Quantification by SIFT-MS of acetaldehyde released by lung cells in a 3D model

Our previous studies have shown that both lung cancer cells and nonmalignant lung cells release acetaldehyde in vitro. However, data from other laboratories have produced conflicting results. Furthermore, all these studies have been carried out in 2D models which are less physiological cell growth systems when compared to 3D models. Therefore, we have carried out further work on the release of acetaldehyde by lung cells in 3D collagen hydrogels. Lung cancer cells CALU-1 and non-malignant lung cells NL20 were seeded in these hydrogels at different cell concentrations and the release of acetaldehyde was measured with the Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) technique. The data obtained showed that the amount of acetaldehyde released by both cell types grown in a 3D model is higher when compared to that of the same cells grown in 2D models. More importantly, acetaldehyde from the headspace of lung cancer cells could be measured even at a low cell concentration (105 cells per hydrogel). The differential of acetaldehyde release could be, depending on the cell concentration, more than 3 fold higher for cancer cells when compared to non-malignant lung cells. This pilot study is the first to study acetaldehyde emission from albeit only two cell types cultured in 3D scaffolds. Clearly, from such limited data the behaviour of other cell types and of tumour cells in vivo cannot be predicted with confidence. Nevertheless, this work represents another step in the search for volatile biomarkers of tumour cells, the ultimate goal of which is to exploit volatile compounds in exhaled breath and other biological fluids as biomarkers of tumours in vivo.