The phosphocholine and glycerophosphocholine content of an oestrogen-sensitive rat mammary tumour correlates strongly with growth rate

Phosphatidylcholine-Derived Lipid Mediators: The Crosstalk Between Cancer Cells and Immune Cells

To become resistant, cancer cells need to activate and maintain molecular defense mechanisms that depend on an energy trade-off between resistance and essential functions. Metabolic reprogramming has been shown to fuel cell growth and contribute to cancer drug resistance. Recently, changes in lipid metabolism have emerged as an important driver of resistance to anticancer agents. In this review, we highlight the role of choline metabolism with a focus on the phosphatidylcholine cycle in the regulation of resistance to therapy. We analyze the contribution of phosphatidylcholine and its metabolites to intracellular processes of cancer cells, both as the major cell membrane constituents and source of energy. We further extended our discussion about the role of phosphatidylcholine-derived lipid mediators in cellular communication between cancer and immune cells within the tumor microenvironment, as well as their pivotal role in the immune regulation of therapeutic failure. Changes in phosphatidylcholine metabolism are part of an adaptive program activated in response to stress conditions that contribute to cancer therapy resistance and open therapeutic opportunities for treating drug-resistant cancers.

Metabolomics Identifies Metabolic Markers of Maturation in Human Pluripotent Stem Cell-Derived Cardiomyocytes

Cardiovascular disease is a leading cause of death worldwide. Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) hold immense clinical potential and recent studies have enabled generation of virtually pure hPSC-CMs with high efficiency in chemically defined and xeno-free conditions. Despite these advances, hPSC-CMs exhibit an immature phenotype and are arrhythmogenic in vivo, necessitating development of strategies to mature these cells. hPSC-CMs undergo significant metabolic alterations during differentiation and maturation. A detailed analysis of the metabolic changes accompanying maturation of hPSC-CMs may prove useful in identifying new strategies to expedite hPSC-CM maturation and also may provide biomarkers for testing or validating hPSC-CM maturation. In this study we identified global metabolic changes which take place during long-term culture and maturation of hPSC-CMs derived from three different hPSC lines. We have identified several metabolic pathways, including phospholipid metabolism and pantothenate and Coenzyme A metabolism, which showed significant enrichment upon maturation in addition to fatty acid oxidation and metabolism. We also identified increases in glycerophosphocholine and the glycerophosphocholine:phosphocholine ratio as potential metabolic biomarkers of maturation. These biomarkers were also affected in a similar manner during murine heart development in vivo. These results support that hPSC-CM maturation is associated with extensive metabolic changes in metabolic network utilization and understanding the roles of these metabolic changes has the potential to develop novel approaches to monitor and expedite hPSC-CM maturation.

Probing the PI3K/Akt/mTor pathway using 31P-NMR spectroscopy: routes to glycogen synthase kinase 3

Akt is an intracellular signalling pathway that serves as an essential link between cell surface receptors and cellular processes including proliferation, development and survival. The pathway has many downstream targets including glycogen synthase kinase3 which is a major regulatory kinase for cell cycle transit as well as controlling glycogen synthase activity. The Akt pathway is frequently up-regulated in cancer due to overexpression of receptors such as the epidermal growth factor receptor, or mutation of signalling pathway kinases resulting in inappropriate survival and proliferation. Consequently anticancer drugs have been developed that target this pathway. MDA-MB-468 breast and HCT8 colorectal cancer cells were treated with inhibitors including LY294002, MK2206, rapamycin, AZD8055 targeting key kinases in/associated with Akt pathway and the consistency of changes in ³¹P-NMR-detecatable metabolite content of tumour cells was examined. Treatment with the Akt inhibitor MK2206 reduced phosphocholine levels in MDA-MB-468 cells. Treatment with either the phosphoinositide-3-kinase inhibitor, LY294002 and pan-mTOR inhibitor, AZD8055 but not pan-Akt inhibitor MK2206 increased uridine-5′-diphosphate-hexose cell content which was suppressed by co-treatment with glycogen synthase kinase 3 inhibitor SB216763. This suggests that there is an Akt-independent link between phosphoinositol-3-kinase and glycogen synthase kinase3 and demonstrates the potential of ³¹P-NMR to probe intracellular signalling pathways.

Metformin Decouples Phospholipid Metabolism in Breast Cancer Cells

INTRODUCTION

The antidiabetic drug metformin, currently undergoing trials for cancer treatment, modulates lipid and glucose metabolism both crucial in phospholipid synthesis. Here the effect of treatment of breast tumour cells with metformin on phosphatidylcholine (PtdCho) metabolism which plays a key role in membrane synthesis and intracellular signalling has been examined.

METHODS

MDA-MB-468, BT474 and SKBr3 breast cancer cell lines were treated with metformin and [3H-methyl]choline and [14C(U)]glucose incorporation and lipid accumulation determined in the presence and absence of lipase inhibitors. Activities of choline kinase (CK), CTP:phosphocholine cytidylyl transferase (CCT) and PtdCho-phospholipase C (PLC) were also measured. [3H] Radiolabelled metabolites were determined using thin layer chromatography.

RESULTS

Metformin-treated cells exhibited decreased formation of [3H]phosphocholine but increased accumulation of [3H]choline by PtdCho. CK and PLC activities were decreased and CCT activity increased by metformin-treatment. [14C] incorporation into fatty acids was decreased and into glycerol was increased in breast cancer cells treated with metformin incubated with [14C(U)]glucose.

CONCLUSION

This is the first study to show that treatment of breast cancer cells with metformin induces profound changes in phospholipid metabolism.

High-field small animal magnetic resonance oncology studies

This review focuses on the applications of high magnetic field magnetic resonance imaging (MRI) and spectroscopy (MRS) to cancer studies in small animals. High-field MRI can provide information about tumor physiology, the microenvironment, metabolism, vascularity and cellularity. Such studies are invaluable for understanding tumor growth and proliferation, response to treatment and drug development. The MR techniques reviewed here include (1)H, (31)P, chemical exchange saturation transfer imaging and hyperpolarized (13)C MRS as well as diffusion-weighted, blood oxygen level dependent contrast imaging and dynamic contrast-enhanced MRI. These methods have been proven effective in animal studies and are highly relevant to human clinical studies.

Quantitative 31P magnetic resonance spectroscopy of the human breast at 7 T

This study presents quantified levels of phosphorylated metabolites in glandular tissue of human breast using (31)P magnetic resonance spectroscopy at 7 T. We used a homebuilt (1)H/(31)P radiofrequency coil to obtain artifact-free (31)P MR spectra of glandular tissue of healthy females by deploying whole breast free induction decay (FID) detection with adiabatic excitation and outer volume suppression. Using progressive saturation, the estimated apparent T(1) relaxation time of (31)P spins of phosphocholine and phosphoethanolamine was 4.4 and 5.7 s, respectively. Quantitative measures for phosphocholine and phosphoethanolamine levels in glandular tissue were established based on MR imaging. We used a 3D (1)H image of the breast to segment the glandular tissue; this was matched to a 3D (31)P image of the B1- field of the (31)P coil to correct for differences in glandular tissue volume and B(1) inhomogeneity of the (31)P coil. The (31)P MR spectra were calibrated using a phantom with known concentration. Average levels of phosphocholine and phosphoethanolamine in 11 volunteers were 0.84 ± 0.21 mM and 1.18 ± 0.41 mM, respectively. In addition, data of three patients with breast cancer showed higher levels of phosphocholine and phosphoethanolamine compared with healthy volunteers. This may indicate a potential role for the use of (31)P magnetic resonance spectroscopy for characterization, prognosis, and treatment monitoring in breast cancer.

