SC-27 * CD13 REPRESENTS A NOVEL BRAIN TUMOR STEM CELL MARKER FOR GLIOBLASTOMA

Abstract

Glioblastoma multiforme (GBM) is a very deadly and highly vascularized tumor, but targeting glioma angiogenesis by vascular endothelial growth factor inhibition has been minimally successful. Thus, understanding the molecular mechanisms that control glioma angiogenesis and progression could lead to significant new therapies. We previously described that mitochondrial DNA (mtDNA) depletion induces increased tumor angiogenesis, decreased mouse survival, increased resistance to chemotherapy, and an increase in CD133 (a well-known stem cell marker). Because glioma enriched with brain tumor stem cells (BTSCs) share similar properties with mtDNA depleted glioma cells, we hypothesize that genes up-regulated in mitochondrial depleted cells could be signature markers of BTSCs. Thus, mtDNA could be essential for the maintenance and expansion of BTSC populations. We ran an RT Profiler PCR array for angiogenesis on both U251 ρ° cells depleted of mtDNA and on the parental, isogenic U251 glioma cells. CD13 mRNA expression was increased 200 fold in ρ° cells over U251 cells. Using fluorescence-activated cell sorting and immunocytochemisty we found that CD13 is significantly increased in ρ° cells over U251 cells, and is not regulated by hypoxia (1% O2). Purification of the CD13+ population by magnetic-activated cell sorting revealed that these cells form neurospheres when cultured in Neurobasal (NB) medium. In addition, 60% of CD13+ cells were also CD133+ in NB medium, while only 10% of CD13+ cells were also CD133+ in DMEM/F-12 medium. These findings suggest CD13 may be a marker of cancer stem cells in GBM. Further elucidation of the molecular mechanisms controlling the expression of CD13 may reveal novel therapuetic targets capable of improving the treatment of GBM.