Proton HR-MAS spectroscopy and quantitative pathologic analysis of MRI/3D-MRSI-targeted postsurgical prostate tissues

Metabolic, pathologic, and genetic analysis of prostate tissues: quantitative evaluation of histopathologic and mRNA integrity after HR-MAS spectroscopy

The impact of high-resolution magic angle spinning (HR-MAS) spectroscopy on the histopathologic and mRNA integrity of human prostate tissues was evaluated. Forty prostate tissues were harvested at transrectal ultrasound (TRUS) guided biopsy (n = 20) or radical prostatectomy surgery (n = 20), snap-frozen on dry ice, and stored at -80°C until use. Twenty-one samples (n = 11 biopsy, n = 10 surgical) underwent HR-MAS spectroscopy prior to histopathologic and cDNA microarray analysis, while 19 control samples (n = 9 biopsy, n = 10 surgical) underwent only histopathologic and microarray analysis. Frozen tissues were sectioned at 14-µm intervals and placed on individual histopathology slides. Every 8th slide was stained with hematoxylin and eosin (H&E) and used to target areas of predominantly epithelial tissue on the remaining slides for mRNA integrity and cDNA microarray analysis. Histopathologic integrity was graded from 1 (best) to 5 (worst) by two 'blinded' pathologists. Histopathologic integrity scores were not significantly different for post-surgical tissues (HR-MAS vs controls); however, one pathologist's scores were significantly lower for biopsy tissues following HR-MAS while the other pathologist's scores were not. mRNA integrity assays were performed using an Agilent 2100 Bioanalyzer and the electrophoretic traces were scored with an RNA integrity number (RIN) from 1 (degraded) to 10 (intact). RIN scores were not significantly different for surgical tissues, but were significantly lower for biopsy tissues following HR-MAS spectroscopy. The isolated mRNA then underwent two rounds of amplification, conversion to cDNA, coupling to Cy3 and Cy5 dyes, microarray hybridization, imaging, and analysis. Significance analysis of microarrays (SAM) identified no significantly over- or under-expressed genes, including 14 housekeeping genes, between HR-MAS and control samples of surgical and biopsy tissues (5% false discovery rate). This study demonstrates that histopathologic and genetic microarray analysis can be successfully performed on prostate surgical and biopsy tissues following HR-MAS analysis; however, biopsy tissues are more fragile than surgical tissues.

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

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

Methods for metabolic evaluation of prostate cancer cells using proton and (13)C HR-MAS spectroscopy and [3-(13)C] pyruvate as a metabolic substrate

Prostate cancer has been shown to undergo unique metabolic changes associated with neoplastic transformation, with associated changes in citrate, alanine, and lactate concentrations. (13)C high resolution-magic angle spinning (HR-MAS) spectroscopy provides an opportunity to simultaneously investigate the metabolic pathways implicated in these changes by using (13)C-labeled substrates as metabolic probes. In this work, a method to reproducibly interrogate metabolism in prostate cancer cells in primary culture was developed using HR-MAS spectroscopy. Optimization of cell culture protocols, labeling parameters, harvesting, storage, and transfer was performed. Using [3-(13)C] pyruvate as a metabolic probe, (1)H and (13)C HR-MAS spectroscopy was used to quantify the net amount and fractional enrichment of several labeled metabolites that evolved in multiple cell samples from each of five different prostate cancers. Average enrichment across all cancers was 32.4 +/- 5.4% for [3-(13)C] alanine, 24.5 +/- 5.4% for [4-(13)C] glutamate, 9.1 +/- 2.5% for [3-(13)C] glutamate, 25.2 +/- 5.7% for [3-(13)C] aspartate, and 4.2 +/- 1.0% for [3-(13)C] lactate. Cell samples from the same parent population demonstrated reproducible fractional enrichments of alanine, glutamate, and aspartate to within 12%, 10%, and 10%, respectively. Furthermore, the cells produced a significant amount of [4-(13)C] glutamate, which supports the bioenergetic theory for prostate cancer. These methods will allow further characterization of metabolic properties of prostate cancer cells in the future. Magn Reson Med, 2009. (c) 2009 Wiley-Liss, Inc.

Detection of polyunsaturated omega-6 fatty acid in human malignant prostate tissue by 1D and 2D high-resolution magic angle spinning NMR spectroscopy

OBJECT

Polyunsaturated omega-6 fatty acids (PUFAs) have been shown to promote prostate cancer. Here, we describe the use of HRMAS NMR spectroscopy to detect omega-6 PUFA species in prostate tissues.

MATERIALS AND METHODS

Samples originating from non-malignant (n = 54) and malignant (n = 27) prostate tissues (from 27 prostatectomized men) were studied by 1D (1)H, 2D (1)H-(1)H and (1)H-(13)C HRMAS NMR spectroscopy followed by histopathological characterization.

RESULTS

HRMAS NMR proved to be a powerful, non-destructive method to identify and characterize PUFAs. The omega-6 PUFA was found in 15% of examined human prostate tumors.

CONCLUSION

It is possible to detect PUFAs in prostate tissues using our NMR-based spectroscopic approach.

Elliptical magnetic resonance spectroscopic imaging with GRAPPA for imaging brain tumors at 3 T

Magnetic Resonance Spectroscopic Imaging (MRSI) is a technique for imaging spatial variation of metabolites and has been very useful in characterizing biochemical changes associated with disease as well as response to therapy in malignant pathologies. This work presents a self-calibrated undersampling to accelerate 3D elliptical MRSI and an extrapolation-reconstruction algorithm based on the GRAPPA method. The accelerated MRSI technique was tested in three volunteers and five brain tumor patients. Acceleration allowed larger spatial coverage and consequently, less lipid contamination in spectra, compared to fully sampled acquisition within the same scantime. Metabolite concentrations measured from the accelerated acquisitions were in good agreement with measurements obtained from fully sampled MRSI scans.

