NMR in cancer. I. High resolution spectroscopy of tumors

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

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

Interim results of a randomized trial of mitomycin C as an adjunct to radical radiotherapy in the treatment of locally advanced squamous-cell carcinoma of the cervix

The purpose of this study was to determine the efficacy of mitomycin C as an adjunct to radiotherapy for the treatment of locally advanced cervix cancer. Patients with squamous-cell carcinoma of the cervix, stages IB2-IVA, were randomized to receive radiotherapy alone or radiotherapy with concomitant mitomycin C. An initial cohort of 160 patients, having a mean follow-up of 46 months, is analyzed. Intravenous mitomycin C, 15 mg/M(2), was given on the first and sixth week of radiotherapy. The 78 patients in the radiotherapy with mitomycin C group and 82 patients in the radiotherapy alone group have a comparable distribution by age and stage (mean age 47 years; stage IB 3%, IIA 11%, IIB 48%, IIIA 1%, IIIB 36%, IVA 3%). The four-year actuarial survival rates for radiotherapy with mitomycin C and radiotherapy alone were 72% and 56%, respectively (P = 0.13). The four-year actuarial disease-free survival rates for radiotherapy with mitomycin C and radiotherapy alone were 71% and 44%, respectively, a statistically significant difference (P = 0.01). The four-year actuarial local recurrence-free survival rates for patients receiving radiotherapy with mitomycin C and radiotherapy alone were 78% and 63%, respectively (P = 0.11). Differences in four-year distant recurrence-free survival between radiotherapy plus mitomycin C and radiotherapy alone were significantly different at 85% vs. 61% (P = 0.01); this analysis is not adjusted for local failure. On subgroup analysis, stage III-IVA patients had a four-year actuarial disease-free survival of 75% for radiotherapy plus mitomycin C compared with 35% for radiotherapy alone (P = 0.03). There were no treatment- related deaths. Mild hematologic toxicity was seen only in the group treated with mitomycin C. No excess in non-hematologic toxicity has been observed thus far with combined mitomycin C and radiotherapy. In this open phase III trial of mitomycin C as an adjunct to radical radiotherapy for squamous-cell carcinoma of the cervix, there were minimal hematologic effects and no increase in acute radiation reactions. A statistically significant difference in favor of patients receiving mitomycin C is shown for disease-free survival. Thus far, there are trends in favor of those patients receiving mitomycin C for survival and local control. Patients with more advanced stage disease, predominantly stage IIIB, appear to have the most benefit. These preliminary results support the hypothesis that targeting hypoxic cells may lead to a therapeutic enhancement in the radiotherapy of cervix cancer. This trial continues to accrue patients and follow-up data. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 206-223 (2000).

Radiation-induced changes in phosphorus T1 values in human melanoma xenografts studied by 31P-MRS

31P-magnetic resonance spectroscopy (MRS) has been shown to be a promising method for monitoring tumor response to radiation therapy. The purpose of the work reported here was to investigate whether the usefulness of 31P-MRS might be enhanced by measurement of spin-lattice relaxation times (T1s) in addition to resonance ratios. The work was based on the hypothesis that tumors having a high probability of being controlled locally would show shortened T1s during the treatment course due to reoxygenation and development of necrosis. BEX-t human melanoma xenografts, which show efficient reoxygenation and development of necrosis following single dose irradiation, were used as tumor models. Tumors were treated with single doses of 5.0 or 15.0 Gy and the T1s of the inorganic phosphate and nucleoside triphosphate beta resonances were measured as a function of time after irradiation by using the superfast inversion recovery method. Fractional tumor water content was determined by drying excised tumors at 50 degrees C until a constant weight was reached. The T1s in irradiated tumors were either longer than or not significantly different from those in unirradiated control tumors. The increase in the T1s following irradiation coincided in time with a radiation-induced increase in tumor water content, suggesting a causal relationship. The effects of reoxygenation and development of necrosis on T1s were probably overshadowed by the effects of tumor water content. Consequently, the usefulness of 31P-MRS in monitoring tumor response to radiation therapy might not be significantly enhanced by measurement of T1s.

