Phase-Transformation Nanoparticle-Mediated Sonodynamic Therapy: An Effective Modality to Enhance Anti-Tumor Immune Response by Inducing Immunogenic Cell Death in Breast Cancer.

Purpose: Immunologically quiescent of breast cancer cells has been recognized as the key impediment for the breast cancer immunotherapy. In this study, we aimed to investigate the role of nanoparticle-mediated sonodynamic therapy (SDT) in promoting anti-tumor immune of breast cancer cells and its potential immune mechanisms.
Materials and Methods: The phase-transformation nanoparticles (LIP-PFH nanoparticles) were in-house prepared and its physiochemical characters were detected. The CCK-8 assay, apoptosis analysis and Balb/c tumor model establishment were used to explore the anti-tumor effect of LIP-PFH nanoparticles triggered by low-intensity focused ultrasound (LIFU) both in vitro and in vivo. Flow cytometry and immunohistochemistry of CD4 ⁺ T, CD8 ⁺ T, CD8 ⁺ PD-1 ⁺ T in blood, spleen and tumor tissue were performed to represent the change of immune response. Detection of immunogenic cell death (ICD) markers was examined to study the potential mechanisms.
Results: LIP-PFH nanoparticles triggered by LIFU could inhibit the proliferation and promote the apoptosis of 4T1 cells both in vitro and in vivo. CD4 ⁺ T and CD8 ⁺ T cell subsets were significantly increased in blood, spleen and tumor tissue, meanwhile CD8 ⁺ PD-1 ⁺ T cells were reduced, indicating enhancement of anti-tumor immune response of breast cancer cells in the nanoparticle-mediated SDT group. Detection of ICD markers (ATP, high-mobility group box B1, and calreticulin) and flow cytometric analysis of dendritic cell (DC) maturity further showed that the nanoparticle-mediated SDT can promote DC maturation to increase the proportion of cytotoxic T cells by inducing ICD of breast cancer cells.
Conclusion: The therapy of nanoparticles-mediated SDT can effectively enhance anti-tumor immune response of breast cancer.
Competing Interests: The authors report no conflicts of interest in this work.
(© 2021 Si et al.)