INTRODUCTION The metabolic shift induced by hypoxia in cancer cells has not been explored at volatilomic level so far. The volatile organic metabolites (VOMs) constitute an important part of the metabolome and their investigation could provide us crucial aspects of hypoxia driven metabolic reconfiguration in cancer cells. OBJECTIVE To identify the altered volatilomic response induced by hypoxia in metastatic/aggressive breast cancer (BC) cells. METHODS BC cells were cultured under normoxic and hypoxic conditions and VOMs were extracted using HS-SPME approach and profiled by standard GC-MS system. Univariate and multivariate statistical approaches (p < 0.05, Log2 FC ≥ 0.58/≤ - 0.58, PC1 > 0.13/< - 0.13) were applied to select the VOMs differentially altered after hypoxic treatment. Metabolic pathway analysis was also carried out in order to identify altered metabolic pathways induced by the hypoxia in the selected BC cells. RESULTS Overall, 20 VOMs were found to be significantly altered (p < 0.05, PC1 > 0.13/< - 0.13) upon hypoxic exposure to BC cells. Further, cell line specific volatilomic alterations were extracted by comparative metabolic analysis of aggressive (MDA-MB-231) vs. non-aggressive (MCF-7) cells incubated under hypoxia and normoxia. In this case, 15 and 12 VOMs each were found to be significantly altered in aggressive cells when exposed to hypoxic and normoxic condition respectively. Out of these, 9 VOMs were found to be uniquely associated with hypoxia, 6 were specific to normoxia and 6 were found common to both the conditions. Formic acid was identified as the most prominent molecule with higher abundance levels in aggressive as compared to non-aggressive cells in both conditions. Furthermore, metabolic pathway analyses revealed that fatty acid biosynthesis and nicotinate and nicotinamide metabolism were significantly altered in aggressive as compared to non-aggressive cells in normoxia and hypoxia respectively. CONCLUSIONS Higher formate overflow was observed in aggressive cells compared to non-aggressive cells incubated under both the conditions, reinforcing its correlation with aggressive and invasive cancer type. Moreover, under hypoxia, aggressive cells preferred to be bioenergetically more efficient whereas, under normoxia, fatty acid biosynthesis was favoured when compared to non-aggressive cells.

中文翻译：

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缺氧在乳腺癌细胞中诱导的细胞外挥发性改变。

引言到目前为止，尚未在挥发性水平上研究由缺氧引起的癌细胞代谢变化。挥发性有机代谢物（VOM）构成了代谢组的重要组成部分，其研究可以为我们提供低氧驱动的癌细胞代谢重构的关键方面。目的确定低氧引起的转移性/侵袭性乳腺癌（BC）细胞中挥发性反应的改变。方法在常氧和低氧条件下培养BC细胞，采用HS-SPME方法提取VOM并通过标准GC-MS系统进行分析。采用单因素和多因素统计方法（p <0.05，Log2 FC≥0.58 /≤-0.58，PC1> 0.13 / <-0.13）选择缺氧治疗后差异性变化的VOM。还进行了代谢途径分析，以确定在选定的BC细胞中由低氧引起的代谢途径的改变。结果总体而言，发现低氧暴露于BC细胞后，有20个VOM发生了显着变化（p <0.05，PC1> 0.13 / <-0.13）。此外，通过在缺氧和常氧条件下孵育的侵袭性（MDA-MB-231）与非侵袭性（MCF-7）细胞的对比代谢分析，可以提取细胞系特异性挥发性变化。在这种情况下，当分别暴露于低氧和常氧条件下时，攻击性细胞中分别有15和12个VOM发生了明显变化。在这些中，发现9个VOM与缺氧唯一相关，其中6个对常氧具有特异性，而6个对这两种情况都相同。与两种情况下的非攻击性细胞相比，甲酸被认为是攻击性中具有最高丰度水平的最突出分子。此外，代谢途径分析显示，在正常氧和低氧状态下，与非侵袭性细胞相比，侵袭性脂肪酸的生物合成以及烟酸酯和烟酰胺代谢显着改变。结论在两种情况下，与非侵袭性细胞相比，在侵袭性细胞中观察到更高的甲酸盐溢出，从而增强了其与侵袭性和浸润性癌症类型的相关性。此外，在低氧条件下，与非侵略性细胞相比，侵袭性细胞优选在生物能上更有效，而在常氧条件下，有利于脂肪酸的生物合成。