Institute for Research on Cancer and Aging, Nice, University of Nice-Sophia Antipolis, CNRS UMR7284, INSERM U1081, Centre A. Lacassagne, Nice, France.
J Cell Physiol. 2013 Sep;228(9):1854-62. doi: 10.1002/jcp.24346.
The efficacy of targeting pH disruption to induce cell death in the acidic and hypoxic tumor microenvironment continues to be assessed. Here we analyzed the impact of varying levels of hypoxia in acidic conditions on fibroblast and tumor cell survival. Across all cell lines tested, hypoxia (1% O(2)) provided protection against acidosis induced cell death compared to normoxia. Meanwhile severe hypoxia (0.1% O(2)) removed this protection and in some cases exacerbated acidosis-induced cell death. Differential survival between cell types during external acidosis correlated with their respective intracellular pH regulating capabilities. Cellular ATP measurements were conducted to determine their contribution to cell survival under these combined stresses. In general, hypoxia (1% O(2)) maintained elevated ATP levels in acidic conditions while severe hypoxia did not. To further explore this interaction we combined acidosis with ATP depletion using 2-deoxyglucose and observed an enhanced rate of cell mortality. Striking results were also observed with hypoxia providing protection against cell death in spite of a severe metabolic stress induced by a combination of acidosis and oligomycin. Finally, we demonstrated that both HIF1α and HIF2α expression were drastically reduced in hypoxic and acidic conditions indicating a sensitivity of this protein to cellular pH conditions. This knockdown of HIF expression by acidosis has implications for the development of therapies targeting the disruption of cellular pH regulation. Our results reinforce the proof of concept that acidosis and metabolic disruption affecting ATP levels could be exploited as a tumor cell killing strategy.
靶向破坏 pH 值以诱导酸性和缺氧肿瘤微环境中的细胞死亡的疗效仍在评估中。在这里，我们分析了不同程度的缺氧对酸性条件下成纤维细胞和肿瘤细胞存活的影响。在所测试的所有细胞系中，与常氧相比，缺氧（1% O(2)）为酸中毒诱导的细胞死亡提供了保护。同时，严重缺氧（0.1% O(2)）消除了这种保护作用，并在某些情况下加剧了酸中毒诱导的细胞死亡。在外部酸中毒期间，细胞类型之间的差异存活与它们各自的细胞内 pH 调节能力相关。进行细胞 ATP 测量以确定它们在这些联合应激下对细胞存活的贡献。一般来说，缺氧（1% O(2)）在酸性条件下维持高水平的 ATP，而严重缺氧则不能。为了进一步探索这种相互作用，我们使用 2-脱氧葡萄糖将酸中毒与 ATP 耗竭结合起来，观察到细胞死亡率的增加。尽管酸中毒和寡霉素联合诱导的严重代谢应激，缺氧仍能提供对细胞死亡的保护，这也产生了惊人的结果。最后，我们证明了缺氧和酸性条件下 HIF1α 和 HIF2α 的表达都明显降低，表明该蛋白对细胞 pH 条件敏感。酸中毒对 HIF 表达的这种敲低对靶向破坏细胞 pH 调节的治疗方法的发展具有重要意义。我们的研究结果强化了这样一个概念，即影响 ATP 水平的酸中毒和代谢紊乱可以被用作肿瘤细胞杀伤策略。
