As the role that the tumor microenvironment plays in the development of cancer becomes increasingly well understood, a new player has emerged: myeloid-derived suppressor cells (MDSCs).
Now, researchers studying the biology of these cells have uncovered numerous effects of MDSCs on cancer development and progression beyond their impact on the immune system. As a result, MDSCs represent an increasingly attractive therapeutic target and predictive marker in patients with a variety of different cancer types.
A Hallmark of Disease
The existence of cells derived from the bone marrow with potent immunosuppressive effects was noted almost 40 years ago. In the intervening years, our understanding of the origin, nature, and function of these cells has evolved, culminating in the coining of the term myeloid-derived suppressor cells in 2007.
Figure. MDSCs in Tumor Microenvironment
Myeloid-derived suppressor cells (MDSCs), which do not exist in healthy individuals, interact with many components of the immune system, including dendritic cells, natural killer (NK) cells, macrophages, and T-regulatory (Treg) cells in the process of promoting cancer.
Adapted from Condamine et al. Annu Rev Med. 2015;66:97-110; and Srivastava et al.
In the animal models in which MDSCs have been extensively studied, they are readily identified by several cell surface markers; in humans, however, they have proved to be a little more difficult to characterize, and identifying distinguishing markers is one of the key challenges for oncology researchers. To further complicate matters, there are several different types of MDSCs.
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