Optimal composition and position of histidine-containing tags improves biodistribution of 99mTc-labeled DARPin G3.

Abstract

Radionuclide molecular imaging of HER2 expression in disseminated cancer enables stratification of patients for HER2-targeted therapies. DARPin G3, a small (14 kDa) engineered scaffold protein, is a promising probe for imaging of HER2. We hypothesized that position (C- or N-terminus) and composition (hexahistidine or (HE)3) of histidine-containing tags would influence the biodistribution of [99mTc]Tc(CO)3-labeled DARPin G3. To test the hypothesis, G3 variants containing tags at N-terminus (H6-G3 and (HE)3-G3) or at C-terminus (G3-H6 and G3-(HE)3) were labeled with [99mTc]Tc(CO)3. Labeling yield, label stability, specificity and affinity of the binding to HER2, biodistribution and tumor targeting properties of these variants were compared side-by-side. There was no substantial influence of position and composition of the tags on binding of [99mTc]Tc(CO)3-labeled variants to HER2. The specificity of HER2 targeting in vivo was confirmed. The tumor uptake in BALB/c nu/nu mice bearing SKOV3 xenografts was similar for all variants. On the opposite, there was a strong influence of the tags on uptake in normal tissues. The tumor-to-liver ratio for [99mTc]Tc(CO)3-(HE)3-G3 was three-fold higher compared to the hexahistidine-tag containing variants. Overall, [99mTc]Tc(CO)3-(HE)3-G3 variant provided the highest tumor-to-lung, tumor-to-liver, tumor-to-bone and tumor-to-muscle ratios, which should improve sensitivity of HER2 imaging in these common metastatic sites.

• Authors: Anzhelika Vorobyeva, Alexey Schulga, Elena Konovalova, Rezan Güler, John Löfblom, Mattias Sandström, Javad Garousi, Vladimir Chernov, Olga Bragina, Anna Orlova, Vladimir Tolmachev, Sergey M Deyev
• Journal: Scientific reports (Sci Rep) Vol. 9 Issue 1 Pg. 9405 (06 28 2019) ISSN: 2045-2322 [Electronic] England
• PMID: 31253840 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Recombinant Fusion Proteins
• polyhistidine
• Histidine
• Technetium
• Receptor, ErbB-2

Topics

• Animals
• Cell Line, Tumor
• Histidine (chemistry, genetics)
• Humans
• Mice
• Mice, Inbred BALB C
• Models, Molecular
• Protein Conformation
• Receptor, ErbB-2
• Recombinant Fusion Proteins (chemistry, genetics, pharmacokinetics)
• Structure-Activity Relationship
• Technetium (chemistry)
• Tissue Distribution
• Xenograft Model Antitumor Assays