Overcoming Breast Cancer Resistance to Targeted, Chemo-, and Immuno Therapy: Mechanisms and Strategies to Overcome Resistance and Facilitate Drug Development

Breast cancer substantially impacts female mortality, and symptoms can differ among individuals. Hence, it is crucial to tailor treatment modalities to individual patients to ensure efficient therapy. The main biomarkers for breast cancer include the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2/ERBB2), typically used to classify various types of breast cancer, such as luminal, HER2-positive (HER2+), and triple-negative breast cancer, and to determine the most suitable treatment strategies. Despite technological improvements and continuous research on drugs, including chemotherapy, targeted therapy, and immunotherapy, mortality rates for breast cancer remain markedly high owing to drug resistance. This chapter provides an in-depth examination of the fundamental mechanisms that contribute to resistance against several treatment modalities, including endocrine therapy, anti-HER2-targeted therapy, chemotherapy, and immunotherapy. Furthermore, the chapter discusses recent relevant advances and clinical trials to address resistance and drug development. Specifically, the application of integrated bioinformatics analysis to uncover potential anticancer therapeutics was emphasized. Accordingly, this chapter seeks to provide notable insights and suggestions to accelerate the advancement of anti-breast cancer treatments, with a specific focus on addressing the issue of treatment resistance in breast cancer.