We further use one tracer for 131I/124I SPECT and PET imaging of PARP1 in subcutaneous and orthotopic mouse models of cancer, thereby illustrating that the expression of PARP1 is highly upregulated and that our labeled tracer accumulates inside the nuclei of glioblastoma cells, where PARP1 is expressed. Here, PARP1 is linked to glioblastoma.