Etoposide toxicity on human neuroblastoma cells in vitro is enhanced by preceeding hyperthermia

Background. Thermal enhancement has been proven in vitro for the cytotoxic effect of alkylants and platinum compounds, not, however, for etoposide, wh ich acts synergistically to these drugs. Procedure, Our in vitro study on a neuroblastoma cell line confirmed previous results in other tumor models t hat the cytotoxicity of etoposide (12.8% as compared to untreated controls) is not enhanced by simultaneous heating to 40 or 42 degreesC for 1 hr (11. 9%), as jugded by colony forming assay. Results. The same temperature appli ed 24 hr before the drug resulted in a significant decrease of colonies (6. 1%). Double treatment with etoposide within a 24-hr-interval yielded a simi lar result (5.6%). The colony number could be further decreased by adding h yperthermia 24 hr before the second treatment (1.3%). Conclusions. We demon strate in vitro that the enhancing effect of increased temperature on the c ytotoxicity of etoposide on neuroblastoma cells is not absent, but depends on scheduling. The temperature range used is achievable in total body hyper thermia. Thus, our results are relevant for possible treatment of dissemina ted neuroblastoma. Med. Pediatr. Oncol. 36:197-198, 2001. (C) 2001 Wiley-Li ss, Inc.