A comparison of in vivo and in vitro 31P NMR spectra from human breast tumours: variations in phospholipid metabolism

An in vivo 31P NMR spectrum was obtained from each of four human breast tumours. The phosphomonoester and phosphodiester region of each spectrum consisted of a broad peak. Chemical extracts from samples of each of the tumours obtained at resection were examined on a high field strength NMR system. The phosphomonoester region in the spectrum from each extract resolved into three peaks consisting of phosphocholine, phosphoethanolamine and a nucleoside monophosphate. The phosphodiester region resolved into two components, glycerophosphorylcholine and glycerophosphorylethanolamine. Comparing the in vivo and in vitro data from each tumour showed that the contribution of phosphodiester was much lower in the in vitro spectra. We believe this to be a consequence of phospholipid, which would not appear in the aqueous extract, contributing to the phosphodiester peak in vivo.     

Measurements of in vivo 31P nuclear magnetic resonance spectra in neuroectodermal tumors for the evaluation of the effects of chemotherapy

The effects of chemotherapy on living tumor tissue in hamsters and rats were investigated by measuring the 31P nuclear magnetic resonance spectra using topical magnetic resonance. Human neuroblastoma, human glioblastoma, and rat glioma tumor cells were inoculated s.c. in the lumbar region of the animals. After the diameter of the tumors increased to 1.5 cm, in vivo 31P nuclear magnetic resonance spectra were measured selectively in the tumors with a TMR-32 spectrometer. Adenosine triphosphate, inorganic phosphate (Pi), phosphodiester, and phosphomonoester peaks were observed. The phosphocreatine peak was hardly detectable, adenosine triphosphate and phosphomonoester peaks were high, and tissue pH, calculated from the chemical shift of Pi, declined. Regardless of the tumor origin or the histological type, the spectral pattern of each neuroectodermal tumor was found to be essentially the same. After i.v. injection of a large dose of a chemotherapeutic agent, adenosine triphosphate peaks decreased and Pi increased gradually, resulting in a dominant Pi peak pattern after 6 to 12 hours. However, during the same period, there were no observable changes in the spectra of normal organs. These findings indicated that the drugs have a selective and direct action on the energy metabolism of tumor cells. With lower drug doses, no remarkable changes were seen in the spectrum. Measurement of in vivo 31P nuclear magnetic resonance spectra is valuable not only to investigate the energy metabolism in tumor tissue but also to evaluate the effects of chemotherapy.     

In vivo 14N nuclear magnetic resonance spectroscopy of tumors: detection of ammonium and trimethylamine metabolites in the murine radiation induced fibrosarcoma 1

The in vivo 14N nuclear magnetic resonance spectra of s.c. implanted murine radiation induced fibrosarcomas (RIF-1) display narrow resonances assignable to betaine and other trimethylamines and broad resonances due to amino acids and peptides. In 19 of the 41 tumors studied a distinct resonance from the ammonium ion is detectable. The accumulation of ammonium in the tumor to nuclear magnetic resonance detectable levels may result from glutaminolysis (a possible pathway for energy production in the tumor), from the degradation of peptides and proteins, or from the deamination of adenine nucleotides. Estimates of the tissue ammonium concentration were obtained from the in vivo tumor spectrum and the spectrum of the nonlabile trimethylamines in the perchloric acid extract. In the extract, the 14N resonances of betaine, carnitine, choline, phosphorylcholine, and glycerophosphorylcholine were resolved, and a relatively high level of tissue urea was observed. Spin-lattice relaxation times were obtained for the 14N nucleus of each of these metabolites in phosphate buffer.     

