Study on the isozymes of lactate dehydrogenase in brain tumors

The changes in isozyme pattern of lactate dehydrogenase (LDH) and calculated ratios of heart muscle type (H)/skeletal muscle type (M) were studied by thin layer acrylamide gel electrophoresis in 65 tissue extracts from 9 human benign astrocytomas, 13 malignant astrocytomas, 3 medulloblastomas, 3 metastatic brain tumors, 19 meningiomas, 9 neurinomas, 5 pituitary adenomas, and 4 other tumors. The isozyme patterns were compared to those obtained from three normal human brain tissues. The average of H/M ratios of normal brain tissues was 1.51±0.03. Benign astrocytomas showed H/M ratios above 1.4 with their average of 2.4±0.7. Malignant astrocytomas showed H/M ratio below 0.9 with their average of 0.58±0.15. There was a decrease in the H/M ratio with increasing the degree of de-differentiation of all gliomas studied. Three medulloblastomas and three metastatic tumors also showed cathodal shifts of LDH isozymes. No characteristic pattern of LDH isozymes was seen in meningiomas, neurinomas, and pituitary adenomas. Analysis of LDH isozyme patterns of the tumors was found to be useful in the estimation of the degree of biological malignancy of gliomas. In four astrocytomas (2 benign and 2 malignant astrocytomas), a supernumerary band of LDH which migrated cathodic to LDH-2 was observed. This extra band was exclusively found in gliomas but not observed in other kinds of tumors. This extra band of LDH might be related with the de-differentiation of glial cells.