Bare fiber photodynamic therapy using porfimer sodium for esophageal disease

During Digestive Disease Week 2005 in Chicago, Illinois, our group of 10 gastrointestinal photodynamic therapists met to discuss variations in procedural technique and treatment protocols. An extensive review of the use of photodynamic therapy (PDT) for esophageal disease has recently been published elsewhere [Wolfsen HC. Present status of photodynamic therapy for high-grade dysplasia in Barrett's esophagus. J Clin Gastroenterol 2005;39(3):189–202]. This report, based mostly on clinical experience and common sense rather than evidence-based medicine, is a detailed discussion of pragmatic issues. In summary, our centers treat patients with Barrett's dysplasia, Barrett's or squamous cell carcinoma using the photosensitizer porfimer sodium (2 mg/kg total body weight) and bare fiber PDT (no fiber centering devices). Aggressive suppression of gastric acid is uniformly emphasized. The most common technique variables were the light energy source, light dosimetry and the amount of Barrett's mucosa treated during a course of PDT. Standardization of porfimer sodium PDT procedures and light dosimetry may enhance treatment outcomes.     

Theranostic Silver Chalcogenide Quantum Dots in Phototherapy

Nanoparticles entered the phototherapy arena as photosensitizers and as delivery vehicles of organic photosensitizers. Luminescent Ag-chalcogenide quantum dots trigger PTT at long wavelengths and offer image-guided phototherapy. These nanoparticles also effectively deliver organic photosensitizers such as 5-aminolevulinic acid (ALA) and/or drugs to the target, hence provide PDT/PTT, Chemo/PTT, or even Chemo/PDT/PTT combination for effective killing of tumor cells.Nanoparticles entered the phototherapy arena as photosensitizers and as delivery vehicles of organic photosensitizers. 4-Aminolevulinic acid is now an FDA-approved pro-drug for PDT suffering from low bioavailability. Small theranostic nanoparticles that are already under heavy investigation for drug delivery and tracking offer the opportunity to improve ALA-bioavailability and delivery to targets, such as the tumor mass.Ag₂S quantum dots are luminescent in the NIR and highly biocompatible, hence are excellent for delivering ALA and providing image-guided PDT. We have loaded Ag₂S with ALA and tagged it with Cetuximab for improved and selective PDT of EGFR(+) colorectal cancer cells under 420 nm and 630 nm irradiation [1]. This enabled improved PDT with a significantly low ALA dose: 0.17 mM ALA-1 min – 640 nm irradiation caused more than 80% death in SW480 cell line after a short incubation. Further toxicity was obtained with additional 5FU conjugation to these QDs and almost all cells were killed at and above 0.35 mM ALA/15 μg mL⁻¹ 5FU doses, which is dramatically lower than IC50 of each component. Ag₂S QDs were also discovered as photosensitizers for PTT [3,4] and a combination of image-guided PTT and chemotherapy potential was investigated in cancer cells, using folic acid tagged Ag₂S QDs loaded with methotrexate [2]. This approach provided selective and near complete killing of FR(+) HeLa cells compared to HT29 and A549 cells via necrosis/late apoptosis after 10 min irradiation at 808 nm. IC₅₀ of MTX was reduced from 10 to 0.21 μg/mL.Lastly, in vivo examples of chemo/PTT combinations for the treatment of breast cancer will be shown.     

Photodynamic therapy in the esophagus

Photodynamic therapy (PDT) involves in situ photo-activation of photosensitizers by light at appropriate wavelength, generating highly active singlet oxygen and free radicals. For esophageal mucosal dysplasia such as high-grade dysplasia or intramucosal cancer, curative endoluminal therapy including PDT is now a reality. We review the role of PDT in the esophagus for the past two decades. The light for PDT can be delivered endoluminally freehand by cylindrical diffusers, via inflatable balloon stabilizers or microlens fibers. Porfimer sodium (Photofrin^®) is the only approved photosensitizer for PDT in the esophagus in North America, Europe and Japan. In addition, 5-aminolaevulinic acid (ALA), m-tetra(hydroxyphenyl)chlorin (m-THPC) and benzoporphyrin derivative monoacid ring A (BPD-MA) are other photosensitizers are being evaluated. More randomized clinical trials with long term follow up data are needed to further establish the role of PDT and other endoluminal ablative therapies either on their own or in combination to demonstrate survival benefits, quality of life advantages and cost-effectiveness. Changes in light delivery, timing, dosimetry and new endoscopic devices are needed to possibly improve all aspects of effectiveness. PDT was used mainly for palliation of advanced obstructing cancer of the esophagus at the gastrointestinal junction. More recently, because of the rising detection of the high-grade dysplasia in Barrett’s esophagus, a curative role of PDT in being realized.     

