Chandler L A, Sosnowski B A, McDonald J R, Price J E, Aukerman S L, Baird A, Pierce G F, Houston L L
Selective Genetics, Inc., San Diego, CA 92121, USA.
Int J Cancer. 1998 Sep 25;78(1):106-11. doi: 10.1002/(sici)1097-0215(19980925)78:1<106::aid-ijc17>3.0.co;2-9.
Over-expression of the epidermal growth factor receptor (EGFR) is a hallmark of numerous solid tumors, thus providing a means of selectively targeting therapeutic agents. Heparin-binding epidermal growth factor (HBEGF) binds to EGFRs with high affinity and to heparan sulfate proteoglycans, resulting in increased mitogenic potential compared to other EGF family members. We have investigated the feasibility of using HBEGF to selectively deliver a cytotoxic protein into EGFR-expressing tumor cells. Recombinant fusion proteins consisting of mature human HBEGF fused to the plant ribosome-inactivating protein saporin (SAP) were expressed in Escherichia coli. Purified HBEGF-SAP chimeras inhibited protein synthesis in a cell-free assay and competed with EGF for binding to receptors on intact cells. A construct with a 22-amino-acid flexible linker (L22) between the HBEGF and SAP moieties exhibited an affinity for the EGFR that was comparable to that of HBEGF. The sensitivity to HBEGF-L22-SAP was determined for a variety of human tumor cell lines, including the 60 cell lines comprising the National Cancer Institute Anticancer Drug Screen. HBEGF-L22-SAP was cytotoxic in vitro to a variety of EGFR-bearing cell lines and inhibited growth of EGFR-over-expressing human breast carcinoma cells in vivo. In contrast, the fusion protein had no effect on small-cell lung carcinoma cells, which are EGFR-deficient. Our results demonstrate that fusion proteins composed of HBEGF and SAP exhibit targeting specificity and cytotoxicity that may be of therapeutic value in treating a variety of EGFR-bearing malignancies.
表皮生长因子受体（EGFR）的过度表达是众多实体瘤的一个标志，因此提供了一种选择性靶向治疗药物的方法。肝素结合表皮生长因子（HBEGF）以高亲和力与EGFR结合，并与硫酸乙酰肝素蛋白聚糖结合，与其他EGF家族成员相比，其促有丝分裂潜力增加。我们研究了使用HBEGF将细胞毒性蛋白选择性递送至表达EGFR的肿瘤细胞中的可行性。由成熟的人HBEGF与植物核糖体失活蛋白皂草素（SAP）融合而成的重组融合蛋白在大肠杆菌中表达。纯化的HBEGF-SAP嵌合体在无细胞试验中抑制蛋白质合成，并与EGF竞争结合完整细胞上的受体。在HBEGF和SAP部分之间具有22个氨基酸柔性接头（L22）的构建体对EGFR的亲和力与HBEGF相当。测定了包括组成美国国立癌症研究所抗癌药物筛选的60种细胞系在内的多种人类肿瘤细胞系对HBEGF-L22-SAP的敏感性。HBEGF-L22-SAP在体外对多种携带EGFR的细胞系具有细胞毒性，并在体内抑制过表达EGFR的人乳腺癌细胞的生长。相比之下，该融合蛋白对缺乏EGFR的小细胞肺癌细胞没有影响。我们的结果表明，由HBEGF和SAP组成的融合蛋白表现出靶向特异性和细胞毒性，这可能在治疗多种携带EGFR的恶性肿瘤中具有治疗价值。
