Blok L J, Chang G T, Steenbeek-Slotboom M, van Weerden W M, Swarts H G, De Pont J J, van Steenbrugge G J, Brinkmann A O
Department of Endocrinology & Reproduction, Erasmus University Rotterdam, The Netherlands.
Br J Cancer. 1999 Sep;81(1):28-36. doi: 10.1038/sj.bjc.6690647.
The beta 1-subunit of Na+,K+-ATPase was isolated and identified as an androgen down-regulated gene. Expression was observed at high levels in androgen-independent as compared to androgen-dependent (responsive) human prostate cancer cell lines and xenografts when grown in the presence of androgens. Down-regulation of the beta 1-subunit was initiated at concentrations between 0.01 nM and 0.03 nM of the synthetic androgen R1881 after relatively long incubation times (> 24 h). Using polyclonal antibodies, the concentration of beta 1-subunit protein, but not of the alpha 1-subunit protein, was markedly reduced in androgen-dependent human prostate cancer cells (LNCaP-FGC) cultured in the presence of androgens. In line with these observations it was found that the protein expression of total Na+,K+-ATPase in the membrane (measured by 3H-ouabain binding) was also markedly decreased. The main function of Na+,K+-ATPase is to maintain sodium and potassium homeostasis in animal cells. The resulting electrochemical gradient is facilitative for transport of several compounds over the cell membrane (for example cisplatin, a chemotherapeutic agent experimentally used in the treatment of hormone-refractory prostate cancer). Here we observed that a ouabain-induced decrease of Na+,K+-ATPase activity in LNCaP-FGC cells results in reduced sensitivity of these cells to cisplatin-treatment. Surprisingly, androgen-induced decrease of Na+,K+-ATPase expression, did not result in significant protection against the chemotherapeutic agent.
Na⁺,K⁺-ATP酶的β1亚基被分离出来，并被鉴定为一种雄激素下调基因。与雄激素依赖（有反应）的人前列腺癌细胞系和异种移植瘤相比，当在雄激素存在的情况下生长时，在雄激素非依赖的细胞系和异种移植瘤中观察到该基因的高水平表达。在相对较长的孵育时间（>24小时）后，合成雄激素R1881浓度在0.01 nM至0.03 nM之间时，β1亚基开始下调。使用多克隆抗体发现，在雄激素存在的情况下培养的雄激素依赖的人前列腺癌细胞（LNCaP-FGC）中，β1亚基蛋白的浓度显著降低，而α1亚基蛋白的浓度未降低。与这些观察结果一致，发现膜中总Na⁺,K⁺-ATP酶的蛋白表达（通过³H-哇巴因结合测量）也显著降低。Na⁺,K⁺-ATP酶的主要功能是维持动物细胞内钠和钾的稳态。由此产生的电化学梯度有利于几种化合物跨细胞膜运输（例如顺铂，一种实验性用于治疗激素难治性前列腺癌的化疗药物）。在这里，我们观察到哇巴因诱导的LNCaP-FGC细胞中Na⁺,K⁺-ATP酶活性降低导致这些细胞对顺铂治疗的敏感性降低。令人惊讶的是，雄激素诱导的Na⁺,K⁺-ATP酶表达降低并未导致对化疗药物的显著保护作用。
