Overexpression of E2F1 in glioma-derived cell lines induces a p53-independent apoptosis that is further enhanced by ionizing radiation

Glioma cell lines show variable responses to radiation in a manner influenc ed by their p53 status, Irradiation of glioma cell lines does not generally induce apoptosis, When wild-type p53 is present, these cells undergo a G(1 ) arrest that is closely associated with increased radiosensitivity as meas ured by clonogenic survival, Previously, others have shown that dysregulate d overexpression of E2F1 induces apoptosis in cell lines with either functi onal or inactivated p53, We found that regardless of p53 status, apoptosis induced by overexpression of E2F1 in glioma cell lines was further enhanced by treatment with ionizing radiation. BAX induction did not follow E2F1 ov erexpression or irradiation in the glioma cell lines tested. Thus, the apop totic response of glioma-derived cells to irradiation can be enhanced by E2 F1 by a mechanism that does not involve the induction of BAX.