Induced expression and subcellular localization of the Bcl-2 protein in cultured glioma cells

It has recently been shown that the bcl-2 gene is involved in the growth and development of certain tumors by suppressing apoptosis. To explore the possible involvement of the Bcl-2 protein in gliomas, three human glioma cell lines (T98G, A172, and U251) were examined for the presence of this protein. It could be documented by confocal laser microscopy that the Bcl-2 protein was localized mainly in mitochondria and nuclear membrane of T98G cells. Flow cytometric analysis revealed that 71-87% of the cultured glioma cells expressed the Bcl-2 protein. Treatment of U251 cells with ACNU for 24 h induced increased Bcl-2 protein expression; induction was dose dependent. Exposure of T98G and A172 cells to ACNU did not affect their Bcl-2 protein levels. Southern blot analysis revealed no chromosomal translocation in the cells studied. These findings suggest that Bcl-2 protein overexpression in glioma cells may partly contribute to tumor growth and tolerance to chemotherapeutic agents.