PDT-induced inflammatory and host responses

Enhancing cancer immunotherapy with photodynamic therapy and nanoparticle: making tumor microenvironment hotter to make immunotherapeutic work better

Cancer immunotherapy has made tremendous advancements in treating various malignancies. The biggest hurdle to successful immunotherapy would be the immunosuppressive tumor microenvironment (TME) and low immunogenicity of cancer cells. To make immunotherapy successful, the 'cold' TME must be converted to 'hot' immunostimulatory status to activate residual host immune responses. To this end, the immunosuppressive equilibrium in TME should be broken, and immunogenic cancer cell death ought to be induced to stimulate tumor-killing immune cells appropriately. Photodynamic therapy (PDT) is an efficient way of inducing immunogenic cell death (ICD) of cancer cells and disrupting immune-restrictive tumor tissues. PDT would trigger a chain reaction that would make the TME 'hot' and have ICD-induced tumor antigens presented to immune cells. In principle, the strategic combination of PDT and immunotherapy would synergize to enhance therapeutic outcomes in many intractable tumors. Novel technologies employing nanocarriers were developed to deliver photosensitizers and immunotherapeutic to TME efficiently. New-generation nanomedicines have been developed for PDT immunotherapy in recent years, which will accelerate clinical applications.

Feedback-Elevated Antitumor Amplifier of Self-Delivery Nanomedicine by Suppressing Photodynamic Therapy-Caused Inflammation

Inflammation activation is accompanied by tumor growth, migration, and differentiation. Photodynamic therapy (PDT) can trigger an inflammatory response to cause negative feedback of tumor inhibition. In this paper, a feedback-elevated antitumor amplifier is developed by constructing self-delivery nanomedicine for PDT and cascade anti-inflammation therapy. Based on the photosensitizer chlorin e6 (Ce6) and COX-2 inhibitor indomethacin (Indo), the nanomedicine is prepared via molecular self-assembly technology without additional drug carriers. It is exciting that the optimized nanomedicine (designated as CeIndo) possesses favorable stability and dispersibility in the aqueous phase. Moreover, the drug delivery efficiency of CeIndo is significantly improved, which could be effectively accumulated at the tumor site and internalized by tumor cells. Importantly, CeIndo not only exhibits a robust PDT efficacy on tumor cells but also drastically decreases the PDT-induced inflammatory response in vivo, resulting in feedback-elevated tumor inhibition. By virtue of the synergistic effect of PDT and cascade inflammation suppression, CeIndo tremendously reduces tumor growth and leads to a low side effect. This study presents a paradigm for the development of codelivery nanomedicine for enhanced tumor therapy through inflammation suppression.

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

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

Switchable ROS Scavenger/Generator for MRI-Guided Anti-Inflammation and Anti-Tumor Therapy with Enhanced Therapeutic Efficacy and Reduced Side Effects

Photosensitizer in photodynamic therapy (PDT)  accumulates in both tumor and adjacent normal tissue due to low selective biodistribution, results in undesirable side effect with limited clinic application. Herein, an intelligent nanoplatform is reported that selectively acts as reactive oxygen species (ROS) scavenger in normal tissue but as ROS generator in tumor microenvironment (TME) to differentially control ROS level in tumor and surrounding normal tissue during PDT. By down-regulating the produced ROS with dampened cytokine wave in normal tissue after PDT, the nanoplatform reduces the inflammatory response of normal tissue in PDT, minimizing the side effect and tumor metastasis in PDT. Alternatively, the nanoplatform switches from ROS scavenger to generator through the glutathione (GSH) responsive degradation in TME, which effectively improves the PDT efficacy with reduced GSH level and amplified oxidative stress in tumor. Simultaneously, the released Mn ions provide real-time and in situ signal change of magnetic resonance imaging (MRI) to monitor the reversal process of catalysis activity and achieve accurate tumor diagnosis. This TME-responsive ROS scavenger/generator with activable MRI contrast may provide a new dimension for design of next-generation PDT agents with precise diagnosis, high therapeutic efficacy, and low side effect.

Current Challenges and Opportunities of Photodynamic Therapy against Cancer

BACKGROUND

Photodynamic therapy (PDT) is an established, minimally invasive treatment for specific types of cancer. During PDT, reactive oxygen species (ROS) are generated that ultimately induce cell death and disruption of the tumor area. Moreover, PDT can result in damage to the tumor vasculature and induce the release and/or exposure of damage-associated molecular patterns (DAMPs) that may initiate an antitumor immune response. However, there are currently several challenges of PDT that limit its widespread application for certain indications in the clinic.

METHODS

A literature study was conducted to comprehensively discuss these challenges and to identify opportunities for improvement.

RESULTS

The most notable challenges of PDT and opportunities to improve them have been identified and discussed.

CONCLUSIONS

The recent efforts to improve the current challenges of PDT are promising, most notably those that focus on enhancing immune responses initiated by the treatment. The application of these improvements has the potential to enhance the antitumor efficacy of PDT, thereby broadening its potential application in the clinic.

Modified hollow mesoporous silica nanoparticles as immune adjuvant-nanocarriers for photodynamically enhanced cancer immunotherapy

Nanomedicine has demonstrated great potential in enhancing cancer immunotherapy. However, nanoparticle (NP)-based immunotherapy still has limitations in inducing effective antitumor responses and inhibiting tumor metastasis. Herein, polyethylenimine (PEI) hybrid thin shell hollow mesoporous silica NPs (THMSNs) were applied as adjuvant-nanocarriers and encapsulated with very small dose of photosensitizer chlorine e6 (Ce6) to realize the synergy of photodynamic therapy (PDT)/immunotherapy. Through PEI etching, the obtained Ce6@THMSNs exhibited enhanced cellular internalization and endosome/lysosome escape, which further improved the PDT efficacy of Ce6@THMSNs in destroying tumor cells. After PDT treatment, the released tumor-associated antigens with the help of THMSNs as adjuvants promoted dendritic cells maturation, which further boosted CD8⁺ cytotoxic T lymphocytes activation and triggered antitumor immune responses. The in vivo experiments demonstrated the significant potency of Ce6@THMSNs-based PDT in obliterating primary tumors and inducing persistent tumor-specific immune responses, thus preventing distant metastasis. Therefore, we offer a THMSNs-mediated and PDT-triggered nanotherapeutic system with immunogenic property, which can elicit robust antitumor immunity and is promising for future clinical development of immunotherapy.