An ex vivo model for the study of tumor metabolism by nuclear magnetic resonance: characterization of the phosphorus-31 spectrum of the isolated perfused Morris hepatoma 7777

We have developed an isolated perfused tumor model to study the metabolism of solid tumors by nuclear magnetic resonance spectroscopy. Morris hepatomas (7777) were implanted in the inguinal region of Buffalo rats, such that they developed an isolated blood supply. These tumors were perfused with a RBC perfusate, removed from the animal, and studied by 31P nuclear magnetic resonance spectroscopy. ATP levels, as determined from the spectra, were stable for as long as the tumors were maintained in the magnet (7 h) only if the perfusate contained inosine, adenosine, and insulin. The adenosine and inosine were also required for recovery from ischemia. Under these conditions, ischemia did not result in a change in tumor pH. The gamma nucleoside triphosphate resonance was significantly larger than the beta nucleoside triphosphate resonance in spectra of some of the perfused tumors, suggesting that ADP above about 300 nmol/g wet weight was not complexed in these tumors. The adenylate levels determined from extracts, O2 consumption, histology, and 31P nuclear magnetic resonance spectra of extracts of perfused tumors and tumors in situ were all similar, indicating the perfused tumor is a reasonable model of the tumor in vivo.     

Response of radiation-induced fibrosarcoma-1 in mice to cyclophosphamide monitored by in vivo 31P nuclear magnetic resonance spectroscopy

In vivo 31P nuclear magnetic resonance spectroscopy has been used to examine the RIF-1 fibrosarcoma in mice during untreated growth and following chemotherapy with cyclophosphamide. Levels of inorganic phosphate increase relative to phosphocreatine or nucleoside triphosphates during early untreated growth. After the tumor reaches a volume of approximately 1 g, no further decrease in energy level is observed. Following treatment with cyclophosphamide, tumor phosphorus metabolite ratios and pH are significantly altered, compared to untreated age-matched controls. During the growth delay period following chemotherapy there is a significant reduction in the ratio of inorganic phosphate to other phosphate metabolites, compared to age-matched controls. In addition, a more alkaline pH is observed in the tumors of treated animals. When the growth delay period ends, nuclear magnetic resonance spectra return to pretreatment patterns. The magnitude of the differences in 31P nuclear magnetic resonance spectral parameters between treated animals and untreated controls is dose dependent. However, doses of cyclophosphamide above 200 mg/kg do not result in earlier spectroscopic alterations, nor in larger effects by Day 3 after treatment, even though clonogenic cell killing and growth delay are greater at these higher doses.     

Phosphate metabolites and steroid hormone receptors of benign and malignant breast tumors. A Nuclear Magnetic Resonance study

Phosphorous 31 (31P) nuclear magnetic resonance (NMR) spectra were recorded from perchloric acid extracts of benign and malignant breast tumors. The spectra were correlated with the histopathologic diagnosis and the steroid receptor status of the tumor. Higher relative content of the lipid-derived metabolite glycerolphosphoethanolamine (GPE), the high-energy nucleoside phosphates (nucleoside-diphosphate [NDP], nucleoside-triphosphate [NTP]), and sugar esters of uridine diphosphate (UDPS) appeared in the carcinomas. Malignant tumors also showed a lower ratio of phosphoethanolamine to phosphocholine (PE/PC) than benign conditions. Lower content of the lipid-derived metabolite glycerolphosphocholine (GPC) and high content of the high-energy compound phosphocreatine (PCr) were associated with malignant tumors having high content of estrogen receptors (ER). High PCr content was also associated in the carcinomas with high progesterone receptors (PgR) content. In the benign tumors NDP and NTP were higher in tumors with high PgR content. The authors suggest that 31P magnetic resonance spectroscopy (MRS) of the breast can provide additional variables to diagnose malignancy, and when combined with magnetic resonance imaging (MRI), invasive procedures may be avoided. It also seems that levels of PCr and GPC obtained from the spectra can serve as markers to hormonal receptor status of breast carcinomas, and may be used in addition to the ER and PgR content to improve prediction of the response to hormonal therapy. Additional development requires in situ MRI and MRS combined studies.     