Evaluation of the ERETIC method as an improved quantitative reference for 1H HR-MAS spectroscopy of prostate tissue

The Electronic REference To access In vivo Concentrations (ERETIC) method was applied to (1)H HR-MAS spectroscopy. The accuracy, precision, and stability of ERETIC as a quantitative reference were evaluated in solution and human prostate tissue samples. For comparison, the reliability of 3-(trimethylsilyl)propionic-2,2,3,3-d(4) acid (TSP) as a quantitation reference was also evaluated. The ERETIC and TSP peak areas were found to be stable in solution over the short-term and long-term, with long-term relative standard deviations (RSDs) of 4.10% and 2.60%, respectively. Quantification of TSP in solution using the ERETIC peak as a reference and a calibrated, rotor-dependent conversion factor yielded results with a precision < or =2.9% and an accuracy error < or =4.2% when compared with the expected values. The ERETIC peak area reproducibility was superior to TSP's reproducibility, corrected for mass, in both prostate surgical and biopsy samples (4.53% vs. 21.2% and 3.34% vs. 31.8%, respectively). Furthermore, the tissue TSP peaks exhibited only 27.5% of the expected area, which would cause an overestimation of metabolite concentrations if used as a reference. The improved quantification accuracy and precision provided by ERETIC may enable the detection of smaller metabolic differences that may exist between individual tissue samples and disease states.

HRMAS 1H-NMR measured changes of the metabolite profile as mesenchymal stem cells differentiate to targeted fat cells in vitro: implications for non-invasive monitoring of stem cell differentiation in vivo

Mesenchymal stem cells (MSCs) have shown a great potential for clinical applications in regenerative medicine. However, it remains challenging to follow the transplanted cell grafts in vivo. Nuclear magnetic resonance spectroscopy (NMR or MRS) is capable of determining and quantifying the cellular metabolites in tissue and organs non-invasively, therefore it is an attractive method for monitoring and evaluating the differentiation and functions of transplanted stem cells in vivo. In this study, metabolic changes of MSCs undergoing adipogenic differentiation to targeted fat cells were investigated in vitro, using solid-state high-resolution magic angle spinning (1)H nuclear magnetic resonance spectroscopy. Quantification of metabolite concentrations before and after differentiation of MSCs showed decreased levels of intracellular metabolites, including choline, creatine, glutamate and myo-inositol, and a substantially increased level of fatty acids, when mesenchymal stem cells were differentiated preferentially to fat cells. Intracellular creatine, myo-inositol and choline reduced from 10.4 +/- 0.72, 16.2 +/- 1.2 and 8.22 +/- 0.51 mM to 3.27 +/- 0.34, 6.1 +/- 0.46 and 3.11 +/- 0.32 mM, respectively, while fatty acids increased from 32.6 +/- 1.5 to 91.2 +/- 3.2 mM after undergoing 3 weeks of differentiation. The increase of the fatty acid concentration measured by NMR is confirmed by the observation of 80% fat cells in differentiated cells by cell counting assay, suggesting resonances from fatty acids may be used as metabolite markers for monitoring MSC differentiation to fat cells in vivo, using the magnetic resonance spectroscopic technique readily available on MRI scanners.

Correlation of MR imaging and MR spectroscopic imaging findings with Ki-67, phospho-Akt, and androgen receptor expression in prostate cancer

PURPOSE

To retrospectively assess whether magnetic resonance (MR) imaging and MR spectroscopic imaging and selected molecular markers correlate with each other and with clinically insignificant and significant prostate cancer (PCa), as defined at surgical pathologic analysis.

MATERIALS AND METHODS

The institutional review board approved this HIPAA-compliant study and waived informed consent. Eighty-nine men (mean age, 63 years; range, 46-79 years) with biopsy-proved PCa underwent combined endorectal MR imaging and MR spectroscopic imaging before radical prostatectomy. Suspicion of clinically insignificant PCa was retrospectively and separately recorded for MR imaging and combined MR imaging and MR spectroscopic imaging by using a scale of 0-3. Clinically insignificant PCa was pathologically defined as organ-confined cancer of 0.5 cm(3) or less without poorly differentiated elements. Prostatectomy specimens underwent immunohistochemical analysis for three molecular markers: Ki-67, phospho-Akt (pAkt), and androgen receptor (AR). To examine differences in marker levels for clinically insignificant and significant cancer, a Wilcoxon rank sum test was used. To examine correlations between marker levels and MR imaging or combined MR imaging and MR spectroscopic imaging scores, the Spearman correlation was used.

RESULTS

Twenty-one (24%) patients had clinically insignificant and 68 (76%) had clinically significant PCa at surgical pathologic review. All markers were significantly correlated with MR imaging and combined MR imaging and MR spectroscopic imaging findings (all correlation coefficients >0.5). In differentiating clinically insignificant from clinically significant PCa, areas under the receiver operating characteristic curves for Ki-67, AR, pAkt, MR imaging, and combined MR imaging and MR spectroscopic imaging were 0.75, 0.78, 0.80, 0.85, and 0.91, respectively.

CONCLUSION

The use of pretreatment MR imaging or combined MR imaging and MR spectroscopic imaging and molecular marker analyses of biopsy samples could facilitate better treatment selection.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/250/3/803/DC1.

