Lonidamine Induced Selective Acidification and De-Energization of Prostate Cancer Xenografts: Enhanced Tumor Response to Radiation Therapy

Prostate cancer is a multi-focal disease that can be treated using surgery, radiation, androgen deprivation, and chemotherapy, depending on its presentation. Standard dose-escalated radiation therapy (RT) in the range of 70-80 Gray (GY) is a standard treatment option for prostate cancer. It could be used at different phases of the disease (e.g., as the only primary treatment when the cancer is confined to the prostate gland, combined with other therapies, or as an adjuvant treatment after surgery). Unfortunately, RT for prostate cancer is associated with gastro-intestinal and genitourinary toxicity. We have previously reported that the metabolic modulator lonidamine (LND) produces cancer sensitization through tumor acidification and de-energization in diverse neoplasms. We hypothesized that LND could allow lower RT doses by producing the same effect in prostate cancer, thus reducing the detrimental side effects associated with RT. Using the Seahorse XFe96 and YSI 2300 Stat Plus analyzers, we corroborated the expected LND-induced intracellular acidification and de-energization of isolated human prostate cancer cells using the PC3 cell line. These results were substantiated by non-invasive 31P magnetic resonance spectroscopy (MRS), studying PC3 prostate cancer xenografts treated with LND (100 mg/kg, i.p.). In addition, we found that LND significantly increased tumor lactate levels in the xenografts using 1H MRS non-invasively. Subsequently, LND was combined with radiation therapy in a growth delay experiment, where we found that 150 µM LND followed by 4 GY RT produced a significant growth delay in PC3 prostate cancer xenografts, compared to either control, LND, or RT alone. We conclude that the metabolic modulator LND radio-sensitizes experimental prostate cancer models, allowing the use of lower radiation doses and diminishing the potential side effects of RT. These results suggest the possible clinical translation of LND as a radio-sensitizer in patients with prostate cancer.

Metabolic Imaging Biomarkers of Response to Signaling Inhibition Therapy in Melanoma

Dabrafenib therapy for metastatic melanoma focuses on blocking growth-promoting signals produced by a hyperactive BRAF protein. We report the metabolic differences of four human melanoma cell lines with diverse responses to dabrafenib therapy (30 mg/kg; oral): WM3918 < WM9838BR < WM983B < DB-1. Our goal was to determine if metabolic changes produced by the altered signaling pathway due to BRAF mutations differ in the melanoma models and whether these differences correlate with response to treatment. We assessed metabolic changes in isolated cells using high-resolution proton magnetic resonance spectroscopy (1H MRS) and supplementary biochemical assays. We also noninvasively studied mouse xenografts using proton and phosphorus (1H/31P) MRS. We found consistent changes in lactate and alanine, either in isolated cells or mouse xenografts, correlating with their relative dabrafenib responsiveness. In xenografts, we also observed that a more significant response to dabrafenib correlated with higher bioenergetics (i.e., increased βNTP/Pi). Notably, our noninvasive assessment of the metabolic status of the human melanoma xenografts by 1H/31P MRS demonstrated early metabolite changes preceding therapy response (i.e., tumor shrinkage). Therefore, this noninvasive methodology could be translated to assess in vivo predictive metabolic biomarkers of response in melanoma patients under dabrafenib and probably other signaling inhibition therapies.

Coherence pathway analysis of J-coupled lipids and lactate and effective suppression of lipids upon the selective multiple quantum coherence lactate editing sequence

Objective:The selective multiple quantum coherence (Sel-MQC) sequence is a magnetic resonance spectroscopy (MRS) technique used to detect lactate and suppress co-resonant lipid signalsin vivo. The coherence pathways of J-coupled lipids upon the sequence, however, have not been studied, hindering a logical design of the sequence to fully attenuate lipid signals. The objective of this study is to elucidate the coherence pathways of J-coupled lipids upon the Sel-MQC sequence and find a strategy to effectively suppress lipid signals from these pathways while keeping the lactate signal.Approach:The product operator formalism was used to express the evolutions of the J-coupled spins of lipids and lactate. The transformations of the product operators by the spectrally selective pulses of the sequence were calculated by using the off-resonance rotation matrices. The coherence pathways and the conversion rates of the individual pathways were derived from them. Experiments were performed on phantoms and two human subjects at 3T.Main results:The coherence pathways contributing to the various lipid resonance signals by the Sel-MQC sequence depending on the gradient ratios and RF pulse lengths were identified. Theoretical calculations of the signals from the determined coherence pathways and signal attenuations by gradients matched the experimental data very well. Lipid signals from fatty tissues of the subjects were successfully suppressed to the noise level by using the gradient ratio -0.8:-1:2 or 1:0.8:2. The new gradient ratios kept the lactate signal the same as with the previously used gradient ratio 0:-1:2.Significance:The study has elucidated the coherence pathways of J-coupled lipids upon the Sel-MQC sequence and demonstrated how lipid signals can be effectively suppressed while keeping lactate signals by using information from the coherence pathway analysis. The findings enable applying the Sel-MQC sequence to lactate detection in an environment of high concentrations of lipids.

