Vjet) to treat colorectal cancer cells. A treatment time-dependent ROS/RNS generation induced oxidation, growth retardation, and cell death within 3D tumor spheroids were found. In TUM-CAM, a semi in vivo model, the ^Vjet markedly reduced vascularized tumors' growth, but an increase of tumor cell immunogenicity or uptake by dendritic cells was not observed. By comparison, the argon-driven single jet kINPen, known to mediate anticancer effects in vitro, in vivo, and in patients, generated less ROS/RNS and terminal cell death in spheroids. In the TUM-CAM model, however, the kINPen was equivalently effective and induced a stronger expression of immunogenic cancer cell death (ICD) markers, leading to increased phagocytosis of kINPen but not ^Vjet plasma-treated tumor cells by dendritic cells. Moreover, the ^Vjet was characterized according to the requirements of the DIN-SPEC 91315. Our results highlight the plasma device-specific action on cancer cells for evaluating optimal discharges for plasma cancer treatment.

Targeting immunogenic cancer cell death by photodynamic therapy: past, present and future

The past decade has witnessed major breakthroughs in cancer immunotherapy. This development has been largely motivated by cancer cell evasion of immunological control and consequent tumor resistance to conventional therapies. Immunogenic cell death (ICD) is considered one of the most promising ways to achieve total tumor cell elimination. It activates the T-cell adaptive immune response and results in the formation of long-term immunological memory. ICD can be triggered by many anticancer treatment modalities, including photodynamic therapy (PDT). In this review, we first discuss the role of PDT based on several classes of photosensitizers, including porphyrins and non-porphyrins, and critically evaluate their potential role in ICD induction. We emphasize the emerging trend of ICD induction by PDT in combination with nanotechnology, which represents third-generation photosensitizers and involves targeted induction of ICD by PDT. However, PDT also has some limitations, including the reduced efficiency of ICD induction in the hypoxic tumor microenvironment. Therefore, we critically evaluate strategies for overcoming this limitation, which is essential for increasing PDT efficiency. In the final part, we suggest several areas for future research for personalized cancer immunotherapy, including strategies based on oxygen-boosted PDT and nanoparticles. In conclusion, the insights from the last several years increasingly support the idea that PDT is a powerful strategy for inducing ICD in experimental cancer therapy. However, most studies have focused on mouse models, but it is necessary to validate this strategy in clinical settings, which will be a challenging research area in the future.

Understanding the glioblastoma tumor biology to optimize photodynamic therapy: From molecular to cellular events

Photodynamic therapy (PDT) has recently gained attention as an alternative treatment of malignant gliomas. Glioblastoma (GBM) is the most prevalent within tumors of the central nervous system (CNS). Conventional treatments for this CNS tumor include surgery, radiation, and chemotherapy. Surgery is still being considered as the treatment of choice. Even so, the poor prognosis and/or recurrence of the disease after applying any of these treatments highlight the urgency of exploring new therapies and/or improving existing ones to achieve the definitive eradication of tumor masses and remaining cells. PDT is a therapeutic modality that involves the destruction of tumor cells by reactive oxygen species induced by light, which were previously treated with a photosensitizing agent. However, in recent years, its experimental application has expanded to other effects that could improve overall performance against GBM. In the current review, we revisit the main advances of PDT for GBM management and also, the recent mechanistic insights about cellular and molecular aspects related to tumoral resistance to PDT of GBM.

Growing tool-kit of photosensitizers for clinical and non-clinical applications

Photosensitizers are photosensitive molecules utilized in clinical and non-clinical applications by taking advantage of light-mediated reactive oxygen generation, which triggers local and systemic cellular toxicity. Photosensitizers are used for diverse biological applications such as spatio-temporal inactivation of a protein in a living system by chromophore-assisted light inactivation, localized cell photoablation, photodynamic and immuno-photodynamic therapy, and correlative light-electron microscopy imaging. Substantial efforts have been made to develop several genetically encoded, chemically synthesized, and nanotechnologically driven photosensitizers for successful implementation in redox biology applications. Genetically encoded photosensitizers (GEPS) or reactive oxygen species (ROS) generating proteins have the advantage of using them in the living system since they can be manipulated by genetic engineering with a variety of target-specific genes for the precise spatio-temporal control of ROS generation. The GEPS variety is limited but is expanding with a variety of newly emerging GEPS proteins. Apart from GEPS, a large variety of chemically- and nanotechnologically-empowered photosensitizers have been developed with a major focus on photodynamic therapy-based cancer treatment alone or in combination with pre-existing treatment methods. Recently, immuno-photodynamic therapy has emerged as an effective cancer treatment method using smartly designed photosensitizers to initiate and engage the patient's immune system so as to empower the photosensitizing effect. In this review, we have discussed various types of photosensitizers, their clinical and non-clinical applications, and implementation toward intelligent efficacy, ROS efficiency, and target specificity in biological systems.

