Studies of human tumors by MRS: a review

Relationship between 31P metabolites and oncolytic viral therapy sensitivity in human colorectal cancer xenografts

Background

Studies using phosphorus magnetic resonance spectroscopy (MRS) have pointed to the significance of phospholipid metabolite alterations as biochemical markers for tumour progression or therapy response.

Methods

Spectroscopic imaging was performed in colorectal flank tumours in nude mice. In vivo tumour doubling times for each cell line were measured. In vivo sensitivity of each tumour line to treatment with G207 and NV1020 oncolytic viruses was assessed. Correlations between viral sensitivity and tumour doubling time and phosphorus MRS were estimated.

Results

For G207 virus, in vitro cytotoxicity tests showed cell viability at multiplicities of infection (ratio of viral particles per tumour cell) of 0·1 on day 6 as follows: C85, less than 1 per cent; HCT8, 1 per cent; LS174T, 9 per cent; HT29, 18 per cent; and C18, 92 per cent. Respective values for NV1020 were 1, 18, 4, 18 and 86 per cent. The phosphoethanolamine to phosphocholine ratio was significantly lower in virus-sensitive than -insensitive cells, and was dependent on tumour doubling time.

Conclusion

Alterations in membrane phospholipid metabolites that relate to proliferation of cancer cells affect the efficacy of oncolytic viral therapy. MRS proved a highly sensitive non-invasive tool for predicting the efficacy of viruses.

Changes in choline metabolism as potential biomarkers of phospholipase C{gamma}1 inhibition in human prostate cancer cells

Phosphoinositide-specific phospholipase Cγ1 (PLCγ1) is activated downstream of many receptor tyrosine kinases to promote cell motility. Inhibition of this protein is being explored as a therapeutic strategy for blocking cancer cell invasion and metastasis. The clinical development of such cytostatic therapies requires the implementation of pharmacodynamic biomarkers of target modulation. In this study, we use magnetic resonance spectroscopy to explore metabolic biomarkers of PLCγ1 down-regulation in PC3LN3 prostate cancer cells. We show that inhibition of PLCγ1 via an inducible short hairpin RNA system causes a reduction in phosphocholine levels by up to 50% relative to the control as detected by (1)H and (31)P magnetic resonance spectroscopy analyses. This correlated with a rounded-up morphology and reduced cell migration. Interestingly, the fall in phosphocholine levels was not recorded in cells with constitutive PLCγ1 knockdown where the rounded-up phenotype was no longer apparent. This study reveals alterations in metabolism that accompany the cellular effects of PLCγ1 knockdown and highlights phosphocholine as a potential pharmacodynamic biomarker for monitoring the action of inhibitors targeting PLCγ1 signaling.

Imaging of desmoplastic infantile ganglioglioma: a spectroscopic viewpoint

PURPOSE

Desmoplastic infantile gangliogliomas (DIG) are rare benign intracranial neoplasms of early childhood with involvement of superficial cerebral cortex and leptomeninges. The purpose of the study was to determine the alterations in metabolite ratios occurring in the neoplasm and combine with magnetic resonance (MR) imaging features to narrow down the diagnosis.

METHODS

MR imaging sequences include T1- and T2-weighted sequences, fluid-attenuated inversion recovery sequences, and post-gadolinium-contrast T1-weighted imaging. Single-voxel short TE (1)H MR spectroscopy was used to study the changes in metabolite ratios in the tumor.

RESULTS

Comparison of metabolite ratios between normal brain tissue and tumor-affected region showed lower N-acetyl aspartate to creatine (Cr; 1.58 vs.1.28), higher choline to Cr (0.82 vs.2.03), and no significant change in myo-inositol to Cr (0.42 vs.0.39).

CONCLUSION

MR spectroscopy and imaging provide valuable information in the diagnosis of DIG.

In vivo (1)H MRS of WSU-DLCL2 human non-Hodgkin's lymphoma xenografts: response to rituximab and rituximab plus CHOP

In order to identify early (1)H MRS metabolic markers of response to rituximab immunotherapy and to rituximab plus CHOP (cyclophosphamide, hydroxydoxorubicin, vincristine, and prednisone) combination therapy, we performed an in vivo MRS investigation of a non-Hodgkin's lymphoma (NHL) xenograft model. Human WSU-DLCL2 NHL cells were subcutaneously implanted into flanks of female severe combined immunodeficient mice. When tumor volumes reached approximately 600 mm(3), rituximab was administered for three weekly cycles at a dose of 25 mg/kg per cycle with or without CHOP. Before and after treatment, tumor lactate (Lac) and total choline (tCho) were detected using the selective multiple quantum coherence sequence and the stimulated echo acquisition mode sequence, respectively. Rituximab produced a small tumor growth delay ( approximately 5 days), whereas treatment with rituximab plus CHOP (RCHOP) led to approximately 20% tumor regression after three cycles of therapy. After one cycle of rituximab, the tCho/H(2)O ratio had decreased significantly (5%, P = 0.003), whereas the Lac/H(2)O ratio had not changed (P = 0.58). Both Lac/H(2)O and tCho/H(2)O had decreased after one cycle of RCHOP treatment (26%, P = 0.001; 10%, P = 0.016, respectively). After two cycles of RCHOP, Ki67 assay of histological tumor specimens indicated approximately 40% decrease in proliferation (P < 0.001) in the RCHOP-treated tumors; no change was detected after treatment with rituximab alone. This study suggests that decreases in tCho/H(2)O are more sensitive indices of response to rituximab, whereas decreases in Lac/H(2)O are more sensitive to response to CHOP combination therapy.

Optimization of automated large-scale production of [(18)F]fluoroethylcholine for PET prostate cancer imaging

INTRODUCTION

PET tumor imaging is gaining importance in current clinical practice. FDG-PET is the most utilized approach but suffers from inflammation influences and is not utilizable in prostate cancer detection. Recently, (11)C-choline analogues have been employed successfully in this field of imaging, leading to a growing interest in the utilization of (18)F-labeled analogues: [(18)F]fluoroethylcholine (FEC) has been demonstrated to be promising, especially in prostate cancer imaging. In this work we report an automatic radiosynthesis of this tracer with high yields, short synthesis time and ease of performance, potentially utilizable in routine production sites.

METHODS

We used a Modular Lab system to automatically perform the two-step/one-pot synthesis. In the first step, we labeled ethyleneglycolditosylate obtaining [(18)F]fluoroethyltosylate; in the second step, we performed the coupling of the latter intermediate with neat dimethylethanolamine. The final mixture was purified by means of solid phase extraction; in particular, the product was trapped into a cation-exchange resin and eluted with isotonic saline.

RESULTS

The optimized procedure resulted in a non decay corrected yield of 36% and produced a range of 30-45 GBq of product already in injectable form. The product was analyzed for quality control and resulted as pure and sterile; in addition, residual solvents were under the required threshold.

