Glucose Metabolism in RIF-1 Tumors after Reduction in Blood Flow: An zyxw in zyxw Vivo 13C and 31P NMR Study zy Zaver M. Bhujwalla, Dikoma C. Shungu, John C. Chatham, Janna P. Wehrle, Jerry D. Glickson zyxwvu Low pH appears to enhance the effectiveness of therapeutic hyperthermia. 13C and 31P NMR spectroscopy have been em- ployed to examine the possibility that elevating glucose in a solid tumor while simultaneously reducing tumor blood flow would induce a more profound acidosis than either treatment alone. When blood flow in RIF-1 tumors was acutely reduced by administration of hydralazine and additional glucose was delivered locally by intratumoral injection, tumor acidosis (as determined by 31P NMR spxtroscopy) during the period of reduced blood flow was not enhanced, relative to administra- tion of hydralarine alone. Tumor NTPIP, ratios decreased sig- nificantlywithin 20 min of hydralazine administration, whether or not glucose was injected, although NTPIP, ratios were slightly higher in tumors that received extra glucose. Tumor lactate concentrations were not significantly different in glu- cose-supplemented tumors, despite glucose concentratlons that were 4 to 5 times higher. When the added glucose was labeled with 13C, no correlation was detected between the pH in an individual tumor and the intensity of the 3-r3C]-lactate resonance in the same tumor. Key words: RIF-1 tumors; glucose; lactate; pH. INTRODUCTION The clinical availability of noninvasive NMR spectro- scopic methods has heightened interest in identifying NMR-detectable metabolic markers sensitive to tumor blood flow and oxygenation, as these would have wide- ranging applications in the treatment of cancer. For ex- ample, both radiation and photodynamic therapy are de- pendent on tissue oxygen and delivery of chemotherapy is dependent on blood flow. Magnetic resonance spec- troscopy is capable of examining the relationships be- tween tumor pH, blood flow, and energy metabolism zyxwvu in situ. This is essential to understanding tumor patho- physiology and may allow the manipulation of these properties to improve treatment efficacy. The conversion of glucose to lactate is associated with poor blood flow and reduced oxygenation in most nor- zyxwvu MRY 303-309 (1994) From the Division of NMR Research, Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland. Address correspondence to: Zaver M. Bhujwalla, Ph.D., Department of Ra- diology, Room 217 Traylor Building, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21025-21 95. Received February 22,1994; revised May 27,1994; accepted May 31,1994. This work was supported by NIH Grant. No. R01 CA 51935. Present address (D.C.S.): The Neurological Institute - Box 65, College of Physicians and Surgeons of Columbia University, 710 West 168th Street, New York NY 1003. Copyright 0 1994 by Williams & Wilkins All rights of reproduction in any form reserved. 0740-31 94/94 $3.00 ma1 tissues. Many tumor cells, however, metabolize glu- cose to lactate under both anaerobic and aerobic condi- tions. The high rates of glycolysis observed in tumors may, in fact, lead to glucose insufficiency, even in areas with functional perfusion. In an earlier study (I), we observed that direct intratumoral administration of glu- cose to RIF-1 tumors produced a significant zyx increase in tissue pH and in levels of nucleoside triphosphates (NTP) and phosphocreatine (PCr) relative to Pi, even though systemic administration of a similar glucose dose results in acidosis and in a decrease in NTPlP, (2). Carbon-13 NMR spectroscopy indicated that most of the glucose utilized was metabolized to lactate. There was, however, no significant increase in total tumor lactate concentra- tion (determined biochemically]. This indicates that, at least on average, perfusion in RIF-1 tumors of this size is adequate to clear newly generated lactate, consistent with previous evidence that RIF-1 is a relatively well- vascularized tumor with a low hypoxic cell fraction (3). The present study was designed to investigate the me- tabolism of glucose under conditions of more severely reduced blood flow. This was accomplished by adminis- tration of the vasodilator hydralazine (4, 5). The aim of this study was to delineate the relationships among tu- mor blood flow, pH, and energy metabolism under con- ditions of glucose availability but reduced blood flow. Inducing acidosis by loading a tumor with glucose has been suggested as a way to enhance the efficacy of hy- perthermic therapy (6, 7). Injecting glucose intratumor- ally and simultaneously reducing blood flow was a po- tential method for accomplishing this goal. 31P and 13C NMR spectroscopy were used to determine the efficacy of this protocol. METHODS AND MATERIALS Tumor Model RIF-1 tumor cells were propagated according to the pro- tocol recommended by Wentyman zyx et al. (8). Tumors were grown in the flanks of female C,H/HeN mice by subcutaneous inoculation of 5 X lo5 cells. Tumors were examined on days 10 through 12 after inoculation, when tumor volumes ranged from 500 to 900 mm3 (calculated for an elliptical volume-(d6)abc-using caliper mea- surements of three perpendicular axes). NMR Spectroscopy and 31PNMR spectra of RIF-1 tumors were obtained using an 8.5 T Bruker spectrometer interfaced to an As- pect 3000 computer. The home-built probe consisted of a 303