Chondroitin sulfate-based prodrug nanoparticles enhance photodynamic immunotherapy via Golgi apparatus targeting

Photodynamic therapy (PDT) is an emerging therapeutic approach that can inhibit tumor growth by destroying local tumors and activating systemic antitumor immune responses. However, PDT can be ineffective because of photosensitizer aggregation, tumor-induced dendritic cells (DC_S) dysfunction and PDT-mediated immunosuppression. Therefore, we designed chondroitin sulfate-based prodrug nanoparticles for the co-delivery of the photosensitizer chlorin e6 (Ce6) and retinoic acid (RA), which can reduce PDT-mediated immunosuppression by disrupting the Golgi apparatus and blocking the production of immunosuppressive cytokines. Moreover, CpG oligodeoxynucleotide was combined as immunoadjuvant to promote the maturation of DCs. As expected, the strategy of Golgi apparatus targeting immunotherapy combined PDT was confirmed to relieve PDT-induced immunosuppression, showed excellent PDT antitumor efficacy in B16F10-subcutaneous bearing mice model. Thus, our finding offers a promising approach for photodynamic immunotherapy of advanced cancers. STATEMENT OF SIGNIFICANCE: Golgi apparatus has been shown to be a potential target of immunosuppression for producing several immunosuppressive cytokines. In this work, a Golgi apparatus-targeted prodrug nanoparticle was developed to enhance the immune response in photodynamic immunotherapy. The nanoparticle can target and disrupt the Golgi apparatus in tumor cells, which reduced PDT-mediated immunosuppression by blocking the production of immunosuppressive cytokines. This work provides an effective strategy of PDT in combination with the Golgi apparatus-targeted nanovesicle for enhanced cancer therapy.

Evaluation of the Antitumor Immune Response Following Photofrin-Based PDT in Combination with the Epigenetic Agent 5-Aza-2'-Deoxycytidine

Photofrin-based photodynamic therapy (PDT) is approved for clinical use by the US Food and Drug Administration and the European Medicines Agency and is among the most widely used photosensitizer for the treatment of cancer. It was broadly reported that both the innate and the adaptive arms of immune response can be activated by PDT and play a critical role in the anticancer outcome of this treatment. PDT leads to the induction of acute local inflammation that includes leukocyte infiltration as well as increased activation and production of pro-inflammatory factors and cytokines. These events can lead to the development of systemic and specific antitumor immune response. Combining Photofrin-PDT with the epigenetic agent 5-aza-2'-deoxycytidine results in potentiated antitumor effects in vivo. Understanding the molecular mechanisms underlying this phenomenon would be invaluable for clinical development of this therapeutic approach. This chapter describes a detailed protocol allowing evaluation of specific antitumor immune response induced by PDT.

A metal-polyphenolic nanosystem with NIR-II fluorescence-guided combined photothermal therapy and radiotherapy

Photothermal therapy (PTT) achieves substantive therapeutic progress in certain tumor types without exogenous agents but is hampered by the over-activated inflammatory response or tumor recurrence in some cases. Herein, we technically developed the metal-polyphenolic nanosystem with precise NIR-II fluorescence-imaging guidance for combining hafnium (Hf)-sensitized radiotherapy with PTT to regress tumor growth.

Multi-Functional Liposome: A Powerful Theranostic Nano-Platform Enhancing Photodynamic Therapy

Although photodynamic therapy (PDT) has promising advantages in almost non-invasion, low drug resistance, and low dark toxicity, it still suffers from limitations in the lipophilic nature of most photosensitizers (PSs), short half-life of PS in plasma, poor tissue penetration, and low tumor specificity. To overcome these limitations and enhance PDT, liposomes, as excellent multi-functional nano-carriers for drug delivery, have been extensively studied in multi-functional theranostics, including liposomal PS, targeted drug delivery, controllable drug release, image-guided therapy, and combined therapy. This review provides researchers with a useful reference in liposome-based drug delivery.

Photodynamic Therapy and Hyperthermia in Combination Treatment-Neglected Forces in the Fight against Cancer

Cancer is one of the leading causes of death in humans. Despite the progress in cancer treatment, and an increase in the effectiveness of diagnostic methods, cancer is still highly lethal and very difficult to treat in many cases. Combination therapy, in the context of cancer treatment, seems to be a promising option that may allow minimizing treatment side effects and may have a significant impact on the cure. It may also increase the effectiveness of anti-cancer therapies. Moreover, combination treatment can significantly increase delivery of drugs to cancerous tissues. Photodynamic therapy and hyperthermia seem to be ideal examples that prove the effectiveness of combination therapy. These two kinds of therapy can kill cancer cells through different mechanisms and activate various signaling pathways. Both PDT and hyperthermia play significant roles in the perfusion of a tumor and the network of blood vessels wrapped around it. The main goal of combination therapy is to combine separate mechanisms of action that will make cancer cells more sensitive to a given therapeutic agent. Such an approach in treatment may contribute toward increasing its effectiveness, optimizing the cancer treatment process in the future.

