Cell dormancy and tumor refractory.

Metastasis of tumor cells from primary tumor and growth at secondary sites are the major cause of mortality in cancer patients. This event may occur years and even decades after successful removal of the primary tumor and adjuvant therapy. Relapse and metastasis are universally existed in various malignancies. This phenomenon is attributed to a small amount of residual tumor cells remained in host for years, which is called as dormancy. Tumor dormancy is characterized by the balanced cell proliferation and cell death, immune evasion from host, non-angiogenic feature, insufficiency of metastatic capacity, cell cycle arrest as well as resistant to conventional chemotherapy. The molecular expressing profile suggested that dormancy is a state of quiescent cancer stem-like cells (CSCs), which are more resistant to chemotherapy and targeted therapy. Hitherto, the progression on tumor dormancy is relatively slow because there are no proper experimental models and biomarkers for identifying the dormant cells. It is no doubt that clarifying the regulatory mechanism of enter or exit of dormancy will help scientists to develop targeted strategy for eliminating dormant tumor cells, and then hinder the distant relapse and metastasis for various malignancies. This review focuses on tumor dormancy, the association of tumor dormancy with CSCs and strengthens the angiogenic switch for enter or exit of dormancy. It enlightens researchers to explore and develop more specific targeted drugs for clearance of the relapse danger.