CANCER STEM CELLS - CURRENT KNOWLEDGE AND TARGETING WITH NATURAL COMPOUNDS

Cancer stem cells (CSCs) constitute a distinct tiny subset of self-renewing, undifferentiated cells within the tumor, that are characterized by a particularly high carcinogenic potential. These cells play a fundamental role at every stage of cancer development from initiation through growth, relapse, and metastasis. CSCs have been identified in vivo in hematological tumors, in solid tumors as well as in vitro in continuous cultures of human tumor cells. Their identification is based on unique biological and molecular features associated with CSC phenotype including expression of specific surface/cytoplasmic markers and genes, overexpression of ABC transporters, or functional assays and xenotransplantation that determine the ability of CSCs to generate tumors. This review focuses on current knowledge of the biology and regulation of CSCs, emphasizing their role in cancer resistance to conventional chemotherapy and radiotherapy. The potential of some natural compounds to inhibit CSCs function damages these cells and/or reduces their resistance to cytostatic therapy and the common methods currently used in CSCs research are discussed.