Characterisation of paediatric brain tumours by their MRS metabolite profiles.

1H-magnetic resonance spectroscopy (MRS) has the potential to improve the noninvasive diagnostic accuracy for paediatric brain tumours. However, studies analysing large, comprehensive, multicentre datasets are lacking, hindering translation to widespread clinical practice. Single-voxel MRS (point-resolved single-voxel spectroscopy sequence, 1.5 T: echo time [TE] 23-37 ms/135-144 ms, repetition time [TR] 1500 ms; 3 T: TE 37-41 ms/135-144 ms, TR 2000 ms) was performed from 2003 to 2012 during routine magnetic resonance imaging for a suspected brain tumour on 340 children from five hospitals with 464 spectra being available for analysis and 281 meeting quality control. Mean spectra were generated for 13 tumour types. Mann-Whitney U-tests and Kruskal-Wallis tests were used to compare mean metabolite concentrations. Receiver operator characteristic curves were used to determine the potential for individual metabolites to discriminate between specific tumour types. Principal component analysis followed by linear discriminant analysis was used to construct a classifier to discriminate the three main central nervous system tumour types in paediatrics. Mean concentrations of metabolites were shown to differ significantly between tumour types. Large variability existed across each tumour type, but individual metabolites were able to aid discrimination between some tumour types of importance. Complete metabolite profiles were found to be strongly characteristic of tumour type and, when combined with the machine learning methods, demonstrated a diagnostic accuracy of 93% for distinguishing between the three main tumour groups (medulloblastoma, pilocytic astrocytoma and ependymoma). The accuracy of this approach was similar even when data of marginal quality were included, greatly reducing the proportion of MRS excluded for poor quality. Children's brain tumours are strongly characterised by MRS metabolite profiles readily acquired during routine clinical practice, and this information can be used to support noninvasive diagnosis. This study provides both key evidence and an important resource for the future use of MRS in the diagnosis of children's brain tumours.

A Phase I Dose-escalation Study of AZD3965, an Oral Monocarboxylate Transporter 1 Inhibitor, in Patients with Advanced Cancer.

PURPOSE: Inhibition of monocarboxylate transporter (MCT) 1-mediated lactate transport may have cytostatic and/or cytotoxic effects on tumor cells. We report results from the dose-escalation part of a first-in-human trial of AZD3965, a first-in-class MCT1 inhibitor, in advanced cancer. PATIENTS AND METHODS: This multicentre, phase I, dose-escalation and dose-expansion trial enrolled patients with advanced solid tumors or lymphoma and no standard therapy options. Exclusion criteria included history of retinal and/or cardiac disease, due to MCT1 expression in the eye and heart. Patients received daily oral AZD3965 according to a 3+3 then rolling six design. Primary objectives were to assess safety and determine the MTD and/or recommended phase II dose (RP2D). Secondary objectives for dose escalation included measurement of pharmacokinetic and pharmacodynamic activity. Exploratory biomarkers included tumor expression of MCT1 and MCT4, functional imaging of biological impact, and metabolomics. RESULTS: During dose escalation, 40 patients received AZD3965 at 5-30 mg once daily or 10 or 15 mg twice daily. Treatment-emergent adverse events were primarily grade 1 and/or 2, most commonly electroretinogram changes (retinopathy), fatigue, anorexia, and constipation. Seven patients receiving ≥20 mg daily experienced dose-limiting toxicities (DLT): grade 3 cardiac troponin rise (n = 1), asymptomatic ocular DLTs (n = 5), and grade 3 acidosis (n = 1). Plasma pharmacokinetics demonstrated attainment of target concentrations; pharmacodynamic measurements indicated on-target activity. CONCLUSIONS: AZD3965 is tolerated at doses that produce target engagement. DLTs were on-target and primarily dose-dependent, asymptomatic, reversible ocular changes. An RP2D of 10 mg twice daily was established for use in dose expansion in cancers that generally express high MCT1/low MCT4).

