A cytochemical study of lactic dehydrogenase (LDH) isoenzymes in human lung cancer

The cytochemical and electrophoretic LDH isoenzyme patterns in cells from lung cancer tissues were examined with 2.6 M urea treatment and the correlation between the LDH isoenzyme pattern and histopathological entities of lung cancer was also studied. The zymograms of the nonlesional lung tissues indicated the main peak at LDH3, with the M/H ratio 0.74. In tumor tissues, epidermoid carcinoma, adenocarcinoma, and large cell carcinoma showed almost similar patterns of isoenzymes with LDH4 peak. Though small cell carcinomas had a peak at LDH3, they indicated lower activity of %LDH1 and %LDH2 than those in nonlesional lung tissues. Most of the tumor tissues showed a high M/H ratio, more than 1.0. In cytochemical stain for LDH, no inhibitory effect of urea treatment was seen in the nonlesional lung tissues. On the other hand, in the cells obtained from three types of lung cancer, except for small cell carcinoma, urea inhibition was noticed. Cytochemical stainability for LDH-M subunits corresponded well to the results of LDH zymogram. These results suggest that the LDH stain with urea treatment is a useful method for detecting malignancy in cytological specimens.