There is biological and clinical evidence that mammalian tumors are highly heterogeneous at single-cell level, and that only a minority of the cancer cells have limitless replicative potential in vitro and in vivo. Here we review the different strategies currently used for the functional isolation of cancer cells with in vivo cancer initiation potential and self-renewal. These tools are currently used to better define their molecular, phenotypic, and drug-resistance characteristics in preclinical and clinical studies.
Keywords: Aldehyde dehydrogenase; Cancer stem cells; Cancer-initiating cells; FACS; Methods; Side population; Tumorigenicity; Tumorspheres.