Cancer patients, though frequently entering complete remission after successful surgery, and/or irradiation,
and chemotherapy years or even decades later may exhibit overt metastases and aggressive, mostly fatal recurrence on
the basis of clinically silent persistence of disseminated tumor cells. Cellular dormancy is a mode of hibernation/
inactivity caused by a temporary mitotic arrest. It represents the critical phenomenon of latency making metastatic
cancer cells highly refractory to conventional therapies. Regarding host-tumor interactions a broad range of dynamic,
interrelated molecular events may influence the dormancy state of quiescence, like regulators of cell cycle arrest, stress
signaling pathways, autophagy, microenvironmental, angiogenic and immunologic factors, genetic and epigenetic effects.
Nonetheless, the underlying mechanisms are still poorly understood. Moreover, a distinct subset of circulating and
disseminated cancer cells exhibits stem cell-like properties with direct tumor-provoking and metastatis-initiating
capacity, being at least partly responsible for the specific dormancy features. In residual disease a future more detailed
molecular and phenotypic characterization of disseminated tumor cells could represent the prerequisite not only for
prognostic and staging purposes, but for a specific design of therapeutic targeting, as well. By understanding the
elusive dormancy signatures of tumor cells, their cell- and context (microenvironment)-dependent modulation should
provide novel potential therapeutic approaches to avoid or overcome metastatic cancer relapse.