phosphocreatine and Carcinoma--Small-Cell

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.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Carcinoma, Small Cell; Energy Metabolism; Humans; Lung Neoplasms; Magnetic Resonance Spectroscopy; Mice; Mice, Nude; Neoplasm Transplantation; Phosphocreatine; Phosphorus; Transplantation, Heterologous; Tumor Cells, Cultured

31P nuclear magnetic resonance (NMR) spectra of cells and of cell extract revealed high levels of phosphorylcholine (PC) and phosphocreatine (PCr) in an adriamycin-resistant human small cell lung carcinoma cell line (GLC4/ADR) and the adriamycin-sensitive parental cell line (GLC4). PCr levels in extracts of GLC4/ADR were increased compared to extracts of GLC4. We estimated that 11% of the total intracellular ATP is not bound to Mg2+ in both cell lines. This value corresponded to an intracellular free Mg2+ of 0.30 mM. The effects of different adriamycin concentrations, 0.05, 1 and 30 microM for GLC4 and 1, 30 and 200 microM for GLC4/ADR, on the phosphorus metabolite levels in continuously perfused cells were monitored. Significant differences between GLC4 and GLC4/ADR included: (a) a strong increase in the beta ATP level in the presence of 30 microM adriamycin in GLC4 only, followed by a fast decrease after 5 h of perfusion. (b) a less dramatic increase in the PC level in GLC4/ADR and an unchanged ATP level in the presence of increasing adriamycin concentrations. (c) an increased GPC level in GLC4/ADR in the presence of adriamycin. The changes in PC and GPC levels in the presence of adriamycin suggested that the phospholipid turnover was increased in GLC4/ADR and could be stimulated in the presence of adriamycin. In both cell lines, PCr levels decreased faster than the ATP levels after adriamycin treatment. Thus, biochemical markers for adriamycin resistance can be detected with NMR spectroscopy. However, more studies are necessary to obtain parameters to distinguish drug-sensitive from drug-resistant tumours in patients by NMR spectroscopy.

Topics: Adenosine Triphosphate; Carcinoma, Small Cell; Doxorubicin; Drug Resistance; Energy Metabolism; Humans; Lung Neoplasms; Magnesium; Magnetic Resonance Spectroscopy; Phosphocreatine; Phospholipids; Tumor Cells, Cultured

Human lung cancers are divided into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) based on established criteria. SCLC differs from NSCLC by the expression of biomarkers, including creatine kinase-BB isoenzyme (EC 2.7.3.2). Subtypes of SCLC are referred to as classic and variant, both of which have elevated levels of creatine kinase-BB isoenzyme. We, therefore, applied 31P nuclear magnetic resonance spectroscopy to cell lines of classic SCLC, variant SCLC, and NSCLC human tumors, using continuous perfusion to identify any differences in the detectable levels of intracellular high-energy phosphate compounds. The spectra indicate that only the variant SCLC cells maintain high levels of phosphocreatine. Additionally, the classic SCLC cells express elevated levels of a diphosphodiester. Neither phosphocreatine nor diphosphodiesters are found in the NSCLC cell spectra.

Topics: Adenosine Triphosphate; Carcinoma, Non-Small-Cell Lung; Carcinoma, Small Cell; Cell Line; Creatine Kinase; Humans; Lung Neoplasms; Oncogenes; Phosphates; Phosphocreatine; Sugar Phosphates