Noninvasive magnetic resonance spectroscopic pharmacodynamic markers of the choline kinase inhibitor MN58b in human carcinoma models

MN58b is a novel anticancer drug that inhibits choline kinase, resulting in inhibition of phosphocholine synthesis. The aim of this work was to develop a noninvasive and robust pharmacodynamic biomarker for target inhibition and, potentially, tumor response following MN58b treatment. Human HT29 (colon) and MDA-MB-231 (breast) carcinoma cells were examined by proton (1H) and phosphorus (31P) magnetic resonance spectroscopy (MRS) before and after treatment with MN58b both in culture and in xenografts. An in vitro time course study of MN58b treatment was also carried out in MDA-MB-231 cells. In addition, enzymatic assays of choline kinase activity in cells were done. A decrease in phosphocholine and total choline levels (P < 0.05) was observed in vitro in both cell lines after MN58b treatment, whereas the inactive analogue ACG20b had no effect. In MDA-MB-231 cells, phosphocholine fell significantly as early as 4 hours following MN58b treatment, whereas a drop in cell number was observed at 48 hours. Significant correlation was also found between phosphocholine levels (measured by MRS) and choline kinase activities (r2 = 0.95, P = 0.0008) following MN58b treatment. Phosphomonoesters also decreased significantly (P < 0.05) in both HT29 and MDA-MB-231 xenografts with no significant changes in controls. 31P-MRS and 1H-MRS of tumor extracts showed a significant decrease in phosphocholine (P < or = 0.05). Inhibition of choline kinase by MN58b resulted in altered phospholipid metabolism both in cultured tumor cells and in vivo. Phosphocholine levels were found to correlate with choline kinase activities. The decrease in phosphocholine, total choline, and phosphomonoesters may have potential as noninvasive pharmacodynamic biomarkers for determining tumor response following treatment with choline kinase inhibitors.     

Metalloporphyrin enhancement of magnetic resonance imaging of human tumor xenografts in nude mice

Paramagnetic metalloporphyrins were examined for their in vivo bio-distribution and their ability to enhance nuclear magnetic resonance imaging of human tumor xenografts in nude mice. The metalloporphyrins tested were: manganese tetrasodium-meso-tetra(4-sulfonatophenyl)-porphine (MnTPPS); manganese meso-tetra-4-pyridylporphine; and gadolinium meso-tetra-4-pyridylporphine. All exhibited high molar relaxivities in aqueous solution. In vivo, at a dose of 2 mg/mouse, MnTPPS depressed the longitudinal relaxation time, T1, significantly in the kidney and less in lung and blood. Manganese meso-tetra-4-pyridylporphine depressed T1 in the kidney, lung and liver, while gadolinium meso-tetra-4-pyridylporphine caused large T1 depressions in the blood, liver, brain and tumor, probably due to dissociation of the metalloporphyrin and binding of Gd to plasma or tissue proteins. At a dose of 10 mg/mouse, MnTPPS caused marked T1 depressions of all tissues tested within 5 min of inoculation, but 48-72 h later, T1 values of normal tissues had returned to near normal, while those of the tumors remained significantly depressed. MnTPPS was able to significantly enhance the intensity of nuclear magnetic resonance images of MX-1 and ZR-75 human breast tumors and CX-1 and LS174T human colon tumor xenografts in nude mice. The results demonstrate that paramagnetic metalloporphyrins, because of their high relaxivities and retention in tumors, have the potential for use as tumor-selective contrast agents for nuclear magnetic resonance imaging.     

Effects of oxygen on the metabolism of murine tumors using in vivo phosphorus-31 NMR

The effect of 100% inspired oxygen on in vivo tumor metabolism was examined using phosphorus-31 (31P) NMR spectroscopy. Isotransplants of two murine tumor histologies, designated MCaIV (C3H mammary adenocarcinoma) and FSaII (C3H fibrosarcoma), were used in syngeneic mice. Tumor volumes ranged from 30 to 1,800 mm3. Both tumor histologies are known to have a high hypoxic cell fraction when tumor volumes exceed 250 mm3. 31P nuclear magnetic resonance (NMR) spectra were obtained at 145.587 MHz, and the signal was detected using a 1.4 cm diameter, single loop coil designed to localize the signal from only the tumor. Spectral parameters for optimal signal-to-noise ratio (SNR) included a 60 degrees pulse and a 2-second recycle delay. Tumors were implanted in the hindfoot dorsum to assure that all detected mobile phosphates were of tumor origin. Phosphocreatine/inorganic phosphate (PCr/Pi) ratios of large tumors (greater than 250 mm3) were reduced compared with small tumors (less than 250 mm3) of the same histology. The increased PCr/Pi response to 100% inspired oxygen was greater for large tumors and for tumors with lower baseline PCr/Pi ratios. When host animals were given 10% oxygen for respiration, there was an increase in Pi and a decrease in both PCr and ATP. The response to 10% oxygen was observed in both large and small tumors of both tumor histologies studied. Resting skeletal muscle exhibited no alteration in the NMR spectrum during either 100 or 10% oxygen breathing. We conclude that the fractional increase in PCr/Pi ratio that occurs after 100% oxygen breathing is a sensitive, noninvasive method of detecting tumor hypoxia.     

