Lactate dehydrogenase isozyme patterns of normal human fibroblasts and their in vitro-transformed counterparts obtained by treatment with CO-60 gamma-rays, SV40 or 4-nitroquinoline 1-oxide.

Lactate dehydrogenase (LDH) isoenzyme patterns of normal human fibroblasts and their in vitro-transformed counterparts were studied. Normal human fibroblasts were derived from embryonic or adult skin or embryonic lung tissues. These cells were transformed into neoplastic cells having unlimited growth potential and abnormal karyotypes by treatment with CO-60 gamma-rays, SV40 or 4-nitroquinoline 1-oxide. No significant difference in LDH isoenzyme patterns was observed in growing or confluent cultures, in the process of in vitro aging of normal human fibroblasts, or in embryonic or adult skin fibroblasts, but there was a considerable difference in isozyme patterns between lung and skin fibroblasts cultured from embryos. All of the transformed fibroblast cell lines derived from lung or skin showed a distinctly increased ratio of B to A subunit (greater than 0.5), whereas normal human fibroblasts did not (less than 0.5). There was no significant difference in total activity of LDH in the various cells used for the present experiments. These findings suggest that the changes of LDH isozyme patterns may be useful as a marker of neoplastic transformation in cultures of normal human fibroblasts.