Clinical applications of in vivo magnetic resonance spectroscopy in oncology.

Magnetic resonance spectroscopy (MRS) can be performed in vivo using commercial MRI systems to obtain biochemical information about tissues and cancers. Applications in brain, prostate and breast aid lesion detection and characterisation (differential diagnosis), treatment planning and response assessment. Multi-centre clinical trials have been performed in all these tissues. Single centre studies have been performed in many other tissues including cervix, uterus, musculoskeletal and liver. While generally MRS is used to study endogenous metabolites it has also been used in drug studies, for example those that include 19F as part of their structure. Recently the hyperpolarisation of compounds enriched with 13C such as [1-13C] pyruvate has been demonstrated in animal models and now in preliminary clinical studies, permitting the monitoring of biochemical processes with unprecedented sensitivity. This review briefly introduces the underlying methods and then discusses the current status of these applications.

DCE-MRI, DW-MRI, and MRS in Cancer: Challenges and Advantages of Implementing Qualitative and Quantitative Multi-parametric Imaging in the Clinic.

Multi-parametric magnetic resonance imaging (mpMRI) offers a unique insight into tumor biology by combining functional MRI techniques that inform on cellularity (diffusion-weighted MRI), vascular properties (dynamic contrast-enhanced MRI), and metabolites (magnetic resonance spectroscopy) and has scope to provide valuable information for prognostication and response assessment. Challenges in the application of mpMRI in the clinic include the technical considerations in acquiring good quality functional MRI data, development of robust techniques for analysis, and clinical interpretation of the results. This article summarizes the technical challenges in acquisition and analysis of multi-parametric MRI data before reviewing the key applications of multi-parametric MRI in clinical research and practice.

Distortion correction of echo-planar diffusion-weighted images of uterine cervix.

PURPOSE: To investigate the clinical utility of the reverse gradient algorithm in correcting distortions in diffusion-weighted images of the cervix and for increasing diagnostic performance. MATERIALS AND METHODS: Forty-one patients ages 25-72 years (mean 40 ± 11 years) with suspected or early stage cervical cancer were imaged at 3T using an endovaginal coil. T2 -weighted (W) and diffusion-weighted images with right and left phase-encode gradient directions were obtained coronal to the cervix (b = 0, 100, 300, 500, 800 s mm(-2) ). Differences in angle of the endocervical canal to the x-axis between T2 W and right-gradient, left-gradient, and corrected images were measured. Uncorrected and corrected images were assessed for diagnostic performance when viewed together with T2 W images by two independent observers against subsequent histology. RESULTS: The angles of the endocervical canal relative to the x-axis were significantly different between the T2 W images and the right-gradient images (P = 0.007), approached significance for left-gradient images (P = 0.055), and were not significantly different after correction (P = 0.95). Corrected images enabled a definitive diagnosis in 34% (n = 14) of patients classified as equivocal on uncorrected images. Tumor volume in this subset was 0.18 ± 0.44 cm(3) (mean ± SD; sensitivity of detection 100% [8/8], specificity 50% [3/6] for an experienced observer). Correction did not improve diagnostic performance for the less-experienced observer. CONCLUSION: Distortion-corrected diffusion-weighted images improved correspondence with T2 W images and diagnostic performance in a third of cases.

Determining the chemical exchange saturation transfer (CEST) behavior of citrate and spermine under in vivo conditions.

