Affibody-based molecular probe 99mTc-(HE)3ZHER2:V2 for non-invasive HER2 detection in ovarian and breast cancer xenografts

Purpose- This study aimed to assess the biodistribution and bioactivity of the affibody molecular probe Tc-99m-(HE)(3)Z(HER2:V2), prepared by genetic recombination, and to investigate its potential for targeted human epidermal growth factor receptor 2 (HER2) imaging in SKOV3 ovarian cancer and MDA-MB-361 breast cancer xenografts. Methods- Affibody molecules were generated through genetic recombination. The radiochemical purity of the Tc-99m-labeled HER2 affibody was determined using reverse phase high performance liquid chromatography (RP-HPLC). Evaluation of HER2 affinity in SKOV3 ovarian cancer cells and MDA-MB-361 breast cancer cells (HER2-positive) was conducted by calculating equilibrium dissociation constants. Biodistribution of the Tc-99m-labeled affibody molecular probe was assessed in Balb/c mice bearing SKOV3 tumors. Tumor targeting specificity was evaluated in Balb/c mice using SKOV3, MDA-MB-361, and AT-3 (HER2-negative) xenografts. Results- Affibody (HE)(3)Z(HER2:V2), generated through recombinant gene expression, was successfully labeled with Tc-99m, achieving a radiochemical purity of (96.0 +/- 1.7)% (n = 3) as determined by RP-HPLC. This molecular probe exhibited specific binding to HER2-positive SKOV3 cells, demonstrating intense radioactive uptake. Biodistribution analysis showed rapid accumulation of Tc-99m-(HE)(3)Z(HER2:V2) in HER2-positive tumors post-administration, primarily clearing through the urinary system. Single-photon emission computed tomography imaging conducted 1-3 h after intravenous injection of Tc-99m-(HE)(3)Z(HER2:V2) into HER2-positive SKOV3 and MDA-MB-361 nude mouse models confirmed targeted uptake of the molecular probe by the tumors. Conclusions- The molecular probe Tc-99m-(HE)(3)Z(HER2:V2) developed in this study effectively targets HER2 for imaging HER2-positive SKOV3 and MDA-MB-361 xenografts in vivo. It exhibits rapid blood clearance without evident toxic effects, suggesting its potential as a valuable marker for detecting HER2 expression in tumor cells.