Induction of tumor immunity by photodynamic therapy

Electrically activated polymetallic nanocrystals for long-term tumor suppression via oxygen-independent ROS generation and electro-immunotherapy

The low oxidation level and immunosuppressive microenvironment within hypoxic tumor tissue are critical factors contributing to the inefficacy of various anti-tumor strategies. Herein, we have designed a novel intravenous injection nanoplatform to conduct electro-immunotherapy, based on phospholipid-modified PtPd nanocrystals loaded with the immunoregulator IPI549 (LP@Pt-Pd@IPI549 nanoparticles, LPPI). LPPI responds to reactive oxygen species (ROS), triggering a cascade of therapeutic effects that overcome hypoxia-related resistance and effectively eradicate hypoxic tumors. Firstly, under electric field exposure, LPPI relied on water rather than oxygen to generate abundant ROS under hypoxic conditions for tumor electrodynamic therapy (EDT). Moreover, the generated ROS further induced the disintegration of the outer phospholipid membrane of LPPI, leading to the release of the immunoregulator and inhibition of myeloid-derived suppressor cells (MDSCs), triggering cascade immune responses. Additionally, the immunomodulatory effects of IPI549, in synergy with the immunogenic cell death (ICD) induced by EDT, reversed the immunosuppressive microenvironment contributing to tumor resistance. In summary, EDT transiently killed tumor cells while simultaneously generating antigen release, instigating an adaptive immune response for electro-immunotherapy, resulting in a potent and long-lasting tumor inhibition effect.

Successful pregnancy and delivery after HiPorfin photodynamic therapy for cervical high-grade squamous intraepithelial lesion

OBJECTIVE

The study analyzed HiPorfin-Photodynamic therapy (PDT) for young women with cervial high-grade squamous intraepithelial lesion (HSIL) and evaluated the impact of PDT on their pregnancy and delivery.

METHODS

Retrospective analysis of 4 patients (21-33 years old) were treated with HiPorfin® (2 mg/kg) PDT in 2019-2022. 1 patient suffered from cervical intraepithelial neoplasia (CIN)Ⅱ and 3 patients from CIN Ⅲ. 630 nm laser light irradiated the cervical surface and endocervical canal with light dose of 150 J/cm2 and 100-120 J/cm2 respectively.

RESULTS

The median observation time period was 40.5 months. Cure rate, HPV eradication rate and negative conversion rate of cytology were all 100.0 % at 3, 6 and 12 months. All cervical canal lesions completely turned negative. No recurrence occurred during the long-term follow-up period. None of patients suffered from infertility. Three patients delivered vaginally and one delivered by C-section to healthy infants at term.

CONCLUSION

HiPorfin® PDT for cervical HSIL was proved to be a safe method without adverse effects on female fertility and allowing these women to have healthy, full-term children.

Photodynamic therapy with HiPorfin for cervical squamous intraepithelial lesion at childbearing age

OBJECTIVE

To evaluate the clinical efficacy and safety of HiPorfin® photodynamic therapy (PDT) in the treatment of young women at reproductive age with high-grade squamous intraepithelial lesion (HSIL) of the cervix.

METHODS

Prospective study of 41 patients aged 28.8 ± 4.6 years old with cervical intraepithelial neoplasia (CIN) Ⅱ-Ⅲ at Peking University Shenzhen Hospital from March 2019 to January 2023. HiPorfin® (2 mg/kg) was infused intravenously, and 48-72 h later, 630-nm laser irradiation was performed in cervical canal and cervical surface with an irradiation dose of 100-120 J/cm2 and 150 J/cm2 respectively.

RESULTS

All 41 patients with no recurrence had been observed at least 12 months follow-up period after PDT. The number of nulliparous women was 30 (30/41, 73.2 %). CIN Ⅱ were 22 cases (22/41,53.7 %) and CIN Ⅲ were 19 cases (19/41,46.3 %). Complete response (CR) was in 95.5 % (21/22) patients with CIN Ⅱ and 78.9 % (15/19) patients with CIN Ⅲ at 6 months follow-up. Meanwhile, CR rate was 100.0 % (22/22) and 84.2 % (16/19) in CIN Ⅱ and CIN Ⅲ group respectively at 12 months. Pre-treatment, all patients (41/41,100 %) were Human papilloma virus (HPV) positive. HPV eradication rate was 63.4 % (26/41), 73.2 % (30/41) and 92.7 % (38/41) at 3, 6 and 12 months after PDT respectively. Before treatment, cytology ≥ atypical squamous cells of undetermined significance (ASCUS) was 78.0 % (32/41). Negative conversion ratio of cytology was 75.0 % (24/32), 90.6 % (29/32) and 100.0 % (32/32) at 3, 6 and 12 months after PDT respectively. There were no serious adverse effects in patients during and after PDT.

CONCLUSION

HiPorfin-PDT is a promising and organ-saving approach for cervical HSIL, which also eradicates HPV infection effectively and can be a beacon of hope for the young women with fertility preservation requirement.

Recent advances in light-triggered cancer immunotherapy

Light-triggered phototherapies, such as photodynamic therapy (PDT) and photothermal therapy (PTT), have shown strong therapeutic efficacy with minimal invasiveness and systemic toxicity, offering opportunities for tumor-specific therapies. Phototherapies not only induce direct tumor cell killing, but also trigger anti-tumor immune responses by releasing various immune-stimulating factors. In recent years, conventional phototherapies have been combined with cancer immunotherapy as synergistic therapeutic modalities to eradicate cancer by exploiting the innate and adaptive immunity. These combined photoimmunotherapies have demonstrated excellent therapeutic efficacy in preventing tumor recurrence and metastasis compared to phototherapy alone. This review covers recent advancements in combined photoimmunotherapy, including photoimmunotherapy (PIT), PDT-combined immunotherapy, and PTT-combined immunotherapy, along with their underlying anti-tumor immune response mechanisms. In addition, the challenges and future research directions for light-triggered cancer immunotherapy are discussed.

Polysaccharide-Based Stimulus-Responsive Nanomedicines for Combination Cancer Immunotherapy

Cancer immunotherapy is a promising antitumor approach, whereas nontherapeutic side effects, tumor microenvironment (TME) intricacy, and low tumor immunogenicity limit its therapeutic efficacy. In recent years, combination immunotherapy with other therapies has been proven to considerably increase antitumor efficacy. However, achieving codelivery of the drugs to the tumor site remains a major challenge. Stimulus-responsive nanodelivery systems show controlled drug delivery and precise drug release. Polysaccharides, a family of potential biomaterials, are widely used in the development of stimulus-responsive nanomedicines due to their unique physicochemical properties, biocompatibility, and modifiability. Here, the antitumor activity of polysaccharides and several combined immunotherapy strategies (e.g., immunotherapy combined with chemotherapy, photodynamic therapy, or photothermal therapy) are summarized. More importantly, the recent progress of polysaccharide-based stimulus-responsive nanomedicines for combination cancer immunotherapy is discussed, with the focus on construction of nanomedicine, targeted delivery, drug release, and enhanced antitumor effects. Finally, the limitations and application prospects of this new field are discussed.

