Understanding the Photodynamic Therapy Induced Bystander and Abscopal Effects: A Review

Abstract

Photodynamic therapy (PDT) is a clinically approved minimally/non-invasive treatment modality that has been used to treat various conditions, including cancer. The bystander and abscopal effects are two well-documented significant reactions involved in imparting long-term systemic effects in the field of radiobiology. The PDT-induced generation of reactive oxygen and nitrogen species and immune responses is majorly involved in eliciting the bystander and abscopal effects. However, the results in this regard are unsatisfactory and unpredictable due to several poorly elucidated underlying mechanisms and other factors such as the type of cancer being treated, the irradiation dose applied, the treatment regimen employed, and many others. Therefore, in this review, we attempted to summarize the current knowledge regarding the non-targeted effects of PDT. The review is based on research published in the Web of Science, PubMed, Wiley Online Library, and Google Scholar databases up to June 2023. We have highlighted the current challenges and prospects in relation to obtaining clinically relevant robust, reproducible, and long-lasting antitumor effects, which may offer a clinically viable treatment against tumor recurrence and metastasis. The effectiveness of both targeted and untargeted PDT responses and their outcomes in clinics could be improved with more research in this area.

In Vitro Antimicrobial Photodynamic Therapy for Pseudomonas aeruginosa (P. aeruginosa) and methicillin-resistant Staphylococcus aureus (MRSA) Inhibition Using a Green Light Source

“…For in vitro studies on cell culture plates, recent observations have indicated that non-irradiated wells, on occasion, exhibit similar responses to irradiated ones, particularly when in close proximity (continuous well) [ 37 , 38 , 39 ]. Nevertheless, this phenomenon was described in the 1970s when elucidating photoirradiation systems for PDT in studies on cancer cells [ 40 ].…”

Photodynamic Therapy for Eye, Ear, Laryngeal Area, and Nasal and Oral Cavity Diseases: A Review

“…Monitoring the long-term safety and outcomes of PDT is essential for ethical practice. Understanding the potential for delayed side effects or adverse events requires ongoing surveillance and reporting [214]. Clinicians have an ethical obligation to contribute to the body of knowledge regarding the safety profile of PDT, fostering transparency and accountability in the medical community.…”

Co-delivery of berberine and gold nanoparticles on liposomes for photodynamic therapy against 3D lung cancer cells

“…Photodynamic therapy (PDT) is a non-invasive treatment option for lung cancer that uses a photosensitizing agent and a specific wavelength of light to destroy cancer cells. 7,8 In PDT, reactive oxygen species (ROS) play a crucial role in the destruction of cancer cells. When photosensitizer (PS) agents are exposed to specific wavelengths of light, the PS becomes activated and transitions to a higher energy state.…”