Preinvasive and invasive cervical cancer: an ex vivo proton magic angle spinning magnetic resonance spectroscopy study

Research progress of metabolomics in cervical cancer

INTRODUCTION

Cervical cancer threatens women's health seriously. In recent years, the incidence of cervical cancer is on the rise, and the age of onset tends to be younger. Prevention, early diagnosis and specific treatment have become the main means to change the prognosis of cervical cancer patients. Metabolomics research can directly reflect the changes of biochemical processes and microenvironment in the body, which can provide a comprehensive understanding of the changes of metabolites in the process of disease occurrence and development, and provide new ways for the prevention and diagnosis of diseases.

OBJECTIVES

The aim of this study is to review the metabolic changes in cervical cancer and the application of metabolomics in the diagnosis and treatment.

METHODS

PubMed, Web of Science, Embase and Scopus electronic databases were systematically searched for relevant studies published up to 2022.

RESULTS

With the emergence of metabolomics, metabolic regulation and cancer research are further becoming a focus of attention. By directly reflecting the changes in the microenvironment of the body, metabolomics research can provide a comprehensive understanding of the patterns of metabolites in the occurrence and development of diseases, thus providing new ideas for disease prevention and diagnosis.

CONCLUSION

With the continuous, in-depth research on metabolomics research technology, it will bring more benefits in the screening, diagnosis and treatment of cervical cancer with its advantages of holistic and dynamic nature.

Focus on the glycerophosphocholine pathway in choline phospholipid metabolism of cancer

Activated choline metabolism is a hallmark of carcinogenesis and tumor progression, which leads to elevated levels of phosphocholine and glycerophosphocholine in all types of cancer tested so far. Magnetic resonance spectroscopy applications have played a key role in detecting these elevated choline phospholipid metabolites. To date, the majority of cancer-related studies have focused on phosphocholine and the Kennedy pathway, which constitutes the biosynthesis pathway for membrane phosphatidylcholine. Fewer and more recent studies have reported on the importance of glycerophosphocholine in cancer. In this review article, we summarize the recent literature on glycerophosphocholine metabolism with respect to its cancer biology and its detection by magnetic resonance spectroscopy applications.

Proton MRS of cervical cancer at 7 T

The differentiation grade of cervical cancer is histologically assessed by examining biopsies or surgical specimens. MRS is a highly sensitive technique that images tissue metabolism and can be used to increase the specificity of tissue characterization in a non-invasive manner. We aim to explore the feasibility of using in vivo ¹ H-MRS at 7 T in women with cervical cancer to study tissue fatty acid composition. 10 women with histologically proven Stage IB1-IIB cervical cancer were scanned with a whole-body 7 T MR system with a multi-transmit system and an internal receive only monopole antenna. A STEAM sequence was used to obtain ¹ H-MRS data. Fatty acid resonances were fitted with Lorentzian curves and the 2.1 ppm/1.3 ppm ratios were calculated. ¹ H-MRS data showed fatty acid signals resonating at 2.1 ppm, 1.9 ppm, 1.5 ppm, 1.3 ppm and 0.9 ppm. Mean 2.1/1.3 ppm ratios were 0.019 ± 0.01, 0.021 ± 0.006, 0.12 ± 0.089 and 0.39 ± 0.27 for normal, Grade I, Grade II and Grade III groups respectively. Poorly differentiated tumor tissue (Grade III) showed elevated fatty acid ratios when compared with the well differentiated tumor (Grade I) or normal tissue. ¹ H-MRS in cervical cancer at 7 T is feasible and individual fatty acid signals were detected. In addition, poorly differentiated tumors show more fatty acid unsaturation. The 2.1 ppm/1.3 ppm ratio has potential for tumor characterization in a non-invasive manner for uterine cervical cancer.

Developing and validating a multivariable prediction model to improve the diagnostic accuracy in determination of cervical versus endometrial origin of uterine adenocarcinomas: A prospective MR study combining diffusion-weighted imaging and spectroscopy

BACKGROUND

A triage test to assist clinical decision-making on choosing primary chemoradiation for cervical carcinomas or primary surgery for endometrial carcinomas is important.

