The invasive/metastatic potential of
cancer cells is an important factor in
tumor progression. The redox ratios obtained from ratios of the endogenous fluorescent signals of
NADH and
FAD, can effectively respond to the alteration of
cancer cells in its mitochondrial energy metabolism. It has been shown previously that the redox ratios may predict the metastatic potential of
cancer mouse xenografts. In this report, we aimed to investigate the metabolic state represented by the redox ratios of
cancer cells in vitro. Fluorescence microscopic imaging technology was used to observe the changes of the endogenous fluorescence signals of
NADH and
FAD in the energy metabolism pathways. We measured the redox ratios (
FAD/
NADH) of
breast cancer cell lines MDA-MB-231, MDA-MB-468, MCF-7, and SKBR3. We found that the more invasive
cancer cells have higher
FAD/
NADH ratios, largely consistent with previous studies on
breast cancer xenografts. Furthermore, by comparing the fluorescence signals of the
breast cancer cells under different nutritional environments including
starvation and addition of
glutamine,
pyruvate and
lactate, we found that the redox ratios still effectively distinguished the highly invasive MDA-MB-231 cells from less invasive MCF-7 cells. These preliminary data suggest that the redox ratio may potentially provide a new index to stratefy
breast cancer with different degrees of aggressiveness, which could have significance for the diagnosis and treatment of
breast cancer.