ABSTRACT
Objective:To prepare nanobody-based immunotoxin BI7D12-PE38KDEL targeting EGFR and to examine its cytotoxicity against EGFR positive tumor cells.Methods:By using molecular cloning strategy,prokaryotic expression construct of pET28a-BI7D12-PE38KDEL was generated which consisted of nanobody 7D12 targeting EGFR in the form of a divalent fused with PE38KDEL,a truncated form of pseudomonas exotoxin A via a flexible peptide(G4S)4,and then transformed into E.coli BL21(DE3).Protein expression was induced by adding IPTG,purified by Ni-affinity column chromatography,and verified by Western blot.The binding capacity of the resulted immunotoxin to EGFR-positive cells A549,HT29,MCF-7 and EGFR-negative cells CEM,Jurkat were determined by flow cytometry assay,and its cytotoxicity against the target cells was examined.Briefly,tumor cells were treated with different dosage of the immunotoxin,and the killing efficacy of BI7D12-PE38KDEL on these cells were assessed by WST-1 assay after 72 hours.Results:The SDS-PAGE and Western blot results showed the recombinant immunotoxin BI7D12-PE38KDEL was successfully prepared,and majority of them was expressed in soluble form.BI7D12-PE38KDEL could selectively bind to EGFR-positive cells of A549,HT29,and MCF-7.More importantly,the immunotoxin exhibited much more significant killing effect on these EGFR positive cells compared to the negative control group of CEM and Jurkat cells(P<0.01).Conclusion:In the current study,the nanobody-based immunotoxin BI7D12-PE38KDEL targeting EGFR was successfully prepared and exhibited a superior inhibition effect for the growth of EGFR-positive cells.