Tumor ablation with photodynamic therapy: introduction to mechanism and clinical applications

Photodynamic therapy (PDT) has been used to treat cancer for more than 25 years. Although the focus has been primarily on surface or superficial lesions, there has been a rapid growth in its application to the treatment of deeper parenchymal malignancies. The photochemical reaction consists of a photosensitizer, which, when irradiated by light at a specific wavelength, generates a cytotoxic oxygen singlet. The end result is an efficient induction of cell death, primarily through apoptosis, microvascular damage, and an antitumor immune response. PDT is currently being used in the treatment of many cancers including lung cancer, head and neck cancers, liver metastases, cholangiocarcinoma, and prostate cancer. The growing body of evidence concerning its efficacy, the increasing use of imaging to guide PDT, and the innate minimally invasive characteristics of PDT suggest that it should become an important addition to the growing array of techniques in interventional oncology.     

In vivo and in vitro models for photodynamic therapy by using novel photosensitizers

Photodynamic therapy (PDT) is an effective treatment for both malignant and non-malignant diseases, and new photosensitizers / chromophores are studied by confocal imaging and biological techniques determining cell survival with/without light. During PDT the activated PS transfers energy to nearby oxygen molecules, generating singlet oxygen (¹O₂) resulting in oxidative stress (ROS), which further elicit cell death by necrosis and apoptosis. Protoporphyrin IX (PpIX), is an efficient and widely used PS for bladder superficial bladder cancer treatment; either endogenously produced in the cancer cells by e. g. aminolaevulinic acid (ALA) or exogenously added as e. g. hexyl-ALA. The effects in vitro and in vivo are present by using an orthotopic rat cancer model; also included pphotochemical internalization (PCI). This is a new strategy for local enhancement of various types of drug molecules by employing a photosensitising compound and illumination of a diseased area in the body. The possibility of using PCI to enhance effects of the cytotoxic drug bleomycin is investigated, together with photophysical determinations and outlines of a treatment for intravesical therapy of bladder cancer. In vitro experiments indicate that employment of PCI technology using the novel photosensitizer TPCS_2a® enhance cytotoxic effects of bleomycin in bladder cancer cells. Furthermore, experiments in an orthotopic in vivo bladder cancer model show effective reduction in both necrotic area and bladder weight after TPCS_2a based photodynamic therapy (PDT). The tumor selectivity and PDT effects may be sufficient to destroy tumors without damaging detrusor muscle layers. Our results present a possible new treatment strategy for non-muscle invasive bladder cancer, with intravesical instillation of photosensitizer and bleomycin followed by illumination through an optic fiber by using a catheter.     

Enhancing the efficiency of 5-aminolevulinic acid-mediated photodynamic therapy using 5-fluorouracil on human melanoma cells

Background5-Aminolevulinic acid-mediated photodynamic therapy (ALA–PDT) is an effective and noninvasive modality for treatment of several types of non-melanoma skin cancers. This in-vitro study attempted to know whether the killing effect of ALA–PDT on the human melanoma cells (Mel-Rm cell line) could be increased by the presence of 5-fluorouracil (5-FU).MethodsTo evaluate the effect of ALA–PDT in combination with 5-FU on viability of human melanoma Mel-Rm cells, the cells incubated with 5-ALA and 5-FU for 3 h in nontoxic concentrations, and subsequently illuminated with a 630 nm light-emitting diode array. The cells viability and cytotoxicity determined by mitochondrial activity and lactate dehydrogenase assays.ResultsCombination of ALA–PDT and 5-FU (FU–ALA–PDT) showed a considerable growth inhibition according to the results of MTT assay compared to ALA–PDT. The results of LDH assay also showed a cytotoxicity effect in ALA–PDT; however, the FU–ALA–PDT showed no significantly enhancement in cytotoxicity compared to ALA–PDT using LDH assay.ConclusionThe Mel-Rm cells incubation with 5-FU before PDT enhances the efficiency of 5-Aminolevulinic acid-mediated photodynamic therapy.     