Correlation of lipid content and composition with liposarcoma histology and grade

BACKGROUND

The determination of sarcoma grade, histologic type, and differentiation is often pathologist dependent and requires considerable expertise.

METHODS

Lipid content and composition was analyzed in ex vivo fat, lipoma, and liposarcoma tissue samples using proton-decoupled 13C nuclear magnetic resonance (13C-NMR) spectroscopy and correlated with the histologic type and grade of liposarcoma.

RESULTS

The well-differentiated liposarcomas were found to have threefold increases in fatty acyl chain content compared with benign lipomas. The fatty acyl chain content of the dedifferentiated and pleomorphic liposarcomas was 1% of that found in lipoma and < 0.2% of that found in well-differentiated liposarcoma. The 2.1- to 2.8-fold increase in the degree of polyunsaturation in the dedifferentiated and pleomorphic liposarcomas compared with well-differentiated liposarcoma could largely be accounted for by the 2.3-fold increase in the percentage of fatty acyl chains of lipid containing linoleic acid. The dedifferentiated and pleomorphic liposarcomas contained both free fatty acids and phospholipids that were not NMR detectable in normal fat, lipoma, and well-differentiated liposarcoma.

CONCLUSION

Ex vivo 13C-NMR spectroscopy may be used to distinguish lipoma from well-differentiated, dedifferentiated, and pleomorphic liposarcoma based on changes in lipid and phospholipid metabolite profiles and may serve as adjunct to conventional light microscopy for the determination of liposarcoma histologic type and thus grade.

Characterization of a phosphonium analog of choline as a probe in 31P NMR studies of phospholipid metabolism

Tumors and transformed cells have been shown by 31P NMR to contain elevated concentrations of two phosphomonoesters, phosphorylcholine and phosphorylethanolamine, involved in phospholipid metabolism. In order to understand the biochemical basis for these phenomena new methods are needed to allow for analysis of the relevant metabolic pathways in intact cells. One such promising tool may be phosphonium-choline, a 31P NMR-visible analog of choline in which the trimethyl-ammonium group of choline has been replaced with a trimethyl-phosphonium moiety. As shown previously [Sim et al. Biochem. J. 154, 303 (1976)], this compound is non-toxic and readily metabolized by cultured cells into phospholipids. In this paper we describe in greater detail some of the chemical and NMR spectroscopic properties of this material. Most significantly we show here that the chemical shift of phosphonium-choline is sensitive to the phosphorylation state of the analog and that the phosphonium nucleus is NMR-visible even after its incorporation into phospholipid. The unique properties of this analog should make it possible to use high-field 31P NMR to follow the flux of phosphonium-choline through the Kennedy pathway in intact perfused cells cultures.

Carcinogens stimulate phosphorylation of ethanolamine derived from increased hydrolysis of phosphatidylethanolamine in C3H/101/2 fibroblasts

Many human tumors contain high concentrations of ethanolamine phosphate (EtnP). An important question is whether increased formation of EtnP is merely the consequence of cell transformation, or is it associated with the process of carcinogenesis. Here we show that in C3H/10T1/2 embryonic fibroblasts, an established cellular model for the study of carcinogenesis, the environmental carcinogens, 7,12-dimethylbenz[a]anthracene (DMBA) and benzo[a]pyrene (B[a]P) (0.1-1 microgram/ml concentration; 24 h treatment), stimulate phosphorylation of ethanolamine derived from increased hydrolysis of phosphatidylethanolamine. The results suggest that increased formation of EtnP is associated with the early stages of carcinogenesis. This observation may have prognostic value.

