Modification of the gluconeogenic/glycolytic balance in isolated perfused liver of myeloproliferative leukemia infected mice: a 13C NMR study.

1. Isolated perfused livers from starved mice inoculated with myeloproliferative leukemia virus exhibited similar rates of consumption of [3-13C]alanine and of synthesis of glutamine and glutamate labeled at the C-2 or C-3 positions as livers from uninfected mice. 2. Leukemic livers also formed glutamine and glutamate labeled at the C-4 position. This is related to their lower content of triglyceride as compared to that of control livers which do not produce these isotopomers. 3. The glucose synthesis rate was much lower in livers from leukemic mice. This is explained by the glycolytic properties of the leukemic infiltrating cells.

31P and 13C NMR studies of isolated perfused hematopoietic cells from leukemic mice.

The myeloproliferative leukemic virus (MPLV) induces within 2-3 weeks a massive infiltration of the adult mouse liver by hematopoietic leukemic cells. Since the metabolism of the infiltrated organ might be correlated with an interaction of two cell populations, it was decided to study the isolated hematopoietic cells separately. The metabolism of these cells embedded in an agarose gel and perfused with labeled substrates was investigated using 31P and 13C NMR. Using [1-13C]glucose as precursor, sequential 13C NMR spectra showed that the hematopoietic cells were able to store glucose as [1-13C]glycogen and to metabolize it through the glycolytic pathway to give [3-13C]lactate as sole end-product. The liver neoglucogenic substrates: [2-13C]pyruvate and [3-13C]alanine are not metabolized by these cells. This suggests that the tricarboxylic acid cycle was not efficient. To investigate further the glycolytic properties of the cells, 10 mM sodium azide was added to the medium containing [1-13C]glucose. When compared to the aerobic conditions, a 40% decrease of nucleotides (0.10 vs 0.17 mumole NTP/10(9) cells), a degradation of [1-13C]glycogen and an increase of ca 35% of the glycolytic rate were observed. The analysis of 13C NMR spectra of the perfusates at the end of the perfusion indicates a total conversion of [1-13C]glucose into [3-13C]lactate and [3-13C]pyruvate under anaerobic conditions. These results permit a better understanding of the metabolism of the perfused leukemic livers which are extensively infiltrated by these hematopoietic cells.

Glucose metabolism in drug-sensitive and drug-resistant human breast cancer cells monitored by magnetic resonance spectroscopy.

Glucose utilization and lactate production have been monitored as a function of time using 13C magnetic resonance spectroscopy and [13C1]-glucose with perfused wild type MCF-7 human breast cancer cells and a drug-resistant (AdrR) cell line derived from them. Compared to wild type cells, AdrR cells exhibited an enhanced (3-fold) rate of glycolysis, indicating an increased demand for ATP production. We have investigated the effects of glucose depletion and azide, an inhibitor of oxidative phosphorylation, on the levels of intracellular phosphates (Pi, ATP) and intracellular pH using 31P magnetic resonance spectroscopy and on the rates of glycolysis. In both cell lines, ATP levels and the rates of glucose utilization and lactate production were invariant in the presence of azide. ATP production, especially in AdrR cells, was highly dependent on active glucose metabolism. The results of these direct measurements confirm that these cells survive by predominantly utilizing glycolysis. Glutamate and myo-inositol were observed in 13C spectra of acid extracts of AdrR but not wild type cells. Both metabolites are potential substrates in drug detoxification. These differences in rates of glycolysis, ATP production, and the production of certain metabolites may reflect metabolic adaptations associated with the development of drug resistance.

Studies on the mechanism of selective retention of porphyrins and metalloporphyrins by cancer cells.

Comparative studies of the toxicity, stability, and retention of the water-soluble porphyrin, tetraphenylporphyrin sulfonate (TPPS), and its complex with Mn(III), have been made with the human breast cancer cell line MCF-7 wild type, and an adriamycin-resistant line derived from it, termed AdrR. Based on growth inhibition, we determined the maximum non-toxic concentration of MnTPPS tolerated by these cells. The integrity of MnTPPS in vitro was investigated by fluorescence microscopy, and we found that there is very little dissociation of MnTPPS within these cells within 4 days. We report novel proton magnetic resonance relaxation measurements of the bulk water of cells in a gel matrix undergoing perfusion. A slightly greater net uptake of MnTPPS in the wild-type cells was observed compared to AdrR; however, there was no significant difference in retention of MnTPPS. These results indicate that over a period of several hours the mechanism of selective retention of these compounds in tumour cells is not due to specific interaction with heme-binding protein, of which there is enhanced expression in the resistant cells. The fact that the net rate of washout of MnTPPS is approximately the same as the net rate of uptake also appears to eliminate compartmentalization or enzymatic modification of MnTPPS within these cells.