Increase in lactate dehydrogenase isoenzyme-1 in plasma in pediatric malignancy.

We investigated 28 cases of pediatric malignancy in which total lactate dehydrogenase (LD, EC 1.1.1.27) activities were increased and isoenzyme LD-1 exceeded LD-2 (flipped pattern). Of these, 11 had a flipped pattern at presentation and 17 showed a flipped pattern during chemotherapy. Those with flipped patterns at presentation were four with germ-cell tumors, one with acute lymphocytic leukemia, and six with nephroblastomas (Wilms tumor). Four of five nephroblastoma homogenates contained predominantly LD-1; one revealed a structurally normal LD-1 with normal kinetics. We conclude that an increase in LD with a flipped pattern is common in nephroblastoma and, in addition, may develop in cancer patients treated with chemotherapy.