Photodynamic therapy (PDT) of lung cancer: experience of the Tokyo Medical University

Endoscopic low (Photodynamic therapy (PDT)) or high (vaporization) power laser treatment has been recognized as a lung-sparing local therapeutic modality that can achieve remarkable responses. This paper reviews the experience of our institution since 1978 in the treatment of lung cancer using laser. Endoscopic ablation of tracheobronchial malignancies is mainly intended to reduce respiratory distress and improve quality of life. Effective results were obtained in 143 (81%) of the 177 lesions. PDT is extremely attractive and has been used for the various purposes. In the curative PDT for centrally located early stage lung cancer, complete response (CR) rate was achieved in 86.4% (165 out of 191 lesions). Overall 5-year survival rate was 57.6% and the lung cancer specific 5-year survival rate was 92.5%. With regard to palliative PDT to opening obstructed bronchi in advanced cases, more than 50% opening of the obstruction was accomplished in 75%. Preoperative PDT was performed in 32 patients with lung cancer for the purpose of either reducing the extent of resection or increasing operability. The initial purpose of PDT was achieved in 27 of 32 patients treated. Conversion to an operable condition was achieved in 4 of 5 originally inoperable cases. In 23 of 27 patients who were originally candidates for pneumonectomy, it became possible to reduce the extent of resection to lobectomy or sleeve lobectomy. PDT could be used to treat peripheral tiny lung cancers safely and without unacceptable effects on surrounding tissue. The authors believe that PDT has a great potential and will achieve further development in the future.     

Evaluation of collagen alteration after topical photodynamic therapy (PDT) using second harmonic generation (SHG) microscopy--in vivo study in a mouse model

Topical photodynamic therapy (PDT) mediated by 5-aminolevulinic acid (ALA) has been used for the treatment of age-related skin lesions for therapeutic or cosmetic purposes. The modulation of collagen component and structure might play a significant role in influencing treatment outcomes of PDT. In this study, the effect of multi-session low dose ALA PDT on skin rejuvenation was examined in a hairless mouse model. Changes in collagen and skin texture were investigated by histological examination and in vivo second harmonic generation (SHG) microscopy. Results indicated that multi-session PDT could improve the collagen density and arrangement of skin tissue. SHG microscopy combined with quantitative collagen analysis could provide a useful tool for the evaluation of collagen alteration induced by ALA PDT.     

Development of a Protocol for Whole-Lung In Vivo Lung Perfusion Assisted Photodynamic Therapy for the Treatment of Lung Metastases

Isolated lung metastases in sarcoma and colorectal cancer patients are inadequately treated with current standard therapies. In Vivo Lung Perfusion, a novel platform, could overcome limitations to photodynamic therapy treatment volumes by using low cellular perfusate, removing blood, and thus allowing greater light penetration. Development of personalized photodynamic therapy protocols requires in silico light propagation simulations based on optical properties and maximal permissible photodynamic threshold doses of lung tissue. This approach aims to maximize the effective treatment dose to the lung while avoiding toxicity to healthy lung tissue. Based on this rationale, the overall objective of this study is to create a whole-lung perfusion assisted PDT protocol. Specifically, we aimed to develop a light delivery system to deliver light homogenously to the entire lung and validate simulations of light distribution in the organ to guide personalized PDT dosimetry.Using a porcine model, animals underwent a modified lung flush procedure to remove blood from the organ. Our light delivery system comprised of multiple LED cylindrical panels emitting 660nm light were placed within the lung cavity, while isotropic detectors were placed within bronchoscopically within various lung segments via the airways. Local fluence rates were collected from fibers. A CT scan was performed using optical phantoms in place of sources, and an in silico model of the lung was generated based on segmentation of the scans (Figure 1). Light propagation in the lung was modelled using the FullMonte simulator inputting our previously determined optical properties at 660nm as parameters. Fluence rate attenuation curves were created from simulations of each experiment plotting the fluence rate over the relative distance from sources (Figure 2A). These curves were used to calculate the effective attenuation coefficient for each model based on our previously determined lung optical properties. Comparison of the irradiance and effective attenuation coefficients calculated from the model and direct measurements taken during experiments are shown in Figure 2B. Overall, there was strong reliability of our simulation thus validating the in silico model. This model will be used to guide personalized dosimetry of PDT treatments by informing the number, position, and intensity of light sources to achieve a desired fluence range within the lung parenchyma.     

