Micro Raman spectroscopy for monitoring alterations between human skin keratinocytes HaCaT and their tumorigenic derivatives A5RT3-toward a Raman characterization of a skin carcinoma model

Raman scattering provides molecular information about biochemical differences between healthy and cancerous cells in a non-invasive and non-destructive fashion. We have monitored such changes for the human skin keratinocyte cell line HaCaT and its cancerogenic counterpart A5RT3 at 514.5 and 647 nm excitations, with either fixed-cell droplets or adherent fixed and living cells for repeated preparations over time in order to discriminate intrinsic characteristic changes. Cell droplets yielded average but rather reproducible information and helped to rapidly determine such changes. The Raman spectra show differences in the relative intensity ratios of the protein amide I band at 1656 cm(-1) and amide III bands around 1250 cm(-1) and of the phenylalanine ring mode at 1003.6 cm(-1) to the CH2 deformation band at 1448 cm(-1), which are considerably greater for HaCaT cells than A5RT3 cells. Interestingly, these observations were accompanied by severe and consistent changes in the amide III region and in the collagen marker region around 936 cm(-1), therefore providing an unambiguous evidence of protein degradation and changes in the essential amino acid phenylalanine and in the lipid components in tumorigenic A5RT3 cells. Ultimately, in light of these intrinsic changes, the present findings are consistent with the passage number of the non-tumorigenic HaCaT cells, because low pass HaCaT showed less pronounced alterations than high pass HaCaT, suggesting a correlation of tumorigenic transformation with primarily genetic instabilities in HaCaT cells. This work represents the first Raman spectroscopy discrimination of the skin carcinoma model cell lines, the non-tumorigenic HaCaT and the cancerous A5RT3 cells, addressing the importance of delineating nonspecific variations from intrinsic characteristic changes and giving a spectroscopic indication for the influence of the passage number of HaCaT cells on the tumorigenic development. Copyright (C) 2009 John Wiley & Sons, Ltd.