Coupling Gd-DTPA with a bispecific,recombinant protein anti-EGFR-iRGD complex improves tumor targeting in MRI

Abstract

Recombinant anti-epidermal growth factor receptor-internalizing arginine-glycine- Aspartic acid (anti-EGFR single-domain antibody fused with iRGD peptide) protein efficiently targets the EGFR extracellular domain and integrin αvβ/β5,and shows a high penetration into cells. Thus,this protein may improve penetration of conjugated drugs into the deep zone of gastric cancer multicellular 3D spheroids. In the present study,a novel tumor- Targeting contrast agent for magnetic resonance imaging (MRI) was developed,by coupling gadolinium-diethylene triamine pentaacetate (Gd-DTPA) with the bispecific recombinant anti-EGFR-iRGD protein. The anti-EGFR-iRGD protein was extracted from Escherichia coli and Gd was loaded onto the recombinant protein by chelation using DTPA anhydride. Single- Targeting agent anti-EGFR-DTPA-Gd,which served as the control,was also prepared. The results of the present study showed that anti-EGFR-iRGD-DTPA-Gd exhibited no significant cytotoxicity to human gastric carcinoma cells (BGC-823) under the experimental conditions used. Compared with a conventional contrast agent (Magnevist),anti-EGFR-iRGD-DTPA-Gd showed higher T1 relaxivity (10.157/mM/sec at 3T) and better tumor- Targeting ability. In addition,the signal intensity and the area under curve for the enhanced signal time in tumor,in vivo,were stronger than Gd-DTPA alone or the anti-EGFR-Gd control. Thus,Gd-labelled anti-EGFR-iRGD has potential as a tumor- Targeting contrast agent for improved MRI.