Elevation of leucine aminopeptidase in disseminated malignant disease

Leucine aminopeptidasea proteolytic enzyme present in most human tissueshas been studied in 90 patients with various types of malignant disease and compared with a group of 25 normal controls and 38 patients with various non-malignant diseases. Levels were measured in serum and 24-hour urine specimens by a colorimetric method. Results showed elevation of LAP values in 24-hour urine specimens in all 16 cases of disseminated GI tract neoplasms19 of 20 cases with disseminated bronchogenic carcinomaall 6 cases of disseminated cancer of the prostateall 9 cases of invasive malignancy of the GU tractand 12 of 15 cases of various hematologic malignancies. (Two patients had CLL; lymphocytes do not produce the enzyme.) Serum levels (vs. urine levels) were not as consistently elevated. Seventeen patients with localized or surgically cured malignancies had normal LAP values. in only 3 of 22 patients with nonmalignant disease was elevation of LAP found (excluding cases with liver or pancreatic diseaseknown to show increased values by previous study of leucine aminopeptidase). It is concluded that urine LAP may be of value in estimating the extent of tumor and success of therapy.