2D和3D培养肺细胞释放VOCs的质谱检测比较研究

Comparative Study on the Mass Spectrometric Detection of VOCs Released by 2D and 3D Cultured Lung Cells

  • 摘要: 挥发性有机物(volatile organic compounds,VOCs)作为一种潜在的癌细胞标志物被广泛研究。目前,体外细胞多采用二维(two-dimensional,2D)贴壁培养方式,这与体内肿瘤细胞呈三维结构存在差别。本实验分别以肺癌细胞A549和肺上皮细胞BEAS-2B为例,构建三维(three-dimensional,3D)培养模型,并以2D模型和培养基作为对照,利用固相微萃取气相色谱-质谱(solid phase microextraction-gas chromatography-mass spectrometry,SPME-GC-MS)法检测细胞释放的VOCs。通过非靶向统计分析细胞在2D和3D培养中释放的差异性VOCs,其中A549细胞有4种(乙酸、1-吡咯啉、4-甲基庚烷、2,4-二甲基-1-庚烯),BEAS-2B细胞也有4种(乙醇、1-吡咯啉、4-甲基庚烷、2,4-二甲基-1-庚烯)。与2D模型相比,这些VOCs在3D模型中的释放量增加了2.11~12.81倍。此外,还讨论了差异性VOCs可能的生化来源以及在2D/3D模型中释放量差异的可能原因。本工作证明了3D培养在体外细胞VOCs检测方面具有广阔的应用前景,有望成为癌症标志物筛查有价值的研究平台。

     

    Abstract: Volatile organic compounds (VOCs) have been widely studied as potential biomarkers of cancer cells. Currently, in vitro cells are mostly cultured in two-dimensional (2D) adherent mode, which is different from in vivo tumor cells with three-dimensional structures. Tumor cell spheres cultured in three-dimensional mode have many similar characteristics to those of in vivo tumors, such as: 1) the structure of cell spheres is divided into proliferative, quiescent, and hypoxic zones; 2) the extracellular matrix deposited in the cell spheres not only increases the density of the spheres but also affects the tumor progression by intercellular interactions. In addition, VOCs detection is mainly accomplished by gas chromatography-mass spectrometry (GC-MS) combined with solid-phase microextraction (SPME), which permits both qualitative and quantitative analysis of VOCs. In this present work, lung cancer cells A549 and lung epithelial cells BEAS-2B were respectively taken as examples to construct three-dimensional (3D) culture models, and 2D models and culture media were used as controls. The VOCs released from cells were detected by SPME-GC-MS. Totally, 163 VOC chromatographic peaks were included in the statistical analyses using an untargeted strategy. Based on orthogonal partial least squares discriminant analysis (OPLS-DA) with the combined criteria of Mann-Whitney U test (p<0.05) and fold change (FC>2), differential VOCs released by cells in 2D and 3D culture modes were screened out. There were four VOCs of acetic acid, 1-pyrroline, 4-methylheptane and 2,4-dimethyl-1-heptene released at differential levels from A549 cells cultured under 2D and 3D modes, and four VOCs of ethanol, 1-pyrroline, 4-methylheptane and 2,4-dimethyl-1-heptene released at various amounts from BEAS-2B cells cultured under 2D and 3D modes, respectively. In comparison to 2D models, 3D models released 2.11 to 12.81 times more of these VOCs. Afterwards, the possible biochemical sources of the differentially released VOCs and the possible mechanisms for the differences in the releases of VOCs in the 2D/3D models were discussed. These differentially released VOCs have been reported to be potential markers in lung cancer cells, liver cancer cells, and other biological samples in previous studies. In addition, compared to 2D models, 3D models can better simulate tumor growth in vivo as well as cellular microenvironments, including the creation of reactive oxygen species (ROS) and extracellular matrix deposition. These physiological microenvironments may promote the release of cellularly differential VOCs. In this paper, by constructing 3D cell models and analyzing differential changes in cellular VOCs, it was proved that 3D culture has a broad application prospect in the detection of cellular VOCs in vitro, and is expected to be a valuable research platform for cancer biomarker screening.

     

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