Response-specific adriamycin sensitivity markers provided by in vivo 31P nuclear magnetic resonance spectroscopy in murine mammary adenocarcinomas

The in vivo phosphorus-31 nuclear magnetic resonance (NMR) spectra of Adriamycin (ADR)-sensitive murine mammary adenocarcinomas (17/A) and an ADR-resistant subline of this tumor which has been isolated in vivo (17/A/ADR) were compared both before and after i.v. administration of 12 mg/kg ADR. Significant differences between ADR-sensitive and -resistant tumors for the changes observed 1 day after treatment (prior to significant decreases in tumor size) included: the pH increased to greater than 7.3 in response to treatment (or pH remained elevated) in ADR-sensitive tumors only; the inorganic phosphate to nucleoside triphosphates peak height ratio decreased to less than 1 in response to treatment only in ADR-sensitive tumors; glycerophosphocholine to nucleoside triphosphates peak height ratio decreased in response to treatment in ADR-sensitive tumors only; and the phosphocholine to nucleoside triphosphates peak height ratio decreased in response to treatment in ADR-sensitive tumors only. These differences are evidence in support of the hypothesis that in vivo 31P-NMR provides response-specific markers of ADR sensitivity. Because 31P-NMR can be applied to humans, these differences may be of prognostic value in the clinical management of human breast cancer if they are present after treatment with lower, nontoxic doses of ADR.     

CXCR1/CXCR2受体拮抗剂——G31P抑制前列腺癌转移的体内外实验研究

目的研究CXCR1/CXCR2受体拮抗剂——G31P对人前列腺癌PC-3细胞的体内外转移的抑制作用。方法采用细胞划痕实验研究G31P对PC-3细胞体外转移的抑制作用。通过建立体内的绿色荧光蛋白(GFP)标志人雄激素非依赖性前列腺癌PC-3细胞的裸鼠原位移植瘤模型,观察G31P对裸鼠前列腺癌原位移植瘤体内转移的影响。结果细胞划痕实验结果显示,G31P 100μg/L处理组作用细胞72小时的迁移率为(50.17±22.43)%(P<0.05,与对照组比较)。与对照组(100μL N.S)比较,G31P处理组(0.5 mg/kg)淋巴结(腰淋巴结、肠系膜淋巴结、远处淋巴结)转移略有减少,但差异无统计学意义;胰腺和肝部转移则明显减少(P<0.05)。免疫组织化学结果显示,与对照组比较,G31P处理组MMP-9(P<0.05)的表达明显减少。结论在体内外实验中G31P均能抑制人雄激素非依赖性前列腺癌PC-3细胞系的转移。     

重组人血管内皮抑素对食管癌细胞生长抑制作用的研究

目的　探讨重组人血管内皮抑素（恩度）对食管癌细胞生长的抑制作用。方法　用ＭＴＴ法检测恩度对食管癌细胞-１０９和人脐静脉内皮细胞（ＨＵＶＥＣ）的增殖抑制作用;建立Ｅｃａ-１０９细胞裸鼠移植瘤模型,观察不同浓度恩度对移植瘤生长的影响;免疫组织化学检测瘤组织微血管密度（ＭＶＤ）;ＥＬＩＳＡ方法检测荷瘤动物血清ＶＥＧＦ的浓度。结果　与空白对照组比较,恩度能抑制Ｅｃａ-１０９和ＨＵＶＥＣ细胞的增殖（Ｐ均＜０.０5）,并有效抑制食管癌移植瘤的生长（Ｐ＜０.０５）,检测荷瘤组织中ＭＶＤ计数较空白对照组明显降低（Ｐ＜０.０５）,荷瘤动物血清ＶＥＧＦ浓度也明显低于空白对照组（Ｐ＜０.０５）。结论 恩度能有效抑制食管癌细胞及移植瘤的生长。     