The safety and efficiency of photodynamic therapy for the treatment of osteosarcoma: A systematic review of in vitro experiment and animal model reports

BACKGROUND

Osteosarcoma (OS) is an aggressive malignant bone tumour with high mortality. A poor prognosis is noted in patients with distal metastases or multidrug resistance. As an emerging antitumor strategy, photodynamic therapy (PDT) mediated by visible and near infrared light has attracted intensive attention given its target selectivity, remote controllability, minimal or non-invasive features. However, PDT also has obvious limitations. Specifically, due to the limited penetration of light, it is mainly used in the clinical treatment of superficial malignant tumours, such as musculoskeletal sarcomas and melanoma, but it has not been applied to the clinical treatment of deep malignant bone tumours except for a very small number of experiments on deep canine OS models.

MATERIALS AND METHODS

We searched for studies that focused on the effectiveness and safety of PDT for OS based on in vitro experiments and animal models in the last decade. A systematic search was conducted using electronic databases, including PubMed, ClinicalTrials.gov, and the Cochrane Library.

INCLUSION CRITERIA

(1) original research articles about PDT for OS; (2) articles in English; (3) in vitro or animal model research; and (4) detailed information, including cell name, fluence, irradiation wavelength, time of incubation with PS, duration between PS treatment and irradiation, and duration between irradiation and viability assays.

EXCLUSION CRITERIA

(1) study was a review/systemic review article, patent, letter, or conference abstract/paper; (2) articles were not published in English; (3) studies containing overlapping or insufficient data.

RESULTS

We identified 201 publications, and 44 articles met the inclusion criteria and were included in the synthesis. Unfortunately, there are no relevant clinical reports of the use of PDT in the treatment of human OS. In these studies, 8 studies only employed in vivo experiments to evaluate the efficiency of PDT in an OS animal model, 19 studies exclusively performed in vitro viability assays of cells treated with PDT under different conditions, and 17 studies included in vitro cell experiments and in vivo animal OS models to evaluate the effect of PDT on OS in vivo and in vitro. All studies have shown that PDT is cytotoxic to OS cells or can inhibit the growth of OS in heterologous or homologous animal OS models but exhibits minimal cytotoxicity at a certain range of dosages.

CONCLUSION

Based on this systematic review, PDT can eradicate OS cells in cell culture and there is some evidence for efficacy in animal models. However, the ability for PDT to control human OS is unclear, the animal and human reports do not show evidence of human OS control, they just do show feasibility. The major issues concerning the potential for treatment of osteosarcoma with PDT are that adequate light should be transmitted to tumor loci and if the disease is caught before metastasis and irradiation of tumor sites is feasible, curative potential is there. Otherwise, PDT may be mainly palliative. To determine whether PDT can safely and efficiently be used in the clinical treatment of OS, many preclinical orthotopic animal OS models and OS models of multiple systemic metastases must be performed and interstitial PDT or intraoperative PDT may be a good and potential candidate for human OS treatment. If these problems can be well solved, PDT may be a potentially effective strategy for the treatment of OS patients.

Insight into the Prospects for Tumor Therapy Based on Photodynamic Immunotherapy

Malignancy is one of the common diseases with high mortality worldwide and the most important obstacle to improving the overall life expectancy of the population in the 21st century. Currently, single or combined treatments, including surgery, chemotherapy, and radiotherapy, are still the mainstream regimens for tumor treatment, but they all present significant side effects on normal tissues and organs, such as organ hypofunction, energy metabolism disorders, and various concurrent diseases. Based on this, theranostic measures for the highly selective killing of tumor cells have always been a hot area in cancer-related fields, among which photodynamic therapy (PDT) is expected to be an ideal candidate for practical clinical application due to its precise targeting and excellent safety performance, so-called PDT refers to a therapeutic method mainly composed of photosensitizers (PSs), laser light, and reactive oxygen species (ROS). Photoimmunotherapy (PIT), a combination of PDT and immunotherapy, can induce systemic antitumor immune responses and inhibit continuing growth and distant metastasis of residual tumor cells, demonstrating a promising application prospect. This article reviews the types of immune responses that occur in the host after PDT treatment, including innate and adaptive immunity. To further help PIT-related drugs improve their pharmacokinetic properties and bioavailability, we highlight the potential improvement of photodynamic immunotherapy from three aspects: immunostimulatory agents, tumor-associated antigens (TAAs) as well as different immune cells. Finally, we focus on recent advances in various strategies and shed light on their corresponding mechanisms of immune activation and possible clinical applications such as cancer vaccines. Having discovered the inherent potential of PDT and the mechanisms that PDT triggers host immune responses, a variety of immunotherapeutic strategies have been investigated in parallel with approaches to improve PDT efficiency. However, it remains to be further elucidated under what conditions the immune effect induced by PDT can achieve tumor immunosuppression and to what extent PDT-induced antitumor immunity will lead to complete tumor rejection. Currently, PIT presents several outstanding intractable challenges, such as the aggregation ability of PSs locally in tumors, deep tissue penetration ability of laser light, immune escape, and biological toxicity, and it is hoped that these issues raised will help to point out the direction of preclinical research on PIT and accelerate its transition to clinical practice.

Radiovaccination Strategy for Cancer Treatment Integrating Photodynamic Therapy-Generated Vaccines with Radiotherapy

Therapeutic cancer vaccines have become firmly established as a reliable and proficient form of tumor immunotherapy. They represent a promising approach for substantial advancements in the successful treatment of malignant diseases. One attractive vaccine strategy is using, as the vaccine material, the whole tumor cells treated ex vivo by rapid tumor ablation therapies that instigate stress signaling responses culminating in immunogenic cell death (ICD). One such treatment is photodynamic therapy (PDT). The underlying mechanisms and critical elements responsible for the potency of these vaccines are discussed in this review. Radiotherapy has emerged as a suitable component for the combined therapy protocols with the vaccines. Arguments and prospects for optimizing tumor control using a radiovaccination strategy involving X-ray irradiation plus PDT vaccines are presented, together with the findings supporting its validity.

Critical PDT theory II: Current concepts and indications

While photodynamic therapy (PDT) is effective for the eradication of select neoplasia and certain other pathologic conditions, it has yet to achieve wide acceptance in clinical medicine. A variety of factors contribute to this situation including relations with the pharmaceutical industry that have often been problematic. Some current studies relating to photodynamic effects are 'phenomenological', i.e., they describe phenomena that only reiterate what is already known. The net result has been a tendency of granting agencies to become disillusioned with support for PDT research. This report is intended to provide some thoughts on current research efforts that improve clinical relevance and those that do not.