SAT-438 Visceral and Marrow Adiposity in Patients with Acromegaly; Relationships to Disease Activity, Markers of Bone Turnover, Bone Mineral Density, and Peripheral Bone Microarchitecture

Adipose tissue (AT) mass, especially visceral (VAT), is reduced in active acromegaly and rises with treatment. Although the effect of acromegaly and its therapy on marrow AT(MAT) is unknown, data in other populations and in vitro, suggest a reciprocal relationship between GH and marrow adiposity. In other groups, VAT and MAT are associated with reduced bone quality and increased vertebral fracture (VF) risk. Therefore, since acromegaly patients have an increased VF incidence, we examined the relationships of VAT and MAT to bone quality in acromegaly. We studied 65 acromegaly subjects (40 men, 25 women, range 18.7-74 yr.) before (n=20) or before and after (n=45) acromegaly therapy by total body multi-slice MRI(n=159)(measurement of VAT, subcutaneous (SAT) and total (TAT) adipose tissue mass), DXA (BMD (n=120) and body composition (n=145)) and HRpQCT (n=35) (microarchitecture of the tibia and radius). Marrow lipid spectra of the tibial diaphysis were acquired by ¹H MRS (PRESS technique)(1.5T MR scanner, Philips) and percentages of bone marrow lipids were quantified (n=53). GH and IGF-1 (n=159) and bone turnover markers (BTM)(n=49) were measured. We examined the relationship between MAT or VAT and GH, IGF-1, age, weight, mass of other MRI measured AT depots, and selected DXA and HRpQCT parameters previously shown to differ in acromegaly compared to healthy subjects and to be associated in other groups with fracture. Data were analyzed by Pearson correlation and the generalized estimating equation (GEE). MAT directly correlated with VAT (r=.249, p=.023) and by HRpQCT (n=13) with bone size (radius: total area (r=.678, p=.01), tibia: total area (r=.535, p=.05)) and trabecular number (r=.543, p=.055). VAT was inversely associated with GH (β= -.017, p<.001), IGF-1 level (expressed as % upper normal limit) (β= -0.004, p=.049) and BTMs (N-Mid Osteocalcin (β= -.0223, p<0.001); CTX (β= -.7283, p=.0134)). VAT was positively associated with age (β=.034, p=.053), weight (β=.072, p <.0001) and with HRpQCT measured bone size (radius: total area (β=.0073, p=.0098); tibia: total area (β= .0049, p <.0001)) and trabecular number (tibia: β=1.9321, p=.0096), and inversely associated with cortical thickness (radius: β= -2.8477, p= .074; tibia: β= -2.3341, p=.0497), trabecular thickness (tibia: β= -92, p<.0001) and total body density (radius β= -.0102, p=.0353; tibia: β= -.0149, p=.003). In summary, VAT is inversely related to acromegaly disease activity, consistent with its known rise as acromegaly is treated. We found that greater VAT is associated with larger bone size and lower bone turnover, but also with some less favorable aspects of bone microarchitecture. MAT correlated with VAT and, in a small number of subjects, with bone size. Whether rising adiposity and reductions in bone turnover with acromegaly therapy are relevant to the skeletal fragility reported in treated acromegaly warrants further study.

Adipose Tissue Redistribution and Ectopic Lipid Deposition in Active Acromegaly and Effects of Surgical Treatment

CONTEXT

GH and IGF-I have important roles in the maintenance of substrate metabolism and body composition. However, when in excess in acromegaly, the lipolytic and insulin antagonistic effects of GH may alter adipose tissue (AT) deposition.

OBJECTIVES

The purpose of this study was to examine the effect of surgery for acromegaly on AT distribution and ectopic lipid deposition in liver and muscle.

DESIGN

This was a prospective study before and up to 2 years after pituitary surgery.

SETTING

The setting was an academic pituitary center.

PATIENTS

Participants were 23 patients with newly diagnosed, untreated acromegaly.

MAIN OUTCOME MEASURES

We determined visceral (VAT), subcutaneous (SAT), and intermuscular adipose tissue (IMAT), and skeletal muscle compartments by total-body magnetic resonance imaging, intrahepatic and intramyocellular lipid by proton magnetic resonance spectroscopy, and serum endocrine, metabolic, and cardiovascular risk markers.

RESULTS

VAT and SAT masses were lower than predicted in active acromegaly, but increased after surgery in male and female subjects along with lowering of GH, IGF-I, and insulin resistance. VAT and SAT increased to a greater extent in men than in women. Skeletal muscle mass decreased in men. IMAT was higher in active acromegaly and decreased in women after surgery. Intrahepatic lipid increased, but intramyocellular lipid did not change after surgery.

CONCLUSIONS

Acromegaly may present a unique type of lipodystrophy characterized by reduced storage of AT in central depots and a shift of excess lipid to IMAT. After surgery, this pattern partially reverses, but differentially in men and women. These findings have implications for understanding the role of GH in body composition and metabolic risk in acromegaly and other clinical settings of GH use.