PURPOSE: To estimate the exchange rates of labile (1) H in citrate and spermine, metabolites present in prostatic secretions, to predict the size of the citrate and spermine CEST effects in vivo. METHODS: CEST z-spectra were acquired at high-field [11.7 Tesla (T)] from citrate and spermine solutions at physiological pH (6.5) using saturation power 6 µT. CEST was performed at different temperatures to determine exchange regimes (slow, intermediate or fast). For low pH solutions of spermine, exchange rates were estimated from resonance line width, fitting z-spectra using the Bloch equations incorporating exchange, and using quantifying exchange using saturation time experiments (QUEST). These rates were extrapolated to physiological pH. RESULTS: Citrate showed little CEST effect at pH 6.5 and temperature (T) = 310 K (maximum 0.001% mM(-1) ), indicating fast exchange, whereas spermine showed greater CEST effects (maximum 0.2% mM(-1) ) indicating intermediate-to-fast exchange. Extrapolating data acquired from low pH spermine solutions predicts exchange rates at pH 6.5 and T of 310 K of at least 2 × 10(4) s(-1) . CONCLUSION: Citrate and spermine show minimal CEST effects at 11.7T even using high saturation power. These effects would be much less than 2% at clinical field-strengths due to relatively faster exchange and would be masked by CEST from proteins. Magn Reson Med 76:742-746, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Radiotherapy planning using MRI.

The use of magnetic resonance imaging (MRI) in radiotherapy (RT) planning is rapidly expanding. We review the wide range of image contrast mechanisms available to MRI and the way they are exploited for RT planning. However a number of challenges are also considered: the requirements that MR images are acquired in the RT treatment position, that they are geometrically accurate, that effects of patient motion during the scan are minimized, that tissue markers are clearly demonstrated, that an estimate of electron density can be obtained. These issues are discussed in detail, prior to the consideration of a number of specific clinical applications. This is followed by a brief discussion on the development of real-time MRI-guided RT.

TE = 32 ms vs TE = 100 ms echo-time (1)H-magnetic resonance spectroscopy in prostate cancer: Tumor metabolite depiction and absolute concentrations in tumors and adjacent tissues.

PURPOSE: To compare the depiction of metabolite signals in short and long echo time (TE) prostate cancer spectra at 3T, and to quantify their concentrations in tumors of different stage and grade, and tissues adjacent to tumor. MATERIALS AND METHODS: First, single-voxel magnetic resonance imaging (MRI) spectra were acquired from voxels consisting entirely of tumor, as defined on T2-weighted and diffusion-weighted (DW)-MRI and from a biopsy-positive octant, at TEs of 32 msec and 100 msec in 26 prostate cancer patients. Then, in a separate cohort of 26 patients, single-voxel TE = 32 msec MR spectroscopy (MRS) was performed over a partial-tumor region and a matching, contralateral normal-appearing region, defined similarly. Metabolite depiction was compared between TEs using Cramér-Rao lower bounds (CRLB), and absolute metabolite concentrations were calculated from TE = 32 msec spectra referenced to unsuppressed water spectra. RESULTS: Citrate and spermine resonances in tumor were better depicted (had significantly lower CRLB) at TE = 32 msec, while the choline resonance was better depicted at TE = 100 msec. Citrate and spermine concentrations were significantly lower in patients of more advanced stage, significantly lower in Gleason grade 3+4 than 3+3 tumors, and significantly lower than expected from the tumor fraction in partial-tumor voxels (by 14 mM and 4 mM, respectively, P < 0.05). CONCLUSION: Citrate and spermine resonances are better depicted at short TE than long TE in tumors. Reduction in these concentrations is related to increasing tumor stage and grade in vivo, while reductions in the normal-appearing tissues immediately adjacent to tumor likely reflect tumor field effects.

Single-shot single-voxel lactate measurements using FOCI-LASER and a multiple-quantum filter.