Evaluation of lactate and alanine as metabolic biomarkers of prostate cancer using 1H HR-MAS spectroscopy of biopsy tissues

The goal of this study was to investigate the use of lactate and alanine as metabolic biomarkers of prostate cancer using (1)H high-resolution magic angle spinning (HR-MAS) spectroscopy of snap-frozen transrectal ultrasound (TRUS)-guided prostate biopsy tissues. A long-echo-time rotor-synchronized Carr-Purcell-Meiboom-Gill (CPMG) sequence including an electronic reference to access in vivo concentrations (ERETIC) standard was used to determine the concentrations of lactate and alanine in 82 benign and 16 malignant biopsies (mean 26.5% +/- 17.2% of core). Low concentrations of lactate (0.61 +/- 0.28 mmol/kg) and alanine (0.14 +/- 0.06 mmol/kg) were observed in benign prostate biopsies, and there was no significant difference between benign predominantly glandular (N = 54) and stromal (N = 28) biopsies between patients with (N = 38) and without (N = 44) a positive clinical biopsy. In biopsies containing prostate cancer there was a highly significant (P < 0.0001) increase in lactate (1.59 +/- 0.61 mmol/kg) and alanine (0.26 +/- 0.07 mmol/kg), and minimal overlap with lactate concentrations in benign biopsies. This study demonstrates for the first time very low concentrations of lactate and alanine in benign prostate biopsy tissues. The significant increase in the concentration of both lactate and alanine in biopsy tissue containing as little as 5% cancer could be exploited in hyperpolarized (13)C spectroscopic imaging (SI) studies of prostate cancer patients.

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

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

Metabolomics-based methods for early disease diagnostics

The emerging field of metabolomics, in which a large number of small-molecule metabolites from body fluids or tissues are detected quantitatively in a single step, promises immense potential for early diagnosis, therapy monitoring and for understanding the pathogenesis of many diseases. Metabolomics methods are mostly focused on the information-rich analytical techniques of NMR spectroscopy and mass spectrometry (MS). Analysis of the data from these high-resolution methods using advanced chemometric approaches provides a powerful platform for translational and clinical research and diagnostic applications. In this review, the current trends and recent advances in NMR- and MS-based metabolomics are described with a focus on the development of advanced NMR and MS methods, improved multivariate statistical data analysis and recent applications in the area of cancer, diabetes, inborn errors of metabolism and cardiovascular diseases.

Functional magnetic resonance imaging in prostate cancer

CONTEXT

Magnetic resonance imaging (MRI) combined with magnetic resonance spectroscopy imaging (MRSI), dynamic contrast-enhanced MRI, and diffusion-weighted MRI emerged as promising tests in the diagnosis of prostate cancer, and they show encouraging results.

OBJECTIVE

This review emphasizes different functional MRI techniques in the diagnosis of prostate cancer and includes information about their clinical value and usefulness.

EVIDENCE ACQUISITION

The authors searched the Medline, Embase, and Cochrane Library databases. There were no language restrictions. The last search was performed in October 2008.

EVIDENCE SYNTHESIS

The combination of conventional MRI with functional MRI techniques is more reliable for differentiating benign and malignant prostate tissues than any other diagnostic procedure. At present, no guideline is available that outlines which technique is best in a specific clinical situation. It also remains uncertain whether improved spatial resolution and signal-to-noise ratio of 3-T MRI will improve diagnostic performance.

CONCLUSIONS

A limited number of small studies suggest that functional MRI may improve the diagnosis and staging of prostate cancer. This finding needs further confirmation in larger studies, and cost-effectiveness needs to be established.

Re-Biopsies of the Prostate after Endo-Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS) in Patients with ASAP: Preliminary Results

Introduction e Objectives

There are some evidences that the combination of EndoMRI and MRS might be able to limit the number of iterative biopsies in patients with negative biopsies of the prostate and a still rising PSA. The aim of this study is to evaluate the possible role of EndoMRI/MRS in patients with ASAP.

Methods

From November 2005 to September 2008 we enrolled 28 consecutive patients diagnosed with ASAP at a TRUS-guided needle prostate biopsy. All patients underwent prostatic EndoMRI and MRS. A prostatic zone was classified as: suspicious for prostate cancer if low intensity signal was present on T2-weighted images and/or if the choline + creatine / citrate ratio was >0.86; equivocal or negative otherwise. A subsequent 12-core needle prostate biopsy was performed and supplementary biopsies were added in the suspicious zones. The results of MRI/MRS were then compared with histological findings.

Results

The combination of EndoMRI and MRS was suspicious for cancer in 70% of patients, equivocal in 23% and negative in 7%. Histological findings at re-biopsy included: prostate cancer in 35%, ASAP in 23%, BPH or prostatitis in 42%. In 78% of patients diagnosed with prostate cancer the combination MRI/MRS was suspicious and in 22% equivocal. In all patients the cancer was found in suspicious zones at MRI/MRS where targeted biopsies were performed.

Conclusions

The combination of EndoMRI and MRS proved to have a good sensitivity but a poor specificity in identifying a concurrent prostate cancer among patients with ASAP. The location of positive cores for prostate cancer was consistent with the suspicious zones at MRI/MRS.

High resolution magic angle spinning NMR spectroscopy for metabolic assessment of cancer presence and Gleason score in human prostate needle biopsies

OBJECTIVES

Histopathology of prostate needle biopsies (PNBs) is an important part in the diagnosis, prognosis and treatment evaluation of prostate cancer. The determination of metabolite levels in the same biopsies may have additional clinical value. Here, we demonstrate the use of non-destructive high resolution magic angle spinning (HRMAS) proton NMR Spectroscopy for the assessment of metabolic profiles of prostate tissue in PNBs as commonly obtained in standard clinical practice.

MATERIALS AND METHODS

PNBs that were taken routinely from 48 patients suspected of having prostate cancer were subjected to HRMAS proton NMR spectroscopy. Subsequent histopathology of the same biopsies classified the tissue either as cancer (n = 10) or benign (n = 30).

RESULTS

Some practical aspects of this assessment were evaluated, such as typical spectral contamination caused by the PNB procedure. Significant metabolic differences were found between malignant and benign tissue using a small set of ratio's involving signals of choline compounds, citrate and lactate. Moreover, significant correlations were observed between choline, total choline, and citrate over creatine signal ratios and the Gleason scores of tumor in PNBs and of tumor in the whole prostate.

CONCLUSION

This preliminary study indicates that HRMAS NMR of routinely obtained PNBs can provide detailed metabolic information of intact prostate tissue with clinical relevance.

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.