Abstract 4296: Correlation of the apparent diffusion coefficient of water assessed by diffusion-weighted imaging with treatment outcome in refractory lymphoma patients

The contrast of MR images can be made sensitive to the average motion of water molecules (diffusivity) giving rise to diffusion-weighted imaging (DWI). Intensity maps of the apparent diffusion constant (ADC) of water can be generated from the DWI information and average ADC values of anatomical regions can be assessed. Malignant tissues generally exhibit hypercellularity, increased nucleus-to-cytoplasm ratios, and an increased amount of macromolecules resulting in decreased water diffusivity (lower ADC). Additionally, a response-related ADC increase has been demonstrated in malignancies under therapy. We previously reported that the ADC mean value (in 10-3 mm2 s-1 [SD, n]) of masses of refractory lymphoma patients prior to a new treatment was lower than the ADC mean value of lymph nodes of healthy volunteers (0.91 [0.23, 15] vs. 1.13 [0.14, 10], respectively). This difference was significant (p &lt; 0.01) despite of a large dispersion on the ADC data from the patients. Given this dispersion, we wanted to prove if refractory lymphoma patients with lower ADC values responded differently than those with higher ADC values. Experimental Design: Under ethical review board approval, refractory lymphoma patients underwent a pretreatment MR exam. DWI was acquired using echo-planar imaging with fat suppression and b-values of 0 and 1000 s/mm2 and the ADC of water in the tumor obtained. Time to treatment failure (TTF) was defined as the time between the end of one treatment and the start of a new one. Results: ADC and TTF were obtained in 12 refractory lymphoma patients and divided into those with TTF ≤ 75 days and those with TTF &gt; 75 days. The ADC mean value [SD, n] in patients with TTF ≤ 75 days was 0.73 [0.20, 5] while in those with TTF &gt; 75 days was 1.04 [0.20, 7]. These mean values were significantly different (p &lt; 0.02). Furthermore, the comparison of the ADC mean value of lymph nodes of healthy volunteers with the ADC mean value of refractory patients with TTF ≤ 75 days was highly significant (p &lt; 0.0005) while the comparison between healthy volunteers and patients with TTF &gt; 75 days was not. Discussion: Our results demonstrate that refractory lymphoma patients with tumor masses displaying abnormally low ADC values prior to the start of treatment have poorer treatment outcome than those patients with ADC tumor values that are comparable to those in normal lymph nodes. If low ADC is due to increased tumor cellularity in patients with poorer outcome, this could produce reduced drug availability, thus explaining the substandard outcome. Our results demonstrate an important predictive value of the ADC determination by DWI in refractory lymphoma patients. This together with the fact that DWI is a noninvasive technique and its acquisition is fairly quick makes the ADC a parameter that could become critical for the clinical examination of the patient with refractory lymphoma.

Citation Format: Fernando Arias-Mendoza, Hamed Mojahed, Ahmed Sawas, Owen A. O'Connor. Correlation of the apparent diffusion coefficient of water assessed by diffusion-weighted imaging with treatment outcome in refractory lymphoma patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4296. doi:10.1158/1538-7445.AM2014-4296

Deoxynucleoside stress exacerbates the phenotype of a mouse model of mitochondrial neurogastrointestinal encephalopathy

Balanced pools of deoxyribonucleoside triphosphate precursors are required for DNA replication, and alterations of this balance are relevant to human mitochondrial diseases including mitochondrial neurogastrointestinal encephalopathy. In this disease, autosomal recessive TYMP mutations cause severe reductions of thymidine phosphorylase activity; marked elevations of the pyrimidine nucleosides thymidine and deoxyuridine in plasma and tissues, and somatic multiple deletions, depletion and site-specific point mutations of mitochondrial DNA. Thymidine phosphorylase and uridine phosphorylase double knockout mice recapitulated several features of these patients including thymidine phosphorylase activity deficiency, elevated thymidine and deoxyuridine in tissues, mitochondrial DNA depletion, respiratory chain defects and white matter changes. However, in contrast to patients with this disease, mutant mice showed mitochondrial alterations only in the brain. To test the hypothesis that elevated levels of nucleotides cause unbalanced deoxyribonucleoside triphosphate pools and, in turn, pathogenic mitochondrial DNA instability, we have stressed double knockout mice with exogenous thymidine and deoxyuridine, and assessed clinical, neuroradiological, histological, molecular, and biochemical consequences. Mutant mice treated with exogenous thymidine and deoxyuridine showed reduced survival, body weight, and muscle strength, relative to untreated animals. Moreover, in treated mutants, leukoencephalopathy, a hallmark of the disease, was enhanced and the small intestine showed a reduction of smooth muscle cells and increased fibrosis. Levels of mitochondrial DNA were depleted not only in the brain but also in the small intestine, and deoxyribonucleoside triphosphate imbalance was observed in the brain. The relative proportion, rather than the absolute amount of deoxyribonucleoside triphosphate, was critical for mitochondrial DNA maintenance. Thus, our results demonstrate that stress of exogenous pyrimidine nucleosides enhances the mitochondrial phenotype of our knockout mice. Our mouse studies provide insights into the pathogenic role of thymidine and deoxyuridine imbalance in mitochondrial neurogastrointestinal encephalopathy and an excellent model to study new therapeutic approaches.