CONCLUSION

In this work, we present an automatic FEC radiosynthesis that has been optimized for routine production. This findings should foster the interest for a wider utilization of this radiomolecule for imaging of prostate cancer with PET, a field for which no gold-standard tracer has yet been validated.

Dermatofibrosarcoma protuberans of the breast: mammographic, ultrasound, MRI and MRS features

Dermatofibrosarcoma protuberans (DFSP) of the breast is a rare malignant tumor, and its preoperative diagnosis is extremely difficult. Local recurrence of DFSP is frequent after incomplete resection because of either false diagnosis or inadequate standard surgical excision. We present a case of DFSP that showed disconcordant results using different imaging modalities, suggesting that the MRI finding of subcutaneously located highly vascular tumor with suspicious kinetics but together with negative Cho peak on (1H) MRS, might be suggestive of the diagnosis of DFSP.

Efficient 1H to 31P polarization transfer on a clinical 3T MR system

31P MR spectroscopy (MRS) in the detection of phosphocholine (PC), glycerolphosphocholine (GPC), phosphorylelthanolamine (PE), and glycerolphosphoethanolamine (GPE) compounds has shown clinical potential at 1.5T for several human diseases. The use of (1)H to (31)P polarization transfer can improve the sensitivity using a refocused INEPT method with a potential enhancement of 2.4 (gamma(1H)/gamma(31P)). However, in this method the (31)P signals of PE, PC, GPE, and GPC are strongly attenuated (50% or more) due to J-coupling between (31)P and (1)H that have similar magnitudes for homonuclear J-coupling constants in those metabolites. A method to cancel the homonuclear J-coupling effects in polarization transfer experiments is to apply frequency-selective refocusing pulses, which becomes feasible at 3T due to the increased chemical shift dispersion as compared to 1.5T. In this study, full (1)H to (31)P polarization transfer was realized using chemical shift selective refocusing pulses at 3T. T(1) and T(2) values for (1)H and (31)P spins of PE, PC, GPE, and GPC were measured in the human brain. A more than 2-fold signal-to-noise ratio (SNR) improvement was obtained compared to an optimized direct (31)P MRS method. As shifted RF pulses were used, this method can be applied on a broadband clinical MR system with a single RF system.

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.

Molecular and functional imaging of breast cancer

Despite several major advances in breast cancer diagnosis and treatment, the American Cancer Society has estimated that in the US alone 43300 women and 400 men will die from breast cancer in 2007. Breast cancer typically is a multi-focal, multi-faceted disease, with the major cause of mortality being complications due to metastasis. Whereas a decade ago genetic alterations were the primary focus in cancer research, it is now apparent that the physiological tumor microenvironment, interactions between cancer cells and stromal cells such as endothelial cells, fibroblasts and macrophages, the extracellular matrix, and a multitude of secreted factors and cytokines influence progression, aggressiveness, and response of the disease to treatment. Prevention, early diagnosis, and treatment are the three broad challenges for MR molecular and functional imaging in reducing mortality from this disease. Multi-parametric molecular and functional MRI provides unprecedented opportunities for identifying novel targets for imaging and therapy at the bench, as well as for accurate diagnosis and monitoring response to therapy at the bedside. Here we provide an overview of the current status of molecular and functional MRI of breast cancer, outlining some key developments, as well as identifying some of the important challenges facing this field in the future.

Characterization of breast cancers and therapy response by MRS and quantitative gene expression profiling in the choline pathway

Tumor choline metabolites have potential for use as diagnostic indicators of breast cancer phenotype and can be non-invasively monitored in vivo by MRS. Extract studies have determined that the principle diagnostic component of these peaks is phosphocholine (PCho), the biosynthetic precursor to the membrane phospholipid, phosphatidylcholine (PtdCho). The ability to resolve and quantify PCho in vivo would improve the accuracy of this putative diagnostic tool. In addition, determining the biochemical mechanisms underlying these metabolic perturbations will improve the understanding of breast cancer and may suggest potential molecular targets for drug development. Reported herein is the in vivo resolution and quantification of PCho and glycerophosphocholine (GPC) in breast cancer xenografts in SCID mice via image-guided 31P MRS, localized to a single voxel. Tumor metabolites are also detected using ex vivo extracts and high-resolution NMR spectroscopy and are quantified in the metastatic tumor line, MDA-mb-231. Also reported is the quantification of cytosolic and lipid metabolites in breast cells of differing cancer phenotype, and the identification of metabolites that differ among these cell lines. In cell extracts, PCho and the PtdCho breakdown products, lysophosphatidylcholine, GPC and glycerol 3-phosphate, are all raised in breast cancer lines relative to an immortalized non-malignant line. These metabolic differences are in direct agreement with differences in expression of genes encoding enzymes in the choline metabolic pathway. Results of this study are consistent with previous studies, which have concluded that increased choline uptake, increased choline kinase activity, and increased phosholipase-mediated turnover of PtdCho contribute to the observed increase in PCho in breast cancer. In addition, this study presents evidence suggesting a specific role for phospholipase A2-mediated PtdCho catabolism. Gene expression changes following taxane therapy are also reported and are consistent with previously reported changes in choline metabolites after the same therapy in the same tumor model.

Aberrant regulation of choline metabolism by mitochondrial electron transport system inhibition in neuroblastoma cells

Anomalous choline metabolic patterns have been consistently observed in vivo using Magnetic Resonance Spectroscopy (MRS) analysis of patients with neurodegenerative diseases and tissues from cancer patient. It remains unclear; however, what signaling events may have triggered these choline metabolic aberrancies. This study investigates how changes in choline and phospholipid metabolism are regulated by distinct changes in the mitochondrial electron transport system (ETS). We used specific inhibitors to down regulate the function of individual protein complexes in the ETS of SH-SY5Y neuroblastoma cells. Interestingly, we found that dramatic elevation in the levels of phosphatidylcholine metabolites could be induced by the inhibition of individual ETS complexes, similar to in vivo observations. Such interferences produced divergent metabolic patterns, which were distinguishable via principal component analysis of the cellular metabolomes. Functional impairments in ETS components have been reported in several central nervous system (CNS) diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD); however, it remains largely unknown how the suppression of individual ETS complex function could lead to specific dysfunction in different cell types, resulting in distinct disease phenotypes. Our results suggest that the inhibition of each of the five ETS complexes might differentially regulate phospholipase activities within choline metabolic pathways in neuronal cells, which could contribute to the overall understanding of mitochondrial diseases.

