sr-4554 and Fibrosarcoma

Photodynamic therapy (PDT) of tumors can create hypoxia when oxygen is depleted by photochemical consumption or the oxygen supply is compromised by microvascular damage. However, oxygen is a requirement for PDT, and hypoxia during illumination can lead to poorer tumor response. As such, sensitive methods of quantifying tumor oxygen and evaluating its distribution may help in the development and optimization of treatment protocols. In this study, the hypoxia marker EF3 [2-(2-nitroimidazol-1[H]-yl)-N-(3,3,3-trifluoropropyl)acetam ide] was used to evaluate the oxygenation of PDT-treated radiation-induced fibrosarcoma tumors. Tumor-bearing mice were administered Photofrin (5 mg/kg) 24 h before PDT illumination at 75 mW/cm2, 135 J/cm2 (30 min). EF3 (52 mg/kg) was injected either within 3 min before PDT illumination, with tumor excision at the conclusion of illumination, or within 3 min after illumination, with tumor excision 30 min later. Control animals received EF3 alone, EF3 plus Photofrin, or EF3 plus illumination. After tumor disaggregation, staining with a fluorochrome-conjugated monoclonal antibody, and flow cytometric analysis, control tumors demonstrated an averaged median fluorescence intensity (+/- SE) of 17.1 +/- 2.8. EF3 binding significantly (P = 0.007) increased during PDT to a median fluorescence intensity of 48.9 +/- 8.3. In the 30 min after PDT, EF3 binding returned to control levels (median, 18.3 +/- 3.3). To evaluate the oxygen concentrations corresponding to these fluorescence intensities, an in vitro standard curve was created based on the in vivo exposure conditions. From this curve, the oxygen tensions of tumors exposed to EF3 under control conditions, during PDT, or after PDT were calculated to be 3.1-5.3, 1.2-2.4, and 3.0-5.2 mm Hg, respectively. Detection of EF3 binding using a monoclonal antibody correlated well with direct detection of binding using a radioactive assay. EF3 binding was linear with drug incubation for times from 1.5 to 60 min. Overall, this work demonstrates that hypoxia during PDT illumination of radiation-induced fibrosarcoma tumors can be detected by the hypoxia marker EF3. Hypoxia during illumination can be labeled separately from that found before or after PDT. Tissue oxygen tensions corresponding to EF3 binding levels can be calculated.

Topics: Animals; Cell Separation; Fibrosarcoma; Flow Cytometry; Mice; Microscopy, Fluorescence; Molecular Probes; Neoplasms, Experimental; Neoplasms, Radiation-Induced; Nitroimidazoles; Oxygen Consumption; Photochemotherapy; Tumor Cells, Cultured

The purpose of this study was to examine the effect of carbogen gas (95% O2-5% CO2) on uptake and metabolism of 5-fluorouracil (5FU) in murine RIF-1 tumors and their growth in vivo. In addition, we have explored the mechanisms by which carbogen can transiently affect the physiology of RIF-1 tumors. After i.p. injection of 1 mmol/kg 5FU into C3H mice, the uptake and metabolism of the drug by s.c. RIF-1 tumors was followed for 2 h noninvasively using 19F-magnetic resonance spectroscopy (MRS). In all animals, irrespective of tumor size, carbogen caused a significant increase in the half-life (t(1/2)) of the elimination of 5FU by the tumor and a significant increase in growth inhibition. In 2-3-g tumors (group II), carbogen also caused increased 5FU uptake and metabolism to the cytotoxic 5-fluoronucleotides, whereas in 0.8-1.5-g tumors (group I), only the t(1/2) was slightly increased. These results suggested that tumor size was an important factor in the effect of carbogen on tumor physiology. Measurements of RIF-1 tumor vascular and necrotic volume showed no significant differences between group I and group II tumors. However, 1H-MR images of RIF-1 tumors showed that carbogen caused a transient decrease in signal intensity, which correlated positively (P = 0.02) with tumor size, suggesting that larger tumors responded to carbogen by transiently increasing O2 uptake from the blood. 19F-MRS was used to measure RIF-1 tumor retention of the fluorinated nitroimidazole SR-4554. These studies also showed a positive correlation (P = 0.001) with tumor size, implying greater hypoxia in larger tumors. We propose that carbogen may transiently open nonfunctional blood vessels in the tumor, allowing increased leakage of 5FU from the plasma into the extracellular space. 5FU transport is known to be pH dependent. Intra- and extracellular tumor pH was measured using 31P- and 19F-MRS, which showed that carbogen caused a significant decrease in the extracellular pH of 0.1 unit in group II tumors and a consequent increase in the negative pH gradient across the tumor plasma membrane, which can cause increased 5FU uptake. The pH gradient was unaffected in group I tumors. We conclude that carbogen breathing can increase tumor uptake of 5FU by two independent mechanisms involving changes in tumor blood flow and pH, which consequently cause increased formation of 5-fluoronucleotides and cytotoxicity. The effect seems more pronounced in hypoxic tumors, implying that carbogen would b

Topics: Animals; Biological Transport; Carbon Dioxide; Fibrosarcoma; Fluorouracil; Hydrogen-Ion Concentration; Hypoxia; Mice; Mice, Inbred C3H; Nitroimidazoles; Nuclear Magnetic Resonance, Biomolecular; Oxygen; Sarcoma, Experimental