Synthesis of Multifunctional Nanoparticles for the Combination of Photodynamic Therapy and Immunotherapy

Programmed death-ligand 1 protein (PD-L1) has been posited to have a major role in suppressing the immune system during pregnancy, tissue allografts, autoimmune disease and other diseases, such as hepatitis. Photodynamic therapy uses light and a photosensitizer to generate singlet oxygen, which causes cell death (phototoxicity). In this work, photosensitizers (such as merocyanine) were immobilized on the surface of magnetic nanoparticles. One peptide sequence from PD-L1 was used as the template and imprinted onto poly(ethylene-co-vinyl alcohol) to generate magnetic composite nanoparticles for the targeting of PD-L1 on tumor cells. These nanoparticles were characterized using dynamic light scattering, high-performance liquid chromatography, Brunauer-Emmett-Teller analysis and superconducting quantum interference magnetometry. Natural killer-92 cells were added to these composite nanoparticles, which were then incubated with human hepatoma (HepG2) cells and illuminated with visible light for various periods. The viability and apoptosis pathway of HepG2 were examined using a cell counting kit-8 and quantitative real-time polymerase chain reaction. Finally, treatment with composite nanoparticles and irradiation of light was performed using an animal xenograft model.

Painless Photodynamic Therapy Triggers Innate and Adaptive Immune Responses in a Murine Model of UV-induced Squamous Skin Pre-cancer

Painless photodynamic therapy (p-PDT), which involves application of photosensitizer and immediate exposure to light to treat actinic keratosis (AK) in patients, causes negligible pain on the day of treatment but leads to delayed inflammation and effective lesion clearance (Kaw et al., J Am Acad Dermatol 2020). To better understand how p-PDT works, hairless mice with UV-induced AK were treated with p-PDT and monitored for 2 weeks. Lesion clearance after p-PDT was similar to clearance after conventional PDT (c-PDT). However, lesion biopsies showed minimal cell death and less production of reactive oxygen species (ROS) in p-PDT treated than in c-PDT-treated lesions. Interestingly, p-PDT triggered vigorous recruitment of immune cells associated with innate immunity. Neutrophils (Ly6G+) and macrophages (F4/80+) appeared at 4 h and peaked at 24 h after p-PDT. Damage-associated molecular patterns (DAMPs), including calreticulin, HMGB1, and HSP70, were expressed at maximum levels around 24 h post-p-PDT. Total T cells (CD3+) were increased at 24 h, whereas large increases in cytotoxic (CD8+) and regulatory (Foxp3+) T cells were observed at 1 and 2 weeks post-p-PDT. In summary, the ability of p-PDT to eliminate AK lesions, despite very little overt cellular damage, appears to involve stimulation of a local immune response.

Photodynamic/ photothermal therapy enhances neutrophil-mediated ibrutinib tumor delivery for potent tumor immunotherapy: More than one plus one?

Neutrophil-mediated drug-delivery systems have gained widespread attention owing to their superior efficacy in cancer therapy. Neutrophils, the most abundant white cells in peripheral blood, are known to migrate to inflamed tumors. Here, we elaborate on a novel strategy to enhance tumor infiltration of neutrophils by photodynamic/photothermal therapy (PDT/PTT) to deliver ibrutinib (IBR) nanocomplexes for cancer immunotherapy. DiR-loading liposomes (DiR-lipos) were administered to induce acute inflammation, and sialic acid (SA) derivative-coated IBR-loading nanocomplexes (SA-2@NCs) were fabricated for targeting activated peripheral blood neutrophils (PBNs). This in vitro and in vivo attempt, therefore, proved the hypothesis that inducing acute inflammation via PDT/PTT could facilitate the migration of PBNs, which could deliver SA-2@NCs into the tumor. The enhanced tumor delivery of SA-2@NCs was accompanied by enhanced antitumor T-cell immune responses in a mouse orthotopic breast cancer model. Our findings indicate that the combination of IBR-mediated immunotherapy with DiR-mediated PDT/PTT bring together two leading novel strategies, taking advantage of their synergistic mechanisms of action for a potent anti-tumor efficacy for breast cancer therapy.

Injectable Single-Component Peptide Depot: Autonomously Rechargeable Tumor Photosensitization for Repeated Photodynamic Therapy

The general practice of photodynamic therapy (PDT) comprises repeated multiple sessions, where photosensitizers are repeatedly administered prior to each operation of light irradiation. To address potential problems arising from the total overdose of photosensitizer by such repeated injections, we here introduce an internalizing RGD peptide (iRGD) derivative (Ppa-iRGDC-BK01) that self-aggregates into an injectable single-component supramolecular depot. Ppa-iRGDC-BK01 is designed as an in situ self-implantable photosensitizer so that it forms a depot by itself upon injection, and its molecular functions (cancer cell internalization and photosensitization) are activated by sustained release, tumor targeting, and tumor-selective proteolytic/reductive cleavage of the iRGD segment. The experimental and theoretical studies revealed that when exposed to body temperature, Ppa-iRGDC-BK01 undergoes thermally accelerated self-assembly to form a supramolecular depot through the hydrophobic interaction of the Ppa pendants and the reorganization of the interpeptide hydrogen bonding. It turned out that the self-aggregation of Ppa-iRGDC-BK01 into a depot exerts a multiple-quenching effect on the photosensitivity to effectively prevent nonspecific phototoxicity and protect it from photobleaching outside the tumor, while enabling autonomous tumor rephotosensitization by long sustained release, tumor accumulation, and intratumoral activation over time. We demonstrate that depot formation through a single peritumoral injection and subsequent quintuple laser irradiations at intervals resulted in complete eradication of the tumor. During the repeated PDT, depot-implanted normal tissues around the tumor exhibited no phototoxic damage under laser exposure. Our approach of single-component photosensitizing supramolecular depot, combined with a strategy of tumor-targeted therapeutic activation, would be a safer and more precise operation of PDT through a nonconventional protocol composed of one-time photosensitizer injection and multiple laser irradiations.

