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

Department of Medicine, Division of Medical Oncology, Duke University Medical Center and Department of Biomedical Engineering, Fitzpatrick Institute for Photonics, Duke University, Durham, NC 27710, USA.
Cancer Research (Impact Factor: 9.33). 06/2010; 70(11):4759-66. DOI: 10.1158/0008-5472.CAN-09-2572
Source: PubMed


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.

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    • "The corrected spectra were fitted using the fluorescence spectra (excitation at 377 nm) of endogenous tissue fluorophores [collagen, elastin, nicotinamide adenine dinucleotide (NADH), and flavin adenine dinucleotid (FAD)] as a priori knowledge . The optical oxidation-reduction (redox) ratio, which is linked to the metabolic state of the tissue, was defined as NADH/(NADH +FAD) [41] [42]. Because collagen and elastin have almost identical fluorescence spectra, estimated amounts of collagen and elastin were combined as collagen + elastin. "
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    • "Lower concentrations of NADH and higher concentrations of FAD were observed in tumor tissue compared lung parenchyma, which means a decreased optical redox ratio in tumor. For epithelial cancer it has been found that this ratio increases for tumor cells [32] [38] as well as for primary human mammary epithelial cell lines [31]. In this ex vivo study we found a decrease in optical redox ratio. "
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