PURPOSE OR HYPOTHESIS

To develop and validate a multiparametric prediction model based on MR imaging and spectroscopy in distinguishing adenocarcinomas of uterine cervical or endometrial origin.

STUDY TYPE

Prospective diagnostic accuracy study.

POPULATION

Eighty-seven women: 25 cervical and 62 endometrial adenocarcinomas divided into training (n = 43; cervical/endometrial adenocarcinomas = 11/32) and validation (n = 44; 14/30) datasets.

FIELD STRENGTH/SEQUENCE

The 3T diffusion-weighted (DW) MR imaging and MR spectroscopy.

ASSESSMENT

Morphology, volumetric DW MR imaging and spectroscopy (MDS) scoring system with total points 0-5, based on presence of the following MR features assessed independently by two radiologists: (a) epicenter at the cervix, (b) rim enhancement, (c) disrupted cervical stromal integrity, (d) mean volumetric apparent diffusion coefficient values (ADCmean) higher than 0.98 × 10-3 mm² /s, (e) fatty acyl δ 1.3 ppm more than 161.92 mM. Histopathology as gold standard.

STATISTICAL TESTS

Logistic regression and receiver operator characteristic (ROC) curves analysis.

RESULTS

For both the training and validation datasets, the MDS score achieved an accuracy of 93.0% and 84.1%, significantly higher than that of morphology (88.4% and 79.5%), ADC value (74.4% and 68.2%), and spectroscopy (81.4% and 68.2%; P < 0.05 for all). The performances of the scoring were superior to the morphology in the training dataset (areas under the receiver operating characteristics curve [AUC] = 0.95 vs. 0.89; P = 0.046), but not in the validation dataset (AUC = 0.90 vs. 0.85; P = 0.289).

DATA CONCLUSION

MDS score has potentials to improve distinguishing adenocarcinomas of cervical or endometrial origin, and warrants large-scale studies for further validation.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1654-1666.

Applications of high-resolution magic angle spinning MRS in biomedical studies II-Human diseases

High-resolution magic angle spinning (HRMAS) MRS is a powerful method for gaining insight into the physiological and pathological processes of cellular metabolism. Given its ability to obtain high-resolution spectra of non-liquid biological samples, while preserving tissue architecture for subsequent histopathological analysis, the technique has become invaluable for biochemical and biomedical studies. Using HRMAS MRS, alterations in measured metabolites, metabolic ratios, and metabolomic profiles present the possibility to improve identification and prognostication of various diseases and decipher the metabolomic impact of drug therapies. In this review, we evaluate HRMAS MRS results on human tissue specimens from malignancies and non-localized diseases reported in the literature since the inception of the technique in 1996. We present the diverse applications of the technique in understanding pathological processes of different anatomical origins, correlations with in vivo imaging, effectiveness of therapies, and progress in the HRMAS methodology.

Characterisation of mobile lipid resonances in tissue biopsies from patients with cervical cancer and correlation with cytoplasmic lipid droplets

The aims of this study were to characterise the major saturated and unsaturated lipid peaks in histologically normal cervical epithelium and stroma, dysplastic epithelium (low-grade cervical intraepithelial neoplasia, CIN) and cancer-containing tissue samples from patients with cervical cancer using diffusion-weighted (1) H high-resolution magic angle spinning MRS, to determine whether mobile lipid resonances (MLRs) distinguish tissue types and to test for a correlation between MLRs and the number of cytoplasmic lipid droplets. Diffusion-weighted spectra of tissue biopsies were acquired using a stimulated echo sequence with bipolar gradients. Major saturated and unsaturated MLRs were identified and multivariate analysis of peak combinations was used to determine the best separation between tissue classes. Lipid droplets were visualised with Nile red staining and fluorescence microscopy. Correlations of saturated lipid resonances (0.9 and 1.3 ppm), polyunsaturated resonances (2.8 ppm), triglycerides (4.3 ppm) and unsaturated resonances (5.3 ppm) with average droplet number (per image) were investigated using a Spearman rank test. A large heterogeneity in lipid content among samples was observed, resulting in no significant differences in MLR intensities of individual peaks between the three tissue classes. Linear discriminant analysis separated 'no cancer' from 'cancer' based on the intensities at 0.9, 1.3, 2.2 and 2.8 ppm [area under the curve (AUC) = 0.939, p < 0.001], 'low-grade CIN' from 'cancer' based on the intensities at 0.9, 4.1, 4.3 and 5.3 ppm (AUC = 0.987, p < 0.001) and 'no cancer' from 'low-grade CIN' based on intensities at 0.9, 2.2 and 4.3 ppm (AUC = 0.984, p < 0.001). The distribution of cytoplasmic lipid droplets was nonuniform and was not related to the presence of epithelial or stromal components. On average, there were more droplets visible in low-grade CIN and cancer-containing tissues. Significant correlations between MLR peaks and lipid droplet number were seen for 0.9 (p = 0.002), 1.3 (p = 0.003) and 2.8 ppm (p = 0.018). MLR combinations indicative of average lipid structure efficiently separated tissue classes. Increased lipid resonances correlated with increased numbers of cytoplasmic lipid droplets.