Role of endorectal magnetic resonance spectroscopic imaging in two different Gleason scores in prostate cancer

OBJECTIVE

The major goal of the work was to record three-dimensional magnetic resonance spectroscopic imaging (MRSI) and to compare metabolite ratios between different Gleason scores (GS).

MATERIALS AND METHODS

MRSI localized by endorectal coil-acquired point-resolved spectroscopy was performed in 14 men with prostate cancer of GS 6 (n = 7) and 7 (n = 7) using a 1.5-tesla MRI scanner.

RESULTS

The ratio of (choline + creatine)/citrate was increased with an increase of GS, i.e. 0.590 ± 0.171 in the target lesion and 0.321 ± 0.157 in the contralateral region of patients with a GS of 6 as opposed to 1.082 ± 0.432 in the target lesion and 0.360 ± 0.243 in the contralateral region of patients with a GS of 7.

CONCLUSION

Our pilot results demonstrated that MRSI was an additional biochemical tool which is complementary to the current imaging modalities for early diagnosis and therapeutic management of prostate cancer.

Uncovering the metabolomic fingerprint of breast cancer

Metabolomics, the study of metabolites and small intermediate molecules, may play a key role in further elucidation of breast cancer. This dynamic, simultaneous assessment of thousands of metabolites allows identification of the presence, concentration and fluxes of specific metabolites, and recognition of the critical metabolic pathways recruited in carcinogenesis. Studies of tumour cell and tissue allow focused analysis on the tumour, whilst studies of biofluids have the appeal of concurrent assessment of tumour and host. Elucidation of these metabolites and pathways may provide essential insights into both the intercellular environment and host/tumour interaction, allowing recognition of new biomarkers for diagnosis and prediction of outcome, new therapy targets and novel approaches for monitoring response and toxicity. Certainly, the field of metabolomics may evolve as a valuable, complementary clinical tool. In this review, current metabolomic data in breast cancer will be presented. The dominant metabolic pathways and metabolite disturbances associated with malignant transformation of breast cells will be outlined, leading to an overview of potential clinical implications for individuals with breast cancer.

F-18-FDG and C-11-Choline Positron Emission Tomography in Human Esophago-Gastric Cancer: Prediction of Response to Therapy

Background

To determine the utility of F-18-FDG and C-11-Choline uptake, in patients with esophageal and esophago-gastric junction tumors who are to undergo either neo-adjuvant or palliative chemotherapy, in predicting response (pathological and survival).

Methods

Eighteen patients with biopsy proven cancer were recruited prospectively. Patients underwent PET imaging before and during the first cycle of chemotherapy (seven and 14 days) with both F-18-FDG and C-11-Choline. Tracer uptake was quantified using Standardized Uptake Values. Pathological tumor response was determined using the Mandard criteria. Cellular proliferation was determined using ki-67 immunohistochemistry. Relationships between tracer uptake and response, one-year survival and cellular proliferation were determined.

Results

All 18 tumors were imaged by F-18-FDG PET compared to 16/18 with C-11-Choline. Change in uptake of either tracer did not correlate with pathological response. Pathological response did not influence survival (median-survival, responders = 16.1 months; non-responders = 19.0 months, p = 0.978). There was no significant correlation of change in tracer uptake with survival. C-11-Choline tumor uptake did not correlate with cellular proliferation.

Conclusion

F-18-FDG PET is superior for imaging of the primary tumor. Neither F-18-FDG nor C-11-Choline PET was able to predict response accurately.

In vivo MRS markers of response to CHOP chemotherapy in the WSU-DLCL2 human diffuse large B-cell lymphoma xenograft

To identify 1H-MRS molecular biomarkers of early clinical therapeutic response in non-Hodgkin's lymphoma, an in vivo longitudinal study was performed on human non-Hodgkin's diffuse large B-cell lymphoma xenografts (WSU-DLCL2) grown in the flanks of female SCID mice. 31P-MRS measurements, which have been demonstrated to be prognostic clinical indices of response (Arias-Mendoza et al. Acad. Radiol. 2004; 11: 368-376) but which provide lower spatial resolution, were included for comparison. The animals received CHOP (cyclophosphamide, hydroxydoxorubicin, oncovin and prednisone) chemotherapy for three 1-week cycles, resulting in stable disease based on tumor volume. Localization of total choline and phosphorus metabolites in vivo was achieved with stimulated echo acquisition mode and image selected in vivo spectroscopy sequences, respectively. Significant decreases in lactate were detected by the selective multiple quantum coherence spectral editing technique after the first cycle of CHOP, whereas total choline and the phosphomonoester/nucleoside triphosphate ratio did not change until the third cycle. Ex vivo extract MRS of tumors corroborated the in vivo results. Histological staining with antibodies to Ki67 revealed a decrease in proliferation rate in CHOP-treated tumors that coincided with the decrease in lactate. This study demonstrates the utility of lactate as an early proliferation-sensitive indicator of therapeutic response in a mouse model of non-Hodgkin's lymphoma and serves as a basis for future clinical implementation of these methods.

Magnetic resonance spectroscopy (MRS) in the investigation of cancer at The Royal Marsden Hospital and The Institute of Cancer Research

Developments in magnetic resonance spectroscopy (MRS) at The Royal Marsden Hospital and The Institute of Cancer Research are reviewed in the context of preceding developments in nuclear magnetic resonance (NMR) and MRS, and some of the early developments in this field, particularly those leading to human measurements. The early development of technology, and associated techniques for human measurement and assessment will be discussed, with particular reference to experience at out institutions. Applications using particular nuclei will then be described and related to other experimental work where appropriate. Contributions to the development of MRS that have been published in Physics in Medicine and Biology will be discussed.

Identification of magnetic resonance detectable metabolic changes associated with inhibition of phosphoinositide 3-kinase signaling in human breast cancer cells

Phosphoinositide 3-kinase (PI3K) is an attractive target for novel mechanism-based anticancer treatment. We used magnetic resonance (MR) spectroscopy (MRS) to detect biomarkers of PI3K signaling inhibition in human breast cancer cells. MDA-MB-231, MCF-7, and Hs578T cells were treated with the prototype PI3K inhibitor LY294002, and the (31)P MR spectra of cell extracts were monitored. In every case, LY294002 treatment was associated with a significant decrease in phosphocholine levels by up to 2-fold (P < 0.05). In addition, a significant increase in glycerophosphocholine levels by up to 5-fold was also observed (P <or= 0.05), whereas the content of glycerophosphoethanolamine, when detectable, did not change significantly. Nucleotide triphosphate levels did not change significantly in MCF-7 and MDA-MB-231 cells but decreased by approximately 1.3-fold in Hs578T cells (P = 0.01). The changes in phosphocholine and glycerophosphocholine levels seen in cell extracts were also detectable in the (31)P MR spectra of intact MDA-MB-231 cells following exposure to LY294002. When treated with another PI3K inhibitor, wortmannin, MDA-MB-231 cells also showed a significant decrease in phosphocholine content by approximately 1.25-fold relative to the control (P < 0.05), whereas the levels of the remaining metabolites did not change significantly. Our results indicate that PI3K inhibition in human breast cancer cells by LY294002 and wortmannin is associated with a decrease in phosphocholine levels.

Proton MR spectroscopy of the brain with a focus on chemical issues

Among the vast number of metabolites in living tissues, metabolites detectable by in vivo MR spectroscopy are limited to those present in high concentrations, and the actual number is only 10 to 20. None is disease-specific. Interpretation of MRS data, therefore, must be based on general knowledge of biochemical processes in association with pathological changes. Each spectrum is a window on the actual biochemical changes taking place within the living tissues, but the reality entails a wide and confusing variance. Continuous expansion of the knowledge may reduce the uncertainty of interpreting MRS data.

