AT1R-Specific Ligand Angiotensin II as a Novel SPECT Agent for Hepatocellular Carcinoma Diagnosis
Yuanbiao Tu, Zicun Liu, Fang Wang, Peifei Liu, Tao Ji, Changsheng Li, Zhihao Han, Zhaolun Li, Yi Ma, Yueqing Gu
Abstract
Hepatocellular carcinoma (HCC) is characterized by a high mortality and early diagnosis and treatment are critically needed. Ang II type 1 receptor (AT1R) has recently emerged as a potential molecular target for cancer diagnosis and intervention. Here, we labeled angiotensin II (Ang II), an AT1R ligand that is overexpressed in various solid cancers, with the near-infrared fluorescent dye, MPA, and radionuclide technetium-99m, and evaluated its capacity for HCC detection. These analyses were done in vitro using HepG2 (AT1R-positive) and BxPC3 (AT1R-negative) cell lines, and in vivo using a subcutaneous and orthotopic xenograft mouse model by fluorescence and SPECT imaging. Both Ang II-PEG4-MPA- and [99mTc]Tc-HYNIC-PEG4-Ang II-bound AT1R exhibited a high affinity in vitro and [99mTc]Tc-HYNIC-PEG4-Ang II displayed an acceptable level of in vitro stability in rat plasma and whole blood. In vivo imaging revealed excellent specific tumor-targeting in HepG2 mouse xenografts models. In vitro and in vivo competition experiments revealed specific Ang II-PEG4-MPA and [99mTc]Tc-HYNIC-PEG4-Ang II uptake by HepG2 cells and tumors. Altogether, AT1R-positive tumors were successfully detected via fluorescence and SPECT imaging using Ang II-PEG4-MPA and [99mTc]Tc-HYNIC-PEG4-Ang II, respectively. Given their superior targeting capacity, Ang II-PEG4-MPA and [99mTc]Tc-HYNIC-PEG4-Ang II are promising tools for HCC detection and warrant clinical translation.