Cloning, Expression and One-Step Purification of a Novel IP-10-(anti-HER2 scFv) Fusion Protein in Escherichia coli

Abstract

Breast cancer is the most common cancer in women, worldwide. The correlation between breast cancer malignancy and human epidermal growth factor 2 (HER2) expression leads to application of monoclonal antibodies against HER2 in HER2-overexpressing breast cancers. Variable fragments of light and heavy chains of monoclonal antibodies are linked in single chain variable fragment (scFv). Herein, IP-10 chemokine is conjugated to scFv against HER2 and thus CD8+T cells can chemoattract to HER2-overexpressing tumors. IP-10-(anti-HER2 scFv) gene was cloned in pET22-b (+) and successful expression of the fusion protein in E. coli host was confirmed by detecting a 39 kDa band in Western blotting. The highest fusion protein expression in Origami (DE3), BL21 (DE3) and SHuffle® were obtained 4 h after 0.1, 0.5 and 0.1 mM IPTG induction at 37, 37 and 30 °C, respectively. It was also demonstrated that the most solubility of the fusion protein is obtained at 25 °C in all the three examined strains. The highest soluble form of the fusion protein was expressed in SHuffle®. However, due to low amount of the fusion protein expressed in SHuffle®, we focused on its expression in Origami (DE3). Finally, purification of the fusion protein using Ni–NTA affinity chromatography under native, denaturing and hybrid conditions was investigated. Purification under hybrid condition caused the most purity of the fusion protein. This study opens up the avenue of exploring the use of IP-10-(anti-HER2 scFv) as a potential treatment for HER2-overexpresing tumors or as an adjuvant in combination with HER2-based vaccine.