The grade of malignance-dependent increase of enzyme activity/expression of gamma-glutamyltranspeptiase (GGT) and dipeptidylpeptidase IV (DPP-IV)-like activity, including CD26 and FAP-1 alpha was found in human gliomas. They seem to participate in maintenance of redox potential, proliferation and tumor microenviroment control expressed primarily at the microvasculature/parenchyma interface.
These activities/molecules correlated with post-operation survival time of a minor subgroup of patients with glioblastoma.