Fluorescence spectroscopy for detection of malignancy: H-ras overexpressing fibroblasts as a model

Autofluorescence from intracellular chromophores upon illumination of cells by monochromatic light has been studied towards the development of novel noninvasive and sensitive technology for the early detection of cancer. To investigate the relationship between biochemical and morphological changes underlying malignant disease and resulting fluorescence spectra, an in vitro model system of a paired normal and malignant murine fibroblasts cell lines, differing in cancer-associated H-ras expression was employed. A comparison of fluorescence excitation and emission spectra of proliferative cells revealed that fluorescence intensity of malignant cells was significantly less than that of normal cells upon excitation at 290 nm. Fluorescence of both cell lines decreased with decreasing cell concentration, but at each concentration, normal cells had higher fluorescence intensity than malignant cells. Similar differences between the cell lines were observed when brought to quiescence or at stationary phase. Results suggested that the chromophore contributing most significantly to these spectra is tryptophan and its moieties in proteins. This model system demonstrates the specific contribution of H-ras to subcellular chromophores, resulting in a significant difference in their autofluorescence intensity, and implies the potential use of the technique for cancer detection. This model system is potent for analysis of the contribution of other oncogenes and their combinations towards spectral detection of cancer.