Studies of Secondary Melanoma on C57BL/6J Mouse Liver Using 1H NMR Metabolomics.

Ju Feng,Jian Hu,Sarah Burton,Nancy Isern

doi:10.3390/metabo3041011

Abstract

NMR metabolomics, consisting of solid state high resolution magic angle spinning (HR-MAS) 1H-NMR, liquid state high resolution 1H-NMR, and principal components analysis (PCA) has been used to study secondary metastatic B16-F10 melanoma in C57BL/6J mouse liver. The melanoma group can be differentiated from its control group by PCA analysis of the estimates of absolute concentrations from liquid state 1H-NMR spectra on liver tissue extracts or by the estimates of absolute peak intensities of metabolites from 1H HR-MAS-NMR data on intact liver tissues. In particular, we found that the estimates of absolute concentrations of glutamate, creatine, fumarate and cholesterol are elevated in the melanoma group as compared to controls, while the estimates of absolute concentrations of succinate, glycine, glucose, and the family of linear lipids including long chain fatty acids, total choline and acyl glycerol are decreased. The ratio of glycerophosphocholine (GPC) to phosphocholine (PCho) is increased by about 1.5 fold in the melanoma group, while the estimate of absolute concentration of total choline is actually lower in melanoma mice. These results suggest the following picture in secondary melanoma metastasis: Linear lipid levels are decreased by beta oxidation in the melanoma group, which contributes to an increase in the synthesis of cholesterol, and also provides an energy source input for TCA cycle. These findings suggest a link between lipid oxidation, the TCA cycle and the hypoxia-inducible factors (HIF) signal pathway in tumor metastases. Thus, this study indicates that the metabolic profile derived from NMR analysis can provide a valuable bio-signature of malignancy and cell hypoxia in metastatic melanoma.

Highlights

Metabolic changes are among the earliest cellular responses to environmental or physiological changes, and metabolomics, studying the profile of metabolites, is a powerful systems biology tool that is capable of diagnosing a disease and evaluating the efficacy of a therapy in an early stage of illness
In the 1H high resolution magic angle spinning (HR-Magic angle sample spinning (MAS)) Nuclear Magnetic Resonance (NMR) spectra on intact liver tissues, the peaks from metastatic melanoma group are visually different from those in the control group (Figure 1)
After quantifying the estimates of absolute intensities of the metabolites by wet tissue mass and analyzing both solid 1H HR-MAS NMR and liquid 1H-NMR data using principal components analysis (PCA), we found that the estimates of absolute concentration of linear lipids is much lower in the liver of secondary melanoma than that in the liver of the control

Summary

Introduction

Metabolic changes are among the earliest cellular responses to environmental or physiological changes, and metabolomics, studying the profile of metabolites, is a powerful systems biology tool that is capable of diagnosing a disease and evaluating the efficacy of a therapy in an early stage of illness. Melanoma is a malignant tumor of melanocytes [3], melanoma itself is treatable by surgical removal at early stage, i.e., in cases without metastases, but is lethal when the cancer has spread into other organs and causes the majority (75%) of deaths related to skin cancer [4]. After 3–4 weeks of inoculation of B16 cells at C57BL/6J mice, histological studies revealed the presence of malignant melanoma and metastasis in liver, lungs and spleen, showing that the B16 mouse melanoma model is an easy to reproduce in vivo model of carcinogenesis [24,25], with liver presenting a moderate stasis and a spot-type tumor proliferation similar with lung tumor proliferation. There is no way to compensate for the absence of liver function in the long term when invaded by metastatic melanoma cells, since the liver has major roles in metabolism, such as detoxification, decomposition of red blood cells, glycogen storage, plasma protein synthesis, and hormone production

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