Radiobiological research over the past decades has provided evidence that cancer stem cell content and the intrinsic radiosensitivity of cancer stem cells varies between tumours, thereby affecting their radiocurability. Translation of this knowledge into predictive tests for the clinic has so far been hampered by the lack of methods to discriminate between stem cells and non-stem cells. New technologies allow isolation of cells expressing specific surface markers that are differentially expressed in tumour cell subpopulations that are enriched for cancer stem cells. Combining these techniques with functional radiobiological assays holds the potential to elucidate the role of cancer stem cells in radioresistance in individual tumours, and to use this knowledge for the development of predictive markers for optimization of radiotherapy.

Exploring the role of cancer stem cells in radioresistance.

Purpose: The antimalarial agent, artemisinin, also confers cancer-specific cytotoxic effects by reacting with ferrous iron atoms to form free radicals. Here, we investigated the radiosensitizing effects of dihydroartemisinin on glioma cells and assessed some possible mechanisms for these effects. Materials and methods: U373MG glioma cells treated with various concentrations of dihydroartemisinin plus radiation, and efficiency of radiosensitization was assessed by clonogenic survival assay. Expression and activity of antioxidant enzymes, glutathione-S-transferase (GST) were quantified by western blot and enzymatic activity analyses, respectively. Results: Dihydroartemisinin showed higher cytotoxicity in the glioma cell lines than in the liver, breast or cervical cancer cell lines. In clonogenic survival assays, treatment with dihydroartemisinin alone dose-dependently reduced the number of U373MG colonies, while treatment with dihydroartemisinin plus γ-irradiation showed far lower clonal survival than cultures treated with radiation or dihydroartemisinin alone. The radiosensitizing effect of dihydroartemisinin was blocked significantly by the free radical scavengers, NAC and TIRON, indicating association with dihydroartemisinin-induced ROS generation. In addition, the radiation-induced expression of endogenous GST was suppressed by treatment with dihydroartemisinin. The radiosensitizing effect of dihydroartemisinin was also markedly enhanced by the addition of holotransferrin Conclusion: Taken together, our results strongly suggest that dihydroartemisinin triggers production of ROS and inhibits GST activity, leading to effective and therapeutically relevant radiosensitization of human glioma cells.

Dihydroartemisinin enhances radiosensitivity of human glioma cells in vitro

Purpose: Investigation of cell migration and proliferation of human glioma cell line spheroids (CLS) and evaluation of morphology, apoptosis, and immunohistochemical expression of MIB-1, p53, and p21 of organotypic muticellular spheroids (OMS) following cisplatin (CDDP) and irradiation (RT). Material and methods: Spheroids of the GaMg glioma cell line and OMS prepared from biopsy tissue of six glioblastoma patients were used. Radiochemosensitvity (5 μg/ml CDDP followed by RT) was determined using migration and proliferation assays on CLS. In OMS, histology and immunohistochemical studies of MIB-1, p53, and p21 expression were examined 24 and 48 h following treatment. Results: Combination treatment led to a migration inhibition of 38% (CDDP 13%; RT 27%) and specific growth delay of 2.6 (CDDP 1.3; RT 2.1) in CLS. Cell cycle analysis after combination treatment showed an accumulation of cells in the G2/M phase. In OMS, apoptosis increased, cell proliferation decreased, and p53/p21 expression increased more pronounced following CDDP+RT. No morphological damage was observed. Conclusion: CDDP can lead to enhancement of the RT effect in spheroids of both human glioma cell line spheroids and biopsy spheroids from glioblastoma specimens. The exerted effect is additive rather than synergistic.

Effects of irradiation and cisplatin on human glioma spheroids: inhibition of cell proliferation and cell migration.

DTI-015 (BCNU dissolved in ethanol) utilizes solvent facilitated perfusion (SFP) for intratumoral drug delivery. A phase II clinical trial of DTI-015 and fractionated external beam radiotherapy on newly diagnosed, malignant gliomas investigated early changes in tumour physiology and metabolism, clinical outcome and safety. Pre- and post DTI-015 injection neuro-imaging included computed tomography (CT) cerebral blood flow and volume, glucose and thallium single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI). Clinical status was determined before and after DTI-015, prior to radiotherapy and 3 monthly thereafter until progression (defined by Macdonald criteria). Primary endpoint was radiographic response. Secondary endpoints were progression free (PFS) and overall survival (OS). Twelve patients were enrolled; eight glioblastoma multiforme (GBM), four anaplastic astrocytoma (AA). Three days after DTI-015 injection, mean tumour blood flow (Paired t-test; P < 0.001) and blood volume (Paired t-test; P = 0.001) were significantly reduced. There was a significant decrease in glucose utilization (Paired t-test; P < 0.001) and thallium uptake (Paired t-test; P < 0.001) at 6 days. Tumour blood volume had a sustained reduction (Paired t-test; P = 0.001) at 26 days after DTI-015. There were two serious adverse events. Two patients with AA achieved a partial response. Median PFS was 39 weeks for AA and 27 weeks for GBM; median OS for GBM was 47 weeks and 132 weeks for AA. The imaging data forms a biological basis for understanding the effects of high dose BCNU delivered intratumorally by SFP, and suggests early effects on tumour vasculature and metabolism.

Phase II trial of intratumoral BCNU injection and radiotherapy on untreated adult malignant glioma.

https://koreascience.or.kr:443/article/JAKO200811237156627.pdf

A. Allarn

Papers

1054 The correlation between fractionated TCD50 and different predictive radiobiologic parameters of nine human tumor xenografts into nude mice