Lan Mei, Shi Yongquan, Sun Li, Liu Lili, Guo Xueyan, Lu Yuanyuan, Wang Jun, Liang Jie, Fan Daiming
State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
Tumour Biol. 2007;28(3):173-80. doi: 10.1159/000103011. Epub 2007 May 21.
Hypoxia-inducible factor 1alpha (HIF-1alpha) has been reported to be expressed aberrantly in gastric cancer cells. Stability and transactivation of HIF-1 were associated with the change of intracellular calcium. We hypothesized that KCl depolarization may modulate HIF-1 activity in gastric cancer cells through calcium involvement.
HIF-1alpha expression and its transcriptional activity were determined in SGC7901 gastric cancer cells treated with KCl and/or CoCl2 under normoxia. KCl induced change in the intracellular free calcium concentration and its effect on HIF-1 activity was investigated subsequently.
Exposure of SGC7901 cells to KCl (50 mM) could induce HIF-1alpha expression and its nucleus accumulation under normoxic conditions, reaching the peak at 8 and 2 h, respectively. KCl could also induce transactivation of the HIF-1 reporter gene and its target gene VEGF secretion at 8 h. Further experiments confirmed that depolarization of SGC7901 cells with KCl caused an increase in intracellular free calcium concentration. Chelation of intracellular calcium by BAPTA [1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid] induced HIF-1alpha accumulation and HIF-1 activity. However, elevation of cytosolic calcium level by ionomycin, a calcium ionophore, failed to induce HIF-1 transcriptional activity.
KCl depolarization would act through the calcium-independent pathway leading to enhanced HIF-1 transcriptional activity in gastric cancer cells.
据报道，缺氧诱导因子1α（HIF-1α）在胃癌细胞中异常表达。HIF-1的稳定性和反式激活与细胞内钙的变化有关。我们推测氯化钾去极化可能通过钙的参与来调节胃癌细胞中的HIF-1活性。
在常氧条件下，测定用氯化钾和/或氯化钴处理的SGC7901胃癌细胞中HIF-1α的表达及其转录活性。随后研究氯化钾诱导的细胞内游离钙浓度变化及其对HIF-1活性的影响。
在常氧条件下，将SGC7901细胞暴露于50 mM氯化钾可诱导HIF-1α表达及其核内积累，分别在8小时和2小时达到峰值。氯化钾在8小时时还可诱导HIF-1报告基因的反式激活及其靶基因VEGF的分泌。进一步的实验证实，用氯化钾使SGC7901细胞去极化会导致细胞内游离钙浓度增加。用BAPTA [1,2-双（2-氨基苯氧基）乙烷-N，N，N'，N'-四乙酸]螯合细胞内钙可诱导HIF-1α积累和HIF-1活性。然而，钙离子载体离子霉素升高胞质钙水平未能诱导HIF-1转录活性。
氯化钾去极化将通过不依赖钙的途径发挥作用，导致胃癌细胞中HIF-1转录活性增强。
