缺氧的肿瘤微环境对癌症治疗提出了重大挑战。缺氧激活的前药（如 evofosfamide）旨在特异性靶向并消除这些耐药细胞。然而，它们的有效性常常受到细胞死亡后复氧的限制。我们假设抗坏血酸的促氧化特性可用于诱导短暂缺氧，通过克服复氧来增强依福磷酰胺的功效。为了检验这一假设，我们在体外和体内研究了 MIA Paca-2 和 A549 癌细胞对抗坏血酸的敏感性。抗坏血酸在 5 mM 时诱导细胞毒性作用，这种作用可以通过内源性施用过氧化氢酶来减轻，这表明过氧化氢在其细胞毒性机制中的作用。在体外，海马实验表明，过氧化氢的产生会消耗氧气，而在稍后的时间点，由于过氧化氢的细胞毒性作用，氧气消耗量的减少会抵消这一消耗。在体内，光声成像显示亚致死水平的药理学抗坏血酸治疗在两种细胞系的肿瘤氧合中触发了复杂的多相反应。最初，抗坏血酸通过消耗氧气的反应产生过氧化氢，在几分钟内产生短暂的缺氧。最初的缺氧阶段在 150 秒左右达到峰值，然后逐渐消退。然而，在较长的时间尺度（大约 300 秒）下，抗坏血酸引发的血管舒张作用会导致血流量增加和随后的再氧合。结合腹膜内注射的亚致死水平。与单独治疗相比，抗坏血酸与 evofosfamide 联合使用可显着延长 MIA Paca-2 和 A549b 异种移植物中的肿瘤倍增时间。然而，这种改善仅在肿瘤亚群中观察到，凸显了氧合反应的复杂性。版权所有 © 2024。由 Elsevier Inc. 出版。

Hypoxic tumor microenvironments pose a significant challenge in cancer treatment. Hypoxia-activated prodrugs like evofosfamide aim to specifically target and eliminate these resistant cells. However, their effectiveness is often limited by reoxygenation after cell death. We hypothesized that ascorbate's pro-oxidant properties could be harnessed to induce transient hypoxia, enhancing the efficacy of evofosfamide by overcoming reoxygenation. To test this hypothesis, we investigated the sensitivity of MIA Paca-2 and A549 cancer cells to ascorbate in vitro and in vivo. Ascorbate induced a cytotoxic effect at 5 mM that could be alleviated by endogenous administration of catalase, suggesting a role for hydrogen peroxide in its cytotoxic mechanism. In vitro, Seahorse experiments indicated generation of hydrogen peroxide consumes oxygen, which is offset at later time points by a reduction in oxygen consumption due to hydrogen peroxide's cytotoxic effect. In vivo, photoacoustic imaging showed pharmacologic ascorbate treatment at sublethal levels triggered a complex, multi-phasic response in tumor oxygenation across both cell lines. Initially, ascorbate generated transient hypoxia within minutes through hydrogen peroxide production, via reactions that consume oxygen. This initial hypoxic phase peaked at around 150 seconds and then gradually subsided. However, at longer time scales (approximately 300 seconds) a vasodilation effect triggered by ascorbate resulted in increased blood flow and subsequent reoxygenation. Combining sublethal levels of i.p. ascorbate with evofosfamide significantly prolonged tumor doubling time in MIA Paca-2 and A549b xenografts compared to either treatment alone. This improvement, however, was only observed in a subpopulation of tumors, highlighting the complexity of the oxygenation response.Copyright © 2024. Published by Elsevier Inc.