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.

Prolonged intracerebral convection-enhanced delivery of topotecan with a subcutaneously implantable infusion pump

Intracerebral convection-enhanced delivery (CED) of chemotherapeutic agents currently requires an externalized catheter and infusion system, which limits its duration because of the need for hospitalization and the risk of infection. To evaluate the feasibility of prolonged topotecan administration by CED in a large animal brain with the use of a subcutaneous implantable pump. Medtronic Synchromed-II pumps were implanted subcutaneously for intracerebral CED in pigs. Gadodiamide (28.7 mg/mL), with or without topotecan (136 μM), was infused at 0.7 mL/24 h for 3 or 10 days. Pigs underwent magnetic resonance imaging before and at 6 times points after surgery. Enhancement and FLAIR+ volumes were calculated in a semi-automated fashion. Magnetic resonance spectroscopy-based topotecan signature was also investigated. Brain histology was analyzed by hematoxylin and eosin staining and with immunoperoxidase for a microglial antigen. CED of topotecan/gadolinium was well tolerated in all cases (n = 6). Maximum enhancement volume was reached at day 3 and remained stable if CED was continued for 10 days, but it decreased if CED was stopped at day 3. Magnetic resonance spectroscopy revealed a decrease in parenchymal metabolites in the presence of topotecan. Similarly, the combination of topotecan and gadolinium infusion led to a FLAIR+ volume that tended to be larger than that seen after the infusion of gadolinium alone. Histological analysis of the brains showed an area of macrophage infiltrate in the ipsilateral white matter upon infusion with topotecan/gadolinium. Intracerebral topotecan CED is well tolerated in a large animal brain for up to 10 days. Intracerebral long-term CED can be achieved with a subcutaneously implanted pump and provides a stable volume of distribution. This work constitutes a proof of principle for the safety and feasibility for prolonged CED, providing a means of continuous local drug delivery that is accessible to the practicing neuro-oncologist.

Skeletal muscle mass in acromegaly assessed by magnetic resonance imaging and dual-photon x-ray absorptiometry

CONTEXT

GH and IGF-I are nitrogen retaining and anabolic, but the impact of long-term exposure to supraphysiological GH and IGF-I, either from endogenous overproduction in acromegaly or exogenous sources, on skeletal muscle (SM) mass is not clear.

OBJECTIVES

The objectives of the study were to assess SM mass by whole-body magnetic resonance imaging (MRI) in acromegaly and test the hypothesis that dual-energy x-ray absorptiometry (DXA) lean tissue mass-derived estimates of SM accurately estimate true SM mass.

DESIGN, SETTING, AND PATIENTS

The design was a cross-sectional study in 27 acromegaly patients compared with predicted models developed in 315 nonacromegaly subjects and to matched controls.

OUTCOME MEASURES

Mass of SM from whole-body MRI and lean tissue from DXA were measured.

RESULTS

SM mass did not differ from predicted or control values in active acromegaly: 31.75 +/- 8.6 kg (acromegaly) vs. 33.06 +/- 8.9 kg (predicted); SM was 95.6 +/- 12.8% of predicted (range 66.7-122%) (P = 0.088). Lean tissue mass (DXA) was higher in acromegaly than controls: 65.91 +/- 15.2 vs. 58.73 +/- 13.5 kg (P < 0.0001). The difference between lean tissue mass (DXA) and SM in acromegaly patients was higher than that in controls (P < 0.0001) consistent with an enlarged non-SM lean compartment in acromegaly. SM mass predicted by DXA correlated highly with SM mass by MRI (r = 0.97, P < 0.0001). SM (MRI) to SM (DXA predicted) ratio was 1.018 (range 0.896-1.159), indicating high agreement of these measures of SM.

CONCLUSIONS

SM mass in active acromegaly patients did not differ from predicted values. SM mass estimated from DXA agreed highly with SM by MRI, supporting the validity of the DXA model in assessing SM in acromegaly and other disorders of GH/IGF-I secretion.

Prediction of treatment response in subtypes of non-Hodgkin's lymphoma by in vivo 31P MR spectroscopy before treatment

8565

Background: To determine if the intracellular tumor marker of phosphoethanolamine plus phosphocholine normalized by nucleotide triphosphates (PPN) monitored non-invasively by phosphorus MR spectroscopy (31P-MRS) correlate with indicators of treatment response in non-Hodgkin's lymphoma (NHL) subtypes. Methods: The PPN value was obtained in 33 diffuse large B-cell lymphomas (DLBCL), 18 follicular lymphomas (FL) and 16 other types (OT) of NHL using in vivo 3D-localized, 1H-irradiated 31P-MRS prior to standard treatment. Results: The PPN values (mean ± standard error) for complete responses (CR) and not complete responses (NCR) in DLBCL were significantly different (CR: 1.42±0.10, n=19 and NCR: 2.25±0.15, n=14; p<0.00002). A Fisher test with a cutoff maximizing PPN sensitivity and specificity (1.78) showed a p<0.004 (sensitivity=0.6, specificity=1.0). Further, when the PPN was combined with the international prognostic index (IPI) to predict treatment response, the Fisher test increased significance (p<0.0002; sensitivity and specificity=0.9). In addition, the two groups dichotomized by the PPN-IPI combination showed a significant difference for drug-free survival (p<0.0001)with one group with survival below 20 months. FL patients did not show PPN significance (CR: 1.40±0.16, n=4 and NCR: 1.75±0.15, n=14). Although this could be due to the lower number of patients, the mean PPN value of the NCR group of FL was significantly lower than that of DLBCL (p<0.01). In the OT group there was only one CR observation but the PPN of its NCR cases was 2.51±0.25, n=13. This value was not significantly different from that of DLBCL but was against that of FL (p<0.007). Conclusions: Our results show that: 1) the pretreatment PPN can predict treatment response in DLBCL identifying a group of DLBCL patients with DFS below 20 months; 2) FL and DLBCL showed distinctive metabolic behaviors; and 3) the number of CR cases was low for FL and OT limiting analysis of PPN until larger cohorts of patients are accrued.