Metallated phthalocyanines and their hydrophilic derivatives for multi-targeted oncological photodynamic therapy

BACKGROUND AND AIM

A photosensitizer (PS) delivery and comprehensive tumor targeting platform was developed that is centered on the photosensitization of key pharmacological targets in solid tumors (cancer cells, tumor vascular endothelium, and cellular and non-cellular components of the tumor microenvironment) before photodynamic therapy (PDT). Interstitially targeted liposomes (ITLs) encapsulating zinc phthalocyanine (ZnPC) and aluminum phthalocyanine (AlPC) were formulated for passive targeting of the tumor microenvironment. In previous work it was established that the PEGylated ITLs were taken up by cultured cholangiocarcinoma cells. The aim of this study was to verify previous results in cancer cells and to determine whether the ITLs can also be used to photosensitize cells in the tumor microenvironment and vasculature. Following positive results, rudimentary in vitro and in vivo experiments were performed with ZnPC-ITLs and AlPC-ITLs as well as their water-soluble tetrasulfonated derivatives (ZnPCS4 and AlPCS4) to assemble a research dossier and bring this platform closer to clinical transition.

METHODS

Flow cytometry and confocal microscopy were employed to determine ITL uptake and PS distribution in cholangiocarcinoma (SK-ChA-1) cells, endothelial cells (HUVECs), fibroblasts (NIH-3T3), and macrophages (RAW 264.7). Uptake of ITLs by endothelial cells was verified under flow conditions in a flow chamber. Dark toxicity and PDT efficacy were determined by cell viability assays, while the mode of cell death and cell cycle arrest were assayed by flow cytometry. In vivo systemic toxicity was assessed in zebrafish and chicken embryos, whereas skin phototoxicity was determined in BALB/c nude mice. A PDT efficacy pilot was conducted in BALB/c nude mice bearing human triple-negative breast cancer (MDA-MB-231) xenografts.

RESULTS

The key findings were that (1) photodynamically active PSs (i.e., all except ZnPCS4) were able to effectively photosensitize cancer cells and non-cancerous cells; (2) following PDT, photodynamically active PSs were highly toxic-to-potent as per anti-cancer compound classification; (3) the photodynamically active PSs did not elicit notable systemic toxicity in zebrafish and chicken embryos; (4) ITL-delivered ZnPC and ZnPCS4 were associated with skin phototoxicity, while the aluminum-containing PSs did not exert detectable skin phototoxicity; and (5) ITL-delivered ZnPC and AlPC were equally effective in their tumor-killing capacity in human tumor breast cancer xenografts and superior to other non-phthalocyanine PSs when appraised on a per mole administered dose basis.

CONCLUSIONS

AlPC(S4) are the safest and most effective PSs to integrate into the comprehensive tumor targeting and PS delivery platform. Pending further in vivo validation, these third-generation PSs may be used for multi-compartmental tumor photosensitization.

The Rationale for "Laser-Induced Thermal Therapy (LITT) and Intratumoral Cisplatin" Approach for Cancer Treatment

Cisplatin is one of the most widely used anticancer drugs in the treatment of various types of solid human cancers, as well as germ cell tumors, sarcomas, and lymphomas. Strong evidence from research has demonstrated higher efficacy of a combination of cisplatin and derivatives, together with hyperthermia and light, in overcoming drug resistance and improving tumoricidal efficacy. It is well known that the antioncogenic potential of CDDP is markedly enhanced by hyperthermia compared to drug treatment alone. However, more recently, accelerators of high energy particles, such as synchrotrons, have been used to produce powerful and monochromatizable radiation to induce an Auger electron cascade in cis-platinum molecules. This is the concept that makes photoactivation of cis-platinum theoretically possible. Both heat and light increase cisplatin anticancer activity via multiple mechanisms, generating DNA lesions by interacting with purine bases in DNA followed by activation of several signal transduction pathways which finally lead to apoptosis. For the past twenty-seven years, our group has developed infrared photo-thermal activation of cisplatin for cancer treatment from bench to bedside. The future development of photoactivatable prodrugs of platinum-based agents injected intratumorally will increase selectivity, lower toxicity and increase efficacy of this important class of antitumor drugs, particularly when treating tumors accessible to laser-based fiber-optic devices, as in head and neck cancer. In this article, the mechanistic rationale of combined intratumor injections of cisplatin and laser-induced thermal therapy (CDDP-LITT) and the clinical application of such minimally invasive treatment for cancer are reviewed.

Photodynamic Therapy: Critical PDT Theory

Photodynamic therapy can be useful for eradication of malignant cells at sites that are accessible to light delivery. There are few adverse effects, with many clinical reports indicating that PDT has curative potential. Patients with minimal disease, where success is more likely, are also sought by those promoting other protocols. New photosensitizing agents that initiate light-catalyzed reactions continue to be discovered. Reports describing advances in understanding fundamental aspects of photobiology are always of interest. But implications for treatment of neoplasia and other diseases are not always justified, especially when poorly-penetrating wavelengths of light are employed, often at very high light doses. Efficacy is sometimes estimated by protocols that may not accurately measure photokilling. Many reports claiming potential clinical relevance for in vitro observations are based on a limited understanding of the determinants of clinical efficacy. The future of photodynamic therapy depends on an appreciation of what can be accomplished, especially when used with other modalities, but will also depend on the goals and interests of granting agencies, pharmaceutical groups and clinical personnel. This commentary is intended to provide some thoughts on current research efforts, especially where clinical implications are suggested, hinted at or otherwise implied.

Recent advances in nanomedicines for photodynamic therapy (PDT)-driven cancer immunotherapy

Cancer immunotherapy has made tremendous clinical progress in advanced-stage malignancies. However, patients with various tumors exhibit a low response rate to immunotherapy because of a powerful immunosuppressive tumor microenvironment (TME) and insufficient immunogenicity of tumors. Photodynamic therapy (PDT) can not only directly kill tumor cells, but also elicit immunogenic cell death (ICD), providing antitumor immunity. Unfortunately, limitations from the inherent nature and complex TME significantly reduce the efficiency of PDT. Recently, smart nanomedicine-based strategies could subtly modulate the pharmacokinetics of therapeutic compounds and the TME to optimize both PDT and immunotherapy, resulting in an improved antitumor effect. Here, the emerging nanomedicines for PDT-driven cancer immunotherapy are reviewed, including hypoxia-reversed nanomedicines, nanosized metal-organic frameworks, and subcellular targeted nanoparticles (NPs). Moreover, we highlight the synergistic nanotherapeutics used to amplify immune responses combined with immunotherapy against tumors. Lastly, the challenges and future expectations in the field of PDT-driven cancer immunotherapy are discussed.

