Immune response after photodynamic therapy increases anti-cancer and anti-bacterial effects

Photodynamic therapy(PDT) is a clinically approved procedure for treatment of cancer and infections. PDT involves systemic or topical administration of a photosensitizer(PS), followed by irradiation of the diseased area with light of a wavelength corresponding to an absorbance band of the PS. In the presence of oxygen, a photochemical reaction is initiated, leading to the generation of reactive oxygen species and cell death. Besides causing direct cytotoxic effects on illuminated tumor cells, PDT is known to cause damage to the tumor vasculature and induce the release of pro-inflammatory molecules. Pre-clinical and clinical studies have demonstrated that PDT is capable of affecting both the innate and adaptive arms of the immune system. Immune stimulatory properties of PDT may increase its beneficial effects giving the therapy wider potential to become more extensively used in clinical practice. Be-sides stimulating tumor-specific cytotoxic T-cells capable to destroy distant untreated tumor cells, PDT leads to development of anti-tumor memory immunity that can potentially prevent the recurrence of cancer. The immunological effects of PDT make the therapy more effective also when used for treatment of bacterial infections, due to an augmented infiltration of neutrophils into the infected regions that seems to potentiate the outcome of the treatment.     

In vitro evaluation of the genotoxic and clastogenic potential of photodynamic therapy

Photodynamic therapy (PDT) was recently introduced in clinical practice for the management of cancer. As far as PDT relies on the combined action of a photosensitizer and a laser source, there is a need to evaluate the genotoxic and mutagenic potential of this treatment modality. This paper reports the effects of various photosensitizer and photo-irradiation doses on lethality to the MIA PaCa cell line using ZnPcS4 as the photosensitizer. The sister chromatid exchange (SCE) assay was used to evaluate the genotoxicity of various photosensitizer and photo-irradiation doses. Also, chromosomal aberrations at various time intervals post-irradiation were evaluated. The results showed that a combination of 3 J/cm2 irradiance with 5 microM ZnPcS4 concentration leads to the LD90 72 h post-irradiation. Eight days post-irradiation the LD90 level was achieved using a light dose of 3 J/cm2, independent of ZnPcS4 concentration. The SCE assay showed that cells treated with various light and drug doses presented no genotoxic potential, as SCE levels were not different from untreated (control) cells. Chromosomal analysis after PDT treatment at various time intervals post-irradiation showed that there was no significant chromosomal damage in cells treated photodynamically compared with untreated controls. The results show that the cell killing mechanism after PDT is not at the chromosome level, but may be at a different cellular level, such as plasma membranes, mitochondria, etc.     

Photodynamic therapy as a new treatment modality for inflammatory and infectious conditions

Photodynamic therapy (PDT) is currently used as a minimally invasive therapeutic modality for cancer. Whereas antitumor treatment regimens require lethal doses of photosensitizer and light, sublethal doses may have immunomodulatory effects, antibacterial action and/or regenerative properties. A growing body of evidence now indicates that non-lethal PDT doses can alleviate inflammation or treat established soft-tissue infections in various murine models of arthritis, experimental encephalomyelitis, inflammatory bowel disease and chronic skin ulcers. Furthermore, PDT is already used in clinical application and clinical trial for the treatment of psoriasis, chronic wounds and periodontitis in humans. Sublethal PDT should be regarded as a new viable option for the treatment of inflammatory conditions.     

Phototherapy and malignancy: possible enhancement by iron administration and hyperbaric oxygen

Photodynamic therapy (PDT) is a new therapeutic approach for the treatment of malignant tumors. Hyperbaric oxygen (HBO(2)) shows beneficial effects in various modalities of cancer interventions. Tumor cells tend to accumulate large amount of iron. There is interaction between tissue content of oxygen, iron, free radical production and tissue damage. Accumulation of intracellular iron is necessary for the production of oxygen radicals. HBO(2) increases tissue oxygen and hydrogen peroxide production in the cells. Malignant cells require iron, and exhibit more transferrin receptors. The photodynamic sensitization of human leukemic cells is achieved with accumulation of porphyrins stimulated by 5-aminolaevulanic acid (ALA) plus hemin. Further, a significant improvement in tumor response is obtained when PDT is delivered during hyperoxygenation. When PDT is combined with hyperoxygenation, the hypoxic condition is improved and the cell killing rate at various time points after PDT is significantly enhanced. Photosensitization with use of porphyrins is used with HBO(2) and PDT for treatment of certain tumors. PDT with ALA is used for treatment of actinic keratosis (AK). The combination of iron administration (by injection or oral rout), hemin, or transferrin, as a source for iron, HBO(2) as a source of oxygen under pressure and PDT as a source of generating free-radical tissue damage may be useful in the treatment of tumors. The possibility of combining HBO(2), iron, light and local photosensitizers to overcome skin tumors deserve extensive laboratory and clinical research work. Conclusively, iron, HBO(2), and PDT may have synergistic effect to hamper tumor cells.     