Quantification of choline- and ethanolamine-containing metabolites in human prostate tissues using 1H HR-MAS total correlation spectroscopy

A fast and quantitative 2D high-resolution magic angle spinning (HR-MAS) total correlation spectroscopy (TOCSY) experiment was developed to resolve and quantify the choline- and ethanolamine-containing metabolites in human prostate tissues in approximately 1 hr prior to pathologic analysis. At a 40-ms mixing time, magnetization transfer efficiency constants were empirically determined in solution and used to calculate metabolite concentrations in tissue. Phosphocholine (PC) was observed in 11/15 (73%) cancer tissues but only 6/32 (19%) benign tissues. PC was significantly higher (0.39 +/- 0.40 mmol/kg vs. 0.02 +/- 0.07 mmol/kg, z = 3.5), while ethanolamine (Eth) was significantly lower in cancer versus benign prostate tissues (1.0 +/- 0.8 mmol/kg vs. 2.3 +/- 1.9 mmol/kg, z = 3.3). Glycerophosphocholine (GPC) (0.57 +/- 0.87 mmol/kg vs. 0.29 +/- 0.26 mmol/kg, z = 1.2), phosphoethanolamine (PE) (4.4 +/- 2.2 mmol/kg vs. 3.4 +/- 2.6 mmol/kg, z = 1.4), and glycerophosphoethanolamine (GPE) (0.54 +/- 0.82 mmol/kg vs. 0.15 +/- 0.15 mmol/kg, z = 1.8) were higher in cancer versus benign prostate tissues. The ratios of PC/GPC (3.5 +/- 4.5 vs. 0.32 +/- 1.4, z = 2.6), PC/PE (0.08 +/- 0.08 vs. 0.01 +/- 0.03, z = 3.5), PE/Eth (16 +/- 22 vs. 2.2 +/- 2.0, z = 2.4), and GPE/Eth (0.41 +/- 0.51 vs. 0.06 +/- 0.06, z = 2.6) were also significantly higher in cancer versus benign tissues. All samples were pathologically interpretable following HR-MAS analysis; however, degradation experiments showed that PC, GPC, PE, and GPE decreased 7.7 +/- 2.2%, while Cho+mI and Eth increased 18% in 1 hr at 1 degrees C and a 2250 Hz spin rate.

Positron Emission Tomography (PET) radiotracers in oncology--utility of 18F-Fluoro-deoxy-glucose (FDG)-PET in the management of patients with non-small-cell lung cancer (NSCLC)

PET (Positron Emission Tomography) is a nuclear medicine imaging method, frequently used in oncology during the last years. It is a non-invasive technique that provides quantitative in vivo assessment of physiological and biological phenomena. PET has found its application in common practice for the management of various cancers.Lung cancer is the most common cause of death for cancer in western countries.This review focuses on radiotracers used for PET scan with particular attention to Non Small Cell Lung Cancer diagnosis, staging, response to treatment and follow-up.

Comparison of T(1) and T(2) metabolite relaxation times in glioma and normal brain at 3T

PURPOSE

To measure T(1) and T(2) relaxation times of metabolites in glioma patients at 3T and to investigate how these values influence the observed metabolite levels.

MATERIALS AND METHODS

A total of 23 patients with gliomas and 10 volunteers were studied with single-voxel two-dimensional (2D) J-resolved point-resolved spectral selection (PRESS) using a 3T MR scanner. Voxels were chosen in normal appearing white matter (WM) and in regions of tumor. The T(1) and T(2) of choline containing compounds (Cho), creatine (Cr), and N-acetyl aspartate (NAA) were estimated.

RESULTS

Metabolite T(1) relaxation values in gliomas were not significantly different from values in normal WM. The T(2) of Cho and Cr were statistically significantly longer for grade 4 gliomas than for normal WM but the T(2) of NAA was similar. These differences were large enough to impact the corrections of metabolite levels for relaxation times with tumor grade in terms of metabolite ratios (P < 0.001).

CONCLUSION

The differential increase in T(2) for Cho and Cr relative to NAA means that the ratios of Cho/NAA and Cr/NAA are higher in tumor at longer echo times (TEs) relative to values in normal appearing brain. Having this information may be useful in defining the acquisition parameters for optimizing contrast between tumor and normal tissue in MR spectroscopic imaging (MRSI) data, in which limited time is available and only one TE can be used.

An illustration of the potential for mapping MRI/MRS parameters with genetic over-expression profiles in human prostate cancer

INTRODUCTION

Magnetic resonance imaging (MRI) and MR spectroscopy can probe a variety of physiological (e.g. blood vessel permeability) and metabolic characteristics of prostate cancer. However, little is known about the changes in gene expression that underlie the spectral and imaging features observed in prostate cancer. Tumor induced changes in vascular permeability and angiogenesis are thought to contribute to patterns of dynamic contrast enhanced (DCE) MRI images of prostate cancer even though the genetic basis of tumor vasculogenesis is complex and the specific mechanisms underlying these DCEMRI features have not yet been determined.

MATERIALS AND METHODS

In order to identify the changes in gene expression that correspond to MRS and DCEMRI patterns in human prostate cancers, we have utilized tissue print micropeel techniques to generate "whole mount" molecular maps of radical prostatectomy specimens that correspond to pre-surgical MRI/MRS studies. These molecular maps include RNA expression profiles from both Affymetrix GeneChip microarrays and quantitative reverse transcriptase PCR (qrt-PCR) analysis, as well as immunohistochemical studies.

RESULTS

Using these methods on patients with prostate cancer, we found robust over-expression of choline kinase a in the majority of primary tumors. We also observed overexpression of neuropeptide Y (NPY), a newly identified angiogenic factor, in a subset of prostate cancers, visualized on DCEMRI.

CONCLUSION

These studies set the stage for establishing MRI/MRS parameters as validated biomarkers for human prostate cancer.

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.

The role of proton magnetic resonance spectroscopy in the diagnosis and categorization of cerebral abscesses

✓ Despite recent advances in neuroimaging, differentiation between cerebral abscesses and necrotic tumors with ring-type contrast enhancement can be puzzling at times. The introduction of advanced imaging techniques, such as diffusion-weighted imaging, has contributed to the identification of cerebral abscesses. However, differentiation may be impossible with imaging only. In this review the authors evaluate the role of proton magnetic resonance (MR) spectroscopy in differentiating between cerebral abscesses and necrotic tumors and address the spectral characteristics of intracranial abscesses. A large number of metabolites not detected in the normal brain spectra may be detected and give valuable information regarding the nature of the abscesses. Proton MR spectroscopy is a safe, noninvasive diagnostic modality, which could significantly increase the accuracy and specificity of conventional MR imaging in differentiating between malignant tumors and cerebral abscesses and provide valuable information regarding the cause of an abscess, as well as, its response to the chosen treatment.