Photodynamic therapy for primary tracheobronchial malignancy in Northwestern China

BackgroundPhotodynamic therapy (PDT) has been routinely performed to treat tracheobronchial malignancy. However, the experience in tracheobronchial adenoid cystic carcinoma (ACC) and peripheral lung cancer is still insufficient. This study aimed to share the experience of PDT for patients with primary tracheobronchial malignancy, especially the adenoid cystic carcinoma and peripheral lung cancer, and evaluated the efficacy and safety of PDT in Northwestern Chinese patients.MethodsThis study retrospectively analyzed the clinical data of 23 patients with primary tracheobronchial malignancy receiving PDT in our center. The short-term effect was evaluated by the objective tumor response and the clinical response. The long-term effect was estimated by recurrence-free survival (RFS).ResultsOf 23 patients, SR was achieved in 18 patients and MR in 3 patients. The clinical symptoms and the quality of life were significantly improved after PDT (P<0.05). And the mean RFS was 8.9 ± 1.9 months. SR for 6 cases of ACC were achieved with significant improvement of clinical symptoms and quality of life. No procedure-related complications appeared. And PDT was successfully performed for the peripheral lung cancer with the guidance of electromagnetic navigation bronchoscopy (ENB).ConclusionsThis study demonstrated that PDT achieved satisfactory efficacy and safety for Northwestern Chinese patients with primary tracheobronchial malignancy. Patients with ACC can benefit from PDT. And ENB-guided PDT is a novel and available option for the peripheral lung cancer. In short, this study accumulated valuable experience for the application of PDT in Chinese patients with primary tracheobronchial malignancy.     

Photodynamic therapy (PDT) - Initiation of apoptosis via activation of stress-activated p38 MAPK and JNK signal pathway in H460 cell lines

Aims

The purpose of this study was to investigate the photoefficacies of protoporphyrin IX (PpIX) generated by drug precursor 5-aminolevulinic acid (ALA) and its hexyl ester (H-ALA) on two human non-small lung carcinoma cell lines (H460/Bcl-2 and H460/neo).

Main methods

Drug uptake and the photoefficacies of PpIX were measured by flow cytometry and MTT assay; while the mode of cell death and alternation of signal transduction pathways were studied with 4′,6-diamidino-2-phenylindole (DAPI) staining and Western blot analysis, respectively.

Key findings

The flow cytometric analysis of H-ALA (5 μM) uptake revealed optimal fluorescent intensity at 8 h incubation, while ALA (0.5 mM) was still far from saturation. The LD₃₀ of H-ALA-PDT was 30 μM, 2 J/cm², while the LD₃₀ of ALA-PDT was 3 mM, 2 J/cm². The dark toxicities mediated by both pro-drug H-ALA and ALA were negligible. By DAPI staining, apoptotic cell death was observed. In addition, by Western blot analysis, H-ALA- and ALA-mediated PDT initiated apoptotic cell death via the up-regulation and activation of p38 mitogen activated protein kinase (MAPK), the stress-activated c-jun N-terminal kinases (JNK) and ERK.

Significance

These results suggested that H-ALA and ALA mediated PDT displayed similar photocytotoxicities towards the two non-small lung cancer cells. Our present study also demonstrates H-ALA or ALA mediated PDT in H460 cells are closely related to the activation of p38 MAPK and JNK signalling pathway.     

