Optical Metabolic Imaging of Treatment Response in Human Head and Neck Squamous Cell Carcinoma

Abstract

Optical metabolic imaging measures fluorescence intensity and lifetimes from metabolic cofactors nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD). These molecular level measurements provide unique biomarkers for early cellular responses to cancer treatments. Head and neck squamous cell carcinoma (HNSCC) is an attractive target for optical imaging because of easy access to the site using fiber optic probes. Two HNSCC cell lines, SCC25 and SCC61, were treated with Cetuximab (anti-EGFR antibody), BGT226 (PI3K/mTOR inhibitor), or cisplatin (chemotherapy) for 24 hours. Results show increased redox ratio, NADH α1 (contribution from free NADH), and FAD α1 (contribution from protein-bound FAD) for malignant cells compared with the nonmalignant cell line OKF6 (p<0.05). In SCC25 and SCC61 cells, the redox ratio is unaffected by cetuximab treatment and decreases with BGT226 and cisplatin treatment (p<0.05), and these results agree with standard measurements of proliferation rates after treatment. For SCC25, NADH α1 is reduced with BGT226 and cisplatin treatment. For SCC61, NADH α1 is reduced with cetuximab, BGT226, and cisplatin treatment. Trends in NADH α1 are statistically similar to changes in standard measurements of glycolytic rates after treatment. FAD α1 is reduced with cisplatin treatment (p<0.05). These shifts in optical endpoints reflect early metabolic changes induced by drug treatment. Overall, these results indicate that optical metabolic imaging has potential to detect early response to cancer treatment in HNSCC, enabling optimal treatment regimens and improved patient outcomes.

Metabolic Imaging in the Study of Oncological Processes (Review)

“…This decrease was caused by transition to more glycolytic metabolism. It was demonstrated on oral cancer cells (SCC25 and SCC61) in vitro that NADH/FAD redox ratio decreased after treatment of cells with Cisplatin [74]. Similar results were obtained on bladder cancer cell line (Т24).…”

“…For example, decreased percentage reviews contribution of bound NADH and FAD, as compared to normal epithelial cells, was revealed on head and neck cancer cell cultures SCC25 and SCC61 [74]. The same work demonstrates increased contribution of bound NADH and FAD after treatment with chemotherapeutic agents Cisplatin, Cetuximab and BGT226.…”

Autofluorescence imaging captures heterogeneous drug response differences between 2D and 3D breast cancer cultures

“…An instrument response function (IRF) was measured using the second-harmonic generated signal from a urea crystal, then deconvolved from the acquired sample decays. The timeresolved data was fit to a two-component exponential decay as described in previously published work, to model the distinct short and long fluorescence lifetimes of free and protein-bound NAD(P)H and FAD [13,14,16]. The fit model is I(t) = α 1 exp -t/τ 1 + α 2 exp -t/τ 2 + C, where I(t) is the time-resolved fluorescence intensity following the excitation pulse from the laser, α 1 and α 2 denote the relative contributions of the short and long lifetime components to the overall decay, and τ 1 and τ 2 are the short and long lifetime values.…”

“…NAD(P)H and FAD are autofluorescent metabolic co-enzymes. The ratio of the fluorescence intensities of NAD(P)H to FAD is the "optical redox ratio," which is sensitive to malignancy, tumor aggressiveness, and drug response [12][13][14][15][16][17][18]. In fact, changes in the redox ratio induced by anti-cancer drugs predict in vivo tumor response long before changes in tumor volume can be measured [15].…”

Advances and challenges in label-free nonlinear optical imaging using two-photon excitation fluorescence and second harmonic generation for cancer research

“…Error bars indicate calculated standard deviations [107]. [108] found redox ratio calculated inversely as NADH/FAD to be increased in cancerous colonic biopsies and malignant cell lines respectively. In vivo studies conducted by Walsh et al in mouse xenograft models for breast cancer [109] and Edward et al in oral cancer models in hamsters [90] also showed similar findings.…”