Magnetic resonance in surgical oncology: II - literature review

Ex vivo and in vivo applications of magnetic resonance spectroscopy have been developed which aid in distinguishing malignant from normal tissues. Studies of breast, colon, cervix, oesophageal and prostate cancer reveal both the successes and failings of present technology. Verification that these non-invasive tests might supplant conventional histology in obtaining spatial diagnostic and chemical prognostic information remains for the time being illusive.

In vivo magnetic resonance spectroscopy in cancer

Magnetic resonance spectroscopy (MRS) has been used for more than two decades to interrogate metabolite distributions in living cells and tissues. Techniques have been developed that allow multiple spectra to be obtained simultaneously with individual volume elements as small as 1 uL of tissue (i.e., 1 x 1 x 1 mm(3)). The most common modern applications of in vivo MRS use endogenous signals from (1)H, (31)P, or (23)Na. Important contributions have also been made using exogenous compounds containing (19)F, (13)C, or (17)O. MRS has been used to investigate cardiac and skeletal muscle energetics, neurobiology, and cancer. This review focuses on the latter applications, with specific reference to the measurement of tissue choline, which has proven to be a tumor biomarker that is significantly affected by anticancer therapies.

Magnetic Resonance Spectroscopy Monitoring of Mitogen-Activated Protein Kinase Signaling Inhibition

Several mitogen-activated protein kinase (MAPK) signaling inhibitors are currently undergoing clinical trial as part of novel mechanism-based anticancer treatment strategies. This study was aimed at detecting biomarkers of MAPK signaling inhibition in human breast and colon carcinoma cells using magnetic resonance spectroscopy. We investigated the effect of the prototype MAPK kinase inhibitor U0126 on the (31)P-MR spectra of MDA-MB-231, MCF-7 and Hs578T breast, and HCT116 colon carcinoma cells. Treatment of MDA-MB-231 cells with 50 micromol/L U0126 for 2, 4, 8, 16, 24, 32, and 40 hours caused inhibition of extracellular signal-regulated kinases (ERK1/2) phosphorylation from 2 hours onwards. (31)P-MR spectra of extracted cells indicated that this was associated with a significant drop in phosphocholine levels to 78 +/- 8% at 8 hours, 74 +/- 8% at 16 hours, 66 +/- 7% at 24 hours, 71 +/- 10% at 32 hours, and 65 +/- 10% at 40 hours post-treatment. In contrast, the lower concentration of 10 micromol/L U0126 for 40 hours had no significant effect on either P-ERK1/ 2 or phosphocholine levels in MDA-MB-231 cells. Depletion of P-ERK1/2 in MCF-7 and Hs578T cells with 50 micromol/L U0126 also produced a drop in phosphocholine levels to 51 +/- 17% at 40 hours and 23 +/- 12% at 48 hours, respectively. Similarly, in HCT116 cells, inhibition with 30 micromol/L U0126 caused depletion of P-ERK1/2 and a decrease in phosphocholine levels to 80 +/- 9% at 16 hours and 61 +/- 4% at 24 hours post-treatment. The reduction in phosphocholine in MDA-MB-231 and HCT116 cells correlated positively with the drop in P-ERK1/2 levels. Our results show that MAPK signaling inhibition with U0126 is associated with a time-dependent decrease in cellular phosphocholine levels. Thus, phosphocholine has potential as a noninvasive pharmacodynamic marker for monitoring MAPK signaling blockade.

Correlation of proton MR spectroscopic imaging with gleason score based on step-section pathologic analysis after radical prostatectomy

PURPOSE

To determine whether hydrogen 1 magnetic resonance (MR) spectroscopic imaging can be used to predict aggressiveness of prostate cancer.

MATERIALS AND METHODS

All patients gave informed consent according to an institutionally approved research protocol. A total of 123 patients (median age, 58 years; age range, 40-74 years) who underwent endorectal MR imaging and MR spectroscopic imaging between January 2000 and December 2002 were included. MR imaging and spectroscopy were performed by using combined pelvic phased-array and endorectal probe. Water and lipids were suppressed, and phase-encoded data were acquired with 6.2-mm resolution. Voxels in the peripheral zone were considered suspicious for cancer if (Cho + Cr)/Cit was at least two standard deviations above the normal level, where Cho represents choline-containing compounds, Cr represents creatine and phosphocreatine, and Cit represents citrate. Correlation between metabolite ratio and four Gleason score groups identified at step-section pathologic evaluation (3 + 3, 3 + 4, 4 + 3, and > or =4 + 4) was assessed with generalized estimating equations.

RESULTS

Data from 94 patients were included. Pathologic evaluation was used to identify 239 lesions. Overall sensitivity of MR spectroscopic imaging was 56% for tumor detection, increasing from 44% in lesions with Gleason score of 3 + 3 to 89% in lesions with Gleason score greater than or equal to 4 + 4. There was a trend toward increasing (Cho + Cr)/Cit with increasing Gleason score in lesions identified correctly with MR spectroscopic imaging. Tumor volume assessed with MR spectroscopic imaging increased with increasing Gleason score.

CONCLUSION

MR spectroscopic imaging measurement of prostate tumor (Cho + Cr)/Cit and tumor volume correlate with pathologic Gleason score. There is overlap between MR spectroscopic imaging parameters at various Gleason score levels, which may reflect methodologic and physiologic variations. MR spectroscopic imaging has potential in noninvasive assessment of prostate cancer aggressiveness.

[methyl-3H]Choline incorporation into MCF7 tumour cells: correlation with proliferation

PURPOSE

The aim of the study was to investigate the intracellular location of [methyl-(3)H]choline in MCF7 tumour cells and to determine the relationship between [methyl-(3)H]choline incorporation and proliferation.

METHODS

Tumour cells were incubated with [methyl-(3)H]choline for 10 min, and then in cold medium to simulate the rapid blood clearance of [methyl-(11)C]choline. Labelled metabolites were then extracted from cells by treating them with organic and aqueous solvents to determine the distribution of tracer between phospholipid and water-soluble metabolite pools. Aqueous extracts were subjected to thin-layer chromatography, ion exchange chromatography and a choline extraction procedure to identify (3)H-containing metabolites. Procedures were carried out on fast- and slow-growing populations of MCF7 cells to determine the relationship between choline incorporation and proliferation.

RESULTS

Only about 5% of [methyl-(3)H]choline was present as phospholipid. [methyl-(3)H]choline incorporation was found to be related to S-phase fraction. In another experiment, [methyl-(14)C]choline incorporation was found to be correlated with [methyl-(3)H]thymidine incorporation. The V(max) of choline uptake was found to be increased whilst K(m) was decreased in populations of MCF7 cells with higher proliferative fractions, compared with populations having lower proliferative fractions.

CONCLUSION

Choline incorporation into tumour cells under conditions that simulate rapid blood clearance of [methyl-(11)C]choline is correlated with proliferation. Most of the activity (about 95%) was in the non-lipid fraction of the cell.

Biochemical characterization of metastatic lymph nodes of breast cancer patients by in vitro 1H magnetic resonance spectroscopy: a pilot study

Using one-dimensional (1D) and two-dimensional (2D) proton nuclear magnetic resonance (NMR) methods, the perchloric acid extract of involved (n = 11) and noninvolved (n = 12) axillary lymph nodes (ALN) of breast cancer patients was investigated. Resonances from 40 metabolites such as lactate (Lac), glucose, several amino acids (alanine, lysine, glutamic acid, glutamine, etc.), nucleotides (adenosine triphosphate, guanosine triphosphate, uridine triphosphate, uridine monophosphate, etc.), membrane metabolites [glycerophosphocholine (GPC), phosphocoline (PC), phosphoethanolamine (PE), choline] were unambiguously assigned in both the involved and noninvolved ALN. The concentration of PC/GPC (p = 0.002) was significantly higher in the involved compared to noninvolved nodes. In addition, the concentration of glycolytic product Lac (p = 0.0001) was also found to be significantly higher in involved nodes. Increased concentration of membrane metabolites PC/GPC may be attributed to increased membrane synthesis in malignant cells and, therefore, suggests the presence of metastatic cells in lymph nodes. The higher concentration of Lac is indicative of the presence of malignant cells that derive energy via anaerobic glycolytic pathway. Present results demonstrate the potentials of in vitro proton NMR in detecting malignant cells in ALN and such studies may have an important bearing in determining the prognosis of breast cancer patients.

