Abnormal lactate dehydrogenase isoenzyme in serum and tumor tissue of a patient with neuroblastoma.

Serum and tumor tissue of a patient with neuroblastoma contained an abnormal isoenzyme of lactate dehydrogenase (LDH; EC 1.1.1.27), which, on agarose gel electrophoresis, migrated between LDH-2 and LDH-3 with a mobility the same as that of the extra LDH isoenzyme found in normal human erythrocytes. On surgical removal of the tumor, the high total LDH activity (775 U/L) in the serum of the patient rapidly decreased to normal (70-220 U/L), and the abnormal LDH isoenzyme was no longer detected. The total LDH activity of the abnormal LDH isoenzyme per gram of hemoglobin in the tumor tissue was 26 times that of erythrocytes, suggesting that the abnormal isoenzyme originated mainly from the tumor cells themselves rather than the erythrocytes contained in the tumor tissue. This first report on the appearance of the abnormal LDH isoenzyme in a patient with neuroblastoma suggests that this abnormal LDH isoenzyme may have some significance as a marker enzyme for neurogenic tumors.