神經膠母細胞瘤是一種具有高死亡率及復發率的惡性腫瘤。而手術、放射線及化學療法是主要治療神經膠母細胞瘤的方法。然而，這些治療方法最後常常會引起腫瘤對化學療法及放射線療法產生抗性。因此去找出神經膠母細胞瘤如何產生抗性的機制或許可以提供一個高度專一及有效的治療方法。在我們之前的研究已經知道神經膠母細胞瘤的細胞株可以從半致死劑量的放射線下存活，並且會調控Vimentin蛋白轉移到細胞核中。這些結果都顯示神經膠母細胞瘤可能藉由將細胞週期暫停在G2/M、中心體增生及上皮-間葉過渡 (epithelial-mesenchymal transition)使細胞在照過放射線後存活。而這些細胞對於太平洋紫杉醇(paclitaxel)這種常用於化學療法的細胞分裂抑制劑有高度的敏感性。
在本篇的研究當中，我們假設經過放射線前處理的腫瘤細胞會因為改變的細胞內分子的特性而使細胞對於化學療法的藥劑更敏感，而藉此可找到療效更好的治療方法。我們利用CNS-1細胞株經放射線處理後建立了三個放射線前處理的神經膠母細胞瘤的細胞株。在西方墨點法的分析下，p21、p53及γ-tubulin蛋白的表現量會隨著放射線劑量增加而上升。而Cdk2, Cdk4, Cdk1, PLK, Cdc25B and Cdc25C蛋白的表現量會先在中等放射線劑量時上升，在最高劑量時下降。而這些結果都顯示經放射線前處理的細胞會走向暫停G2/M細胞週期並伴隨著中心體增加來使細胞逃過死亡。此外，免疫組織染色的結果也顯示，在一個經放射線治療後又復發的病人檢體中，vimentin蛋白和在細胞株中的分布結果相似，會轉移到細胞核中。而有趣的是，若將CNS-1細胞經1- [4-(furo [2,3-b] quinolin-4-ylamino)phenyl]ethanone (CIL-102) 這種微管聚合的抑制劑前處理後，會增加細胞對太平洋紫杉醇的敏感性。但若是細胞先經放射線前處理後再處理CIL-102，則會降低細胞對太平洋紫杉醇的敏感性。而根據這些實驗結果我們可以下一個結論:CNS-1這株神經膠母細胞瘤的細胞株若是經過放射線或CIL-102藥物的前處理使細胞週期停在G2/M，可以增加太平洋紫杉醇對腫瘤的毒殺性。這篇研究可以提供一個結合放射線及化學療法在臨床治療的方向，在提高對於神經膠母細胞瘤的治療效果的同時也降低藥物對病人的傷害。

Gliobastoma (GBM) is a malignant cancer with high mortality and recurrence rate. Surgery, radiation and chemotherapy are common treatment modalities for GBM. However, cancer therapy may complicated by chemo/radiation-induced resistance. To detect underlying mechanisms of how GBM develop resistance may help to design a highly specific and efficient treatment regime. Our previous data showed that glioma cell lines survive sequential LD 50 radiations. Vimentin was upregulated and translocated to the nuclei. These results suggested that cell cycle G2/M arrest, centrosome amplification, and EMT may protect GBM cells from death. Furthermore, these cells were sensitized to paclitaxel (taxol) treatment, a mitotic inhibitor used in cancer chemotherapy.
In this study, we test the hypothesis that radiation resistant/ preconditioned tumor may have alerted molecular characters to make it more sensitive to adjuvant cancer treatment which might provide clues to find better methods to enhance therapeutic efficacy. We had irradiated CNS-1 cells to establish a radiation preconditioned (RP) GBM cell lines. By using Western blotting method, the p21, p53 and γ-tubulin were up-regulated in a radiation dose-dependent manner. The expression of Cdk2, Cdk4, Cdk1, PLK, Cdc25B and Cdc25C were up-regulated at low and medium irradiation dosages (4 and 8 Gy), then down-regulated at high irradiation dosage (12 Gy). These data suggested that RP cells may enter G2/M cell cycle check point arrest and along with centrosome amplification. In addition, immunohistochemical staining showed vimentin nuclear translocation in post- irradiated, recurrent GBM. Interestingly, CNS-1 cells preconditioned with CIL-102, a microtubule polymerization inhibitor that rested the cells at G2/M phase, resulted in enhanced paclitaxel toxicity by using Trypan Blue Exclusion assay. But RP cells combined treatment with paclitaxel and CIL-102 showed decreased drug toxicity. According to these results, we conclude that CNS-1 preconditioned with radiation or CIL-102 resulted in G2/M check point arrest which enhances the efficacy of paclitaxel in killing tumor. Given glioma therapy may complicated by chemo/radiation toxicity, this study may provide clues to design a therapeutic regime to enhance chemo reagent’s killing efficacy but with less toxicity to the patients.

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