Radiolabeled choline as a proliferation marker: Comparison with radiolabeled acetate

[11C]Choline is a potential tracer to detect tumors, especially brain and prostate cancers. The metabolism of [11C]choline defines the accumulation pattern of [11C]choline in tumors depicted by positron emission tomography. Choline is a precursor of phosphatidylcholine that is a major constituent of membrane lipids. Membrane lipid synthesis as well as DNA synthesis is activated during cell proliferation. We investigated the relation between [14C]choline metabolism and proliferative activity using 10 tumor cell lines and fibroblasts. [14C]Choline uptake was higher in tumor cells than in fibroblasts and was correlated with the proliferative activity, though the sensitivity of [14C]choline uptake to proliferative activity was less than that of [1-14C]acetate. [14C]Phosphocholine produced from [14C]choline by phosphorylation mainly contributed to this accumulation. [11C]Choline can be used for the evaluation of tumor proliferation through estimating choline kinase activity.

L-alpha-glycerylphosphorylcholine inhibits the transfer function of phosphatidylinositol transfer protein alpha

Phosphatidylinositol transfer protein alpha (PITP-alpha) is a bifunctional phospholipid transfer protein that is highly selective for phosphatidylinositol (PtdIns) and phosphatidylcholine (PtdCho). Polar lipid metabolites, including L-alpha-glycerylphosphorylcholine (GroPCho), increasingly have been linked to changes in cellular function and to disease. In this study, polar lipid metabolites of PtdIns and PtdCho were tested for their ability to influence PITP-alpha activity. GroPCho inhibited the ability of PITP-alpha to transfer PtdIns or PtdCho between liposomes. The IC(50) of both processes was dependent on membrane composition. D-myo-inositol 1-phosphate and glycerylphosphorylinositol modestly enhanced PITP-alpha-mediated phospholipid transfer. Choline, phosphorylcholine (PCho), CDP-choline, glyceryl-3-phosphate, myo-inositol and D-myo-inositol 1,4,5-trisphosphate had little effect. Membrane surface charge was a strong determinant of the GroPCho inhibition with the inhibition being greatest for highly anionic membranes. GroPCho was shown to enhance the binding of PITP-alpha to anionic vesicles. In membranes of low surface charge, phosphatidylethanolamine (PtdEtn) was a determinant enabling the GroPCho inhibition. Anionic charge and PtdEtn content appeared to increase the strength of PITP-alpha-membrane interactions. The GroPCho-enhanced PITP-alpha-membrane binding was sufficient to cause inhibition, but not sufficient to account for the extent of inhibition observed. Processes associated with strengthened PITP-alpha-membrane binding in the presence of GroPCho appeared to impair the phospholipid insertion/extraction process.

1H magnetic resonance spectroscopy of preinvasive and invasive cervical cancer: In vivo-ex vivo profiles and effect of tumor load

PURPOSE

To compare in vivo (1)H magnetic resonance (MR) spectra of preinvasive and invasive cervical lesions with ex vivo magic angle spinning (MAS) spectra of intact biopsies from the same subjects and to establish the effects of tumor load in the tissue sampled on the findings.

MATERIALS AND METHODS

A total of 51 subjects (nine with normal cervix, 10 with cervical intraepithelial neoplasia [CIN], and 32 with cervical cancer) underwent endovaginal MR at 1.5 T. Single-voxel (3.4 cm(3)) (1)H MR spectra were acquired and voxel tumor load was calculated (tumor volume within voxel as a percentage of voxel volume). Resonances from triglycerides -CH(2) and -CH(3) and choline-containing compounds (Cho) were correlated with voxel tumor load. Biopsies analyzed by (1)H MAS-MR spectroscopy (MRS) had metabolite levels correlated with tumor load in the sample at histology.

RESULTS

In vivo studies detected Cho in normal, CIN, and cancer patients with no significant differences in levels (P = 0.93); levels were independent of voxel tumor load. Triglyceride -CH(2) and -CH(3) signals in-phase with Cho were present in 77% and 29%, respectively, of cancer subjects (but not in normal women or those with CIN), but did not correlate with voxel tumor load. Ex vivo cancer biopsies showed levels of triglycerides -CH(2) and -CH(3) and of Cho that were significantly greater than in normal or CIN biopsies (P < 0.05); levels were independent of the tumor load in the sample. The presence of -CH(2) in vivo predicted the presence of cancer with a sensitivity and specificity of 77.4% and 93.8% respectively, positive (PPV) and negative (NPV) predictive values were 96% and 68.2%; for -CH(2) ex vivo, sensitivity was 100%; specificity, 69%; PPV, 82%; and NPV, 100%.

CONCLUSION

Elevated lipid levels are detected by MRS in vivo and ex vivo in cervical cancer and are independent of tumor load in the volume of tissue sampled.

Characterization of Lesions of the Breast with Proton MR Spectroscopy:Comparison of Carcinomas, Benign Lesions, and Phyllodes Tumors

OBJECTIVE

Proton MR spectroscopy is a recently described technique with high sensitivity and specificity for differentiating breast carcinoma from benign lesions. We evaluated the possible relationship between spectroscopy results and the tumor proliferative index, angiogenesis, and HER2/neu oncogene overexpression. SUBJECTS AND METHODS. We prospectively evaluated 19 breast carcinomas, 21 benign breast lesions (including 18 fibroadenomas, one fibrocystic change, one hamartoma, and one papilloma), and six phyllodes tumors (four benign, two of borderline malignancy) using proton MR spectroscopy. All lesions were larger than 1.5 cm. Tumor Ki-67 proliferative index, tumor angiogenesis, and HER2/neu oncogene overexpression were evaluated by immunohistochemistry of the histologic material.

RESULTS

Spectroscopy findings were positive in 17 (89%) of 19 carcinomas but negative for all benign lesions and phyllodes tumors (sensitivity, 89%; specificity, 100%). Significantly higher levels were obtained for all biologic parameters in carcinomas compared with benign lesions and phyllodes tumors. HER2/neu oncogene overexpression was present in 37% of carcinomas but not in other lesions. The two false-negative findings of breast carcinoma showed similar Ki-67 proliferative index and microvessel density compared with the remaining carcinomas, but both cases were negative for HER2/neu overexpression.

CONCLUSION

Proton MR spectroscopy is useful in the in vivo characterization of breast masses when the lesion exceeds 1.5 cm in maximal dimension. Spectroscopy is unable to reveal benign breast lesions and phyllodes tumors of benign and borderline malignancy. We suggest that a false-negative spectroscopic result may be related to an absence of HER2/neu overexpression in carcinoma of the breast.

Transition zone prostate cancer: metabolic characteristics at 1H MR spectroscopic imaging--initial results

PURPOSE

To determine whether cancers of the prostate transition zone (TZ) possess a unique metabolic pattern by which they may be identified at proton magnetic resonance (MR) spectroscopic imaging.

