Is active targeting of brain metastases of breast cancer superior to passive targeting?

摘要

Brain metastasis is a major cause of death in patients with solid cancers. Breast cancer cells have high tendency to migrate towards brain. Cancer cells within brain are characterized by severe aggressiveness and inaccessibility. Currently, breast cancer and its metastasis are the second leading cause of death among women. Tumor microenvironment and blood brain barrier (BBB) represent great obstacles in targeting breast cancer and its metastasis. Chemotherapy is a safer treatment modality for brain metastasis compared with risky surgical resection and brain radiotherapy. Unfortunately, conventional chemotherapy lack penetration of BBB and suffer from multiple resistance mechanisms. Current treatment technologies for brain metastases of breast cancer have limited long-term success and numerous side effects, illustrating the urgent need for novel smart strategies. Various novel drug entities and nanosystems have been employed to improve diagnosis and targeted treatment of breast cancer and its metastasis. Immunotherapy agents and small tyrosine kinase inhibitors have been shown to reduce tumor size and increase survival in patients with breast cancer, but still poorly penetrate BBB. Tailored sized nanoparticles to some extent crossed brain tumor barrier and enhanced drug accumulation in tumors by taking advantage of enhanced permeability and retention. Furthermore, various active targeting strategies have been adopted to improve accessibility to brain malignancies. Therefore, to achieve enhanced antitumor therapy against breast cancer and its brain metastasis, multi-talented delivery systems are urgently needed for optimal treatment. This review focuses on the various active and passive targeting technologies for the treatment of breast cancer brain metastases in the past decade. A comprehensive summary and examples along with pros and cons of each system will be discussed. Different treatment modalities and nanotechnology facilities will be demonstrated to aid in designing the optimal smart, safe, targeted and effective systems to combat brain metastases of breast cancer.