Antibody-Based Immunotherapy: Alternative Approaches for the Treatment of Metastatic Melanoma

Melanoma is the least common form of skin cancer and is associated with the highest mortality. Where melanoma is mostly unresponsive to conventional therapies (e.g., chemotherapy), BRAF inhibitor treatment has shown improved therapeutic outcomes. Photodynamic therapy (PDT) relies on a light-activated compound to produce death-inducing amounts of reactive oxygen species (ROS). Their capacity to selectively accumulate in tumor cells has been confirmed in melanoma treatment with some encouraging results. However, this treatment approach has not reached clinical fruition for melanoma due to major limitations associated with the development of resistance and subsequent side effects. These adverse effects might be bypassed by immunotherapy in the form of antibody–drug conjugates (ADCs) relying on the ability of monoclonal antibodies (mAbs) to target specific tumor-associated antigens (TAAs) and to be used as carriers to specifically deliver cytotoxic warheads into corresponding tumor cells. Of late, the continued refinement of ADC therapeutic efficacy has given rise to photoimmunotherapy (PIT) (a light-sensitive compound conjugated to mAbs), which by virtue of requiring light activation only exerts its toxic effect on light-irradiated cells. As such, this review aims to highlight the potential clinical benefits of various armed antibody-based immunotherapies, including PDT, as alternative approaches for the treatment of metastatic melanoma.

Photoacoustic visualization of the fluence rate dependence of photodynamic therapy

This study investigates the fluence rate effect, an essential modulating mechanism of photodynamic therapy (PDT), by using photoacoustic imaging method. To the best of our knowledge, this is the first time that the fluence rate dependence is investigated at a microscopic scale, as opposed to previous studies that are based on tumor growth/necrosis or animal surviving rate. This micro-scale examination enables subtle biological responses, including the vascular damage and the self-healing response, to be studied. Our results reveal the correlations between fluence rate and PDT efficacy/self-healing magnitude, indicating that vascular injuries induced by high fluence rates are more likely to recover and by low fluence rates (≤126 mW/cm²) are more likely to be permanent. There exists a turning point of fluence rate (314 mW/cm²), above which PDT practically produces no permanent therapeutic effect and damaged vessels can fully recover. These findings have practical significance in clinical setting. For cancer-related diseases, the 'effective fluence rate' is useful to provoke permanent destruction of tumor vasculature. Likewise, the 'non effective range' can be applied when PDT is used in applications such as opening the blood brain barrier to avoid permanent brain damage.

AIEgen-coupled upconversion nanoparticles eradicate solid tumors through dual-mode ROS activation

Reactive oxygen species (ROS) are essential for the regulation of antitumor immune responses, where they could induce immunogenic cell death, promote antigen presentation, and activate immune cells. Here, we report the development of near-infrared (NIR)-driven immunostimulants, based on coupling upconversion nanoparticles with aggregation-induced emission luminogens (AIEgens), to integrate the immunological effects of ROS for enhanced adaptive antitumor immune responses. Intratumorally injected AIEgen-upconversion nanoparticles produce high-dose ROS under high-power NIR irradiation, which induces immunogenic cell death and antigen release. These nanoparticles can also capture the released antigens and deliver them to lymph nodes. Upon subsequent low-power NIR treatment of lymph nodes, low-dose ROS are generated to further trigger efficient T cell immune responses through activation of dendritic cells, preventing both local tumor recurrence and distant tumor growth. The utility of dual-mode pumping power on AIEgen-coupled upconversion nanoparticles offers a powerful and controllable platform to activate adaptive immune systems for tumor immunotherapy.

Susceptibility and Resistance Mechanisms During Photodynamic Therapy of Melanoma

Melanoma is the most aggressive malignant skin tumor and arises from melanocytes. The resistance of melanoma cells to various treatments results in rapid tumor growth and high mortality. As a local therapeutic modality, photodynamic therapy has been successfully applied for clinical treatment of skin diseases. Photodynamic therapy is a relatively new treatment method for various types of malignant tumors in humans and, compared to conventional treatment methods, has fewer side effects, and is more accurate and non-invasive. Although several in vivo and in vitro studies have shown encouraging results regarding the potential benefits of photodynamic therapy as an adjuvant treatment for melanoma, its clinical application remains limited owing to its relative inefficiency. This review article discusses the use of photodynamic therapy in melanoma treatment as well as the latest progress made in deciphering the mechanism of tolerance. Lastly, potential targets are identified that may improve photodynamic therapy against melanoma cells.

Inhibition of IDO leads to IL-6-dependent systemic inflammation in mice when combined with photodynamic therapy

It was previously reported that the activation of antitumor immune response by photodynamic therapy (PDT) is crucial for its therapeutic outcome. Excessive PDT-mediated inflammation is accompanied by immunosuppressive mechanisms that protect tissues from destruction. Thus, the final effect of PDT strongly depends on the balance between the activation of an adoptive arm of immune response and a range of activated immunosuppressive mechanisms. Here, with flow cytometry and functional tests, we evaluate the immunosuppressive activity of tumor-associated myeloid cells after PDT. We investigate the antitumor potential of PDT combined with indoleamine 2,3-dioxygenase 1 (IDO) inhibitor in the murine 4T1 and E0771 orthotopic breast cancer models. We found that the expression of IDO, elevated after PDT, affects the polarization of T regulatory cells and influences the innate immune response. Our results indicate that, depending on a therapeutic scheme, overcoming IDO-induced immunosuppressive mechanisms after PDT can be beneficial or can lead to a systemic toxic reaction. The inhibition of IDO, shortly after PDT, activates IL-6-dependent toxic reactions that can be diminished by the use of anti-IL-6 antibodies. Our results emphasize that deeper investigation of the physiological role of IDO, an attractive target for immunotherapies of cancer, is of great importance.

NLRP3 Inflammasome Mediated Interleukin-1β Production in Cancer-Associated Fibroblast Contributes to ALA-PDT for Cutaneous Squamous Cell Carcinoma

Background

Long-term tumor control following PDT is a result of its direct effect on tumor and vasculature in combination with induction of inflammatory-reactions upregulating the immune system. When PDT induces necrosis of tumors and vascular system, an immune cascade can be initiated to release all kinds of cytokines including IL1β. This further leads to the activation of inflammatory-cells and hence death of tumor cells.

