Cancer monitoring by FTIR spectroscopy.

Evidence for balanced cell growth where protein and RNA content rise at a constant relative rate with respect to DNA content with increasing grade of cancer and with malignant transformation, is derived from analysis of infrared spectra of malignant lymphoma and transformed fibroblasts within the literature. This evidence is consistent with flow cytometry derived RNA-protein relationships, and supports the biosynthetic connection proposed here between the RNA/DNA ratio as calculated from the absorbance pulse at 1121 cm(-1), and the protein/nucleic acid ratio as measured by the absorbance ratio A1650 cm(-1)/A1084 cm(-1). The present analysis is the first to explain and show evidence for a simple unifying biomolecular content theory for interdependent changes seen within the fingerprint region (900 cm(-1)-1750 cm(-1)) of the infrared spectrum of cells. Structural changes to lipids and proteins in the wavenumber range 2800 cm(-1)-3000 cm(-1), seen as increasing CH3/CH2 ratio and decreasing symmetric CH2/asymmetric CH2 ratio, are found for the first time to occur with increasing cancer (lymphoma) grade as well. These lipid/protein structural changes (2800-3000 cm(-1)) may reflect an increasing protein/lipid content ratio with malignant grade, and are the same as those shown recently for benign to malignant transformation, further supporting their cellular metabolic basis. Rising ribose content (1121 cm(-1)) is seen to correlate with rising 996 cm(-1)/966 cm(-1) ratio (another index of RNA/DNA) with increasing malignant lymphoma grade as well, The proposed spectral connections have a high signal/noise ratio with respect to clinically meaningful information. They may potentially be applied to clinical cancer grading, or in vitro cancer treatment sensitivity testing.