Biophysical aspects of photodynamic therapy.

Over the last three decades photodynamic therapy (PDT) has been developed to a useful clinical tool, a viable alternative in the treatment of cancer and other diseases. Several disciplines have contributed to this development: chemistry in the development of new photosensitizing agents, biology in the elucidation of cellular processes involved in PDT, pharmacology and physiology in identifying the mechanisms of distribution of photosensitizers in an organism, and, last but not least, physics in the development of better light sources, dosimetric concepts and construction of imaging devices, optical sensors and spectroscopic methods for determining sensitizer concentrations in different tissues. Physics and biophysics have also helped to focus on the role of pH for sensitizer accumulation, dose rate effects, oxygen depletion, temperature, and optical penetration of light of different wavelengths into various types of tissue. These are all important parameters for optimally effective PDT. The present review will give a brief, physically based, overview of PDT and then discuss some of the main biophysical aspects of this therapeutic modality.     

Recent developments in anticancer photochemotherapy]

The photodynamic therapy of cancer (PDT) by porphyrins is now at a turning point with the advent of phase III clinical trials. The transport of photofrin II and its delivery to tumor cells and vasculature is believed to be a determinant of tumor necrosis by suppressing the oxygen supply. However, this treatment must be improved by increasing the selectivity of the photosensitizer uptake by tumors and also by using photosensitizers absorbing in the 700-800 nm range where tissues have the highest transmittance. In addition, these new photosensitizers (chlorines, phthalocyanines...) should be rapidly excreted to avoid the only secondary effect of the PDT: the long-lasting photosensitivity of the patient skin. Finally, the combination of PDT with other therapies or its chemopotentiation by "bioreductive" drugs which interfere with the metabolism of hypoxic cells resulting from the PDT are potential means for improving the effectiveness of this new modality for cancer treatment.     

Perylenequinones in photodynamic therapy: cellular versus vascular response.

Photodynamic therapy (PDT) is a promising new modality in the treatment of cancers, which employs the interaction between a tumor-localizing photosensitizer and light of an appropriate wavelength to bring about molecular oxygen-induced cell death. We have investigated the efficacy of photosensitizers from the family perylenequinone, namely Hypericin, Hypocrellin A and B, in the treatment of cancer. These photosensitizers are known as potent second generation natural photosensitizers that have phototherapeutic advantages over the presently used porphyrins. We have studied the in vitro signaling mechanism involved in the photodynamic action following PDT in various human carcinoma cell lines. The difference of tumor cell death between two modes of action i.e., vascular- and cellular-mediated cell death, were evaluated in order to compare treatments that can efficaciously eradicate tumor in xenografts model. The antivascular effect of PDT was demonstrated in the chick chorioallantoic membrane (CAM) model. Tumor therapy based on targeting the vasculature of the tumor is indeed promising as demonstrated in the higher relative regression percentage of treated tumor compared to cellular targeted PDT. The favorable tumor response derived from short drug-light interval mediated PDT was primarily based on the differential uptake of the photosensitizer into tumor-associated vasculature as opposed to the cellular compartments of the tumor.     

