Background: Solid epithelial tumors like breast cancer are the most frequent malignancy in women. Circulating tumor cells (CTCs) are frequently released from hypoxic areas into the blood, where CTCs face elevated oxygen concentrations. This reoxygenation might challenge the use of CTCs for liquid biopsy. Methods: We modeled this situation in vitro using the breast cancer cell lines—MCF-7, MDA-MB-468, MDA-MB-231—and the cell line BC-M1 established from DTCs in the bone marrow. Cells were cultured under hypoxia, followed by a reoxygenation pulse for 4 h, reflecting the circulation time of CTCs. Analyzed were gene products like EGFR, ErbB-2, EpCAM, PD-L1 on mRNA and protein level. Results: mRNAs of erbb2 or pdl1 and protein levels of PD-L1 displayed significant changes, whereas ErbB-2 protein levels remained constant. The strongest discrepancy between protein and mRNA levels under hypoxia was observed for EGFR, supporting the idea of cap-independent translation of egfr mRNA. Analyses of the phosphorylation of AKT, Erk 1/2, and Stat3 revealed strong alterations after reoxygenation. Conclusions: CTCs reaching secondary sites faster than reoxygenation could alter the mRNA and protein levels in the cells. CTC and DTC with high PD-L1 levels might become quiescent under hypoxia but were easily reactivated by reoxygenation.

中文翻译：

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进入血液后对缺氧肿瘤细胞中mRNA和蛋白质水平的复氧作用的体外建模。

背景：实体上皮肿瘤（如乳腺癌）是女性中最常见的恶性肿瘤。循环肿瘤细胞（CTC）通常从低氧区域释放到血液中，在血液中CTC面临着较高的氧气浓度。这种复氧可能会挑战使用CTC进行液体活检。方法：我们使用乳腺癌细胞系MCF-7，MDA-MB-468，MDA-MB-231和从骨髓DTC建立的BC-M1细胞系对这种情况进行了体外建模。在缺氧条件下培养细胞，然后再充氧脉冲4 h，反映了CTC的循环时间。分析了mRNA和蛋白质水平上的EGFR，ErbB-2，EpCAM，PD-L1等基因产物。结果：erbb2或pdl1的mRNAPD-L1的蛋白质水平显示出显着变化，而ErbB-2的蛋白质水平保持恒定。在低氧条件下，EGFR的蛋白质和mRNA水平之间存在最大差异，这支持了egfr mRNA的不依赖帽的翻译的想法。AKT，Erk 1/2和Stat3的磷酸化分析显示复氧后发生了强烈的变化。结论：四氯化碳到达次要位置的速度比复氧更快，这可能会改变细胞中的mRNA和蛋白质水平。高PD-L1水平的CTC和DTC在缺氧条件下可能会变为静止状态，但很容易被复氧激活。