Scientists from the National Cancer Institute (Bethesda, MD), M. J. Son et al., reported in the May 8th issue of Cell Stem Cell their study results on identifying a new marker for a subpopulation of cancer stem cells from human glioblastoma mutiforme (GBM). The investigators noted that although CD133+ cells from GBM are reported enriched for cancer stem cells, approximately 40% of the cells isolated from fresh GBM specimens lack the marker. In the current study, the researchers found that stage-specific embryonic antigen 1 (SSEA-1/Lex)+ co-expressed on the surface of CD133+ were highly tumorigenic when implanted into immunocompromised animals. The experimental results also revealed that the SSEA-1+ cells underwent asymmetrical cell division which resulted in both SSEA-1+ and SSEA-1- daughter cells. The SSEA-1+ cells were able to self-renew with multilineage differentiation potential. The authors concluded that their observations suggest that "SSEA-1 may be a general TSC/TIC enrichment marker in human GBMs."

Canadian scientists J. J. P. Kelly et al. from the University of Calgary published in the April 23rd online edition of Stem Cells their findings on isolating and characterizing a subpopulation of human brain tumor stem cells (BTSCs) from primary glioma tumors. The study involved culturing CD133+ and CD133- BTSCs from glioblastoma multiforme (GBM) and analyzing their proliferative potential in the absence of mitogens. The experimental data revealed that both of the above BTSC subpopulations were able to proliferate, self-renew and form multipotent neurospheres in the absence of exogenous mitogens. Epidermal growth factor (EGF) and fibroblast growth factor-2 (FGF2) were shown to enhance survival, proliferation, and sphere size. Antagonists of the EGF receptor and the EGF signaling pathway were found to reduce mitogen-independent proliferation and neurospheres formation. In vivo results revealed that as few as 10 mitogen independent BTSCs could form tumors when implanted intracranially into immunocompromised mice. The authors concluded from their study observations that "exogenous mitogen independence, mediated in part through EGFR signaling, is one characteristic that distinguishes CD133+ and CD133- GBM BTSCs from neural stem cells."