Enhancing the effect of 5-aminolevulinic acid based photodynamic therapy in human meningioma cells

Abstract

The interest in photodynamic therapy (PDT) in cancer treatment has continuously increased since its' advent in the 1960s. In neurosurgery, 5-aminolevulinic acid based photodynamic therapy (5-ALA PDT) is used for malignant glioma in vitro and in vivo. Data about PDT in meningioma, which is the second most frequent primary brain tumor, is sparse. Preliminary work indicated that meningiomas are more resistant to PDT than gliomas. In the present study we evaluated whether the effect of 5-ALA PDT on malignant meningioma cells can be increased by ciprofloxacin and changes in incubation time, factors known to influence the effectiveness of PDT in other tumor entities. An in vitro-PDT model of a malignant human meningioma cell line (KT21-MG) was chosen as screening method. Cultured cells were incubated with varying 5-ALA concentrations for 4h and exposed to PDT (control group). Two experimental groups, one with 5-ALA and ciprofloxacin (group I) and one with 24-h ALA incubation time (group II), were studied, respectively. Cell viability was assessed by WST-1 assay. Ciprofloxacin and longer ALA incubation time significantly increased the lethal effect of 5-ALA PDT on meningioma cells. Efficacy of 5-ALA PDT could be increased by adjunction of ciprofloxacin in conventional clinical dosing and by prolongation of ALA incubation time. As ciprofloxacin is a common antibiotic with good tissue penetration, low toxicity and a favorable risk profile it represents a clinically interesting method for future PDT trials in meningiomas.