Cell Death Forms and HSP70 Expression in U87 Cells after Ionizing Radiation and/or Chemotherapy

Background: Several types of cell death can induce the activation of the immune system by releasing factors of damage. Aim: To identify different cell death modalities using U87 glioblastoma cell line after radio-chemotherapy treatments by analyzing the expression of HSP70 after gamma-ray irradiation and temozolomide treatment. Materials and Methods: U87 cell line was irradiated with 2, 4, 8, 10 and 20 Gy, treated with 200 mu M of temozolomide, or subjected to combined treatments of these. Results: Forty-eight hours after treatment, apoptosis was more prevalent than necrosis, especially after gamma-radiation with a somewhat dose-dependent trend. Temozolomide did not seem to induce significant modifications of the pattern of cell death and protein expression. Temozolomide-induced cell death was lower or equal to that obtained with high dose radiotherapy. A low synergism between the two treatments was observed. Conclusion: This cell line showed a marked radioresistance to conventional clinical doses, showing attempts to repair the induced damage, while temozolomide treatment showed no cytotoxic effects.