Department of Urology, Chang Gung Memorial Hospital, Kwei-Shan, Tao-Yuan, Taiwan.
J Mol Endocrinol. 2013 Jun 29;51(1):131-41. doi: 10.1530/JME-13-0090. Print 2013.
Hypoxia induces metabolic alteration in cancer cells by stabilizing hypoxia-inducible factor 1α (HIF-1α (HIF1A)), which regulates the bioenergetic genes of glycolysis and lipid metabolic pathways. However, the target genes of hypoxia-induced metabolic alterations in the prostate remain uncertain. Mitochondrial aconitase (mACON) (ACONM) is an enzyme that is central to carbohydrate and energy metabolism and is responsible for the interconversion of citrate to isocitrate as part of the citric acid cycle in the human prostate. We evaluated the effects of the molecular mechanisms of hypoxia on mACON gene expression in PC-3 and LNCaP human prostate carcinoma cells. Immunoblotting assays revealed that hypoxia modulated mACON and lactate dehydrogenase A (LDHA) protein expression, while these effects were attenuated when HIF-1α was knocked down. Hypoxia induced fatty acid synthase (FASN) in PC-3 cells while hypoxia blocked FASN gene expression in LNCaP cells after 24-h incubation. Results of real-time RT-qPCR, immunoblotting, and transient gene expression assays revealed that hypoxia treatment or co-transfection with HIF-1α expression vector enhanced gene expression of mACON, implying that hypoxia modulated mACON at the transcriptional level. Hypoxia-induced mACON promoter activity is dependent on the DNA fragment located at -1013 to -842 upstream of the translation initiation site. l-mimosine, an iron chelator, stabilized HIF-1α but downregulated mACON gene expression, suggesting that iron chelation blocked the hypoxia-induced mACON gene expression. These results suggest that hypoxia dysregulates the expressions of LDHA, FASN, and mACON genes, and the hypoxia-induced mACON gene expression is via the HIF-1α-dependent and iron-dependent pathways in prostate carcinoma cells.
缺氧通过稳定缺氧诱导因子 1α（HIF-1α（HIF1A））来诱导癌细胞的代谢改变，HIF-1α 调节糖酵解和脂质代谢途径的生物能基因。然而，前列腺中缺氧诱导代谢改变的靶基因仍不确定。线粒体顺乌头酸酶（mACON）（ACONM）是一种在碳水化合物和能量代谢中起核心作用的酶，负责柠檬酸转化为异柠檬酸，作为柠檬酸循环的一部分在人类前列腺中进行。我们评估了缺氧对 PC-3 和 LNCaP 人前列腺癌细胞中 mACON 基因表达的分子机制的影响。免疫印迹分析显示，缺氧调节 mACON 和乳酸脱氢酶 A（LDHA）蛋白表达，而当 HIF-1α 被敲低时，这些作用会减弱。缺氧诱导 PC-3 细胞中的脂肪酸合酶（FASN），而缺氧在 24 小时孵育后阻断 LNCaP 细胞中 FASN 基因的表达。实时 RT-qPCR、免疫印迹和瞬时基因表达分析的结果表明，缺氧处理或与 HIF-1α 表达载体共转染增强了 mACON 的基因表达，表明缺氧在转录水平上调节 mACON。缺氧诱导的 mACON 启动子活性依赖于翻译起始位点上游-1013 至-842 的 DNA 片段。l-金雀异黄素，一种铁螯合剂，稳定 HIF-1α，但下调 mACON 基因表达，表明铁螯合阻断了缺氧诱导的 mACON 基因表达。这些结果表明，缺氧失调调节 LDHA、FASN 和 mACON 基因的表达，并且前列腺癌细胞中缺氧诱导的 mACON 基因表达是通过 HIF-1α 依赖性和铁依赖性途径进行的。
