Keler T, Graziano R F, Mandal A, Wallace P K, Fisher J, Guyre P M, Fanger M W, Deo Y M
Medarex, Inc., Annandale, New Jersey 08801, USA.
Cancer Res. 1997 Sep 15;57(18):4008-14.
A bispecific antibody, MDX-H210, was developed to target cytotoxic effector cells expressing Fc gamma receptor type I (Fc gammaRI, CD64) to HER2/neu-overexpressing tumor cells. HER2/neu is an appropriate target for immunotherapy due to the high level of expression of this proto-oncogene in a variety of malignancies. The expression of Fc gammaRI is limited primarily to cytotoxic immune cells, including monocytes, macrophages, and cytokine-activated polymorphonuclear (PMN) cells. Therefore, tumor cells bound with MDX-H210 can be selectively recognized by effector cells with cytotoxic potential. MDX-H210 was prepared by chemical conjugation of Fab' fragments derived from the HER2/neu-specific monoclonal antibody, 520C9, and the Fc gammaRI-specific monoclonal antibody, H22. This bispecific molecule demonstrated specific, dose-dependent, and saturable binding to both HER2/neu- and Fc gammaRI-expressing cells. A solid-phase immunoassay that demonstrated simultaneous and specific binding to both antigens was used to confirm the bispecific nature of MDX-H210. Monocytes and PMN cells mediated MDX-H210-dependent lysis of HER2/neu-overexpressing cell lines derived from breast, ovarian, and lung carcinomas. IFN-gamma treatment of monocytes enhanced antibody-dependent cellular cytotoxicity, whereas IFN-gamma and granulocyte colony-stimulating factor were required for PMN cell-mediated tumor cell lysis. In addition, MDX-H210 elicited tumor necrosis factor-alpha secretion from monocytes when cultured in the presence of HER2/neu-positive target cells. These in vitro data suggest that targeting tumor cells to Fc gammaRI with MDX-H210 may be an effective treatment for malignancies that overexpress HER2/neu. The in vivo cytotoxic potential of MDX-H210 may be enhanced by combination therapy with the cytokines granulocyte colony-stimulating factor and IFN-gamma, which up-regulate Fc gammaRI expression on cytotoxic effector cells.
一种双特异性抗体MDX-H210被研发出来，用于将表达I型Fcγ受体（FcγRI，CD64）的细胞毒性效应细胞靶向至过表达HER2/neu的肿瘤细胞。由于该原癌基因在多种恶性肿瘤中高表达，HER2/neu是免疫治疗的合适靶点。FcγRI的表达主要限于细胞毒性免疫细胞，包括单核细胞、巨噬细胞和细胞因子激活的多形核（PMN）细胞。因此，与MDX-H210结合的肿瘤细胞可被具有细胞毒性潜力的效应细胞选择性识别。MDX-H210是通过将源自HER2/neu特异性单克隆抗体520C9的Fab′片段与FcγRI特异性单克隆抗体H22进行化学偶联制备而成。这种双特异性分子对表达HER2/neu和FcγRI的细胞表现出特异性、剂量依赖性和饱和性结合。一种能同时特异性结合两种抗原固相免疫测定法被用于确认MDX-H210的双特异性性质。单核细胞和PMN细胞介导了MDX-H210依赖的对源自乳腺癌、卵巢癌和肺癌的过表达HER2/neu细胞系的裂解。用干扰素-γ处理单核细胞可增强抗体依赖的细胞毒性，而PMN细胞介导的肿瘤细胞裂解则需要干扰素-γ和粒细胞集落刺激因子。此外，当在HER2/neu阳性靶细胞存在的情况下培养时，MDX-H210可诱导单核细胞分泌肿瘤坏死因子-α。这些体外数据表明，用MDX-H210将肿瘤细胞靶向至FcγRI可能是过表达HER2/neu的恶性肿瘤的一种有效治疗方法。通过与粒细胞集落刺激因子和干扰素-γ联合治疗可增强MDX-H210的体内细胞毒性潜力，这两种细胞因子可上调细胞毒性效应细胞上FcγRI的表达。