Successful treatment of refractory facial acne using repeat short-cycle ALA-PDT: Case study

Acne vulgaris is a common dermatological disorder. Topical photodynamic therapy (PDT)-mediated with aminolevulinic acid (ALA) or methyl aminolevulinic acid (MAL) has been successfully used in the treatment of moderate to severe acne. The purpose of this case report is to highlight the feasibility of using a repeat weekly short-cycle ALA-PDT to treat severe facial acne lesions refractory to systemic retinoid and antibiotics.     

Development of Functional Polymers Targeting Tumor-Associated Amino Acid Transporters for Photosensitizer Delivery

Photodynamic therapy (PDT) is a minimally invasive therapeutic modality that has been clinically approved for various cancer treatment [1]. To extend the potential of PDT to various types of cancers, it is important to develop new photosensitizers or drug delivery systems that can accumulate selectively within target tumors. Up to now, tremendous efforts have been devoted to the development of photosensitizers, some of which are already clinically used [2]. In addition to these efforts, recent studies have reported photosensitizers and drug delivery systems targeting specific molecules and environment in malignant tumors [3,4]. For example, we developed functional polymers possessing multiple cyclic RGD peptides in the side chains for photosensitizer delivery to target α_vβ₃ integrins, and this polymer-photosensitizer conjugate selectively accumulate within subcutaneous tumors in mice upon intravenous injection and accomplished appreciable PDT effects [4]. Such studies indicate that active targeting of tumor-associated molecules or environment should be a promising approach to achieve efficient PDT effects without giving unfavorable photochemical damage to normal tissues. In this context, we recently developed functional polymers targeting tumor-associated amino acid transporters [5]. The polymer had multiple amino acid moieties in the side chains and provided multivalent interaction with target amino acid transporters, exerting efficient tumor accumulation after systemic administration. In this study, based on this strategy, we fine-tuned the chemical structure of the polymers targeting tumor-associated amino acid transporters for PDT. In in vitro study, the fine-tuned polymer-photosensitizer conjugate exhibited strong phototoxicity without substantial dark toxicity to cultured cancer cells in an amino acid transporter-selective manner. Even in in vivo study, the polymer-photosensitizer conjugate demonstrated significantly enhanced PDT effect. Our polymers may be promising drug delivery systems for PDT.     

A quantitative study of in vivo protoporphyrin IX fluorescence build up during occlusive treatment phases

BackgroundTopical photodynamic therapy (PDT) is a non-invasive light based therapy used to treat non-melanoma skin cancer (NMSC) and dysplasia. During PDT, the light sensitive molecule protoporphyrin IX (PpIX) is activated, resulting in the production of singlet oxygen, which subsequently leads to cell death. PpIX is metabolised from a topically applied pro-drug and the strong fluorescence signal associated with PpIX can be utilised as an indicator of the amount of PpIX present within the tumour tissue. In this work we measure the build up PpIX during the occlusive treatment phase and investigate how the PpIX production rate is affected by different lesion and patient characteristics.MethodsFluorescence measurements were used to investigate the build up of PpIX within the tumour tissue during the 3 h long occlusive treatment prior to irradiation. The study included in vivo measurements of 38 lesions from 38 individual patients. Actinic keratosis (AK) and basal cell carcinoma (BCC) were the lesion types included in this study. The resulting data from the study was analysed using generalised linear mixed effects models.ResultsIt was found that the surface fluorescence signal linearly increased with occlusive treatment time. The predictive models suggest that there is a significant difference in PpIX production between lesion location, however no significant difference is demonstrated between different lesion types, gender and skin type.ConclusionsThe study extends and supports previous knowledge of PpIX production during the occlusive treatment phase.     