In vivo 31P MRS of experimental tumours

More than 50% of cancers fail to respond to any individual treatment and tumour follow-up after treatment plays a major role in routine therapy planning and pharmacological research. Today, MRS is the only technological approach providing non-invasive access to tumour biochemistry. Ten years ago, expectations were raised concerning 31P MRS as an exciting and promising technical approach to the study of tumours. However the expectations have not always come to fruition. How close are we now to seeing routine 31P NMR in clinical oncology? This review of the 127 published papers shows spectroscopy results in more than 150 experimental animal tumour models. These tumour/host/treatment systems provide us with a useful basis to evaluate the current state of the art, summarize the basic knowledge presently available, determine the key points underlying the present disappointment of some clinical oncologists and stimulate new basic research. The information collected concerns the discussion of the reliability of experimental models in oncology, the technical improvement of magnetic resonance technology and the monitoring of bioenergetic status, pH regulation and phospholipid metabolism in treated and untreated tumours. Recent advances (two-thirds of the papers have been published in the last 5 years) seem to provide more optimistic perspectives than those generally accepted a few years ago, in the depressing period following early pioneering work.

An assessment of artefacts in localized and non-localized 31P MRS studies of phosphate metabolites and pH in rat tumours

UA hepatomas, GH3 prolactinomas and N-methyl-N-nitrosourea-induced mammary tumours, which were subcutaneously grown in rats, have been studied by 31P MRS using non-localized pulse-acquire, image selected in vivo spectroscopy (ISIS) and one-dimensional chemical shift imaging (1-D CSI) techniques. Comparisons have been made with measurements from acid extracts of these tumour types and surrounding tissues (i.e., muscle and skin). Since muscle containing high concentrations of phosphocreatine (PCr) is often found adjacent to the tumour, we have compared the ratio of the PCr to gamma-NTP peaks in the spectra with the same ratio calculated from the acid extract data, and have used deviations between the two sets of data to assess the discrimination of the MRS localization technique to signals from the tissue surrounding the tumour. Extract data showed an average NTP content of 1.25 mumol/g wet wt for all three tumour types. PCr (at 0.42 mumol/g wet wt), was significant only in the GH3 prolactinoma whereas it was negligible in the other tumour types (< 0.1 mumol/g wet wt). There was good agreement between the ISIS PCr/gamma-NTP ratio and the extract data for all tumours. However, the 1-D CSI data showed an unexpectedly large contamination of the tumour spectrum with PCr signals from the skin which was shown by subsequent phantom experiments to be due to the curved geometry of tumour and skin rather than Fourier bleed. In pH measurements by MRS it was found that biological variability was greater than the effects of artefacts (due to either the chemical shift artefact in the ISIS technique or partial volume effects) in the localization technique. An average pH of 7.2 was observed for all tumours. By initially comparing data from different localization schemes with that from chemical extracts potential sources of error have been highlighted and show that phantom studies alone are not sufficient to fully assess the accuracy of localized MRS data.

Comparative analysis of normal and growth-retarded placentas with phosphorus nuclear magnetic resonance spectroscopy

OBJECTIVE

Phosphorus 31 magnetic resonance spectroscopy studies were carried out on placentas from normal vaginal and elective cesarean deliveries without antenatal complications and from pregnancies complicated by intrauterine growth retardation of unknown cause to determine differences.

STUDY DESIGN

Perchloric acid extraction was performed on frozen tissue, and quantitative analysis was carried out for well-resolved resonances representing adenosine triphosphate, sugar phosphate, inorganic phosphorus, diphosphoglycerate, glycerophosphorylethanolamine, and glycerophosphorylcholine.

RESULTS

Adenosine triphosphate levels were highest in the growth-retarded group. There were significantly higher levels of sugar phosphate, diphosphoglycerate, and glycerophosphorylcholine in the placentas of the growth-retarded pregnancies compared with those from normal placentas.

CONCLUSION

These differences may represent a response to hypoxia and an increase in the amount of blood in the placenta. The results demonstrate the utility of nuclear magnetic resonance spectroscopy for studying the pathology of abnormal placentas to gain a better understanding of the pathology and represent early steps toward in vivo spectroscopic studies of the placenta.

