Galactosyltransferase (GalTF),
sialyltransferase (SiaTF),
fucosyltransferase (FucTF),
5'-nucleotidase (5'Nucl), and
ADP-ribosyltransferase (RibTF) were determined in three subcellular fractions of
tumor cells and adjacent control tissue from 20 patients with small primary infiltrating ductal
adenocarcinomas of the breast. Viable, as pure
tumor cell populations as possible were isolated, subfractionated, and their
enzyme levels compared to those in the patients' sera. The activities in
tumor cells of the three
glycosyltransferases were two- to seven-fold higher, whereas 5'-Nucl and RibTF showed reduced activities when compared to adjacent noninvolved tissue. Serum GalTF and SiaTF were slightly elevated in early mammary
carcinoma, whereas FucTF, 5'Nucl, and RibTF were decreased in comparison with a control group. The proposed
tumor origin of circulating
enzymes could not be confirmed. Surprisingly, only for RibTF could a correlation between
tumor and serum activity be established; a weak correlation was found for SiaTF. However, no such relationship could be determined for GalTF, FucTF, or 5'Nucl. In conclusion, the
enzyme profile of the
tumor cell does not, except for RibTF, appear in the serum. Serum
enzyme profiles, therefore, do not permit detection of the early stages of
breast cancer. A high correlation between RibTF activity and cytosol
estrogen and
progesterone receptor levels has been determined in
tumor cells, possibly indicating slower growing, more differentiated types of
breast tumors.