BACKGROUND Gliomas are the most common brain cancer and survival is poor, with 11–15 months for high-grade glioblastoma patients, despite treatment. Gliomas are hypoxic tumours, which increases with tumour grade. Under hypoxia, the transcription factor hypoxia inducible factor-1 (HIF) accumulates and upregulates expression of genes involved in tumour development and progression. HIF-1 levels and activity are controlled by HIF hydroxylases which target HIF-1α for degradation and prevent co-activation. HIF hydroxylases are part of the 2-oxoglutarate (2-OG)-dependent dioxygenase enzyme family, that require 2-OG and oxygen as substrates and ascorbate and iron as co-factors. The role of ascorbate in regulating the hypoxic pathway in cancer is of interest, with previous research showing reduced HIF pathway activity with increasing tumour ascorbate levels. Brain tissue has one of the highest ascorbate levels in the body, and is one of the last to become depleted under deficiency, indicating an important role for ascorbate in this tissue. One previous study has analysed ascorbate levels in 11 human glioblastoma patients, and showed lower ascorbate in tumour tissue compared to normal brain tissue. There have been no studies investigating the relationship between ascorbate levels and the hypoxic pathway in human glioma tissues. MATERIAL AND METHODS Human glioma tissues (n = 39), obtained from the Cancer Society Tissue Bank Christchurch (ethics approval H19/163), were processed for ascorbate and hypoxic pathway proteins (HIF-1α, CA-IX, BNIP3, HKII, GLUT1 and VEGF). Ascorbate levels were quantified by HPLC-ED, and proteins were measured by Western blotting and ELISA. Spearman’s correlations were used to identify relationships between ascorbate and HIF pathway proteins. RESULTS Of the samples, 64% were GBM. Ascorbate was significantly lower in GBM compared to low-grade gliomas (p = 0.04). VEGF was significantly higher in GBM compared to astrocytomas (p = 0.01). Increased tumour ascorbate was associated with lower VEGF and CA-IX proteins. HIF-1α and BNIP3 protein were positively associated, and VEGF was positively associated with HKII and CA-IX. VEGF inversely associated with BNIP3, and CA-IX inversely associated with HKII. The hypoxic pathway score (calculated from protein levels of members of the hypoxic pathway) was reduced in tumours with higher ascorbate but this did not reach significance (p = 0.2). CONCLUSION This is the first study to show that ascorbate levels were reduced in high-grade gliomas compared to low-grade. Some members of the hypoxic pathway were associated with ascorbate levels. The overall hypoxic pathway score did not significantly correlate with ascorbate and increased numbers of samples are required to confirm any associations. Other variables, such as IDH-1 mutation status of the tumours may affect the correlation and will be analysed next.

中文翻译：

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P16.11 人脑胶质瘤组织中的维生素 C 水平和缺氧途径

背景 胶质瘤是最常见的脑癌，尽管接受了治疗，但高级别胶质母细胞瘤患者的生存期很短，为 11-15 个月。神经胶质瘤是缺氧性肿瘤，随着肿瘤分级而增加。在缺氧条件下，转录因子缺氧诱导因子-1 (HIF) 积累并上调参与肿瘤发展和进展的基因的表达。HIF-1 水平和活性由 HIF 羟化酶控制，HIF 羟化酶靶向 HIF-1α 进行降解并防止共激活。HIF 羟化酶是 2-氧戊二酸 (2-OG) 依赖性双加氧酶家族的一部分，需要 2-OG 和氧作为底物，抗坏血酸盐和铁作为辅助因子。抗坏血酸在调节癌症缺氧途径中的作用是令人感兴趣的，先前的研究表明，随着肿瘤抗坏血酸水平的增加，HIF 通路活性降低。脑组织是体内抗坏血酸水平最高的组织之一，也是最后一个因缺乏而耗尽的组织之一，这表明抗坏血酸在该组织中的重要作用。先前的一项研究分析了 11 名人类胶质母细胞瘤患者的抗坏血酸水平，并显示与正常脑组织相比，肿瘤组织中的抗坏血酸水平较低。没有研究调查抗坏血酸水平与人类神经胶质瘤组织中的缺氧途径之间的关系。材料和方法 人类神经胶质瘤组织（n = 39），从基督城癌症协会组织银行（伦理批准 H19/163）获得，用于抗坏血酸和缺氧途径蛋白（HIF-1α、CA-IX、BNIP3、HKII、GLUT1和 VEGF）。抗坏血酸水平通过 HPLC-ED 定量，蛋白质通过蛋白质印迹和 ELISA 测量。Spearman 相关性用于确定抗坏血酸和 HIF 通路蛋白之间的关系。结果 样本中，64% 为 GBM。与低级别胶质瘤相比，GBM 中的抗坏血酸显着降低 (p = 0.04)。与星形细胞瘤相比，GBM 中的 VEGF 显着升高（p = 0.01）。增加的肿瘤抗坏血酸与较低的 VEGF 和 CA-IX 蛋白有关。HIF-1α与BNIP3蛋白呈正相关，VEGF与HKII和CA-IX呈正相关。VEGF 与 BNIP3 负相关，CA-IX 与 HKII 负相关。抗坏血酸较高的肿瘤的缺氧途径评分（根据缺氧途径成员的蛋白质水平计算）降低，但这没有达到显着性（p = 0.2）。结论 这是第一项研究表明，与低级别相比，高级别胶质瘤的抗坏血酸水平降低。缺氧途径的一些成员与抗坏血酸水平有关。总体缺氧途径评分与抗坏血酸没有显着相关性，需要增加样本数量来确认任何关联。其他变量，例如肿瘤的 IDH-1 突变状态可能会影响相关性，将在接下来进行分析。