Phosphodiesters in saponified extracts of human breast and colon tumors using 31P magnetic resonance spectroscopy

Saponified phospholipid extracts of malignant and normal human breast and colon surgical tissue specimens (n = 45) generate characteristic phosphodiester profiles using 31P magnetic resonance (MR) spectroscopy. The resultant 31P MR spectroscopic profiles of the analyzed tissues are used to differentiate malignant from normal. The appearance of an uncharacterized resonance at 0.29 delta in the malignant tissue spectra (50% of breast and 75% of colon specimens) is the most notable qualitative finding. Quantitatively, malignant colon tissues differ from normal colon tissues with depressed levels of phosphatidylserine and elevated levels of glycerol 3-phosphorylglycerol and an index measuring the summation of phospholipid polar head group residues with free hydroxyl groups. Malignant breast tissues have significantly elevated levels of glycerol 3-phosphorylethanolamine and significantly depressed levels of glycerol 3-phosphorylcholine compared to normal breast tissues, reflecting a perturbation in the balance of lipid residues that are the respective breakdown products of phosphatidylethanolamine and phosphatidylcholine. The concentration of the polar head group residues is compared to 31P MR spectroscopic profiles of colon and breast tissue phospholipids, in order to demonstrate the quantitative nature of the technique employed.

The progression of spermatogenesis in the developing rat testis followed by 31P MR spectroscopy

To evaluate the use of human testicular 31P MR spectroscopy as a diagnostic tool to differentiate between several stages of male infertility, we have studied the testicular levels of several phosphorus containing compounds in the rat in relation to the condition of spermatogenesis and the cell types present in the seminiferous tubules of the testis. During testicular maturation several characteristic changes occur in the 31P MR spectrum of the testis of male Wistar rats. The phosphomonoester/adenosine triphosphate (PM/ATP) ratio shows a decline from 1.61 to 1.02 between the age of 3 and 12 weeks, whereas the phosphodiester (PD)/ATP ratio increases from 0 to 0.72. The testicular pH increases in the same time from 7.06 to 7.32. Testicular MR data obtained after 12 weeks of age onward do not show significant change anymore. The high PM/ATP ratio is associated by a relative high amount of proliferating spermatogonia and spermatocytes during meiosis in the testis, whereas the PD peak seems to be correlated with the release and maintenance of spermatozoa. The MR spectra show a specific fingerprint in all developmental stages of the rat testis as a result of the different cell types in the testis.

Evaluation of BA1112 rhabdomyosarcoma oxygenation with microelectrodes, optical spectrophotometry, radiosensitivity, and magnetic resonance spectroscopy

We studied tumor tissue oxygenation in the BA1112 rhabdomyosarcoma using micro-electrode pO2 measurements, optical spectrophotometry, analyses of cell survival after irradiation, and 31P magnetic resonance spectroscopy (MRS). Studies were carried out in WAG/Rij/Y rats breathing normoxic, hypoxic, and hyperoxic gas mixtures with and without iv administration of perfluorochemical. Significant changes in tissue oxygenation and metabolic status were found when pO2 values, optical measurements of hemoglobin saturation and cytochrome a, a3 reduction-oxidation, radiation cell survival determinations, and MRS measurements of phosphometabolite ratios were obtained in rats breathing different gas mixtures. Inhalation of 100% O2 caused increases in tumor pO2, hemoglobin saturation, cytochrome a, a3 oxidation, tumor radiosensitivity, and PCr/Pi, NTP/Pi, and PDE/Pi ratios. Such changes were augmented by pretreatment with iv perfluorochemicals. Inhalation of hypoxic gas mixtures resulted in reductions in the above parameters. These results indicate that tissue oxygenation can be manipulated reproducibly in the BA1112 rhabdomyosarcoma and suggest that 31P MRS can be used to monitor changes in tumor oxygenation in this model system.

