Mackenzie Cancer Research Group, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand.
Fianostics GmbH, Technologie- und Forschungszentrum, Wiener Neustadt, Austria.
Cell Physiol Biochem. 2021 Oct 2;55(5):553-568. doi: 10.33594/000000435.
BACKGROUND/AIMS: Maintenance of whole-body ascorbate levels and distribution is mediated via sodium-dependent vitamin C transporters (SVCTs). The kidney is one of a few organs that express both SVCT1 and SVCT2. Recent evidence suggests that accumulation of ascorbate may be different in tumour compared to normal tissue, but data on SVCT levels in tumours is sparse.
The role of the two SVCT isoforms in ascorbate uptake in renal cell carcinoma (RCC) was investigated in vitro and in clinical samples. In three human RCC cell lines, we investigated SVCT protein levels and cellular location in response to ascorbate supplementation and withdrawal. In clinical RCC samples (n=114), SVCT patterns of staining and protein levels were analysed and compared to ascorbate levels.
In cell culture, transporter levels and cellular location were not modified by ascorbate availability at any time up to 8h, although basal SVCT2 levels governed maximal ascorbate accumulation. In clinical samples, SVCT1 protein levels in papillary RCC (pRCC) were similar to matched normal renal cortex, but were increased in clear-cell RCC (ccRCC). Native SVCT2 (72 kDa) was significantly decreased in both pRCC and ccRCC tissues compared to cortex (p<0.01), whereas a modified form of SVCT2 (100 kDa) was significantly increased (p<0.001). There was no association between the transporters (SVCT1, native or modified SVCT2) and ascorbate concentrations in either normal or tumour tissues. SVCT1 and SVCT2 displayed diffuse cytoplasmic staining in both pRCC and ccRCC tumour cells, with cortex showing distinct membrane staining for SVCT1.
We observed a re-distribution of ascorbate transporters in tumour tissue compared to normal cortex and a shift from native to modified SVCT2 in cell culture and clinical samples. Data presented here show that SVCT protein levels do not appear to predict intracellular ascorbate accumulation in RCC.
背景/目的：全身抗坏血酸水平和分布的维持是通过钠依赖性维生素 C 转运体（SVCTs）介导的。肾脏是表达 SVCT1 和 SVCT2 的少数器官之一。最近的证据表明，与正常组织相比，肿瘤中抗坏血酸的积累可能不同，但关于肿瘤中 SVCT 水平的数据很少。
我们在体外和临床样本中研究了两种 SVCT 同工型在肾细胞癌（RCC）中摄取抗坏血酸的作用。在三种人 RCC 细胞系中，我们研究了 SVCT 蛋白水平和细胞内位置对补充和撤回抗坏血酸的反应。在临床 RCC 样本（n=114）中，分析了 SVCT 染色模式和蛋白水平，并与抗坏血酸水平进行了比较。
在细胞培养中，无论在 8 小时内抗坏血酸的供应如何，转运体水平和细胞内位置都不会改变，尽管基础 SVCT2 水平决定了最大的抗坏血酸积累。在临床样本中，乳头状 RCC（pRCC）的 SVCT1 蛋白水平与匹配的正常肾皮质相似，但在透明细胞 RCC（ccRCC）中增加。与皮质相比，pRCC 和 ccRCC 组织中的天然 SVCT2（72 kDa）显著降低（p<0.01），而修饰形式的 SVCT2（100 kDa）显著增加（p<0.001）。在正常或肿瘤组织中，转运体（SVCT1、天然或修饰的 SVCT2）与抗坏血酸浓度之间均无相关性。SVCT1 和 SVCT2 在 pRCC 和 ccRCC 肿瘤细胞中均显示弥漫性细胞质染色，而皮质中 SVCT1 显示出明显的膜染色。
与正常皮质相比，我们观察到肿瘤组织中抗坏血酸转运体的重新分布，以及细胞培养和临床样本中从天然 SVCT2 向修饰的 SVCT2 的转变。这里提供的数据表明，SVCT 蛋白水平似乎不能预测 RCC 中细胞内抗坏血酸的积累。
