A plasma membrane ectoenzyme in mammalian cells,
5'-nucleotidase, was evaluated as a marker for ovarian
carcinoma. Activities of this
enzyme were determined in homogenates from normal (N = 17) and malignant ovaries (N = 17), as well as in the sera from control women (N = 35),
ovarian cancer patients with active disease (N = 24), and those in clinical remission (N = 9). A significant reduction of the activity of
5'-nucleotidase was observed in
tumor homogenates compared with homogenates from normal ovaries. Levels of this
enzyme in the sera of
ovarian cancer patients were higher than in control women, suggesting the possibility of shedding of this
enzyme from the
tumor cell surface to the systemic circulation of the host. The diagnostic value of serum 5'-necleotidase levels was compared with another
enzyme marker for ovarian
carcinoma, viz. serum
glycoprotein:
galactosyltransferase. The upper limit of normal was set at 2 SD higher than the normal mean. Elevation of serum
5'-nucleotidase was observed in 12/24 (50%) patients with active disease, and 1/9 (11%) patients with clinical remission. In contrast, serum
glycoprotein:
galactosyltransferase was elevated in all the serum samples from patients with active disease and in none of those with clinical remission. There was some correlation between the serum levels of
5'-nucleotidase and those of
glycoprotein:
galactosyltransferase (0.01 less than P less than 0.05). Elevation of
5'-nucleotidase in the serum of these patients was not due to liver
metastasis. Serum
5'-nucleotidase levels seem to correlate with disease status in some ovarian
carcinoma patients, but in general it is inferior to serum
glycoprotein:
galactosyltransferase as a
tumor marker.