TRANSFECTION OF C6 GLIOMA-CELLS WITH THE BAX GENE AND INCREASED SENSITIVITY TO TREATMENT WITH CYTOSINE-ARABINOSIDE

Object. Genes known to be involved in the regulation of apoptosis incl ude members of the bcl-2 gene family, such as inhibitors of apoptosis (bcl-2 and bcl-xl) and promoters of apoptosis (bax). The authors inves tigated a potential approach for the treatment of malignant gliomas by using a gene transfection technique to manipulate the level of an int racellular protein involved in the control of apoptosis. Methods. The authors transfected the murine bax gene, which had been cloned into a mammalian expression vector, into the C6 rat glioma cell line. Overexp ression of the bax gene resulted in a decreased growth rate (average d oubling time of 32.96 hours compared with 22.49 hours for untransfecte d C6, and 23.11 hours for clones transfected with pcDNA3 only), which may be caused, in part, by an increased rate of spontaneous apoptosis (0.77 +/- 0.15% compared with 0.42 +/- 0.08% for the vector-only trans fected C6 cell line; p = 0.038, two-tailed Student's t-test). Treatmen t with 1 mu M cytosine arabinoside (ara-C) resulted in significantly m ore cells undergoing apoptosis in the cell line overexpressing bar tha n in the vector-only control cell line (23.57 +/- 2.6% compared with 5 .3 +/- 0.7% terminal deoxynucleotidyl transferase-mediated biotinylate d-deoxyuridine triphosphate nick-end labeling technique-positive cells ; p 0.007). Furthermore, measurements of growth curves obtained immedi ately after treatment with 0.5 mu M ara-C demonstrated a prolonged gro wth arrest of at least 6 days in the cell line overexpressing bar. Con clusions. These results can be used collectively to argue that overexp ression of bax results in increased sensitivity of C6 cells to ara-C a nd that increasing bax expression may be a useful strategy, in general , for increasing the sensitivity of gliomas to antineoplastic treatmen ts.