Chen Tao, Liu Xue, Hong Haifeng, Wei Henry
Department of Cell Biology and Institute of Biomedicine, National Engineering Research Center of Genetic Medicine, Guangdong Provincial Key Laboratory of Bioengineering Medicine, College of Life Science and Technology, Jinan University, Guangzhou, 510632, Guangdong, China.
J Transl Med. 2020 Oct 6;18(1):376. doi: 10.1186/s12967-020-02538-y.
Monoclonal antibodies (mAbs) have been used for cancer therapy. They are large and have some disadvantages limiting their use. Smaller antibody fragments are needed as their alternatives. A fully human single-domain antibody (sdAb) has a small size of only 15 kDa and consists of only the variable domain of the human antibody heavy chain (VH). It has no immunogenicity. It can easily penetrate into tumor tissues, target an epitope inaccessible to mAb and be manufactured in bacteria for a low cost. Epidermal growth factor receptor (EGFR) is over-expressed in many cancer cells and is a good target for cancer therapy.
The EGFR protein fragment located on the EGFR extracellular domain III was chosen to screen a human sdAb library. Five human anti-EGFR sdAbs were identified. Their specific binding to EGFR was confirmed by ELISA, Western blotting and flow cytometry. Their anti-tumor effects were tested.
Five novel fully human anti-EGFR sdAbs were isolated. They specifically bound to EGFR, not to the seven unrelated proteins as negative controls. They also bound to the three different human cancer cell lines, but not to the two cell lines as negative controls. They inhibited cell proliferation, migration and invasion and increased apoptosis of these three cancer cell lines. Two of them were tested for their anti-tumor effect in vivo and showed the anti-tumor activity in a mouse xenograft model for human lung cancer. Immunohistochemical staining of xenograft tumors also showed that their anti-tumor effects were associated with the inhibition of cancer cell proliferation and the promotion of cancer cell apoptosis.
This study clearly demonstrated that the anti-EGFR sdAbs could inhibit cancer cell growth in vitro and tumor growth in vivo. They could be potential therapeutics for the treatment of different human cancers.
单克隆抗体（mAb）已用于癌症治疗。它们体积较大，存在一些缺点限制了其应用。因此需要更小的抗体片段作为替代。完全人源单域抗体（sdAb）体积小，仅15 kDa，仅由人抗体重链可变域（VH）组成。它没有免疫原性。它能轻松穿透肿瘤组织，靶向mAb无法触及的表位，并且可以在细菌中低成本生产。表皮生长因子受体（EGFR）在许多癌细胞中过度表达，是癌症治疗的良好靶点。
选择位于EGFR胞外结构域III的EGFR蛋白片段筛选人源sdAb文库。鉴定出5种人抗EGFR sdAb。通过酶联免疫吸附测定（ELISA）、蛋白质印迹法和流式细胞术确认它们与EGFR的特异性结合。测试它们的抗肿瘤作用。
分离出5种新型完全人源抗EGFR sdAb。它们特异性结合EGFR，不与作为阴性对照的7种无关蛋白结合。它们也与3种不同的人癌细胞系结合，但不与作为阴性对照的2种细胞系结合。它们抑制这3种癌细胞系的细胞增殖、迁移和侵袭，并增加细胞凋亡。其中2种在体内测试了抗肿瘤作用，在人肺癌小鼠异种移植模型中显示出抗肿瘤活性。异种移植肿瘤的免疫组织化学染色也表明，它们的抗肿瘤作用与抑制癌细胞增殖和促进癌细胞凋亡有关。
本研究清楚地表明，抗EGFR sdAb可在体外抑制癌细胞生长，在体内抑制肿瘤生长。它们可能是治疗不同人类癌症的潜在疗法。
