TABLE 1.

Classification and major features of stem cells reported in glioma therapy.

Stem cell	Defining criteria	Source/Niche	Linage
Pluripotent stem cells: capacity to differentiate into any cell of all three germ layers
Embryonic stem cells (ECSs)	Markers of pluripotency as found in ICM cells: Transcription factors: Oct4, Nanog, Rex-1 Cell surface markers: SSEA-3, SSE-A4, TRA-1-60, TRA-1-81, alkaline phosphatase	Blastocyst Morula Growth-arrested embryos Somatic cell nuclear transfer Single blastomere	As defined by pluripotency
Induce pluripotent stem cells (iPSCs)	Essentially the same than ECS markers	Reprogrammed adult somatic cells—usually fibroblasts or skin cells.	As defined by pluripotency given than iPSC are functionally equivalent to ECS
Multipotent stem cells: capacity to differentiate into cells of one of the three germ layers
Neural stem cells (NSCs)	Positive: GFAP, CD133, CD184, and Nestin, Sox1, Sox2, and Pax6 Negative: CD271, CD44, CD24 Immune profile: Absent HLA II	Subependymal zone (SEZ)—lining the lateral ventricles Dentate gyrus of the hippocampus *Obtained from fetal and adult mammals	Neurons Oligodendrocytes Astrocytes Ependymal cells
Mesenchymal stem cells (MSCs)	MSC must comply with ISCT criteria: Positive (>95% +): CD105, CD73, CD90 Negative (<2% –): CD45, CD34, CD14 or CD11b, CD79α, or CD19, HLA DR Adherence to plastic in standard culture conditions In vitro differentiation to osteoblast, adipocytes, and chondroblasts. Immune profile: Absent HLA II	Adult tissues: adipose tissue, bone marrow, peripheral blood, dental pulp, ligamentum flavum, synovium, endometrium, sweat glands, and milk Fetal tissues: umbilical cord, umbilical cord blood, Wharton jelly, amniotic fluid, chorionic villi, and placenta	Osteoblast Adipocytes Chondroblast *Differentiation into ectodermal and endodermal linages has also been reported
Hematopoietic stem cells (HMSs)	Negative: CD45R/B220 (B cells), Gr-1 (granulocytes), Mac-1 (macrophages), Ter-119 (erythrocytes) and CD4/CD8 (lymphocytes)—for phenotypic enrichment. Positive: Sca-1, c-Kit, CD150 *They appear as side population in dye exclusion assays due to the high expression of MDR pumps	Adult tissues: bone marrow, peripheral blood Non-adult tissues: umbilical cord blood, yolk sac, liver, spleen	Hematopoietic cells

IMC, inner mass cells; MDR, multidrug resistance.