Follow-up by 31P NMR spectroscopy of the energy metabolism of malignant tumor in rats during treatment

The energy metabolism of tumors in rats was investigated by in vivo 31P-NMR spectroscopy. The effects of radiotherapy, chemotherapy or radiotherapy combined with 5-fluorouracil (5-FU) chemotherapy were evaluated by observing the changes of these spectra in chemically induced subcutaneous fibrosarcoma in rats. Two milligrams of DMBA in solution in olive oil were administered subcutaneously in the flank of 20 Wistar rats and 17 fibrosarcoma occurred. 31P NMR spectra were recorded with a Brüker Medspec 30/47 spectrometer using a surface coil positioned over the tumor. We did not observe significant changes in the spectra during tumor growth. Radiotherapy and 5-FU chemotherapy alone did not induce major changes in the 31P spectra. But the situation was completely different for animals receiving the therapeutic combination. A clear increase in the ratio of inorganic phosphate to total phosphorus signal was observed 48 h after the first irradiation session. The pH shifted concurrently to the acidic range. No effect on tumor regression was observed in the rats from the chemotherapy group, while regression was less than 50% in rats treated by irradiation only, and at least 80% in the combined group.

In vivo phosphorus 31 magnetic resonance spectroscopy of human uveal melanomas and other intraocular tumors

We studied the feasibility of using the surface coil probe technique for the noninvasive in vivo study of ocular tumors by phosphorus 31 magnetic resonance spectroscopy. The characteristic organophosphate metabolites of suspected uveal melanomas before proton beam irradiation were determined qualitatively by phosphorus 31 magnetic resonance spectroscopy in vivo using a three-turn surface coil. Spectra of choroidal hemangioma, osteoma, and metastasis were also obtained in vivo and compared with those of uveal melanomas. Analysis of spectra performed at 1.5 T showed significant peaks of phosphomonoesters, inorganic phosphate, phosphodiesters, phosphocreatine, and adenosine 5'-triphosphates. The unusually high concentration of phosphodiesters may be considered as a marker for uveal melanomas and other choroidal tumors. By analyzing the ratio of phosphocreatine to phosphodiesters spectral area values, we interpreted qualitatively spectra of intraocular tumors to differentiate malignant tumors from benign lesions. Nevertheless, the main limitation of interpreting the spectra was their contamination by signals from surrounding tissues.

Phosphorus 31 magnetic resonance spectroscopy of human placenta and quantitation with perchloric acid extracts

Phosphorus 31 magnetic resonance spectroscopic studies of fresh placental tissue are reported that indicate resonances for adenosine triphosphate, inorganic phosphate, sugar phosphates-phosphomonoesters, and phosphodiesters. Perchloric acid extract methods were used to further characterize and quantitate phosphorous metabolites in term human placentas by phosphorus 31 magnetic resonance spectroscopy. The perchloric acid extracts give enhanced resolution of phosphorus signals and allow identification of other phosphorus metabolites including small amounts of phosphocreatine. Emphasis was placed on quantitating adenosine triphosphate levels in the acid extracts with the use of the external reference standard hexachlorocyclotriphosphazene in a coaxial capillary system. Adenosine triphosphate levels measured in this way ranged from 0.404 to 0.709 mumol per gram wet weight. Comparison with an internal standard method with phosphocreatine is also reported. Contribution to the measured high-energy phosphate pool from blood in the highly vascularized tissue was found to be relatively large and could range from 30% to 50% of the total adenosine triphosphate measured.

Influence of hormono- and/or chemotherapy on the MXT mouse mammary tumor as monitored by 31P MRS

We describe the early in vivo modifications that occurred in the MXT mouse hormone sensitive mammary tumor following various treatments which were monitored by 31P NMR spectroscopy. The MXT mouse mammary tumor was subjected to clinically relevant low-dose chemotherapy, i.e. seven cycles of 20 mg/kg cyclophosphamide (CPA) with or without an attempt at estrogenic cell recruitment prior to the CPA treatment. NMR measurements were begun at the end of the CPA treatment in order to evaluate the remaining 'long-term' chemotherapy-induced modifications within the MXT tumors. Statistical analyses performed on the 31P NMR parameters revealed that treatment had induced significant effects on bATP/PCr, Pi/PCr and PME/PDE only, with PCr being the most discriminating index. Its presence within MXT tumors was verified by means of an analysis of perchloric extracts. The results indicate a relative decrease of PME/PDE and a better conservation of PCr within the CPA-treated group as compared to the control one. This feature appeared even prior to any macroscopic modifications, as was the case within the group which contained tumors smaller than 120 mm2, and where no significant differences appeared between the mean sizes of the MXT cancers. In contrast, within the G2 group, which contained tumors equal to or larger than 120 mm2, CPA significantly slowed down tumor growth, while the administration of estradiol (E2) prior to CPA treatment antagonized the positive CPA-induced therapeutic effect. In conclusion, the non-invasive follow-up of the chemotherapeutic treatment of a clinically relevant mammary tumor model by 31P NMR spectroscopy backed up by statistical analyses revealed metabolic changes that appeared well before any modifications in histopathology or growth.

