A novel immunocompetent mouse model of neuroblastoma bone marrow metastasis as a therapeutic target for mesenchymal stem cell-based immunotherapy.

BACKGROUND

Recent advances in immunotherapy have highlighted the need for clinically relevant immunocompetent models of metastatic neuroblastoma. However, such models of bone marrow (BM) metastasis remain limited. We previously developed a gene-modified mesenchymal stem cell (MSC)-based immunotherapeutic strategy that functions as a tumor-selective drug delivery system (DDS) and demonstrated its antitumor efficacy in a localized TH-MYCN neuroblastoma model. Therefore, this study aimed to establish a reproducible immunocompetent mouse model of neuroblastoma BM metastasis as a platform for evaluating novel therapeutic strategies.

METHODS

Primary cultured tumor cells derived from spontaneous tumors of homozygous TH-MYCN mice were intravenously injected (1 × 107 cells) into the orbital venous plexus of wild-type mice. BM metastasis was assessed 21 days after injection using spinal immunohistochemistry and ex vivo culture of femur-derived bone marrow cells with GD2 expression analysis by flow cytometry. A separate cohort of 17 mice were monitored for survival. MSC biodistribution was evaluated after intraperitoneal administration of DiR-labeled or copGFP-transduced MSCs using an in vivo imaging system (IVIS) and immunohistochemistry.

RESULTS

BM metastases were detected in 6 of 9 mice (66.7%). Twelve of the 17 mice died at 17-74 days (median, 29 days) after injection. Mice with BM metastasis developed significant anemia compared with controls. IVIS and immunohistochemical analyses demonstrated MSC accumulation in spinal BM lesions.

CONCLUSION

We established a clinically relevant immunocompetent neuroblastoma BM metastasis model and demonstrated MSC homing to metastatic BM lesions, providing a useful platform for evaluating therapies targeting metastatic neuroblastoma.