gms | German Medical Science

Objective: The effect of nanoparticle induced hyperthermia in recurrent glioblastoma is currently under observation in a randomized clinical trial. The effects of hyperthermia on calcium metabolism in glioblastoma cells are not studied sufficiently. The purpose of the present study was to investigate calcium metabolism, apoptosis and necrosis after hyperthermia at different temperatures on the cellular level and to evaluate the possibility of additive treatments to enhance the effect of hyperthermia therapy.

Method: Culured glioblastoma cells (A172) were loaded with the fluorescence calcium indicator FURA-2. Hyperthermia (38°-45°) was applied for 1 hour. Calcium homeostasis was studied during hyperthermia. Apoptosis and necrosis were determined 1h and 24h after onset of hyperthermia by staining with Hoechst33342 and propidium iodide.

Results: Increasing the temperature from 38°C to 44°C in 2 Celsius steps lead to a concomitant rise of intracellular calcium concentration during hyperthermia. This was accompanied by an increase of apoptosis 1h and 24h after onset of hyperthermia (from 5.3% to 10.8% and from 9.8% to 19.4%, respectively) and necrosis as well (from 1.4% to 3.9% and from 4.0% to 7.9%, respectively). Raising hyperthermia up to 45°C lead to a massive rise of necrosis (18.7% after 1h; 62.3% after 24h) and thus to a reduction of apoptotic cell count. Temperatures ≥45°C induced spontaneous calcium oscillations and nearly immediate cell death in roughly 70% of the performed experiments.

Conclusions: In our cell culture model of heat treated glioblastoma cells hyperthermia induces significantly elevated necrosis rates at temperatures ≥45°C. At lower temperatures hyperthermia induces increased apoptosis rates. At temperatures <45°C additive therapies for glioblastoma treatment in combination to hyperthermia may be reasonable to lower the temperature threshold for massive necrosis induction to a feasible level.