Cancer Tills the Premetastatic Field: Mechanistic Basis and Clinical Implications

A growing body of work has shown that cancer metastasis is not a random spontaneous event; rather, it is the culmination of a cascade of priming steps through which a subpopulation of the tumor cells acquires invasive traits while readying a permissive environment, termed the "premetastatic niche," in which distant metastases can occur. Signals from the primary tumor mobilize and adapt immune cells as well as directly communicating with distant niche cells to induce a broad spectrum of adaptations in target organs, including the induction of angiogenesis, inflammation, extracellular matrix remodeling, and metabolic reprogramming. Together, these interactions facilitate the formation of a premetastatic niche composed of a variable mix of resident and recruited immune cells, endothelial cells, and stromal cells connected through a complex signaling network that we are only beginning to understand. Here, we summarize the latest findings on how cancer induces and guides the formation of this premetastatic niche as well as potential prognostic markers and therapeutic targets that may lead to a better understanding and effective treatment of metastatic disease. (C) 2016 AACR.