Methods

Ultraviolet irradiation was used to induce cSCC mice model, gene chip was used to screen inflammatory cytokines, qPCR, ELISA and implanted tumor mice model were used to verify the changes and important role of interleukin-1β, and WB preliminarily explored the production mechanism of interleukin-1β.

Results

Inflammatory cytokines and receptors transcript screening identify IL1r1 as the top4. After ALA-PDT, IL1r1 and IL1β increased in patients' biopsies, principally in mesenchymal cells. In vivo, the inhibition of ALA-PDT on tumor growth of cutaneous squamous cell carcinoma (cSCC) mice in the group with intralesional injection of anti-IL1β mAb or caspase1-inhibitor was significantly weaker than the control groups. Furthermore, NLRP3-inflammasome and p-p65/p65 were elevated after ALA-PDT mediated IL1β production in cancer-associated-fibroblasts.

Discussion

By means of activating NLRP3-inflammasome with IL1β production in CAFs, PDT stimulates local acute-inflammatory-response, which further promotes PDT effect for cSCC.

Quantitative assessment of changes in cellular morphology at photodynamic treatment in vitro by means of digital holographic microscopy

Temporal dependence of changes in the morphological characteristics of cells of two cultured lines of cancer origin, HeLa and A549, induced by photodynamic treatment with Radachlorin photosensitizer, have been monitored using digital holographic microscopy during first two hours after short-term irradiation. The observed post-treatment early dynamics of the phase shift in the transmitted wavefront indicated several distinct scenarios of cell behavior depending upon the irradiation dose. In particular the phase shift increased at low doses, which can be associated with apoptosis, while at high doses it decreased, which can be associated with necrosis. As shown, the two cell types responded differently to similar irradiation doses. Although the sequence of death scenarios with the increase of the irradiation dose was the same, each scenario was realized at substantially different doses. These findings suggest that the average phase shift of the transmitted wavefront can be used for quantitative non-invasive cell death characterization. The conclusions made were cofirmed by commonly used test assays using confocal fluorescent microscopy.

Topical treatment with oleocanthal extract in reducing inflammatory reactions after photodynamic therapy: a prospective quasi-experimental pilot study

OBJECTIVE

Photodynamic therapy (PDT) is an effective treatment against skin field cancerization. Its main side effect is local inflammation in the treated area. The phenolic compound oleocanthal (decarboxy methyl ligstroside aglycone), which is present in extra virgin olive oil (EVOO), has anti-inflammatory properties. The purpose of this study was to evaluate the topical efficacy of an oily fluid enriched with oleocanthal (OC) extract, in comparison with a conventional oily fluid, in reducing the degree of inflammatory reaction after conventional PDT.

METHODS

Quasi-experimental pilot study, before-after with a control group, performed with a cohort of consecutive patients diagnosed with actinic keratosis/field cancerization (AK/FC) in the forehead and/or scalp, treated by PDT. The study was carried out from April 2016 to November 2017 at a speciality hospital in southern Spain. A group of 24 consecutive patients received the topical application, three times daily for one week, of an emollient oily fluid in the area treated with PDT. Subsequently, another group, of 23 consecutive patients, received the same treatment pattern with an oily fluid enriched with OC extract. The post-PDT inflammatory reaction was measured by an independent member of the hospital's dermatology department, using the following visual scale of erythema (from 0 to 4).The assessment was conducted at 30 min and at 48 h post-PDT.

RESULTS

In the assessment at 48 h after treatment, the inflammation had improved more among the patients treated with OC (median: 25%, 95%CI: -5.3 to 28.5) than in the non-OC group (median: 0%; 95%CI: -45.2 to -6.2). The difference was statistically significant (p<0.01), and the Cohen's d value was 0.89 (large effect). At three months after PDT, a complete response had been obtained by 60.9% of the patients treated with OC compared to 29.2% of the non-OC group, and the difference was close to statistical significance (p=0.059).

CONCLUSIONS

The topical application of an oily fluid enriched with OC extract achieved a greater reduction in post-PDT cutaneous inflammation and a better treatment response, in comparison with the application of a conventional oily fluid.

Overcoming drug resistance with functional mesoporous titanium dioxide nanoparticles combining targeting, drug delivery and photodynamic therapy

We have designed a nano-drug delivery system ADH-1-HA-MTN, which can overcome the drug resistance of tumor cells based on an EMT cell targeting strategy in combination with PDT.

Oxygen self-sufficient fluorinated polypeptide nanoparticles for NIR imaging-guided enhanced photodynamic therapy

Oxygen self-sufficient fluorinated polypeptide nanoparticles have been synthesized via the loading of a NIR photosensitizer (BODIPY-Br₂) into a water-dispersible drug delivery system for high efficiency PDT.

Photochemical delivery of bleomycin induces T-cell activation of importance for curative effect and systemic anti-tumor immunity

Photochemical internalization (PCI) is a technology to enhance intracellular drug delivery by light-induced translocation of endocytosed therapeutics into the cytosol. The aim of this study was to explore the efficacy of PCI-based delivery of bleomycin and the impact on systemic anti-tumor immunity. Mouse colon carcinoma cells (CT26.CL25), stably expressing the bacterial β-galactosidase, were inoculated into the legs of athymic or immuno-competent BALB/c mice strains. The mice were injected with the photosensitizer AlPcS_2a and bleomycin (BLM) prior to tumor light exposure from a 670nm diode laser. Photochemical activation of BLM was found to induce synergistic inhibition of tumor growth as compared to the sum of the individual treatments. However, a curative effect was not observed in the athymic mice exposed to 30J/cm² of light while >90% of the thymic mice were cured after exposure to only 15J/cm² light. Cured thymic mice, re-challenged with CT26.CL25 tumor cells on the contralateral leg, rejected 57-100% of the tumor cells inoculated immediately and up to 2months after the photochemical treatment. T-cells from the spleen of PCI-treated mice were found to inhibit the growth of CT26.CL25 cells in naïve thymic mice with a 60% rejection rate. The results show that treatment of CT26.CL25 tumors in thymic mice by PCI of BLM induces a systemic anti-tumor immunity.

