The problem of cancer dormancy: understanding the basic mechanisms and identifying therapeutic opportunities.

The hiatus observed in the progression of cancer after diagnosis and treatment in a large proportion of patients has led to the notion that a state of cancer dormancy must exist during tumor progression. However, research on this stage of cancer has been limited due to the lack of appropriate models and clinical correlates. Fortunately, the last decade has seen the development of new cancer dormancy models, whole animal and intravital imaging techniques and the molecular characterization of minimal residual disease. These studies enabled researchers to reveal intriguing mechanisms and molecular determinants that define tumor dormancy. It is imperative to understand the basic mechanisms of dormancy, as this will accelerate the development of new markers of progression and novel therapeutic opportunities to induce dormancy and/or eradicate dormant disease. This issue of Cell Cycle includes a "Spotlight on Cancer Dormancy" highlighting major contributions to the field of cancer dormancy from basic and clinical studies. We anticipate that this will initiate a forum of discussion on the problem of cancer dormancy and stimulate investigators to study this rather unexplored but undeniably relevant clinical stage of cancer progression.