Photodynamic therapy in Argentina

The use of endogenous Protoporphyrin IX generated through the heme biosynthetic pathway after administration of 5-aminolevulinic acid (ALA) has led to many applications in photodynamic therapy (PDT). In Buenos Aires, Argentina, the Centro de Investigaciones sobre Porfirinas y Porfirias (CIPYP), reported for the first time, in 1975, porphyrin synthesis from ALA in highly dividing plant tissues. Increased porphyrin synthesis in tumours as well as cell photosensitisation was reported soon after. Our group is also interested in studying the use of new synthetic lipophilic derivatives of ALA as well as ALA delivery in liposomes. We have elucidated the mechanism of ALA transport in mammalian and yeast cells. The interactions between ALA-PDT and nitric oxide were investigated in three murine adenocarcinoma cell lines. In the National University of Río Cuarto, Córdoba, a group is devoted to the synthesis of new porphyrin-derived photosensitisers to study their effects on photoinactivation of bacterial and mammalian cells death by PDT. At the Centre of Electron Microscopy of the Cordoba National University, a prototype of a 630 nm noncoherent light source was designed and constructed. Cost of the light source and scarce knowledge of the benefits of PDT by physicians limit the spread of the treatment throughout the country.     

The use of a portable device for photodynamic therapy at home decreasing the patient's stay at hospital for small nodular basal cell carcinoma treatment

IntroductionSeveral studies have proved the efficacy of photodynamic therapy (PDT) for low-risk basal cell carcinoma (BCC). The standard PDT treatment consists of two sessions performed with one-week interval ¹. Although it is a well-tolerated treatment, the pain and the long stay at hospital area during PDT treatment must be improved. So, a new and portable PDT device was developed in order to offer part of PDT treatment at home.Material and MethodsAfter a clinical and dermoscopic diagnosis, 8 nodular BCC were submitted to this pilot study. The lesions were debulked and the material taken to histological confirmation of BCC. Then, a 20% methyl aminolevunate cream was applied and the area was covered for 3 hours. The first illumination was performed at the hospital, using a commercial LED device system emitting at 630 nm. The lesion was illuminated for 20 minutes with 125 mW/cm² totalizing 150J/cm² of fluence. Immediately after the first illumination, a light layer cream was applied and the new portable irradiation device was fixed using a medical adhesive tape. The patient was sent home and advised to turn on the illumination after 1.5 hours, and turn it off after 2 hours (totalizing a 312J/cm² of total fluence). Histological evaluation of the treated area was performed through a punch biopsy 30 days after treatment. The pain during PDT treatment was assessed every 3 minutes during the hospital session and self-reported every 20 minutes during home treatment on a numerical scale from 0 to 10. The median score values were compared between hospital and home treatments in 7 different moments using the T-Student test considering significant differences for a p-value <0,05. The patients were evaluated every 6 months through clinical and dermoscopy evaluation.ResultsThe lesions comprised 8 nodular BCC (mean diameter of 8,38mm) distributed in 6 females and 9 males patients. The median age was 58 years old. Six BCC were located on trunk, and 2 were located on upper limbs. According to histological analysis, the clearance at 30 days after PDT was 86,67%. The pain score was significantly lower for the PDT treatment performed at home (Table 1). All the patients completed 1 year of follow up and showed no recurrence.ConclusionUsing a portable irradiation prototype delivering lower irradiance was possible to offer a less painful and more comfortable treatment. In this pilot study, our protocol presented promising results with 86.6% of clearance. A randomized clinical trial has been started (registration number: 32048720.8.0000.5434) to confirm these promising results and establishing this new protocol.     

Clinical evaluation of a mobile,low-cost system for fluorescence guided photodynamic therapy of early oral cancer in India

Background: Morbidity and mortality due to oral cancer in India are exacerbated by a lack of access to effective treatments amongst medically underserved populations. We developed a user-friendly low-cost, portable fibre-coupled LED system for photodynamic therapy (PDT) of early oral lesions, using a smartphone fluorescence imaging device for treatment guidance, and 3D printed fibreoptic attachments for ergonomic intraoral light delivery.Methods: 30 patients with T₁N₀M₀ buccal mucosal cancer were recruited from the JN Medical College clinics, Aligarh, and rural screening camps. Tumour limits were defined by external ultrasound (US), white light photos and increased tumour fluorescence after oral administration of the photosensitising agent ALA (60 mg/kg, divided doses), monitored by a smartphone fluorescence imaging device. 100 J/cm² LED light (635 nm peak) was delivered followed by repeat fluorescence to assess photobleaching. US and biopsy were repeated after 7–17 days. This trial is registered with ClinicalTrials.gov, NCT03638622, and the study has been completed.Findings: There were no significant complications or discomfort. No sedation was required. No residual disease was detected in 22 out of 30 patients who completed the study (26 of 34 lesions, 76% complete tumour response, 50 weeks median follow-up) with up to 7.2 mm depth of necrosis. Treatment failures were attributed to large tumour size and/or inadequate light delivery (documented by limited photobleaching). Moderately differentiated lesions were more responsive than well-differentiated cancers.Interpretation: This simple and low-cost adaptation of fluorescenceguided PDT is effective for treatment of early-stage malignant oral lesions and may have implications in global health.     

