Homologous Tumor Cell-Derived Delivery of Doxorubicin via Liquid Nitrogen-Treated 4T1 Cells for Targeted Breast Cancer Therapy

Whole cells serve as promising carriers for delivering bioactive molecules owing to their superior biocompatibility, minimal immunogenicity, and extended circulation time. In addition to preserving the intact cellular structure and functions, they provide abundant tumor-associated antigens as immune targets, providing a basis for tumor vaccine development. However, conventional chemotherapy with doxorubicin (DOX) suffers from limited tumor-targeting ability and severe systemic toxicity, which markedly restrict its therapeutic efficacy. In this study, we establish a simple liquid nitrogen freezing strategy to load DOX into liquid-nitrogen-treated (LNT) tumor cells for homologous targeting of breast cancer. The optimized formulation achieved a DOX loading of 38.28 ± 1.61 μg/5 × 10⁶ cells. Both in vitro and in vivo studies confirm that the prepared DOX/LNT cell formulation exhibits excellent safety with no proliferative or pathogenic potential. Regarding the antitumor effect of DOX/LNT cells, in vitro cytotoxicity assays reveal an IC₅₀ value of 1.104 μg/mL, representing a 1.87-fold improvement over free DOX. Furthermore, DOX/LNT cell achieves superior antitumor efficacy by combining chemotherapy with the activation of antitumor immune responses. Following intravenous administration via tail vein injection, in vivo studies demonstrated a tumor inhibition rate of 81.81%, extending the average survival time of breast tumor-bearing mice to 56 days. This approach offers a novel drug delivery system with improved tumor-targeting specificity, representing a precise and effective therapeutic strategy that integrates chemotherapy and immunotherapy for breast cancer treatment.