No significant financial relationships to disclose.

In vivo 31P MR spectral patterns and reproducibility in cancer patients studied in a multi-institutional trial

The standardization and reproducibility of techniques required to acquire anatomically localized 31P MR spectra non-invasively while studying tumors in cancer patients in a multi-institutional group at 1.5 T are reported. This initial group of patients was studied from 1995 to 2000 to test the feasibility of acquiring in vivo localized 31P MRS in clinical MR spectrometers. The cancers tested were non-Hodgkin's lymphomas, sarcomas of soft tissue and bone, breast carcinomas and head and neck carcinomas. The best accrual and spectral quality were achieved with the non-Hodgkin's lymphomas. The initial analysis of the spectral values of the sum of phosphoethanolamine plus phosphocholine normalized by the content of nucleotide triphosphates in a homogeneous sample of 32 NHL patients studied by in vivo (31)P MRS showed good reproducibility among different institutions. No statistical differences were found between the institution with the largest number of cases accrued and the rest of the multi-institutional NHL data (2.28 +/- 0.64, mean +/- standard error; n = 17, vs 2.08 +/- 0.14, n = 15). The preliminary data reported demonstrate that the institutions involved in this trial are obtaining reproducible 31P MR spectroscopic data non-invasively from human tumors. This is a fundamental prerequisite for the international cooperative group to be able to demonstrate the clinical value of the normalized determination of phosphoethanolamine plus phosphocholine by 31P MRS as predictor for treatment response in cancer patients.

Correlation of cerebral metabolites with functional outcome in experimental primate stroke using in vivo 1H-magnetic resonance spectroscopy

BACKGROUND AND PURPOSE

Ensuring the translatability of primate stroke models is critical for preclinical testing of cerebroprotective strategies, and such models would benefit from further characterization of the experimental ischemic tissue. Our purpose was to examine the cerebral metabolic response to stroke in baboons with MR spectroscopy and to correlate metabolite levels with functional neurologic outcomes.

METHODS

Seven baboons underwent 1 hour of middle cerebral artery occlusion. At 3 and 10 days, each animal was imaged with traditional MR imaging and multivoxel proton (1)H-MR spectroscopy, and a neurologic examination was performed. Spectra obtained from the infarcted hemisphere of each animal were compared with the contralateral hemisphere, and metabolite levels were correlated with neurologic outcome scores.

RESULTS

Spectra obtained at 3 days postischemia revealed prominent lactate (LAC) resonances and attenuated N-acetylaspartate (NAA) peaks in infarcted hemispheres. Ten-day spectra showed persistence of these findings in animals with large strokes (>30% of the hemisphere), with partial normalization of the spectra in animals with small strokes (<30% of the hemisphere). Mean area under the curve from LAC spectra had a negative correlation with functional outcome by 2 different scoring systems (r(2) = 0.72 and 0.73), whereas NAA showed a positive correlation (r(2) = 0.79 and 0.62).

CONCLUSIONS

The metabolic alterations observed in our primate model of reperfused ischemia by (1)H-MR spectroscopy recapitulate those seen in clinical stroke. Furthermore, correlations between LAC and NAA peaks with functional outcome further suggest that MR spectroscopy may play a role in outcome prediction following cerebral infarction in higher primates.

In vivo measurement of phosphorous markers of disease

Phosphorus Magnetic Resonance Spectroscopy (³¹P-MRS) has been utilized to study energy, carbohydrate, and phospholipid metabolism in vitro and in vivo in live tissues non-invasively. Despite its lack of sensitivity, its application has extended to in situ human tissues and organs since proper signal localization was devised. Follow-up of phosphocreatine in neuromuscular diseases and schizophrenia and follow-up of phospholipid-related molecules in tumors are described here to demonstrate the value of ³¹P-MRS as an imaging technique to determine in vivo markers of disease and in the diagnosis, prognosis, and follow-up of human diseases.

Detection of Fetal Lactate With Two-Dimensional-Localized Proton Magnetic Resonance Spectroscopy

BACKGROUND

Antenatal surveillance is inefficient for accurately detecting fetal compromise. A noninvasive technique for assessing fetal metabolic status would be useful for clinical management.

