Photodynamic therapy with talaporfin sodium induces dose- and time-dependent apoptotic cell death in malignant meningioma HKBMM cells

Abstract

Objective: To investigate the effect of photodynamic therapy (PDT) with the talaporfin sodium (mono-L-asparthyl chlorine e6: NPe-6) on human malignant meningioma cell line HKBMM cells in vitro.

Material and methods: After incubation with NPe6 for 4 h, cells underwent PDT (diode laser irradiation: 3.4 mW/cm² and 1 J/cm². Cell viability was determined in 2 malignant meningioma cell lines (human origin; HKBMM cells and rat origin; KMY-J cells) and human malignant glioma U251 cells with Cell Counting Kit-8 assay. The HKBMM cells were examined for caspase-3 activity, annexin V or propidium iodide (PI) staining, and lactate dehydrogenase leakage. Morphological change was also investigated with phase-contrast microscopy.

Results: In human malignant meningioma HKBMM cells, viability showed a dose- and time-dependent decrease. After 24 h of laser irradiation, NPe6 at 20 μg/ml or more induced a significant decrease in cell viability in both HKBMM cells and KMY-J cells, although they more resistance than the malignant glioma cell line U251 cells. Two kinds of morphological change were also observed in the HKBMM cells, shrinkage of the cell body, indicating apoptosis, and swelling of the cell body, indicating necrosis. In addition, both caspase-3 activity and DNA fragmentation, biochemical markers indicative of apoptosis, showed a dose-dependent increase. The percentage of necrotic cells showing positive staining for annexin V or PI was greater than that of apoptotic cells at a high concentration of NPe6. Lactate dehydrogenase leakage, a biochemical marker of necrosis, also showed a marked increase at a high concentration of NPe6.

Conclusion: Photodynamic therapy with NPe6 induced dose- and time-dependent apoptosis in human malignant meningioma HKBMM cells. At a high concentration of NPe6, however, it induced necrosis.

Keywords: Apoptosis; HKBMM cells; Malignant meningioma; Photodynamic therapy; Talaporfin sodium (NPe6).