Our previous studies have shown that both lung cancer cells and non-malignant 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 (10(5) 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.

FTIR spectra of cells on glass coverslips allows the study of the Amide I region.

The rising incidence of cancer worldwide is causing an increase in the workload in pathology departments. This, coupled with advanced analysis methodologies, supports a developing need for techniques that could identify the presence of cancer cells in cytology and tissue samples in an objective, fast, and automated way. Fourier transform infrared (FT-IR) microspectroscopy can identify cancer cells in such samples objectively. Thus, it has the potential to become another tool to help pathologists in their daily work. However, one of the main drawbacks is the use of glass substrates by pathologists. Glass absorbs IR radiation, removing important mid-IR spectral data in the fingerprint region (1800 cm−1 to 900 cm−1). In this work, we hypothesized that, using glass coverslips of differing compositions, some regions within the fingerprint area could still be analyzed. We studied three different types of cells (peripheral blood mononuclear cells, a leukemia cell line, and a lung cancer cell line) and lymph node tissue placed on four different types of glass coverslips. The data presented here show that depending of the type of glass substrate used, information within the fingerprint region down to 1350 cm−1 can be obtained. Furthermore, using principal component analysis, separation between the different cell lines was possible using both the lipid region and the fingerprint region between 1800 cm−1 and 1350 cm−1. This work represents a further step towards the application of FT-IR microspectroscopy in histopathology departments.

Raman spectroscopy has been widely used to study its possible clinical application in cancer diagnosis. However, in order to make it into clinical practice, it is important that this technique is able not only to identify cancer cells from their normal counterparts, but also from the array of cells present in human tissues. To this purpose, we used Raman spectroscopy to assess whether this technique was able to differentiate not only between lung cancer cells and lung epithelial cells but also from lung fibroblasts. Furthermore, we studied whether the differences were due to cell lineage (epithelial versus fibroblast) or to different proliferative characteristics of cells, and where in the cell compartment these differences might reside. To answer these questions we studied cell cytoplasm, cell nucleus and isolated whole cell nuclei. Our data suggests that Raman spectroscopy can differentiate between lung cancer, lung epithelial cells and lung fibroblasts. More important, it can also differentiate between 2 cells from the same lineage (fibroblast) but with one of them rendered immortal and with an increased proliferative activity. Finally, it seems that the main spectral differences reside in the cell nucleus and that the study of isolated nuclei strengthens the differences between cells.