Lutterbuese Ralf, Raum Tobias, Kischel Roman, Lutterbuese Petra, Schlereth Bernd, Schaller Evelyne, Mangold Susanne, Rau Doris, Meier Petra, Kiener Peter A, Mulgrew Kathy, Oberst Michael D, Hammond Scott A, Baeuerle Patrick A, Kufer Peter
Micromet AG, Staffelseestrasse 2, Munich, Germany.
J Immunother. 2009 May;32(4):341-52. doi: 10.1097/CJI.0b013e31819b7c70.
Carcinoembryonic antigen (CEA, CD66e) is a well-characterized tumor-associated antigen that is frequently overexpressed in tumors. Phospholipases release CEA from tumor cells resulting in high circulating serum levels of soluble CEA (sCEA) that has been validated as marker for progression of colorectal, breast, and lung cancers. sCEA also acts as a competitive inhibitor for anticancer strategies targeting membrane-bound CEA. As a novel therapeutic approach for treatment of tumors expressing CEA on their cell surface, we constructed a series of bispecific single-chain antibodies (bscAb) combining various single-chain variable fragments recognizing human CEA with a deimmunized single-chain variable fragments recognizing human CD3. CEA/CD3-bscAbs redirected human T cells to lyse CEA-expressing tumor cells in vitro and in vivo. Efficient tumor cell lysis was achieved in vitro at bscAb concentrations from 1 pg/mL (19 fM) to 8.9 pg/mL with preactivated CD8 T cells, and 200 to 500 pg/mL with unstimulated peripheral blood mononuclear cell. The cytotoxic activity of a subset of CEA/CD3-bscAbs was not competitively inhibited by sCEA at concentrations that exceeded levels found in the serum of most cancer patients. Treatment with CEA/CD3-bscAbs prevented the growth of human colorectal cancer lines in a severe combined immunodeficiency mouse model modified to show human T cell killing of tumors. A murine surrogate CEA/CD3-bscAb capable of recruiting murine T cells for redirected tumor lysis in immunocompetent mice prevented the growth of lung tumors expressing human CEA. Together, our results reveal a unique opportunity for targeting cytotoxic T cells toward CEA-expressing tumors without being competitively inhibited by sCEA and establish CEA/CD3-bscAb as a promising and potent therapeutic approach.
癌胚抗原（CEA，CD66e）是一种特征明确的肿瘤相关抗原，在肿瘤中经常过度表达。磷脂酶从肿瘤细胞中释放CEA，导致循环血清中可溶性CEA（sCEA）水平升高，sCEA已被确认为结直肠癌、乳腺癌和肺癌进展的标志物。sCEA还作为针对膜结合CEA的抗癌策略的竞争性抑制剂。作为治疗细胞表面表达CEA的肿瘤的一种新型治疗方法，我们构建了一系列双特异性单链抗体（bscAb），将识别人类CEA的各种单链可变片段与识别人类CD3的去免疫单链可变片段结合。CEA/CD3-bscAb在体外和体内将人类T细胞重定向以裂解表达CEA的肿瘤细胞。在体外，对于预激活的CD8 T细胞，bs cAb浓度为1 pg/mL（19 fM）至8.9 pg/mL时可实现有效的肿瘤细胞裂解，对于未刺激的外周血单核细胞，浓度为200至500 pg/mL时可实现有效裂解。在超过大多数癌症患者血清中发现的水平的浓度下，sCEA不会竞争性抑制一部分CEA/CD3-bscAb的细胞毒性活性。在经过修饰以显示人类T细胞对肿瘤的杀伤作用的严重联合免疫缺陷小鼠模型中，用CEA/CD3-bscAb治疗可阻止人类结直肠癌系的生长。一种能够募集鼠T细胞以在免疫活性小鼠中重定向肿瘤裂解的鼠替代CEA/CD3-bscAb可阻止表达人类CEA的肺肿瘤的生长。总之，我们的结果揭示了一个独特的机会，即靶向细胞毒性T细胞作用于表达CEA的肿瘤，而不受sCEA的竞争性抑制，并将CEA/CD3-bscAb确立为一种有前景的有效治疗方法。