Magnetic resonance spectroscopy of cancer metabolism and response to therapy

Magnetic resonance spectroscopy allows noninvasive in vivo measurements of biochemical information from living systems, ranging from cultured cells through experimental animals to humans. Studies of biopsies or extracts offer deeper insights by detecting more metabolites and resolving metabolites that cannot be distinguished in vivo. The pharmacokinetics of certain drugs, especially fluorinated drugs, can be directly measured in vivo. This review briefly describes these methods and their applications to cancer metabolism, including glycolysis, hypoxia, bioenergetics, tumor pH, and tumor responses to radiotherapy and chemotherapy.

Metabonomic signature analysis of cervical carcinoma and precancerous lesions in women by (1)H NMR spectroscopy

(1)H nuclear magnetic resonance (NMR)-based metabonomics has been used to characterize the metabolic profiles of cervical intraepithelial neoplasia (CIN) and cervical squamous cell carcinoma (CSCC). Principal component analysis (PCA) and orthogonal partial least-squares discriminant analysis (OPLS-DA) were used to model the systematic variation related to patients with CIN or CSCC with healthy controls. Potential metabolic biomarkers were identified using database comparisons, and the one-way analysis of variance (ANOVA) test was used to examine the significance of the metabolites. Compared with plasma obtained from the healthy controls, plasma from patients with CIN had higher levels of very-low density lipoprotein (VLDL), acetone, unsaturated lipid and carnitine, together with lower levels of creatine, lactate, isoleucine, leucine, valine, alanine, glutamine, histidine, glycine, acetylcysteine, myo-inositol, choline and glycoprotein. Plasma from patients with CSCC had higher levels of acetate and formate, together with lower levels of creatine, lactate, isoleucine, leucine, valine, alanine, glutamine, histidine and tyrosine compared with the plasma of the healthy controls. In addition, compared with the plasma of patients with CIN, the plasma of CSCC patients had higher levels of acetate, formate, lactate, isoleucine, leucine, valine, alanine, glutamine, histidine, tyrosine, acetylcysteine, myo-inositol, glycoprotein, α-glucose and β-glucose, together with lower levels of acetone, unsaturated lipid and carnitine. Moreover, the profiles showed high feasibility and specificity by statistical analysis with OPLS-DA compared to the Thinprep cytology test (TCT) by setting the histopathological outcome as standard. The metabolic profile obtained for cervical cancer is significant, even for the precancerous disease. This suggests a systemic metabolic response to cancer, which may be used to identify potential early diagnostic biomarkers of the cancer and to establish clinical diagnostic methods.