Correlations between in vivo tumor weight,oxygen pressure, 31P NMR spectroscopy,hypoxic microenvironment marking by beta-D-iodinated azomycin galactopyranoside (beta-D-IAZGP), and radiation sensitivity

PURPOSE: The purpose of this study is to evaluate the amount of hypoxic fraction in a rodent tumor by means of polarographic oxygen electrode, phosphorus-31 magnetic resonance spectroscopy (31P-MRS), and a newly synthesized hypoxic marker, beta-D-iodinated azomycin galactopyranoside (beta-D-IAZGP). We also investigated the radiosensitivity for tumors of different weights. METHODS AND MATERIALS: Murine mammary carcinoma cells, FM3A, were subcutaneously implanted into the back of 5-week-old male C3H/He mice. beta-D-IAZGP radiolabeled with 123I or with 125I was injected intravenously into tumor-bearing mice, and marker distribution was measured by nuclear medicine procedures. Radiosensitivity of the tumor was measured by the in vivo/in vitro clonogenic assay. Tumor oxygenation status was also measured directly by polarographic oxygen electrodes and indirectly estimated from 31P-MR spectra. RESULTS: Higher accumulation of 123I-beta-D-IAZGP was observed in the tumors than in normal tissues at 24 h after administration. As to biodistribution of 125I-beta-D-IAZGP, the tumor/blood ratio varied widely, but correlated significantly with tumor weight. Mean oxygen pressure (pO2) values and ratios of nucleoside triphosphate beta to inorganic phosphate (beta-ATP/Pi) and of phosphocreatine to inorganic phosphate (PCr/Pi) decreased significantly with the increase in tumor volume. As tumor volume increased, the surviving fraction of cells from tumors irradiated in vivo increased significantly. CONCLUSIONS: The increase in tumor volume was significantly correlated with a reduction in mean pO2, a decrease in the ratios of beta-ATP/Pi or PCr/Pi, an increase in uptake of beta-D-IAZGP, and an increase in radioresistance. Because the uptake of beta-D-IAZGP can be measured noninvasively by nuclear medicine techniques, it could be clinically useful for monitoring hypoxia in human tumors.     

In vivo 19F magnetic resonance spectroscopy and chemical shift imaging of tri-fluoro-nitroimidazole as a potential hypoxia reporter in solid tumors.

PURPOSE: 2-Nitro-alpha-[(2,2,2-trifluoroethoxy)methyl]-imidazole-1-ethanol (TF-MISO) was investigated as a potential noninvasive marker of tissue oxygen levels in tumors using (19)F magnetic resonance spectroscopy (MRS) and (19)F chemical shift imaging. EXPERIMENTAL DESIGNS: In vitro data were obtained using high-performance liquid chromatography on tumor cells incubated under varying oxygen conditions to determine the oxygen-binding characteristics. In vivo data were obtained using a well-characterized hypoxic murine breast tumor (MCa), in addition to studies on a rat prostate tumor model (R3327-AT) implanted in nude mice. Detection of intratumor (19)F signal from TF-MISO was done using MRS for up to 10 h following a 75 mg/kg i.v. injection. Localized distribution of the compound in the implanted MCa tumor has been imaged using slice-selective two-dimensional chemical shift imaging 6 h after injection. RESULTS: The in vitro results showed that TF-MISO preferentially accumulates in cells incubated under anoxic conditions. The in vivo (19)F MR spectral features (line width and chemical shift) were recorded as a function of time after injection, and the results indicate that the fluorine atoms are indeed sensitive to changes in the local environment while still providing a detectable MR signal. Ex vivo spectra were collected and established the visibility of the (19)F signal under conditions of maximum hypoxia. Late time point (>6 h) tumor tissue concentrations, as obtained from (19)F MRS, suggest that TF-MISO is reduced and retained in hypoxic tumor. The feasibility of obtaining TF-MISO tumor distribution maps in a reasonable time frame was established. CONCLUSIONS: Based on the results presented herein, it is suggested that TF-MISO has the potential to be a valid magnetic resonance hypoxia imaging reporter for both preclinical hypoxia studies and hypoxia-directed clinical therapy.     

