Immediate Protein Targets of Photodynamic Treatment in Carcinoma Cells

Oxidative stress induced in tumor cells undergoing photodynamic treatment (PDT) leads to extensive modification of many proteins in these cells. Protein oxidation mainly gives rise to formation of carbonyls and oxidized thiols. The immediate targets of PDT-induced protein oxidation in A431 tumor cells have been identified using a proteomic approach involving selective biotinylation, affinity purification and mass spectrometric identification of modified proteins. In all, 314 proteins were shown to undergo PDT-mediated oxidative modifications. While abundant structural proteins and chaperones represented a significant fraction of the carbonylated proteins, labeling of proteins containing oxidized thiols allowed identification of many proteins at low abundance and those involved in signaling and redox homeostasis. On the basis of the identification of these proteins, several likely mechanisms of PDT-induced triggering of apoptosis were put forward. This may not only lead to a further understanding of the complex network of cellular responses to oxidative stress, but it may also help in detailed targeting of photodynamic treatment applied to cancer.

接受光动力治疗（photodynamic treatment, PDT）的肿瘤细胞所诱导产生的氧化应激，会引发这些细胞内大量蛋白质发生广泛修饰。蛋白质氧化主要会导致羰基（carbonyls）与氧化型巯基（oxidized thiols）的形成。研究人员采用结合了选择性生物素标记（selective biotinylation）、亲和纯化（affinity purification）与修饰蛋白质质谱鉴定（mass spectrometric identification）的蛋白质组学方法，已鉴定出A431肿瘤细胞中PDT诱导的蛋白质氧化的直接作用靶点。总计有314种蛋白质被证实发生了PDT介导的氧化修饰。尽管丰度较高的结构蛋白与分子伴侣（chaperones）在羰基化修饰蛋白质中占比可观，但针对含氧化型巯基蛋白质的标记，使得研究人员能够鉴定出诸多低丰度蛋白质，以及参与信号转导与氧化还原稳态（redox homeostasis）的蛋白质。基于这些蛋白质的鉴定结果，研究者提出了数种PDT诱导细胞凋亡（apoptosis）的潜在机制。该研究不仅有助于进一步阐明细胞应对氧化应激的复杂调控网络，也可为癌症光动力治疗的精准靶向策略提供理论支撑。