Synergistic effect of dichloroacetate on talaporfin sodium-based photodynamic therapy on U251 human astrocytoma cells

lncRNA MEG3 Inhibits the Proliferation and Growth of Glioma Cells by Downregulating Bcl-xL in the PI3K/Akt/NF-κB Signal Pathway

This study was conducted to investigate the impact and mechanisms of lncRNA MEG3 on glioma cells. lncRNA MEG3 was lowly expressed in glioma cells as compared to noncancer cells. Overexpression of MEG3 significantly downregulated the expression of Bcl-xL, slightly upregulated the expression of NF-κB p65 and IκBα, and reduced the proliferation of glioma cells with increased apoptosis and the migration and invasion ability. Subsequently, glioma cells overexpressing MEG3 had less tumorgenicity in xenograft mouse models. It is likely that MEG3 induces apoptosis in glioma cells via downregulating the Bcl-xL gene in the PI3K/Akt/NF-κB signal pathway to reduce the development of glioma.

Novel Photosensitizer β-Mannose-Conjugated Chlorin e6 as a Potent Anticancer Agent for Human Glioblastoma U251 Cells

A photosensitizer is a molecular drug for photodynamic diagnosis and photodynamic therapy (PDT) against cancer. Many studies have developed photosensitizers, but improvements in their cost, efficacy, and side effects are needed for better PDT of patients. In the present study, we developed a novel photosensitizer β-mannose-conjugated chlorin e6 (β-M-Ce6) and investigated its PDT effects in human glioblastoma U251 cells. U251 cells were incubated with β-M-Ce6, followed by laser irradiation. Cell viability was determined using the Cell Counting Kit-8 assay. The PDT effects of β-M-Ce6 were compared with those of talaporfin sodium (TS) and our previously reported photosensitizer β-glucose-conjugated chlorin e6 (β-G-Ce6). Cellular uptake of each photosensitizer and subcellular distribution were analyzed by fluorescence microscopy. β-M-Ce6 showed 1000× more potent PDT effects than those of TS, and these were similar to those of β-G-Ce6. β-M-Ce6 accumulation in U251 cells was much faster than TS accumulation and distributed to several organelles such as the Golgi apparatus, mitochondria, and lysosomes. This rapid cellular uptake was inhibited by low temperature, which suggested that β-M-Ce6 uptake uses biological machinery. β-M-Ce6 showed potent PDT anti-cancer effects compared with clinically approved TS, which is a possible candidate as a next generation photosensitizer in cancer therapy.

Possible mechanism of heme oxygenase-1 expression in rat malignant meningioma KMY-J cells subjected to talaporfin sodium-mediated photodynamic therapy

BACKGROUND

We previously demonstrated that heme oxygenase-1 (HO-1) induction may contribute to a protective response against photodynamic therapy (PDT) using talaporfin sodium (TS) in rat malignant meningioma KMY-J cells. In the present study, we examined the mechanism of HO-1 induction by PDT with TS (TS-PDT) in KMY-J cells.

METHODS

KMY-J cells were incubated with 25 μM TS for 2 h and then exposed to 664 nm diode laser irradiation at 1 J/cm². The gene and protein expression levels of HO-1 and hypoxia-inducible factor-1α (HIF-1α) were determined by real-time RT-PCR and western blot analysis, respectively. Cell viability was measured using the cell counting kit-8 assay.

RESULTS

mRNA and protein levels of HO-1 in KMY-J cells were increased significantly at 3, 6, and 9 h after laser irradiation and the increased mRNA level of HO-1 was decreased by antioxidant N-acetyl cysteine treatment. The protein level of HIF-1α, which mediates transcriptional activation of the HO-1 gene, was increased significantly at 1 h after laser irradiation. Additionally, induction of mRNA expression of HO-1 by TS-PDT was diminished by HIF-1α inhibitor echinomycin. We also demonstrated that echinomycin significantly augmented the cytotoxic effect of TS-PDT.

CONCLUSIONS

Our findings indicate that TS-PDT may induce HO-1 expression via reactive oxygen species production and then HIF-1 pathway activation in KMY-J cells, and the HO-1 induction may cause attenuation of the therapeutic effect of TS-PDT.