Human umbilical cord blood-derived mesenchymal stem cells and their effect on gliomas.

Glioblastoma in adults and pediatric brain tumors have become one of the favored vehicles for cancer stem cell hypothesis. There is compelling evidence that human glioblastoma is a heterogeneous tumor composed of lineage committed tumor cells and a subpopulation of cancer stem cells. These tumor-initiating stem cells have a high tumorogenic potential and low proliferationrate. [1],[2],[3],[4],[5] Glioma stem cells are found to be essentially similar to normal stem cells expressing CD133 stem cell marker. Cancer stem cells derived from human tumors and cell lines are capable of recapitulating original polyclonal tumor when transplanted into immunodeficient nude mice, indicating the synergistic influence of immune suppression on tumor implantation. It is well recognized that cancer stem cells can be enriched and harvested from many human tumor biopsy specimens using the CD133 (Prominin 1) as a cell surface marker. Yet a subpopulation of CD133 negative stem cells exist with low turnover rate and tumorogenic propensity. [4],[6],[7] These cancer stem cells contribute to tumor radio/chemo resistance by an increase in DNA repair capacity through preferential activation of DNA damage response check points. [8] Bao et al, have shown that L1CAM (neural cell adhesion molecules L1, CD 171, which regulates neural cell growth, survival, migration, axonal outgrowth and neurite outgrowth) is essential for growth and survival of CD133 positive glioma stem cells, both in vivo and in vitro, thus suggesting to be a possible therapeutic target to suppress the tumor growth. [9]