Proton (1H) MR spectroscopy of the breast

Proton (hydrogen 1) [1H]) magnetic resonance (MR) spectroscopy provides biochemical information about the tissue under investigation. Its diagnostic value in cancer is typically based on the detection of elevated levels of choline compounds, choline being a marker of active tumor. The two main potential clinical applications of 1H MR spectroscopy are (a) as an adjunct to breast MR imaging to improve specificity in differentiating benign from malignant lesions, and (b) for monitoring or even predicting response to treatment in patients undergoing neoadjuvant chemotherapy. Preliminary data are promising, with study results suggesting that 1H MR spectroscopy may decrease the number of benign biopsies recommended on the basis of MR imaging findings and may help predict response as early as 24 hours after the first dose of neoadjuvant chemotherapy. Although several limitations currently exist that make the technique premature for clinical use, further evaluation with larger, preferably multicenter trials is certainly warranted.

Noninvasive magnetic resonance spectroscopic pharmacodynamic markers of a novel histone deacetylase inhibitor, LAQ824, in human colon carcinoma cells and xenografts

The aim of this work was to use phosphorus magnetic resonance spectroscopy ((31)P MRS) to investigate the pharmacodynamic effects of LAQ824, a histone deacetylase (HDAC) inhibitor. Human HT29 colon carcinoma cells were examined by (31)P MRS after treatment with LAQ824 and another HDAC inhibitor, suberoylanilide hydroxamic acid. HT29 xenografts and tumor extracts were also examined using (31)P MRS, pre- and post-LAQ824 treatment. Histone H3 acetylation was determined using Western blot analysis, and tumor microvessel density by immunohistochemical staining of CD31. Phosphocholine showed a significant increase in HT29 cells after treatment with LAQ824 and suberoylanilide hydroxamic acid. In vivo, the ratio of phosphomonoester/total phosphorus (TotP) signal was significantly increased in LAQ824-treated HT29 xenografts, and this ratio was inversely correlated with changes in tumor volume. Statistically significant decreases in intracellular pH, beta-nucleoside triphosphate (beta-NTP)/TotP, and beta-NTP/inorganic phosphate (Pi) and an increase in Pi/TotP were also seen in LAQ824-treated tumors. Tumor extracts showed many significant metabolic changes after LAQ824 treatment, in parallel with increased histone acetylation and decreased microvessel density. Treatment with LAQ824 resulted in altered phospholipid metabolism and compromised tumor bioenergetics. The phosphocholine and phosphomonoester increases may have the potential to act as pharmacodynamic markers for noninvasively monitoring tumor response after treatment with LAQ824 or other HDAC inhibitors.

Resistance to chemotherapy in cancer: a complex and integrated cellular response

Inherent and acquired resistance pathways account for the high rate of failure in cancer chemotherapy. The mechanisms or pathways mediating resistance may be classified as pharmacokinetic (i.e. alter intratumour drug exposue) or pharmacodynamic (i.e. failure to elicit cytotoxicity). More often than not, the resistant phenotype is characterised by alterations in multiple pathways. Consequently, the pathways may act synergistically or generate a broad spectrum of resistance to anticancer drugs. There has been a great deal of systematic characterisation of drug resistance in vitro. However, translating this greater understanding into clinical efficacy has rarely been achieved. This review explores the phenomenon of drug resistance in cancer and highlights the gap between in vitro and in vivo observations. This gap presents a major obstacle in overcoming drug resistance and restoring sensitivity to chemotherapy.

The value of 18F-choline PET/CT in patients with elevated PSA-level and negative prostate needle biopsy for localisation of prostate cancer

PURPOSE

Patients with persistent elevated PSA and repeated negative prostate biopsy, that means having the prostate biopsied at multiple times, were investigated with 18F-choline PET/CT to delineate prostate cancer and guide renewed prostate biopsy.

METHODS

Twenty patients with elevated PSA and negative prostate biopsies underwent 18F-choline PET/CT. We performed an early examination of the pelvic region 3-5 min after application. After 30 minutes a whole body PET/CT examination was performed. Image analysis was performed visually and by semi-quantitative analysis calculating the maximum standardised uptake value (SUVmax). 18F-choline uptake was defined as focal, multifocal or inhomogeneous. After the 18F-choline PET/CT, all patients underwent a repeated prostate biopsy, and in the cases where a focal or multifocal uptake was found, the biopsy was guided by the result of the examination.

RESULTS

Qualitative image analysis revealed focal 18F-choline uptake in 13 out of 20 patients. In five patients, prostate cancer was revealed by repeated aspiration biopsy. None of the patients with a multifocal or inhomogeneous 18F-choline uptake had a malignant neoplasm in the prostate. Semiquantitative analysis performed with SUVmax was not helpful in the discrimination of malignancy but showed high values also in benign prostate diseases, as well as in normal prostate tissue. The dual-phase protocol delivered no clear benefit in discriminating malignancy from benign alterations.

CONCLUSION

The use of 18F-choline cannot be generally recommended for localising prostate cancer; however, in highly selected patients, we found useful additional information. In 25% of patients, 18F-choline PET/CT allowed the identification of neoplastic prostatic zones.

Hypoxia regulates choline kinase expression through hypoxia-inducible factor-1 alpha signaling in a human prostate cancer model

The intensity of the total choline (tCho) signal in spectroscopic images of tumors is spatially heterogeneous. The likewise heterogeneous physiologic tumor microenvironment may contribute to this heterogeneity. We therefore investigated the relationship between hypoxia, choline metabolites, and choline kinase (Chk) in a human prostate cancer model. Human PC-3 prostate cancer cells were engineered to express enhanced green fluorescent protein (EGFP) under hypoxic conditions. These PC-3-5HRE-EGFP cells were characterized in culture and as tumors transplanted in mice using (1)H magnetic resonance spectroscopy (MRS) and MRS imaging (MRSI) combined with EGFP fluorescence microscopy and imaging. Hypoxic EGFP-fluorescing tumor regions colocalized with regions of high tCho in combined MRSI and optical imaging studies. Cellular phosphocholine (PC) and tCho concentrations as well as Chk expression levels significantly increased following exposure of PC-3 cells to hypoxia. A putative promoter region located 5' of the translation start site of the human chk-alpha gene was cloned and luciferase (Luc)-based reporter vector constructs were generated. Luc reporter assays provided evidence that some of the putative hypoxia response elements (HRE) within this putative chk-alpha promoter region functioned in vitro. Chromatin immunoprecipitation assays using an antibody against hypoxia-inducible factor (HIF)-1 alpha showed that HIF-1 can directly bind this region of the endogenous chk-alpha promoter in hypoxic PC-3-5HRE-EGFP cells. These data suggest that HIF-1 activation of HREs within the putative chk-alpha promoter region can increase Chk-alpha expression within hypoxic environments, consequently increasing cellular PC and tCho levels within these environments.

