Читать книгу The SAGE Encyclopedia of Stem Cell Research - Группа авторов - Страница 279

CSCs are commonly identified and enriched using strategies for identifying normal stem cells, including fluorescence-activated cell sorting (FACS), with antibodies directed at cell-surface markers, and functional approaches including side population analysis or Aldefluor assay (an assay that detects stem and progenitor cells based on their expression of the enzyme aldehyde dehydrogenase, rather than cell surface phenotype). The CSC-enriched population purified by these approaches is then implanted, at various cell doses, in immune-deficient mice to assess tumor development capacity. This in vivo assay is called limiting dilution assay. The tumor cell subsets that can initiate tumor development at low cell numbers are further tested for self-renewal capacity in serial tumor studies. CSCs can also be identified by efflux of incorporated Hoechst dyes via multidrug resistance (MDR) and ATP-binding cassette (ABC). The use of Oct4 as a marker for stemness of embryonic stem cells is well established. Oct4 expression has been demonstrated in several adult normal and cancer tissues, in adult human and canine tissues, in human cancer cell lines, and in normal adult human stem cells.

Another in vitro approach for identification of cell subsets enriched with cancer stem cells is sphere-forming assays. Many normal stem cells are capable, under special culture conditions, of forming three-dimensional spheres, which can differentiate into multiple cell types. As with normal stem cells, the CSCs isolated from brain or prostate tumors also have the ability to form anchorage-independent spheres.

Data over recent years have indicated the existence of CSCs in various solid tumors. For isolating CSCs from solid and hematological tumors, markers specific for normal stem cells of the same organ are commonly used. A number of cell surface markers have proven useful for isolation of subsets enriched for cancer stem cells, including CD133 (also known as PROM1), CD44, CD24, EpCAM (epithelial cell adhesion molecule, also known as epithelial specific antigen, ESA), THY1, and ATP-binding cassette B5 (ABCB5).