The
isozyme patterns and activities of six
enzymes were determined in surgical biopsy samples of lung
tumors and non-neoplastic pulmonary areas. Fetal lungs were also examined. No tissue differences were found in the
isozyme pattern of
hexokinase or
alkaline phosphatase; small differences in
pyruvate kinase isozyme proportions were observed. The
tumors exhibited significant deviations with respect to the
lactate dehydrogenase (LDH) and
malate dehydrogenase (MDH)
isozyme patterns. Despite the diversity of cell types, the proportions of the M-subunit of LDH in each
tumor and that of the mitochondrial
isozyme of MDH in all but one
tumor were higher than in control samples from the same lung. In contrast, the normal fetal lung showed a higher
LDH-H proportion than did adult lung and a mature MDH
isozyme pattern. The
alpha-glycerophosphate dehydrogenase and
adenylate kinase activities of the
tumors were about one-tenth and one-fourth, respectively, of those of nonneoplastic adult lung. These lower activities (evident also in normal fetal lung) were accompanied by 3- to 5-fold increases in the LDH, MDH,
pyruvate kinase, and
hexokinase activities of the
tumors; fetal lungs had lesser increases (2- to 3-fold) for the first 3
enzymes. The common features of
tumors with different cell types and histological grade identified here point to several
enzymes the quantitation or
isozyme analysis of which may be of practical use in distinguishing cancerous from nonneoplastic human lung samples. A combination of different indicators, such as opposite changes in LDH and
alpha-glycerophosphate dehydrogenase activity, coupled with elevated proportions of
LDH-M, may be used to diagnose
neoplasia most reliably.