Optical Redox Ratio Differentiates Breast Cancer Cell Lines Based on Estrogen Receptor Status

Abstract

Autofluorescence spectroscopy is a powerful imaging technique that exploits endogenous fluorophores. The endogenous fluorophores NADH and flavin adenine dinucleotide (FAD) are two of the principal electron donors and acceptors in cellular metabolism, respectively. The optical oxidation-reduction (redox) ratio is a measure of cellular metabolism and can be determined by the ratio of NADH/FAD. We hypothesized that there would be a significant difference in the optical redox ratio of normal mammary epithelial cells compared with breast tumor cell lines and that estrogen receptor (ER)–positive cells would have a higher redox ratio than ER-negative cells. To test our hypothesis, the optical redox ratio was determined by collecting the fluorescence emission for NADH and FAD via confocal microscopy. We observed a statistically significant increase in the optical redox ratio of cancer compared with normal cell lines (P < 0.05). Additionally, we observed a statistically significant increase in the optical redox ratio of ER(+) breast cancer cell lines. The level of ESR1 expression, determined by real-time PCR, directly correlated with the optical redox ratio (Pearson’s correlation coefficient = 0.8122, P = 0.0024). Furthermore, treatment with tamoxifen and ICI 182,870 statistically decreased the optical redox ratio of only ER(+) breast cancer cell lines. The results of this study raise the important possibility that fluorescence spectroscopy can be used to identify subtypes of breast cancer based on receptor status, monitor response to therapy, or potentially predict response to therapy. This source of optical contrast could be a potentially useful tool for drug screening in preclinical models.

Ex vivooptical metabolic measurements from cultured tissue reflectin vivotissue status

“…The optical redox ratio has been previously used to quantify metabolic differences among normal tissue, pre-cancerous tissue, and cancerous tumors. 1,2,26,35,36 In the current study, two epithelial depth layers were interrogated because stratified squamous epithelial tissues are known to have a gradient of cellular metabolic activity, with the basal cells being most active and the superficial cells being least active. 2,28 As shown in Fig.…”

Autofluorescence Imaging and Spectroscopy of Human Lung Cancer

“…Typically, compared with the normal tissues, the fluorescence intensity of free FAD in cancerous tissues increased, while the free and protein-bound NADH contributed less for the spectra. The optical oxidation reduction (redox) ratio is a measurement of cellular metabolism, which is defined as the ratio between NADH and FAD [41,42]. In this study, the optical redox was calculated as the ratio of NADH (free and protein-bound) to free FAD, INADH/IFAD.…”

Correlating two-photon excited fluorescence imaging of breast cancer cellular redox state with seahorse flux analysis of normalized cellular oxygen consumption

“…2,3 Since the first publication by Chance et al, 4 the ORR has been used in a broad range of applications spanning from cancer detection and diagnosis to predicting drug response to monitoring cellular function and stem cell differentiation. [5][6][7][8][9] Unlike competing quantitative techniques with which the cells have to be lyzed, [10][11][12] TPEF microscopy provides a nondestructive, real-time, and label-free method for quantifying cellular metabolism. It enables the spatial mapping of metabolic rate at the submicrometer scale with minimum interruption of normal cell function.…”