Using metabolomics to monitor anticancer drugs

The metabolome of a cancer cell is likely to show changes after responding to an anticancer drug. These changes could be used to decide whether to continue treatment or, in the context of a drug trial, to indicate whether the drug is working and perhaps its mechanism of action. (Nuclear) magnetic resonance spectroscopy (NMR/MRS) methods can offer important insights into novel anticancer agents in order to accelerate the drug development process including time-course studies on the effect of a drug on its site of action (termed pharmacodynamics), in this case the cancer. In addition, some classes of anticancer agents currently under development (e.g. antiangiogenics) are designed to be used in combination with other drugs and will not cause tumour shrinkage when used as single agents in Phase 1 clinical trials. Thus NMR/MRS may have a special role in monitoring the pharmacodynamic actions of such drugs in early-phase clinical trials. This review focuses on the use of ex vivo NMR and in vivo MRS methods for monitoring the effect of some novel anticancer drugs on the cancer metabolome. Ex vivo NMR methods are complementary to in vivo measurements, as they can provide additional information and help in the interpretation of the in vivo data.

Conventional and novel PET tracers for imaging in oncology in the era of molecular therapy

In the last ten years, the development of several novel targeted drugs and the refinement of state of the art technologies such as the genomics and proteomics and their introduction to clinical practice have revolutionized the management of patients affected by cancer. However, everyday practice points out several clinical questions: the difficulty of response assessment to new drugs especially using standard RECIST criteria that do not provide information on biological, vascular or metabolic variations; the inadequate selection of patients who are likely to benefit from a targeted therapy excluding those with breast cancer and gastrointestinal stromal tumours; the need to know the global biological background of diseases especially in metastatic setting using repeatable non-invasive procedures. Molecular imaging could provide information on in vivo distribution of biological markers in response to targeted therapy and could improve the selection of patients before therapies. The aim of this review is to analyze the current role of conventional and innovative positron emission tomography (PET) radiotracers in clinical practice and to explore the promising perspectives of molecular imaging in cancer research.

In vivo monitoring response to chemotherapy of human diffuse large B-cell lymphoma xenografts in SCID mice by 1H and 31P MRS

RATIONALE AND OBJECTIVES

A reliable noninvasive method for in vivo detection of early therapeutic response of non-Hodgkin's lymphoma (NHL) patients would be of great clinical value. This study evaluates the feasibility of (1)H and (31)P magnetic resonance spectroscopy (MRS) for in vivo detection of response to combination chemotherapy of human diffuse large B-cell lymphoma (DLCL2) xenografts in severe combined immunodeficient (SCID) mice.

MATERIALS AND METHODS

Combination chemotherapy with cyclophosphamide, hydroxy doxorubicin, Oncovin, prednisone, and bryostatin 1 (CHOPB) was administered to tumor-bearing SCID mice weekly for up to four cycles. Spectroscopic studies were performed before the initiation of treatment and after each cycle of the CHOPB. Proton MRS for detection of lactate and total choline was performed using a selective multiple-quantum-coherence-transfer (Sel-MQC) and a spin-echo-enhanced Sel-MQC (SEE-Sel-MQC) pulse sequence, respectively. Phosphorus-31 MRS using a nonlocalized, single-pulse sequence without proton decoupling was also performed on these animals.

RESULTS

Significant decreases in lactate and total choline were detected in the DLCL2 tumors after one cycle of CHOPB chemotherapy. The ratio of phosphomonoesters to beta-nucleoside triphosphate (PME/betaNTP, measured by (31)P MRS) significantly decreased in the CHOPB-treated tumors after two cycles of CHOPB. The control tumors did not exhibit any significant changes in either of these metabolites.

CONCLUSIONS

This study demonstrates that (1)H and (31)P MRS can detect in vivo therapeutic response of NHL tumors and that lactate and choline offer a number of advantages over PMEs as markers of early therapeutic response.

Metabolism of diffuse intrinsic brainstem gliomas in children

Progress in the development of effective therapies for diffuse intrinsic brainstem gliomas (DIBSGs) is compromised by the unavailability of tissue samples and the lack of noninvasive markers that can characterize disease status. The purpose of this study was to compare the metabolic profile of DIBSGs with that of astrocytomas elsewhere in the CNS and to determine whether the measurement of metabolic features can improve the assessment of disease status. Forty in vivo MR spectroscopy (MRS) studies of 16 patients with DIBSG at baseline and after radiation therapy were retrospectively reviewed. Control data for baseline studies of DIBSGs were obtained from 14 untreated regular and anaplastic astrocytomas. All spectra were acquired with single-voxel, short echo-time (35 ms), point-resolved spectroscopy. Absolute metabolite concentrations (mmol/kg) and lipid intensities (arbitrary units) were determined. At baseline, creatine and total choline (tCho) were significantly lower in DIBSGs than in astrocytomas elsewhere in the CNS (4.3 +/- 1.1 vs. 7.5 +/- 1.9 mmol/kg, p < 0.001; 1.9 +/- 0.7 vs. 4.2 +/- 2.6, p < 0.001). Serial MRS in individual subjects revealed increasing levels of tCho (p < 0.05) and lipids (p < 0.05) and reduced ratios of N-acetylaspartate, creatine, and myoinositol relative to tCho (all p < 0.01). Metabolic progression defined by increased tCho concentration in serial MRS preceded clinical deterioration by 2.4 +/- 2.7 months (p < 0.04). Low tCho of DIBSG at baseline is consistent with low proliferative tumors. Subsequent metabolic changes that have been associated with malignant degeneration preceded clinical deterioration. MRS provides early surrogate markers for disease progression.

Response of choline metabolites to docetaxel therapy is quantified in vivo by localized (31)P MRS of human breast cancer xenografts and in vitro by high-resolution (31)P NMR spectroscopy of cell extracts

Choline-containing compounds (CCCs) are elevated in breast cancer, and detected in vivo by the (1)H MRS total choline (tCho) resonance (3.25 ppm) and the (31)P MRS phosphomonoester (PME) resonance (3.8 ppm). Both the tCho and PME resonances decrease early after initiation of successful therapy. The single major component of these composite resonances, phosphocholine (PCho), also responds to therapy by decreasing. The ability to resolve and quantify PCho in vivo would thus increase the sensitivity of this biomarker for early detection of therapeutic response. Herein, the in vivo resolution and quantification of PCho is reported in human mouse xenograft tumors of the human breast cancer cell lines MCF-7 and MDA-mb-231. Significant decreases in tumor PCho are observed within 2 to 4 d posttreatment with the antimicrotubule drug, docetaxel. To determine whether these decreases are a general tumor response or an intracellular metabolic response, high-resolution NMR spectroscopy was performed on extracts of cells treated with docetaxel. Significant decreases in intracellular PCho and increases in glycerophosphocholine (GPC) were observed. These decreases are coincident with other tumor and cellular responses such as tumor growth delay (TGD), cell-cycle arrest, and modes of cell death such as mitotic catastrophe, necrosis, and apoptosis, with mitotic catastrophe predominating.