Measurement of tissue lactate using (1) H MRS is often confounded by overlap with intense lipid signals at 1.3 ppm. Single-voxel localization using PRESS is also compromised by the large chemical shift displacement between voxels for the 4.1 ppm (-CH) resonance and the 1.3 ppm -CH3 resonance, leading to subvoxels with signals of opposite phase and hence partial signal cancellation. To reduce the chemical shift displacement to negligible proportions, a modified semi-LASER sequence was written ("FOCI-LASER", abbreviated as fLASER) using FOCI pulses to permit high RF bandwidth even with the limited RF amplitude characteristic of clinical MRI scanners. A further modification, MQF-fLASER, includes a selective multiple-quantum filter to detect lactate and reject lipid signals. The sequences were implemented on a Philips 3 T Achieva TX system. In a solution of brain metabolites fLASER lactate signals were 2.7 times those of PRESS. MQF-fLASER lactate was 47% of fLASER (the theoretical maximum is 50%) but still larger than PRESS lactate. In oil, the main 1.3 ppm lipid peak was suppressed to less than 1%. Enhanced suppression was possible using increased gradient durations. The minimum detectable lactate concentration was approximately 0.5 mM. Coherence selection gradients needed to be at the magic angle to avoid large water signals derived from intermolecular multiple-quantum coherences. In pilot patient measurements, lactate peaks were often observed in brain tumours, but not in cervix tumours; lipids were effectively suppressed. In summary, compared with PRESS, the fLASER sequence yields greatly superior sensitivity for direct detection of lactate (and equivalent sensitivity for other metabolites), while the single-voxel single-shot MQF-fLASER sequence surpasses PRESS for lactate detection while eliminating substantial signals from lipids. This sequence will increase the potential for in vivo lactate measurement as a biomarker in targeted anti-cancer treatments as well as in measurements of tissue hypoxia.

Comparison of three reference methods for the measurement of intracellular pH using 31P MRS in healthy volunteers and patients with lymphoma.

31P magnetic resonance spectroscopy (31P MRS) can measure intracellular pH (pHi) using the chemical shift difference between pH-dependent inorganic phosphate (Pi) and a pH-independent reference peak. This study compared three different frequency reference peaks [phosphocreatine (PCr), α resonance of adenosine triphosphate (αATP) and water (using 1H MRS)] in a cohort of 10 volunteers and eight patients with non-Hodgkin's lymphoma (NHL). Well-resolved chemical shift imaging (CSI) spectra were acquired on a 1.5T scanner for muscle, liver and tumour. The pH was calculated for all volunteers and patients using the available methods. The consistency of the resulting pH was evaluated. The direct Pi­PCr method was best for those spectra with a very well-defined PCr, such as muscle (pH=7.05 ± 0.02). In liver, the Pi­αATP method gave more consistent results (pH=7.30 ± 0.06) than the calibrated water-based method (pH=7.27 ± 0.11). In NHL nodes, the measured pH using the Pi­αATP method was 7.25 ± 0.12. Given that the measured range includes some biological variation in individual patients, treatment-related changes of the order of 0.1 pH units should be detectable.

Evaluation of short-TE (1)H MRSI for quantification of metabolites in the prostate.

Back-to-back (1)H MRSI scans, using an endorectal and phased-array coil combination, were performed on 18 low-risk patients with prostate cancer at 3 T, employing TEs of 32 and 100 ms in order to compare metabolite visualization at each TE. Outer-volume suppression of lipid signals was performed using regional saturation (REST) slabs and the quantification of spectra at both TEs was achieved with the quantitation using quantum estimation (QUEST) routine. Metabolite nulling experiments in an additional five patients found that there were negligible macromolecule background signals in prostate spectra at TE = 32 ms. Metabolite visibility was judged using the criterion Cramér-Rao lower bound (CRLB)/amplitude < 20%, and metabolite concentrations were corrected for relaxation effects and referenced to the data acquired in corresponding water-unsuppressed MRSI scans. For the first time, the prostate metabolites spermine and myo-inositol were quantified individually in vivo, together with citrate, choline and creatine. All five metabolite visibilities were higher in TE = 32 ms MRSI than in TE = 100 ms MRSI. At TE = 32 ms, citrate was visible in 99.0% of lipid-free spectra, whereas, at TE = 100 ms, no metabolite simulation of citrate matched the in vivo peaks. Spermine, choline and creatine were visualised separately in 30.4% more spectra at TE = 32 ms than at TE = 100 ms, and myo-inositol in 72.5% more spectra. T2 values were calculated for spermine (53 ± 16 ms), choline (62 ± 17 ms) and myo-inositol (90 ± 48 ms). Data from the TE = 32 ms spectra showed that the concentrations of citrate and spermine secretions were positively correlated in both the peripheral zone and central gland (R(2) = 0.73 and R(2) = 0.43, respectively), and that the citrate content was significantly higher in the former at 64 ± 22 mm than in the latter at 32 ± 16 mm (p = 0.01). However, lipid contamination at TE = 32 ms was substantial; therefore, to make clinical use of the greater visualisation of prostate metabolites at TE = 32 ms rather than at TE = 100 ms, three-dimensional MRSI at TE = 32 ms with effective lipid suppression must be implemented.