Symphony of nanomaterials and immunotherapy based on the cancer-immunity cycle

The immune system is involved in the initiation and progression of cancer. Research on cancer and immunity has contributed to the development of several clinically successful immunotherapies. These immunotherapies often act on a single step of the cancer–immunity cycle. In recent years, the discovery of new nanomaterials has dramatically expanded the functions and potential applications of nanomaterials. In addition to acting as drug-delivery platforms, some nanomaterials can induce the immunogenic cell death (ICD) of cancer cells or regulate the profile and strength of the immune response as immunomodulators. Based on their versatility, nanomaterials may serve as an integrated platform for multiple drugs or therapeutic strategies, simultaneously targeting several steps of the cancer–immunity cycle to enhance the outcome of anticancer immune response. To illustrate the critical roles of nanomaterials in cancer immunotherapies based on cancer–immunity cycle, this review will comprehensively describe the crosstalk between the immune system and cancer, and the current applications of nanomaterials, including drug carriers, ICD inducers, and immunomodulators. Moreover, this review will provide a detailed discussion of the knowledge regarding developing combinational cancer immunotherapies based on the cancer–immunity cycle, hoping to maximize the efficacy of these treatments assisted by nanomaterials.

CT radiomic features of photodynamic priming in clinical pancreatic adenocarcinoma treatment

Photodynamic therapy (PDT) offers localized focal ablation in unresectable pancreatic tumors while tissues surrounding the treatment volume experience a lower light dose, termed photodynamic priming (PDP). While PDP does not cause tissue damage, it has been demonstrated to promote vascular permeability, improve drug delivery, alleviate tumor cell density, and reduce desmoplasia and the resultant internal pressure in pre-clinical evaluation. Preclinical data supports PDP as a neoadjuvant therapy beneficial to subsequent chemotherapy or immunotherapy, yet it is challenging to quantify PDP effects in clinical treatment without additional imaging and testing. This study investigated the potential of radiomic analysis using CT scans acquired before and after PDT to identify areas experiencing PDT-induced necrosis as well as quantify PDP effects in the surrounding tissues. A total of 235 CT tumor slices from seven patients undergoing PDT for pancreatic tumors were examined. Radiomic features assessed included intensity metrics (CT number in Hounsfield Units) and texture analysis using several gray-level co-occurrence matrix (GLCM) parameters. Pre-treatment scans of tumor areas that resulted in PDT-induced necrosis showed statistically significant differences in intensity and texture-based features that could be used to predict the regions that did respond (paired t-test, response versus no response,p < 0.001). Evaluation of PDP effects on the surrounding tissues also demonstrated statistically significant differences, in tumor mean value, standard deviation, and GLCM parameters of contrast, dissimilarity and homogeneity (t-test, pre versus post,p < 0.001). Using leave-one-out cross validation, six intensity and texture-based features were combined into a support-vector machine model which demonstrated reliable prediction of treatment effects for six out of seven patients (ROC curve, AUC = 0.93). This study provides pilot evidence that texture features extracted from CT scans could be utilized as an effective clinical diagnostic prediction and assessment of PDT and PDP effects in pancreatic tumors. (clinical trial NCT03033225).

Investigation of the therapeutic effect of 5-aminolevulinic acid based photodynamic therapy on hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a heterogeneous type of cancer and current treatment options limit successful therapy outcomes. Photodynamic therapy (PDT) has attracted attention as an alternative approach in the treatment of different types of cancer. However, there is no study in the literature regarding the effect of PDT on HCC, in vitro. Therefore, the aim of this study was to determine the cytotoxic and apoptotic effects of 5-aminolevulinic acid (5-ALA)/PDT on two different HCC cell lines in terms of hepatitis B virus (HBV) infection. The therapeutic effects of 5-ALA-based PDT on HCC cell lines (Huh-7 and SNU-449) were evaluated by PpIX-fluorescence accumulation, WST-1 analysis, Annexin V analysis, and acridine orange/ethidium bromide staining after irradiation with different light doses through diode laser. The results showed that 1 mM 5-ALA displayed higher PpIX fluorescence in the SNU-449 cell line than the Huh-7 cell line after 4 h of incubation. After irradiation with different light doses (3, 6, 9, and 12 J/cm²), 5-ALA significantly reduced the proliferation of HCC cells and induced apoptotic cell death (p < 0.01). Furthermore, SNU-449 cells were more responsive to 5-ALA-based PDT than Huh-7 cells due to possibly its molecular features as well as viral HBV status. Our preliminary data obtained from this study may contribute to the development of 5-ALA/PDT-based treatment strategies in the treatment of HCC. However, this study could be improved by the elucidation of the molecular mechanisms of cell death induced by 5-ALA/PDT in HCC cells, the use of different photosensitizer, light sources, and in vivo experiments.

Photodynamic Therapy-Current Limitations and Novel Approaches

Photodynamic therapy (PDT) mostly relies on the generation of singlet oxygen, via the excitation of a photosensitizer, so that target tumor cells can be destroyed. PDT can be applied in the settings of several malignant diseases. In fact, the earliest preclinical applications date back to 1900’s. Dougherty reported the treatment of skin tumors by PDT in 1978. Several further studies around 1980 demonstrated the effectiveness of PDT. Thus, the technique has attracted the attention of numerous researchers since then. Hematoporphyrin derivative received the FDA approval as a clinical application of PDT in 1995. We have indeed witnessed a considerable progress in the field over the last century. Given the fact that PDT has a favorable adverse event profile and can enhance anti-tumor immune responses as well as demonstrating minimally invasive characteristics, it is disappointing that PDT is not broadly utilized in the clinical setting for the treatment of malignant and/or non-malignant diseases. Several issues still hinder the development of PDT, such as those related with light, tissue oxygenation and inherent properties of the photosensitizers. Various photosensitizers have been designed/synthesized in order to overcome the limitations. In this Review, we provide a general overview of the mechanisms of action in terms of PDT in cancer, including the effects on immune system and vasculature as well as mechanisms related with tumor cell destruction. We will also briefly mention the application of PDT for non-malignant diseases. The current limitations of PDT utilization in cancer will be reviewed, since identifying problems associated with design/synthesis of photosensitizers as well as application of light and tissue oxygenation might pave the way for more effective PDT approaches. Furthermore, novel promising approaches to improve outcome in PDT such as selectivity, bioengineering, subcellular/organelle targeting, etc. will also be discussed in detail, since the potential of pioneering and exceptional approaches that aim to overcome the limitations and reveal the full potential of PDT in terms of clinical translation are undoubtedly exciting. A better understanding of novel concepts in the field (e.g. enhanced, two-stage, fractional PDT) will most likely prove to be very useful for pursuing and improving effective PDT strategies.

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.