MATERIALS AND METHODS

Findings in 40 patients who underwent combined endorectal MR imaging and hydrogen 1 MR spectroscopic imaging before radical prostatectomy and who had TZ tumor identified subsequently at step-section pathologic analysis were retrospectively reviewed. Within this population, a subset of 16 patients whose TZ tumor had a largest diameter of 1 cm or greater and was included in the MR spectroscopic imaging excitation volume was identified. In these 16 patients, the ratios of choline-containing compounds (Cho) and creatine/phosphocreatine (Cr) to citrate (Cit) (ie, [Cho + Cr]/Cit), Cho/Cr, and Cho/Cit were compared in tumor and control tissues. The presence of only Cho and the absence of all metabolites were also assessed.

RESULTS

The mean values of (Cho + Cr)/Cit, Cho/Cr, and Cho/Cit were different between TZ cancer and control tissues (P =.001, P =.003, and P =.001, respectively; Wilcoxon signed rank test). Nine (56%) of 16 patients had at least one tumor voxel in which Cho comprised the only detectable peak, while no control voxels showed only Cho (P =.008, McNemar test). The percentage of voxels in which no metabolites were detected did not differ between tumor and control tissues (P =.134, McNemar test).

CONCLUSION

TZ cancer has a metabolic profile that is different from that of benign TZ tissue; however, the broad range of metabolite ratios observed in TZ cancer precludes the use of a single ratio to differentiate TZ cancer from benign TZ tissue.

Noninvasive estimation of tumour viability in a xenograft model of human neuroblastoma with proton magnetic resonance spectroscopy (1H MRS)

The aim of the study was to evaluate proton magnetic resonance spectroscopy ((1)H MRS) for noninvasive biological characterisation of neuroblastoma xenografts in vivo. For designing the experiments, human neuroblastoma xenografts growing subcutaneously in nude rats were analysed in vivo with (1)H MRS and magnetic resonance imaging at 4.7 T. The effects of spontaneous tumour growth and antiangiogenesis treatment, respectively, on spectral characteristics were evaluated. The spectroscopic findings were compared to tumour morphology, proliferation and viable tumour tissue fraction. The results showed that signals from choline (Cho)-containing compounds and mobile lipids (MLs) dominated the spectra. The individual ML/Cho ratios for both treated and untreated tumours were positively correlated with tumour volume (P<0.05). There was an inverse correlation between the ML/Cho ratio and the viable tumour fraction (r=-0.86, P<0.001). Higher ML/Cho ratios concomitant with pronounced histological changes were seen in spectra from tumours treated with the antiangiogenic drug TNP-470, compared to untreated control tumours (P<0.05). In conclusion, the ML/Cho ratio obtained in vivo by (1)H MRS enabled accurate assessment of the viable tumour fraction in a human neuroblastoma xenograft model. (1)H MRS also revealed early metabolic effects of antiangiogenesis treatment. (1)H MRS could prove useful as a tool to monitor experimental therapy in preclinical models of neuroblastoma, and possibly also in children.

Phosphorous metabolites and steady-state energetics of transformed fibroblasts during three-dimensional growth

Rat1-T1 and MR1 spheroids represent separate transformed phenotypes originated from the same rat fibroblasts that differ in three-dimensional (3D) growth kinetics, histological structure, and oxygenation status. In the present study, (31)P-NMR spectroscopy of perfused spheroid suspensions was used to investigate cellular energetics relative to 3D growth, development of necrosis, and cell cycle distribution. Both spheroid types were characterized by a remarkably low amount of free (inorganic) phosphate (P(i)) and a low phosphocreatine peak. The ratio of nucleoside triphosphate (NTP) to P(i) ranged between 1.5 and 2.0. Intracellular pH, NTP-to-P(i) ratio, and NTP/cell remained constant throughout spheroid growth, being unaffected by the emergence of oxygen deficiency, cell quiescence, and necrosis. However, a 50% decrease in the ratio of the lipid precursors phosphorylcholine and phosphorylethanolamine (PC/PE) was observed with increasing spheroid size and was correlated with an increased G(1)/G(0) phase cell fraction. In addition, the ratio of the phospholipid degradation products glycerophosphorylcholine and glycerophosphorylethanolamine (GPC/GPE) increased with spheroid diameter in Rat1-T1 aggregates. We conclude that changes in phospholipid metabolism, rather than alterations in energy-rich phosphates, reflect cell quiescence in spheroid cultures, because cells in the inner oxygen-deficient zones seem to adapt their energy metabolism to the environmental conditions before necrotic cell destruction.

Use of radiolabelled choline as a pharmacodynamic marker for the signal transduction inhibitor geldanamycin

There is an urgent need to develop non-invasive pharmacodynamic endpoints for the evaluation of new molecular therapeutics that inhibit signal transduction. We hypothesised that, when labelled appropriately, changes in choline kinetics could be used to assess geldanamycin pharmacodynamics, which involves inhibition of the HSP90 molecular chaperone-->Raf1-->Mitogenic Extracellular Kinase-->Extracellular Signal-Regulated Kinase 1 and 2 signal transduction pathway. Towards identifying a potential pharmacodynamic marker response, we have studied radiolabelled choline metabolism in HT29 human colon carcinoma cells following treatment with geldanamycin. We studied the effects of geldanamycin, on net cellular accumulation of (methyl-(14)C)choline and (methyl-(14)C)phosphocholine production. In parallel experiments, the effects of geldanamycin on extracellular signal-regulated kinase 1 and 2 phosphorylation and cell viability were also assessed. Additional validation studies were carried out with the mitogenic extracellular kinase inhibitor U0126 as a positive control; a cyclin-dependent kinase-2 inhibitor roscovitine and the phosphatidylinositol 3-kinase inhibitor LY294002 as negative controls. Hemicholinium-3, an inhibitor of choline transport and choline kinase activity was included as an additional control. In exponentially growing HT29 cells, geldanamycin inhibited extracellular signal-regulated kinase 1 and 2 phosphorylation in a concentration- and time-dependent manner. These changes were associated with a reduction in (methyl-(14)C)choline uptake, (methyl-(14)C) phosphocholine production and cell viability. Brief exposure to U0126, suppressed phosphocholine production to the same extent as Hemicholinium-3. In contrast to geldanamycin and U0126, which act upstream of extracellular signal-regulated kinase 1 and 2, roscovitine and LY294002 failed to suppress phosphocholine production. Our results suggest that when labelled with carbon-11 isotope, (methyl-(11)C)choline may be a useful pharmacodynamic marker for the non-invasive evaluation of geldanamycin analogues.

Exposure of human breast cancer cells to the anti-inflammatory agent indomethacin alters choline phospholipid metabolites and Nm23 expression

We previously observed that changes in choline phospholipids of two malignant human mammary epithelial cells (HMECs) following treatment with a high dose of the cyclooxygenase (COX) inhibitor, indomethacin, mimicked changes following transfection with a metastasis suppressor gene, nm23. The similarity between response to indomethacin and nm23 transfection led us to 1) expand our (1)H NMR spectroscopy study of indomethacin treatment by determining the response at two doses for two nonmalignant and three malignant HMECs, 2) investigate COX-1 and COX-2 levels in HMECs and their relationship with choline phosholipid metabolites, and 3) determine changes in Nm23 expression following treatment with indomethacin. All HMECs exhibited a significant change in choline phospholipids following treatment with 300 microM indomethacin. At the lower dose of 50 microM, only nonmalignant HMECs and the estrogen-dependent malignant cell line, MCF-7, responded. COX-1 levels were significantly higher in malignant HMECs than in nonmalignant HMECs. A significant increase in Nm23 expression following 300 microM indomethacin was detected in MCF-12A and MCF-7 cells but not in MDA-MB-231 and MDA-MB-435 cells. These results suggest that COX-1 expression and its inhibition play a role in the choline phospholipid metabolism of HMECs, and the effect of indomethacin on HMECs may be mediated, in part, through upregulation of nm23.