Photosensitization Priming of Tumor Microenvironments Improves Delivery of Nanotherapeutics via Neutrophil Infiltration

Remodeling of tumor microenvironments enables enhanced delivery of nanoparticles (NPs). This study shows that direct priming of a tumor tissue using photosensitization rapidly activates neutrophil infiltration that mediates delivery of nanotherapeutics into the tumor. A drug delivery platform is comprised of NPs coated with anti-CD11b antibodies (Abs) that target activated neutrophils. Intravital microscopy demonstrates that the movement of anti-CD11b Abs-decorated NPs (NPs-CD11b) into the tumor is mediated by neutrophil infiltration induced by photosensitization (PS) because the systemic depletion of neutrophils completely abolishes the nanoparticle tumor deposition. The neutrophil uptake of NPs does not alter neutrophil activation and transmigration. For cancer therapy in mice, tumor PS and photothermal therapy of anti-CD11b Abs-linked gold nanorods (GNRs-CD11b) are combined to treat the carcinoma tumor. The result indicates that neutrophil tumor infiltration enhances nanoparticle cancer therapy. The findings reveal that promoting tumor infiltration of neutrophils by manipulating tumor microenvironments could be a novel strategy to actively deliver nanotherapeutics in cancer therapies.

Near-Infrared-Triggered Photodynamic Therapy with Multitasking Upconversion Nanoparticles in Combination with Checkpoint Blockade for Immunotherapy of Colorectal Cancer

While immunotherapy has become a highly promising paradigm for cancer treatment in recent years, it has long been recognized that photodynamic therapy (PDT) has the ability to trigger antitumor immune responses. However, conventional PDT triggered by visible light has limited penetration depth, and its generated immune responses may not be robust enough to eliminate tumors. Herein, upconversion nanoparticles (UCNPs) are simultaneously loaded with chlorin e6 (Ce6), a photosensitizer, and imiquimod (R837), a Toll-like-receptor-7 agonist. The obtained multitasking UCNP-Ce6-R837 nanoparticles under near-infrared (NIR) irradiation with enhanced tissue penetration depth would enable effective photodynamic destruction of tumors to generate a pool of tumor-associated antigens, which in the presence of those R837-containing nanoparticles as the adjuvant are able to promote strong antitumor immune responses. More significantly, PDT with UCNP-Ce6-R837 in combination with the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) checkpoint blockade not only shows excellent efficacy in eliminating tumors exposed to the NIR laser but also results in strong antitumor immunities to inhibit the growth of distant tumors left behind after PDT treatment. Furthermore, such a cancer immunotherapy strategy has a long-term immune memory function to protect treated mice from tumor cell rechallenge. This work presents an immune-stimulating UCNP-based PDT strategy in combination with CTLA-4 checkpoint blockade to effectively destroy primary tumors under light exposure, inhibit distant tumors that can hardly be reached by light, and prevent tumor reoccurrence via the immune memory effect.

Photodynamic therapy using chloro-aluminum phthalocyanine decreases inflammatory response in an experimental rat periodontal disease model

BACKGROUND AND OBJECTIVE

Emerging evidence suggests that photodynamic therapy (PDT) can exhibit immunomodulatory activity. The purpose of the present study was to analyse cytokine profiles after application of PDT in gingival tissues of rats with ligature-induced periodontal disease (PD).

STUDY DESIGN/MATERIAL AND METHODS

Periodontal disease was induced through the introduction of a cotton thread around the first left mandibular molar, while the right side molars did not receive ligatures. After 7days of PD evolution, ligatures were removed from the left side, and the animals were randomically divided into the following treatment groups: I, rats without treatment; II, rats received chloro-aluminum phthalocyanine (AlClPc); III, rats received low-level laser alone; and IV, rats received AlClPc associated with low-level laser (PDT). The animals were killed 7days after the treatments, and the mandibles were histologically processed to assess morphological and immunohistochemical profile, while gingival tissues were removed for quantification of tumor necrosis factor (TNF)-α, interleukin (IL-)1β and IL-10 expression (by ELISA).

RESULTS

Histomorphological analysis of periodontal tissues demonstrated that PDT-treated animals show tissue necrosis, as well as lower TNF- α expression, compared to ligatured animals treated with AlClPc alone.

CONCLUSIONS

It was concluded that PDT using AlClPc entrapped in a lipid nanoemulsion may be useful in therapies, because of immunomodulatory effects that decreased the inflammatory response and cause tissue destruction.

Fluorinated polymer–photosensitizer conjugates enable improved generation of ROS for anticancer photodynamic therapy

Fluorous nanoparticles enhances oxygen uptake as a PDT carrier for skin cancers.

Long-Circulating Au-TiO2 Nanocomposite as a Sonosensitizer for ROS-Mediated Eradication of Cancer

Although sonodynamic therapy (SDT) has emerged as a potential alternative to conventional photodynamic therapy, the low quantum yield of the sonosensitizer such as TiO₂ nanoparticles (NPs) is still a major concern. Here, we have developed hydrophilized Au-TiO₂ nanocomposites (HAu-TiO₂ NCs) as sonosensitizers for improved SDT. The physicochemical properties of HAu-TiO₂ NCs were thoroughly studied and compared with their counterparts without gold deposition. Upon exposure of HAu-TiO₂ NCs to ultrasound, a large quantity of reactive oxygen species (ROS) were generated, leading to complete suppression of tumor growth after their systemic administration in vivo. Overall, it was evident that the composites of gold with TiO₂ NPs significantly augmented the levels of ROS generation, implying their potential as SDT agents for cancer therapy.

