Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, RJ, Brazil.
Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Rio de Janeiro 21941-590, RJ, Brazil.
Int J Mol Sci. 2021 Sep 18;22(18):10096. doi: 10.3390/ijms221810096.
According to the growth rate hypothesis (GRH), tumour cells have high inorganic phosphate (Pi) demands due to accelerated proliferation. Compared to healthy individuals, cancer patients present with a nearly 2.5-fold higher Pi serum concentration. In this work, we show that an increasing concentration of Pi had the opposite effect on Pi-transporters only in MDA-MB-231 when compared to other breast cell lines: MCF-7 or MCF10-A (non-tumoural breast cell line). Here, we show for the first time that high extracellular Pi concentration mediates ROS production in TNBC (MDA-MB-231). After a short-time exposure (1 h), Pi hyperpolarizes the mitochondrial membrane, increases mitochondrial ROS generation, impairs oxygen (O) consumption and increases PKC activity. However, after 24 h Pi-exposure, the source of HO seems to shift from mitochondria to an NADPH oxidase enzyme (NOX), through activation of PKC by HO. Exogenous-added HO modulated Pi-transporters the same way as extracellular high Pi, which could be reversed by the addition of the antioxidant N-acetylcysteine (NAC). NAC was also able to abolish Pi-induced Epithelial-mesenchymal transition (EMT), migration and adhesion of MDA-MB-231. We believe that Pi transporters support part of the energy required for the metastatic processes stimulated by Pi and trigger Pi-induced HO production as a signalling response to promote cell migration and adhesion.
根据生长率假说（GRH），由于肿瘤细胞的快速增殖，其对无机磷酸盐（Pi）的需求量很高。与健康个体相比，癌症患者的血清 Pi 浓度几乎高出 2.5 倍。在这项工作中，我们发现，与其他乳腺癌细胞系（MCF-7 或 MCF10-A）相比，Pi 转运蛋白在 MDA-MB-231 中的浓度增加仅产生相反的效果：非肿瘤性乳腺癌细胞系（MCF10-A）。在这里，我们首次表明，高细胞外 Pi 浓度可介导三阴性乳腺癌（MDA-MB-231）中的 ROS 产生。短时间暴露（1 小时）后，Pi 使线粒体膜超极化，增加线粒体 ROS 生成，损害氧（O）消耗并增加 PKC 活性。然而，在 Pi 暴露 24 小时后，HO 的来源似乎从线粒体转移到 NADPH 氧化酶（NOX），通过 HO 激活 PKC。外源性添加的 HO 以与细胞外高 Pi 相同的方式调节 Pi 转运蛋白，这可以通过添加抗氧化剂 N-乙酰半胱氨酸（NAC）来逆转。NAC 还能够消除 Pi 诱导的 MDA-MB-231 上皮-间充质转化（EMT）、迁移和黏附。我们认为，Pi 转运蛋白为 Pi 刺激的转移过程所需的部分能量提供支持，并触发 Pi 诱导的 HO 产生作为促进细胞迁移和黏附的信号反应。
