Laser Research Centre, Faculty of Health Science, University of Johannesburg, Doornfontein 2028, South Africa.
Anticancer Agents Med Chem. 2021;21(2):123-136. doi: 10.2174/1871520620666200318101037.
Photodynamic Therapy (PDT) is a cancer therapy involving the systemic injection of a Photosensitizer (PS) that localizes to some extent in a tumor. After an appropriate time (ranging from minutes to days), the tumor is irradiated with red or near-infrared light either as a surface spot or by interstitial optical fibers. The PS is excited by the light to form a long-lived triplet state that can react with ambient oxygen to produce Reactive Oxygen Species (ROS) such as singlet oxygen and/or hydroxyl radicals, that kill tumor cells, destroy tumor blood vessels, and lead to tumor regression and necrosis. It has long been realized that in some cases, PDT can also stimulate the host immune system, leading to a systemic anti-tumor immune response that can also destroy distant metastases and guard against tumor recurrence. The present paper aims to cover some of the factors that can affect the likelihood and efficiency of this immune response. The structure of the PS, drug-light interval, rate of light delivery, mode of cancer cell death, expression of tumor-associated antigens, and combinations of PDT with various adjuvants all can play a role in stimulating the host immune system. Considering the recent revolution in tumor immunotherapy triggered by the success of checkpoint inhibitors, it appears that the time is ripe for PDT to be investigated in combination with other approaches in clinical scenarios.
光动力疗法（PDT）是一种癌症治疗方法，涉及系统性注射光敏剂（PS），该光敏剂在一定程度上定位于肿瘤。在适当的时间（从几分钟到几天不等）后，肿瘤会受到红色或近红外光的照射，无论是作为表面斑点还是通过间质光纤。PS 被光激发形成长寿命的三重态，可与周围氧气反应生成活性氧物种（ROS），如单线态氧和/或羟基自由基，从而杀死肿瘤细胞、破坏肿瘤血管，并导致肿瘤消退和坏死。长期以来，人们已经意识到，在某些情况下，PDT 还可以刺激宿主免疫系统，引发全身性抗肿瘤免疫反应，也可以破坏远处转移灶并防止肿瘤复发。本文旨在介绍一些可能影响这种免疫反应的可能性和效率的因素。PS 的结构、药物-光间隔、光传递率、癌细胞死亡方式、肿瘤相关抗原的表达以及 PDT 与各种佐剂的联合应用都可以在刺激宿主免疫系统方面发挥作用。考虑到近年来肿瘤免疫疗法因检查点抑制剂的成功而引发的革命，现在看来，PDT 与其他方法联合应用于临床场景的时机已经成熟。
