Luciferase Reporter Cell Line - RD

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children; for patients with high-risk or metastatic disease, it remains a highly challenging malignancy associated with a poor prognosis. Here, researchers report a novel immunotherapy strategy for RMS: the combined application of chimeric antigen receptor (CAR) natural killer (NK) cells targeting the epidermal growth factor receptor (EGFR) and radiotherapy. In both two-dimensional cultures and three-dimensional spheroid models, primary human EGFR-CAR NK cells demonstrated enhanced cytotoxicity against a variety of RMS cell lines. Furthermore, EGFR-CAR NK cells exhibited exceptional killing efficacy against chemotherapy-resistant RMS cells as well as patient-derived tumor samples. Most importantly, in in vivo RMS xenograft models, EGFR-CAR NK cells demonstrated superior tumor-homing capabilities compared to untransduced, unmodified NK cells. Notably, combining EGFR-CAR NK cell therapy with fractionated radiotherapy further promoted the infiltration of NK cells into the tumor microenvironment and effectively inhibited tumor growth.

In this study, researchers subcutaneously (s.c.) inoculated NSG mice with luciferase-expressing RD cells and confirmed the successful engraftment of tumor cells via bioluminescence imaging (BLI) (Figure 1A). Subsequently, 10 × 10⁶ fluorescently labeled NK cells were administered to the tumor-bearing mice as a single dose via intravenous injection. The researchers confirmed the tumor's location using BLI and, while the mice were under anesthesia, monitored the migration dynamics of the NK cells in real-time over a 120-hour period using fluorescence detection (Figure 1B). At 24, 48, and 120 hours post-inoculation, the presence of both EGFR-CAR NK cells and NT NK cells was detected at the tumor site, as well as in other NK cell homing organs such as the lungs, liver, and spleen. Notably, quantitative analysis of the fluorescence signals within the tumor region revealed that EGFR-CAR NK cells exhibited significantly enhanced migration capabilities toward the tumor site compared to NT NK cells (Figure 1C). However, immunofluorescence analysis of tissue sections did not confirm that the immune cells had infiltrated into the deep interior of the solid tumor mass (Figure 1D). Meanwhile, the presence of NK cells was readily detectable in the spleens of mice treated with either NT or EGFR-CAR NK cells (Figure 1E). Consistent with the aforementioned results, despite the administration of three consecutive therapeutic injections (each comprising 10 × 10⁶ EGFR-CAR or NT NK cells) on days 7, 11, and 14 post-tumor inoculation, this treatment regimen failed to significantly delay tumor growth.

Figure 1. EGFR-CAR NK cells home to established RMS tumor xenografts in NSG mice. (Reindl L M, et al., 2025)