Protein Interactions Group, Frederick National Laboratory for Cancer Research, National Cancer Institute, NIH, Frederick, Maryland 21702, USA.
Mol Cancer Ther. 2012 Jul;11(7):1400-10. doi: 10.1158/1535-7163.MCT-12-0172. Epub 2012 May 2.
Soluble ligands are important targets for therapy of cancers and other diseases. Therapeutic monoclonal antibodies (mAb) against such ligands block their interactions with corresponding receptors but do not enhance their removal from the circulation and can increase their half-lives because of the long half-lives of the antibodies. We have hypothesized that mAbs targeting two or more nonoverlapping epitopes on the same ligand could form oligomeric antibody-ligand complexes that can bind to cells expressing Fc gamma receptors (FcγRs) with high avidity leading to their fast and irreversible removal from the circulation. Insulin-like growth factor II (IGF-II) is an example of such ligands and an important target for human cancer therapy. We identified two mAbs, m610.27 and m630.3, which bound to nonoverlapping epitopes on IGF-II with nanomolar affinity, and generated a bispecific antibody, m660. m660 inhibited the interaction of human IGF-II (hIGF-II) with the human breast cancer cell line MCF-7, hIGF-II-mediated IGF receptor type I and insulin receptor phosphorylation, and cell growth. In the presence of hIGF-II, large complexes of m660 were formed that bound to FcγRII-expressing BJAB cells much more efficiently than the monospecific antibody-hIGF-II complexes and were presumably phagocytosed by phorbol 12-myristate 13-acetate-stimulated macrophage-like U937 cells. A mixture of m610.27 and m630.3 exhibited similar properties. To our knowledge, these mAbs are the first reported to target nonoverlapping epitopes on a cancer-related ligand and could represent a novel class of candidate therapeutics against cancers. This approach could also be used to irreversibly eliminate other disease-related soluble ligands.
可溶性配体是癌症和其他疾病治疗的重要靶点。针对这些配体的治疗性单克隆抗体 (mAb) 可阻断其与相应受体的相互作用，但不能增强其从循环中的清除，并且由于抗体的半衰期长，其半衰期会延长。我们假设针对同一配体上两个或多个不重叠表位的 mAb 可以形成寡聚抗体-配体复合物，该复合物可以与表达 Fcγ 受体 (FcγR) 的细胞高亲和力结合，导致其快速和不可逆地从循环中清除。胰岛素样生长因子 II (IGF-II) 就是这样的配体之一，也是人类癌症治疗的重要靶点。我们鉴定了两种 mAb，m610.27 和 m630.3，它们以纳摩尔亲和力结合到 IGF-II 上的非重叠表位上，并生成了一种双特异性抗体 m660。m660 抑制了人 IGF-II (hIGF-II) 与人乳腺癌细胞系 MCF-7 的相互作用、hIGF-II 介导的 IGF 受体 I 和胰岛素受体磷酸化以及细胞生长。在 hIGF-II 的存在下，形成了 m660 的大复合物，与表达 FcγRII 的 BJAB 细胞结合的效率比单特异性抗体-hIGF-II 复合物高得多，并且可能被佛波醇 12-肉豆蔻酸 13-醋酸酯刺激的巨噬细胞样 U937 细胞吞噬。m610.27 和 m630.3 的混合物表现出类似的性质。据我们所知，这些 mAb 是首批报道针对癌症相关配体上不重叠表位的 mAb，可能代表一类针对癌症的新型候选治疗药物。这种方法也可用于不可逆地消除其他与疾病相关的可溶性配体。
