Study of serum enzyme leucine aminopeptidase (LAP) isozyme in lung cancer

Serum leucine sminopeptidase (LAP) activity and its isozyme fraction were assayed in 73 primary lung cancer patients with the passage of time before the operation to 3 years after the operation. The LAP activity showed a high value in 25% of the patients before the operation, but did not exhibit a significant change after the operation. By contrast, the isozyme Y fraction showed a high value in 71% of the patients before thee operation and normalization was observed in half of them 1 month after the operation. There was no significant difference in the Y fraction with the size of tumor before the operation, but a significant fall wes observed after curative resection. About half of the patients in whom the Y fraction showed a high value before the operation died within 1 year after the operation. Furthemore, the subsequent prognosis was unfavorable evan in patients in whom the value was normalized after the operation, and a high Y fraction value before the operation seemed to serve as a parameter of unfavorable prognosis.