Knockdown of long non-coding RNA PCAT1 in glioma stem cells promotes radiation sensitivity.

This study aimed to investigate the function of glioma stem cells (GSCs) and the role of PCAT1. This study dissociated the differences between GSCs and glioma cells in terms of apoptosis rate and γH2AX positive cells levels after radiation. Microarray was carried out to detect that expressed PCAT1, and it was testified by RT-qPCR. After transfection, GSCs were used to investigate the influence of PCAT1 on radiation sensitivity. Sphere-formation capability was first examined. Cell apoptosis rate after radiation of 0 Gy or 6 Gy was analyzed by flow cytometry, and the level of γH2AX positive cells after 6 Gy radiation were compared. CCK8 assay was used to investigate the cell proliferation and RT-qPCR was used to examine miR-129-5p and HMGB1 expression. GSCs exhibited great capability in sphere formation and lower expression in apoptosis and γH2AX positive cells rates after 6 Gy radiation. PCAT1 had higher expression in GSCs. PCAT1 knockdown restrained the sphere-formation ability, increased the apoptosis rate and DNA damage under the treatment of radiation. Moreover, knockdown of PCAT1 inhibited the cell proliferation. In addition, silencing PCAT1 could increase the expression of miR-129-5p and decrease the expression of HMGB1. PCAT1 was overexpressed in GSCs and played a facilitating role in radiation resistance.

Calcitriol enhances 5-aminolevulinic acid-induced fluorescence and the effect of photodynamic therapy in human glioma.

BACKGROUND: Glioma recurrence frequently occurs close to the marginal area of the surgical cavity as a result of residual infiltrating glioma cells. Fluorescence-guided surgery with 5-aminolevulinic acid (ALA) for resection of gliomas has been used as an effective therapeutic approach to discriminate malignant tissue from brain tissue and to facilitate patient prognosis. ALA-based photodynamic therapy is an effective adjuvant treatment modality for gliomas. However, insufficient protoporphyrin IX (PpIX) accumulation may limit the applicability of fluorescence-guided resection and photodynamic therapy in the marginal areas of gliomas. METHODS: To be able to understand how to overcome these issues, human glioma cells and normal astrocytes were used as the model system. Glioma cells and astrocytes were preconditioned with calcitriol for 48 hours and then incubated with ALA. Changes in ALA-induced PpIX fluorescence and cell survival after light exposure were assessed. Furthermore, expression of porphyrin synthetic enzymes in pretreated glioma cells was analyzed. RESULTS: Calcitriol can be administered prior to ALA as a non-toxic preconditioning regimen to significantly enhance ALA-induced PpIX levels and fluorescence. This increase in PpIX level was detected preferentially in glioma versus normal cells. Also, calcitriol pretreated glioma cells exhibited increased cell death following ALA-based photodynamic therapy. Furthermore, mechanistic studies documented that expression of the porphyrin synthesis enzymes coproporphyrinogen oxidase was increased by calcitriol at the mRNA level. CONCLUSION: We demonstrated for the first time a simple, non-toxic and highly effective preconditioning regimen to selectively enhance PpIX fluorescence and the response of ALA-PDT in glioma cells. This finding suggests that the combined treatment of glioma cells with calcitriol plus ALA may provide an effective and selective therapeutic modality to enhance ALA-induced PpIX fluorescent quality for improving discrimination of tumor tissue and PDT efficacy.

Low-dose arsenic trioxide enhances 5-aminolevulinic acid-induced PpIX accumulation and efficacy of photodynamic therapy in human glioma.

Among glioma treatment strategies, 5-aminolevulinic acid (5-ALA)-based fluorescence-guided resection (FGR) and photodynamic therapy (PDT) have been used as effective novel approaches against malignant glioma. However, insufficient intracellular protoporphyrin IX (PpIX) accumulation limits the application of FGR and PDT in the marginal areas of gliomas. To overcome these issues, we assessed the intracellular levels of PpIX in human glioma cell lines and rat cortical astrocytes pretreated with 0.1µM arsenic trioxide (ATO). Apoptosis and cell viability after PDT were evaluated using Annexin V-FITC apoptosis detection kit and MTT assay, respectively. In order to find out the possible mechanism, we investigated the expression of the key enzymes in the heme biosynthesis pathway, which regulates porphyrin synthesis in glioma cells. Our findings showed that the 5-ALA-induced PpIX accumulation in glioma cell lines pretreated with 0.1µM ATO was increased relative to the control groups. No changes in fluorescence intensity were detected in the rat cortical astrocytes pretreated using the same ATO concentration. Apoptosis following PDT in glioma cells pretreated with 0.1µM ATO were significantly higher than in control groups, especially late apoptotic cells, while the cell viability was decreased. The expression of CPOX was upregulated in glioma cells after pretreatment with 0.1µM ATO. We concluded that ATO was a potential optional approach in enhancing intracellular PpIX accumulation and improving the benefits of 5-ALA-induced FGR and PDT in glioma.

Harmine hydrochloride inhibits Akt phosphorylation and depletes the pool of cancer stem-like cells of glioblastoma.

Harmine hydrochloride (Har-hc), a derivative from Harmine which is a natural extractive from plants, has been considered for treatment of kinds of cancers and cerebral diseases. In this study, we found that Har-hc clearly decreased cell viability, induced apoptosis and inhibited Akt phosphorylation in glioblastoma cell lines. Moreover, Har-hc had the ability to inhibit self-renewal and promote differentiation of glioblastoma stem like cells (GSLCs) accompanied by inhibition of Akt phosphorylation. Especially, we demonstrated that Har-hc inhibited neurosphere formation of human primary GSLCs. In vivo test also confirmed Har-hc decreased the tumorigenicity of GSLCs. Thus we conclude that Har-hc has potent anti-cancer effects in glioblastoma cells, which is at least partially via inhibition of Akt phosphorylation. Administration of Har-hc may act as a new approach to glioblastoma treatment.