Enhancing Nonmass Lesions in the Breast: Evaluation with Proton (H) MR Spectroscopy

PURPOSE

To prospectively evaluate the sensitivity and specificity of proton (hydrogen 1 [1H]) magnetic resonance (MR) spectroscopy for diagnosing malignant enhancing nonmass lesions identified at breast MR imaging, with histologic examination as the reference standard.

MATERIALS AND METHODS

In this HIPAA-compliant, institutional review board-approved study, in which all participants gave written informed consent, proton (1H) MR spectroscopy of the breast was performed in suspicious or biopsy-proved malignant lesions that were 1 cm or larger at MR imaging. Single-voxel proton (1H) MR spectroscopic data were collected. MR spectroscopic findings were defined as positive if the signal-to-noise ratio of the choline resonance peak was 2 or greater and as negative in all other cases. MR spectroscopic results were then compared with histologic findings, and statistical analysis was performed.

RESULTS

In 32 women (median age, 48.5 years [range, 20-63 years]) with enhancing nonmass lesions, the median lesion size at MR imaging was 2.8 cm (range, 1.2-9.0 cm). At histologic analysis, 12 (37%) of 32 lesions were malignant and 20 (63%) were benign. Positive choline findings were present in 15 of 32 lesions, including all 12 (100%) cancers and three (15%) of 20 benign lesions, giving proton (1H) MR spectroscopy a sensitivity of 100% (95% confidence interval [CI]: 74%, 100%) and a specificity of 85% (95% CI: 62%, 97%) for detection of enhancing nonmass lesions. For 25 lesions with unknown histologic features, proton (1H) MR spectroscopy would have significantly (P<.01) increased the positive predictive value of biopsy from 20% to 63%. If biopsy had been performed for only those lesions with positive choline findings at proton (1H) MR spectroscopy, biopsy might have been avoided for 17 (68%) of 25 lesions, and no cancers would have been missed.

CONCLUSION

Proton (1H) MR spectroscopy had 100% sensitivity and 85% specificity for the detection of malignancy in enhancing nonmass lesions.

Metabolic and molecular imaging in neuro-oncology

Techniques for human brain imaging have undergone rapid developments in recent years. Technological progress has enabled the assessment of many physiological parameters in vivo that are highly relevant for tumour grading, tissue characterisation, definition of the extent and infiltration of tumours, and planning and monitoring of therapy. In this review, we provide a brief overview of advanced MRI and molecular-tracer techniques that have many potential clinical uses. A broad range of techniques, including dynamic MRI, PET, and single photon emission computed tomography, provide measurements of various features of tumour blood flow and microvasculature. Using PET to measure glucose consumption enables visualisation of tumour metabolism, and magnetic resonance spectroscopy techniques provide complementary information on energy metabolism. Changes in protein and DNA synthesis can be assessed through uptake of labelled amino acids and nucleosides. Advanced imaging techniques can be used to assess tumour malignancy, extent, and infiltration, and might provide diagnostic clues to distinguish between lesion types and between recurrent tumour and necrosis. Stereotactic biopsies should be taken from the most malignant part of tumours, which can be identified by changes in microvascular structure and metabolic activity. Functional and metabolic imaging can improve the planning and monitoring of radiation and chemotherapy and contribute to the development of new therapies.

Metabolic findings on 3T 1H-MR spectroscopy in peritumoral brain edema

BACKGROUND AND PURPOSE

Little is known about the metabolic properties of brain edema associated with tumors. This work was conducted on the basis of the assumption that, in the presence of intra-axial and extra-axial brain tumors, the white matter involved by the edema is a site of metabolic change that involves the structure of the myelin sheath.

MATERIALS AND METHODS

Thirteen patients comprised our cohort affected by intra-axial and extra-axial cerebral tumors with a peritumoral T2-weighted MR signal hyperintensity as a result of edema, where MR spectroscopy showed no increase in choline-containing compounds. Measurements on proton MR spectroscopy (1H-MR spectroscopy) were performed with a 3T whole-body scanner with use of a point-resolved spectroscopy sequence for localization (TR, 2000 ms; TE, 35 ms), and the metabolites were quantified with the SAGE method. Peak intensities of the main metabolites were expressed as ratios of one another and were compared with values obtained in the white matter of the left frontal region in a control group of 16 healthy volunteers.

RESULTS

Choline-to-creatine (Cho/Cr) and myo-inositol-to-creatine (mIns/Cr) signal intensity ratios were normal in all patients. N-acetylaspartate-to-creatine (NAA/Cr) and N-acetylaspartate-to-choline (NAA/Cho) ratios decreased in 4 patients. Glutamate plus glutamine-to-creatine (Glx/Cr) was increased in 10 patients. A resonance peak at 3.44 ppm, strongly suggesting the presence of glucose, was detected in all but 1 patient. Lactate was detected in 12 patients and lipids in 5. Moreover, the resonances that pertained to the aliphatic amino acids valine, leucine, and isoleucine were present in 12 patients.

CONCLUSIONS

Our findings on MR spectroscopy confirmed the hypothesis that in the edema surrounding brain tumors, an energy-linked metabolic alteration was associated with injury to the myelin sheath.

Preliminary assessment of benign maxillofacial and neck lesions with in vivo single-voxel 1H magnetic resonance spectroscopy

OBJECTIVE

The purpose of this study was to assess the potential roles of in vivo single-voxel hydrogen 1 (1H) magnetic resonance (MR) spectroscopy in differentiation of benign maxillofacial and neck lesions.

STUDY DESIGN

Fifty-five benign maxillofacial and neck lesions were selected for this study. Both localization techniques for single-voxel 1H MR spectroscopy, long TE (144 ms) point-resolved spectroscopy (PRESS), and short TE (30 ms) stimulated echo acquisition mode (STEAM) were utilized. Choline (Cho) signals were regarded as the criterion to evaluate the differences among the benign lesions.

RESULTS

Choline signals were detected in 25 of 55 (45.5%) lesions with PRESS versus 12 of 55 (21.8%) lesions with STEAM (P = .015). On the PRESS, 8 out of 11 (72.7%) neurogenic tumors, 5 of 7 (71.5%) Warthin tumors, and 4 of 5 (80%) sarcoidosis and sinus histiocytosis were detected with Cho signals, whereas 16 of 19 (84.2%) fluid-filled lesions (hemangiomas, lymphangiomas, and cysts) had no Cho signals. Statistically, a significant difference of Cho signals remained between the fluid-filled lesions and the solid lesions (P = .003).

CONCLUSIONS

In vivo 1H MR spectroscopy might provide information in differentiating fluid-filled lesions from solid lesions in the maxillofacial and neck regions. Most neurogenic tumors, Warthin tumors, sarcoidosis, and sinus histiocytosis were detected with Cho signals.