Clinical Application of Photodynamic Therapy

Photodynamic therapy（PDT） is a new medical technology, the study on photodynamic therapy was in full swing in the past two decade. Scientists have made great progress in it. Photosensitizer,oxygen and light source play important role in photodynamic therapy. PDT is a light activated chemotherapy. A photon is adsorbed by a photosensitizer which moves the drug into an excited state. The excited drug can then pass its energy to oxygen to create a chemical radical called “singlet oxygen”. Singlet oxygen attacks cellular structures by oxidation. Such oxidative damage might be oxidation of cell membranes or proteins. When the accumulation of oxidative damage exceeds a threshold level,the cell begins to die. Photodynamic therapy allows selective treatment of localized cancer. PDT involves administration of a photosensitizer to the patients, followed by delivery of light to the cancerous region. The light activates the agent which kills the cancer cells. Without light,the agent is harmless. As a new therapy,photodynamic Therapy has great Advantage in treating cancers. 1. PDT avoids systemic treatment. The treatment occurs only where light is delivered, hence the patient does not undergo go needless systemic treatment when treating localized disease. Side-effects are avoided, from losing hair or suffering nausea to more serious complications. 2. PDT is selective. The photosensitizing agent will selectively accumulate in cancer cells and not in surrounding normal tissues. Hence ,there is selective targeting of the cancer and sparing of surrounding tissues. 3. when surgery is not possible. PDT kills cancer cells but does not damage collagenous tissue structures,and normal cells will repopulate these structures. Hence,if a patient has cancer in a structure that cannot be removed surgicaily（eg. ,the upper bronchi of the lung） ,PDT can still treat the site. 4. PDT is repeatable. Uniike radiation therapy,PDT can be used again and again. Hence,it offers a means of longterm management of cancer even if complete cure is not attainable.     

Concise review: cancer/testis antigens, stem cells, and cancer

In the multistep process of cancer development, the concept that cancer stem cells are derived from normal stem cells that have gradually accumulated various genetic and epigenetic defects is gaining strong evidence. A number of investigations have identified molecular markers that, under normal conditions, are responsible for stem cell homeostasis but are also expressed in tumor "stem cell-like" subpopulations. In this regard, it was recently reported that a group of tumor-specific antigens known as cancer/testis antigens (CTAs) are expressed in human MSCs. It has long been stated that in normal tissue these antigens are exclusively expressed in germ cell precursors; however, based on these results, we suggest that CTAs are expressed at earlier stages during embryogenesis. The tumor-restricted expression of CTAs has led to several immunotherapeutic trials targeting some of these proteins. The clinical implications that these trials may have on the normal stem cell pools, as well as the immunologic properties of these cells, is to date poorly studied and should be considered.     

光动力疗法治疗肿瘤的免疫机制研究进展

光动力疗法(photodynamic therapy,PDT)是治疗肿瘤的有效手段之一,PDT治疗可导致肿瘤细胞的死亡和凋亡,并损伤肿瘤相关血管.近年来,PDT的免疫机制越来越受到关注.肿瘤细胞的免疫逃逸是肿瘤发生发展的重要因素.PDT治疗肿瘤时,可通过免疫原性细胞死亡(immunogenic cell death,ICD)诱导肿瘤细胞表达损伤相关分子模式(damage associated molecular patterns,DAMPs),从而活化树突状细胞,诱导机体特异性抗肿瘤免疫.同时,PDT还可影响肿瘤微环境中的相关免疫细胞和因子,进而增强机体抗肿瘤反应.光动力治疗和其他免疫治疗联合应用亦能增强疗效.故光动力治疗的免疫机制研究将为肿瘤治疗提供可能的新思路.     

Haematoporphyrin Based Photodynamic Therapy Combined with Hyperthermia Provided Effective Therapeutic Vaccine Effect against Colon Cancer Growth in Mice

Photodynamic therapy (PDT) has become an attractive option used in tumor treatment via its direct tumoricidal activities or its immune-boosting activities. On the other hand, heat shock protein 70 has been found to be largely associated with the establishment of anti-tumor activities offered by hyperthermia treated tumor cells. In the present study, we found that injection of tumor-bearing mice with colon cancer cell line CT-26 treated with haematoporphyrin based photodynamic therapy (hematoporphyrin monomethyl ether based PDT, HMME-PDT) together with hyperthermia demonstrated the most effective therapeutic effects against tumor growth, followed by cells treated by hyperthermia alone. CT-26 cells treated only with HMME-PDT failed to provide any therapeutic effects, although significant cell death was induced by HMME-PDT. Compared to hyperthermia treatment, HMME-PDT induced more efficient surface localization of HSP70 on CT-26 cells which correlated with efficient activation of cytolytic CD8 T cells and with effective anti-tumor responses. Thus, our study demonstrated that the surface expression of HSP70 may play a more important role than the total expression or release of this molecule in the activation of immune responses. And our study offered a novel modified PDT approach to the treatment of tumor cells intrinsically low on HSP70 expression.     