Advances in MR spectroscopy of the prostate

Commercial MR imaging/magnetic resonance spectroscopic imaging (MRSI) packages for staging prostate cancer on 1.5-T MR scanners are now available. The technology is becoming mature enough to begin assessing its clinical utility in selecting, planning, and following prostate cancer therapy. Before therapy, 1.5-T MR imaging/MRSI has the potential to improve the local evaluation of prostate cancer presence and volume and has a significant incremental benefit in the prediction of pathologic stage when added to clinical nomograms. After therapy, two metabolic biomarkers of effective and ineffective therapy have been identified and are being validated with 10-year outcomes. Accuracy can be improved by performing MR imaging/MRSI at higher magnetic field strengths, using more sensitive hyperpolarized (13)C MRSI techniques and through the addition of other functional MR techniques.

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

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

Combined magnetic resonance imaging and magnetic resonance spectroscopy imaging in the diagnosis of prostate cancer: a systematic review and meta-analysis

CONTEXT

Magnetic resonance imaging (MRI) combined with magnetic resonance spectroscopy imaging (MRSI) emerged as a promising test in the diagnosis of prostate cancer and showed encouraging results.

OBJECTIVE

The aim of this systematic review is to meta-analyse the diagnostic accuracy of combined MRI/MRSI in prostate cancer and to explore risk profiles with highest benefit.

EVIDENCE ACQUISITION

The authors searched the MEDLINE and EMBASE databases and the Cochrane Library, and the authors screened reference lists and contacted experts. There were no language restrictions. The last search was performed in August 2008.

EVIDENCE SYNTHESIS

We identified 31 test-accuracy studies (1765 patients); 16 studies (17 populations) with a total of 581 patients were suitable for meta-analysis. Nine combined MRI/MRSI studies (10 populations) examining men with pathologically confirmed prostate cancer (297 patients; 1518 specimens) had a pooled sensitivity and specificity on prostate subpart level of 68% (95% CI, 56-78%) and 85% (95% CI, 78-90%), respectively. Compared with patients at high risk for clinically relevant cancer (six studies), sensitivity was lower in low-risk patients (four studies) (58% [46-69%] vs 74% [58-85%]; p>0.05) but higher for specificity (91% [86-94%] vs 78% [70-84%]; p<0.01). Seven studies examining patients with suspected prostate cancer at combined MRI/MRSI (284 patients) had an overall pooled sensitivity and specificity on patients level of 82% (59-94%) and 88% (80-95%). In the low-risk group (five studies) these values were 75% (39-93%) and 91% (77-97%), respectively.

CONCLUSIONS

A limited number of small studies suggest that MRI combined with MRSI could be a rule-in test for low-risk patients. This finding needs further confirmation in larger studies and cost-effectiveness needs to be established.

Proton magnetic resonance spectroscopy of the central, transition and peripheral zones of the prostate: assignments and correlation with histopathology

Proton magnetic resonance spectroscopy (MRS) is used to compare the chemistry of the transition, central and peripheral zones of the prostate. The assignments are made using two-dimensional correlated spectroscopy and the results compared with histopathology. The chemistry associated with benign prostatic hyperplasia (BPH), prostate intraepithelial neoplasia (PIN) and malignant biopsy tissues are described. There are distinct MR spectral patterns for glandular and stromal BPH, PIN and adenocarcinoma. Importantly, there are also different spectral patterns from BPH in the transitional and central zones when compared to BPH in the peripheral zone. A pattern recognition method is used to analyze the MR spectra from the biopsy specimens. The resultant mathematical classifiers generated a high level of accuracy (sensitivity and specificity of 100 and 97%). It was found that for this accuracy to be achieved, the classifiers need to be developed by comparing the spectra with specialist serial sectioned histopathology. With serial sectioned pathology the pattern recognition method was capable of identifying less than 5% of adenocarcinoma in a given piece of tissue. Many of the chemicals identified in the biopsy specimens are available for inspection from the prostate, in vivo, at 3 T.

Two-dimensional MR spectroscopy of healthy and cancerous prostates in vivo

OBJECTIVES

A major goal of this article is to summarize the current status of evaluating prostate metabolites non-invasively using spatially resolved two-dimensional (2D) MR Spectroscopy (MRS).

MATERIALS AND METHODS

Due to various technical challenges, the spatially resolved versions of 2D MRS techniques are currently going through the developmental stage. During the last decade, four different versions of 2D MRS sequences have been successfully implemented on 3T and 1.5T MRI scanners manufactured by three different vendors. These sequences include half and maximum echo sampled J-resolved spectroscopy (JPRESS), S-PRESS and L-COSY, which are single volume localizing sequences, and the multi-voxel based JPRESS sequence.

RESULTS

Even though greater than 1ml voxels have been used, preliminary evaluations of 2D JPRESS, S-PRESS and L-COSY sequences have demonstrated unambiguous detection of citrate, creatine, choline, spermine and more metabolites in human prostates. ProFIT-based quantitation of JPRESS and L-COSY data clearly shows the superiority of 2D MRS over conventional one-dimensional (1D) MRS and more than six metabolites have been successfully quantified. These sequences have been evaluated in a small group of prostate pathologies and pilot investigations using these sequences show promising results in prostate pathologies.

CONCLUSION

Implementation of the state-of-the-art 2D MRS techniques and preliminary evaluation in prostate pathologies are discussed in this review. Even though these techniques are going through developmental and early testing phases, it is evident that 2D MRS can be easily added on to any clinical Magnetic Resonance Imaging (MRI) protocol to non-invasively record the biochemical contents of the prostate.

Metabolic profiling of transgenic adenocarcinoma of mouse prostate (TRAMP) tissue by 1H-NMR analysis: evidence for unusual phospholipid metabolism

BACKGROUND

The TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) mouse model has frequently been used in preclinical studies with chemotherapeutic/chemopreventive rationales. Here the hypothesis was tested using (1)H-NMR-based metabolic profiling that the TRAMP tumor metabolic phenotype resembles that reported for human prostate cancer.