CASE

Fetal magnetic resonance spectroscopy was performed at 20 weeks in a pregnancy complicated by severe intrauterine growth restriction to determine if lactate, a metabolite associated with fetal hypoxia, was present. Two-dimensional, single-slice proton magnetic resonance spectroscopy was carried out at 1.5 T using a volume-selective, double-spin echo technique. Lactate was detected in fetal back muscle. Fetal death occurred the next day.

CONCLUSIONS

Although this initial report is purely experimental, further development of this technique may prove to be a valuable noninvasive tool in the management of suspected fetal hypoxia.

Methodological standardization for a multi-institutional in vivo trial of localized 31P MR spectroscopy in human cancer research. In vitro and normal volunteer studies

A multi-institutional group has been created to demonstrate the utility of in vivo 31P magnetic resonance spectroscopy (31P-MRS) to study human cancers in vivo. This review is concerned with the novel problems concerning quality control in this large multinational trial of 31P MRS. Our results show that the careful and systematic performance of the quality control tests depicted here (standardized dual 1H/31P tuned radiofrequency probe, quality control procedures, routine use of 1H irradiation while acquiring 31P MR signals) has ensured comparable results between the different institutions. In studies made in vitro, the root-mean-square error was 3.6 %, and in muscle of healthy volunteers in vivo the coefficients of variance for the ratios phosphocreatine/nucleotide-triphosphates, phosphocreatine/noise and nucleotide-triphosphate/noise were 12.2, 7.0 and 10.8 %, respectively. The standardization of the acquisition protocol for in vivo-localized 31P MR spectroscopy across the different institutions has resulted in comparable in vivo data, decreasing the possible problems related to a research study carried out under a multi-institutional setting.

In vivo magnetic resonance spectroscopy in the evaluation of mitochondrial disorders

Magnetic resonance spectroscopy (MRS) has been utilized to study several metabolic pathways in vivo and in live tissues in vitro non-invasively. Despite its inherited lack of sensitivity, its application has extended all the way to in situ human tissues and organs since proper technical advancements were devised. Examples of its application described here demonstrate the value of in vivo MRS as a technique that determines parameters of mitochondrial dysfunction directly and indirectly which could be of value for the diagnosis, prognosis, and follow-up of mitochondrial disorders.

Predicting treatment response in non-Hodgkin’s lymphoma from the pretreatment tumor content of phosphoethanolamine plus phosphocholine1

RATIONALE AND OBJECTIVES

Phosphoethanolamine and phosphocholine, shown to be elevated in tumors and possibly related to apoptotic signaling, have the potential to be prognostic variables of cancer treatment.

MATERIALS AND METHODS

The sum of phosphoethanolamine and phosphocholine normalized by nucleotide-triphosphates was determined in tumors of non-Hodgkin's lymphoma (NHL) patients via in vivo 31P MR spectroscopy.

RESULTS

The normalized sum of phosphoethanolamine and phosphocholine showed significant differences in tumors of patients who had a complete response to treatment against those who did not (t-test: 1.45 +/- 0.15, mean +/- standard error, n = 10 vs. 2.28 +/- 0.15, n = 17, P < .001; Fisher test: P < .04; sensitivity and specificity approximately equal to 70%). This parameter also showed significant differences among treatment responses in the previously untreated and aggressive subgroups and in the low and low-intermediate-risk subgroups determined by the international prognostic index (IPI). Further, distinctly different treatment response cutoffs for the parameter were found in different risk groups. When these risk-dependent cutoffs were used, the Fisher test of the whole group improved (P < .0002, sensitivity 80%, specificity 94%). The normalized sum of phosphoethanolamine and phosphocholine and the IPI were better predictor covariates for time to treatment failure when fitted interactively in a Cox regression (P < .0003) than when fitted independently. When time to treatment failure was used as a surrogate of survival in Kaplan-Meier analysis, the interaction of both covariates segregated the cases significantly (P < .008). There was no significance with each covariate independently.

CONCLUSION

The normalized sum of phosphoethanolamine and phosphocholine measured before treatment successfully predicts long-term response to treatment and time to treatment failure in non-Hodgkin's lymphoma, particularly when combined with the IPI.

Phosphomonoester concentrations differ between chronic lymphocytic leukemia cells and normal human lymphocytes

Levels of phospholipid-related metabolites of chronic lymphocytic leukemia lymphocytes (CLL) and normal human lymphocytes were quantified using phosphorus magnetic resonance spectroscopy. The CLL cells versus normal lymphocytes showed significant increases of phosphoethanolamine(Etn-P) (8.11+/-2.10 mean+/-S.E., micromol/g wet weight, n=12 versus 3.63+/-1.10, n=3, P<or=0.002), phosphocholine (2.10+/-0.37, n=12 versus 0.36+/-0.09, n=3, P<or=0.01), glycerophosphoethanolamine (0.26+/-0.03, n=10 versus 0.11+/-0.05, n=3, P<or=0.004), and glycerophosphocholine (0.33+/-0.03, n=10 versus 0.17+/-0.05, n=3, P<or=0.003). Further, the phospholipid precursor ethanolamine (Eth) was studied in blood and was found significantly lowered in CLL patients (4.6+/-1.6 microM, n=25) compared to normal volunteers (7.7+/-2.5, n=12, P<or=0.001). Increased intermediates with depletion of precursors suggest the presence of sustained phospholipid metabolism activation in CLL.

