FLUORESCENT TAGS TARGETED ON CELL SURFACE CARBOHYDRATES

癌变通常与细胞表面碳水化合物的改变有关。某些碳水化合物的表达或过度表达，如唾液酸化的Lewis X(SleX)、唾液酸化的Lewis a(Slea)、Lewis X(Lex)和Lewis Y(LeY)，与某些癌症的发生有关。这些细胞表面碳水化合物可用于肿瘤细胞的细胞特异性鉴定和靶向。该项目的长期目标是开发能够识别目标碳水化合物结构的小分子人工受体，具有高选择性和亲和力。这种受体可用于开发荧光标记，用于细胞特异性识别、组织特异性成像(如核磁共振)和靶向递送治疗剂。在本研究中，我们将使用SLeX作为模型碳水化合物，并以结肠癌作为模型生物系统，因为SLeX的表达通常与结肠癌的进展和转移有关。这一应用的短期目标是开发能够高亲和力和选择性识别SLeX的组织特异性荧光标记(传感器)。为了构建这样的荧光传感器，我们计划使用一种结合模板指导合成、组合化学和计算机分子建模辅助设计的综合方法。SLeX特异性人工受体具有用于细胞鉴定、检测和标记的潜力，用于定位、分期、组织活检和荧光定向手术切除结肠癌细胞。这种组织特异性化合物也可以作为靶向输送癌症化疗药物的载体。与基于抗体的检测/输送系统相比，这些小分子传感器还可能具有以下优势：(1)在储存和体内的稳定性更高；(2)通过生物膜的渗透性增加，从而增强了靶标可及性；(3)对结合的固有敏感性，随着荧光强度的显著增加，使得检测和可视化变得更容易，更适合高通量筛选，以及(4)更低的引发不良免疫反应的倾向。类似的方法，一旦开发出来，也可以用于构建与人类恶性肿瘤有关的其他细胞表面碳水化合物的荧光标记。

Malignant transformation is often associated with alteration of cell surface carbohydrates. The expression or over-expression of certain carbohydrates, such as sialyl Lewis X (sLex), sialyl Lewis a (sLea), Lewis X (Lex) and Lewis Y (Ley), has been correlated with the development of certain cancers. These cell surface carbohydrates can be used for cell-specific identification and targeting of carcinoma cells. The long-term goal of this project is the development of small molecule artificial receptors which can recognize target carbohydrate structures with high selectivity and affinity. Such receptors could be used for the development of fluorescent tags for cell- specific identification, tissue-specific imaging (such as MRI), and targeted delivery of therapeutic agents. In this study, we will use sLex as the model carbohydrate and use colon cancer as the model biological system because the expression of sLex is often associated with progression and metastasis of colon cancer. The short-term objective of this application is to develop tissue-specific fluorescent tags (sensors) which can recognize sLex with high affinity and selectivity. For the construction of such fluorescent sensors, we plan to use an integrated approach combining template-directed synthesis, combinatorial chemistry, and computer molecular modeling aided design. The sLex-specific artificial receptors have the potential to be used for cell identification, detection and tagging for the purpose of localization, staging, tissue biopsy, and fluorescence-directed surgical removal of colon cancer cells. Such tissue-specific compounds could also serve as vehicles for targeted delivery of cancer chemotherapeutic agents. These small molecule sensors may also have the following advantages over antibody-based detection/delivery systems: (1) greater stability during storage and in vivo; (2) increased permeability through biological membranes and, therefore, enhanced target accessibility; (3) intrinsic sensitivity to binding with significant fluorescence intensity increases, making detection and visualization easier and more suitable for high throughout screening, and (4) lower propensity to elicit undesirable immune responses. Similar methods, once developed, could also be used for the construction of fluorescent tags for other cell surface carbohydrates implicated in human malignancies.