Glioblastoma cell line shows phenotypes of cancer stem cells in hypoxic microenvironment of spheroids.

In this study, we examined the phenotypes of CD133-positive cells that were induced in a hypoxic microenvironment of spheroids formed using a glioblastoma cell line (T98G). Colony-formation assay showed that spheroid CD133-positive cells (SCPCs) were more resistant to X-rays and Temozolomide (TMZ) than spheroid CD133-negative cells (SCNCs) sorted from T98G spheroids. In contrast, the sensitivity to X-rays and TMZ was not different between hypoxic cells and normoxic cells of T98G spheroids in a colony-formation assay using green fluorescent protein (GFP) reporter-transfectants to monitor hypoxia. This result suggests that the difference in the sensitivity to X-rays and TMZ between SCPCs and SCNCs did not result from hypoxia. Transwell membrane assay indicated that the migration and inversion ability of SCPCs was higher than that of SCNCs. These results, including the findings obtained previously regarding nestin positivity in SCPCs, strongly suggest that SCPCs are cancer stem cell (CSC)-like cells. Additionally, based on experiments of monolayer culture of T98G cells, it was shown that hypoxia or low pH culture condition is not sufficient for the induction of SCPCs. The three-dimensional cell structure might be a critical factor for SCPC induction.