MR-visible lipids and the tumor microenvironment

MR-visible lipids or mobile lipids are defined as lipids that are observable using proton MRS in cells and tissues. These MR-visible lipids are composed of triglycerides and cholesterol esters that accumulate in neutral lipid droplets, where their MR visibility is conferred as a result of the increased molecular motion available in this unique physical environment. This review discusses the factors that lead to the biogenesis of MR-visible lipids in cancer cells and in other cell types, such as immune cells and fibroblasts. We focus on the accumulations of mobile lipids that are inducible in cultured cells by a number of stresses, including culture conditions, and in response to activating stimuli or apoptotic cell death induced by anticancer drugs. This is compared with animal tumor models, where increases in mobile lipids are observed in response to chemo- and radiotherapy, and to human tumors, where mobile lipids are observed predominantly in high-grade brain tumors and in regions of necrosis. Conducive conditions for mobile lipid formation in the tumor microenvironment are discussed, including low pH, oxygen availability and the presence of inflammatory cells. It is concluded that MR-visible lipids appear in cancer cells and human tumors as a stress response. Mobile lipids stored as neutral lipid droplets may play a role in the detoxification of the cell or act as an alternative energy source, especially in cancer cells, which often grow in ischemic/hypoxic environments. The role of MR-visible lipids in cancer diagnosis and the assessment of the treatment response in both animal models of cancer and human brain tumors is also discussed. Although technical limitations exist in the accurate detection of intratumoral mobile lipids, early increases in mobile lipids after therapeutic interventions may be useful as a potential biomarker for the assessment of treatment response in cancer.

Detection of metabolite changes in C6 glioma cells cultured with antimitotic oleyl glycoside by 1H MAS NMR

The synthetic glycoside, oleyl N-acetyl-alpha-D-glucosaminide (1), was previously shown to exhibit antimitotic activity on rat (C6) and human (U-373) glioma lines. To obtain information about its mechanism of action, metabolite changes in C6 glioma cells were analyzed after treatment with 1 using high-resolution magic angle spinning (1)H NMR. Compound 1 caused either a decrease or an increase in the intensity of the signal assigned to coenzyme A (CoA) metabolites depending on the concentration used. The data obtained from the (1)H NMR spectra of cells cultured with 1, combined with those obtained after treatment with oleic acid (an inhibitor of acetyl-CoA carboxylase) and phenyl butyrate (a known antineoplastic agent), suggest that 1 may be altering the metabolism of fatty acids and induce apoptosis of C6 glioma cells. These results point to NMR spectroscopy as an efficient technique for monitoring the response of the cells to therapeutic agents.

Short-term temperature effect on the HRMAS spectra of human brain tumor biopsies and their pattern recognition analysis

OBJECT

To investigate the effect of temperature (0 versus 37 degrees C) in the high-resolution magic angle spinning spectroscopy (HRMAS) pattern of human brain tumor biopsies and its influence in recognition-based tumor type prediction. This proof-of-principle study addressed the bilateral discrimination between meningioma (MM) and glioblastoma multiforme (GBM) cases.

MATERIALS AND METHODS

Forty-three tumor biopsy samples were collected (20 MM and 23 GBM), kept frozen and later analyzed at 0 degrees C and 37 degrees C by HRMAS. Post-HRMAS histopathology was used to validate the tumor type. Time-course experiments (100 min) at both temperatures were carried out to monitor HRMAS pattern changes. Principal component analysis and linear discriminant analysis were used for classifier development with a training set of 20 biopsies.

RESULTS

Temperature-dependent, spectral pattern changes mostly affected mobile lipids and choline-containing compounds resonances and were essentially reversible. Incubation of 3 MM and 3 GBM at 37 degrees C during 100 minutes produced irreversible pattern changes below 13% in a few resonances. Classification performance of an independent test set of 7 biopsies was 100% for the pulse-and-acquire, CPMG at echo times (TE) of 30 ms and 144 ms and Hahn Echo at TE 30 ms at 0 degrees C and 37 degrees C. The performance for Hahn Echo spectra at 136 ms was 83.3% at 0 degrees C and 100% at 37 degrees C.

CONCLUSION

The spectral pattern of mobile lipids changes reversibly with temperature. HRMAS demonstrated potential for automated brain tumor biopsy classification. No advantage was obtained when acquiring spectra at 37 degrees C with respect to 0 degrees C in most of the conditions used for the discrimination addressed.

Molecular imaging of cancer: MR spectroscopy and beyond

Proton magnetic resonance spectroscopic imaging is a non-invasive diagnostic tool for the investigation of cancer metabolism. As an adjunct to morphologic and dynamic magnetic resonance imaging, it is routinely used for the staging, assessment of treatment response, and therapy monitoring in brain, breast, and prostate cancer. Recently, its application was extended to other cancerous diseases, such as malignant soft-tissue tumours, gastrointestinal and gynecological cancers, as well as nodal metastasis. In this review, we discuss the current and evolving clinical applications of proton magnetic resonance spectroscopic imaging. In addition, we will briefly discuss other evolving techniques, such as phosphorus magnetic resonance spectroscopic imaging, sodium imaging and diffusion-weighted imaging in cancer assessment.