Molecular and metabolic consequences following E6 transfection in an isogenic ovarian cell line (A2780) pair.

AIMS: To examine molecular and metabolic consequences of HPV-16 viral- protein E6, which targets p53 for degradation, in A2780 (ovarian cancer) cells. METHODS: Isogenic derivatives of A2780 cells, with empty-vector (E6-) or E6 (E6+) transfection, were cultured. Intracellular metabolites, fatty acids, and the flux of glutamine, glucose, alanine and lactate in proliferation (Day 2) and confluence (Day 4) were determined using MRS. Western blotting confirmed p53 status, protein expressions related to AKT, ERK and mTOR signalling, and phospholipid metabolism. RESULTS: Growth rate was slower in E6+ cells compared with E6-, resulting in reduced glycolysis, amino acid uptake and fatty acid synthesis. Glutamine metabolism, glycerophosphocholine (GPC), and protein expressions of cytosolic PLA2 (cPLA2) and p-cPLA2 increased in E6+ cells. Despite decreased ERK and AKT signalling, expression of S6RP and p-S6RP downstream of mTOR remained unaffected in E6+ cells. E6+ cells were more invasive and migrate faster than the E6- cells. CONCLUSION: E6+ had slower growth than E6- cells with reduced metabolism, but E6+ cells maintained cellular homeostasis through glutamine metabolism when compared with E6- at Day 2. The ability to migrate and form larger colonies may provide the E6+ cells with a growth advantage.

Noninvasive phosphorus magnetic resonance spectroscopic imaging predicts outcome to first-line chemotherapy in newly diagnosed patients with diffuse large B-cell lymphoma.

RATIONALE AND OBJECTIVES: Based on their association with malignant proliferation, using noninvasive phosphorus MR spectroscopic imaging ((31)P MRSI), we measured the tumor content of the phospholipid-related phosphomonoesters (PME), phosphoethanolamine and phospholcholine, and its correlation with treatment outcome in newly diagnosed patients with diffuse large B-cell lymphoma (DLBCL) receiving standard first-line chemotherapy. EXPERIMENTAL DESIGN: The PME value normalized to nucleoside triphosphates (PME/NTP) was measured using (31)P MRSI in tumor masses of 20 patients with DLBCL before receiving standard first-line chemotherapy. Response at 6 months was complete in 13 patients and partial in seven. Time to treatment failure (TTF) was ≤11 months in eight patients, from 18 to 30 months in three, and ≥60 months in nine. RESULTS: On a t test, the pretreatment tumor PME/NTP mean value (SD, n) of patients with a complete response at 6 months was 1.42 (0.41, 13), which was significantly different from the value of 2.46 (0.40, 7) in patients with partial response (P < .00001). A Fisher test significantly correlated the PME/NTP values with response at 6 months (sensitivity and specificity at 0.85, P < .004) while a Cox proportional hazards regression significantly correlated the PME/NTP values with TTF (hazard ratio = 5.21, P < .02). A Kaplan-Meier test set apart a group entirely composed of patients with TTF ≤ 11 months (hazard ratio = 8.66, P < .00001). CONCLUSIONS: The pretreatment tumor PME/NTP values correlated with response to treatment at 6 months and time to treatment failure in newly diagnosed patients with DLBCL treated with first-line chemotherapy, and therefore they could be used to predict treatment outcome in these patients.