Tumor acidity, chemoresistance and proton pump inhibitors

Tumor microenvironment may play a key role in tumor malignancy. It is hypothesized that hypoxia and acidity may contribute to the progression from benign to malignant growth. In particular, the unfavorable environment may induce the selection of tumor cells able to survive in acidic and hypoxic conditions. In fact, the common components of the cancer phenotype result from active selection, and characteristics of tumor microenvironment may create the best condition for this selection. Acidity, in particular, has been shown to have a role in resistance to chemotherapy, proliferation and metastatic behavior. In fact, a mechanism of resistance to cytotoxic drugs may be the alteration of the tumor microenvironment through changes of the pH gradient between the extracellular environment and cell cytoplasm. The extracellular pH of solid tumors is significantly more acidic than that of normal tissues, thus impairing the uptake of weakly basic chemotherapeutic drugs and reducing their effect on tumors. An important determinant of tumor acidity is the anaerobic metabolism that allows selection of cells able to survive in an hypoxic-anoxic environment with the generation of lactate. However, this is not the major mechanism responsible for the development of an acidic environment within solid tumors. It appears clear that a complex framework of protein-protein, protein-lipid and lipid-lipid interactions underlay the pH homeostasis in mammalian cells. Malignant tumor cells seem to hijack some of these mechanism to protect themselves from the acidic environment and to maintain acidity in an environment unsuitable for normal or more differentiated cells. Recent data suggest that vacuolar-type (V-type) H(+)-ATPases, that pump protons across the plasma membrane, may have a key role in the acidification of the tumor microenvironment. Some human tumor cells are characterized by an increased V-type H(+)-ATPase expression and activity, and pretreatment with proton pump inhibitors -- a class of H(+)-ATPase inhibitors -- sensitized tumor cell lines to the effect of a variety of anticancer drugs. Proton pump inhibitor pretreatment has been associated with inhibition of V-type H(+)-ATPase activity and increase in both extracellular pH and pH of lysosomal organelles. In vivo experiments in human/mouse xenografts have shown that oral pretreatment with proton pump inhibitors is able to sensitize human solid tumors to anticancer drugs. These data suggest that tumor alkalinization may represent a key target of future antitumor strategies.

Recent advances in magnetic resonance neurospectroscopy

Over the past two decades, proton magnetic resonance spectroscopy (proton MRS) of the brain has made the transition from research tool to a clinically useful modality. In this review, we first describe the localization methods currently used in MRS studies of the brain and discuss the technical and practical factors that determine the applicability of the methods to particular clinical studies. We also describe each of the resonances detected by localized solvent-suppressed proton MRS of the brain and discuss the metabolic and biochemical information that can be derived from an analysis of their concentrations. We discuss spectral quantitation and summarize the reproducibility of both single-voxel and multivoxel methods at 1.5 and 3-4 T. We have selected three clinical neurologic applications in which there has been a consensus as to the diagnostic value of MRS and summarize the information relevant to clinical applications. Finally, we speculate about some of the potential technical developments, either in progress or in the future, that may lead to improvements in the performance of proton MRS.

Magnetic resonance imaging and spectroscopy of transgenic models of cancer

The complexity of cancer, where a single genetic alteration can have multiple functional effects, makes it a fascinating but humbling disease to study, and the necessity of investigating it in its entirety is more imperative than ever before. Advances in transgene technology have made it possible to create cancer cells, or mice with specific genetic alterations, and the application of an array of both functional and molecular non-invasive MR methods to these transgenic cancer cells and mice to characterize their phenotypic traits is revolutionizing our understanding of cancer. With the establishment of multi-modality molecular imaging centers within barrier or pathogen-free facilities, multi-parametric and multi-modality imaging of transgenic mouse models of human cancer are becoming increasingly prevalent. In this review, we outline some of the methods currently available for generating transgenic mice and cancer cell lines. We also present examples of the application of MR methods to transgenic models that are providing novel insights into the molecular and functional characteristics of cancer and are leading to an era of "non-invasive phenotyping" of the effects of specific molecular alterations in cancer.

Diagnostic impact of proton MR-spectroscopy versus image-guided stereotactic biopsy

BACKGROUND

The aim of this study was to compare the diagnostic accuracy of (1)H MR-spectroscopy versus image-guided stereotactic biopsy.

METHOD

A cohort of 83 consecutive patients with a broad spectrum of brain lesions were examined. Prior to stereotactic biopsy, the patients were subjected to (1)H MR-spectroscopy examination. Diagnostic accuracy of (1)H MR-spectroscopy and image guided stereotactic biopsy was determined for the largest diagnostic subgroups. Each diagnostic procedure was tested for concordance in every subgroup.

FINDINGS

The subgroups of patients comprised: low grade glioma, high grade glioma (grades III and IV), lymphoma and metastasis. For the sensitivity of (1)H MR-spectroscopy ranged from 87.7 in high grade glioma to 92.3% in metastasis and for specificity from 93.3% for high grade glioma to 100% in low grade glioma. The highest positive predictive value of 100% was reached in the subgroup of low grade glioma. The highest negative predictive value was reached in lymphoma and metastasis, 100%. The kappa values were highly significant for all comparisons (p<0.001). The co-efficient ranged from 0.68 to 0.84. It was lowest in assessing high grade glioma and highest in lymphoma.

CONCLUSION

Compared with each other (1)H MR-spectroscopy and image-guided stereotactic biopsy showed a moderate to good, statistically highly significant concordance. In patients in whom operation is at an increased risk e.g., due to severe medical illness, (1)H MR-spectroscopy as a noninvasive procedure may be sufficient to assess the diagnosis.

Choline metabolism in cancer: implications for diagnosis and therapy

Magnetic resonance studies from the last 10 years have conclusively demonstrated that choline metabolism is altered in a wide variety of cancers. In cancer, the choline metabolite profile is characterized by an elevation of phosphocholine and total choline-containing compounds. This elevation is increasingly being used as an endogenous biomarker of cancer. Importantly, the enzymes and pathways resulting in these distinct alterations in phosphocholine and total choline may provide novel molecular targets for specific, targeted anticancer therapies. In this article, we have summarized some of the magnetic resonance spectroscopy and positron emission tomography techniques that are currently available, or will be in the near future, for choline metabolism-based diagnosis, staging and therapy assessment in cancer patients. This review also outlines currently known molecular alterations that cause the aberrant choline metabolite profile in cancers and concludes with a summary of recent research findings that may, in the future, lead to novel anticancer therapies targeting choline metabolism.

Imaging breast cancer

Imaging has a significant role in diagnosing, treating, and monitoring breast cancer. Advances in this field are having a great impact in the clinical management of this disease. Breast cancer has now become an "outpatient cancer". This article describes the role and advances of imaging in breast cancer.