Clinical photodynamic therapy of head and neck cancers—A review of applications and outcomes

As local control is tantamount to cure in head and neck cancer, an aggressive regimen of surgery and radiation remains the standard of care for most patients. Despite significant technical advances, these treatments are highly morbid. Further, patients who fail treatment have limited salvage options.Photodynamic therapy (PDT) and photodiagnosis (PD) of head and neck cancer offer significant potential for improved outcomes in a myriad of clinical indications ranging from in situ to recurrent disease. However, despite promising results, these modalities remain at the fringe of head and neck treatment options.Photofrin^®, Photosan and Foscan^® are photosensitizers used clinically in head and neck PD/PDT. In addition, aminolevulinic acid (ALA), which gives origin to Protoporphyrin IX, an endogeneous photosensitizer, is also used for PD/PDT. We review the clinical literature on these photosensitizers to assist in the integration of these important modalities into the mainstream of head and neck oncological therapy.     

Chlorin e6 mediated photodynamic therapy triggers resistance through ATM-related DNA damage response in lung cancer cells

ObjectivePhotodynamic therapy (PDT) is a promising strategy for the treatment of malignant tumors due to its high selectivity, limited-toxicity, and non-invasiveness. However, PDT can also induce DNA damage and subsequent repair response, which may reduce the efficacy of PDT. In the present study, we sought to explore the effect of chlorin e6 (Ce6)-mediated PDT on DNA damage and DNA damage response (DDR) in lung cancer cells. In addition, the effect of PDT combined with ATM inhibitor on molecules of DDR and the possibility of improving the efficacy of PDT were further investigated.Materials and methodsIn the in vitro study, lewis cells were submitted to Ce6 treatment (2, 4, 8, 16, 32 μg/mL). To determine the concentration of Ce6, uptake and toxicity of Ce6 mediated PDT were detected using flow cytometry (FACS), Confocal microscopy, and CCK-8. In the subsequent research, 8 μg/mL of Ce6 was the treatment condition for inducing PDT. The different post-irradiation placement times were further grouped under this condition (2, 4, 6, 12 h). Cellular reactive oxygen species (ROS), damage of DNA were measured by DCFH-DA probe, comet assay respectively. Then the expression of p-ATM, p53, and γ-H2A.X proteins related to DNA damage response, was detected by WB. The efficacy of Ce6 induced PDT was also demonstrated by Annexin-V/PI staining as well as the expression of PCNA, cleaved-caspase-3. On this basis, ATM inhibitor was applied to treat lewis cells combined with Ce6 (2, 4 h) to investigate whether the efficacy of PDT induced by Ce6 can be improved after the ATM-related DDR was blocked. The cell viability, apoptosis, and expression of associated proteins were assayed.ResultsAt 2–4 h after PDT treatment, ROS was dramatically elevated in lewis cells, DNA double-strand breaks (DDSB) occurred, as well as up-regulation of DDR proteins γ-H2A.X, p-ATM, and p53. At the same time, lewis cells did not undergo significant apoptosis. After ATM inhibition, the DDR was significantly blocked within 2–4 h after Ce6 induced PDT, along with a pronounced decrease in cell viability followed by a prominent increase of apoptosis.ConclusionCe6-mediated PDT generates ROS in a short period time, thus inducing DNA damage, ATM-related DDR as well as promoting resistance of lung cancer cells to PDT. Combining ATM inhibitor with PDT could effectively inhibit the DDR induced by PDT, thereby enhancing the efficacy. This study reveals a new resistance mechanism of PDT and proposes an intervention strategy.