| Objective: Malignant glioma is one of the most common primary malignant tumor in head and neck. Generally, surgical resection is the preferred treatment in clinic, but due to the special growth site and aggressive growth characteristics of malignant glioma, it is hard to eradicate and easy to recur postoperatively. Actually, postoperative radiotherapy and synchronization chemotherapy is widely employed in the treatment scheme either at home or abroad, which can reduce the recurrence efficiently. However, the healing rate is limited due to the resistance to the chemotherapy and radiotherapy.Recently, how to enhance the radiosensitivity of malignant tumor is becoming a hotspot. Previously, administration of some compounds in advance could enhance the radiosensitivity compared with individual radiation treatment. Meanwhile, the growth of malignant tumor was significantly suppressed. As early as in the 1960s, Adams et al. found a kind of electrophilic compounds which could increase the radiosensitivity of tumor cells in vitro and in vivo. Among these, misonidazole was a representative compound. Although the sensitization enhancement ratio(SER) amounted to 2.2, it is hard to employed in clinic on account of its huge toxicity. So the radiosensitizer with low toxicity and high efficiency is concerned by researchers. For anoxic cells occur exist commly in tumor, while anoxic cells is much less radiosensitive responded to irradiation. An ideal radiosensitizer should enhance the radiosensitivity of anoxic cells in malignant tumor and do as less as harm to normal tissue. Currently, the concept of radiosensitizer expands from the nomal hypoxic cell radiosensitizers to a complex areas covered with many aspects, such as microenvironment, angiogenesis factor, the transfer course of transmembrane induced by irradiation, DNA damage, cell cycle regulation, apoptosis, cell differentiation and so on. It includes all the kinds of chemical and biological means,which could overcome the resistance of tumor to the radiotherapy and enhance the cell-killing effect.Three compounds, artemisinin, artesunate, dihydroartemisinin as the candidates were investigated in the present study. The malignant glioma cell lines CHG-5 and U87 were selected. In order to screen out a efficient compound with good radiosensitization to the glioma cell lines, we obversed the radiosensitizing effect of objected compound on the tumor-bearing nude mice, and then explored the mechanism of radiosensitization preliminarily. In view of this, we expected to provide some experimental basis for seeking radiosensitizer with low toxicity and high efficiency.Method:①MTT assay was used to assay the IC50s of two cell lines to ART and its derivatives.②When synergized withβ-ray, we observed the radiosensitization of drugs with 20% IC50 and selected the optimal one.③Scratch test was used to observe the effect of objective drug on cell migration.④intracellular reduced GSH was measured.⑤flow cytometry was employed to assay the cell apoptosis and cell cycle distribution.⑥Immunohistochemical on cell climbing slice was detected for the expression level of CyclinD1 and proliferating cell nuclear antigen, and then the differences between the groups was compared and analyzed.⑦Tumor-bearing nude mice model by the CHG-5 cells was established to observed the radiosensitization of the objected drug in vivo.Results:①For CHG-5, the IC50 of ART, DHA and AS was 1.47 mmol/l, 0.20 mmol/l and 0.29 mmol/l, respectively. Correspondingly, the IC50 for U87 was 1.61 mmol/l, 0.25 mmol/l and 0.46 mmol/l, respectively.②Only AS could suppress the proliferation of both cell lines under the concentration of 20% IC50 when combined withβ-ray.③0.06 mmol/l AS could significantly inhibit the cell migration.④Compared with medium group, down-regulated GSH production was found after the treatment of 0.06 mmol/l AS(p<0.05).⑤Flow cytometry suggested the cell cycle was arrested in G1 phase by 0.06 mmol/l AS.⑥The Immunohistochemical results showed that,for both CyclinD1 and Proliferating cell nuclear antigen, the expression level order(from high to low) were medium, beta-ray, AS, AS plus beta-ray group.⑦AS combined with beta-ray could significantly supressed the growth of subcutaneous xenograft of nude mice. Conclusion:In summary,we found AS could enhance the radiosentivity of human glioma cell line CHG-5 toβ-ray from three artemisinin derivatives. And AS had a significant inhibition on the growth of xenograft of nude mice, which might be associated with G1 arrest. Meanwhile, decreased intracelluar GSH was involved in the radiosensitization of AS on glioma. |
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