METHODS

Aqueous extracts or intact tissues of normal prostate from 8- ("young") or 28-("old") week-old C57BL/6J wild-type mice or of prostate tumor from age-matched TRAMP mice were analyzed by (1)H-NMR. Results were compared with immunohistochemical findings. Expression of choline kinase was studied at the protein and mRNA levels.

RESULTS

In young TRAMP mice presenting with zonal hyperplasia, the ratio of glycerophosphocholine (GPC) to phosphocholine (PC) was 22% below that in wild-type mice (P < 0.05). In old TRAMP mice with well-defined malignancy, reduced tumor levels of citrate (49%), choline (33%), PC (57%), GPC (66%), and glycerophosphoinositol (61%) were observed relative to normal prostate (P < 0.05). Hierarchical cluster analysis of metabolite levels distinguished between normal and malignant tissue in old but not young mice. While the reduction in tissue citrate resembles human prostate cancer, low levels of choline species in TRAMP tumors suggest atypical phospholipid metabolism as compared to human prostate cancer. TRAMP tumor and normal prostate tissues did not differ in expression of choline kinase, which is overexpressed in human prostate cancer.

CONCLUSION

Although prostate cancer in TRAMP mice shares some metabolic features with that in humans, it differs with respect to choline phospholipid metabolism, which could impact upon the interpretation of results from biomarker or chemotherapy/chemoprevention studies.

Potential of magnetic resonance spectroscopic imaging in predicting absence of prostate cancer in men with serum prostate-specific antigen between 4 and 10 ng/ml: a follow-up study

OBJECTIVES

Screening for prostate cancer using serum prostate-specific antigen (PSA) determination has a positive predictive value of only 30% to 42% for a PSA level between 4 and 10 ng/mL. Magnetic resonance spectroscopic imaging (MRSI), which identifies cancer on the basis of changes in cellular metabolite levels, might be able to identify patients with noncancerous PSA elevation and help avoid unnecessary biopsies. We tested this hypothesis by evaluating the incidence of prostate cancer in men with a PSA level of 4 to 10 ng/mL and a negative MRSI study.

METHODS

A total of 155 men underwent a three-dimensional proton MRSI of the prostate before transrectal ultrasound-guided biopsy for clinical indications. MRSI was performed using an endorectal coil on a 1.5-T magnetic resonance scanner. Patients with no voxels positive for malignancy underwent standard sextant biopsy, and additional MRSI-targeted biopsies were obtained in men with suspicious or malignant voxels. Patients with a biopsy negative for cancer underwent repeat serum PSA estimation every 6 months for a minimum of 18 months.

RESULTS

Of the 155 men, 36 (mean PSA level of 6.47 ng/mL, range 4.25 to 9.9) had no malignant voxels on MRSI. None of them were positive for cancer on biopsy. Of these 36 men, 26 completed at least 18 months (mean 26.9, range 18 to 44) of follow-up. Four patients required repeat biopsies and one, with a persistently elevated PSA level was diagnosed with prostate cancer 29 months after the initial MRSI.

CONCLUSIONS

The results of our study have shown that prostate biopsy can be deferred in patients with an increased serum PSA of 4 to 10 ng/mL if their MRSI does not show any malignant voxels.

Metabolic profiling, metabolomic and metabonomic procedures for NMR spectroscopy of urine, plasma, serum and tissue extracts

Metabolic profiling, metabolomic and metabonomic studies mainly involve the multicomponent analysis of biological fluids, tissue and cell extracts using NMR spectroscopy and/or mass spectrometry (MS). We summarize the main NMR spectroscopic applications in modern metabolic research, and provide detailed protocols for biofluid (urine, serum/plasma) and tissue sample collection and preparation, including the extraction of polar and lipophilic metabolites from tissues. 1H NMR spectroscopic techniques such as standard 1D spectroscopy, relaxation-edited, diffusion-edited and 2D J-resolved pulse sequences are widely used at the analysis stage to monitor different groups of metabolites and are described here. They are often followed by more detailed statistical analysis or additional 2D NMR analysis for biomarker discovery. The standard acquisition time per sample is 4-5 min for a simple 1D spectrum, and both preparation and analysis can be automated to allow application to high-throughput screening for clinical diagnostic and toxicological studies, as well as molecular phenotyping and functional genomics.

Lactic acid and proteoglycans as metabolic markers for discogenic back pain

STUDY DESIGN

Disc tissue was removed at surgery from 9 patients with discogenic pain and 9 deformity patients with scoliosis undergoing anterior and posterior spinal fusion. These samples were then analyzed using ex vivo proton high resolution magic angle spinning (HR-MAS) NMR spectroscopy to produce metabolic profiles for comparison between the 2 patient groups.

OBJECTIVE

The goal of this study was to use quantitative ex vivo HR-MAS NMR spectroscopy to identify biochemical markers associated with discogenic back pain.

SUMMARY OF BACKGROUND DATA

Biomarkers of disc degeneration have been previously described using NMR spectroscopy, but the link between discogenic back pain and biomarkers has not been completely understood.

METHODS

HR-MAS NMR spectroscopy was performed on snap frozen samples taken from 9 patients who underwent discectomies for painful disc degeneration. The resulting proton NMR spectrums were compared with those from discs harvested from a reference population consisting of 9 scoliosis patients.

RESULTS

Spectral analyses demonstrated significantly lower proteoglycan (PG)/collagen (0.31 +/- 0.22 vs. 0.77 +/- 0.48) and PG/lactate (0.46 +/- 0.24 vs. 2.24 +/- 1.11) ratios, and a higher lactate/collagen (0.77 +/- 0.49 vs. 0.40 +/- 0.21) ratio in specimens obtained from discogenic pain patients when compared with scoliosis patients.

CONCLUSION

Our results suggest that spectroscopic markers of proteoglycan, collagen, and lactate may serve as metabolic markers of discogenic back pain. These results provide a further basis of the potential to develop in vivo MR spectroscopy for the investigation of discogenic back pain.

