MR spectroscopy in breast cancer metabolomics

Abstract

Breast cancer poses a significant health care challenge worldwide requiring early detection and effective treatment strategies for better patient outcome. A deeper understanding of the breast cancer biology and metabolism may help developing better diagnostic and therapeutic approaches. Metabolomic studies give a comprehensive analysis of small molecule metabolites present in human tissues in vivo. The changes in the level of these metabolites provide information on the complex mechanism of the development of the disease and its progression. Metabolomic approach using analytical techniques such as magnetic resonance spectroscopy (MRS) has evolved as an important tool for identifying clinically relevant metabolic biomarkers. The metabolic characterization of breast lesions using in-vivo MRS has shown that malignant breast tissues contain elevated levels of choline containing compounds (tCho), suggesting rapid proliferation of cancer cells and alterations in membrane metabolism. Also, tCho has been identified as one of the important biomarkers that help to enhance the diagnostic accuracy of dynamic contrast enhanced magnetic resonance imaging and also for monitoring treatment response. Further, metabolome of malignant tissues can be studied using ex vivo and in vitro MRS at high magnetic fields. This provided the advantage of detection of a large number of compounds that facilitated more comprehensive insight into the altered metabolic pathways associated with the cancer development and progression and also in identification of several metabolites as potential biomarkers. This article briefly reviews the role of MRS based metabolic profiling in the discovery of biomarkers and understanding of the altered metabolism in breast cancer.

Keywords: biomarker; breast cancer; ex vivo; in vitro; in vivo; in vivo magnetic resonance spectroscopy (MRS); metabolomics; therapeutic response.

FIGURE 1

(A) T1‐weighted MR image of the normal breast from a volunteer showing the voxel position from which a single‐voxel ¹H MR in vivo spectrum (B) was obtained without water and fat suppression (Reprinted with permission from John Wiley & Sons, Inc. from references # 37 and 38)

FIGURE 2

In vivo proton MR spectra acquired at TE = 135 ms from three different voxel (8 ml) locations within the normal breast of a 31 year old normal female volunteer. (A) Upper quadrant, (B) Para‐areolar region, (C) Lower quadrant (Reprinted with permission from Elsevier from reference # 62)

FIGURE 3

(A) MRI of a patient with locally advanced breast cancer showing the voxel position from which the single‐voxel ¹H MR in‐vivo spectrum was obtained without water and fat (lipid) suppression (B) and with the suppression of water+fat (lipid) resonances (C) (Reprinted with permission from John Wiley & Sons, Inc. from reference # 38)

FIGURE 4

The role of metabolic reprogramming in breast cancer cells, their role in cancer and the induced co‐adaptive mechanism (Reprinted with permission from John Wiley & Sons, Inc. from reference # 27)

FIGURE 5

T2‐weighted fat suppressed axial image (A) from the normal breast tissue of a lactating women volunteer showing a voxel location of size 20×20×20 mm³ (B) corresponding ¹H MR spectrum obtained without water and lipid suppression showing the water and lipid peaks. (C) ¹H MR spectrum obtained with water and lipid suppression showing the residual water and lipid along with the tCho and the lactose peaks (Reprinted with permission from John Wiley & Sons, Inc. from reference # 72)

FIGURE 6

Schematic representation of the link between the choline synthesis and the Wnt‐mediated β‐catenin pathway. (A) Normal breast tissue: In a normal breast tissue Wnt (green polygon) signaling is absent and β‐catenin (brown rectangles) level is maintained low in the cell cytosol due to phosphorylation (red stars) and degradation of β‐catenin. Also, cyclin D1 (red circles) translocates to the nucleus at a reduced rate to participate in G1 to S phase transition. The cell division rate is regulated. Phosphatidyl choline (PtdCho; blue rectangle) which is a membrane phospholipid, converts into phosphocholine (PCho; brown triangle) in the cytosol by the activity of phospholipase D (PLD; grey circle). (B) Malignant breast tissue: During malignancy, Wnt signaling is active and hence β‐catenin increases in the cytosol that can translocate to the nucleus and bind to cyclin D1 (brown rectangle + red circle), to increase the rate of cellular transcription. With the increase in cellular proliferation, membrane requirement for PtdCho increases that in turn leads to increased PLD activity (double grey circle). PCho increases in the cell cytosol, thereby increasing the tCho levels. Increased cytosolic β‐catenin levels also increase the activity of PLD (Reprinted with permission from John Wiley & Sons, Inc. from reference # 74)

FIGURE 7

The 3‐D score plot (PC1‐PC3) of PCA analysis of multi‐parametric data (volume, ADC and tCho) in pathological responders and non‐responders at Tp0 (A) after Tp1 (B) Tp2 (C) and Tp3 (D) while (E–H) show the 3‐D score plot for clinical response (Figure as originally published in reference # 81: Uma Sharma, Khushbu Agarwal, Rani G. Sah, Rajinder Parshad, Vurthaluru Seenu, Sandeep Mathur, Siddhartha D. Gupta and Naranamangalam R. Jagannathan (2018). Front. Oncol. 15 August 2018 https://doi.org/10.3389/fonc.2018.00319)

FIGURE 8

In vitro ¹H magnetic resonance (MR) spectrum from the aliphatic region of the perchloric acid extracted from involved breast cancer tissue recorded at 400 MHz nuclear magnetic resonance (NMR). Abbreviations: Ala, alanine; Ace, acetate; Arg, arginine; Asp, aspartate; Cho, choline; Cr, creatine; Glc, glucose; Glu, glutamate; Gln, glutamine; GPC, glycerophosphocholine; Gly, glycine; Iso, isoleucine; KG, ketogultarate Lac, lactate; Leu, leucine; Lys, lysine; mI, myo‐inositol; PCr, phosphocreatine; PCho, phosphocholine; Pyr, pyruvate; Suc, succinate; Tau, taurine; Val, valine (Figure as originally published in reference # 52: Jagannathan NR, Sharma U. Breast tissue metabolism by magnetic resonance spectroscopy. Metabolites 2017;7(2):25. https://doi.org/10.3390/metabo7020025)

FIGURE 9

High‐resolution 400 MHz proton MR spectrum of fine‐needle aspirate (FNAC‐ex vivo) from (A) malignant and (B) benign breast tissues. Abbreviations: Leu: leucine; Val: valine; Thr: threonine; Lac: lactate; Ala: alanine; Lys: lysine; Ac: acetate; Glu: glutamic acid; Gln: glutamine; PCr: phosphocreatine; Cr: creatine; PEtn: phosphoethanol amine; Etn: ethanol amine; PCho: phosphocholine; Cho: choline; Tau: taurine; Gly: glycine; Asp: aspartate; CH₃, CH₂CO, CO‐CH₂‐CH₂‐: groups of lipids (Reprinted with permission from Bentham Science Publishers from reference # 43)