Pathological Mechanism of Photodynamic Therapy and Photothermal Therapy Based on Nanoparticles

The ultimate goal of phototherapy based on nanoparticles, such as photothermal therapy (PTT) which generates heat and photodynamic therapy (PDT) which not only generates reactive oxygen species (ROS) but also induces a variety of anti-tumor immunity, is to kill tumors. In addition, due to strong efficacy in clinical treatment with minimal invasion and negligible side effects, it has received extensive attention and research in recent years. In this paper, the generations of nanomaterials in PTT and PDT are described separately. In clinical application, according to the different combination pathway of nanoparticles, it can be used to treat different diseases such as tumors, melanoma, rheumatoid and so on. In this paper, the mechanism of pathological treatment is described in detail in terms of inducing apoptosis of cancer cells by ROS produced by PDT, immunogenic cell death to provoke the maturation of dendritic cells, which in turn activate production of CD4+ T cells, CD8+T cells and memory T cells, as well as inhibiting heat shock protein (HSPs), STAT3 signal pathway and so on.

Tumor microenvironment-related dendritic cell deficiency: a target to enhance tumor immunotherapy

Dendritic cells (DCs), as specialized antigen-presenting cells, are essential for the initiation of specific T cell responses in innate antitumor immunity and, in certain cases, support humoral responses to inhibit tumor development. Mounting evidence suggests that the DC system displays a broad spectrum of dysfunctional status in the tumor microenvironment (TME), which ultimately affects antitumor immune responses. DC-based therapy can restore the function of DCs in the TME, thus showing a promising potential in tumor therapy. In this review, we provide an overview of the DC deficiency caused by various factors in the TME and discuss proposed strategies to reverse DC deficiency and the applications of novel combinatorial DC-based therapy for immune normalization of the tumor.

Acidosis-Induced TGF-β2 Production Promotes Lipid Droplet Formation in Dendritic Cells and Alters Their Potential to Support Anti-Mesothelioma T Cell Response

For poorly immunogenic tumors such as mesothelioma there is an imperious need to understand why antigen-presenting cells such as dendritic cells (DCs) are not prone to supporting the anticancer T cell response. The tumor microenvironment (TME) is thought to be a major contributor to this DC dysfunction. We have reported that the acidic TME component promotes lipid droplet (LD) formation together with epithelial-to-mesenchymal transition in cancer cells through autocrine transforming growth factor-β2 (TGF-β2) signaling. Since TGF-β is also a master regulator of immune tolerance, we have here examined whether acidosis can impede immunostimulatory DC activity. We have found that exposure of mesothelioma cells to acidosis promotes TGF-β2 secretion, which in turn leads to LD accumulation and profound metabolic rewiring in DCs. We have further documented how DCs exposed to the mesothelioma acidic milieu make the anticancer vaccine less efficient in vivo, with a reduced extent of both DC migratory potential and T cell activation. Interestingly, inhibition of TGF-β2 signaling and diacylglycerol O-acyltransferase (DGAT), the last enzyme involved in triglyceride synthesis, led to a significant restoration of DC activity and anticancer immune response. In conclusion, our study has identified that acidic mesothelioma milieu drives DC dysfunction and altered T cell response through pharmacologically reversible TGF-β2-dependent mechanisms.

Current Approaches for Combination Therapy of Cancer: The Role of Immunogenic Cell Death

Cell death resistance is a key feature of tumor cells. One of the main anticancer therapies is increasing the susceptibility of cells to death. Cancer cells have developed a capability of tumor immune escape. Hence, restoring the immunogenicity of cancer cells can be suggested as an effective approach against cancer. Accumulating evidence proposes that several anticancer agents provoke the release of danger-associated molecular patterns (DAMPs) that are determinants of immunogenicity and stimulate immunogenic cell death (ICD). It has been suggested that ICD inducers are two different types according to their various activities. Here, we review the well-characterized DAMPs and focus on the different types of ICD inducers and recent combination therapies that can augment the immunogenicity of cancer cells.

Photodynamic Therapy-Based Dendritic Cell Vaccination Suited to Treat Peritoneal Mesothelioma

The potential of dendritic cell (DC)-based immunotherapy to treat cancer is, nowadays, well documented. Still, the clinical success of immune checkpoint inhibitors has dampened the interest in anticancer DC vaccination. For highly life-threatening tumors that are regarded as nonimmunogenic, such as mesothelioma, however, T helper 1 immunity-biased DC-based immunotherapy could still represent an attractive strategy. In this study, we took advantage of photodynamic therapy (PDT) to induce immunogenic cell death to generate mesothelioma cell lysates for DC priming and evaluated such a vaccine to treat peritoneal mesothelioma. We found that the white light in vitro activation of the photosensitizer OR141 led to mesothelioma cell death, together with the release of bona fide danger signals that promote DC maturation. The administration of a PDT-based DC vaccine to mice bearing peritoneal mesothelioma led to highly significant survival when compared with sham or control animals treated with anti-CTLA4 antibodies. This was further supported by a strong CD8⁺ and CD4⁺ T cell response, characterized by an increased proliferation, cytotoxic activities and the expression of activation markers, including interferon gamma (IFNγ). Moreover, the PDT-based DC vaccine led to a significant increase in IFNγ⁺ T cells infiltered within mesothelioma, as determined by flow cytometry and immunohistochemistry. Finally, in vivo tracking of intraperitoneally administered DCs led us to document rapid chemotaxis towards tumor-occupied lymphatics (vs. lipopolysaccharide (LPS)-treated DC). DCs pulsed with PDT-killed mesothelioma cells also exhibited a significant increase in CCR7 receptors, together with an intrinsic capacity to migrate towards the lymph nodes. Altogether, these results indicate that PDT-based DC vaccination is particularly suited to induce a potent immune response against peritoneal mesothelioma.