Biochemical characterization of pediatric brain tumors by using in vivo and ex vivo magnetic resonance spectroscopy

OBJECT

Magnetic resonance (MR) spectroscopy provides biochemical information about tumors. The authors sought to determine the relationship between in vivo and ex vivo biochemical characterization of pediatric brain tumors by using MR spectroscopy. Their hypothesis was that ex vivo MR spectroscopy provides a link between in vivo MR spectroscopy and neuropathological analysis.

METHODS

In vivo proton MR spectroscopy was performed before surgery in 11 patients with neuroepithelial tumors. During resection, a total of 40 tumor biopsy samples were obtained from within the volume of interest identified on in vivo MR spectroscopy and were frozen immediately in liquid nitrogen. High-Resolution Magic Angle Spinning (HRMAS) was used to perform ex vivo MR spectroscopy in these 40 tumor biopsy samples. Neuropathological analysis was performed using the same biopsy samples, and the tumors were classified as ependymoma, choroid plexus carcinoma, pineoblastoma (one each), and pilocytic astrocytoma, medullobastoma, low-grade glioma, and glioblastoma multiforme (two each). Ex vivo HRMAS MR spectroscopy improved line widths and line shapes in the spectra, compared with in vivo MR spectroscopy. Choline (Cho) detected in vivo corresponded to three different peaks ex vivo (glycerophosphocholine, phosphocholine [PCho], and Cho). Metabolite ratios from in vivo spectra correlated with ratios from ex vivo spectra (Pearson correlation coefficient range r = 0.72-0.91; p < or = 0.01). Metabolite ratios from ex vivo spectra, such as PCho/ total creatine (tCr) and lipid/tCr, correlated with the percentage of cancerous tissue and percentage of tumor necrosis, respectively (r = 0.84; p < 0.001).

CONCLUSIONS

Agreement between in vivo and ex vivo MR spectroscopy indicates that ex vivo HRMAS MR spectroscopy can improve resolution of this modality and provide a link between in vivo MR spectroscopy and neuropathological analysis.

1H NMR visible lipids are induced by phosphonium salts and 5-fluorouracil in human breast cancer cells

Cationic lipophilic phosphonium salts (CLPS) selectively accumulate in the mitochondria of neoplastic cells and inhibit mitochondrial function. The effects of the CLPS p-(triphenylphosphoniummethyl) benzaldehyde chloride (drug A), and [4-(hydrazinocarboxy)-1-butyl] tris-(4-dimethylaminophenyl) phosphonium chloride (drug B), on human breast cells of differing biological properties were assessed using growth inhibition assays and 1H NMR. Drug A and, to a lesser extent, drug B demonstrated selective growth inhibition of the highly tumorigenic DU4475 breast carcinoma cell line compared to the transformed HBL-100 human breast cell line. However, in contrast to previous studies using other cell lines, no synergistic activity was found when the drugs were used in combination. 1H NMR demonstrated significant increases in mobile lipid acyl chain resonances in both cell lines treated with cytotoxic doses (IC50, 48 h) of the drugs used either alone or in combination. Two-dimensional NMR revealed accompanying decreases in phosphocholine/Lys levels in HBL-100 cells treated with A, B, or a 1:1 combination A+B at the IC50, and in DU4475 cells treated with drug A (IC50). This was accompanied by significant increases in cho/Lys ratios with IC50 A or combination A+B treatment. Similar spectra were observed in cells treated with 5-fluorouracil but not methotrexate, indicating that mobile lipid accumulation is a general but not universal response to cytotoxic insult.

Evaluation of total choline from in-vivo volume localized proton MR spectroscopy and its response to neoadjuvant chemotherapy in locally advanced breast cancer

Results of the proton magnetic resonance spectroscopy carried out on normal, benign breast disease and locally advanced breast cancer patients are presented. The in-vivo MR spectra of malignant breast tissue of patients (n = 67) suffering from infiltrating ductal carcinoma are dominated by the water resonance, while the spectra of the unaffected contralateral breast tissue of these patients are mainly dominated by resonance arising from lipids which is similar to the spectra of normal breast tissue obtained from volunteers (controls, n = 16). In addition to the water and lipid peaks, in majority of the patients (approximately 80%) the water suppressed spectra showed a resonance at 3.2 ppm due to choline containing compounds (TCho) before treatment. In patients receiving neoadjuvant chemotherapy, absence/reduction in choline was observed in 89% of the patients. TCho was also observed in 2 of 14 benign lesions. The sensitivity and specificity of in-vivo MRS in detecting TCho in malignant tumours was 78% and 86%, respectively. Observation of TCho before treatment and its disappearance (or reduction) after treatment may be a useful indicator of response of locally advanced breast cancer to neoadjuvant chemotherapy.

Magnetic resonance detects changes in phosphocholine associated with Ras activation and inhibition in NIH 3T3 cells

Ras is frequently mutated in cancer, and novel therapies are being developed to target Ras signalling. To identify non-invasive surrogate markers of Ras activation and inhibition, we used(31)P magnetic resonance spectroscopy (MRS) and investigated NIH 3T3 cells compared to a mutant ras transfected counterpart. The MR spectra indicated that phosphocholine (PC) levels increased significantly from 3 +/- 2 fmol cell(-1)in NIH 3T3 cells to 13 +/- 4 fmol cell(-1)in the transfected cells. The PC/NTP ratio increased significantly from 0.3 +/- 0.1 to 0.7 +/- 0.3. This could not be explained by either a faster proliferation rate or by alterations in cell cycle distribution. Both cell lines were treated with simvastatin, 17-AAG and R115777, agents which inhibit Ras signalling. Cell proliferation was inhibited in both cell lines. The spectrum of NIH 3T3 cells was not affected by treatment. In contrast, in the ras transfected cells growth inhibition was associated with an average 35 +/- 5% drop in PC levels and a comparable drop in PC/NTP. Thus the MRS visible increase in phosphocholine is associated with Ras activation, and response to treatment is associated with partial reversal of phosphocholine increase in ras transfected cells. MRS might therefore be a useful tool in detecting Ras activation and its inhibition following targeted therapies.

Tumour phospholipid metabolism

Following the impetus of early clinical and experimental investigations, in vivo and in vitro MRS studies of tumours pointed in the eighties to the possible significance of signals arising from phospholipid (PL) precursors and catabolites as novel biochemical indicators of in vivo tumour progression and response to therapy. In the present decade, MRS analyses of individual components contributing to the 31P PME (phosphomonoester) and PDE (phosphodiester) resonances, as well as to the 1H 'choline peak', have reinforced some of these expectations. Moreover, the absolute quantification of these signals provided the basis for addressing more specific (although still open) questions on the biochemical mechanisms responsible for the formation of intracellular pools of PL derivatives in tumours, under different conditions of cell proliferative status and/or malignancy level. This article is aimed at providing an overview on: (a) quantitative MRS measurements on the contents of phosphocholine (PCho), phosphoethanolamine (PEtn) and their glycerol derivatives ģlycerol 3-phosphocholine (GPC) and glycerol 3-phosphoethanolamine (GPE)[ in human tumours and cells (with particular attention to breast and brain cancer and lymphomas), as well as in normal mammalian tissues (including developing organs and rapidly proliferating tissues); (b) possible correlations of MRS parameters like PEtn/PCho and PCho/GPC ratios with in vitro cell growth status and/or cell tumorigenicity; and (c) current and new hypotheses on the role and interplay of biosynthetic and catabolic pathways of the choline and ethanolamine cycles in modulating the intracellular sizes of PCho and PEtn pools, either in response to mitogenic stimuli or in relation to malignant transformation.

