Co-application of arsenic trioxide (As 2O 3) and cisplatin (CDDP) on human SY-5Y neuroblastoma cells has differential effects on the intracellular calcium concentration ([Ca 2+] i) and cytotoxicity

Abstract

Arsenic trioxide (As 2O 3) and cisplatin (CDDP) are clinically relevant chemotherapeutics which modulate the intracellular calcium concentration ([Ca 2+] i) by different mechanisms: As 2O 3 depletes intracellular calcium stores while CDDP triggers an influx of Ca 2+. We investigate whether co-application of As 2O 3 and CDDP has an effect on [Ca 2+] i homeostasis, resulting in an increase of cytotoxicity/apoptosis in human SY-5Y neuroblastoma cells. Confocal imaging with Ca 2+-sensitive dye (fluo-4) was used for investigating [Ca 2+] i dynamics. The induction of cell death was assayed using Trypan blue exclusion and Hoechst 33347 staining. Application of As 2O 3 (1 μM) or CDDP (1 μM) increased [Ca 2+] i. The largest elevation was observed when the basic [Ca 2+] i concentration was low. Both, transient and sustained [Ca 2+] i-increases were observed in response to a single application of As 2O 3 or CDDP. Sustained increase showed clear additive effects when both drugs were co-applied. The magnitude of the [Ca 2+] i-increase depends on the order of application; the most pronounced effect occurred when the cells were preincubated with CDDP followed by a co-application with As 2O 3. The sustained [Ca 2+] i elevations resulted in increased cytotoxicity and apoptosis. Therefore, co-treatment with CDDP and As 2O 3 may be a more effective anti-cancer therapy then either agent alone.