The assessment of treatment response in non-Hodgkin's lymphoma by image guided 31P magnetic resonance spectroscopy

Serial image guided 31P magnetic resonance spectroscopy (MRS) studies were performed in eight patients with non-Hodgkin's lymphoma to determine the changes in phosphorus metabolites that occur in vivo in response to chemotherapy. Pre-treatment spectral characteristics were different in high and low grade lymphoma. A larger inorganic phosphate (Pi) peak was seen in high grade NHL relative to phosphomonoesters (PME) or beta adenosine triphosphate (beta ATP), producing significant differences in the PME/Pi and Pi/beta ATP metabolite ratios, and probably reflecting a larger hypoxic cell fraction within the high grade lymphomas. Consistent metabolite changes were seen with treatment, and before reductions in tumour bulk had occurred. Alterations in tumour energetics with changes in Pi and beta ATP, and increases in phospholipid turnover reflected as an increase in the phosphodiester (PDE) resonance were detected. Changes were seen between days 10 and 27 in low grade lymphoma treated with oral alkylating therapy and between days 1 and 5 in lymphoma treated with intensive combination chemotherapy. Increases in the PDE/beta ATP metabolite ratio may be an early indicator of response to chemotherapy in human tumours. These studies illustrate the feasibility and clinical potential of image guided 31P MRS as a means of assessing response to therapy.

In vivo 31P-NMR spectroscopy of murine tumours before and after localized hyperthermia

In vivo 31P-NMR spectroscopy was used to monitor the energy metabolism, apparent intracellular pH (pHNMR), and phospholipid turnover in subcutaneous fibrosarcomas (FSall) and mammary carcinomas (MCaIV) treated with hyperthermia (HT). Treatment consisted of elevation of tumour temperature to 43.5 degrees C for 15, 30 or 60 min (FSall) and 30 min (MCaIV). Experiments were performed on conscious mice with biologically relevant tumour sizes. Using water bath immersion, this study focused on acute heat-induced metabolic changes (up to 7 h post-HT). 31P-NMR spectra of both murine tumours were characterized by relatively high pretreatment levels of PME, Pi and NTP, and lower levels of PDE, PCr and DPDE. Following hyperthermia, NTP and PCr levels, as well as pHNMR, decreased in both tumour lines. This drop was accompanied by a prompt and dramatic increase in Pi. After heating for 15 min, the limited spectral changes observed for the high-energy phosphates and the marginal decline in pHNMR were nullified within 7 h, whereas Pi remained significantly elevated. With the exception of PME/NTP and PME/PDE, all relevant metabolic ratios (PCr/Pi, NTP/Pi, PME/Pi) decreased after heating and did not resolve thereafter. Upon longer heat exposure times the high-energy phosphates, pHNMR, NTP/Pi, PCr/Pi, and PME/Pi all decreased in a dose-dependent manner and remained at the respective lower levels. The PME/PDE ratio was increased after 43.5 degrees C/15 min whereas at longer heating times this ratio did not change. At comparable heat doses MCaIV tumours seem to exhibit changes similar to FSall tumours.

