Nanomaterials in Cancer Immunotherapy: A Spotlight on Breast Cancer

Abstract
Breast cancer (BC) is one of the primary causes of death among females worldwide. It can affect a woman at any age after puberty, but the risk of developing the disease increases with age. An early diagnosis and the implementation of an appropriate therapeutic strategy are the two most essential aspects in assuring a favorable prognosis for patients diagnosed with any cancer. There has been significant development in cancer immunotherapy over the past few years. It is among the most effective approaches to fighting cancer and boosts the immune system. In the preclinical setting, immunotherapy using checkpoint blockade antibodies and antigen receptor T cells has shown promising results in BC. Despite this, developing safe and effective immunotherapy against breast cancer is challenging because several novel antigens are poorly immunogenic. Regrettably, conventional immunotherapy confronts further obstacles, such as its inability to trigger the anti-tumor response sufficiently. Most tumors have low immunogenicity due to their origin in healthy cells, making it difficult for the immune system to recognize them as foreign invaders. Additionally, the clinical use of immunotherapy for BC has experienced significant drawbacks, including poor immune responses due to insufficient antigen delivery to the immune cells and uncontrolled immune system regulation, which can promote autoimmunity and nonspecific inflammation. To address these challenges, nanomaterial-based immunotherapy has recently emerged as a potent tool against BC. Scientists have been enthralled by the potential of nanomaterial in BC immunotherapy for decades due to its significant benefits over traditional immunotherapy. Over the past few decades, there has been a considerable increase in the research and application of nanomaterial-based antigens/adjuvants in BC immunotherapy. This review focuses on current advances in BC immunotherapy strategies by focusing on recent breakthroughs in nano immunotherapy.