Application of photodynamic therapy in immune-related diseases

Photodynamic therapy (PDT) is a therapeutic modality that utilizes photodamage caused by photosensitizers and oxygen after exposure to a specific wavelength of light. Owing to its low toxicity, high selectivity, and minimally invasive properties, PDT has been widely applied to treat various malignant tumors, premalignant lesions, and infectious diseases. Moreover, there is growing evidence of its immunomodulatory effects and potential for the treatment of immune-related diseases. This review mainly focuses on the effect of PDT on immunity and its application in immune-related diseases.

Neoadjuvant vascular-targeted photodynamic therapy improves survival and reduces recurrence and progression in a mouse model of urothelial cancer

Locally advanced urothelial cancer has high recurrence and progression rates following surgical treatment. This highlights the need to develop neoadjuvant strategies that are both effective and well-tolerated. We hypothesized that neoadjuvant sub-ablative vascular-targeted photodynamic therapy (sbVTP), through its immunotherapeutic mechanism, would improve survival and reduce recurrence and progression in a murine model of urothelial cancer. After urothelial tumor implantation and 17 days before surgical resection, mice received neoadjuvant sbVTP (WST11; Tookad Soluble, Steba Biotech, France). Local and systemic response and survival served as measures of therapeutic efficacy, while immunohistochemistry and flow cytometry elucidated the immunotherapeutic mechanism. Data analysis included two-sided Kaplan-Meier, Mann-Whitney, and Fischer exact tests. Tumor volume was significantly smaller in sbVTP-treated animals than in controls (135 mm3 vs. 1222 mm3, P < 0.0001) on the day of surgery. Systemic progression was significantly lower in sbVTP-treated animals (l7% vs. 30%, P < 0.01). Both median progression-free survival and overall survival were significantly greater among animals that received sbVTP and surgery than among animals that received surgery alone (P < 0.05). Neoadjuvant-treated animals also demonstrated significantly lower local recurrence. Neoadjuvant sbVTP was associated with increased early antigen-presenting cells, and subsequent improvements in long-term memory and increases in effector and active T-cells in the spleen, lungs, and blood. In summary, neoadjuvant sbVTP delayed local and systemic progression, prolonged progression-free and overall survival, and reduced local recurrence, thereby demonstrating therapeutic efficacy through an immune-mediated response. These findings strongly support its evaluation in clinical trials.

Recent progress in development and applications of second near-infrared (NIR-II) nanoprobes

Optical probes for near-infrared (NIR) light have clear advantages over UV/VIS-based optical probes, such as their low levels of interfering auto-fluorescence and high tissue penetration. The second NIR (NIR-II) window (1000-1350 nm) offers better light penetration, lower background signal, higher safety limit, and higher maximum permitted exposure than the first NIR (NIR-I) window (650-950 nm). Therefore, NIR-II laser-based photoacoustic (PA) and fluorescence (FL) imaging can offer higher sensitivity and penetration depth than was previously available, and deeper lesions can be treated in vivo by photothermal therapy (PTT) and photodynamic therapy (PDT) with an NIR-II laser than with an NIR-I laser. Advances in creation of novel nanomaterials have increased options for improving light-induced bioimaging and treatment. Nanotechnology can provide advantages such as good disease targeting ability and relatively long circulation times to supplement the advantages of optical technologies. In this review, we present recent progress in development and applications of NIR-II light-based nanoplatforms for FL, PA, image-guided surgery, PDT, and PTT. We also discuss recent advances in smart NIR-II nanoprobes that can respond to stimuli in the tumor microenvironment and inflamed sites. Finally, we consider the challenges involved in using NIR-II nanomedicine for effective diagnosis and 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.

Nanomedicines modulating tumor immunosuppressive cells to enhance cancer immunotherapy

Cancer immunotherapy has veered the paradigm of cancer treatment. Despite recent advances in immunotherapy for improved antitumor efficacy, the complicated tumor microenvironment (TME) is highly immunosuppressive, yielding both astounding and unsatisfactory clinical successes. In this regard, clinical outcomes of currently available immunotherapy are confined to the varied immune systems owing in large part to the lack of understanding of the complexity and diversity of the immune context of the TME. Various advanced designs of nanomedicines could still not fully surmount the delivery barriers of the TME. The immunosuppressive TME may even dampen the efficacy of antitumor immunity. Recently, some nanotechnology-related strategies have been inaugurated to modulate the immunosuppressive cells within the tumor immune microenvironment (TIME) for robust immunotherapeutic responses. In this review, we will highlight the current understanding of the immunosuppressive TIME and identify disparate subclasses of TIME that possess an impact on immunotherapy, especially those unique classes associated with the immunosuppressive effect. The immunoregulatory cell types inside the immunosuppressive TIME will be delineated along with the existing and potential approaches for immunosuppressive cell modulation. After introducing the various strategies, we will ultimately outline both the novel therapeutic targets and the potential issues that affect the efficacy of TIME-based nanomedicines.

Modulation of aminolevulinic acid-based photoinactivation efficacy by iron in vitro is cell type dependent

Iron availability to cells may be modified in the tumour microenvironment, which may be involved in treatment response. Iron availability affects the conversion of protoporphyrin IX to heme, which likely determines the efficacy of aminolevulinic acid-based photodynamic therapy (ALA-based PDT). We compared photoinactivation efficacy in three oesophageal cell lines in culture media differing in iron content, DMEM and RPMI 1640, and in RPMI 1640 supplemented with iron to understand the importance of iron presence for ALA-based PDT outcome. ALA-based PDT was more efficacious in DMEM than in RPMI 1640 in all tested cell lines. Consistently, the highest protoporphyrin IX fluorescence signals, indicating the highest level of protoporphyrin IX production, were detected from cell colonies incubated in DMEM compared to those incubated in RPMI 1640 irrespective of iron presence. Components in the culture media other than iron ions are likely to be responsible for the observed differences in two culture media. Nevertheless, iron supplementation to RPMI 1640 showed that the presence of ferric ions in the concentration range 0-8 mg/l affected ALA-based PDT efficacy in a cell type-dependent manner. In poorly differentiated carcinoma cells, the increased efficacy of ALA-induced photoinactivation in the presence of 0.1 mg/l of supplemented iron was found. At the same iron concentration, the slightly different mitochondrial potential at no modifications of the iron labile pool was observed. The efficacy of ALA-based PDT in vitro depends on the choice of culture medium and the presence of iron ions in culture medium depending on intrinsic properties of cells.

NIR-Triggered Sequentially Responsive Nanocarriers Amplified Cascade Synergistic Effect of Chemo-Photodynamic Therapy with Inspired Antitumor Immunity

A desirable cancer therapeutic strategy is supposed to have effective ability to not only exert maximum anticancer ability but also inspire antitumor immunity for preventing tumor relapse and metastasis. During this research, multifunctional upconversion nanoparticles (UCNPs) coated by ROS-responsive micelles are prepared for tumor targeting and near-infrared (NIR)-triggered photodynamic therapy (PDT)-combined synergistic effect of chemotherapy. Moreover, both PDT and chemotherapy agents could activate antitumor immunity via inducing immunogenic cell death with CD8⁺ and CD4⁺ T cells infiltrating in tumors. Through the experiments, intravenous administration of multifunctional nanocarriers with noninvasive NIR irradiation destroys the orthotopic tumors and efficiently suppresses lung metastasis in a metastatic triple-negative breast cancer model by cascade-amplifying chemo-PDT and systemic antitumor immunity. In conclusion, this study provides prospective chemo-PDT with inspired antitumor immunity for metastatic cancer treatment.