Measurements of human breast cancer using magnetic resonance spectroscopy: a review of clinical measurements and a report of localized 31P measurements of response to treatment

A review of the literature has shown that in human breast tumours, large signals from phosphomonoesters (PME) and phosphodiesters (PDE) are evident. In serial measurements in 19 patients with breast cancer, a decrease in PME was significantly associated with a stable or responding disease (p = 0.017), and an increase in PME was associated with disease progression. Extract studies have shown PME to comprise of phosphoethanolamine (PEth) and phosphocholine (PCho), with the PEth to PCho ratio ranging from 1.3 to 12. The PCho content of high grade tumours was found to be higher than low grade tumours. In some animal models, changes in PCho have been shown to correlate with indices of cellular proliferation, and spheroid studies have shown a decrease in PCho content in spheroids with smaller growth fractions. A serial study of 25 patients with advanced primary breast tumours undergoing hormone, chemotherapy or radiotherapy treatments, showed that in this heterogenous group there were significant changes in metabolites that were seen during the first 3 weeks (range 2-4 weeks) of treatment, that correlated with volume change over this period, employed here as a measure of response. Changes in PME (p = 0.003), total phosphate (TP) (p = 0.008) and total nucleoside tri-phosphate (TNTP) (p = 0.02) over 3 (+/-1) weeks were significantly associated with response, as were the levels of PME (p<0.001), PDE (p = 0.01), TP (p = 0.001) and TNTP (p = 0.007) at week 3 (+/-1). PME at week 3 (+/-1) was also significantly associated with the best volume response to treatment (p = 0.03). A reproducibility analysis of results from the observation of normal breast metabolism in four volunteers showed a mean coefficient of variation of 25%, after correcting for changes resulting from the menstrual cycle. Reproducibility studies in four patients with breast cancer showed a mean coefficient of variation of 33%, with the reproducibility being better in patients measured on different days (difference in TP was -6%) compared with those measured on the same day (difference in TP was -29%).

Metabolic changes underlying 31P MR spectral alterations in human hepatic tumours

Magnetic resonance spectroscopy (MRS) remains the technique of choice for observing tumour metabolism non-invasively. Although initially 31P MR spectroscopy showed much promise as a non-invasive diagnostic tool, studies of a wide range of hepatic tumours have conclusively shown that this technique cannot be utilized to distinguish between different tumour types. This lack of specificity and sensitivity appears to be a consequence of the fact that hepatic tumours develop with a range of modalities and not as a single abnormal disease process, and also because of the limited availability of MR detectable metabolic markers. This has led, in recent years, to a re-evaluation of the role of 31P MR spectroscopy, re-emerging as a non-invasive tool to follow the efficacy of the treatment regime. Furthermore, since the principal changes observed in tumours by 31P MRS appear to be an elevation in the concentration of phosphorylcholine (PCho) and phosphoethanolamine (PEth), new research using a combination of MRS and tissue culture of cell lines which carry a combination of known inducible oncogenes, are helping to elucidate some of the metabolic pathways that give rise to these metabolic alterations.

TNF-induced modulations of phospholipid metabolism in human breast cancer cells

Tumor necrosis factor alpha (TNF) is a cytokine that is cytocidal for certain tumor cells and induces necrotic and apoptotic forms of cell death. Flow cytometry and transmission electron microscopy analysis demonstrated that in human breast cancer cells (MCF7) TNF induces cell cycle arrest in G0+G1/S, accompanied by apoptosis. 31P and 13C NMR spectroscopy was applied to study cellular metabolism of MCF7 cells during TNF-induced signal to apoptosis. Deuterated choline and 2H NMR spectroscopy were utilized to monitor the kinetics of the rate limiting reactions in phosphocholine metabolism. The NMR measurements revealed that immediately after administration of TNF, choline transport was inhibited by 52+/-6%. Later (approximately 15 h), the activity of phosphocholine:cytidine triphosphate cytidylyltransferase, a key enzyme in the biosynthesis of phosphatidylcholine, was enhanced two-fold. These two opposing changes led to a decrease in the level of phosphocholine. Throughout these changes the energetic state of the cells, determined by the level of nucleoside triphosphates and the rate of glucose metabolism via glycolysis, remained constant. The results indicate that TNF specifically modulates the kinetics of membrane-bound enzymes of the rate determining steps in phosphatidylcholine biosynthesis, possibly as part of early events involved in apoptosis.

1H MRS markers of tumour growth in intrasplenic tumours and liver metastasis induced by injection of HT-29 cells in nude mice spleen

We have characterized, by in vitro magnetic resonance spectroscopy (MRS), the metabolite pattern of perchloric acid (PCA) extracts of intrasplenic tumours and hepatic metastasis, produced by intra-spleen injection of the human colorectal carcinoma cell line HT-29 and its metastatic variant HT-29 MMM into nude mice. Our aim was to gain further understanding of colorectal tumour metabolism as a basis for future in vivo studies of human colon cancer by 1H MRS. Metabolite PCA extract analysis showed a good reproduction of the spectral pattern observed in human primary colon tumours, while they were very different from the spectral pattern of the host tissues (spleen and liver). The main differences between host and tumour tissues involved taurine, phosphocholine (PC), phosphoethanolamine (PE), creatine, glycogen and glucose. Creatine is the most promising marker to follow tumour growth because of its practical absence in the nude mice host tissues. Detection of variable levels of this compound and of taurine in hepatic foci in man, are suggested as possible diagnostic markers. No correlation could be found between spectral pattern differences and the different ability to metastasize of the two HT-29 cell lines used. Furthermore, indirect evidence for a functional link between taurine and myo-inositol in colon tumour cells is presented. In summary, our data suggest that the nude mice model may be a suitable system for the MRS study of the changes taking place in host tissues upon tumour progression.

In vivo and ex vivo study of metabolic and cellular effects of 5-fluorouracil chemotherapy in a mouse mammary carcinoma

The effect of 5-fluorouracil (5FU) on the 31P nuclear magnetic resonance (NMR) profile of a mouse mammary carcinoma, implanted on the foot of CH3/He mice, was studied both in vivo and in perchloric acid extracts. In vivo, significant increases in the ratios, nucleotide triphosphate:inorganic phosphate (Pi) (p < 0.02) and phosphocreatine:Pi (p < 0.005), were observed 48 h after 5FU, relative to control. Two readily resolvable peaks were observed in the phosphomonoester region of the in vivo NMR spectrum, phosphocholine (PC) and a peak (denoted PME') comprised of mainly phosphoethanolamine (PE). PME':PC was significantly elevated relative to control from 24 h to 168 h (p < 0.0001 at 48 h). Perchloric acid extract data indicate that the change in this ratio was due to an increase in the PE concentration rather than a decrease in PC. PE increased from 0.56 +/- 0.11 micromol/g tissue in controls to 0.95 +/- 0.29 micromol/g tissue 48 h after 5FU (p < 0.006). Perchloric acid extracts also revealed a significant increase in phosphodiesters. Glycerophosphocholine increased from 0.82 +/- 0.24 micromol/g tissue in controls to 1.82 +/- 0.61 micromol/g tissue in 5FU treated tumors after 48 h (p < 0.002), and glycerophosphoethanolamine increased from 0.25 +/- 0.06 micromol/g tissue in controls to 0.36 +/- 0.10 micromol/g tissue in treated tumors (p < 0.004). These changes suggest that ethanolamine and choline containing metabolites in this tumor may be metabolized via different pathways. Cell cycle analysis showed only relatively small changes in cell cycle distribution and apoptotic fraction following 5FU.

