Elevated Thymic and Serum Galactosyltransferase with Low-Molecular-Weight Acceptor Activity in Murine Leukemia1

Galactosyltransferaseactivity (UDP-galactose:A/-acetyl-o-glucosamine-D-galactosyltransferase) couldbemeasuredinthymus and sera from differentstrainsof mice.Total thymic homogenatesor thymocytepreparationsobtainedfromthymomacarry ing AKR/J miceexhibitedhigherenzymeactivity comparedto nonleukemic ontrolmice.A similardifferencewasalsonotedin Swiss mousethymus which developthymic leukemiaupon a single injection of 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboximide.Galactosidase, whichwas25timeslessactivethangalactosyltransferase,was not responsiblefor this difference. Theseobservationswereextendedto anevaluationof theserum levelof the enzymeas a potentialtumor biomarker.A 3to 4foldincreaseintheactivityof galactosyltransferase wasdetected in serum samplesobtainedfrom both leukemicmice models (AKR/Jand Swiss)comparedto the controls,whereasthe sera from P388 tumor-bearingDBA/2 mice showed a statistically nonsignificant increaseof only20%.Thedataindicatethatserum galactosyltransferase (thatacceptsthelow-molecular-weight ac ceptor,W-acetyl-D-glucosamine) l velsareelevatedin the pres enceof thymicleukemia,andsuggestthepossibilityof shedding of this enzymefrom the tumorcells to the systemiccirculation of the host. The implications,includingthe potentialdiagnostic significanceof the results,arediscussed.