The immunological consequences of photodynamic treatment of cancer,a literature review

In this review we discuss the effect of photodynamic treatment (PDT) of solid tumors on the immune response. The effect on both the innate and adapted immune response is discussed. We have summarized the evidence that PDT causes or enhances an anti-tumor response. PDT is a local treatment in which the treated tumor remains in situ while the immune system is only locally affected and still functional in contrast with e.g. after systemic chemotherapy. We conclude that PDT of cancer is a way of in situ vaccination to induce a systemic antitumor response. In general, immune cells are found in the tumor stroma, separated from tumor cells by extracellular matrix and basal membrane-like structures. We hypothesize that PDT destroys the structure of a tumor, thereby enabling direct interaction between immune cells and tumor cells resulting in the systemic anti-tumor immune response.     

Pulsed diode laser-based monitor for singlet molecular oxygen

Photodynamic therapy (PDT) is a promising cancer treatment. PDT uses the affinity of photosensitizers to be selectively retained in malignant tumors. When tumors, pretreated with the photosensitizer, are irradiated with visible light, a photochemical reaction occurs and tumor cells are destroyed. Oxygen molecules in the metastable singlet delta state O2(1Delta) are believed to be the species that destroys cancerous cells during PDT. Monitoring singlet oxygen produced by PDT may lead to more precise and effective PDT treatments. Our approach uses a pulsed diode laser-based monitor with optical fibers and a fast data acquisition system to monitor singlet oxygen during PDT. We present results of in vitro singlet oxygen detection in solutions and in a rat prostate cancer cell line as well as PDT mechanism modeling.     

新型卟啉类光敏药物介导的PDT对两种胃癌细胞HGC27和MGC803的杀伤效应

目的 观察本实验室自行合成的新型卟啉类光敏药物对2种人胃癌细胞HGC27和MGC803的光动力学治疗(PDT)作用及作用机制.方法 以人胃癌细胞HGC27和MGC803为实验细胞株.实验分为4组:空白对照组(无药物孵育、无光照),单纯光敏药物组(药物孵育、无光照),单纯光照组(无药物孵育、有光照),光敏药物+光照组(药...     

肺癌细胞株A549光动力学实验结果的定量分析

背景：目前光动力学癌症治疗的基础与临床研究均依赖于经验或定性模型,并缺乏准确有效的光学方法以监测及提高疗效。 目的：定量分析光动力数学模型在细胞试验中的应用结果,探讨光动力学疗法治疗计划系统的可能性。 方法：将人肺腺癌细胞株A549,3 W/633 nm半导体二极管激光器,血卟啉衍生物光敏剂Photosan3,采用底部澄清黑色96孔板进行常规细胞培养,严格避光状态下进行光敏剂处理及激光照射,设定标准曲线及对照组,计算不同光功率处理后的细胞残存率;数学模型基于时间域速率方程组方法建立。 结果与结论：光敏剂浓度为12 g/L、采用20,30,40,50 mW 4个光照功率、0~20 J/cm² 11个光照能量,组合而成4条细胞残存率曲线,显示激光功率相同情况下,随光照能量增加,细胞残存率下降,且相同能量下,激光功率越高,细胞残存率越高;通过数学模型模拟计算,设定入射光子量ρ为8.0×10⁵,光敏剂初始浓度[S₀]_i为4.0×10¹⁰,初始单态氧浓度[O₃]_i为5.9×10¹⁷,在此参数设定下,模拟的曲线与实际测得曲线最为相近,显示随着入射激光子量增加,细胞残存率逐渐增加,在相同入射光子量之下,细胞残存率随能量增加而下降的趋势。实验结果首次清楚地表明了定量描述光动力学疗法细胞模型的可行性,证实了光动力治疗数学模型与细胞试验的吻合性,表明此模型可以较准确反映细胞试验的结果。     

