Production and characterization of GPC3-N protein and its nanobody.

Glypican-3 (GPC3) has a promise to be the diagnostic biomarker as well as therapeutic target for hepatocellular carcinoma (HCC). Nanobody have the great potential in clinical diagnosis and treatment for their characteristics of small size, high solubility, stability, manipulability, binding advantages, and ease of production. In this study, the recombinant glypican-3-N terminal (GPC3-N) protein was expressed as inclusion body in E. coli BL21(DE3)pLysS cells and then purified, which is then used as the immunogen to construct nanobody phage library. The positive clone (named MF15) was obtained by four rounds of bio-panning, and then transformed into the E. coil TOP10F' cells to express nanobody protein, with the molecular weight of 19 kDa. Both Western blot and immunofluorescence analysis revealed that bacterially expressed GPC3-N protein is biologically active, and MF15 could specifically recognized native GPC3 expressed in HepG2 cells. The results in this study would provide the technical support for the development of diagnostic kits and antibody drugs targeting GPC3.