Nanomedicine-Based Strategies Targeting Macrophage Polarization in Breast Cancer Bone Metastasis: An Updated Review

The presence of bone metastasis represents one of the common and toughest complications of breast cancer that significantly increases the morbidity rate. Currently available therapies for treating breast cancer have been able to ameliorate symptoms, but still suffer from insufficient accumulation of the drugs in bone metastatic sites and severe side effects on the whole body. The use of drug delivery systems based on nanomedicine has been demonstrated to be a promising approach in improving drug accumulation and pharmacodynamics of drugs in pre-clinical models. Engineered nanoparticles could be tailored in order to improve accumulation in the tumor environment and provide the delivery of drugs to bone metastatic regions. Moreover, recent advances in nanotechnology have provided many new options for imaging and therapeutic experiments in metastatic cancers. Modulation of tumor‑associated macrophage (TAM) polarization represents one of the recently described strategies since M2-like phenotype contributes to tumor growth, immunosuppression and metastasis development, while induction of M1-like phenotype has been proven to be effective in enhancing anti-tumor immune response in pre-clinical models. In this review, we discuss recent advances in the nanomedicine approach that targets TAM polarization in breast cancer bone metastasis, the rationale of the proposed strategies, therapeutic potential and limitations.