Detection of cancer in cervical tissue biopsies using mobile lipid resonances measured with diffusion-weighted (1)H magnetic resonance spectroscopy

The purpose of this study was to implement a diffusion-weighted sequence for visualisation of mobile lipid resonances (MLR) using high resolution magic angle spinning (HR-MAS) (1)H MRS and to evaluate its use in establishing differences between tissues from patients with cervical carcinoma that contain cancer from those that do not. A stimulated echo sequence with bipolar gradients was modified to allow T(1) and T(2) measurements and optimised by recording signal loss in HR-MAS spectra as a function of gradient strength in model lipids and tissues. Diffusion coefficients, T(1) and apparent T(2) relaxation times were measured in model lipid systems. MLR profiles were characterised in relation to T(1) and apparent T(2) relaxation in human cervical cancer tissue samples. Diffusion-weighted (DW) spectra of cervical biopsies were quantified and peak areas analysed using linear discriminant analysis (LDA). The optimised sequence reduced spectral overlap by suppressing signals originating from low molecular weight metabolites and non-lipid contributions. Significantly improved MLR visualisation allowed visualisation of peaks at 0.9, 1.3, 1.6, 2.0, 2.3, 2.8, 4.3 and 5.3 ppm. MLR analysis of DW spectra showed at least six peaks arising from saturated and unsaturated lipids and those arising from triglycerides. Significant differences in samples containing histologically confirmed cancer were seen for peaks at 0.9 (p < 0.006), 1.3 (p < 0.04), 2.0 (p < 0.03), 2.8 (p < 0.003) and 4.3 ppm (p < 0.0002). LDA analysis of MLR peaks from DW spectra almost completely separated two clusters of cervical biopsies (cancer, 'no-cancer'), reflecting underlying differences in MLR composition. Generated Receiver Operating Characteristic (ROC) curves and calculated area under the curve (0.962) validated high sensitivity and specificity of the technique. Diffusion-weighting of HR-MAS spectroscopic sequences is a useful method for characterising MLR in cancer tissues and displays an accumulation of lipids arising during tumourigenesis and an increase in the unsaturated lipid and triglyceride peaks with respect to saturated MLR.

Metabolic profiling of human lung cancer tissue by 1H high resolution magic angle spinning (HRMAS) NMR spectroscopy

This work aims at characterizing the metabolic profile of human lung cancer, to gain new insights into tumor metabolism and to identify possible biomarkers with potential diagnostic value in the future. Paired samples of tumor and noninvolved adjacent tissues from 12 lung tumors have been directly analyzed by (1)H HRMAS NMR (500/600 MHz) enabling, for the first time to our knowledge, the identification of over 50 compounds. The effect of temperature on tissue stability during acquisition time has also been investigated, demonstrating that analysis should be performed within less than two hours at low temperature (277 K), to minimize glycerophosphocholine (GPC) and phosphocholine (PC) conversion to choline and reduce variations in some amino acids. The application of Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) to the standard 1D (1)H spectra resulted in good separation between tumor and control samples, showing that inherently different metabolic signatures characterize the two tissue types. On the basis of spectral integration measurements, lactate, PC, and GPC were found to be elevated in tumors, while glucose, myo-inositol, inosine/adenosine, and acetate were reduced. These results show the valuable potential of HRMAS NMR-metabonomics for investigating the metabolic phenotype of lung cancer.

Determination of metabolite concentrations in human brain tumour biopsy samples using HR-MAS and ERETIC measurements

