Biology and treatment of basal-like breast cancer

Breast cancer is one of the most common cancers identified among women worldwide. It is a heterogeneous disease, with each sub-disease displaying unique clinical and histopathologic characteristics. Based on genomic analysis and gene expression profiling, breast cancer has been classified into several distinct subgroups. Estrogen receptor (ER)-positive breast cancers can be treated with antiestrogen drugs such as tamoxifen, and human epidermal growth factor receptor 2 (HER2)-positive breast cancers can be treated with HER2-targeted drugs such as trastuzumab. Because of the low expression of ER and HER2, patients with basal-like breast cancer cannot benefit from these targeted therapies. Thus, to identify and validate pivotal theranostic biomarkers for basal-like breast cancer is of paramount importance. This chapter describes the molecular and histological features of basal-like breast cancer as well as the differences between basal-like breast cancer and the other breast cancer subtypes. It presents current progress in identifying the biomarkers for basal-like breast cancer. It concludes with a description of the current therapeutic strategies to treat basal-like breast cancer and argues that inhibition of basal-like tumor-associated signaling pathways, in conjunction with standard therapies, may enhance the treatment efficacy.