Histone deacetylase inhibition increases levels of choline kinase α and phosphocholine facilitating noninvasive imaging in human cancers.

Histone deacetylase (HDAC) inhibitors are currently approved for cutaneous T-cell lymphoma and are in mid-late stage trials for other cancers. The HDAC inhibitors LAQ824 and SAHA increase phosphocholine (PC) levels in human colon cancer cells and tumor xenografts as observed by magnetic resonance spectroscopy (MRS). In this study, we show that belinostat, an HDAC inhibitor with an alternative chemical scaffold, also caused a rise in cellular PC content that was detectable by (1)H and (31)P MRS in prostate and colon carcinoma cells. In addition, (1)H MRS showed an increase in branched chain amino acid and alanine concentrations. (13)C-choline labeling indicated that the rise in PC resulted from increased de novo synthesis and correlated with an induction of choline kinase α expression. Furthermore, metabolic labeling experiments with (13)C-glucose showed that differential glucose routing favored alanine formation at the expense of lactate production. Additional analysis revealed increases in the choline/water and phosphomonoester (including PC)/total phosphate ratios in vivo. Together, our findings provide mechanistic insights into the impact of HDAC inhibition on cancer cell metabolism and highlight PC as a candidate noninvasive imaging biomarker for monitoring the action of HDAC inhibitors.

Comparison of NMR lipid profiles in mitotic arrest and apoptosis as indicators of paclitaxel resistance in cervical cell lines.

This study aimed to characterize changes in lipid saturation using magnetic resonance spectroscopy of sensitive (HeLa) and resistant (C33A; Me180) cervical cancer cell lines following exposure to paclitaxel to explore lipid profiles as biomarkers of drug resistance. Spectra were acquired at 11.74 T. Flow cytometry, electron, and confocal microscopy assessed cellular morphology. Western blots assessed cytoplasmic phospholipase A(2) , fatty acid synthase, and acyl-CoA synthetase1 expression. After 24 h of paclitaxel exposure, >60% of cells showed mitotic arrest. At 48 h, HeLa cells showed apoptosis while C33A/Me180 cells showed normal morphology indicating resistance. MR-visible lipids increased significantly in all lines at 24 h with further increases at 48 h; resistant lines showed smaller increases than HeLa. Cytoplasmic phospholipase A(2) and fatty acid synthase levels were unchanged at 24 h and dropped at 48 h in HeLa; acyl-CoA synthetase1 was higher in Me180/C33A than in HeLa controls but did not increase significantly. The percentage of cells displaying lipid droplets increased significantly at 24 and 48 h in all lines; droplet size increased only in HeLa cells. Droplet number was >3-4× greater in apoptotic compared with mitotic-arrested cells. Apoptotic cells accumulate unsaturated fatty acids in large (relative to control) droplets; resistant lines accumulated smaller droplets with less triglycerides.

Noninvasive detection of carboxypeptidase G2 activity in vivo.

The pseudomonad protein, carboxypeptidase G2 (CPG2), is a prodrug-activating enzyme utilized in the targeted chemotherapy strategies of antibody- and gene-directed enzyme prodrug therapy (ADEPT and GDEPT). We have developed a noninvasive imaging approach to monitor CPG2 activity in vivo that will facilitate the preclinical and clinical development of CPG2-based ADEPT and GDEPT strategies. Cleavage of the novel reporter probe, 3,5-difluorobenzoyl-L-glutamic acid (3,5-DFBGlu), by CPG2, in human colon adenocarcinoma WiDr xenografts engineered to stably express CPG2, was monitored using (19)F MRSI. The high signal-to-noise ratio afforded by the two MR-equivalent (19)F nuclei of 3,5-DFBGlu, and the 1.4 ppm (19)F chemical shift difference on CPG2-mediated cleavage, enabled the dynamics and quantification of the apparent pharmacokinetics of 3,5-DFBGlu and its CPG2-mediated cleavage in the tumor to be evaluated. In addition, the apparent rate of increase of 3,5-difluorobenzoic acid concentration could also provide a biomarker of CPG2 activity levels in tumors of patients undergoing CPG2-based therapies, as well as a biomarker of treatment response. The addition of in vivo reporter probes, such as 3,5-DFBGlu, to the armamentarium of prodrugs cleaved by CPG2 affords new applications for CPG2 as a gene reporter of transgene expression.

