Effects of Hyaluronan on Breast Cancer Aggressiveness

Simple summary: Breast cancer is the most common neoplasm in women. Although the primary tumor does not appear in a vital organ, lethality is due to the ability of tumor cells to invade and seed distant organs, causing metastases. Approaches to reduce breast cancer cell aggressiveness target hormone receptors that sustain cell growth and motility. However, other factors contribute to aberrant cell behaviors in cancer cells, and nowadays, the role of the environment surrounding cancer cells is evident. The extracellular matrix polysaccharide hyaluronan is a ubiquitous component of the tumor microenvironment that not only modulates cell growth and movement but also plays a critical role in modulating the inflammatory response. In this review, we discuss the role of hyaluronan in relation to the expression of critical hormone receptors. The expression of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) in breast cancer cells is critical for determining tumor aggressiveness and targeting therapies. The presence of such receptors allows for the use of antagonists that effectively reduce breast cancer growth and dissemination. However, the absence of such receptors in triple-negative breast cancer (TNBC) reduces the possibility of targeted therapy, making these tumors very aggressive with a poor outcome. Cancers are not solely composed of tumor cells, but also include several types of infiltrating cells, such as fibroblasts, macrophages, and other immune cells that have critical functions in regulating cancer cell behaviors. In addition to these cells, the extracellular matrix (ECM) has become an important player in many aspects of breast cancer biology, including cell growth, motility, metabolism, and chemoresistance. Hyaluronan (HA) is a key ECM component that promotes cell proliferation and migration in several malignancies. Notably, HA accumulation in the tumor stroma is a negative prognostic factor in breast cancer. HA metabolism depends on the fine balance between HA synthesis by HA synthases and degradation yielded by hyaluronidases. All the different cell types present in the tumor can release HA in the ECM, and in this review, we will describe the role of HA and HA metabolism in different breast cancer subtypes.