Luciferase Reporter Cell Line - C666-1

Mouse orthotopic xenograft tumor models are frequently utilized to investigate the mechanisms underlying tumorigenesis, tumor progression, and preclinical therapeutic interventions. However, there remains a lack of established and highly visualizable orthotopic xenograft models for nasopharyngeal carcinoma (NPC), which hinders the development of therapeutic strategies for this malignancy. In this study, researchers aimed to establish a simple and reliable method for constructing an orthotopic xenograft model of NPC. They subcutaneously injected human NPC cells (C666–1-luc)-which stably express the firefly luciferase gene-into the right axillary region of BALB/c nude mice. Four weeks later, the resulting subcutaneous tumors were excised, sectioned into small fragments, and orthotopically transplanted into the nasopharyngeal region of immunodeficient BALB/c nude mice to induce tumor formation. Tumor growth was monitored using bioluminescence imaging and small-animal magnetic resonance imaging (MRI). Furthermore, histological features and the expression of relevant immunological antigens within the orthotopic NPC xenograft model were analyzed using tissue section analysis and immunohistochemistry (IHC). This study successfully established a visualizable orthotopic xenograft model of NPC. Fluorescence signal detection, micro-MRI imaging, and Hematoxylin-Eosin (HE) staining results confirmed that tumors had successfully grown within the nasopharyngeal region of the nude mice. Additionally, IHC analysis revealed the expression of cytokeratin (CK), CK5/6, P40, and P63 within the orthotopic tumor tissues.

First, researchers constructed human nasopharyngeal carcinoma cells that stably express the firefly luciferase gene (C666-1-luc) (Figure 1a). Subsequently, in vitro and in vivo imaging analyses were performed on both C666-1 and C666-1-luc cells. In the in vitro experiments, C666-1-luc cells exhibited distinct regions of high-intensity luminescence, whereas no such phenomenon was observed in the C666-1 cells (Figure 1b). Three weeks after the subcutaneous injection of C666-1-luc cells into the axillae of mice, in vivo imaging was conducted on the mice bearing subcutaneous tumors. The results revealed that the subcutaneous tumor regions displayed prominent, high-intensity luminescent signals, and the spatial extent of these luminescent regions corresponded precisely with the actual size of the subcutaneous tumors (Figure 1c). Next, the researchers implanted tissue fragments of the luciferase-expressing C666-1-luc cells-which had already formed subcutaneous tumors-into the nasopharyngeal regions of nude mice, thereby establishing an orthotopic xenograft model of nasopharyngeal carcinoma. Following the transplantation of the tumors into the nasopharynx of the nude mice, bioluminescence imaging (BLI) results demonstrated that the tumor regions within the nasopharyngeal cavity emitted strong, stable, and high-intensity luminescent signals. The high-intensity luminescent regions-representing the tumors-gradually expanded over time, indicating that the tumors were undergoing continuous growth within the nasopharynx of the nude mice (Figure 1d). Subsequently, a longitudinal quantitative analysis of the nasopharyngeal carcinoma BLI signals acquired at various time points was performed using the "Region of Interest" (ROI) analysis method. The results demonstrated an upward trend in the intensity of the nasopharyngeal carcinoma BLI signals over time, thereby further corroborating the continuous growth of the tumors (Figure 1e).

Figure 1. Establishment of the mouse orthotopic xenograft model of nasopharyngeal carcinoma. (Chen W, et al., 2024)