New marker of tumor cell death revealed by ATR-FTIR spectroscopy

Fourier transform infrared spectroscopy in attenuated total reflection can be used to discriminate the necrotic from the apoptotic cell death in a tumoral T cell line irradiated by a UV source able to induce both apoptosis and necrosis. Using Jurkat cells as the model system, significant spectral differences in the irradiated cells vs. time were observed in the lipid–proteins ratio absorbance band at 1,397 cm⁻¹ and in lactic acid IR band at 1,122 cm⁻¹; these spectral features are inversely correlated with the percentage of apoptotic cells assessed by flow cytometry. From the analysis of second derivatives in the IR spectral region between 1,800 and 900 cm⁻¹, we have detected two significant spectral changes: the first centered at 1,621 cm⁻¹ by analyzing the components of the amide I band and the second centered at 1,069 cm⁻¹ due to C–O stretching vibration of the DNA backbone sensitive to the dehydrated state of DNA; these identified differences in the intracellular biomolecules have been allowed to monitor the necrotic process. The variations in the spectral data set have been identified by the Kruskal–Wallis test and confirmed by the hierarchical cluster analysis.