By generating a mouse model for testing effects of soluble DLK1 overexpression specifically in the context of glioblastoma, we show that the previously reported association between DLK1 expression and tumor grade in glioma [14,15] may at least in part be caused by DLK1 itself, as soluble DLK1-overexpressing tumors had a higher proliferation rate and significantly decreased mice survival as compared to controls. Here, DLK1 is linked to central nervous system cancer.