A hierarchical unsupervised spectral clustering scheme for detection of prostate cancer from magnetic resonance spectroscopy (MRS)

Magnetic Resonance Spectroscopy (MRS) along with MRI has emerged as a promising tool in diagnosis and potentially screening for prostate cancer. Surprisingly little work, however, has been done in the area of automated quantitative analysis of MRS data for identifying likely cancerous areas in the prostate. In this paper we present a novel approach that integrates a manifold learning scheme (spectral clustering) with an unsupervised hierarchical clustering algorithm to identify spectra corresponding to cancer on prostate MRS. Ground truth location for cancer on prostate was determined from the sextant location and maximum size of cancer available from the ACRIN database, from where a total of 14 MRS studies were obtained. The high dimensional information in the MR spectra is non linearly transformed to a low dimensional embedding space and via repeated clustering of the voxels in this space, non informative spectra are eliminated and only informative spectra retained. Our scheme successfully identified MRS cancer voxels with sensitivity of 77.8%, false positive rate of 28.92%, and false negative rate of 20.88% on a total of 14 prostate MRS studies. Qualitative results seem to suggest that our method has higher specificity compared to a popular scheme, z-score, routinely used for analysis of MRS data.

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.

Utilité clinique de la tomographie par émission de positons dans le cancer de la prostate

In prostate cancer, use of FDG, the radiopharmaceutical currently most widely used in oncology, is limited to the most aggressive cancers and, in the absence of another tracer, to attempting to localise occult recurrences detected biochemically (elevated PSA serum levels). Four other PET tracers are currently suggested in various situations of prostate cancer development: for guiding biopsies, for diagnosis and staging of the primary cancer and of local or metastatic recurrences, especially in bone, and for localizing occult biochemical recurrence. This article is illustrated by cases summarising our experience with fluoromethylcholine-(18F) and PET/CT. They cover a wide spectrum of clinical settings: localisation of intraprostatic neoplastic lesions, initial staging, monitoring treatment by ultrasound, detection of occult recurrences and characterisation of images on conventional imaging modalities, which are questionable or difficult to interpret.

Clinically significant prostate cancer local recurrence after radiation therapy occurs at the site of primary tumor: magnetic resonance imaging and step-section pathology evidence

PURPOSE

To determine whether prostate cancer local recurrence after radiation therapy (RT) occurs at the site of primary tumor by retrospectively comparing the tumor location on pre-RT and post-RT magnetic resonance imaging (MRI) and using step-section pathology after salvage radical prostatectomy (SRP) as the reference standard.

METHODS AND MATERIALS

Nine patients with localized prostate cancer were treated with intensity modulated RT (69-86.4 Gy), and had pre-RT and post-RT prostate MRI, biopsy-proven local recurrence, and SRP. The location and volume of lesions on pre-RT and post-RT MRI were correlated with step-section pathology findings. Tumor foci >0.2 cm(3) and/or resulting in extraprostatic disease on pathology were considered clinically significant.

RESULTS

All nine significant tumor foci (one in each patient; volume range, 0.22-8.63 cm(3)) were detected both on pre-RT and post-RT MRI and displayed strikingly similar appearances on pre-RT and post-RT MRI and step-section pathology. Two clinically insignificant tumor foci (</=0.06 cm(3)) were not detected on imaging. The ratios between tumor volumes on pathology and on post-RT MRI ranged from 0.52 to 2.80.

CONCLUSIONS

Our study provides a direct visual confirmation that clinically significant post-RT local recurrence occurs at the site of primary tumor. Our results are in agreement with reported clinical and pathologic results and support the current practice of boosting the radiation dose within the primary tumor using imaging guidance. They also suggest that monitoring of primary tumor with pre-RT and post-RT MRI could lead to early detection of local recurrence amenable to salvage treatment.

Detection of prostate cancer with MR spectroscopic imaging: an expanded paradigm incorporating polyamines

PURPOSE

To characterize benign and malignant prostate peripheral zone (PZ) tissue retrospectively by using a commercial magnetic resonance (MR) spectroscopic imaging package and incorporating the choline plus creatine-to-citrate ratio ([Cho + Cr]/Cit) and polyamine (PA) information into a statistically based voxel classification procedure.

MATERIALS AND METHODS

The institutional review board approved this HIPAA-compliant study and waived the requirement for informed consent. Fifty men (median age, 60 years; range, 44-69 years) with untreated biopsy-proved prostate cancer underwent combined endorectal MR imaging and MR spectroscopic imaging. Commercial software was used to acquire and process MR spectroscopic imaging data. The (Cho + Cr)/Cit and the PA level were tabulated for each voxel. The PA level was scored on a scale of 0 (PA undetectable) to 2 (PA peak as high as or higher than Cho peak). Whole-mount step-section histopathologic analysis constituted the reference standard. Classification and regression tree analysis in a training set generated a decision-making tree (rule) for classifying voxels as malignant or benign, which was validated in a test set. Receiver operating characteristic and generalized estimating equation regression analyses were used to assess accuracy and sensitivity, respectively.

RESULTS

The median (Cho + Cr)/Cit was 0.55 (mean +/- standard deviation, 0.59 +/- 0.03) in benign and 0.77 (mean, 1.08 +/- 0.20) in malignant PZ voxels (P = .027). A significantly higher percentage of benign (compared with malignant) voxels had higher PA than choline peaks (P < .001). In the 24-patient training set (584 voxels), the rule yielded 54% sensitivity and 91% specificity for cancer detection; in the 26-patient test set (667 voxels), it yielded 42% sensitivity and 85% specificity. The percentage of cancer in the voxel at histopathologic analysis correlated positively (P < .001) with the sensitivity of the classification and regression tree rule, which was 75% in voxels with more than 90% malignancy.

CONCLUSION

The statistically based classification rule developed indicated that PAs have an important role in the detection of PZ prostate cancer. With commercial software, this method can be applied in clinical settings.

