Maegawa Mari, Takeuchi Kenji, Funakoshi Eishi, Kawasaki Katsumi, Nishio Kazuto, Shimizu Nobuyoshi, Ito Fumiaki
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan.
Mol Cancer Res. 2007 Apr;5(4):393-401. doi: 10.1158/1541-7786.MCR-06-0303.
Antibodies are the most rapidly expanding class of human therapeutics, including their use in cancer therapy. Monoclonal antibodies (mAb) against epidermal growth factor (EGF) receptor (EGFR) generated for cancer therapy block the binding of ligand to various EGFR-expressing human cancer cell lines and abolish ligand-dependent cell proliferation. In this study, we show that our mAb against EGFRs, designated as B4G7, exhibited a growth-stimulatory effect on various human cancer cell lines including PC-14, a non-small cell lung cancer cell line; although EGF exerted no growth-stimulatory activity toward these cell lines. Tyrosine phosphorylation of EGFRs occurred after treatment of PC-14 cells with B4G7 mAb, and it was completely inhibited by AG1478, a specific inhibitor of EGFR tyrosine kinase. However, this inhibitor did not affect the B4G7-stimulated cell growth, indicating that the growth stimulation by B4G7 mAb seems to be independent of the activation of EGFR tyrosine kinase. Immunoprecipitation with anti-ErbB3 antibody revealed that B4G7, but not EGF, stimulated heterodimerization between ErbB2 and ErbB3. ErbB3 was tyrosine phosphorylated in the presence of B4G7 but not in the presence of EGF. Further, the phosphorylation and B4G7-induced increase in cell growth were inhibited by AG825, a specific inhibitor of ErbB2. These results show that the ErbB2/ErbB3 dimer functions to promote cell growth in B4G7-treated cells. Changes in receptor-receptor interactions between ErbB family members after inhibition of one of its members are of potential importance in optimizing current EGFR family-directed therapies for cancer.
抗体是人类治疗药物中发展最为迅速的一类，包括其在癌症治疗中的应用。用于癌症治疗的针对表皮生长因子（EGF）受体（EGFR）的单克隆抗体（mAb）可阻断配体与各种表达EGFR的人类癌细胞系的结合，并消除配体依赖性细胞增殖。在本研究中，我们表明，我们针对EGFRs的mAb，命名为B4G7，对包括PC-14（一种非小细胞肺癌细胞系）在内的各种人类癌细胞系表现出生长刺激作用；尽管EGF对这些细胞系没有生长刺激活性。用B4G7 mAb处理PC-14细胞后，EGFRs发生酪氨酸磷酸化，并且它被EGFR酪氨酸激酶的特异性抑制剂AG1478完全抑制。然而，这种抑制剂并不影响B4G7刺激的细胞生长，这表明B4G7 mAb的生长刺激似乎独立于EGFR酪氨酸激酶的激活。用抗ErbB3抗体进行免疫沉淀显示，B4G7而非EGF刺激了ErbB2和ErbB3之间的异二聚化。在存在B4G7的情况下，ErbB3发生酪氨酸磷酸化，而在存在EGF的情况下则没有。此外，ErbB2的特异性抑制剂AG825抑制了磷酸化以及B4G7诱导的细胞生长增加。这些结果表明，ErbB2/ErbB3二聚体在B4G7处理的细胞中发挥促进细胞生长的作用。抑制ErbB家族成员之一后，其成员之间受体 - 受体相互作用的变化对于优化当前针对癌症的EGFR家族导向疗法具有潜在重要性。