Ablative therapies for hepatic and biliary tumors: endohepatology coming of age

Ablative therapies refer to minimally invasive procedures performed to destroy abnormal tissue that may arise with many conditions, and can be achieved clinically using chemical, thermal, and other techniques. In this review article, we explore the different ablative therapies used in the management of hepatic and biliary malignancies, namely hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), with a particular focus on radiofrequency ablation (RFA) and photodynamic therapy (PDT) techniques.

Photoimmunotherapy of Ovarian Cancer: A Unique Niche in the Management of Advanced Disease

Ovarian cancer (OvCa) is the leading cause of gynecological cancer-related deaths in the United States, with five-year survival rates of 15-20% for stage III cancers and 5% for stage IV cancers. The standard of care for advanced OvCa involves surgical debulking of disseminated disease in the peritoneum followed by chemotherapy. Despite advances in treatment efficacy, the prognosis for advanced stage OvCa patients remains poor and the emergence of chemoresistant disease localized to the peritoneum is the primary cause of death. Therefore, a complementary modality that is agnostic to typical chemo- and radio-resistance mechanisms is urgently needed. Photodynamic therapy (PDT), a photochemistry-based process, is an ideal complement to standard treatments for residual disease. The confinement of the disease in the peritoneal cavity makes it amenable for regionally localized treatment with PDT. PDT involves photochemical generation of cytotoxic reactive molecular species (RMS) by non-toxic photosensitizers (PSs) following exposure to non-harmful visible light, leading to localized cell death. However, due to the complex topology of sensitive organs in the peritoneum, diffuse intra-abdominal PDT induces dose-limiting toxicities due to non-selective accumulation of PSs in both healthy and diseased tissue. In an effort to achieve selective damage to tumorous nodules, targeted PS formulations have shown promise to make PDT a feasible treatment modality in this setting. This targeted strategy involves chemical conjugation of PSs to antibodies, referred to as photoimmunoconjugates (PICs), to target OvCa specific molecular markers leading to enhanced therapeutic outcomes while reducing off-target toxicity. In light of promising results of pilot clinical studies and recent preclinical advances, this review provides the rationale and methodologies for PIC-based PDT, or photo-immunotherapy (PIT), in the context of OvCa management.

First autopsy analysis of the efficacy of intra-operative additional photodynamic therapy for patients with glioblastoma

The study aim to demonstrate the therapeutic tissue depth of photodynamic therapy (PDT) using the photosensitizer talaporfin sodium and semiconductor laser for malignant glioma from an autopsy finding. Three patients diagnosed with glioblastoma by pre-operative imaging (1 newly diagnosed patient and 2 patients with recurrence) were treated with intra-operative additional PDT and adjuvant therapy such as post-operative radiotherapy or chemotherapy. All three patients died of brain stem dysfunction owing to cerebrospinal fluid dissemination or direct invasion of the tumor cells from 13, 18, or 20 months after PDT. Antemortem magnetic resonance images demonstrated no tumor recurrence in the site of PDT, and autopsy was performed for the pathological analysis. Macroscopic observation demonstrated no tumor recurrence in two patients, but one patient demonstrated tumor recurrence in the therapeutic depth of PDT. Microscopic analysis demonstrated histopathological changes reaching depths of 9, 11, and 18 mm (mean: 12.7 mm) from the surface of the cavity of tumor resection, suggesting the therapeutic tissue depth of PDT to be in this range. This region demonstrated glial scarring with infiltration of T lymphocytes and macrophages, with slight degeneration of small vessel walls. However, viable tumor tissues were observed beyond or around the therapeutic tissue depth of PDT in two patients. PDT for glioblastoma prevented early local recurrence, which suggests the possibility that activation of the immune mechanisms was involved. The therapeutic tissue depth was suggested to be 9-18 mm from the surface of the cavity of tumor resection; however, the viable tumor tissues were demonstrated beyond this therapeutic range.

Investigation of copper-cysteamine nanoparticles as a new photosensitizer for anti-hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a primary malignancy of the liver and occurs predominantly in patients with underlying chronic liver disease and cirrhosis. HCC is now the third leading cause of cancer deaths worldwide, with over 500,000 people affected. However, there is no complete effective (ideal) treatment for liver cancer yet, and the new methods are expected to be discovered. Herein, for the first time, we report the anti-HCC effects of copper-cysteamine nanoparticles (Cu-Cy NPs), a new type of photosensitizers. An in vitro 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay shows that Cu-Cy NPs could significantly reduce the activity of HepG2 cells at a very low dose after a short time of ultraviolet radiation. In addition, we found that cell death was induced by Cu-Cy NPs, which is associated with cellular apoptosis. This implied that apoptosis might be the main mechanism of the Cu-Cy's anti-HCC activity. Furthermore, we found that Cu-Cy NPs obviously inhibited the tumor growth in vivo. More interestingly, we found that the soluble Cu-Cy NPs were able to enter exosomes which were secreted by tumor cells, and exosomes could be used to deliver Cu-Cy NPs to target tumor cells. All these observations suggest that Cu-Cy NPs have a good potential for cancer treatment.

Photo-immune therapy with liposomally formulated phospholipid-conjugated indocyanine green induces specific antitumor responses with heat shock protein-70 expression in a glioblastoma model

Glioblastoma (GBM) is the most common malignant brain tumor, and infiltrates into the surrounding normal brain tissue. Induction of a tumor-specific immune response is one of the best methods to obtain tumor-specific cytotoxicity. Photodynamic therapy (PDT) is known to effectively induce an antitumor immune response. We have developed a clinically translatable nanoparticle, liposomally formulated phospholipid-conjugated indocyanine green (LP-iDOPE), applicable for PDT. This nanoparticle accumulates in tumor tissues by the enhanced permeability and retention effect, and releases heat and singlet oxygen to injure cancer cells when activated by near infrared (NIR) light. We assessed the effectiveness of the LP-iDOPE system in brain using the rat 9L glioblastoma model. Treatment with LP-iDOPE and NIR irradiation resulted in significant tumor growth suppression and prolongation of survival. Histopathological examination showed induction of both apoptosis and necrosis and accumulation of CD8+ T-cells and macrophages/microglia accompanied by marked expressions of heat shock protein-70 (HSP70), which was not induced by mild hyperthermia alone at 45° C or an interleukin-2-mediated immune reaction. Notably, the efficacy was lost in immunocompromised nude rats. These results collectively show that the novel nanoparticle LP-iDOPE in combination with NIR irradiation can efficiently induce a tumor-specific immune reaction for malignant gliomas possibly by inducing HSP70 expression which is known to activate antigen-presenting cells through toll-like receptor signaling.