Phosphocholine as a biomarker of breast cancer: Molecular and biochemical studies

The discovery of metabolic and molecular markers that help improving the detection and diagnosis of breast cancer is an important goal to be achieved. A high composite-choline signal in magnetic resonance spectra of breast lesions has been demonstrated to improve the accuracy of breast cancer diagnosis. In the present study we revealed the principal molecular and biochemical steps associated with the induction of choline metabolism and phosphocholine accumulation in human breast cancer cell-lines in comparison with normal human mammary epithelial cells. We found upregulation of the expression levels of specific choline transporters: organic cation transporter-2 and choline high affinity transporter-1, as well as of the enzyme choline kinase alpha in the cancerous cells in comparison with that in the normal mammary epithelial cells. The expression levels of choline transporter like-1, organic cation transporter-1 and choline kinase beta were similar in normal and cancerous cells. We further showed that choline transport rates and choline kinase activity indeed increased by several fold in the cancer cells leading to the elevation of phosphocholine. The results strongly suggest that phosphocholine can serve as a biomarker of breast cancer reflecting upregulation of specific choline transporters and choline kinase genes.

Anandamide protects from low serum-induced apoptosis via its degradation to ethanolamine

Anandamide (AEA) is a lipid molecule belonging to the family of endocannabinoids. Various studies report neuroprotective activity of AEA against toxic insults, such as ischemic conditions and excitotoxicity, whereas some show that AEA has pro-apoptotic effects. Here we have shown that AEA confers a protective activity in N18TG2 murine neuroblastoma cells subjected to low serum-induced apoptosis. We have demonstrated that the protection from apoptosis by AEA is not mediated via the CB1 receptor, the CB2 receptor, or the vanilloid receptor 1. Interestingly, breakdown of AEA by fatty acid amide hydrolase is required for the protective effect of AEA. Furthermore, the ethanolamine (EA) generated in this reaction is the metabolite responsible for the protective response. The elevation in the levels of reactive oxygen species during low serum-induced apoptosis is not affected by AEA or EA. On the other hand, AEA and EA reduce caspase 3/7 activity, and AEA attenuates the cleavage of PARP-1. Taken together, our results demonstrate a role for AEA and EA in the protection against low serum-induced apoptosis.

Choline phospholipid metabolism in cancer: consequences for molecular pharmaceutical interventions

Over the past decade, our program has focused on understanding the role of the physiological environment, tumor vasculature, and metabolism in several of the aggressive phenotypic traits of cancer, such as invasion and metastasis. These studies have been performed primarily with magnetic resonance (MR) imaging (MRI) and spectroscopy (MRS) on human breast and prostate cancer models. During the course of these studies, we observed specific changes in choline phospholipid metabolism associated with a more aggressive phenotype. Molecular or pharmacologic interventions that reduced this aggressiveness were also consistent with a reversal of these alterations. In this contextual review, we have outlined the insight we have gained from these studies and have discussed some of the enzymes and pathways that may present novel targets for pharmaceutical interventions in cancer.

Metabolic imaging by hyperpolarized 13C magnetic resonance imaging for in vivo tumor diagnosis

The "Warburg effect," an elevation in aerobic glycolysis, may be a fundamental property of cancer cells. For cancer diagnosis and treatment, it would be valuable if elevated glycolytic metabolism could be quantified in an image in animals and humans. The pyruvate molecule is at the metabolic crossroad for energy delivery inside the cell, and with a noninvasive measurement of the relative transformation of pyruvate into lactate and alanine within a biologically relevant time frame (seconds), it may be possible to quantify the glycolytic status of the cells. We have examined the metabolism after i.v. injection of hyperpolarized (13)C-pyruvate in rats with implanted P22 tumors. The strongly enhanced nuclear magnetic resonance signal generated by the hyperpolarization techniques allows mapping of pyruvate, lactate, and alanine in a 5 x 5 x 10 mm(3) imaging voxel using a 1.5 T magnetic resonance scanner. The magnetic resonance scanning (chemical shift imaging) was initiated 24 seconds after the pyruvate injection and had a duration of 14 seconds. All implanted tumors showed significantly higher lactate content than the normal tissue. The results indicate that noninvasive quantification of localized Warburg effect may be possible.

Therapeutic targets and biomarkers identified in cancer choline phospholipid metabolism

Choline phospholipid metabolism is altered in a wide variety of cancers. The choline metabolite profile of tumors and cancer cells is characterized by an elevation of phosphocholine and total choline-containing compounds. Noninvasive magnetic resonance spectroscopy can be used to detect this elevation as an endogenous biomarker of cancer, or as a predictive biomarker for monitoring tumor response to novel targeted therapies. The enzymes directly causing this elevation, such as choline kinase, phospholipase C and phospholipase D may provide molecular targets for anticancer therapies. Signal transduction pathways that are activated in cancers, such as those mediated by the receptor tyrosine kinases breakpoint cluster region-abelson (Bcr-Abl), c-KIT or epidermal growth factor receptor (EGFR), correlate with the alterations in choline phospholipid metabolism of cancers, and also offer molecular targets for specific anticancer therapies. This review summarizes recently discovered molecular targets in choline phospholipid metabolism and signal transduction pathways, which may lead to novel anticancer therapies potentially being monitored by magnetic resonance spectroscopy techniques.

MR-determined metabolic phenotype of breast cancer in prediction of lymphatic spread, grade, and hormone status

The purpose of the study was to evaluate the use of metabolic phenotype, described by high-resolution magic angle spinning magnetic resonance spectroscopy (HR MAS MRS), as a tool for prediction of histological grade, hormone status, and axillary lymphatic spread in breast cancer patients. Biopsies from breast cancer (n = 91) and adjacent non-involved tissue (n = 48) were excised from patients (n = 77) during surgery. HR MAS MR spectra of intact samples were acquired. Multivariate models relating spectral data to histological grade, lymphatic spread, and hormone status were designed. The multivariate methods applied were variable reduction by principal component analysis (PCA) or partial least-squares regression-uninformative variable elimination (PLS-UVE), and modelling by PLS, probabilistic neural network (PNN), or cascade correlation neural network. In the end, model verification by prediction of blind samples (n = 12) was performed. Validation of PNN training resulted in sensitivity and specificity ranging from 83 to 100% for all predictions. Verification of models by blind sample testing showed that hormone status was well predicted by both PNN and PLS (11 of 12 correct), lymphatic spread was best predicted by PLS (8 of 12), whereas PLS-UVE PNN was the best approach for predicting grade (9 of 12 correct). MR-determined metabolic phenotype may have a future role as a supplement for clinical decision-making-concerning adjuvant treatment and the adaptation to more individualised treatment protocols.