Endogenous fluorescence of normal and malignant fibroblast cultures

Light-induced Fluorescence (LIF) technique is based on fluorescence emitted from intracellular chromophores upon illumination of cells by monochromatic light. We compared LIF emitted from a pair of normal and malignant murine cell lines, differing in H-ras expression. The malignant cells fluoresced significantly less than the normal cells, upon excitation at 290±10 nm. For both cell types, fluorescence decreased with decreasing cell concentration, but at each concentration, the normal cells fluoresced more than the malignant cells. The effect of viability and metabolic stage of the cells on this pattern was compared. The difference among the cells was not due to a difference in protein or DNA content. Thus, this model system demonstrates the specific contribution of H-ras to sub-cellular chromophores, resulting in a significant difference in their autofluorescence intensity, while measuring both emission and excitation scans. This study suggests a potential use of the LIF technique to distinguish between normal and malignant cells and tissues.