Research progress in mechanisms of drug resistance in cancer stem cells

Cancer is a stem cell disease.A major challenge in treating cancer is the resistance to conventional therapies,which is demonstrated to be related to the cancer stem cells(CSCs) that are responsible for the sustained cancer growth,survival and invasion.Identifying these stem cells in different cancers and defining the microenvironment and the biologic processes necessary for their existence is paramount in developing new clinical approaches with the goal of preventing disease recurrence.The alteration of local microenvironment(niche) around the CSCs,the aberrant activation of development associated signaling pathways,the excessive enhancement of DNA damage repair and the efflux of anticancer drugs mediated by ABC transporters are the main causes of clinical resistance to therapy.This review will briefly outline the cellular and molecular mechanisms underlying cancer progression,focusing on the resistance to therapy.