Prediction of treatment response of head and neck cancers with P-31 MR spectroscopy from pretreatment relative phosphomonoester levels

RATIONALE AND OBJECTIVES

Combinations of chemotherapy and fractionated radiation therapy are the currently preferred nonsurgical treatment methods for squamous cell carcinoma of the head and neck, but to the authors' knowledge there is no reliable marker for predicting therapeutic response. Early identification of nonresponders would allow prompt replacement of ineffective, toxic therapy by alternative, potentially more effective procedures. Frequent regional node involvement facilitates surface coil investigation with phosphorus-31 magnetic resonance spectroscopy.

MATERIALS AND METHODS

P-31 magnetic resonance spectra were acquired from 12 patients before radiation therapy or chemotherapy. In vivo three-dimensional localized P-31 nuclear magnetic resonance chemical shift imaging was performed with a 1.5-T clinical imager and a dual-tuned H-1/P-31 surface coil. Proton decoupling and nuclear Overhauser enhancement were used to improve sensitivity and resolve overlapping signals in the phosphomonoester region of the spectrum.

RESULTS

The average pretreatment ratio of phosphomonoester to beta-nucleoside triphosphate was significantly smaller in complete responders (n = 4) than in incomplete responders (partial responders plus nonresponders, n = 8) (0.0 +/- 0.0 vs 1.22 +/- 0.17 [P = .004]).

CONCLUSION

Results of this preliminary study suggest that H-1-decoupled P-31 magnetic resonance spectroscopy may prove to be a useful predictor of therapeutic response in head and neck cancers.

A new method for spectral decomposition using a bilinear Bayesian approach

A frequent problem in analysis is the need to find two matrices, closely related to the underlying measurement process, which when multiplied together reproduce the matrix of data points. Such problems arise throughout science, for example, in imaging where both the calibration of the sensor and the true scene may be unknown and in localized spectroscopy where multiple components may be present in varying amounts in any spectrum. Since both matrices are unknown, such a decomposition is a bilinear problem. We report here a solution to this problem for the case in which the decomposition results in matrices with elements drawn from positive additive distributions. We demonstrate the power of the methodology on chemical shift images (CSI). The new method, Bayesian spectral decomposition (BSD), reduces the CSI data to a small number of basis spectra together with their localized amplitudes. We apply this new algorithm to a 19F nonlocalized study of the catabolism of 5-fluorouracil in human liver, 31P CSI studies of a human head and calf muscle, and simulations which show its strengths and limitations. In all cases, the dataset, viewed as a matrix with rows containing the individual NMR spectra, results from the multiplication of a matrix of generally nonorthogonal basis spectra (the spectral matrix) by a matrix of the amplitudes of each basis spectrum in the the individual voxels (the amplitude matrix). The results show that BSD can simultaneously determine both the basis spectra and their distribution. In principle, BSD should solve this bilinear problem for any dataset which results from multiplication of matrices representing positive additive distributions if the data overdetermine the solutions.

3D localized in vivo 1H spectroscopy of human brain by using a hybrid of 1D-Hadamard with 2D-chemical shift imaging

We report acquisition of 3D image-guided localized proton spectroscopy (1H-MRS) in the human brain on a standard clinical imager. 3D coverage is achieved with a hybrid of chemical shift imaging (CSI) and transverse Hadamard spectroscopic imaging (HSI). 16 x 16 x 4 arrays of 3.5 and 1 ml voxels were obtained in 27 min. The spatially selective HSI 90 degrees pulses incorporate naturally into a PRESS double spin-echo sequence to subdivide the VOI into four partitions along its short axis. 2D CSI (16 x 16) is performed along the other long axes. Because the hybrid excites the spins in the entire VOI, a square-root-N signal-to-noise-ratio (SNR) gain per given examination time is realized compared with sequentially interleaving N 2D slices. A two-fold gain in sensitivity is demonstrated in the brain for N = 4.

Heteronuclear multivoxel spectroscopy of in vivo human brain: two-dimensional proton interleaved with three-dimensional 1H-decoupled phosphorus chemical shift imaging

Multivoxel, heteronuclear interleaved two-dimensional proton and three-dimensional 1H-decoupled 31P CSI of human brain is demonstrated. This method offers efficient use of limited examination time as patient preparation, coil tuning, shimming and imaging are done only once and the CSI data sets from both nuclei are obtained concurrently. Effective interleaving of 31P and 1H is possible due to the shorter T1s of proton brain metabolites, allowing a 1H acquisition cycle to be inserted into each 31P TR. This way, the entire MRS time is available to both nuclei, increasing their SNR per-unit-time by approximately 12% for 31P and approximately 80% for 1H, compared with sequential detection of equal (45-50 min) length. The spectral resolution and SNR of 31P are further increased through bi-level 1H-decoupling and NOE.