The use of magnetic resonance imaging and spectroscopy in the assessment of patients with head and neck and other superficial human malignancies

The proper demarcation of diseased tissue is important for radiation therapy planning and treatment. The volume to be irradiated is usually identified on radiographs or on x-ray computed tomography (CT) sections. Magnetic resonance (MR)-derived images of the proton T2 relaxation times in small pixel elements, typically 0.5 mm2 or less, provide significantly sharper differentiation between normal and diseased tissue. The T2 values in tissue depend on the tissue composition, histologic condition, and physiologic environment within the tumor. Furthermore, for many tumors the histogram of T2 values has a clear biphasic distribution suggesting that T2 maps may be useful for the identification of necrotic or hypoxic regions within tumors. The distribution of T2 values within the tumor bed shows the general pattern that the T2 values are elevated with a range greater than that seen in normal muscle. Elevated T2 values are not by themselves diagnostic of malignancy; however, they demonstrate the heterogeneity of the microenvironment present within a tumor. The spatial distribution of T2 values is being explored as a method for computer assistance in the delineation of the target volume for treatment planning. In addition, MR P-31 spectroscopic examinations were performed on 30 patients with squamous cell carcinomas of the head and neck. Although hampered by muscle contamination in some P-31 spectra obtained with surface coil profile localization techniques, significant trends can still be appreciated in our data. These trends include the following: (1) the P-31 spectra from malignant tissue have well-resolved spectral lines in the upfield region that correspond to Pi, phosphomonoester (PME), and phosphodiester (PDE) not usually seen in normal muscle; (2) the PDE/B-ATP and PME/B-ATP ratios are greater than unity in all cases; and (3) most of the tumors have higher PME peaks than PDE peaks. The P-31 spectra from patients treated with ionizing radiation changed during and after therapy. Some of the changes could be associated with alteration of the tumor metabolic activity or synthesis and breakdown of lipoproteins. These studies suggest that magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) studies may be useful for both radiotherapy treatment planning and the noninvasive monitoring of patients both before and during treatment.

Magnetic resonance imaging and spectroscopy of intraocular tumors

Proton magnetic resonance imaging (1H MRI) has emerged as a clinically useful tool for the diagnosis of intraocular tumors. During the last four years 1H MRI characteristics, including spin-lattice relaxation times (T1) and spin-spin relaxation times (T2), have been established for several types of tumors. The introduction of surface coils to the imaging process has significantly improved the quality of intraocular MR images, leading some clinicians to suggest that 1H MR images are preferable to CT scans. Another MRI technique, in which sodium-23 (23Na) is imaged rather than protons, is now under development as tool for intraocular diagnosis. The potential of 23Na MRI depends upon the high concentration and "visibility" of sodium in the vitreous body, and upon the apparent differences in sodium behavior in normal cells vs. tumor cells. The metabolism of normal ocular tissues and intraocular tumors may be probed noninvasively with phosphorus-31 MR spectroscopy (31P MRS). Much progress has been made during the last few years in understanding the appearance of 31P MR spectra of many types of healthy and diseased cells and tissues. Clinical application of this technique to the diagnosis and monitoring of intraocular tumors following conservative treatment will be dependent upon the development of spectroscopy techniques that collect information from the volume of interest (tumor) only.

Phosphorus-31 nuclear magnetic resonance spectroscopy of human retinoblastoma cells: correlation with metabolic indices

The 31P nuclear magnetic resonance spectrum of cultured human Y-79 retinoblastoma cells was obtained at 121 MHz on intact cells trapped in agarose threads. The spectrum was dominated by monoester peaks, which varied in relative concentration from preparation to preparation. Resonances from phosphocreatine, phosphodiesters and diphosphodiesters also exhibited variability relative to ATP. The main monoester was identified as phosphorylcholine by 31P-NMR of perchloric acid extracts. It was determined that the changes in monoester concentration correlated with feeding pattern. Phosphorus spectra of cells 1, 2 and 3 days post feeding showed a 40% decrease in the relative concentration of phosphorylcholine concentration over the 3 day period. Phosphocreatine, phosphodiesters and diphosphodiesters increased relative to ATP during the same period. Growth curve experiments and oxygen consumption measurements indicated that the decrease in phosphorylcholine correlated with a decrease in cellular growth and oxygen consumption. We conclude that monoester concentration may be a useful indicator of nutritional status in these cells and possibly in intact tumors.

