Enzyme Activities in Induced and Serially Transplanted Murine Mammary Adenocarcinomas2

The activities of 9 enzymes and the isoenzyme patterns of lactate dehydrogenase (LDH) and hexokinase were measured in mammary adenocarcinomas of BALB/cCrl mice. Adenocarcinomas from 4 sources were used to compare the patterns of enzyme activity between tumors from hyperplastic alveolar nodule outgrowths (HAN) with different frequencies of tumor transformation, between tumors with different growth rates, and between primary and transplanted tumors. No enzyme differences were observed among the primary adenocarcinomas arising from the HAN outgrowths, regardless of the frequency of tumor development. When these neoplasms were transplanted, the slow-growing tumors had markedly increased α-glycerophosphate dehydrogenase activity and slightly increased pyruvate kinase activity; however, other enzyme parameters were the same as in the primary and fast-growing transplanted tumors. Differences were also observed in the patterns of LDH isoenzymes in transplanted tumors, but again the isoenzyme patterns in the primary neoplasms were indistinguishable from one another. Examination of the enzyme activity of two serially transplanted adenocarcinomas with widely different growth rates confirmed that α-glycerophosphate dehydrogenase activity was significantly higher in the slow-growing line. Some biochemical characteristics, particularly the activity of α-glycerophosphate dehydrogenase, correlated inversely with growth rate only in transplanted mammary adenocarcinomas; this implies that some metabolic changes in tumors may be related to transplantation rather than to primary tumor growth.