A fast, reliable, automatic shimming procedure using 1H chemical-shift-imaging spectroscopy

The importance and the difficulty of achieving good B0 homogeneity over the volume of interest in in vivo NMR spectroscopy are well known. A fast, reliable, versatile, and fully automatic shimming procedure has been developed, using 3D chemical-shift imaging to measure the field distribution using only the water peak in the sample of interest. The procedure minimizes the mean-square error in the field distribution with respect to a constant field where the signal exists (e.g., the head). This produces a set of linear equations that can be solved by standard matrix methods. The procedure has been applied on a commercial imager producing water linewidths from the entire head as low as 8 Hz at 1.5 T. The mean linewidth and standard deviation from 94 head studies were 11.7 +/- 1.9 Hz.

Investigation of broad resonances in 31P NMR spectra of the human brain in vivo

Broad resonances that lie underneath the familiar small molecule profile of in vivo 31P NMR spectra can make accurate spectral integration of these mobile phosphates difficult. The two major broad components are the phosphate contained in the hydroxyapatite in cranial bone and the phosphodiester moiety in partially mobile membrane phospholipids. They can be removed with post-acquisition processing but this results in distortion of lineshapes and intensities and interferes with accurate quantitation. We have employed an off-resonance saturation procedure to eliminate the bone resonance and isolate the signal from the membrane phospholipids by subtraction. Selective saturation of the phospholipid resonance increases the clarity of the sharp peaks downfield from the phosphocreatine peak. Selective saturation 3-D chemical shift imaging techniques were used to create a localized phospholipid profile of the entire brain simultaneously. Monitoring localized phospholipid concentration may be important in studying demyelinating diseases.

A simple method to fix and extract ATP from rat liver samples

A simple one-step method to fix and extract ATP from rat liver samples is described. The results show that this method is suitable for fixation and extraction of the hepatic ATP content, whereas its simplicity leads to consider it the procedure of choice.

A sensitive multienzymatic assay for the measurement of pyruvate, dihydroxyacetone phosphate, oxaloacetate, and acetoacetate in clear extracts from biological samples

A multienzymatic method for the measurement of pyruvate, dihydroxyacetone phosphate, oxaloacetate, and acetoacetate is presented. The determination procedure is considered suitable because it is simple, sensitive, and its advantages could be demonstrated by comparison with the original methods.

31P NMR studies of adenosine-stimulated ATP synthesis in perfused luteinized ovaries

31P NMR spectroscopy was utilized to study phosphate metabolism of perfused ovaries. In luteinized ovaries, a loss in ATP of approximately 30% with a concomitant acidification was reversed by 50 microM adenosine. The results suggest that in the ovaries, adenosine can serve to regulate ATP concentration during periodic hypoxic challenges.

Hepatic gluconeogenesis from alanine: 13C nuclear magnetic resonance methodology for in vivo studies

This paper describes an experimental protocol designed to optimize 13C NMR spectra from the liver of the living anesthetized rat at 1.9 T. The protocol involves the use of a Helmholtz NMR coil which is positioned around the liver after surgical exposure. 1H decoupling is facilitated by double tuning this coil to both the 1H and the 13C frequencies. The protocol was shown to be suitable for studying the hepatic metabolism of 13C-labeled substrates in vivo by investigating the metabolism of [3-13C]alanine. Labeled glucose, glutamate, glutamine, and aspartate were formed and detected by 13C NMR in vivo in this experiment. The labeling patterns in these metabolites provided evidence that the major flow of alanine carbon into the Krebs cycle is via the pyruvate carboxylase reaction rather than through pyruvate dehydrogenase.

A 1H NMR technique for observing metabolite signals in the spectrum of perfused liver

We have developed a 1H NMR technique to selectively edit the spectrum of perfused liver for specific resonances of metabolites that occur in low concentration. The method employs selective DANTE pulses, which avoid exciting the water signal and at the same time control the J modulation effect in the homonuclear spin-echo experiment. By difference spectroscopy, we have suppressed the background signals from lipids and water and have resolved the CH3 resonance of lactate at 1.33 ppm. Moreover, the technique is highly selective and allows us to select the CH3 resonance of alanine at 1.47 ppm in the presence of the CH3 resonance of lactate at 1.33 ppm, even though the latter was much larger before editing. We have applied this technique to study the metabolic effect of ethanol in perfused mouse liver and have observed that the rate of formation of lactate from pyruvate is increased by a factor of 2.8 when ethanol is added.

Application of multipulse NMR to observe 13C-labeled metabolites in biological systems

Limitations in resolution and sensitivity of 13C NMR spectroscopy have reduced the information obtainable from intact biological systems. With the aim of increasing the information from in vivo 13C NMR two multipulse NMR techniques, the DEPT pulse sequence and the gated spin-echo sequence, were used to obtain edited 13C NMR spectra from different 13C-labeled mammalian tissues. This allowed the separation of the 13C NMR signals from the tissues into subspectra containing either CH, CH2, or CH3 signals, thereby increasing the information obtainable from these spectra. Comparing the two techniques, the DEPT sequence gives more accurate editing than the gated spin-echo sequence but suffers from the difficulty of determining 1H pulse angles in vivo.