QOPNA, Department of Chemistry, University of Aveiro , 3810-193 Aveiro, Portugal.
Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra , 3000-548 Coimbra, Portugal.
Bioconjug Chem. 2018 Feb 21;29(2):306-315. doi: 10.1021/acs.bioconjchem.7b00636. Epub 2018 Jan 26.
The use of glycosylated compounds is actively pursued as a therapeutic strategy for cancer due to the overexpression of various types of sugar receptors and transporters on most cancer cells. Conjugation of saccharides to photosensitizers such as porphyrins provides a promising strategy to improve the selectivity and cell uptake of the photosensitizers, enhancing the overall photosensitizing efficacy. Most porphyrin-carbohydrate conjugates are linked via the carbon-1 position of the carbohydrate because this is the most synthetically accessible approach. Previous studies suggest that carbon-1 galactose derivatives show diminished binding since the hydroxyl group in the carbon-1 position of the sugar is a hydrogen bond acceptor in the galectin-1 sugar binding site. We therefore synthesized two isomeric porphyrin-galactose conjugates using click chemistry: one linked via the carbon-1 of the galactose and one linked via carbon-3. Free base and zinc analogs of both conjugates were synthesized. We assessed the uptake and photodynamic therapeutic (PDT) activity of the two conjugates in both monolayer and spheroidal cell cultures of four different cell lines. For both the monolayer and spheroid models, we observe that the uptake of both conjugates is proportional to the protein levels of galectin-1 and the uptake is suppressed after preincubation with an excess of thiogalactose, as measured by fluorescence spectroscopy. Compared to that of the carbon-1 conjugate, the uptake of the carbon-3 conjugate was greater in cell lines containing high expression levels of galectin-1. After photodynamic activation, MTT and lactate dehydrogenase assays demonstrated that the conjugates induce phototoxicity in both monolayers and spheroids of cancer cells.
由于大多数癌细胞过度表达各种类型的糖受体和转运蛋白，因此将糖基化合物用作癌症的治疗策略是一种积极的方法。将糖缀合到卟啉等光敏剂上提供了一种有前途的策略，可以提高光敏剂的选择性和细胞摄取率，从而增强整体光敏化效果。大多数卟啉-碳水化合物缀合物通过碳水化合物的碳-1 位连接，因为这是最具合成可及性的方法。以前的研究表明，碳-1 位半乳糖衍生物的结合能力降低，因为糖的碳-1 位上的羟基是半乳糖凝集素-1 糖结合位点中的氢键受体。因此，我们使用点击化学合成了两种异构的卟啉-半乳糖缀合物：一种通过半乳糖的碳-1 连接，另一种通过碳-3 连接。合成了这两种缀合物的自由碱基和锌类似物。我们评估了两种缀合物在四种不同细胞系的单层和球形细胞培养物中的摄取和光动力治疗（PDT）活性。对于单层和球体模型，我们观察到两种缀合物的摄取都与半乳糖凝集素-1 的蛋白水平成正比，并且通过荧光光谱法测量，摄取在与过量硫代半乳糖预孵育后被抑制。与碳-1 缀合物相比，在半乳糖凝集素-1 表达水平较高的细胞系中，碳-3 缀合物的摄取量更大。光动力激活后，MTT 和乳酸脱氢酶测定表明，该缀合物在单层和球体的癌细胞中均诱导光毒性。
