Abstract
Objective: Five-aminolevulinic acid (5-ALA)-induced porphyrins in malignant gliomas are potent photosensitizers. Promising results of ALA-PDT (photodynamic therapy) in recurrent glioblastomas have been published. Recently, 5-ALA-induced fluorescence was studied in meningioma surgery. Here, we present an experimental study of ALA-PDT in an in vitro model of primary meningioma cell lines. Methods: We processed native tumor material obtained intra-operatively within 24 h for cell culture. Epithelial membrane antigen (EMA) immunohistochemistry was performed after the first passage to confirm that cells were meningioma cells. For 5-ALA-PDT treatment, about 5000 cells per well were seeded in 20 wells of a blank 96-well plate. Each block of 4 wells was inoculated with 150 µL of 0, 25, 50 and 100 µg/mL 5-ALA solutions; one block was used as negative control without 5-ALA and without PDT. Following incubation for 3 h PDT was performed using a laser (635 nm, 18.75 J/cm2). The therapeutic response was analyzed by the water soluble tetrazolium salt (WST-1) cell viability assay 90 min after PDT. Results: 5-ALA-PDT was performed in 14 primary meningioma cell lines. EMA expression was verified in 10 primary cell cultures. The remaining 4 were EMA negative and PDT was without any effect in these cultures. All 10 EMA-positive cell lines showed a significant and dose-dependent decrease in viability rate (p < 0.001). Cell survival at 5-ALA concentrations of 12.5, 25, 50 and 100 μg/mL was 96.5% ± 7.6%, 67.9% ± 29.9%, 24.0% ± 16.7% and 13.8% ± 7.5%, respectively. For the negative controls (no 5-ALA/PDT and ALA/no PDT), the viability rates were 101.72% ± 3.5% and 100.17% ± 3.6%, respectively. The LD50 for 5-ALA was estimated between 25 and 50 µg/mL. Conclusion: This study reveals dose-dependent cytotoxic effects of 5-ALA-PDT on primary cell lines of meningiomas. Either 5-ALA or PDT alone did not affect cell survival. Further efforts are necessary to study the potential therapeutic effects of 5-ALA-PDT in vivo.
Highlights
Meningiomas account for 20%–34% of intracranial tumors
No toxicity was detected in wells containing 50 μg/mL 5-ALA not subjected to irradiation, neither was toxicity detected in wells without 5-ALA subjected to irradiation (Figure 2)
Application of 5-ALA and subsequent photodynamic therapy (PDT) was found to be toxic in all 10 tested Epithelial membrane antigen (EMA) positive cell lines, and toxicity was found to be dose-dependent in all cell lines
Summary
Meningiomas account for 20%–34% of intracranial tumors. With gliomas, they are the most common primary intracranial tumors with an annual incidence ranging from two to seven per 100,000 for women, and from one to five for men [1,2,3]. Five-aminolevulinic acid (5-ALA) has been under close scrutiny for fluorescence-guided resections because it elicits the accumulation of fluorescing porphyrins in malignant gliomas [15,16,17,18,19,20] These porphyrins are phototoxic and have been explored for photodynamic therapy (PDT) of these tumors [18,21,22,23,24,25,26,27,28]. Systemic 5-ALA application causes fluorescence of gliomas and of meningiomas, but not of adjacent brain tissue enhancing visual distinction of tumor tissue from brain tissue This may help to improve the extent of resection (photodiagnosis) but may be used for PDT [19,32]. In this study, we evaluated the 5-ALA induced PDT susceptibility of 21 primary meningioma cell cultures
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