The effect of experimental conditions on the detection of spermine in cell extracts and tissues.

The aim of this work was to investigate the effect of experimental conditions on the visibility of polyamines. In solution the chemical shift of the three groups of peaks (at approximately 1.8, 2.1 and 3.1 ppm) were found to be pH dependent. Relaxation times in aqueous solution at pH 7.0, 298 K and 11.74 T were measured to be: putrescine (T(1) = 2.49 s, T(2) = 2.07 s), spermidine (T(1) = 1.27 s, T(2) = 1.05 s) and spermine (T(1) = 1.02 s, T(2) = 0.82 s). Simple spin-echo sequences could not be used to measure T(2) as the spins also experience phase evolution from homonuclear coupling which imposes a modulation on the T(2) decay curve. This modulation is eliminated by using CPMG sequences with an echo spacing of <500 micros. Relaxation times for spermine in solution in presence of metal ions and protein showed that metal ions had little effect on T(2); however, addition of 15 mg/ml bovine serum albumin reduced T(2) of spermine (0.41 s at 298 K and 0.19 s at 277 K) but was not as short as the T(2) of the polyamine peak in prostatic tissue (0.03 s at 277 K). The MR visibility of polyamines in prostate cell extracts, PC-3 xenograft (intact as well as extracted) and intact human prostatic tissues were investigated. Polyamines were not detected in methanol/chloroform extracts, but were visible in perchloric acid extracts of prostate tumour cells. No polyamines were detected in the HR MAS spectra of three samples of whole PC-3 xenograft tissue studied. In summary, the chemical shift of polyamine species is pH dependent, while protein binding causes peak broadening and reduction in T(2). Perchloric acid extraction improves visibility of intracellular polyamines, but whole tissue polyamines are not seen in xenografts without epithelial/ ductal structure.

Evaluation of magnetic resonance diffusion and spectroscopy measurements as predictive biomarkers in stage 1 cervical cancer.

OBJECTIVE: To establish whether ADC and total choline were significantly different between cervical tumors with different histological characteristics (type, degree of differentiation, presence or absence of lymphovascular invasion, lymph-node involvement) in order to establish their role as predictive biomarkers. METHODS: 62 patients with stage 1 cervical cancer were scanned at 1.5 T. T2-weighted imaging (TR/TE=4500/80 ms), to identify tumor and normal cervix, was followed by diffusion-weighted imaging (TR/TE=2500/69 ms; 5 b-values 0, 100, 300, 500 and 800 s/mm(2)) and MR spectroscopic imaging (15 mm slice, 7.5 mm in-plane resolution, TR=888 ms). Regions of interest in normal cervix and tumor were drawn on apparent diffusion coefficient (ADC) maps by an expert observer with reference to the T2-weighted images. ADCs were calculated using a monoexponential fit of data from all b-values. MR spectra in voxels designated as tumor (>30% tumor) or non-tumor were quantified using LCModel and referenced to tissue water. RESULTS: There was a statistically significant difference between the ADC of tumor regions (1117+/-183x10(-6) mm(2)/s) and of selected normal regions (1724+/-198x10(-6) mm(2)/s; p<0.001), and between tumors that were well/moderately differentiated (1196+/-181x10(-6) mm(2)/s) compared with those that were poorly differentiated (1038+/-153x10(-6) mm(2)/s; p=0.016). There was no significant difference between the ADCs of the tumors when separated by other characteristics (tumor type, lymphovascular invasion, lymph-node metastases), or between measured total choline in any of the groups. CONCLUSION: ADCs are lower in cancer compared to normal cervical tissue, with degree of tumor differentiation contributing to this difference.