Multidimensional HRMAS NMR: a platform for in vivo studies using intact bacterial cells

In vivo analysis in whole cell bacteria, especially the native tertiary structures of the bacterial cell wall, remains an unconquered frontier. The current understanding of bacterial cell wall structures has been based on destructive analysis of individual components. These in vitro results may not faithfully reflect the native structural and conformational information. Multidimensional High Resolution Magic Angle Spinning NMR (HRMAS NMR) has evolved to be a powerful technique in a variety of in vivo studies, including live bacterial cells. Existing studies of HRMAS NMR in bacteria, technical consideration of its successful application, and current limitations in studying true human pathogens are briefly reviewed in this report.

Changes of metabolite profile in kainic acid induced hippocampal injury in rats measured by HRMAS NMR

The solid-state high resolution magic angle spinning nuclear magnetic resonance (HRMAS NMR) technique was applied in this work to characterize and quantify the neurochemical changes in the rat hippocampus (CA1 or CA3) after local administration of kainic acid (KA). Intact tissue samples obtained from the KA treated and control brain samples were analyzed using HRMAS NMR. Metabolite profiles from NMR spectra of KA treated and control samples revealed the statistical significant decrease of N-acetylaspartate (NAA) and an increase of choline derivatives in the CA1 and CA3 directly receiving KA injection. Less extensive KA-induced metabolic changes were found in the hippocampi sample from the area contralateral to the site receiving KA administration. These results provided quantitative metabolic information on KA-induced neuronal loss and cell breakdown. In addition, the present study also revealed increased level of gamma-aminobutyric acid (GABA) and glutamate after KA treatment, suggesting that the cellular release of inhibitory and excitatory amino acids can be quantified using this method. KA induced microglia activation was evidenced by increased level of myo-insitol (myo-I). This study demonstrates that ex vivo HRMAS NMR is a useful tool for analyzing and quantifying changes of neurochemistry and cerebral metabolism in the intact brain.

NMR-based metabolomics approach to target biomarkers for human prostate cancer

In the era of genomics and proteomics, metabolomics offers a unique way to probe the underlying biochemistry of malignant transformations. In the context of oncological metabolomics, the study of the global variation of metabolites involved in the development and progression of cancers, few existing techniques offer as much potential to discover biomarkers as nuclear magnetic resonance techniques. The most fundamental magnetic resonance methodologies with regard to human prostate cancer are magnetic resonance spectroscopy and magnetic resonance spectroscopic imaging. Recent in vivo explorations have examined crucial metabolites that may indicate cancerous lesions and have the potential to direct treatment; while ex vivo studies of prostatic fluids and tissues have defined novel diagnostic parameters and indicated that magnetic resonance methodologies will be paramount in future prostate cancer management.

Computer-aided diagnosis of prostate cancer with emphasis on ultrasound-based approaches: a review

This paper reviews the state of the art in computer-aided diagnosis of prostate cancer and focuses, in particular, on ultrasound-based techniques for detection of cancer in prostate tissue. The current standard procedure for diagnosis of prostate cancer, i.e., ultrasound-guided biopsy followed by histopathological analysis of tissue samples, is invasive and produces a high rate of false negatives resulting in the need for repeated trials. It is against these backdrops that the search for new methods to diagnose prostate cancer continues. Image-based approaches (such as MRI, ultrasound and elastography) represent a major research trend for diagnosis of prostate cancer. Due to the integration of ultrasound imaging in the current clinical procedure for detection of prostate cancer, we specifically provide a more detailed review of methodologies that use ultrasound RF-spectrum parameters, B-scan texture features and Doppler measures for prostate tissue characterization. We present current and future directions of research aimed at computer-aided detection of prostate cancer and conclude that ultrasound is likely to play an important role in the field.

Imaging prostate cancer: a multidisciplinary perspective

The major goal for prostate cancer imaging in the next decade is more accurate disease characterization through the synthesis of anatomic, functional, and molecular imaging information. No consensus exists regarding the use of imaging for evaluating primary prostate cancers. Ultrasonography is mainly used for biopsy guidance and brachytherapy seed placement. Endorectal magnetic resonance (MR) imaging is helpful for evaluating local tumor extent, and MR spectroscopic imaging can improve this evaluation while providing information about tumor aggressiveness. MR imaging with superparamagnetic nanoparticles has high sensitivity and specificity in depicting lymph node metastases, but guidelines have not yet been developed for its use, which remains restricted to the research setting. Computed tomography (CT) is reserved for the evaluation of advanced disease. The use of combined positron emission tomography/CT is limited in the assessment of primary disease but is gaining acceptance in prostate cancer treatment follow-up. Evidence-based guidelines for the use of imaging in assessing the risk of distant spread of prostate cancer are available. Radionuclide bone scanning and CT supplement clinical and biochemical evaluation (prostate-specific antigen [PSA], prostatic acid phosphate) for suspected metastasis to bones and lymph nodes. Guidelines for the use of bone scanning (in patients with PSA level > 10 ng/mL) and CT (in patients with PSA level > 20 ng/mL) have been published and are in clinical use. Nevertheless, changes in practice patterns have been slow. This review presents a multidisciplinary perspective on the optimal role of modern imaging in prostate cancer detection, staging, treatment planning, and follow-up.

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

Background

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

Methods

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

Results

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

Conclusion

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

Combined Use of Diffusion-Weighted MRI and 1H MR Spectroscopy to Increase Accuracy in Prostate Cancer Detection

OBJECTIVE

The objective of our study was to establish the sensitivity and specificity for prostate cancer detection using a combined 1H MR spectroscopy and diffusion-weighted MRI approach.

