Preclinical evaluation of ⁶⁸Ga-radiolabeled trimeric affibody for PDGFRβ-targeting PET imaging of hepatocellular carcinoma.

Abstract

Hepatocellular carcinoma (HCC) is a highly vascularized solid carcinoma and tumor vessel-targeted molecular imaging might be effective for early diagnosis of HCC. Herein, we developed a novel trimeric affibody (Z_TRI) with highly specific binding to the platelet-derived growth factor receptor beta (PDGFRβ). The aim of this study is to evaluate the feasibility of ⁶⁸Ga-radiolabeled Z_TRI ([⁶⁸Ga]Ga-DOTA-Z_TRI) as PET tracer for diagnosis of HCC. The bioinformatics analysis of clinical database and immunoblotting of clinical specimens were performed to validate the potential of PDGFRβ as HCC biomarker. The trimeric affibody Z_TRI was conjugated with DOTA-NHS-ester and radiolabeled with ⁶⁸Ga to produce [⁶⁸Ga]Ga-DOTA-Z_TRI conjugate. Immunoreactivity and specific uptake of [⁶⁸Ga]Ga-DOTA-Z_TRI were assessed by dose-dependent cell binding, autoradiography, and biodistribution analysis. [⁶⁸Ga]Ga-DOTA-Z_TRI PET/CT scanning of diethylnitrosamine (DEN)-induced primary HCC rats and a rare case of idiopathical HCC rhesus monkey was performed to evaluate the imaging capability and radiation dosimetry of [⁶⁸Ga]Ga-DOTA-Z_TRI in vivo. Excessive PDGFRβ was validated as a representative biomarker of HCC neovascularization. The radiolabeling of [⁶⁸Ga]Ga-DOTA-Z_TRI was achieved at more than 95% radiochemical yield. In vitro assays showed specific uptake of [⁶⁸Ga]Ga-DOTA-Z_TRI in HCC tumor vessels by autoradiography. Animal PET/CT imaging with [⁶⁸Ga]Ga-DOTA-Z_TRI successfully visualized the tumor lesions in primary HCC rats and rhesus monkey, and indicated radiation absorbed dose of 2.03E-02 mSv/MBq for each scanning. Our results demonstrated that [⁶⁸Ga]Ga-DOTA-Z_TRI conjugate could be applied as a promising PET tracer for early diagnosis of hepatocellular carcinoma.