Karim Aftab, McCarthy Kevin, Jawahar Ajay, Smith Donald, Willis Brian, Nanda Anil
Department of Neurosurgery, Louisiana State University Health Sciences Center in Shreveport, Shreveport, Louisiana 71130-3932, USA.
Anticancer Res. 2005 Jan-Feb;25(1B):675-9.
Glioblastoma multiforme (GBM) is a high-grade primary brain tumor that is refractory to current forms of treatment. In cell studies, the growth rate of GBM cells correlates with the level of Cyclooxygenase-2 (COX-2) enzyme expression. COX-2 has been implicated in carcinogenesis of systemic cancers. Recently, COX-2 inhibition has been shown to increase the radiosensitivity of various tumors. We wished to assess whether the expression of COX-2 is greater in radioresistant versus radiosensitive forms of GBM.
The radiosensitive (A172) and radioresistant (T98G) Glioblastoma multiforme cell lines were assayed for COX-2 expression using standard immunofluorescence histochemistry. Fluorescence readings were recorded per field. Western blot analysis was performed on both A172 and T98G GBM cell lines. The radioresistant cells were exposed to incremental doses of radiation in the presence and absence of a COX-2-selective inhibitor. Radioresistant cells were then exposed to incremental doses of COX-2-selective inhibitor at a constant dose of radiation.
The radioresistant cell line T98G had an approximate 1. 7-fold greater expression of COX-2 than did the radiosensitive cell line A172, as per immunofluorescence histochemistry. Western blot analysis confirmed this finding. Statistical analysis (Bonferroni/Dunn) showed the results to be significant (p<0.0001). The wells containing radioresistant cells exposed to incremental doses of radiation and COX-2 inhibitors appeared to have higher cell kill when compared to radiation alone. Furthermore, increasing the COX-2 inhibitor concentration yielded higher cell kill.
The results presented here show that the radioresistant GBM cell line, T98G, has a greater expression of COX-2 than does the radiosensitive GBM cell line, A172. These results suggest that: (i) COX-2 expression may serve as a marker for assessing radioresistance in GBM, (ii) COX-2 inhibition may lower the required doses of postoperative radiation, (iii) COX-2 inhibitors may have a role in radiosensitizing otherwise radioresistant forms of GBM.
多形性胶质母细胞瘤（GBM）是一种高级别原发性脑肿瘤，对目前的治疗形式具有抗性。在细胞研究中，GBM细胞的生长速率与环氧化酶-2（COX-2）酶的表达水平相关。COX-2与系统性癌症的致癌作用有关。最近，已表明COX-2抑制可增加各种肿瘤的放射敏感性。我们希望评估COX-2在GBM的放射抗性形式与放射敏感形式中表达是否更高。
使用标准免疫荧光组织化学法检测放射敏感（A172）和放射抗性（T98G）多形性胶质母细胞瘤细胞系中的COX-2表达。记录每个视野的荧光读数。对A172和T98G GBM细胞系进行蛋白质免疫印迹分析。在存在和不存在COX-2选择性抑制剂的情况下，将放射抗性细胞暴露于递增剂量的辐射。然后将放射抗性细胞在恒定辐射剂量下暴露于递增剂量的COX-2选择性抑制剂。
根据免疫荧光组织化学，放射抗性细胞系T98G的COX-2表达比放射敏感细胞系A172高约1.7倍。蛋白质免疫印迹分析证实了这一发现。统计分析（Bonferroni/Dunn）表明结果具有显著性（p<0.0001）。与单独辐射相比，含有暴露于递增剂量辐射和COX-2抑制剂的放射抗性细胞的孔似乎具有更高的细胞杀伤率。此外，增加COX-2抑制剂浓度可产生更高的细胞杀伤率。
此处呈现的结果表明，放射抗性GBM细胞系T98G的COX-2表达高于放射敏感GBM细胞系A172。这些结果表明：（i）COX-2表达可作为评估GBM放射抗性的标志物；（ii）COX-2抑制可降低术后放疗所需剂量；（iii）COX-2抑制剂可能在使原本放射抗性形式的GBM增敏方面发挥作用。
