evaluation of tumor malignancy based on expression analysis of genome instability factors

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We established a cancer stem cell line, U87CS, by means of spheroid culture of U87MG cells derived from glioblastoma in neuronal stem cell medium. U87CS cells presented high tumorigenicity after intracranial transplantation into nude mice brains and positive immunohistochemical staining of CD133, a marker for a subset of leukemia and glioblastoma cancer stem cells. Telomerase of U87CS cells was higher than original U87MG cells. With ICRF193, an inhibitor of G2/S cell division, decatenation checkpoint activity increased in U87CS cells more than U87MG cells. The gene expression of CD133 and multidrug resistance (MDR) 1 on U87CS cells increased an average of 47.18 and 8.51 times, respectively, compared to the level on U87MG cells by Real time quantitative RT-PCR. U87CS cells possessed stronger drug-resistance to conventional anti-cancer drugs, such as Doxorubicin (Dox), etoposide (VP-16), and BCNU, than U87MG cells. Single-color flow cytometric analysis showed the uptake of Dox content into U87CS cells were lower than U87MGcells and verapamil, an inhibitor of ABC transporters, increased the uptake on both of U87MG and U87CS cells. Double immunofluoresence staining showed co-expression of CD133 and MDR1 on U87CS cells transplanted into nude mice brains. Furthermore, we identified the crossreactivity of CD133 and MDR1 in surgical specimens of recurrent glioblastomas after surgical removal and radiochemotherapy. These results suggest that CS cells may be resistant to cell damage conditions including anti-cancer drugs and represent a novel target for glioblastoma therapeutics.