Combination of photodynamic therapy (PDT) and anti-tumor immunity in cancer therapy

Photodynamic therapy (PDT) is performed using a photosensitizer and light of specific wavelength in the presence of oxygen to generate singlet oxygen and reactive oxygen species(ROS) in the cancer cells. The accumulated photosensitizers in target sites induce ROS generation upon light activation, then the generated cytotoxic reactive oxygen species lead to tumor cell death via apoptosis or necrosis, and damages the target sites which results tumor destruction. As a consequence, the PDT-mediated cell death is associated with anti-tumor immune response. In this paper, the effects of PDT and immune response on tumors are reviewed. Activation of an immune response regarding the innate and adaptive immune response, interaction with immune cells and tumor cells that associated with antitumor efficacy of PDT are also discussed.

Preparation of a chlorophyll derivative and investigation of its photodynamic activities against cholangiocarcinoma

Photodynamic therapy (PDT) is emerging as a promising method for the treatment of various cancer diseases. However, the clinical application of PDT is limited due to the lack of effective photosensitizers. In this study, a novel chlorophyll derivative, N,N-bis(2-carboxyethyl)pyropheophorbide a (BPPA), had been synthesized and characterized. BPPA had a characteristic long wavelength absorption peak at 669nm and a singlet oxygen quantum yield of 0.54. To investigate the photodynamic ability of BPPA against cholangiocarcinoma (CCA), cellular uptake, subcellular location and bio-distribution, in vitro and in vivo PDT efficacy of BPPA were studied. The results showed that BPPA could rapidly accumulate in QBC-939 cells and localize in the cytoplasm. BPPA- PDT was effective in reducing the cell viability in a drug dose- and light dose-dependent manner in vitro. In CCA xenograft nude mouse model, the concentration of BPPA in the plasma lowered rapidly, and the fluorescence signal peaked at 0.5h and 2h after injection in the skin and tumor, respectively. Significant quantities could be observed in the tumor. BPPA followed by irradiation could significantly inhibit growth of tumors, and histological examination revealed necrotic damage in PDT-treated tumors. These results suggested that BPPA could be a promising drug candidate for photodynamic therapy in cholangiocarcinoma.

Advanced smart-photosensitizers for more effective cancer treatment

Photodynamic therapy (PDT) based upon the use of light and photosensitizers (PSs) has been used as a novel treatment approach for a variety of tumors. It, however, has several major limitations in the clinic: poor water solubility, long-term phototoxicity, low tumor targeting efficacy, and limited light penetration. With advances in nanotechnology, materials science, and clinical interventional imaging procedures, various smart-PSs have been developed for improving their cancer-therapeutic efficacy while reducing the adverse effects. Here, we briefly review state-of-the-art smart-PSs and discuss the future directions of PDT technology.

WITHDRAWN: Treatment of cancer by low intensity laser radiation therapy

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). The Editorial Board of Progress in Biophysics and Molecular Biology retracts this paper due to an accusation of plagiarism. After careful review, the Editorial Board believes sufficient evidence exists to support this accusation. The author does not dispute the fact that: (i) The paper "Treatment of cancer by low intensity laser radiation therapy" -- which was submitted to Progress in Biophysics and Molecular Biology (PBMB) in June 2017, and which was accepted for publication (http://doi.org/10.1016/j.pbiomolbio.2017.11.002)-- has been published previously in near-identical form. (ii) The previous publication appeared in the June 2017 issue of Cancer Biology (http://doi.org/10.7537/marscbj070217.11). (iii) The author explains that this is an administrative mix-up with another paper published in Cancer Biology in September 2017 (http://doi.org/10.7537/marscbj070317.03). The article duplicates significant paragraphs from the other published article. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

ALA-Photodynamic treatment in Lichen sclerosus-clinical and immunological outcome focusing on the assesment of antinuclear antibodies

BACKGROUND

Lichen sclerosus (LS) is a difficult to treat, often relapsing disease with unknown background. Autoimmune diseases also coexist with LS. Over recent years photodynamic therapy (PDT) has been shown to be a noninvasive and successful therapeutic approach for the effective treatment of many conditions. However, the change of immune status of the patients based on ANA antibodies has not been yet reported. Our aim was to observe the clinical response followed by possible changes in autoimmune antibodies levels before and after PDT for LS.

MATERIAL AND METHODS

We enrolled 100 women with Lichen sclerosus with or without a concomitant autoimmune disease. All patients received 10 cycles of PDT (65 treated with DIOMED Light, 35 with PhotoDYN Light). We assessed autoimmune antibodies before and after PDT in addition to the clinical response evaluation.Two-year prospective controlled before-and-after study.

RESULTS

Following PDT, patients showed a significant attenuation in symptoms' intensity (itching, pruritus, vulvar discomfort). After therapy 41% of patients had partial response, 51% of patients had no symptoms and 8% had persistent or worsened symptoms. The most frequent autoimmune disease were thyroid disorders, followed by vitiligo and arthritis. 57% patients with an additional autoimmune disease before PDT had ANA antibodies. The mean level of ANA in this group diminished significantly after PDT treatment (261.74 IU/ml before vs. 123.20 IU/ml after treatment).

CONCLUSION

Based on our results, we assume that PDT may influence the immune status of patients with Lichen sclerosus.

Photodynamic Therapy in Gynecologic Malignancies: A Review of the Roswell Park Cancer Institute Experience

Photodynamic therapy (PDT) is a treatment modality used in the management of solid tumor malignancies that employs the use of a photosensitizing agent, a light source and oxygen in order to illicit a direct cytotoxic effect. Its use in gynecologic malignancies is somewhat novel and has been used for palliative and curative intent. At the Roswell Park Cancer Institute, the use of PDT in the management of gynecologic cancers began in the mid 1980s and since that time 35 patients have received PDT as a treatment for recurrent or metastatic cutaneous and vulvar, vaginal, anal, and cervical recurrences. In our experience, 85% patients with metastatic cutaneous lesions had a complete response. Twenty-seven percent of patients with metastatic vaginal, cervical or anal recurrences had a complete response to therapy with a median response time of 28 months. Side effects from the treatment included moderate to severe burning sensation, pain and edema at the treatment site requiring narcotic pain medication for symptom management in patients who underwent treatment to cutaneous lesions as well as lower genital tract recurrences. PDT should be considered an option in patients who are too frail to undergo the standard of care or decline the standard of care in lieu of a less invasive treatment modality.