In vivo 31P MRS evaluation of ganciclovir toxicity in C6 gliomas stably expressing the herpes simplex thymidine kinase gene

Phosphorus MRS was evaluated as a monitor of tumour therapeutic response to the herpes simplex virus thymidine kinase suicide gene therapy paradigm. In vivo 31P spectra were obtained from subcutaneous rat C6 gliomas constitutively expressing the HSVtk gene post treatment with ganciclovir (GCV, 15 mg/kg i.p., twice-daily). Significant regression (p < 0.1) of tumour volume was observed 10 days after beginning GCV administration. However, no changes in tumour pH or energy metabolites from pre-treatment values were observed. High-resolution 31P spectra of tumour extracts revealed a statistically significant reduction in the phosphocholine to phosphoethanolamine ratio six days post-GCV administration. These results indicate that the HSVtk/GCV-induced killing of tumours is not associated with corresponding changes in 31P MRS-observable energy metabolites and pH. The observed reduction in the PE/PC ratio may provide a non-invasive in vivo indicator of therapeutic efficacy.

Effects of blood flow modifiers on tumor metabolism observed in vivo by proton magnetic resonance spectroscopic imaging

Perfusion plays a key role in tumor proliferation and therapeutic response. Tumor heterogeneity necessitates use of the highest spatial resolution to monitor metabolic correlates of blood flow changes. This is best achieved with 1H NMR spectroscopy, which permits noninvasive acquisition of high resolution spectroscopic images (SI) of subcutaneous tumors in a relatively short scan time (e.g., 12-25 microliters voxels with signal-to-noise ratio 7:1 in 30 min at 4.7 T). This study seeks to identify 1H spectroscopic indices of tumor blood flow. Proton SI of subcutaneous murine RIF-1 tumors were recorded (a) before and after administration of nicotinamide (1 g/kg) to increase blood flow, and (b) before and after hydralazine (10 mg/kg) to decrease flow. Nicotinamide produced a significant decrease in the total choline peak amplitudes, which subsequent high resolution NMR spectroscopy of tumor extracts revealed to be due to decreases in phosphocholine and glycerophosphocholine. The deamidation of nicotinamide to nicotinic acid, which is known to have hypolipidemic effects and to stimulate the formation of prostaglandins, may have sufficiently altered lipid metabolism to affect the in vivo concentration of the NMR-visible choline-containing compounds. The main effect of hydralazine was a significant increase of lactate, which is consistent with a reduction of tumor blood flow.

Quantitative and qualitative characterization of 1H NMR spectra of colon tumors, normal mucosa and their perchloric acid extracts: decreased levels of myo-inositol in tumours can be detected in intact biopsies

Sixteen colonic tumours and 10 normal mucosa biopsies have been examined by 1H NMR spectroscopy at 9.4 T. A complete characterization and quantification of the aliphatic region of PCA extract spectra and the analysis of the two-dimensional COSY spectra of five pairs of intact biopsies (tumor and control mucosa) has been carried out. The analysis of the PCA extracts demonstrated a significant increase in the concentration of the endogenous compounds: lactate, glutamate, aspartate, taurine, spermine, glutathione and glycerophosphoethanolamine, and a significant decrease of myo- and scyllo-inositol, in tumours with respect to mucosae. Among these metabolites, the high myo-inositol and taurine levels and the reciprocal changes found between them in tumours and mucosae make their resonances interesting as possible malignancy markers if they are detectable in vivo. In contrast to the easy observation of taurine in one-dimensional spectra of intact biopsies, the difficulty of observing myo-inositol prompted us to use two-dimensional COSY spectra for the detection and quantification of both these metabolites. In the two-dimensional spectra, the use of a ratio between the cross-peak volumes of both metabolites permits an excellent differentiation between tumours and normal mucosa and suggests its potential to detect malignant changes in the healthy tissue, provided a two-dimensional approach is used.

Modulation of MR-visible mobile lipid levels by cell culture conditions and correlations with chemotactic response

A transformed murine fibroblast cell line has been used to assess which criteria govern the appearance of a lipid pool that is mobile on the MR time scale. A high-resolution proton MR signal arising from neutral lipids, including triglyceride and cholesteryl esters, has previously been associated with membrane events in stimulated, transformed and malignant cells. We report that the attenuation of cellular proliferation by confluence or low pH caused significant increases in MR-visible lipid and that the lipid signal could be amplified at high density by the removal of serum. A significant decrease in chemotactic response accompanied the culture of cells at high density, but chemotactic response was not generally linked to alteration of the lipid signal. The appearance of the signal was also not correlated with the proportion of cells in any phase of the cell cycle. Significant changes in the MR-visible pools of the lipid metabolites choline, phosphocholine and glycerophosphocholine were measured under the culture conditions employed with 2D MRS and suggest that MR-visible lipid may arise from the catabolism of phospholipids.

31P NMR spectroscopy studies of phospholipid metabolism in human melanoma xenograft lines differing in rate of tumour cell proliferation

The concentration of phospholipid metabolites in tumours has been hypothesized to be related to rate of cell membrane turnover and may reflect rate of cell proliferation. The purpose of the study reported here was to investigate whether 31P NMR resonance ratios involving the phosphomonoester (PME) or phosphodiester (PDE) resonance are correlated to fraction of cells in S-phase or volume-doubling time in experimental tumours. Four human melanoma xenograft lines (BEX-t, HUX-t, SAX-t, WIX-t) were included in the study. The tumours were grown subcutaneously in male BALB/c-nu/nu mice. 31P NMR spectroscopy was performed at a magnetic field strength of 4.7 T. Fraction of cells in S-phase was measured by flow cytometry. Tumour volume-doubling time was determined by Gompertzian analysis of volumetric growth data. BEX-t and SAX-t tumours differed in fraction of cells in S-phase and volume-doubling time, but showed similar 31P NMR resonance ratios. BEX-t and WIX-t tumours showed significantly different 31P NMR resonance ratios but similar fractions of cells in S-phase. The 31P NMR resonance ratios were significantly different for small and large HUX-t tumours even though fraction of cells in S-phase and volume-doubling time did not differ with tumour volume. None of the 31P NMR resonance ratios showed significant increase with increasing fraction of cells in S-phase or significant decrease with increasing tumour volume-doubling time across the four xenograft lines.(ABSTRACT TRUNCATED AT 250 WORDS)

Hormone dependence of breast cancer cells and the effects of tamoxifen and estrogen: 31P NMR studies

Many breast tumors appear to progress from estrogen-dependent growth to a more malignant phenotype characterized by estrogen-independent growth, antiestrogen resistance, and a high metastatic potential. Utilizing 31P NMR spectroscopy on human breast cancer cells growing in vitro, we have investigated the effects of 17 beta-estradiol and tamoxifen on the metabolic/bioenergetic spectra of a series of human breast cancer cells that vary in their estrogen and antiestrogen responsiveness. A comparison of baseline spectra associates higher levels of phosphodiesters and UDP-glucosides (e.g. UDP-glucose, UDP-N-acetylglucosamine), and lower phosphocholine/glycerylphosphocholine and phosphocholine/phosphoethanolamine ratios, with the acquisition of estrogen-independent growth in estrogen receptor expressing cells. No metabolic changes are clearly associated with the metastatic phenotype. Whilst estrogen treatment produces no consistently significant spectral changes in any of the cell lines, the estrogen-independent and estrogen-responsive MCF7/MIII cell line responds to tamoxifen treatment by significantly increasing all spectral resonances 30%-40% above baseline values. This may reflect a tamoxifen-induced change to a more differentiated or apoptotic phenotype, or an attempt by the cells to reverse the inhibitory effects of the drug. The ability to detect metabolic changes in response to tamoxifen by NMR spectroscopy may provide a novel means to identify those tumors that are responsive to antiestrogen therapy.