Accurate determination of the concentration of the metabolites contained in intact human biopsies of 10 glioblastoma multiforme samples was achieved using one-dimensional (1)H high-resolution magic angle spinning (HR-MAS) NMR combined with ERETIC (electronic reference to in vivo concentrations) measurements. The amount of sample used ranged from 6.8 to 12.9 mg. Metabolite concentrations were measured in each sample using two methods: with DSS (2,2-dimethyl-2-silapentane-5-sulfonate sodium salt) as an internal reference and with ERETIC as an external electronically generated reference. The ERETIC signal was shown to be highly reproducible and did not affect the spectral quality. The concentrations calculated by the ERETIC method in model solutions were shown to be independent of the salt concentration in the range typically found in biological samples (0-250 mM). The ERETIC method proved to be straightforward to use in tissues and much more robust than the internal standard method. The concentrations calculated using the internal DSS concentration were systematically found to be higher than those determined using the ERETIC technique. These results indicate a possible interaction of the DSS molecules with the biopsy sample. Moreover, variations in the sample preparation process, with possible loss of DSS solution, may hamper the quantification process, as happens in one of the ten samples analysed. In this study, the ERETIC method was validated on model solutions and used in brain tumour tissues. Calculated metabolite concentrations obtained with the ERETIC procedure matched the values determined in the same type of tumours by in vivo, ex vivo and in vitro methodologies.

Investigation of metabolite changes in the transition from pre-invasive to invasive cervical cancer measured using (1)H and (31)P magic angle spinning MRS of intact tissue

The aim of this study was to determine the metabolic changes in the transition from pre-invasive to invasive cervical cancer using high-resolution magic angle spinning (HR-MAS) MRS. Biopsy specimens were obtained from women with histologically normal cervix (n = 5), cervical intraepithelial neoplasia (CIN; mild, n = 5; moderate/severe, n = 40), and invasive cancer (n = 23). (1)H HR-MAS MRS data were acquired using a Bruker Avance 11.74 T spectrometer (Carr-Purcell-Meiboom-Gill sequence; TR = 4.8 s; TE = 135 ms; 512 scans; 41 min acquisition). (31)P HR-MAS spectra were obtained from the normal subjects and cancer patients only (as acetic acid applied before tissue sampling in patients with CIN impaired spectral quality) using a (1)H-decoupled pulse-acquire sequence (TR = 2.82 s; 2048 scans; 96 min acquisition). Peak assignments were based on values reported in the literature. Peak areas were measured using the AMARES algorithm. Estimated metabolite concentrations were compared between patient diagnostic categories and tissue histology using independent samples t tests. Comparisons based on patient category at diagnosis showed significantly higher estimated concentrations of choline (P = 0.0001) and phosphocholine (P = 0.002) in tissue from patients with cancer than from patients with high-grade dyskaryosis, but no differences between non-cancer groups. Division by histology of the sample also showed increases in choline (P = 0.002) and phosphocholine (P = 0.002) in cancer compared with high-grade CIN tissue. Phosphoethanolamine was increased in cancer compared with normal tissue (P = 0.0001). Estimated concentrations of alanine (P = 0.01) and creatine (P = 0.008) were significantly reduced in normal tissue from cancer patients compared with normal tissue from non-cancer patients. The estimated concentration of choline was significantly increased in CIN tissue from cancer patients compared with CIN tissue from non-cancer patients (P = 0.0001). Estimated concentrations of choline-containing metabolites increased from pre-invasive to invasive cervical cancer. Concurrent metabolite depletion occurs in normal tissue adjacent to cancer tissue.

An assessment of the effects of sample ischaemia and spinning time on the metabolic profile of brain tumour biopsy specimens as determined by high-resolution magic angle spinning (1)H NMR

High-resolution magic angle spinning (HRMAS) (1)H NMR of biopsy tissue provides a biochemical profile that has potential diagnostic and prognostic value, and can aid interpretation of the lower-resolution (1)H-NMR spectra obtained in vivo. However, the biochemical profile obtained may be affected by experimental factors such as a period of ischaemia before snap-freezing of the biopsy tissue for subsequent analysis and the mechanical stress of the spinning procedure of HRMAS itself. We have used normal rat brain cortex as a 'gold standard', either funnel-frozen or deliberately allowed to become ischaemic for set periods of time before snap-freezing, to quantitatively investigate these two effects. In addition, we have compared biochemical changes that occur in normal rat brain during HRMAS (spun continuously at 5 kHz for 4 h at 4 degrees C as could be required for a two-dimensional acquisition) with those that occur in biopsy samples from low-grade and high-grade adult human astrocytomas, during the same HRMAS procedure. Significant changes due to delayed initial sample freezing were noted in metabolites associated with glycolysis (alanine, glucose and lactate), as expected. However, for the funnel-frozen rat tissue at 4 degrees C, there were even more significant changes, which appear to be the result of extended spinning at 5 kHz. In particular, the 18% total creatine increase observed is unlikely to be de novo synthesis of creatine. More likely, the asymptotic exponential increase in creatine suggests an exponential release of an NMR-invisible bound creatine store as a result of tissue damage from mechanical stress of sample spinning. Overall, it appears that tissue ischaemia during biopsy excision and delays in snap-freezing may have less significant effects on metabolite profile than the prolonged spinning times required for two-dimensional HRMAS, and this must be accounted for when results are being interpreted.