In situ production of ROS in the skin by photodynamic therapy as a powerful tool in clinical dermatology

Photodynamic therapy (PDT) is a clinical modality of photochemotherapy based on the accumulation of a photosensitizer in target cells and subsequent irradiation of the tissue with light of adequate wavelength promoting reactive oxygen species (ROS) formation and cell death. PDT is used in several medical specialties as an organ-specific therapy for different entities. In this review we focus on the current dermatological procedure of PDT. In the most widely used PDT protocol in dermatology, ROS production occurs by accumulation of the endogenous photosensitizer protoporphyrin IX after treatment with the metabolic precursors 5-methylaminolevulinic acid (MAL) or 5-aminolevulinic acid (ALA). To date, current approved dermatological indications of PDT include actinic keratoses (AK), basal cell carcinoma (BCC) and in situ squamous cell carcinoma (SCC) also known as Bowen disease (BD). With regards to AKs, PDT can also treat the cancerization field carrying an oncogenic risk. In addition, an increasing number of pathologies, such as other skin cancers, infectious, inflammatory or pilosebaceous diseases are being considered as potentially treatable entities with PDT. Besides the known therapeutic properties of PDT, there is a modality used for skin rejuvenation and aesthetic purposes defined as photodynamic photorejuvenation. This technique enables the remodelling of collagen, which in turn prevents and treats photoaging stygmata. Finally we explore a new potential treatment field for PDT determined by the activation of follicular bulge stem cells caused by in situ ROS formation.

Photodynamic efficiency of a chlorophyll-a derivative in vitro and in vivo

This paper reports the antitumor activity of a chlorophyll-a derivative, 2-[1-hydroxyethyl]-2-devinylpyropheophorbide-a (HEPa). Photophysical characteristics of HEPa were measured. And its cytotoxicity, intracellular localization, biodistribution, efficiency of photodynamic therapy (PDT), histological analysis were investigated using human bile duct carcinoma cells (QBC-939) and QBC-939 tumor bearing BABL/c nude mice as animal model. The results showed that HEPa was localized mainly within the cytoplasmic region and partially in lysosome. Biodistribution of HEPa in QBC-939 tumor bearing BABL/c nude mice showed its fast rate of clearance and high tumor selectivity. In vitro, HEPa had low dark toxicity and high photoxicity against QBC-939 cells. The inhibition rate of QBC-939 tumor could increase up to 92.3%, and H&E staining confirmed that HEPa could cause serious damage to the tumor with light dose of 100J/cm(2), implying that HEPa has potential to be a new antitumor candidate for photodynamic therapy (PDT).

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.

Photodynamic therapy downregulates the function of regulatory T cells in patients with esophageal squamous cell carcinoma

Photodynamic therapy (PDT) by selective photosensitization of cancer cells and subsequent laser application results in local tumor necrosis. However, the effects of PDT on immune function, which may depend on the type of immune response, are controversial. We investigated the immunological changes induced by PDT and the effect of PDT on level and function of regulatory T cells (Treg) in patients with invasive esophageal squamous cell carcinoma (ESCC). We analyzed patient's blood samples before and after PDT. Blood CD4+CD25+CD127-FoxP3+ Treg levels were quantified by FACS, and Treg function was evaluated by coculture proliferation assays with T effector (Teff) cells. We found that PDT abrogated the suppressive capacity of peripheral Treg (Days 7 and 14, p = 0.016) but had no effect on Treg levels. The effect of PDT on Treg function at Day 7 was accompanied by slight but statistically significant increases in peripheral neutrophil granulocytes (p = 0.035) and monocytes (p = 0.013) and a statistically significant increase (approximately 18-fold) in serum IL-6 levels (p = 0.008). In conclusion, PDT abolished Treg function, possibly due to increased IL-6 levels in treated ESCC patients. This may be crucial for an improved therapeutic outcome.

T-cell mediated anti-tumor immunity after photodynamic therapy: why does it not always work and how can we improve it?

Photodynamic therapy (PDT) uses the combination of non-toxic photosensitizers and harmless light to generate reactive oxygen species that destroy tumors by a combination of direct tumor cell killing, vascular shutdown, and activation of the immune system. It has been shown in some animal models that mice that have been cured of cancer by PDT, may exhibit resistance to rechallenge. The cured mice can also possess tumor specific T-cells that recognize defined tumor antigens, destroy tumor cells in vitro, and can be adoptively transferred to protect naïve mice from cancer. However, these beneficial outcomes are the exception rather than the rule. The reasons for this lack of consistency lie in the ability of many tumors to suppress the host immune system and to actively evade immune attack. The presence of an appropriate tumor rejection antigen in the particular tumor cell line is a requisite for T-cell mediated immunity. Regulatory T-cells (CD25+, Foxp3+) are potent inhibitors of anti-tumor immunity, and their removal by low dose cyclophosphamide can potentiate the PDT-induced immune response. Treatments that stimulate dendritic cells (DC) such as CpG oligonucleotide can overcome tumor-induced DC dysfunction and improve PDT outcome. Epigenetic reversal agents can increase tumor expression of MHC class I and also simultaneously increase expression of tumor antigens. A few clinical reports have shown that anti-tumor immunity can be generated by PDT in patients, and it is hoped that these combination approaches may increase tumor cures in patients.

Antitumor activity of photodynamic therapy with a chlorin derivative in vitro and in vivo

Chlorin derivatives are promising photosensitive agents for photodynamic therapy (PDT) of tumors. The aim of the current study is to investigate the PDT therapeutic effects of a novel chlorin-based photosensitizer, meso-tetra[3-(N,N-diethyl)aminomethyl-4-methoxy]phenyl chlorin (TMPC) for gliomas in vitro and in vivo. Physicochemical characteristics of TMPC were recorded by ultraviolet visible spectrophotometer and fluorescence spectrometer. The rate of singlet oxygen generation of TMPC upon photo-excitation was detected by using 1,3-diphenylisobenzofuran (DPBF). The accumulation of TMPC in gliomas U87 MG cells was measured by fluorescence spectrometer. The efficiency of TMPC-PDT in vitro was analyzed by MTT assay and clonogenic assay. The biodistribution and clearance of TMPC were determined by fluorescence measuring. Human gliomas U87 MG tumor-bearing mice model was used to evaluate the antitumor effects of TMPC-PDT. TMPC shows a singlet oxygen generation rate of 0.05 and displays a characteristic long wavelength absorption peak at 653 nm (ε = 15,400). The accumulation of TMPC increased with the increase of incubation time. In vitro, PDT using TMPC and laser showed laser dose- and concentration-dependent cytotoxicity to U87 MG cells. In U87 MG tumor-bearing mice, TMPC-PDT significantly reduced the growth of the tumors. Both in vitro and in vivo, TMPC showed little dark toxicity. In vitro and in vivo studies, it found that TMPC has excellent antitumor activities. It suggests that TMPC is a potential photosensitizer of photodynamic therapy for cancer.