Basso F, de Souza Costa CA, Bagnato VS, Mima EGDO, Pavarina AC. Treatment of Oral Candidiasis Using Photodithazine®- Mediated Photodynamic Therapy In Vivo

This study evaluated the effectiveness of antimicrobial photodynamic therapy (aPDT) in the treatment of oral candidiasis in a murine model using Photodithazine^® (PDZ). This model of oral candidiasis was developed to allow the monitoring of the infection and the establishment of the aPDT treatment. Six-week-old female mice were immunosuppressed and inoculated with C. albicans to induce oral candidiasis. PDZ-mediated aPDT and nystatin treatment were carried out for 5 consecutive days with one application per day. The macroscopic evaluation of oral lesions was performed. After each treatment, the tongue was swabbed to recover C. albicans cells. Viable colonies were quantified and the number of CFU/ml determined. The animals were sacrificed 24 hours and 7 days after treatment and the tongues were surgically removed for histological analysis and analysis of inflammatory cytokines expression (IL-1, TNF-α and IL-6) by RT-qPCR. Data were analyzed by two-way ANOVA. PDZ-mediated aPDT was as effective as Nystatin (NYS group) in the inactivation of C. albicans, reducing 3 and 3.2 logs₁₀ respectively, 24 h after treatment (p<0.05). Animals underwent PDZ-mediated aPDT showed complete remission of oral lesions, while animals treated with NYS presented partial remission of oral lesions in both periods assessed. Histological evaluation revealed mild inflammatory infiltrate in the groups treated with aPDT and NYS in both periods assessed. The aPDT induced the TNF-α expression when compared with the control (P-L-) (p<0.05), 24 h and 7 days after treatment. In summary, the murine model developed here was able to mimic the infection and PDZ-mediated aPDT was effective to treat mice with oral candidiasis.

Low dose of GRP78-targeting subtilase cytotoxin improves the efficacy of photodynamic therapy in vivo

Photodynamic therapy (PDT) exerts direct cytotoxic effects on tumor cells, destroys tumor blood and lymphatic vessels and induces local inflammation. Although PDT triggers the release of immunogenic antigens from tumor cells, the degree of immune stimulation is regimen-dependent. The highest immunogenicity is achieved at sub-lethal doses, which at the same time trigger cytoprotective responses, that include increased expression of glucose-regulated protein 78 (GRP78). To mitigate the cytoprotective effects of GRP78 and preserve the immunoregulatory activity of PDT, we investigated the in vivo efficacy of PDT in combination with EGF-SubA cytotoxin that was shown to potentiate in vitro PDT cytotoxicity by inactivating GRP78. Treatment of immunocompetent BALB/c mice with EGF-SubA improved the efficacy of PDT but only when mice were treated with a dose of EGF-SubA that exerted less pronounced effects on the number of T and B lymphocytes as well as dendritic cells in mouse spleens. The observed antitumor effects were critically dependent on CD8+ T cells and were completely abrogated in immunodeficient SCID mice. All these results suggest that GRP78 targeting improves in vivo PDT efficacy provided intact T-cell immune system.

ROS-generating TiO2 nanoparticles for non-invasive sonodynamic therapy of cancer

The non-invasive photodynamic therapy has been limited to treat superficial tumours, primarily ascribed to poor tissue penetration of light as the energy source. Herein, we designed a long-circulating hydrophilized titanium dioxide nanoparticle (HTiO2 NP) that can be activated by ultrasound to generate reactive oxygen species (ROS). When administered systemically to mice, HTiO2 NPs effectively suppressed the growth of superficial tumours after ultrasound treatments. In tumour tissue, the levels of proinflammatory cytokines were elevated several fold and intense vascular damage was observed. Notably, ultrasound treatments with HTiO2 NPs also suppressed the growth of deeply located liver tumours at least 15-fold, compared to animals without ultrasound treatments. This study provides the first demonstration of the feasibility of using HTiO2 NPs as sensitizers for sonodynamic therapy in vivo.

Immunological aspects of antitumor photodynamic therapy outcome

Photodynamic therapy (PDT) of cancer is an efficient and promising therapeutic modality approved for the treatment of several types of tumors and non-malignant diseases. It involves administration of a non-toxic photosensitizer followed by illumination of the tumor site with a harmless visible light. A light activated photosensitizer can transfer its energy directly to molecular oxygen, leading to production of highly toxic reactive oxygen species (ROS). Antitumor effects of PDT result from the combination of three independent mechanisms involving direct cytotoxicity to tumor cells, destruction of tumor vasculature and induction of the acute local inflammatory response. PDT-mediated inflammatory reaction is accompanied by tumor infiltration of the leukocytes, enhanced production of pro-inflammatory factors and cytokines. Photodynamic therapy is able to effectively stimulate both the innate and the adaptive arm of the immune system. In consequence, this regimen can lead to development of systemic and specific antitumor immune response. However, there are limited studies suggesting that under some specific circumstances, PDT on its own may exert some immunosuppressive effects leading to activation of immunosuppressive cells or cytokines production. In this report we briefly review all immunological aspects of PDT treatment.

A Surgical View of Photodynamic Therapy in Oncology: A Review

Clinical photodynamic therapy (PDT) has existed for over 30 years, and its scientific basis has been known and investigated for well over 100 years. The scientific foundation of PDT is solid and its application to cancer treatment for many common neoplastic lesions has been the subject of a huge number of clinical trials and observational studies. Yet its acceptance by many clinicians has suffered from its absence from the undergraduate and/or postgraduate education curricula of surgeons, physicians, and oncologists. Surgeons in a variety of specialties many with years of experience who are familiar with PDT bear witness in many thousands of publications to its safety and efficacy as well as to the unique role that it can play in the treatment of cancer with its targeting precision, its lack of collateral damage to healthy structures surrounding the treated lesions, and its usage within minimal access therapy. PDT is closely related to the fluorescence phenomenon used in photodiagnosis. This review aspires both to inform and to present the clinical aspect of PDT as seen by a surgeon.

