Marked increases in DT diaphorase activity in malignantly transformed Syrian hamster fibroblastic cells

NAD(P)H quinone oxidoreductase (DT diaphorase; EC 1.6.99.2) activity in cultured Syrian hamster fibroblastic cells was measured. The cells examined were classified into three categories: (1) four primary embryonic fibroblasts, (2) three non-malignant immortal cells and (3) four malignantly transformed cells. The results showed that cytosolic DT diaphorase activity in malignant cells was markedly higher than the corresponding activity in non-malignant cells (enzyme activity: (3) much greater than (1) greater than or equal to (2)). The enzyme activity was not influenced very much by the particular phase of cell growth. Thus, the increase in DT diaphorase activity seems to be a good marker for malignant transformation, at least in Syrian hamster fibroblastic cells.