Resonance Raman spectroscopy at 257 nm excitation of normal and malignant cultured breast and cervical cells

The sensitivity and selectivity of UV-excited resonance Raman spectroscopy indicate that this technique may be useful in studying certain biochemical changes in cells, especially changes in DNA that occur during the developme nt of cancer. To determine whether this technique can distinguish normal fr om malignant cells, we have measured UV resonance Raman spectra at 257.26 n m excitation of suspensions of normal and malignant cultured breast and cer vical cells. Samples were excited with the use of an intracavity doubled ar gon-ion laser, and the spectra were recorded with a single grating spectrog raph and a liquid nitrogen-cooled charge-coupled device. Cell spectra obtai ned closely resembled that of DNA, with peaks around 1330, 1480, and 1580 c m(-1), due to the nucleotide bases. In addition to these, the uracil base i n RNA provides a peak at 1230 cm(-1). Strong tryptophan and tyrosine contri butions appear in the 1520-1670 cm(-1) range. The ratios of Raman spectral peaks 1480/1614 cm(-1) and 1480/1540 cm(-1), which are sensitive to the con centration of nucleic acids relative to cell proteins, were found to be hig her in malignant cells than in normal cells. Normal and malignant cells cou ld also be differentiated by using the ratio at 1330/1480 cm(-1). This diff erence may be the result of decreased hypochromism due to changes in stacki ng of the purine bases. Changes in relative amounts of RNA may also contrib ute to this ratio. The results of this pilot study indicate that there may be significant differences in the UV resonance Raman spectra of normal and cancerous cells. These differences may be related to changes in nucleotide/ protein concentrations in the cell, as well as changes in the vibrational s tructure of the nucleic acids associated with the malignant cell phenotype.