SUBJECTS AND METHODS

Forty-two men (mean age +/- SD, 69.3 +/- 4.7 years) with prostate cancer were studied using endorectal T2-weighted imaging, 2D chemical shift imaging (CSI), and isotropic apparent diffusion coefficient (ADC) maps. Regions of interest (ROIs) were drawn around the entire gland, central gland, and peripheral zone tumor, diagnostically defined as low signal intensity on T2-weighted images within a sextant that was biopsy-positive for tumor. Lack of susceptibility artifact on a gradient-echo B0 map through the slice selected for CSI and no high signal intensity on external array T1-weighted images confirmed the absence of significant hemorrhage after biopsy. CSI voxels were classified as nonmalignant or as tumor (ROI included > or = 30% or > or = 70% tumor). Choline-citrate (Cho/Cit) ratios and average ADCs were calculated for every voxel. A plot of Cho/Cit ratios versus ADCs yielded a line of best separation of tumor voxels from nonmalignant voxels. Receiver operating characteristic (ROC) curves were plotted for Cho/Cit ratios alone, ADCs alone, and a combination of the two.

RESULTS

The Cho/Cit ratios were significantly higher (p < 0.001) and the ADCs were significantly lower (p < 0.006) in tumor-containing voxels than in non-tumor-containing voxels. When voxels containing 30% or more tumor were considered positive, the area under the ROC curves using combined MR spectroscopy and ADC (0.81) was similar to that of Cho/Cit alone (0.79) and better than ADC alone (0.66). When voxels containing 70% or more tumor were considered positive and cutoffs to achieve a 90%-or-greater sensitivity chosen, a combination of Cho/Cit and ADC achieved a significant improvement in specificity compared with Cho/Cit alone (p < 0.0001) or ADC alone (p < 0.0001).

CONCLUSION

When voxels containing > or = 70% tumor are considered positive, the combined use of MR spectroscopy and diffusion-weighted MRI increases the specificity for prostate cancer detection while retaining the sensitivity compared with MR spectroscopy alone or diffusion-weighted MRI alone.

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.

Clinical role of proton magnetic resonance spectroscopy in oncology: brain, breast, and prostate cancer

Standardised proton magnetic resonance spectroscopic imaging (MRSI) was initially developed for routine in-situ clinical assessment of human brain tumours, and its use was later extended for examination of prostate and breast cancers. MRSI coupled with both routine and functional MRI techniques provides more detailed information about a tumour's location and extent of its infiltration than any other modality alone. Information obtained by adding MRSI data to anatomical and functional MRI findings aid in clinical management decisions (such as watchful waiting vs immediate intervention). In this Review, we discuss the current status of proton MRSI, with emphasis on its clinical use to map the location and extent of tumour processes for spectroscopic image-guided biopsy procedures and to monitor treatment paradigms for brain, prostate, and breast cancer.

Quantitative analysis of prostate metabolites using 1H HR-MAS spectroscopy

A method was developed to quantify prostate metabolite concentrations using (1)H high-resolution magic angle spinning (HR-MAS) spectroscopy. T(1) and T(2) relaxation times (in milliseconds) were determined for the major prostate metabolites and an internal TSP standard, and used to optimize the acquisition and repetition times (TRs) at 11.7 T. At 1 degrees C, polyamines (PAs; T(1mean) = 100 +/- 13, T(2mean) = 30.8 +/- 7.4) and citrate (Cit; T(1mean) = 237 +/- 39, T(2mean) = 68.1 +/- 8.2) demonstrated the shortest relaxation times, while taurine (Tau; T(1mean) = 636 +/- 78, T(2mean) = 331 +/- 71) and choline (Cho; T(1mean) = 608 +/- 60, T(2mean) = 393 +/- 81) demonstrated the longest relaxation times. Millimolal metabolite concentrations were calculated for 60 postsurgical tissues using metabolite and TSP peak areas, and the mass of tissue and TSP. Phosphocholine plus glycerophosphocholine (PC+GPC), total choline (tCho), lactate (Lac), and alanine (Ala) concentrations were higher in prostate cancer ([PC+GPC](mean) = 9.34 +/- 6.43, [tCho](mean) = 13.8 +/- 7.4, [Lac](mean) = 69.8 +/- 27.1, [Ala](mean) = 12.6 +/- 6.8) than in healthy glandular ([PC+GPC](mean) = 3.55 +/- 1.53, P < 0.01; [tCho](mean) = 7.06 +/- 2.36, P < 0.01; [Lac](mean) = 46.5 +/- 17.4, P < 0.01; [Ala](mean) = 8.63 +/- 4.91, P = 0.051) and healthy stromal tissues ([PC+GPC](mean) = 4.34 +/- 2.46, P < 0.01; [tCho](mean) = 7.04 +/- 3.10, P < 0.01; [Lac](mean) = 45.1 +/- 18.6, P < 0.01; [Ala](mean) = 6.80 +/- 2.95, P < 0.01), while Cit and PA concentrations were significantly higher in healthy glandular tissues ([Cit](mean) = 43.1 +/- 21.2, [PAs](mean) = 18.5 +/- 15.6) than in healthy stromal ([Cit](mean) = 16.1 +/- 5.6, P < 0.01; [PAs](mean) = 3.15 +/- 1.81, P < 0.01) and prostate cancer tissues ([Cit](mean) = 19.6 +/- 12.7, P < 0.01; [PAs](mean) = 5.28 +/- 5.44, P < 0.01). Serial spectra acquired over 12 hr indicated that the degradation of Cho-containing metabolites was minimized by acquiring HR-MAS data at 1 degree C compared to 20 degrees C.

Metabonomics techniques and applications to pharmaceutical research & development

In this review, the background to the approach known as metabonomics is provided, giving a brief historical perspective and summarizing the analytical and statistical techniques used. Some of the major applications of metabonomics relevant to pharmaceutical Research & Development are then reviewed including the study of various influences on metabolism, such as diet, lifestyle, and other environmental factors. The applications of metabonomics in drug safety studies are explained with special reference to the aims and achievements of the Consortium for Metabonomic Toxicology. Next, the role that metabonomics might have in disease diagnosis and therapy monitoring is provided with some examples, and the concept of pharmacometabonomics as a way of predicting an individual's response to treatment is highlighted. Some discussion is given on the strengths and weaknesses, opportunities of, and threats to metabonomics.