Hepatocellular Carcinoma Cells Carrying a Multimodality Reporter Gene for Fluorescence, Bioluminescence, and Magnetic Resonance Imaging In Vitro and In Vivo

Rationale and objectives: The study aimed to evaluate the feasibility of imaging or tracking hepatocellular carcinoma cells by modifying these cells to carry a multimodality reporter gene, enabling fluorescence, bioluminescence, and magnetic resonance imaging (MRI) in vitro and in vivo.

Materials and methods: HepG2 cells were labeled with the enhanced green fluorescent protein (EGFP)/luciferase2/ferritin-the multimodality reporter gene (labeled HepG2 cells). The labeled and unlabeled HepG2 cells were cultured in vitro and then injected subcutaneously into mice as a hepatoma model in vivo. The expressions of EGFP, luciferase2, and ferritin in HepG2 cell suspensions and hepatoma model were investigated using fluorescence, bioluminescence, and MRI.

Results: Individual HepG2 cells expressing EGFP were identified under blue laser excitation. The linear coefficient between the optical signal intensity of luciferase2 and the number of labeled cells was 0.993. MRI was used to distinguish the T2* signal of 2 × 10⁷ cells/mL between the labeled (6.67 ± 1.88 ms) and unlabeled cells (10.66 ± 2.22 ms) (P = 0.034). In vivo, individual HepG2 cells expressing EGFP in frozen sections were observed. Labeled cells expressing luciferase2 have been detected since the second day after injection, and the bioluminescence increased with the tumor size. The T2* signal was significantly different between the labeled (6.04 ± 1.60 ms) and unlabeled cells (17.06 ± 2.17 ms) (P <0.001).

Conclusions: A multimodality reporter gene consisting of EGFP, luciferase2, and ferritin was successfully integrated into the HepG2 cell genome via a lentiviral vector and was highly expressed in the daughter cells. These cells could be detected by fluorescence, bioluminescence, and MRI in vitro and in vivo.