Chemotherapy is becoming one of the main treatments for patients with non small cell lung cancer. At present, it is however impossible to assess patient response, i.e., to know what is the best chemotherapy combination for an individual patient. Thus, to have access to a tool that could allow clinicians to determine the best combination of chemotherapeutic drugs with respect to patient response is of prime importance. To this end, we have investigated the potentials of FTIR microspectroscopy as such a tool. Briefly, this technique measures the vibrational modes of the functional groups of biomolecules present in cells, after interaction of mid-infrared light with the sample. The amount of light absorbed by a vibrating bond is linearly related to concentration and the infrared spectrum reflects the global chemical composition of the studied sample. Gemcitabine (dFdC, 2’, 2’-difluorodeoxycitidine) is a pro-drug used in the treatment of patients with NSCLC. It requires three consecutive phosphorylations to become the active drug gemcitabine triphosphate. This final metabolite is incorporated into the cell DNA, inhibits DNA synthesis and subsequently halts cell replication. Infrared spectra were obtained in the reflectance mode by seeding 5 x 104 cells in 100 μL of complete media (CM) on aluminum coated slides. After 1 hour incubation at 37 °C and 5 % CO2, gemcitabine at different doses was added to cell cultures. Cells were then incubated overnight before obtaining their micro-FTIR spectra with a Nicolet Centaurus IR microscope. Spectra were recorded at a resolution of 4 cm-1 and with 64 co-additions. The main changes seen in the spectra of A549, CALU-1, and SKMES lung cancer cell lines following the addition of gemcitabine was an increase of the 1080 cm-1 peak with respect to the 1050 cm-1 peak, with a further increase in the 1080 cm-1/1050 cm-1 band ratio which was proportional to the dose of gemcitabine. The increase in the 1080 cm-1 ratio was due to the increased number of phosphate groups in DNA (1080 cm-1 peak) following the incorporation of gemcitabine triphosphate into the DNA. FTIR spectroscopy can be a useful tool to assess cell sensitivity to anticancer drugs and hence gain insight into tumor cellular response to chemotherapy. These findings are being confirmed at single cell level using synchrotron based FTIR microspectroscopy.
[Proc Amer Assoc Cancer Res, Volume 46, 2005]