JBC, Vol. 252, Issue 5, 1807-1813, Mar, 1977
Cancer-associated serum galactosyltransferase activity. Demonstration in an animal model system
D. K. Podolsky, M. M. Weiser, J. C. Westwood and M. Gammon
Two different lines of solid tumors were produced in outbred hamsters by
subcutaneous injection of polyoma transformed BHK cells. Growth of the
tumors correlated with the appearance in serum of an electrophoretically
distinct peak of galactosyltransferase: NeuAc-, Gal-free fetuin acceptor
activity on polyacrylamide gels. This slow moving peak of enzyme activity
(GT-HH) was detected before solid tumors could be grossly observed and the
amount of activity in this peak was also found to be linearly related with
growth of the tumor. GT-IIH was not detectable in control animals and
separated from a faster migrating major area of serum galactosyltransferase
activity (GT-IH) found in sera of both control and tumor-bearing hamsters.
These two activities were shown to maintain their respective mobilities on
re-electrophoresis. Solubilized enzyme derived from excised tumors
demonstrated an electrophoretic mobility on polyacrylamide gels identical
to that for GT-IIH present in serum from tumor-bearing animals. In
contrast, enzyme activity solubilized from livers of both control or
tumor-bearing hamsters showed a mobility similar to that of the faster
moving serum galactosyltransferase enzyme activity, i.e. GT-IH. In
addition, medium derived from nonconfluent BHKpy cells in tissue culture
contained galactosyltransferase activity which co-electrophoresed with the
slower migrating characteristics of galactosyltransferase activities
derived from serum (control and tumor-bearing), solid tumors, liver and
BHKpy cells in tissue culture were compared. All kinetic properties were
similar with the exception that the Km UDP-galactose of GT-IIH (1.0 X
10(-5) M) was half that of GT-IH (2.0 X 10(-5) M).
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