Preliminary results on phosphorus-31 nuclear magnetic resonance evaluation of human uveal melanoma in enucleated eyes

Clinical evaluation of uveal melanomas by nuclear magnetic resonance (NMR) techniques depends on ascertaining how these tumors characteristically appear in NMR images and spectra. The authors have determined NMR characteristics of suspected uveal melanomas by phosphorus-31 (31P) NMR spectroscopy of freshly enucleated human eyes. Nuclear magnetic resonance examination was performed at 8.45 Tesla within 90 minutes after enucleation. Enucleated eyes were maintained at 4 degrees C in tissue culture medium during the 30 minutes required for transport. Nuclear magnetic resonance spectra were obtained within 10 minutes, a clinically acceptable time, using a two-turn 31P surface coil. Spectral parameters included 10-kHz spectral width, 1024 data points, and 0.5-second recycle delay. Phosphorus-31 NMR spectroscopy allowed differentiation of choroidal melanomas from normal ocular structures. Differentiating features include significant peaks in tumor spectra due to the phosphodiesters glycerol 3-phosphoryl ethanolamine (GPE) and glycerol 3-phosphorylcholine (GPC), and the phosphomonoesters phosphorylethanolamine (PE) and phosphorylcholine (PC). These preliminary data are encouraging and suggest that clinical trials at the lower magnetic field strengths available in NMR imaging systems seem feasible and warrant investigation.

Response of a non-Hodgkin lymphoma to 60Co therapy monitored by 31P MRS in situ

High quality 31P MR spectra (signal to noise ratio (S/N) approximately 18, 15 min acquisition for each spectrum) were consistently obtained with surface coils over a period of 6-week RT. Both transient and steady state alterations in metabolites in response to RT were found in this case. The transient changes occurred during the first 3 hr immediately after the 3rd fractionated RT, these changes include the transient elevation of the PCr resonance, a decrease in PDE and an increase in intracellular pH. The monitoring showed that the metabolites approached steady state approximately 2 hr after the fractionated radiation intervention, suggesting that in vivo MRS can be useful for studying the dynamics of tumor response to RT such as repair of potential lethal damage, growth delay, and reoxygenation etc. The steady-state MR spectra showed the net response to each intervention and can clinically be useful for predicting and measuring the result of the fractionated RT. In this case study, the PDE peak which contains the phospholipid metabolites GPC and GPE, is the most sensitive resonance in response to RT. After the 3rd RT, prior to tumor size reduction, the PDE to ATP ratio decreased 33% and intracellular pH increased to 7.34 +/- 0.05 from 7.27 +/- 0.05. In the subsequent RT interventions, both the tumor size and PDE/ATP ratio continually decreased whereas the pH values remained alkaline and fluctuated around 7.34 to 7.65. The data suggest that the phospholipid metabolite PDE may signal important alterations in membrane metabolism that eventually lead to cell death.

Anti-tumor effects of interferon in mice injected with interferon-sensitive and interferon-resistant Friend leukemia cells. V. Comparisons with the action of tumor necrosis factor

A number of similarities and dissimilarities in the anti-tumor effects of TNF and interferon alpha/beta have been observed in DBA/2 mice injected with Friend erythroleukemia cells (FLC). Mouse TNF exerted marked anti-tumor effects in mice injected either s.c. or i.p. with FLC lines 3C18 or 3 gamma R8 resistant in vitro to the cytotoxic effects of TNF. Likewise, mouse interferon alpha/beta had anti-tumor activity in mice injected with these FLC, resistant to the action of interferon alpha/beta or gamma in vitro. The results of histopathologic examination and 31P nuclear magnetic resonance analyses of 3C18 FLC s.c. tumors injected with TNF resembled the results previously obtained for 3C18 FLC tumors injected with interferon alpha/beta, although the effects of TNF occurred more rapidly. Injection of mice with antibody to mouse interferon alpha/beta or gamma did not abrogate the anti-tumor effects of TNF in mice injected i.p. with FLC. Our results suggest that in this experimental system the anti-tumor effects of TNF, like interferon alpha/beta, do not result from a direct effect on the tumor cells themselves but are host-mediated.