Anti-tumor immunity of BAM-SiPc-mediated vascular photodynamic therapy in a BALB/c mouse model

In recent decades, accumulating evidence from both animal and clinical studies has suggested that a sufficiently activated immune system may strongly augment various types of cancer treatment, including photodynamic therapy (PDT). Through the generation of reactive oxygen species, PDT eradicates tumors by triggering localized tumor damage and inducing anti-tumor immunity. As the major component of anti-tumor immunity, the involvement of a cell-mediated immune response in PDT has been well investigated in the past decade, whereas the role of humoral immunity has remained relatively unexplored. In the present investigation, using the photosensitizer BAM-SiPc and the CT26 tumor-bearing BALB/c mouse model, it was demonstrated that both cell-mediated and humoral adaptive immune components could be involved in PDT. With a vascular PDT (VPDT) regimen, BAM-SiPc could eradicate the tumors of ∼70% of tumor-bearing mice and trigger an anti-tumor immune response that could last for more than 1 year. An elevation of Th2 cytokines was detected ex vivo after VPDT, indicating the potential involvement of a humoral response. An analysis of serum from the VPDT-cured mice also revealed elevated levels of tumor-specific antibodies. Moreover, this serum could effectively hinder tumor growth and protect the mice against further re-challenge in a T-cell-dependent manner. Taken together, these results show that the humoral components induced after BAM-SiPc-VPDT could assist the development of anti-tumor immunity.

Targeting Epigenetic Processes in Photodynamic Therapy-Induced Anticancer Immunity

Photodynamic therapy (PDT) of cancer is an approved therapeutic procedure that generates oxidative stress leading to cell death of tumor and stromal cells. Cell death resulting from oxidative damage to intracellular components leads to the release of damage-associated molecular patterns (DAMPs) that trigger robust inflammatory response and creates local conditions for effective sampling of tumor-associated antigens (TAA) by antigen-presenting cells. The latter can trigger development of TAA-specific adaptive immune response. However, due to a number of mechanisms, including epigenetic regulation of TAA expression, tumor cells evade immune recognition. Therefore, numerous approaches are being developed to combine PDT with immunotherapies to allow development of systemic immunity. In this review, we describe immunoregulatory mechanisms of epigenetic treatments that were shown to restore the expression of epigenetically silenced or down-regulated major histocompatibility complex molecules as well as TAA. We also discuss the results of our recent studies showing that epigenetic treatments based on administration of methyltransferase inhibitors in combination with PDT can release effective mechanisms leading to development of antitumor immunity and potentiated antitumor effects.

Photodynamic therapy using talaporfin sodium induces concentration-dependent programmed necroptosis in human glioblastoma T98G cells

Photodynamic therapy (PDT) using photosensitizer induces several types of cell death, such as apoptosis, necrosis, and autophagy, depending on the PDT procedure, photosensitizer type, and cell type. We previously demonstrated that PDT using the photosensitizer talaporfin sodium (mono-L-aspartyl chlorine e6, NPe6; NPe6-PDT) induces both mitochondrial apoptotic and necrotic cell death in human glioblastoma T98G cells. However, details regarding the mechanism of necrosis caused by NPe6-PDT are unclear. Here, we investigated whether or not necroptosis, a recently suggested form of programmed necrosis, is involved in the necrotic cell death of NPe6-PDT-treated T98G cells. Leakage of lactate dehydrogenase (LDH) from the cell layer into conditioned medium was significantly increased by NPe6 (25 and 50 μg/ml)-PDT, indicating that NPe6-PDT induces necrosis in these cells. NPe6 (25 μg/ml)-PDT treatment also induced conversion of microtubule-associated protein 1 light-chain 3 (LC3)-I into phosphatidylethanolamine-conjugated LC3-II accompanying autophagosome formation, indicators of autophagy; however, of note, NPe6 (50 μg/ml)-PDT did not induce such autophagic changes. In addition, both necrostatin-1 (a necroptosis inhibitor) and knockdown of necroptotic pathway-related proteins [e.g., receptor interacting serine-threonine kinase (RIP)-1, RIP-3, and mixed lineage kinase domain-like protein (MLKL)] inhibited leakage of LDH caused by NPe6 (25 μg/ml)-PDT. Taken together, the present findings revealed that NPe6-PDT-induced necrotic cell death is mediated in part by the necroptosis pathway in glioblastoma T98G cells.

Clinical use of photodynamic therapy in ocular tumors

Although the introduction of intravitreal anti-vascular endothelial growth factor drugs reduced the indications for photodynamic therapy in ophthalmology, it may still be used in various ocular tumors. Although many studies have shown that photodynamic therapy is effective in ocular tumors, the literature consists of case reports and series. In this review, we systematically performed a meta-analysis for the use of photodynamic therapy in circumscribed choroidal hemangioma, diffuse choroidal hemangioma, retinal capillary hemangioma, von Hippel-Lindau angiomatosis, choroidal melanoma, retinal astrocytoma, retinoblastoma, eyelid tumors, conjunctival tumors, and choroidal metastasis.

Macrophage targeted theranostics as personalized nanomedicine strategies for inflammatory diseases

Inflammatory disease management poses challenges due to the complexity of inflammation and inherent patient variability, thereby necessitating patient-specific therapeutic interventions. Theranostics, which integrate therapeutic and imaging functionalities, can be used for simultaneous imaging and treatment of inflammatory diseases. Theranostics could facilitate assessment of safety, toxicity and real-time therapeutic efficacy leading to personalized treatment strategies. Macrophages are an important cellular component of inflammatory diseases, participating in varied roles of disease exacerbation and resolution. The inherent phagocytic nature, abundance and disease homing properties of macrophages can be targeted for imaging and therapeutic purposes. This review discusses the utility of theranostics in macrophage ablation, phenotype modulation and inhibition of their inflammatory activity leading to resolution of inflammation in several diseases.