Studies on the Uptake of Glucose Derivatives by Red Blood Cells

Erythrocytes express the same glucose transporter (GLUT-1) as is present in the blood-brain barrier. With the aim of testing the viability of using this transport system to deliver glucosyl drug derivatives to the brain, the uptake of several dopamine-glucose conjugates and a few structurally related analogues by erythrocytes was studied with HPLC and (1)H MAS NMR spectroscopy. The results showed that slight structural changes determine the uptake of glycoconjugates by red blood cells. However, experiments in the presence of glucose transport inhibitors showed that none of the conjugates that efficiently crossed the cell membrane were transported by GLUT-1.

Metabolic mapping by use of high-resolution magic angle spinning 1H MR spectroscopy for assessment of apoptosis in cervical carcinomas

Background

High-resolution magic angle proton magnetic resonance spectroscopy (HR ¹H MAS MRS) provides a broad metabolic mapping of intact tumor samples and allows for microscopy investigations of the samples after spectra acquisition. Experimental studies have suggested that the method can be used for detection of apoptosis, but this has not been investigated in a clinical setting so far. We have explored this hypothesis in cervical cancers by searching for metabolites associated with apoptosis that were not influenced by other histopathological parameters like tumor load and tumor cell density.

Methods

Biopsies (n = 44) taken before and during radiotherapy in 23 patients were subjected to HR MAS MRS. A standard pulse-acquire spectrum provided information about lipids, and a spin-echo spectrum enabled detection of non-lipid metabolites in the lipid region of the spectra. Apoptotic cell density, tumor cell fraction, and tumor cell density were determined by histopathological analysis after spectra acquisition.

Results

The apoptotic cell density correlated with the standard pulse-acquire spectra (p < 0.001), but not with the spin-echo spectra, showing that the lipid metabolites were most important. The combined information of all lipids contributed to the correlation, with a major contribution from the ratio of fatty acid -CH₂ to CH₃ (p = 0.02). In contrast, the spin-echo spectra contained the main information on tumor cell fraction and tumor cell density (p < 0.001), for which cholines, creatine, taurine, glucose, and lactate were most important. Significant correlations were found between tumor cell fraction and glucose concentration (p = 0.001) and between tumor cell density and glycerophosphocholine (GPC) concentration (p = 0.024) and ratio of GPC to choline (p < 0.001).

Conclusion

Our findings indicate that the apoptotic activity of cervical cancers can be assessed from the lipid metabolites in HR MAS MR spectra and that the HR MAS data may reveal novel information on the metabolic changes characteristic of apoptosis. These changes differed from those associated with tumor load and tumor cell density, suggesting an application of the method to explore the role of apoptosis in the course of the disease.

Current concepts in neuroendocrine cancer metabolism

Neuroendocrine (NE) cancers occur in multiple anatomic locations and range in prognosis from indolent to aggressive. In addition, adenocarcinomas can express gene products associated with NE cells, referred to as NE differentiation (NED), which correlates with poor prognosis and aggressive disease. Several metabolites and peptides produced by NE cells have been discovered that engage in cellular signaling and have autocrine and paracrine effects on cancer cell proliferation. This review focuses on the current knowledge of small molecule metabolism in NE cancers involving the synthesis of biogenic amine, polyamine, and amino acid neurotransmitters. Systems biology-directed approaches to NE cancer metabolism using gene expression profiling, liquid chromatography/mass spectrometry (LC/MS) and nuclear magnetic resonance (NMR) are also discussed. Furthermore, knowledge of metabolic and signaling pathways in NE cancers has led to the successful implementation of therapeutic regimens in cell culture and animal models of NE carcinogenesis.