Melanoma tumors acquire a new phospholipid metabolism phenotype under cystemustine as revealed by high-resolution magic angle spinning proton nuclear magnetic resonance spectroscopy of intact tumor samples

N'-[2-chloroethyl]-N[2-(methylsulfonyl) ethyl]-N'-nitrosourea (cystemustine),a chloroethylnitrosourea antineoplastic drug, provokes cellular proliferation inhibition and redifferentiation, but there was no cell death in B16 melanoma tumors. Because the phospholipid (Plp) metabolism is tightly involved in tumor growth regulation and tumor cell survival, we tested the hypothesis that melanoma tumors undergo adaptive Plp metabolism changes to survive treatment. Measurements of Plp derivatives were performed using a novel proton nuclear magnetic resonance Spectroscopy application using magic angle spinning on intact tumor tissue samples. Phosphatidylcholine levels were obtained from one-dimensional spectra, and relative levels of choline- and ethanolamine-containing compounds were derived from two-dimensional spectra (total correlation spectroscopy sequence). Two major findings emerged from this study: (a) during tumor growth inhibition, there was a transient accumulation of choline, glycerophosphocholine, and glycerophosphoethanolamine and a sustained increase in phosphocholine and phosphoethanolamine, whereas phosphatidylcholine levels remained unchanged; and (b) during tumor growth recovery, only phosphocholine and phosphoethanolamine remained elevated. Therefore, cystemustine-treated B16 melanoma tumors acquire a new Plp metabolism phenotype, a mechanism that could participate in tumor cell redifferentiation and/or survival.     

Monoclonal antibody A7-superparamagnetic iron oxide as contrast agent of MR imaging of rectal carcinoma

Superparamagnetic iron oxide (SPIO)-based colloid has been used clinically as a tissue-specific magnetic resonance contrast agent. We coupled monoclonal antibody A7 (Mab A7), which reacts specifically with human colorectal carcinoma, to Ferumoxides (SPIO) and examined the accumulation of this conjugate in xenografted tumours in nude mice. We examined in vitro immunoreactivity of Mab A7 coupled to Ferumoxides and its in vivo distribution in nude mice with human colorectal carcinoma. Magnetic resonance imaging of tumour-bearing nude mice was performed 72 h after injection of A7-Ferumoxides. A7-Ferumoxides retained binding activities that were nearly identical to intact Mab A7. More of the radiolabelled A7-Ferumoxides accumulated in the tumour than normal mouse IgG-Ferumoxides from 12 h onwards after injection (P<0.05). Both A7-Ferumoxides and normal mouse IgG-Ferumoxides disappeared from blood linearly over time. The accumulation levels in normal tissue decreased linearly over time but were lower than levels in tumours from 6 h. In magnetic resonance T2-weighted imaging of the tumour-bearing nude mice, signal intensity was reduced at the margin of the tumour by injection of A7-Ferumoxides. Mab A7 coupled to Ferumoxides is potentially suitable as a magnetic resonance contrast agent for detecting local recurrence of rectal carcinoma.     

Response of solid tumors to chemotherapy monitored by in vivo 31P nuclear magnetic resonance spectroscopy: a review

In vivo 31P nuclear magnetic resonance (MR) spectroscopy has shown great promise as a tool for cancer research and the clinical management of solid tumors. It is now possible in some cases to integrate MR spectroscopy with routine MR imaging of the cancer patient, so that tissue identified as tumor on an MR image can be examined biochemically and monitored following treatment. Alterations have been observed in the phosphorus MR spectra of patient tumors after treatment, but the causes and consequences of these alterations are poorly understood. Here we review data obtained from experimental animal tumor models treated with chemotherapy in order to gain insight into the biological events reflected in MR spectroscopic changes, and to determine what information the spectra provide about the success or failure of therapeutic interventions. An attempt is made to relate these experimental findings to the cancer clinic and to analyze the contributions of MR spectroscopy to the understanding of tumor biology.     

