Simultaneous in vivo optical quantification of key metabolic and vascular endpoints reveals tumor metabolic diversity in murine breast tumor models

Abstract

Therapeutically exploiting vascular and metabolic endpoints becomes critical to translational cancer studies because altered vascularity and deregulated metabolism are two important cancer hallmarks. The metabolic and vascular phenotypes of three sibling breast tumor lines with different metastatic potential are investigated in vivo with a newly developed quantitative spectroscopy system. All tumor lines have different metabolic and vascular characteristics compared to normal tissues, and there are strong positive correlations between metabolic (glucose uptake and mitochondrial membrane potential) and vascular (oxygen saturations and hemoglobin concentrations) parameters for metastatic (4T1) tumors but not for micrometastatic (4T07) and nonmetastatic (67NR) tumors. A longitudinal study shows that both vascular and metabolic endpoints of 4T1 tumors increased up to a specific tumor size threshold beyond which these parameters decreased. The synchronous changes between metabolic and vascular parameters, along with the strong positive correlations between these endpoints suggest that 4T1 tumors rely on strong oxidative phosphorylation in addition to glycolysis. This study illustrates the great potential of our optical technique to provide valuable dynamic information about the interplay between the metabolic and vascular status of tumors, with important implications for translational cancer investigations. K E Y W O R D Soptical spectroscopy, tumor metabolism, tumor metastasis, vascular microenvironmentInterest in metabolism and the vascular microenvironment continues to grow in a broad range of disciplines including neuroscience [1], cardiovascular biology [2] and the field of cancer research [3]. At the most basic level, lack of oxygen promotes glycolysis to allow biological systems to survive acute stress [4]. Under conditions of chronic stress, such as persistent hypoxia, biological cells can undergo long-term changes that allow their metabolism and supporting

Resolving Metabolic Heterogeneity in Experimental Models of the Tumor Microenvironment from a Stable Isotope Resolved Metabolomics Perspective

“…Nevertheless, considerable progress is being made via single cell analyses of genome, transcriptome [13,21,22,[40][41][42][43][44][45][46][47][48][49], proteome [50][51][52], and metabolome [8,[52][53][54][55][56][57]. Although spatially resolved single cell metabolism has long been studied by live cell microscopy, the number of metabolites that can be detected and quantified is very limited [58][59][60][61]. The more recent single cell metabolomics development can capture more metabolites, but it is limited to those at high abundance while there are important issues on quantitation and reproducibility yet to be resolved [55].…”

“…In addition, free versus bound concentrations of metabolites can be discriminated in cells by fluorescence lifetime imaging microscopy (FLIM) [158,194,195]. However, microscopy-based metabolic imaging requires the use of fluorescent probes such as NBD-glucose for measuring glucose uptake [58][59][60], with the exception of a few metabolites that have intrinsic fluorescence (e.g., FADH2, NAD(P)H) [196]. In addition, this approach cannot resolve stable isotopes and is currently low in metabolic coverage.…”

Empirical method for rapid quantification of intrinsic fluorescence signals of key metabolic probes from optical spectra measured on tissue-mimicking turbid medium

“…9,10 Biomedical optical spectroscopy techniques have gained increasing interest in measuring glycolysis and mitochondrial function of tumors in vivo for cancer research due to their cost-effectiveness and high portability. [11][12][13][14] Our group has developed techniques to quantify glucose uptake using glucose analog 2-NBDG 15 and mitochondrial membrane potential using TMRE 16 in tumor models in vivo. 11,12 A significant challenge for using biomedical optical spectroscopy to quantify metabolic parameters in vivo is to effectively remove the attenuation caused by tissue absorption and scattering on the measured fluorescence signals.…”

“…[11][12][13][14] Our group has developed techniques to quantify glucose uptake using glucose analog 2-NBDG 15 and mitochondrial membrane potential using TMRE 16 in tumor models in vivo. 11,12 A significant challenge for using biomedical optical spectroscopy to quantify metabolic parameters in vivo is to effectively remove the attenuation caused by tissue absorption and scattering on the measured fluorescence signals. 17 We previously developed an inverse scalable Monte Carlo-based model to extract intrinsic fluorescence from turbid media with high accuracy and demonstrated this technique for quantification of 2-NBDG and TMRE uptake on small tumor models in vivo.…”

“…17 We previously developed an inverse scalable Monte Carlo-based model to extract intrinsic fluorescence from turbid media with high accuracy and demonstrated this technique for quantification of 2-NBDG and TMRE uptake on small tumor models in vivo. 11,12 However, it is difficult to adapt the Monte Carlo technique for real-time data processing due to the time-consuming fitting processing. 13 To enable real-time spectral data processing, we have developed and now present an empirical ratiometric method for rapid fluorescence spectra attenuation correction.…”