Despite reduced tumor growth, we could demonstrate that GM-CSF overexpression and treatment clearly contribute to tumor progression in a xenotransplant model: GM-CSF overexpressing and GM-CSF treated tumors showed a significant increase in tumor cell invasion into the surrounding tissue, concomitant with the recruitment of stromal strands into the tumor tissue and enhanced and persistent tumor angiogenesis. This evidence concerns the gene CSF2 and neoplasm.