MRI in the detection of prostate cancer: combined apparent diffusion coefficient, metabolite ratio, and vascular parameters.

OBJECTIVE: The purpose of this study was to compare apparent diffusion coefficients, metabolic ratios, and vascularity values within histologically defined prostate tumors with those in nontumor tissue to determine which functional parameter or combination of parameters is best for differentiating tumor from nontumor tissue. SUBJECTS AND METHODS: Twenty patients due for prostatectomy underwent endorectal MRI at 1.5 T. Transverse T2-weighted, diffusion-weighted, 2D chemical shift, and dynamic contrast-enhanced images were acquired. After prostatectomy, the gland was sectioned transversely. Fresh slices and stained whole-mount sections with histologically defined tumor outlines were photographed. The tumor outlines were mapped onto images, and the apparent diffusion coefficient (ADC), choline-to-citrate (Cho/cit) ratio, and vascularity of the histologically defined tumor, normal peripheral zone, and central gland were quantitatively measured. Area under the receiver operating characteristics (ROC) curve (A(z)) was used to determine the sensitivity and specificity of parameter combinations in cancer detection. RESULTS: In tumor regions larger than 1 cm(2), the Cho/cit ratio was higher in tumor than in nontumor tissue (p < 0.001), in the peripheral zone alone (p = 0.007), and in the central gland alone (p = 0.005). ADC was lower and tumor vascularity greater in tumor than in nontumor tissue (ADC, p = 0.003; initial area under the gadolinium plasma concentration-time curve [initial gadolinium AUC], p = 0.012; forward rate constant [K(trans)], p = 0.011; return rate constant [k(ep)], p = 0.036). No single parameter had a significantly greater A(z) (ADC, 0.71; Cho/cit ratio, 0.79; initial gadolinium AUC, 0.60; K(trans), 0.62; k(ep), 0.65). Pairs of parameters, however, did increase A(z): ADC and initial gadolinium AUC (A(z) = 0.94) versus ADC (p = 0.001) and initial gadolinium AUC (p < 0.001); ADC and Cho/cit ratio (A(z) = 0.94) versus ADC (p = 0.001) and Cho/cit ratio (not significant); and Cho/cit ratio and initial gadolinium AUC (A(z) = 0.88) versus Cho/cit ratio (not significant) and initial gadolinium AUC (p < 0.001). All three functional techniques together had an A(z) of 0.95, showing no further improvement. CONCLUSION: The combination of two functional parameters is associated with significant improvement in prostate cancer detection over use of any parameter alone. Use of a third parameter does not increase the rate of detection.

Hyperpolarized (13)C magnetic resonance detection of carboxypeptidase G2 activity.

Carboxypeptidase G2 (CPG2) is a bacterial enzyme that is currently employed in a range of targeted cancer chemotherapy strategies such as gene-directed enzyme prodrug therapy (GDEPT). Employing dynamic nuclear polarization (DNP) and natural abundance (13)C magnetic resonance spectroscopy (MRS), we observed the CPG2-mediated conversion of a novel hyperpolarized reporter probe 3,5-difluorobenzoyl-L-glutamic acid (3,5-DFBGlu) to 3,5-difluorobenzoic acid (3,5-DFBA) and L-glutamic acid (L-Glu) in vitro. Isotopic labeling of the relevant nuclei with (13)C in 3,5-DFBGlu or related substrates will yield a further factor of 100 increase in the signal-to-noise. We discuss the feasibility of translating these experiments to generate metabolic images of CPG2 activity in vivo.