Changes in radiation sensitization induced by Fluosol-DA as measured by 31P nuclear magnetic resonance spectroscopy

Numerous agents have been studied in attempts to sensitize radioresistant hypoxic tumor cells. We have investigated the effect of Fluosol-DA plus carbogen (95% oxygen and 5% CO2) on the sensitivity of a radioresistant mammary carcinoma in C3H/He mice and also on tumor metabolism by 31P nuclear magnetic resonance spectroscopy. Statistically significant increases in phosphocreatine/Pi were noted for small- (150-350 mm3) and medium- (351-650 mm3) sized tumors treated with Fluosol-DA plus carbogen. Small tumors were shown to undergo significant radiosensitization in the presence of Fluosol-DA plus carbogen and medium-sized tumors showed a lesser degree of radiosensitization. Large tumors (greater than 900 mm3) showed no effect. Fluosol-DA or carbogen alone had no effects on animals with any tumor volume, as monitored by significant changes in radiosensitivity or nuclear magnetic resonance parameters. An approximately linear relationship was found between the decrease in the values for radiation dose which yields 50% tumor control and the increase in phosphocreatine/Pi, with a correlation of r = -0.93. 31P nuclear magnetic resonance spectroscopy may be useful for monitoring changes in radiosensitivity induced by agents which alter tumor oxygenation and subsequent metabolic status.     

Phosphorus metabolism during growth of lymphoma in mouse liver: a comparison of 31P magnetic resonance spectroscopy in vivo and in vitro.

Large phosphomonoester (PME) signals are detected in the phosphorus magnetic resonance spectra (31P MRS) of many neoplastic and rapidly dividing tissues. In addition, alterations in phosphodiester (PDE) signals are sometimes seen. The present study of a murine lymphoma growing in liver showed a positive correlation between the hepatic PME/PDE ratio measured in vivo by 31P MRS at 4.7 T and the degree of lymphomatous infiltration in the liver, quantified by histology. High-resolution 31P MRS of liver extracts at 9.7 T showed that the PME peak consists largely of phosphoethanolamine (PE) and to a lesser extent of phosphocholine (PC). The concentration of both PE and PC increased positively with lymphomatous infiltration of the liver. In vivo, the PDE peak contains signals from phospholipids (mostly phosphatidylethanolamine and phosphatidylcholine) and the phospholipid breakdown products glycerophosphoethanolamine (GPE) and glycerophosphocholine (GPC). Low levels of GPE and GPC were detected in the aqueous extracts of the control and infiltrated livers; their concentrations remained unchanged as the infiltration increased. The total concentration of phospholipids measured by 31P MRS of organic extracts decreased about 3-fold as the infiltration increased to 70%. Thus, our data showed that the increased PME/PDE ratio in vivo is due to both an increase in the PME metabolites and a decrease in the PDE metabolites. We propose that this ratio can be used as a non-invasive measure of the degree of lymphomatous infiltration in vivo.     

Different energy metabolism in two human small cell lung cancer subpopulations examined by 31P magnetic resonance spectroscopy and biochemical analysis in vivo and in vitro.

Two human small cell lung cancer tumor lines, maintained as solid tumor xenografts on nude mice and as in vitro cell cultures, were studied by in vivo 31P magnetic resonance spectroscopy and by biochemical analysis of extracts of solid tumors and cell cultures. The tumor lines CPH SCCL 54A and CPH SCCL 54B are subpopulations from the same tumor. In solid tumors (n = 125), the ATP/Pi ratio was greater in 54A than in 54B. This was due to a higher ATP level in 54A, whereas there was no difference in Pi, ADP, and AMP. A decrease in ATP/Pi during growth was caused by a decline in ATP, whereas Pi remained unchanged. Small amounts of phosphocreatine were found in the xenografts and in tumor extracts, but not in the cell extracts; correspondingly, there was a low creatine kinase activity in solid tumors and no activity in the cell cultures. Thus, the phosphocreatine content of the solid tumors originated from the stroma. A difference in ATP content between 54A and 54B was also found in cell cultures; hence, the metabolic difference is an intrinsic quality of the malignant cells and is not caused by the host system.