Detection of apoptosis on two leukemic cell lines with infrared spectroscopy

Apoptosis is a programmed cell death that plays an important role in the pathogenesis and progression of neoplasm. For the research and therapeutic purposes, it is essential to have some techniques available to reliably enumerate cell death produced by apoptosis. Since Infrared (IR) spectroscopy can simultaneously detect the changes of cellular DNA and proteins, we hypotheses that IR could be one of alternative means for detecting apoptosis. In the current study, two leukemic cells lines (CEM and K562) were exposed to VP (etoposide) and apoptosis were estimated using IR spectroscopy and flow cytometry. Our results show that there is a direct temporal relationship between the onset of apoptosis and the spectral changes on DNA and protein contents. The correlations for apoptosis predicted by IR spectra and flow cytometry were pretty good (correlation coefficients ranged from r = 0.82 ∼ 0.94). In addition, a protein marker for apoptosis from IR spectra was found that the dominant protein structure shifted from α-sheet to β-helical when the severity of apoptosis increased and this was evident in both cell lines. Therefore, our study suggest that IR spectroscopy may provide a fast and reagent free means for detecting apoptotic cell death.