The present invention relates to an expression vector comprising the Guanylate
Binding Protein 1 (GBP-1) gene or parts thereof. The introduction of said vector
comprising said gene or parts thereof in sense or antisense orientation into cells
can be used to induce phenotypical changes of said cells and can, thus, be used
for modulation of cell differentiation. Additionally, the present invention provides,
inter alia, a method for determination of the stage of cellular differention by
using GBP-1 gene expression as a marker.