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

Abstract

Purpose: 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.

Methods: 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.

Results: 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.

Conclusions: Our results demonstrated that [⁶⁸Ga]Ga-DOTA-Z_TRI conjugate could be applied as a promising PET tracer for early diagnosis of hepatocellular carcinoma.

Keywords: 68Ga; Affibody; Hepatocellular carcinoma; PDGFRβ; PET.