Immunotherapy has been successful in treating many tumour types. The development of additional tumour-antigen binding monoclonal antibodies (mAbs) will help expand the range of immunotherapeutic targets. Lewis histo-blood group and related glycans are overexpressed on many carcinomas, including those of the colon, lung, breast, prostate and ovary, and can therefore be selectively targeted by mAbs. Here we examine the molecular and structural basis for recognition of extended Lea and Lex containing glycans by a chimeric mAb. Both the murine (FG88.2) IgG3 and a chimeric (ch88.2) IgG1 mAb variants showed reactivity to colorectal cancer cells leading to significantly reduced cell viability. We determined the X-ray structure of the unliganded ch88.2 fragment antigen-binding (Fab) containing two Fabs in the unit cell. A combination of molecular docking, glycan grafting and molecular dynamics simulations predicts two distinct subsites for recognition of Lea and Lex trisaccharides. While light chain residues were exclusively used for Lea binding, recognition of Lex involved both light and heavy chain residues. An extended groove is predicted to accommodate the Lea–Lex hexasaccharide with adjoining subsites for each trisaccharide. The molecular and structural details of the ch88.2 mAb presented here provide insight into its cross-reactivity for various Lea and Lex containing glycans. Furthermore, the predicted interactions with extended epitopes likely explains the selectivity of this antibody for targeting Lewis-positive tumours.

中文翻译：

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靶向癌症的抗体识别Lewis聚糖的分子和结构基础。

免疫疗法已经成功地治疗了许多类型的肿瘤。其他肿瘤-抗原结合单克隆抗体（mAbs）的开发将有助于扩大免疫治疗靶标的范围。Lewis组织学血型和相关聚糖在许多癌中过表达，包括结肠癌，肺癌，乳腺癌，前列腺癌和卵巢癌，因此可以被mAb选择性靶向。在这里，我们研究了通过嵌合mAb识别扩展的Lea和Lex包含的聚糖的分子和结构基础。鼠类（FG88.2）IgG3和嵌合（ch88.2）IgG1 mAb变体均显示出与结肠直肠癌细胞的反应性，从而导致细胞活力大大降低。我们确定了在单位细胞中包含两个Fab的未配位ch88.2片段抗原结合（Fab）的X射线结构。分子对接的结合 聚糖接枝和分子动力学模拟预测了识别Lea和Lex三糖的两个不同的亚位点。虽然轻链残基专门用于Lea结合，但Lex的识别涉及轻链和重链残基。预计将延伸一个凹槽，以容纳Lea-Lex六糖以及每个三糖相邻的亚位点。此处展示的ch88.2 mAb的分子和结构细节为深入了解其与各种含Lea和Lex的聚糖的交叉反应性提供了信息。此外，与扩展表位的预测相互作用可能解释了该抗体对靶向Lewis阳性肿瘤的选择性。虽然轻链残基专门用于Lea结合，但Lex的识别涉及轻链和重链残基。预计将延伸一个凹槽，以容纳Lea-Lex六糖以及每个三糖的相邻亚位点。此处展示的ch88.2 mAb的分子和结构细节为深入了解其与各种含Lea和Lex的聚糖的交叉反应性提供了信息。此外，与扩展表位的预测相互作用可能解释了该抗体对靶向Lewis阳性肿瘤的选择性。虽然轻链残基专门用于Lea结合，但Lex的识别涉及轻链和重链残基。预计将延伸一个凹槽，以容纳Lea-Lex六糖以及每个三糖的相邻亚位点。此处展示的ch88.2 mAb的分子和结构细节为深入了解其与各种含Lea和Lex的聚糖的交叉反应性提供了信息。此外，与扩展表位的预测相互作用可能解释了该抗体对靶向Lewis阳性肿瘤的选择性。此处介绍的2 mAb可深入了解其与各种含Lea和Lex的聚糖的交叉反应性。此外，与扩展表位的预测相互作用可能解释了该抗体对靶向Lewis阳性肿瘤的选择性。此处介绍的2 mAb可深入了解其与各种含Lea和Lex的聚糖的交叉反应性。此外，与扩展表位的预测相互作用可能解释了该抗体对靶向Lewis阳性肿瘤的选择性。