Pyrimidine base degradation in cultured murine C-1300 neuroblastoma cells and in situ tumors.
Dihydropyrimidine dehydrogenase (DPD), the initial, rate-limiting step in pyrimidine degradation, was studied in two cell lines of murine neuroblastoma (MNB-T1 and MNB-T2) that were derived from C-1300 MNB tumor carried in A/J mice. The MNB-T2 (low malignancy) cell line was originally derived from the in situ tumor and carried in tissue culture for more than 100 passages; the MNB-T1 (high malignancy) line consisted of a new sub-culture that was also established from the in situ MNB tumor. DPD activity was determined in cytosolic preparations of MNB utilizing high performance liquid chromatography to separate the radiolabeled substrate ([2-14C]thymine) from [2-14C]dihydrothymine. The apparent affinity of DPD for NADPH in MNB cells (Km approximately 0.08 mM) was identical to that of A/J mouse brain and liver. The DPD activity of the high malignancy (MNB-T1) cell line was 14.3% of that observed in the low malignancy (MNB-T2) line. In situ tumors formed after implantation of high malignancy (MNB-T1) cells into A/J mice had only 25.2% of the DPD activity observed in tumors derived from low malignancy (MNB-T2) cells. When MNB-T2 cells were injected into naive A/J mice, tumors developed in only 68% of animals, the tumor growth rate was slow and a mortality of 20% was observed. In contrast, tumors derived from injected MNB-T1 cells showed a faster growth rate and 100% mortality. Most MNB-T2 derived tumors were not lethal and ultimately resolved while the MNB-T1 derived tumors were invariably lethal. These studies support the concept that the levels of DPD activity in neoplastic cells are inversely related to their malignant expression and also provide a model to study differences between neuroblastoma cell lines derived from the same in situ tumor but which manifest different neoplastic behavior.
Tuchman
M
M
Department of Pediatrics, University of Minnesota, Minneapolis 55455.
O'Dea
R F
RF
Ramnaraine
M L
ML
Mirkin
B L
BL
D000818:Animals; D001921:Brain / Q000201:enzymology; D002395:Catecholamines / Q000378:metabolism; D042943:Dihydrouracil Dehydrogenase (NADP); D008099:Liver / Q000201:enzymology; D051379:Mice; D009249:NADP / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D010088:Oxidoreductases / Q000378:metabolism*; D011743:Pyrimidines / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000378:metabolism*
D002395:Catecholamines; D011743:Pyrimidines; D009249:NADP; D010088:Oxidoreductases; D042943:Dihydrouracil Dehydrogenase (NADP)