Gene Therapy Applications to Cancer Treatment

Over the past ten years significant advances have been made in the fields of gene therapy and tumour immunology, such that there now exists a considerable body of evidence validating the proof in the principle of gene therapy based cancer vaccines. While clinical benefit has so far been marginal, data from preclinical and early clinical trials of gene therapy combined with standard therapies are strongly suggestive of additional benefit. Manyreasons have been proposed to explain the paucity of clinical responses to single agent vaccination strategies including the poor antigenicity of tumour cells and the development of tolerance through down-regulation of MHC, costimulatory, signal transduction, and other molecules essential for the generation of strong immune responses. In addition, there is now evidence from animal models that the growing tumour may actively inhibit the host immune response. Removal of the primary tumour prior to T cell transfer from the spleen of cancer bearing animals, led to effective tumour cell line specific immunity in the recipient mouse suggesting that there is an ongoing tumour-host interaction. This model also illustrates the potential difficulties of clinical vaccine trials in patients with advanced stage disease.     

Development of dendritic-cell based prostate cancer vaccine

Available treatments for metastatic prostate cancer have failed to demonstrate significant curative potential. Current efforts are now directed towards developments of novel strategies for the treatment of metastatic prostate cancer. Cancer immunotherapeutic strategies utilize patient immune system components to kill cancer cells. This review discusses progress in active specific immunotherapeutic approaches as potential alternative methods in the treatment of metastatic prostate cancer. One of the newest advances in cancer immunotherapy is the use of dendritic cells as the vehicle to deliver cancer antigens for an effective in vivo T cell activation. The development of dendritic cell-based prostate cancer vaccine, as well as results of several clinical trials in prostate cancer involving the administration of peptide-pulsed autologous dendritic cell pulsed are discussed.     

Fluorescence diagnosis and photodynamic therapy in dermatology from experimental state to clinic standard methods.

The role of photodynamic therapy (PDT) in the treatment of in situ neoplasias and tumors of the skin is steadily increasing. An intratumoral enriched photosensitizer and its activation by light are the principles of photodynamic action. Aminolevulinic acid (ALA) has been shown to be the drug with most experimental and clinical use in the past. The highest efficacy with most selectivity in topical PDT is postulated for methyl aminolevulinate or methyl aminooxopenoat (MAL, MAOP, Metvix). For solar keratoses, topical PDT using MAL is already considered to be the treatment of choice. Epithelial skin tumors such as basal cell carcinomas also respond very well, however, a debulking procedure of the exophytic tumor tissue is an absolute prerequisite to a successful cure. In addition to functioning as a novel therapeutic tool, photodynamic sensitization of skin cancer cells is increasingly used for fluorescence diagnosis (FD) (also known as photodynamic diagnosis or PDD). The fluorescence of induced porphyrins is effective in detecting and delineating neoplastic skin areas. Future approaches of FD and PDT are nontumoral applications, especially psoriasis, viral-induced diseases, or acne vulgaris. Topical PDT is well tolerated and leads to excellent aesthetic results with only minor side effects.     

In Vitro Photodynamic Therapy with Chlorin e6 Leads to Apoptosis of Human Vascular Smooth Muscle Cells

Percutaneous coronary intervention has become the most common and widely implemented method of heart revascularization. However, the development of restenosis remains the major limitation of this method. Photodynamic therapy (PDT) recently emerged as a new and promising method for the prevention of arterial restenosis. Here the efficacy of chlorin e6 in PDT was investigated in vitro using human vascular smooth muscle cells (TG/HA-VSMCs) as one of the cell types crucial in the development of restenosis. PDT-induced cell death was studied on many levels, including annexin V staining, measurement of the generation reactive oxygen species (ROS) and caspase-3 activity, and assessment of changes in mitochondrial membrane potential and fragmentation of DNA. Photosensitization of TG/HA-VSMCs with a 170 μM of chlorin e6 and subsequent illumination with the light of a 672-nm diode laser (2 J/cm²) resulted in the generation of ROS, a decrease in cell membrane polarization, caspase-3 activation, as well as DNA fragmentation. Interestingly, the latter two apoptotic events could not be observed in photosensitized and illuminated NIH3T3 fibroblasts, suggesting different outcomes of the model of PDT in various types of cells. The results obtained with human VSMCs show that chlorin e6 may be useful in the PDT of aerial restenosis, but its efficacy still needs to be established in an animal model.